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Sankaran, Nishanth Bharadwaj. "Ridged Nail Designs for Multi-Material Joining of Automotive Structures." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1531702943447706.
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Klein, Mario, Frank Podlesak, Kevin Höfer, et al. "Advanced Joining Technologies for Load and Fibre Adjusted FRP-Metal Hybrid Structures." Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-177669.
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Multi-material-design (MMD) is commonly realized through the combination of thin sheet metal and fibre reinforced plastics (FRP). To maximize the high lightweight potential of the material groups within a multi-material system as good as possible, a material-adapted and particularly fibre adjusted joining technology must be applied. The present paper focuses on two novel joining technologies, the Flow Drill Joining (FDJ) method and Spin-Blind-Riveting (SBR), which were developed for joining heavy-duty metal/composite hybrids. Tests were carried out with material combinations which are significant for lightweight constructions such as aluminium (AA5083) and carbon fibre-reinforced polyamide in sheet thickness of 1.8 mm. The mechanical testing and manufacturing of those multi-material joints was investigated.
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Fedina, Tatiana. "Laser beam-material interaction in Powder Bed Fusion." Licentiate thesis, Luleå tekniska universitet, Produkt- och produktionsutveckling, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-84303.
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The acceptance of additive manufacturing (AM) depends on the quality of final parts and the process repeatability. Recently, many studies have been dedicated to the establishment of the relationship between the process behavior and material performance. Phenomena such as laser-material interaction, melt pool dynamics, ejecta formation and particle movement behavior on a powder bed are of a particular interest for the AM community as these events directly influence the outcome of the process. Another aspect, which hinders the adoption of AM, is the need for cost-efficient powder materials and their sustainable processing and subsequent recycling. The research work presented in this thesis, to a certain degree, covers the above mentioned scientific aspects and focuses on the behavior of gas and water atomized steel powders in laser powder bed fusion (LPBF). Paper I demonstrates a comparative study of dissimilarly-shaped gas and water atomized low alloy steel powders regarding their processability, packing capacities, particle movement behavior and powder performance in LPBF. The impact of chemical composition and morphology of the powders on the process behavior was revealed. Powder spattering and melt pool instabilities were discussed in detail. Paper II explains the role of ejecta in the recycled powder and the changing behavior of the material due to ejecta pick-up. The impact of multiple powder recycling on the degradation of low alloy steel powder in laser powder bed fusion was studied. Oxygen content, particle size and ejecta occurrence gradually increased after each recycling step and were identified as the main contributors to the property alterations observed in the powder during recycling. In addition, a direct correlation between the increase in oxygen with repeated recycling and a more frequent spatter ejection after each recycle was established. Paper III is a successor of Paper I and contains a research on the particle movement and denudation behavior on a powder bed when using near-spherical and non-spherical steel powders. The influence of particle morphology on the dynamics of arbitrary-shaped powder particles was studied by applying an analytical correlation formula to calculate the drag force exerted on powder particles of various shape. Particle entrainment of gas and water atomized powders in front of the laser beam was measured, revealing a significant difference in the powder transfer towards the melt pool.
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Al-Zubaidy, Basem. "Material interactions in a novel Refill Friction Stir Spot Welding approach to joining Al-Al and Al-Mg automotive sheets." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/material-interactions-in-a-novel-refill-friction-stir-spot-welding-approach-to-joining-alal-and-almg-automotive-sheets(ccf8ed1d-e468-4a6c-b90e-ca868d3349e0).html.
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Refill Friction Stir Spot Welding (RFSSW) is a new solid-state joining technology, which is suitable for joining similar and dissimilar overlap sheets connections, particularly in aluminium and magnesium alloys. This welding method is expected to have wide applications in joining of body parts in the automotive industry. In the present study, RFSSW has been used to join 1.0 mm gauge sheets of two material combinations: similar AA6111-T4 automotive aluminium alloy joints and a dissimilar aluminium AA6111-T4 to magnesium AZ31-H24 alloy combinations. The performance of the joints was investigated in terms of the effect of the welding parameters (including tool rotation rate, sleeve plunge depth, and welding time etc.) to improve current understanding and allow optimisation of the process for short welding-cycles when joining similar and dissimilar light alloys. The results of the investigations on similar AA6111 welds showed the ability to use a wide window of process parameters that resulted in joints with a successfully refilled keyhole and flat weld surface, even when using a welding time as short as 0.5 s. The joints in the as-welded condition showed strengths as high as 4.2 kN, when using welding parameters of 1500 rpm, 1.0 mm with a range of welding times from 0.55 to 2.0 s. All joints showed a nugget pull-out failure mode when using a sleeve plunge depth of 0.8 mm or more, as a result of increasing the joint area. The strength of the joints further improved and reached peak loads of 5.15 and 6.43 kN after natural and artificial ageing, respectively, for welds produced using optimised welding parameters of a 2500 rpm tool rotation rate, a 1.5 s welding time and a 1.0 mm plunge. This improvement in strength resulted from the improvement in the local mechanical properties in the HAZ and other regions, which results from a minimal HAZ due to the rapid weld cycle and the re-precipitation of GPZs and clustering on natural ageing, or β on artificial ageing. A modification to the RFSSW process was developed in this project to solve the problems faced when dissimilar welding Mg to Al. This modified process involved adding a final brief pin plunge stage to consolidate refill defects and it was successful in producing nearly defect-free joints with improved mechanical properties, using a wide range of the process parameters. The average peak load of the joints increased with increasing tool rotation rate, to reach a maximum value at 2500 rpm due to eliminating the weld defects by increasing the material plasticity. However, increasing the tool rotation rate further to 2800 rpm led to a decrease in the average peak failure load due to eutectic melting at the weld interface. The optimum welding condition was thus found to be: 2500 rpm, 1.0 s, and 1.0 mm, which gave an average peak failure load of 2.4 kN and average fracture energy of 1.3 kN.mm. These values represent an improvement of about 10 % and 27 %, respectively, compared to welds produced with the conventional RFSSW process, and about 112 % and 78 % of the Mg-Mg similar joints produced using the same welding conditions. A FE model developed in this project was successful in increasing understanding of the behaviour of the RFSSW joints when subjected to lap tensile-shear loading. The stress and strain distribution in the modelled samples showed that the highest concentration occurring in the region of the confluence of the SZ with the two sheets. With increasing extension, these regions of highest stress and strain propagated to the outer surfaces of the two sheets and then annularly around the weld nugget. This annular ring of high strain concentration agreed well with the failure path and results in the full plug pull-out fracture mode shown by the experimentally tested samples. The predicted force-extension curves showed high agreement with the experimental results, especially when including the effect of the hook defect and correction of compliance in the experimental results.
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Mäkinen, Katri. "Optimisation of local material parameters : Optimising local material parameters in ductile cast iron cylinder head casting." Thesis, Jönköping University, JTH, Material och tillverkning, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-54500.
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The constantly tightening emission regulations demand the engines to be moreefficient, to get more power out of smaller engines. Higher engine loads andcomponent temperatures are causing more stresses to engine components. Therefore,a company that produces engines wanted to study if it would be possible to increasethe capabilities of the components by optimising the used material. In this final project work, a cylinder head will be studied. The cylinder heads for theengines are made of ductile cast iron. The limits of that material are near safety limits,and therefore a better material is needed. In this work are some previous studiesanalysed and tried to find how to optimise the used material. The optimised materialshould have better thermal conductivity properties combined with sufficient strengthproperties. Previous studies were analysed to gather knowledge of the elements that affect thematerial parameters. Those studies showed that copper, silicon, pearlite fraction, andthe use of chills are the elements to be optimised. Silicon and pearlite fraction waschosen as optimisation parameters because of their effect on the thermal conductivityand strength properties. Copper was chosen as an optimisation variable due to its effecton the pearlite formation. Chills were used to affect the cooling rate and thereby thepearlite formation. The work was made using MAGMASOFT™ simulation software to simulate cylinderhead casting. The simulated cylinder head was divided into 4 parts for the simulations.For those sections were then set targets for pearlite fraction according to previousstudies. The silicon content was kept constant in the simulation, based on the studiespresented in this work. Copper content was simulated with variations from 0 to 0.7weight-%, and chill heights were simulated from 20 to 60 mm and without chills. After simulating the different variables, the results were analysed. Then the selectedcasting simulation result was mapped to finite element simulation mesh to include thelocal material parameters to finite element simulation. With the finite elementsimulation, the estimated lifetime of the component was simulated. By analysing the casting simulation results, an optimal combination was found. Theoptimal material parameters for a cylinder head casting would be copper 0.5weight-%, silicon 1.9 weight-% and chills thicker than 40 mm on the flame plate. Theoptimised material gives more possibilities to develop engines even further when thecomponent demands are growing.
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Zemui, Simon. "Quenching and tempering hardness response of front axle steel beams : Different material properties during quenching and tempering." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-62747.
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The aim of this thesis was to investigate what the relation is between as-quench hardness and final surface hardness for steel beams is, depending on what tempering temperature is used. Also explain how chemistry, dimension and microstructure effects the final mechanical properties of the front axle beam. For this a review of literature concerning the effects was completed.Hardness measurement on the surface was performed on the ends of the beam (bottom and top). This hardness measurement was performed on 6 different front axle articles of the same material (41CrS4) and 2 different front axle articles of another material (40CrMo4). The relation diagram gives an estimation of what type of tempering temperature is needed to achieve the final hardness that is desired. Because the relation was done with some inconsistences it can’t be said to give a perfect answer. The relation diagrams only work for material 41CrS4 and 40CrMo4. For the core hardness test, 2 articles of 41CrS4 and one article of 40CrMo4 was measured on 5 different position on the cross-section, the beams for the respective articles were taken from quenched state and quenched+tempered. The beam dimensions have a significant effect when it comes to cooling down the part and achieve as close to uniform hardness as possible. Even though the Middle point of the I-section sample is one of the closest cores to the surface, it has a softer core compared with the other cores. While there exists hardness difference after quenching between different points in the core they even out after tempering. When comparing the core hardness with the surface hardness it can be said that the surface hardness is not as hard as the core because of decarburization. The microstructure analysis was done on 2 articles of 41CrS4 and one article of 40CrMo4. Samples from the 3 articles is taken from both the as-quenched state and quenched+tempered state. From the optical microscope it could be seen, that the surface of the beams decarbonizes leading to a higher amount of ferrite at the structure and softer surface. Because of this 15 mm into the material is harder than at-surface. Decarburization of the 41CrS4 steels made it so that what should have been a martensite and bainite dominated surface became a ferrite and bainite dominated.To decide the actual amount of retained austenite in the sample an XRD-analysis was performed. The XRD-analysis is done only for one article type of 41CrS4. From the front axle beam three samples of three different locations (bottom, middle, top) was taken for the analysis. For the theoretical calculation of the retained austenite vs the actual amount it can be said that is a very good representation of the total amount of retained austenite in the product. But the theoretical calculation deviates a bit from the actual amount at the top part of the beam.<br>Syftet med denna avhandling var att undersöka vad relationen är mellan härdat ythårdhet och slut ythårdhet för stålbalkar är, beroende på vilken anlöpnings temperatur som används. Tar också upp hur kemi, dimension och mikrostruktur påverkar de sista mekaniska egenskaperna hos framaxel balken. För detta genomfördes en genomgång av litteraturen om effekterna.Hårdhetsmätning på ytan utfördes på balkens ändar (botten och toppen). Denna hårdhetsmätning utfördes på 6 olika främre axelartiklar av samma material (41CrS4) och 2 olika främre axelartiklar av annat material (40CrMo4). Relationsdiagrammet ger en uppskattning av vilken typ av anlöpningstemperatur som behövs för att uppnå den slutliga hårdheten som önskas. Eftersom förhållandet gjordes med vissa inkonsekvenser kan det inte sägas ge ett perfekt svar. Relationsdiagrammen fungerar endast för material 41CrS4 och 40CrMo4.För kärnhårdhetstestet mättes 2 artiklar av 41CrS4 och en artikel av 40CrMo4 i 5 olika positioner på tvärsnittet, stålen för respektive artiklar togs från härdat tillstånd och härdat + anlöpt. Dimensionerna har en signifikant effekt när det gäller att kyla ner delen och uppnå så nära enhetlig hårdhet som möjligt. Även om mittpunkten i I-sektionsprovet är en av de närmaste kärnorna till ytan, så har det en mjukare kärna jämfört med de andra kärnorna. Det finns hårdhetsskillnad efter härdning mellan de olika punkter men de jämnar ut sig efter anlöpningen. När man jämför kärnhårdheten med ythårdheten kan man säga att ythårdheten inte är så hård på grund av avkolning.Mikrostrukturanalysen gjordes på 2 artiklar av 41CrS4 och en artikel av 40CrMo4. Prover från de 3 artiklarna tas från både härdat tillstånd och härdat + anlöpt tillstånd. Från det optiska mikroskopet kunde man se att stålbalkens yta har blivit utsatt för avkolning vilket leder till en högre mängd ferrit vid strukturen och en mjukare yta. På grund av detta, så är 15 mm in i materialet hårare än vid ytan. Avkolning av 41CrS4 stål gjorde så att det som borde ha varit ett martensit och bainit dominerat yta blev istället ferrit och bainit dominerat.XRD-analysen görs endast för en artikelart av 41CrS4. Från fram axelbalken togs tre prov från tre olika platser (botten, mitten, toppen) för analysen. För att bestämma den verkliga mängden restaustenit i provet utfördes en XRD-analys. För den teoretiska beräkningen av den rest austeniten jämfört med det faktiska beloppet kan man säga det är en mycket bra representation av den totala mängden kvarhållen austenit i produkten. Men den teoretiska beräkningen avviker lite från den faktiska mängden vid stålens övre del.
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Segerstark, Andreas. "Laser Metal Deposition using Alloy 718 Powder : Influence of Process Parameters on Material Characteristics." Doctoral thesis, Högskolan Väst, Avdelningen för svetsteknologi (SV), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-11842.
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Additive manufacturing (AM) is a general name used for manufacturing methods which have the capabilities of producing components directly from 3D computeraided design (CAD) data by adding material layer-by-layer until a final componentis achieved. Included here are powder bed technologies, laminated object manufacturing and deposition technologies. The latter technology is used in this study. Laser Metal Powder Deposition (LMPD) is an AM method which builds components by fusing metallic powder together with a metallic substrate, using a laser as energy source. The powder is supplied to the melt-pool, which is created by the laser, through a powder nozzle which can be lateral or coaxial. Both the powder nozzle and laser are mounted on a guiding system, normally a computer numerical control (CNC) machine or a robot. LMPD has lately gained attentionas a manufacturing method which can add features to semi-finished components or as a repair method. LMPD introduce a low heat input compared to conventional arc welding methods and is therefore well suited in, for instance, repair of sensitive parts where too much heating compromises the integrity of the part. The main part of this study has been focused on correlating the main process parameters to effects found in the material which in this project is the superalloy Alloy 718. It has been found that the most influential process parameters are the laser power, scanning speed, powder feeding rate and powder standoff distance.These process parameters have a significant effect on the temperature history ofthe material which, among others, affects the grain structure, phase transformation, and cracking susceptibility of the material. To further understand the effects found in the material, temperature measurements has been conducted using a temperature measurement method developed and evaluated in this project. This method utilizes a thin stainless steel sheet to shield the thermocouple from the laser light. This has proved to reduce the influence of the laser energy absorbed by the thermocouples.
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Squires, Lile P. "Friction Bit Joining of Dissimilar Combinations of Advanced High-Strength Steel and Aluminum Alloys." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/4104.
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Friction bit joining (FBJ) is a new method that enables lightweight metal to be joined to advanced high-strength steels. Weight reduction through the use of advanced high-strength materials is necessary in the automotive industry, as well as other markets, where weight savings are increasingly emphasized in pursuit of fuel efficiency. The purpose of this research is twofold: (1) to understand the influence that process parameters such as bit design, material type and machine commands have on the consistency and strength of friction bit joints in dissimilar metal alloys; and (2) to pioneer machine and bit configurations that would aid commercial, automated application of the system. Rotary broaching was established as an effective bit production method, pointing towards cold heading and other forming methods in commercial production. Bit hardness equal to the base material was found to be highly critical for strong welds. Bit geometry was found to contribute significantly as well, with weld strength increasing with larger bit shaft diameter. Solid bit heads are also desirable from both a metallurgical and industry standpoint. Cutting features are necessary for flat welds and allow multiple material types to be joined to advanced high-strength steel. Parameters for driving the bit were established and relationships identified. Greater surface area of contact between the bit and the driver was shown to aid in weld consistency. Microstructure changes resulting from the weld process were characterized and showed a transition zone between the bit head and the bit shaft where bit hardness was significantly increased. This zone is frequently the location of fracture modes. Fatigue testing showed the ability of FBJ to resist constant stress cycles, with the joined aluminum failing prior to the FBJ fusion bond in all cases. Corrosion testing established the use of adhesive to be an effective method for reducing galvanic corrosion and also for protecting the weld from oxidation reactions.
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Shirley, Kevin Alexander. "Toward a Production Ready FBJ Process for Joining Dissimilar Combinations of GADP 1180 Steel and AA 7085-T76." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/6694.
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Friction Bit Joining (FBJ) is a new technology that can be used to join dissimilar materials together. This ability makes it a good candidate for creating light weight structures for the automotive industry by combining lightweight materials such as aluminum to stronger materials like advanced high-strength steels. The automotive industry and many other industries have great interest in reducing structure weight to increase fuel efficiency. The purpose of this research is to make FBJ of GADP 1180 to AA 7085-T76 a production ready process by (1) better understanding the effects of process parameters, bit design and tool design on joint strength and reliability especially as they relate to different joint configurations; (2) determining if consecutive FBJ joints on a part will be additive in strength; (3) improving surface finish for better coating adhesion so that joints can be made to withstand extended corrosion testing; and (4) determining the failure modes and fatigue life of joint components at high and low load amplitudes. No universal parameter set for optimizing peak load for T-peel, cross tension, and lap-shear tension configurations were found. Due to the extreme load conditions of T-peel and the smaller margin of safety it is better to optimize for T-peel. However, strength and reliability were still improved across the board. Cutting features and tapered shanks were found to not always be necessary. Removing cutting features from the bit design increased peak weld cycle loads, but a stiffer machine can overcome this. Consecutive FBJ joints on a part are mostly additive in nature. When the weakest joint fails, its load is distributed to the remaining joints and will limit the peak load of the whole part. If all joints are "good" then the peak load will be approximately additive. Most of the stress is localized on the side of the bit opposite of the pulling direction. Failure modes in lap-shear tend to change from weld nugget pullouts in single weld specimens to aluminum material failures in multi-weld specimens. This is because of the added stiffness that additional material and welds provide to resist coupons bending and creating a peeling action. Surface finish was improved by development of a floating carbide cutting system which cut aluminum flash as it was generated around the head of the bit. A new internal drive design provided the ability to drive bits flush with the aluminum top layer if desired with minimal reductions in strength. Flush bits provided benefits in safety, cosmetics, and coating adhesion.
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Hausner, Susann, Martin Franz-Xaver Wagner, and Guntram Wagner. "Microstructural Investigations of Low Temperature Joining of Q&P Steels Using Ag Nanoparticles in Combination with Sn and SnAg as Activating Material." MDPI AG, 2019. https://monarch.qucosa.de/id/qucosa%3A33164.
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Quenching and partitioning (Q&P) steels show a good balance between strength and ductility due to a special heat treatment that allows to adjust a microstructure of martensite with a fraction of stabilized retained austenite. The final heat treatment step is performed at low temperatures. Therefore, joining of Q&P steels is a big challenge. On the one hand, a low joining temperature is necessary in order not to influence the adjusted microstructure; on the other hand, high joint strengths are required. In this study, joining of Q&P steels with Ag nanoparticles is investigated. Due to the nano-effect, high-strength and temperature-resistant joints can be produced at low temperatures with nanoparticles, which meets the contradictory requirements for joining of Q&P steels. In addition to the Ag nanoparticles, activating materials (SnAg and Sn) are used at the interface to achieve an improved bonding to the steel substrate. The results show that the activating materials play an important role in the successful formation of joints. Only with the activating materials, can joints be produced. Due to the low joining temperature (max. 237 °C), the microstructure of the Q&P steel is hardly influenced.
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Prasad, Himani Siva. "Phenomena in material addition to laser generated melt pools." Licentiate thesis, Luleå tekniska universitet, Produkt- och produktionsutveckling, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-73754.
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Jonnalagadda, Krisha Praveen. "Failure mechanisms in APS and SPS thermal barrier coatings during cyclic oxidation and hot corrosion." Licentiate thesis, Linköpings universitet, Konstruktionsmaterial, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-134379.
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Thermal Barrier Coatings (TBCs) are advanced material systems that are being used in the hot sections of gas turbines such as combustor, turbine blades, and vanes. The top ceramic coating in TBCs provides insulation against the hot gases and the intermediate metallic bond coat provides oxidation and corrosion resistance to the underlying turbine components. Durability of thermal barrier coatings is very important for the overall performance of the gas turbine. TBCs can fail in several different ways and there is a combination of more than one failure mechanism in most situations. One of the most widely used TBC is atmospheric plasma sprayed (APS) yttria stabilized zirconia (YSZ). Both the deposition technique and the TBC material have certain limitations. The main aim of this research is to study new TBC materials and/or new deposition techniques and compare with the conventional YSZ and understand their failure mechanisms during cyclic oxidation and hot corrosion. Thermal cyclic oxidation of a newly developed high purity nano YSZ thermal barrier coating has been studied. Cross sectional analysis of exposed as well as completely failed samples showed a mixed-type failure caused by crack propagation parallel to the bond coat/top coat interface. The majority of the damage occurred towards the end of the coating life. A finite element model has been developed to study the probability of crack growth along different paths that leads to the final failure. Hot corrosion mechanism in suspension plasma sprayed two-layer gadolinium zirconate/YSZ, three-layer dense gadolinium zirconate/gadolinium zirconate/YSZ, and a single-layer YSZ has been studied in the presence of sodium sulfate and vanadium pentoxide. The test results showed that gadolinium zirconate coatings were more susceptible to corrosion compared to YSZ coatings despite gadolinium zirconate coatings having lower reactivity with the corrosive salts. Thermal cycling behavior of a high chromium bond coat has been studied. Cross-sectional analysis showed formation of sandwich type microstructure with chromium rich oxide and alumina as the top and the bottom layers. Inter-diffusion of minor elements between different MCrAlY coatings – substrate systems has been studied using, diffusion simulation software, DICTRA. The simulation results showed that the diffusion of minor elements in the coatings is dependent on the rate of β phase depletion in the beginning. After the depletion of β phase there was no clear dependence of the coating composition on the diffusion of minor elements.
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BANGASH, MUHAMMAD KASHIF. "Joining of Dissimilar Materials." Doctoral thesis, Politecnico di Torino, 2018. http://hdl.handle.net/11583/2711296.
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Material manufacturers and engineering structure designers are currently focusing new ways to exploit the benefits of light-weight, hybrid materials with improved properties at a low cost. The ability to join dissimilar materials is enabling the design engineers to develop light-weight and efficient automobiles, aircraft and space vehicles.
The objective of this PhD research study was to produce alternative and efficient joining solutions for automotive and aerospace applications. The joining of dissimilar material was experimented to obtain light-weight Fibre Reinforced Polymer (FRP) sandwich composites, Al-foam sandwich (AFS) composites, hybrid dynamic FRP epoxy/polyurethane composites and the joining of Ti6Al4V alloy with and without surface modification to Ceramic Matrix Composite (CMC) and itself.
The joining of Al-foam and Al-honeycomb to FRP skins was performed. The experimental results show that higher flexural properties can be achieved by replacing Al-honeycomb with low-cost Al-foam as a core material in the sandwich structures. Compared to FRP-honeycomb sandwich panels, FRP-Al foam sandwich panels display ~25 % and ~65 % higher flexural strength in a long and short span three-point bending tests respectively.
AFS composites with complete metallic character, to withstand high-temperature application conditions, were produced by soldering/brazing techniques using Zn-based and Al-based joining alloys. A post-brazing thermal treatment was designed to recover the mechanical properties of AFS composites, lost during the soldering/brazing process. The microstructural analysis of the Al-skin/Al-foam interface revealed that the diffusion of joining materials into the joining substrates (Al-sheet and Al-foam) was achieved. Around 80% higher bending load before failure was observed when the AFS specimens produced with Zn-based joining alloys were subjected to flexural load compared to those produced with Al-based joining alloys.
Hybrid dynamic Carbon Fibre Reinforced Polymer (CFRP) composites with enhanced impact properties were produced by exploiting the reversible cross-linking functionalities of dynamic epoxy and dynamic PU resin systems. By joining dynamic CFRP-epoxy and dynamic CFR-PU laminates, hybrid dynamic composite in three different configurations and a non-hybrid composite were obtained. The four dynamic composites were characterised for structural, thermal, flexural and impact properties. The damage initiation upon impact was observed at around 95% higher energy level in the hybrid configuration (CFRP-4), compared to the non-hybrid configuration. The hybrid configuration CFRP-3 responded with around 55% higher perforation threshold energy compared the non-hybrid configuration.
Preliminary work on Adhesive joining of the Ti6Al4V alloy to itself was performed to analyse the effect micro-machining on adhesion and the effect of shape/design of micro-slots on an adhesive joint strength. Three types of micro-slots: V, semi-circle and U-shaped micro-slots were produced on Ti6Al4V sheet surface by using an in-house developed Micro-Electro-Discharge Machining (Micro-EDM) setup. Ti6Al4V alloy specimens with and without micro-machined surfaces were bonded together using a commercial epoxy adhesive. The Single Lap Offset (SLO) shear test results revealed that the micro-slot oriented perpendicular to the applied load displayed ~23 % higher joining strength compared to when the micro-slots were oriented parallel to the applied load. U-shaped micro-slots configuration displayed ~30 % improvement in the joint shear strength compared to the specimens with un-modified surfaces. The fractured surfaces analysis revealed mix (adhesive-cohesive) with cohesive dominated failure in bonded specimens with micro-machined surfaces compared to the as-received where pure adhesive failure was observed.
The joining of CMCs (C/SiC and SiC/SiC) to Ti6Al4V alloy was experimented using active brazing alloy (Cusil-ABA) and Zr-based brazing alloy (TiB590) in a pressure-less argon atmosphere. The CMC-Ti6Al4V joint strength was further improved by modifying the surface of Ti6Al4V alloy using an in-house built Micro-EDM setup. Around 40% higher joining strength was recorded when the Zr-based brazing alloy was used as a joining material compared to the conventional active brazing alloy, Cusil-ABA. Improvement in the joining strength was noticed when the Ti6Al4V surface was modified prior to joining.
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Bergstedt, Edwin. "A Study in How Welding Parameters Affect the Porosity in Laser Welded High Pressure Die Cast AM50 Magnesium Alloy." Thesis, KTH, Materialvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-291119.
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There are a need for reducing the weight of vehicles, one solution is to implement cast lightweight materials such as the high pressure die cast AM50 magnesium alloy. The weldability of this cast alloy is poor and to implement the use of the alloy commercially a welding process is needed that limits the porosity of the weld. The aim of this thesis is to study the effect of the welding parameters on the porosity in the weld, for three laser welding methods. The welding methods examined are single spot and twin spot laser using either a beam splitter or separate optics. The microstructure of the base material are also examined in order to evaluate relations between the components of the microstructure and the porosity in the weld. It was concluded that the hydrogen in the base material was the main reason for the observed porosity in the weld and that the material contains high pressure gas. The welding parameters did not influence the porosity for the single beam laser process, however, for the dual beam processes the welding parameters could affect the amount of pores. It was found that a double weld reduced the amount of pores and that the size and distribution of the secondary phase particles would benefit from the treatment. The cleaning of the samples prior to welding increased the porosity, however, non-cleaned samples contained more oxide inclusions. The results indicate that a twin beam process could reduce the porosity in the weld of the AM50 alloy.<br>Det finns ett behov av att reducera vikten på fordon, en lösning är att implementera gjutna lätta material såsom formsprutad AM50-magnesiumlegering. Svetsbarheten hos denna gjutna legering är dålig och för att kommersiellt kunna använda legeringen krävs en svetsprocess som begränsar svetsens porositet. Syftet med detta examensarbete är att studera svetsparametrarnas effekt på svetsens porositet för tre lasersvetsmetoder. De svetsmetoder som undersöks är enkelpunkts och dubbelpunktslaser där antingen en stråldelare eller separat optik använts. Basmaterialets mikrostruktur undersöks också för att utvärdera sambandet mellan mikrostrukturen och porositeten i svetsen. Man drog slutsatsen att väte i basmaterialet var huvudorsaken till den observerade porositeten i svetsen och att materialet innehåller gas under högt tryck. De undersökta svetsparametrarna påverkade inte porositeten för processen med en laserstråle, men för dubbelstråleprocesserna kan svetsparametrarna påverka mängden porer. Det visade sig att en svets utförd med två strålar minskade mängden porer och att storleken och fördelningen av sekundärfaspartiklarna gynnas av behandlingen. Prover som rengjordes före svetsning hade ökad porositet, men icke-rengjorda prover innehöll mer oxidinneslutningar. Resultaten indikerar att en dubbelstråleprocess kan minska porositeten då AM50-legeringen lasersvetsas.
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Höjer, Fredrik. "Putsa infärgat faner : Val av material, snittyta och metod." Thesis, Linköpings universitet, Malmstens Linköpings universitet, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-162975.
Full textAbstract:
I mitt examensarbete undersöker jag vilken putsmetod som lämpar sig bäst för putsning av infärgat faner utan att infärgat damm fastnar på oönskade områden. Testområdet har varit avgränsat till att undersöka detta problem tillsammans med andra, icke infärgade faner. Frågan är om det finns en metod som på ett effektivt och ergonomiskt sätt garanterar ett bra resultat? Mina tester utgår från om val av material, fiberriktning och snittyta har betydelse för hur det infärgade dammet fastnar på ytan. Min förhoppning är att hantverkare och formgivare ska ta hjälp av denna undersökning för att lättare kunna göra medvetna val där infärgade faner kombineras med andra träslag. Genom intervjuer med andra hantverkare, om deras erfarenheter har ett problemområde kartlagts utifrån vad som är mest relevant för undersökningen. Även litterära studier har gjorts för att bättre förstå träts anatomiska egenskaper. För att uppnå optimala förutsättningar för att infärgat damm inte ska fasta på oönskade områden visar testerna, genom att kombinera infärgat faner med ett bandporigt träslag som har en radiell snittyta tillsammans med en fiberriktning som ligger i samma riktning som putsriktningen, med en putsmetod där direkt sug över putsytan verkar samtidigt som putsningen ger bäst förutsättning för att infärgat damm inte fastnar på oönskade områden.
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Lätzer, Michael. "Füge- und Übertragungsverhalten torsionsbelasteter Stahl-Aluminium-Rändelpressverbindungen." Doctoral thesis, Universitätsbibliothek Chemnitz, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-200348.
Full textAbstract:
Die vorliegende Dissertation beschäftigt sich mit analytischen, numerischen und experimentellen Grundlagenuntersuchungen zum Füge- und zum Übertragungsverhalten einer reibformschlüssigen Stahl-Aluminium-Rändelpressverbindung. Die Besonderheit dieser Verbindung besteht darin, dass eine mit einer Rändelung und Übermaß versehene harte Stahlwelle in eine weiche Aluminiumnabe mit kreisrunder Bohrung längseingepresst wird. Die maßgebende Größe für den Fügevorgang ist der Fasenwinkel der Welle φ. Der Nabenwerkstoff wird hierbei in Abhängigkeit des Fasenwinkels der Welle φ umgeformt beziehungsweise herausgeschnitten. Mit Hilfe der relativen Festigkeit R F , welche das Verhältnis von maximaler Lösekraft F l, max zu maximaler Fügekraft F f, max repräsentiert, wurde ein Gütekennwert zur gezielten Auswahl von Stahl-Aluminium-Rändelpressverbindungen hinsichtlich der axialen Übertragungsfähigkeit abgeleitet. Die Charakterisierung der experimentell ermittelten Torsionsmoment - Verdrehwinkel - Kurven ergab zur Auslegung die Bereiche Auslegungs- und Versagenskriterium. Das maximal übertragbare Torsionsmoment wird beim sogenannten Versagenskriterium τ S durch das Abscheren der Rändel in der Nabe erreicht. In Analogie zum Füge- und zum Löseverhalten zeigt sich der positive Einfluss des Fasenwinkels φ auf das übertragbare Torsionsmoment. So können formend gefügte Stahl-Aluminium- Rändelpressverbindungen ein um bis zu ca. 40% größeres statisches Torsionsmoment als vergleichbare schneidend gefügte Rändelpressverbindungen übertragen. Das mechanisch-physikalische Berechnungsmodell zur Berechnung des statisch übertragbarenTorsionsmomentes basiert auf der Kerbzahnverbindung. Damit kann das Torsionsmoment am Auslegungskriterium T pF sowie das maximal übertragbare Torsionsmoment bei Abscherung Tτ S ermittelt werden. Die Berücksichtigung des formenden beziehungsweise schneidenden Fügevorgangs wird in Abhängigkeit des Fasenwinkels φ mit Hilfe des sogenannten winkelbasierten Umformgrades ε plRPV beschrieben<br>The present thesis provides analytical, numerical and experimental fundamental studies for the joining behaviour and the transmission behaviour of a friction and form closure steel-aluminum knurled interference fit. The special feature of this connection is a knurled and oversize hard steel shaft, longitudinally pressed in a soft aluminum hub with a circular bore. The most important parameter for the joining process is the shaft chamfer angle φ. Due to the shaft chamfer angle φ the material of the hub will be formed or cutted during the joining process. By using the relative strength, the quotient of push out force and joining force who describes the joint strength, a first quality parameter for a precise selection of steel-aluminum knurled interference fit has been derived. The description of the experimentally determined torque - twisting angle – curves has shown areas of design criterion and mechanical breakdown. The maximum transmittable torque is achieved by reaching the shearing stress of the knurls in the hub - mechanical breakdown τ S. Similar to the joining and the push out behaviour, the positive influence of the shaft chamfer angle φ is also shown at the transmittable torque. Furthermore, knurled interference fits joined by forming can transmit higher torques of about 40% than interference fits joined by cutting due to the material hardening. The mechanical-physical model for calculating the static transmittable torque is based on the serration connection. Thus, the torque at the design criterion and the maximum transmittable torque at the mechanical breakdown can be found. The consideration of the forming or cutting joining process is described as a function of the shaft chamfer angle φ using the so-called angle-based plastic strain ε plRPV
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Khalil, Chady. "Développement du procédé de soudage par impulsion magnétique pour soudage hétérogène bimétallique et pour assemblage hybride métal / composite." Thesis, Ecole centrale de Nantes, 2018. http://www.theses.fr/2018ECDN0031.
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La réduction des émissions CO2 et l'amélioration de la performance restent toujours les grands objectifs de l'industrie automobile. Pour atteindre ces objectif, les équipementiers automobiles cherchent toujours à alléger les structures à travers l'emploie des matériaux hétérogènes qui a évolué au cours des dernières décennies où nous trouvons aujourd'hui à la fois des aciers doux, des aciers à très hautes résistances, des alliages légers tels que les alliages d'aluminium et de magnésium ainsi que des composites à fibre de verre ou de carbone. Cette tendance pose aujourd'hui plusieurs défis concernant à la fois l'assemblage bimétallique et l'assemblage hybride métal/composite. Les difficultés de réaliser ce type d’assemblage est lié surtout à la différence des propriétés mécaniques, thermiques et chimiques des divers matéiaux. Ces différences limitent l’utilisation des techniques d’assemblage traditionnelles, c’est-à-dire l’assemblage mécanique, le soudage par fusion et le collage, et nécessitent ainsi le développement de nouvelles solutions d’assemblage. Dans ce contexte, cette étude vise à répondre aux défis des soudages hétérogènes ainsi qu' à développer deux nouvelles solutions originales d'assemblage hybride métal/composite en utilisant le procédé de soudage par impulsion magnétique<br>Reducing CO2 emissions and improving performance are still the main goals of the automotive industry. To achieve these objectives, automotive suppliers are still seeking to lighten the structures through the use of heterogeneous materials that have evolved in recent decades. We find today in one vehicle mild steels, very high strength steels, light alloys such as aluminum and magnesium alloys as well as fiber reinforces polymeric composites. The presence of dissimilar materials arises several challenges regarding both the heteregeneous metal assemblies and hybrid metal / composites assemblies. The differences in the mechanical, thermal and chemical properties of the various materials limit the use of traditional assembly techniques, i.e. mechanical assembly, fusion welding and adhesive bonding, and thus the development of new assembly solutions is required. In this context, this study aims to meet the challenges of heterogeneous metal welding and aims to develop two new original hybrid metal / composite assembly solutions using the magnetic pulse welding process
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Aldén, Rickard. "Metallurgical investigation in weldability of Aluminium Silicon coated boron steel with different coating thickness." Thesis, KTH, Materialvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-171209.
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Hot-pressed aluminium and silicon coated boron steel is used in the car industry where high tensile strength is of great importance, such as in the safety cage of a car where deformation has to be kept to a minimum in case of a collision. After hot-pressing the AlSi-boron steel shows excellent properties with high tensile strength, minimal spring back and also shows good protection against corrosion. A thickness of the AlSi coating of 150 [g/m2] for AlSi coated boron steel is typically used by the car industry today. However the coating thickness would be desirable to be minimized to 80 [g/m2]. Welding of this boron steel with 80 [g/m2]have shown difficulties; and it’s not clear why this occurs. In this report the metallurgical properties of the different coating layers will be investigated, simulations with Thermocalc module Dictra will be used, SEM/EDS will be used to characterize phases in coating layers and correlate to weldability. Resistance spot welding tests will also be performed where the welding parameters of pre-pulse, pulse time, time in between pulses and current will be varied to achieve desirable weld plug diameter without expulsion. Hardness testing in form of micro Vickers will executed. The Materials used will be USIBOR® 1500, AS80 with four different annealing times and one sample of AS150.
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Lindell, David. "Process Mapping for Laser Metal Deposition of Wire using Thermal Simulations : A prediction of material transfer stability." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-85474.
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Additive manufacturing (AM) is a quickly rising method of manufacturing due to its ability to increase design freedom. This allows the manufacturing of components not possible by traditional subtractive manufacturing. AM can greatly reduce lead time and material waste, therefore decreasing the cost and environmental impact. The adoption of AM in the aerospace industry requires strict control and predictability of the material deposition to ensure safe flights. The method of AM for this thesis is Laser Metal Deposition with wire (LMD-w). Using wire as a feedstock introduces a potential problem, the material transfer from the wire to the substrate. This requires all process parameters to be in balance to produce a stable deposition. The first sign of unbalanced process parameters are the material transfer stabilities; stubbing and dripping. Stubbing occurs when the energy to melt the wire is too low and the wire melts slower than required. Dripping occurs when too much energy is applied and the wire melts earlier than required. These two reduce the predictability and stability that is required for robust manufacturing. Therefore, the use of thermal simulations to predict the material transfer stability for LMD-w using Waspaloy as the deposition material has been studied. It has been shown that it is possible to predict the material transfer stability using thermal simulations and criterions based on preexisting experimental data. The criterion for stubbing checks if the completed simulation result produces a wire that ends below the melt pool. For dripping two criterions shows good results, the dilution ratio is a good predictor if the tool elevation remains constant. If there is a change in tool elevation the dimensionless slenderness number is a better predictor. Using these predictive criterions it is possible to qualitatively map the process window and better understand the influence of tool elevation and the cross-section of the deposited material.<br>Additiv tillverkning (AT) är en kraftigt växande tillverkningsmetod på grund av sin flexibilitet kring design och möjligheten att skapa komponenter som inte är tillverkningsbara med traditionell avverkande bearbetning. AT kan kraftigt minska tid- och materialåtgång och på så sett minskas kostnader och miljöpåverkan. Införandet av AT i flyg- och rymdindustrin kräver strikt kontroll och förutsägbarhet av processen för att försäkra sig om säkra flygningar. Lasermetalldeponering av tråd är den AT metod som hanteras i denna uppsats. Användandet av tråd som tillsatsmaterial skapar ett potentiellt problem, materialöverföringen från tråden till substratet. Detta kräver att alla processparametrar är i balans för att få en jämn materialöverföring. Är processen inte balanserad syns detta genom materialöverföringsstabiliteterna stubbning och droppning. Stubbning uppkommer då energin som tillförs på tråden är för låg och droppning uppkommer då energin som tillförs är för hög jämfört med vad som krävs för en stabil process. Dessa två fenomen minskar möjligheterna för en kontrollerbar och stabil tillverkning. På grund av detta har användandet utav termiska simuleringar för att prediktera materialöverföringsstabiliteten för lasermetalldeponering av tråd med Waspaloy som deponeringsmaterial undersökts. Det har visat sig vara möjligt att prediktera materialöverföringsstabiliteten med användning av termiska simuleringar och kriterier baserat på tidigare experimentell data. Kriteriet för stubbning kontrolleras om en slutförd simulering resulterar i en tråd som når under smältan. För droppning finns två fungerande kriterier, förhållandet mellan svetshöjd och penetrationsdjup om verktygshöjden är konstant, sker förändringar i verktygshöjden är det dimensionslös ”slenderness” talet ett bättre kriterium. Genom att använda dessa kriterier är det möjligt att kvalitativt kartlägga processfönstret och skapa en bättre förståelse för förhållandet mellan verktygshöjden och den deponerade tvärsnittsarean.
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Kanesund, Jan-erik. "Influence of deformation and environmental degradation of Inconel 792." Licentiate thesis, Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-133824.
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Industrial gas turbines are often used as a mechanical drive for pumps and compressors or in power generation as an electric power supply. The gas turbine has for many years been a popular engine due to its flexibility with respect to different types of fuel and due to a design, that enables a high power-to-weight ratio. A simplified description of a gas turbine is that the engine consists of a cold and hot section. The turbo compressor section belongs to cold section and the combustion chamber together with the turbine section belongs to the hot section. In the hot section of a gas turbine, the condition is extremely severe because of an aggressive environment characterized by high temperatures, increased temperature gradients, high pressure and centrifugal forces resulting in large stresses on individual components together with an oxidizing and corroding atmosphere. Materials used in the high temperature section (hot gas path) of a modern gas turbine are different types of superalloys, as single crystal, directionally solidified or polycrystalline alloys, depending on temperature and load conditions. In the first turbine stage, temperature is very high due to exposure to the combustion gas. To handle the problem with creep, single crystal superalloys are often used in this section. In the second row of turbine blades, the temperature of the gas is lower and polycrystalline superalloys are typically used. IN-792 is a cast polycrystalline superalloy with high strength, good resistance to hot corrosion and a cheaper option than single crystals. In the hot section of gas turbine, IN-792 is a suitable material for components such as turbine blades and vans where a complex load condition, high temperature and severe environment prevails. Due to startup and shutdown of the gas turbine engine during service, the components in the hot section are exposed to cyclic load and temperature. This will generate mechanical and thermal fatigue damage in gas turbine components. Steady state temperature gradient arises by the cooling system acting at cold spots during service to introduce tensile stress, which indirectly gives rise to creep damage in the component. This work includes tree studies of deformation and damage mechanisms of superalloy IN-792. The first study is made on test bars exposed to thermomechanical fatigue in laboratory environment, the second and the third study is made on turbine blades used during service. In the second study, the machines are placed off-shore and exposed to marine environment. In the third study the machine is landbased and exposed to an industrial environment. In the second study, the deformation and damage mechanisms are compared between the turbine blades used during service and the test bars exposed to thermomechanical fatigue testing in the first study.
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Wielage, B. "Schriftenreihe Werkstoffe und werkstofftechnische Anwendungen." Technische Universität Chemnitz, 2013. https://monarch.qucosa.de/id/qucosa%3A19884.
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Die Schriftenreihe „Werkstoffe und werkstofftechnische Anwendungen“ behandelt Themengebiete der Werkstoffwissenschaft und -technik, der Oberflächentechnik sowie deren industriellen Anwendungen. Es werden vorrangig aktuelle Forschungsergebnisse der Professuren Verbundwerkstoffe und Oberflächentechnik/Funktionswerkstoffe des Instituts für Werkstoffwissenschaft und Werkstofftechnik der TU Chemnitz vorgestellt. Weiterhin sind in der Schriftenreihe die Tagungsbände des jährlich am Institut stattfindenden „Werkstofftechnischen Kolloquium“ enthalten. Die einzelnen Bände beschäftigen sich mit den Forschungsgebieten Galvanische Metallabscheidung, Anodisieren, Thermisches und Kaltgas-Spritzen, Löten, Verbundwerkstoffe, Werkstoffverbunde, Wärmebehandlung, CVD-Beschichtungen/PVD-Beschichtungen, Simulation in der Beschichtungstechnik, Organisches Beschichten (Pulverbeschichten, Lackieren, Sol-Gel-Verfahren), Elektrochemisches Strukturieren, Thermomechanische Behandlung und Mechanische Werkstoffeigenschaften.<br>The book series „Werkstoffe und werkstofftechnische Anwendungen“ outlines up-to-date topics of material science and engineering, surface engineering as well as resulting industrial applications. Mainly, recent research results of the departments Composite Materials and Surface Engineering/Functional Materials of the Institute of Material Science and Engineering of Chemnitz University of Technology are presented. In addition, the book series includes the proceedings of the annual in-house conference “Werkstofftechnisches Kolloquium”. The separate volumes concentrate on the following fields of scientific research: Galvanised Coating, Anodising, Thermal and Cold Spraying, Soldering and Brazing, Composite Materials, Composite Structures, Thermal and Thermomechanical Treatment, CVD and PVD Coating, Simulation of Coating Processes, Organic coating (Powder Coating, Varnishing, Sol-Gel Processes), Electrochemical Structuring and Mechanical Material Properties.
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Yoak, Beth A. "Rapid Nailing Method for Joining Materials." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1397604720.
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Lätzer, Michael. "Füge- und Übertragungsverhalten torsionsbelasteter Stahl-Aluminium-Rändelpressverbindungen." Doctoral thesis, Universitätsverlag der Technischen Universität Chemnitz, 2015. https://monarch.qucosa.de/id/qucosa%3A20428.
Full textAbstract:
Die vorliegende Dissertation beschäftigt sich mit analytischen, numerischen und experimentellen Grundlagenuntersuchungen zum Füge- und zum Übertragungsverhalten einer reibformschlüssigen Stahl-Aluminium-Rändelpressverbindung. Die Besonderheit dieser Verbindung besteht darin, dass eine mit einer Rändelung und Übermaß versehene harte Stahlwelle in eine weiche Aluminiumnabe mit kreisrunder Bohrung längseingepresst wird. Die maßgebende Größe für den Fügevorgang ist der Fasenwinkel der Welle φ. Der Nabenwerkstoff wird hierbei in Abhängigkeit des Fasenwinkels der Welle φ umgeformt beziehungsweise herausgeschnitten. Mit Hilfe der relativen Festigkeit R F , welche das Verhältnis von maximaler Lösekraft F l, max zu maximaler Fügekraft F f, max repräsentiert, wurde ein Gütekennwert zur gezielten Auswahl von Stahl-Aluminium-Rändelpressverbindungen hinsichtlich der axialen Übertragungsfähigkeit abgeleitet.
Die Charakterisierung der experimentell ermittelten Torsionsmoment - Verdrehwinkel - Kurven ergab zur Auslegung die Bereiche Auslegungs- und Versagenskriterium. Das maximal übertragbare Torsionsmoment wird beim sogenannten Versagenskriterium τ S durch das Abscheren der Rändel in der Nabe erreicht. In Analogie zum Füge- und zum Löseverhalten zeigt sich der positive Einfluss des Fasenwinkels φ auf das übertragbare Torsionsmoment. So können formend gefügte Stahl-Aluminium- Rändelpressverbindungen ein um bis zu ca. 40% größeres statisches Torsionsmoment als vergleichbare schneidend gefügte Rändelpressverbindungen übertragen.
Das mechanisch-physikalische Berechnungsmodell zur Berechnung des statisch übertragbarenTorsionsmomentes basiert auf der Kerbzahnverbindung. Damit kann das Torsionsmoment am Auslegungskriterium T pF sowie das maximal übertragbare Torsionsmoment bei Abscherung Tτ S ermittelt werden. Die Berücksichtigung des formenden beziehungsweise schneidenden Fügevorgangs wird in Abhängigkeit des Fasenwinkels φ mit Hilfe des sogenannten winkelbasierten Umformgrades ε plRPV beschrieben.<br>The present thesis provides analytical, numerical and experimental fundamental studies for the joining behaviour and the transmission behaviour of a friction and form closure steel-aluminum knurled interference fit. The special feature of this connection is a knurled and oversize hard steel shaft, longitudinally pressed in a soft aluminum hub with a circular bore. The most important parameter for the joining process is the shaft chamfer angle φ. Due to the shaft chamfer angle φ the material of the hub will be formed or cutted during the joining process. By using the relative strength, the quotient of push out force and joining force who describes the joint strength, a first quality parameter for a precise selection of steel-aluminum knurled interference fit has been derived.
The description of the experimentally determined torque - twisting angle – curves has shown areas of design criterion and mechanical breakdown. The maximum transmittable torque is achieved by reaching the shearing stress of the knurls in the hub - mechanical breakdown τ S. Similar to the joining and the push out behaviour, the positive influence of the shaft chamfer angle φ is also shown at the transmittable torque. Furthermore, knurled interference fits joined by forming can transmit higher torques of about 40% than interference fits joined by cutting due to the material hardening. The mechanical-physical model for calculating the static transmittable torque is based on the serration connection. Thus, the torque at the design criterion and the maximum transmittable torque at the mechanical breakdown can be found. The consideration of the forming or cutting joining process is described as a function of the shaft chamfer angle φ using the so-called angle-based plastic strain ε plRPV.
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Seidlitz, Holger, Lars Ulke-Winter, Colin Gerstenberger, and Lothar Kroll. "Dimensioning of Punctiform Metal-Composite Joints: A Section-Force Related Failure Criterion." Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-152889.
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Reliable line production processes and simulation tools play a central role for the structural integration of thermoplastic composites in advanced lightweight constructions. Provided that material- adapted joining technologies are available, they can be applied in heavy-duty multi-material designs (MMD). A load-adapted approach was implemented into the new fully automatic and faulttolerant thermo mechanical flow drill joining (FDJ) concept. With this method it is possible to manufacture reproducible high strength FRP/metal-joints within short cycle times and without use of extra joining elements for the first time. The analysis of FDJ joints requires a simplified model of the joint to enable efficient numerical simulations. The present work introduces a strategy in modeling a finite-element based analogous-approach for FDJ-joints with glass fiber reinforced polypropylene and high-strength steel. Combined with a newly developed section-force related failure criterion, it is possible to predict the fundamental failure behavior in multi-axial stress states. The functionality of the holistic approach is illustrated by a demonstrator that represents a part of a car body-in-white structure. The comparison of simulated and experimentally determined failure loads proves the applicability for several combined load cases.
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Sirén, Sebastian. "Case depth measurements on inductionhardened crankshafts by using ultrasonic backscattering method." Thesis, Uppsala universitet, Tillämpad materialvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-325021.
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Induction hardening is a complex process that requires regular verification of the case depth and the microstructure. Today this verification is done by destructive testing where a cross section is analysed. The case depth is measured by several Vickers hardness impressions and the microstructure is analysed by a light optic microscope. This master thesis was performed in collaboration with Volvo GTO in Skövde, with the target to find out if an ultrasonic backscattering method is usable for analysing the case depths on induction hardened crankshafts. This was done by verifying the results provided by ultrasonic testing with the results provided by destructive testing. The measurements were done on several crankshafts with different case depths and steel composition. The result, for crankshafts with normal case depths, shows a good correlation between the destructive testing (DT) and the ultrasonic testing (UT). The mean value for the discrepancy was 0.39 mm with a standard deviation of 0.20 mm. The reproducibility of the method has a standard deviation of 0.074 mm.
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Dube, Manu. "Constitutive modeling of joining materials in electronic packaging." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/280470.
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Modeling simplifications for complex material behavior may lead to unanticipated errors under generalized loading conditions, which are difficult to detect in finite element analyses. This work analyzes existing models under simple loading conditions where the nature of the results is known a priori, and proposes new models to overcome the limitations detected. Elastic and elastoplastic formulations for loading-dependent material parameters are generalized, and limitations of the rate-dependent elastoplastic simulation and the Perzyna viscoplastic formulation are discussed. A yield function that provides continuous yielding irrespective of the direction of loading and does not generate spurious plastic strain increments under temperature change is developed. A thermomechanical model based on the concept of superposition of asymptotic phases is also proposed, with generalized stress-strain-temperature relationships that intrinsically predict the variation of the coefficient of thermal expansion and elastic constants with temperature, and is validated for aluminum, lead, tin and solder. A plastic yield criterion shown to be in general agreement with hardening based on dislocation density and a preliminary empirical creep equation for lead-tin eutectic solder are developed as part of the thermomechanical model. Finally an approximate dissipated-work based formulation for the Disturbed State Concept of Desai (2001) is developed and limitations of DSC assumptions are discussed. Validations are conducted for the eutectic lead-tin data of Wang et al. (2001), with prior parameters being shown to require recomputation.
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Mendez, Patricio F. (Patricio Fernando). "Joining metals using semi-solid slurries." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/16706.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1995.<br>Includes bibliographical references (leaf 18).<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>by Patricio F. Mendez.<br>M.S.
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Karlsson, Hampus, and Anton Karlsson. "Konceptutveckling av en caterpillar med inriktning på kvalitet : En utvecklingsprocess." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-14996.
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When transporting a sea cable, what is commonly called a caterpillar is used, but the most common said is a cable tensioner. These machines can be found in a flurry of different variants, where there are a multitude of competitors, which applies demands to having an extremely distinctive machine. Therefore from a market analysis it have been identified that a lack of quality regarding the machines are a factor. A poor quality shortage that usually occurs in hard weather conditions, but this is something that should not happen as it may lead to machine breakdown. Semcon AB in Karlskrona constructs and then collaborates with Ronneby Svets & Smide, who manufacture cable carousels, armrests and other equipment for the cable industry but not the cable tensioner that are ordered separately by external companies. This is the background to why the project is created because Semcon sees a need to eliminate this bottleneck and also expand their product portfolio for customer recovery. The aim it therefore, together with Semcon, develop a new concept for a completely new cable tensioner with given preferences, rough drawing and selection of qualitative features for the machine in order to be competitive with its future overall solution for the cable industry. To find a solution to the described problem, a product development process has been followed to establish structure. The process include a planning, concept development, design and detailed development phase. From the first phase, a wide understanding of how the complex machine works and where its deficiencies may be. Even hidden customer needs in form of interviews with cable manufacturers in Karlskrona and with industries that handle sea cable were conducted to get a broader spectrum. The needs are transformed into specifications to generate concepts based on the rankings of the measurably formulated specifications. Followed up by an evaluation where the best concepts were taken to the design phase and detailed development. All design calculations have been made, either by hand or with computer-based programs. The work has resulted in an innovative concept of a whole cable tensioner with all key components, rough drawing, together with a new thinking solution regarding the contact face between the cable and the machine, developed through experiments and theory studies. As this project is very broad, the overall project has been divided into two master thesis works and all electronics are handles by an electrical/automation company. Therefore, for a broader understanding and information about functionality, reference is made to the second project “Konceptutveckling kring funktionerna hos en kabeldragare” authored by Anton Hansson. It is extremely important to mention that the outcome of this project is intended to be a concept for a new innovative cable tensioner. This means that with future work on the concept, which includes continued depth of calculation and further contact with suppliers, can provide an opportunity to manufacture the generated concept. Another development area Semcon must proceed with is to review the safety routines of the machine. The authors of this report believe that a highly competitive solution has been presented, and that work contributes to a strong foundation for the development of transporting sea cable technology in the future with the help of this innovative concept.
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Kapoor, Rakesh R. (Rakesh Rameshchandra). "Brazing alloys for ceramic to metal joining." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14841.
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Goldspiegel, Fabien. "Simulation numérique du procédé de clouage grande-vitesse pour l'assemblage de matériaux hybrides." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEM028/document.
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L’industrie automobile suit une politique d’allègement via l’introduction de matériaux plus légers et plus diversifiés dans la structure du véhicule. Parmi les techniques d’assemblages envisagées, le présent document se focalise sur le procédé de clouage grandevitesse. Des essais d’assemblages ont été réalisés en laboratoire sur de l’aluminium de fonderie, de l’acier DP780 et DP1180. La cinématique d’assemblage, les modes de ruptures, la réaction des tôles et les propriétés de la liaison sont étudiés. Des modèles matériaux ont été choisis pour rendre compte des phénomènes dynamiques et de rupture des tôles pendant l’assemblage. Le clou et les tôles ont ensuite été caractérisés mécaniquement dans plusieurs conditions de chargements et utilisés pour la calibration des modèles. Un modèle par éléments finis du clouage est crée; ses sensibilitées aux variations de maillage, frottement et modèle matériau sont évaluées et ses limitations capturées, soit par une pression d’assemblage inadaptées soit par la fragilité du clou. Des simulations de traction-croix et traction-cisaillement permettent finalement l’estimation des propriétés mécaniques de la liaison<br>Lightweigthing structures using mixed material components have become one of the main target of automotive industry’s future. Among the joining processes under exploration, the present work focuses on High-Speed Nailing. Experimental campaigns are conducted under laboratory conditions on layers superposition made of cast aluminium, dual-phase steels DP780 and DP1180. Joining kinematics, sheets fracture modes, reaction the nail insertion and nailed-joint strengths are investigated in various conditions of experiment. Material models are chosen to account for the dynamic and fracture phenomena exhibit by materials in the joining stage. Mechanical tests are performed on nail and sheets materials under different strain-rates and stress-states and used as references for the calibration procedure. A finite element model of the joining stage is built; its sensitivity to mesh size, friction and material formulation is evaluated and its limitations captured by either inappropriate joining pressure setting or nail brittleness. After a new equilibrium is reached, the nailed-joint is tested through cross-tension and sheartension simulations to tackle the prediction of in-service properties
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Brochu, Mathieu. "Joining Si₃N₄ to FA-129 iron aluminide." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84482.
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Joints between dissimilar materials are characterized particularly by compositional gradients and microstructural changes, which yield large variations in chemical, physical and mechanical properties across the joint. The joining of dissimilar materials is therefore more complex than the joining of similar materials. In this project, the joining procedure, from the interaction between the different components in a joint to the determination of the mechanical properties was applied to the Si3N4/FA-129 system. This iron aluminide intermetallic alloy (FA-129), was developed by Oak Ridge National Laboratories (ORNL) to have high temperature properties with good room temperature ductility. This intermetallic is replacing high strength ferritic stainless steel (SS) in moderate strength applications due to cost and property reasons. Joints between SS and Si3N4 are already used industrially and this project was to evaluate the potential to replace these Si3N 4/SS joints by those of Si3N4/FA-129.<br>Broadly stated, the results obtained during this project are as follows: (I) The E2 energy for Si3N4 ceramic was calculated to be 3.01 keV. (II) The wetting of iron aluminide alloy by copper has been achieved and the spreading and reaction kinetics are influenced by the presence of Cr as alloying element. (III) The penetration and decohesion of the FA-129 microstructure is significantly reduced by the utilization of a Cu alloy containing a high titanium concentration. (IV) An active brazing alloy containing a high active element content can be fabricated by an electroless deposition technique. (V) The melting behavior of the powder was characterized and complete melting occurs in a multi-step process at different temperatures, which are a function of the heating rate. (VI) The strength of joint produced by brazing Si3N4 to itself using the composite powder reached 400 MPa. (VII) Direct brazing of Si 3N4 to FA-129 was shown to be unsuccessful and therefore a soft Cu interlayer was inserted to absorb residual stresses. The maximum joint strength reached was 160 MPa. (VIII) Partial Transient Liquid Phase Bonding was successfully applied to the Si3N4/FA-129 system using a nickel interlayer. The conventional silicide and nitride layers were not observed as the silicide layer dissolved into the nickel core at high temperature. The strength of the assembly was measured and a strength of 80 MPa was obtained, independent of the joining parameters.
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Gårdstam, Johannes. "Simulation of mechanical joining for automotive applications." Licentiate thesis, KTH, Mechanics, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3942.
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<p>Regarding the use of material, modern lightweight car bodies are becoming more and more complex than previous constructions. The materials nowadays are used for a more specific field of application and more high strength steels are used and also other materials like aluminium, stainless steel, reinforced polymers are used more frequent. The joining of these materials often requires new or modified joining processes. The aim with this thesis is concerned with the development of simulation models of the joining process as well as mechanical properties of self piercing riveted (SPR) joints and pierce nut joints. In both of these joining methods problems occur when introducing more high strength steel sheets. For SPR, fractures occur in the rivet, and for pierce nut the thread will be damaged.</p><p>Since both the SPR process and the pierce nut process expose the material for plastic deformation up to 150%, correct material properties for very large strain and a simulation program that could handle this was required. With the commercial finite element program Deform2D an axi-symmetric model has been built for the SPR process and the pierce nut process. Because of the computational time, 3D simulations were only used where it was necessary. The developed 3D models use the commercial finite element program ABAQUS-Explicit. All simulation models have been verified with satisfactory agreement to experimental results.</p><p>For SPR, an axi-symmetric simulation model was used for evaluating and optimising the setting process in the stainless steel sheets EN1.4301, HyTens 800 and HyTens 1200. Subsequently, 3D models were used for predicting the mechanical properties of new SPR joints that have showed reduced risk for rivet cracking. In pierce nut simulations, nuts with hardness 8 and 10 have been set in the high strength steel sheet DP600. An axi-symmetric simulation model was used for centred nut setting and two different simulation models in 3D were used to evaluate eccentric nut setting and torque resistance.</p><p>This work resulted in more knowledge about the fracture risk in the rivet and how to reduce it. The strain and stress, which was used as fracture indicators, were reduced to the half with modifications of the rivet and the die geometry. Mechanical property simulations in shear and peel load resulted in satisfactory results for new SPR joints that have showed reduced fracture risk during rivet setting. New die and rivet designs can be developed effectively by combining the process and mechanical property simulations.</p><p>For a pierce nut joint in high strength steel sheets (1.5mm DP600), the simulations show that the cutting of the sheet in combination with eccentric setting over the die causes the thread damage. The thread damage can be avoided by changing the dimension of the nut or by increasing the strength of the nut material. The simulation models can also be used to develop new nut and die geometries for future applications.</p>
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Zhuang, Wei-Dong. "Applications of powder interlayers for large gap joining." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/43608.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1997.<br>Includes bibliographical references.<br>Large gap joints are frequently encountered in the manufacturing of massive components as well as in the repairing of damaged parts. Several methods using powder interlayers to produce large clearance transient liquid phase (TLP) joints have been developed and investigated in this work. One of the methods was using a mixture of powders of the melting point depressant (MPD) and the base material, from which a great amount of MPD (>30 vol.%) usually has to be used to eliminate residual porosity. To reduce the MPD in the joint, the liquid infiltrated powder interlayer bonding (LIPB) process was developed. For a material system that has a large mutual solubility between the liquid and the solid at the bonding temperature, a protective coating on the particles of the base material was applied to avoid excessive dissolution and inhibit early diffusional solidification, which can block the infiltration paths and prevent full infiltration. Direct coating of the MPD on the particles of the base material proved highly effective in producing tough and strong joints for certain material systems. The classic liquid phase sintering (LPS) theory was adopted to explain the physical process as occurring in the powder interlayer during joining. Despite the general applicability of the theory, there are several other important factors have to be considered as well. For example, the reaction rate between the MPD and the base material can markedly affect the densification of a mixed powder interlayer. Fast growth of the intermetallic compounds as a result of reaction can significantly retard the liquid flow. For the infiltration process, kinetics of dissolution and diffusional solidification largely depend on the mutual solubility between the liquid (infiltrant) and the solid (powder interlayer). Dissolution is needed to open up closed pores in the powder interlayer. However, excessive dissolution is undesirable due to fast liquid saturation and subsequent diffusional solidification, which may prevent complete infiltration of the interlayer. A protective coating on the particles of the base material provides a way of reducing the dissolution rate, which facilitates full infiltration of the interlayer. The solubility factor is also crucial for direct coating of the MPD on the particles of the base material. Higher solubility of the base material in the MPD is preferred to maintain enough liquid for complete densification. Experiments were performed on joining the materials including titanium alloy, Ti- 6A1-4V, nickel base superalloy, Inconel 625, stainless steel, SS304, and commercially pure copper. Application of the particular joining process depends on careful choice of the MPD, the base powders as well as the geometry of the interlayers.<br>by Wei-Dong Zhuang.<br>Ph.D.
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Fox, Gordon R. "Joining of Shape-Memory NiTi Torque Tubes to Structural Materials." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1331157030.
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Thomson, David. "The joining of precoated sheet steels to dissimilar contruction materials." Thesis, Swansea University, 2008. https://cronfa.swan.ac.uk/Record/cronfa42587.
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Within the UK steel industry it is believed that continued growth of steel usage in the construction sector would be facilitated by offering multi-material solutions which combine the benefits of several materials (i.e. precoated sheet steels, aluminium alloy, glass, timber and mortar). A review of both traditional and novel joining processes that are currently used to assemble sheet steels indicated that adhesive and sealant bonding has the most potential for joining both multi-metal and fundamentally dissimilar material combinations. Consequently, the aim of this Eng.Doc research project was to establish the robustness of bonded joints, test methodology procedures, and design guidelines for multi-material combinations. The results obtained in this study have shown that a range of structural adhesive and sealant systems exist, capable of producing strong and durable multimaterial joints. The highest levels of durability were obtained with organic coated steel - aluminium or glass joints which restricted the ingress of water to the exposed edges of the bond line. With precoated steel-timber or mortar joints, bond strength was adversely affected by rapid water penetration through the porous timber and mortar adherends promoting joint failure. Furthermore, it was noted that the failure loads obtained with adhesive bonded steel-timber and glass joints were higher than anticipated. This was attributed to a change in the stress distribution, whereby a greater stress concentration was located at the overlap end of the higher modulus steel adherend. Guidelines were developed describing best practice joining techniques for adhesive bonding steel - brittle materials (i.e. glass and mortar), and the requirements for further work outlined to facilitate follow up projects.
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Holmberg, Jonas. "Surface integrity on post processed alloy 718 after nonconventional machining." Licentiate thesis, Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-12191.
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There is a strong industrial driving force to find alternative production technologies in order to make the production of aero engine components of superalloys even more efficient than it is today. Introducing new and nonconventional machining technologies allows taking a giant leap to increase the material removal rate and thereby drastically increase the productivity. However, the end result is to meet the requirements set for today's machined surfaces.The present work has been dedicated to improving the knowledge of how the non-conventional machining methods Abrasive Water Jet Machining, AWJM, Laser Beam Machining, LBM, and Electrical Discharge Machining, EDM, affect the surface integrity. The aim has been to understand how the surface integrity could be altered to an acceptable level. The results of this work have shown that both EDM and AWJM are two possible candidates but EDM is the better alternative; mainly due to the method's ability to machine complex geometries. It has further been shown that both methods require post processing in order to clean the surface and to improve the topography and for the case of EDM ageneration of compressive residual stresses are also needed.Three cold working post processes have been evaluated in order to attain this: shot peening, grit blasting and high pressure water jet cleaning, HPWJC. There sults showed that a combination of two post processes is required in order to reach the specified level of surface integrity in terms of cleaning and generating compressive residual stresses and low surface roughness. The method of high pressure water jet cleaning was the most effective method for removing the EDM wire residuals, and shot peening generated the highest compressive residual stresses as well as improved the surface topography.To summarise: the most promising production flow alternative using nonconventional machining would be EDM followed by post processing using HPWJC and shot peening.
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Bozzo, Closas Bernat. "Superconducting joining of melt textured YBCO bulks." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/369047.
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La obtenció de ceràmiques superconductores de YBa2Cu3O7 porta implícita una limitació en les dimensions i forma de les peces. Per tal de superar aquesta limitació, s’ha proposat un mètode de soldadura basat en l’ús d’una làmina de plata com a decapant.
Aquest treball de Tesi està enfocat en:
• El perfeccionament de la tècnica de soldadura de YBCO per tal de resoldre una sèrie de problemàtiques presents en el moment de començar aquest treball.
• Caracterització de la microestructura de les mostres soldades.
• El desenvolupament d’eines d’anàlisi quantitatiu per avaluar la qualitat de la soldadura des del punt de vista de les propietats magnètiques i elèctriques.
• La expansió del mètode de soldadura per incloure soldadures on existeix una desorientació cristal·logràfica entre les dues peces unides i estudi de la influència d’aquesta desorientació en les propietats magnètiques i elèctriques.
El primer pas seguit fou la construcció d’un forn equipat amb un sistema d’observació òptica in-situ. Aquest sistema va permetre obtenir gravacions de l’evolució de la mostra durant el tractament tèrmic. Aquests vídeos van permetre detectar la presència de dos tipus de líquids que eren arrossegats fora de la zona de soldadura. L’estudi de la microestructura de la soldadura van indicar que aquesta pèrdua de líquid afavoria l’aparició de defectes microestructurals. Una modificació del porta-mostres emprat solucionà el problema.
Es van realitzar estudis de la microestructura més detallats per tal de poder entendre millor els mecanismes que en fan possible la seva formació amb la idea de postular-ne un possible model.
Un estudi adequat de les propietats magnètiques també fou necessari, ja que l’objectiu final del mètode de soldadura és el d’unir diverses peces de YBCO, tot mantenint les propietats superconductores a la zona soldada. Per aquest motiu, es van realitzar mesures d’imatge magnètica, basades en una Sonda d’Efecte Hall. A partir dels mapes de magnetització local de les mostres, es va obtenir la distribució de densitats de corrent crítica, emprant un programari especialitzat. Per tal d’entendre millor aquests mapes de densitat de corrent i, també, per extreure’n informació útil, es va desenvolupar un programari de simulació i els coneixements adquirits, es van poder obtenir les densitats de corrent intergranular i intragranular (JcGB i JcG).
Es va estudiar la dependència del quocient entre JcGB i JcG amb l’angle de desorientació cristal·lina. En principi s’esperava una dependència semblant a la que es troba en el cas de les cintes superconductores. No obstant, la dependència que es va trobar era més fluixa que la del cas model considerat.
Aquesta dependència es va comprar, llavors, amb la d’altres estudis similars, fets amb fronteres de gra artificials en mostres superconductores volumètriques, revelant un comportament semblant entre elles, indicant que el valor del quocient JcGB/JcG era potencialment intrínsec al grau de desorientació. Aquesta hipòtesi es va confirmar quan es van comparar mostres de YBCO amb qualitats diferents, però amb el mateix angle de desorientació.
Es van realitzar mesures dels mapes de magnetització en funció del camp magnètic per tal de determinar els règims d’ancoratge de vòrtexs presents en les mostres i es van comparar amb el cas de les cintes superconductores. Tot i que els règims d’ancoratge en la zona de soldadura són similars als de les fronteres de gra per una cinta superconductora, els règims en zones fora de la soldadura difereixen entre els dos casos.
Finalment, es van realitzar mesures de nanoindentació per tal de correlacionar les propietats mecàniques amb les elèctriques. Concretament, es va avaluar la duresa del material en la zona de soldadura i fora d’aquesta zona. El quocient entre les dues dureses mostraven una gran correlació amb el valor del quocient JcGB/JcG.<br>The obtention of bulk YBa2Cu3O7 tiles by the Top Seeded Melt Growth method carries and implicit limitation on the shape and size of the pieces. In order to overcome this limitation a joining method based on the use of an Ag foil as a welding agent has been proposed.
This thesis work was focused in the following aspects:
• The refinement of the welding methodology for YBCO pellets in order to solve the issues present.
• Characterization of the microstructure of welded pellets.
• The development of suitable quantitative analysis tool for evaluating the weld quality in terms of its superconducting behavior.
• The expansion of the methodology to include welds with crystallographic misorientation and study the influence of such a crystallographic misorientation on the electric and magnetic properties
The first step was to develop a furnace bundled with an in-situ observation video setup that allowed visually record the evolution of the sample during the thermal process. Those videos revealed the existence of two types of liquids that were dragged out from the weld position. The microstructural study carried out on the welded samples indicated that this loss of liquid was the source of microstructural malformations at the weld position. A modification on the sample holder was required and solved the issue.
All the studied samples were analyzed under the scope of their micro-structural characteristics and their magnetic properties.
For the case of the micro-structural characterization, a basic study was carried out in order to determine the successfulness of the weld formation and it was used as a feedback parameter for fine-tuning the thermal process. The weld microstructure was further investigated in order to obtain more information about its characteristics and in order to obtain a better understanding about the mechanisms that make the weld formation possible.
A proper study of the magnetic and electric properties was also required, since the final objective of the superconducting welding technology is to join several YBCO tiles while maintaining the superconducting properties at the weld position. For that purpose, magnetic imaging Hall Effect based measurements were performed on the specimens under study. From the local magnetization maps, current density distribution maps were obtained by using specialized software. In order to understand and obtain useful information from those current density maps, a simulation software piece was developed and the knowledge acquired from those simulations allowed obtaining the inter- and intra-granular critical current density values (JcGB and JcG) from each sample.
The ratio between JcGB and JcG was studied as a function of the misorientation angle. In principle, a behavior similar to coated conductors was expected. However, the dependence found was weaker than the considered model case.
That determined dependence was compared with similar studies on grain boundaries in bulk YBCO, revealing a similar behavior and indicating that the JcGB/JcG ratio value was potentially intrinsic to the misorientation angle. This hypothesis was confirmed when several samples with different YBCO grain characteristics but with the sample misorientation were compared.
Field dependence measurements of the magnetization maps were also performed in order to determine the vortex pinning regimes present at the samples and to compare them with the thin film case. Despite the weld pinning regimes were similar, the behavior at the grain was slightly different.
Finally, the superconducting properties were correlated with the mechanical properties. The hardness of the material was evaluated by using nano-indentation techniques at different positions. The ratio between the hardness at the weld and away from the weld exhibited a high correlation with the JcGB/JcG ratio.
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Zhang, Peihui. "Joining enabled by high velocity deformation." Columbus, Ohio : Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1061233577.
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Thesis (Ph. D.)--Ohio State University, 2003.<br>Title from first page of PDF file. Document formatted into pages; contains xvi, 255 p.; also includes graphics (some col.). Includes abstract and vita. Advisor: Glenn S. Daehn, Dept. of Materials Science and Engineering. Includes bibliographical references (p. 201-202).
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Wang, Qiuwan. "STUDY OF DIRECT JOINING OF HYBRID STRUCTURE BETWEEN MILD STEEL AND THERMOPLASTICS." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1469210390.
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Zhong, Zhihong. "Development of Technologies for Joining of Silicon Carbide Materials to Metals." Kyoto University, 2010. http://hdl.handle.net/2433/120415.
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VENTRELLA, ANDREA. "JOINING OF CERAMIC COMPOSITES AND ADVANCED CERAMICS." Doctoral thesis, Politecnico di Torino, 2012. http://hdl.handle.net/11583/2502686.
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Ceramics and Ceramic Matrix Composites (CMC) are well known as useful materials for harsh environment applications. Ceramic components have been widely used as abrasives, cutting tools, nuclear fuel elements, catalyst supports and astronomical telescope mirrors. Generally speaking, ceramics and CMC are excellent candidates for high-temperature applications because of their good mechanical properties and thermal stability at elevated temperatures.
However, to produce large-size and complex components, development and testing of joints for ceramics and CMC are fundamental. Joining materials and techniques currently available to join ceramic and CMC include diffusion bonding using various active fillers, transient eutectic phase methods such as nano-infiltration and transient eutectic-phase (NITE), laser joining, selected area chemical vapor deposition , glass-ceramic joining , solid state displacement reactions, preceramic polymer routes, reaction forming, brazing. Adhesive joining materials (e.g. epoxy resins) are used to join ceramics only for applications at temperature lower than 150 °C, i.e. adhesively bonded joints are widely used for automotive, aerospace, electronic and packaging applications.
Together with the need of a reliable joining method, a widely accepted standard to test the mechanical strength of joined ceramics and composites is still unavailable and measuring the shear strength of the same joining material with different test methods could lead to different results.
The aim of this Thesis is to compare and discuss several different shear strength tests used to join ceramics and CMC, with the final goal to provide designers and scientific community a widely accepted, reliable test method.
A homogeneous pure shear stress state is not obtainable with most of the currently used single or double lap tests, which give apparent and not pure shear strength of the joined samples; in addition, the presence of several different apparent shear strength tests in the literature makes comparison quite impossible.
The asymmetrical four point bending test (ASTM C1469-10) is recommended as a standard test by the ASTM to test joined ceramics and composites, but notches have to be cut in the joined area when the joining material strength is high. When the shear strength of the joining material approaches that of the substrate to be joined, ASTM C1469-10 is not suitable.
With torsion tests a pure shear loading strength can be measured without using notches.
One of the very first proposals for torsion test for epoxy bonded aluminum alloy samples was reported by M. Ouddane et al.: as thoroughly discussed there, torsion results were considered more reliable than those obtained by standard lap tests, the improvement mainly due to the fact that lap tests induce non uniform stress concentrations that affect the reliability of results.
Recent papers deal with torsion tests on joined hourglass shaped samples : preliminary results suggest that the torsion test method with a miniature specimen has a potential to evaluate the shear properties of the joint interface, provided that the fracture occurs in the joined area.
Torsion tests have been thoroughly analyzed in this Thesis: a pure non-uniform shear stress distribution is obtained with torsion tests; together with asymmetrical four point bending test (ASTM C1469-10), torsion test is the only one able to measure pure shear strength of joined ceramics and composites.
The torsion test method is proposed in some ASTM standards but none of them is directly applicable to joined ceramics: the main result of this Thesis is to demonstrate the reliability of torsion as a method to measure the shear strength of joined ceramics and CMC.
Two torsion standards have been adapted to joined C/C and ceramics, first by preparing square section samples (TS), rods (TC), tubes (TT), then by mechanically shaping the joined samples as a hourglass in different shapes.
The choice of an epoxy resin (Araldite AV119) to join SiC in this PhD thesis was done in order to have a “model” brittle joining material to obtain a statistically relevant number of joined samples in a reasonable time, to compare shear strength results .
More than one hundred joined samples have been prepared and tested at room temperature by asymmetrical four point bending (A4PB) (ASTM C1469-10), torsion on square section samples (TS), torsion on circular section rods (TC), torsion on hourglass shaped samples (THG, TDHG, TRHG), torsion of tubes (TT), single lap in compression (SL), single lap off set in compression (SLO), double lap off set in compression (DLO), Brazilian test (BT), double notch (DN) methods. A modified ASTM B898 standard has been used as a further example of single lap test in compression to complete the comparison work (B898).
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Riggs, Mark R. "TIG Welding of Nickel Titanium to 304 Stainless Steel." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1397607979.
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Kulkarni, Rahul R. "Joining of aluminum and long fiber thermoplastic (LFT) composites." Birmingham, Ala. : University of Alabama at Birmingham, 2007. https://www.mhsl.uab.edu/dt/2008r/kulkarni.pdf.
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Thesis (Ph. D.)--University of Alabama at Birmingham, 2007.<br>Additional advisors: Derrick R. Dean, Alan W. Eberhardt, Ramana G. Reddy, Uday K. Vaidya. Description based on contents viewed Feb. 13, 2009; title from PDF t.p. Includes bibliographical references.
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Evans, William Charles. "Advancements in Joining Armor Grade Steels." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1556816907125644.
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Boonyongmaneerat, Yuttanant. "Sintering and joining of low temperature co-fired tungsten and aluminum oxide." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36204.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006.<br>Includes bibliographical references (p. 181-189).<br>Conventional methods used to fabricate co-fired tungsten/alumina composites usually rely on high temperature processing (>1500C). As it would be beneficial or even necessary for some applications to produce such composites at relatively low firing temperatures, low-temperature processing techniques and the attendant knowledge of processing-property relationships need to be developed. In this thesis, a set of experiments and simulations are performed to obtain a better understanding of sintering and joining of the tungsten/alumina system processed at temperatures near or below 12000C. The technique of activated sintering for tungsten is investigated, whereby a minimal content of additives enables low firing temperatures through a change in the sintering mechanism for tungsten. Tungsten compacts produced by this method are found to sinter only to the "initial stage" and are characterized by high residual porosity level. Hardness and fracture toughness of such partially-sintered materials are examined experimentally and analytically, and dependence of mechanical properties on the relative particle neck size is observed. Various studies are carried out to examine both fundamental and practical aspects of joining co-fired tungsten/alumina.<br>(cont.) First, contributions to adhesion of co-sintered bilayers are studied where the properties of the tungsten layer are controlled using the process of activated sintering. Using a bending delamination test, improvements in sintered density of tungsten are found to increase the adhesive strength of the system only up to a point, beyond which shrinkage mismatch compromises the intrinsic toughness of the interface. A study of low-temperature co-fired tungsten/alumina is then focused on composite shells for an investment casting application. The influences of various processing parameters in a slurry-based route on the sintering and adhesion properties of tungsten/alumina are investigated. Binder content, stucco sand application, and powder characteristics are among the parameters found to critically control the quality of tungsten/alumina shells produced. Finally, the feasibility of several joining strategies, which involve the use of chemical additives, is examined on co-fired tungsten/alumina compacts processed at low temperatures. Some bonding techniques are verified to help improve the bonding of the co-sintered composites.<br>by Yuttanant Boonyongmaneerat.<br>Ph.D.
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Brolin, Nord Elin. "En studie av skador hos stolar från renässansen 1560-tal till biedermeier 1850-tal. : Ett arbete om sambandet mellan konstruktion, material och skadebild." Thesis, Linköpings universitet, Malmstens Linköpings universitet, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-150581.
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Through the selection of six representative typical Swedish chairs from each era, I present manufacturing techniques and how the craftsmanship has affected the style of the chairs over time. My main source material is the objects themselves. I chose to analyze the constructions and what can distinguish them apart in techniques, material choices, aesthetics and design. The main part of my work has been to find out what are the most occurring damages and its causes. Most damages from renaissance to biedermeier can be linked to the mortise joint. Through interviews with experienced conservators and with my own experiences as a cabinet maker and conservator, I discuss the concept of the ultimate chair design in terms of stability. I have come to the conclusion that the most solid chair is the eight to twelve framed chairs from the Renaissance, but the chair must be adapted to the intended use.
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Sorensen, Daniel David. "Dissimilar Metal Joining in the Medical Device Industry." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1494157928729494.
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Coelho, Rodrigo Santiago. "Joining of light-weight materials by friction stir welding and laser beam welding." Berlin Bochum Dülmen London Paris Europ. Univ.-Verl, 2008. http://d-nb.info/994359489/04.
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Joesbury, Adam Michael. "New approaches to composite metal joining." Thesis, Cranfield University, 2015. http://dspace.lib.cranfield.ac.uk/handle/1826/10009.
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This thesis explores new methods for achieving load-carrying joints between the dissimilar materials of continuous fibre reinforced polymer matrix composites and structural metals. The new composite-to-metal joining methods investigated in this work exploit the metal-to-metal joining techniques of arc micro-welding, resistance spot welding, and metal filler brazing, to form novel micro-architectured metal adherends that can be used for enhanced composite-to-metal joining. Through a combination of equipment instrumentation and metallographic inspection of fabricated prototype joints, understanding is gained of how materials respond when processed by manufacturing techniques that have not previously been exploited for dissimilar material joining. Mechanical testing of prototype joints; both to ultimate loading strength and partial failure states, with subsequent inspection of specimens and comparative performances evaluation enabled joining performance characterisation of the new joining methods. Key results include: the identification of micropin reinforced adhesive joints to exhibit pseudo-ductile failure characteristics, resistance spot weld reinforcement of adhesive joints to boost bonding performance, and the use of a polymer infused metal foam to overcome difficulties of thermoplastic to metal adhesion. Through this work knowledge of how novel micro-architectures reacted under mechanical loading enabled insights to be gained into how perceived manufacturing defects can benefit joining performance. Such examples include, localised material weakness that lead to global pseudo-ductile failure behaviour, and low-strength secondary joining mechanisms boosting primary load transfer systems. By comparison of the diverse joining methods investigated in this work, trends were identified that suggest joining performance between the two dissimilar materials is improved by increasing the direct interaction between the composite reinforcement fibres and the metal structure. It is demonstrated that joining improvements are gained by forming mechanical connections between metals and composite precursory material before the final manufacturing process of the composite.
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Gingerich, Mark Bryant. "Joining Carbon Fiber and Aluminum with Ultrasonic Additive Manufacturing." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461161262.
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