Dissertations / Theses on the topic 'Manufacture of aluminium parts'

Saab Surveillance in Järfä̈lla constructs complex products, such as radars and electronic support measures. Saab sees an advantage in manufacturing details with additive manufacturing as it enables a high level of complexity. Additive manufacturing is relatively new in the industry and consequently there are uncertainties regarding the process. The purpose of this bachelor thesis was to improve the knowledge of the repeatability of additive manufactured parts as well as compare additive manufactured test rods in two different directions, horizontally and vertically, to subtractive manufactured test rods with a vibration test. The vibration test was conducted to simulate the operative environment where the additive manufactured parts might be implemented in the future. Before the vibration test could be performed, the test rods were designed in a 3D-modeling program and analysed with a finite element method to achieve the required natural frequency range of 100 - 200 Hz and a maximal bending stress of 60 - 80 MPa in the notched area of the test rod. It was concluded that the subtractive manufactured test rods had the highest repeatability. The horizontally additive manufactured test rods had a higher repeatability than the vertically additive manufactured test rods, but the vertically additive manufactured test rods had the highest overall strength. It was also concluded that more studies are needed to ensure that additive manufactured parts can be produced with high repeatability while maintaining the structural integrity.
Saab Surveillance i Järfä̈lla konstruerar komplexa försvarsprodukter som till exempel radarsystem. Additiv tillverkning i metall möjliggör tillverkning av produkter med hög komplexitet, men då tillverkningsprocessen är relativt ny i industrin finns det en stor osäkerhet kring processen. Syftet med detta kandidatexamensarbete var att få en bättre förståelse för repeterbarheten hos additivt tillverkade delar samt att jämföra additivt tillverkade provstavar konstruerade i två olika riktningar, horisontellt och vertikalt, med svarvade provstavar med hjälp av ett vibrationstest. Vibrationstestet genomfördes för att simulera den operativa miljön där de additivt tillverkade detaljerna skulle kunna implementeras i framtiden. Innan vibrationstestet kunde utföras simulerades provstavarnas design i en mjukvara för 3D-modellering. En finit element-analys utfördes även fö̈r att få en egenfrekvens inom intervallet 100 - 200 Hz och en maximal böjspänning mellan 60 - 80 MPa i anvisningen på provstaven. Slutsatsen drogs att de traditionellt bearbetade stavarna hade den högsta repeterbarheten. De horisontellt additivt tillverkade stavarna hade högre repeterbarhet än de vertikalt additivt tillverkade stavarna, men att de vertikalt additivt tillverkade stavarna hade ett längre utmattningsliv. Det kunde även konstateras att fler studier inom ämnet behövs för att kunna säkerställa repeterbarheten hos additivt tillverkade delar utan att behöva kompromissa med hållfastheten.

This thesis is dedicated to a study of manufacturing of aluminum parts at Alfa company. A complete analysis of the company's main product which are roller doors for commercial vehicles is elaborated. The thesis is based on a existing operation of the company and tries to find the optimal solution for the future. The result is the definition of a new solution and determination it’s operating costs, economic impacts and suggestions for improvement. Key words roller door, aluminum profiles, slat, roller shutter, manufacturing of aluminum parts.

This study identifies the concepts of reliability, cost of downtime, cost of spare parts, and procurement lead time as the four key moderators of spare parts availability. These concepts are used to establish a model to manage spare parts inventories. Reliability was assessed in terms of developing failure predictions for major component categories. Cost of downtime was evaluated by identifying various methods for determining costs associated with downtime. Cost of spare parts was examined to find correlations with economic indicators. These correlations were used to predict future price movements. Yearly changes in lead time were identified and correlated with economic indexes to develop movement predictability.

Additive manufacturing of aluminium alloys using selective laser melting (SLM) is of research interest nowadays because of its potential benefits in industry sectors such as aerospace and automotive. However, in order to demonstrate the credibility of aluminium SLM for industrial needs, a comprehensive understanding of the interrelation between the process parameters, produced microstructure, and mechanical behaviour is still needed. This thesis aims at contributing to developing this comprehensive understanding through studying the various aspects of the process, with investigation of the powder raw material to the near fully dense samples, focussing on the alloy AlSi10Mg. The primary building blocks in the SLM process are the single tracks. Their formation is affected by the physical properties of the material that control the laser-material interactions. Keyhole mode melting was found to be dominant when processing AlSi10Mg, producing conical-shaped melt pools. Porosity was not evident in single tracks and individual layers. Satellites and balling defects, however, were observed on top of the tracks and layers at higher scan speeds, which contribute to porosity formation with layer progression. The combination of process parameters controls the amount of porosity formed, with the scan speed controlling the type of pore; metallurgical or keyhole pore. A pre-melt scan strategy significantly reduced porosity and successfully produced 99.8% dense samples. Furthermore, the pre-melt scan strategy was seen to effectively reduce the number of pores developed when using powder that does not fully comply with the process standards. The gas flow rate within the process chamber controlled laser spatter and condensate removal during processing, which in its turn affected the degree of porosity in the samples. The SLM process resulted in an AlSi10Mg alloy with a characteristically fine microstructure, with fine equiaxed grains at the melt pool core and coarser elongated grains at the boundary. The material showed a strong texture, owing to directional solidification. Cellular dendritic Al with inter-dendritic Si was observed. The material was subjected to a T6 heat treatment that transformed the microstructure into spheroids of Si in the Al matrix. This study investigated, for the first time, the local mechanical properties within the SLM material using nanoindentation. This showed a uniform nano-hardness profile that was attributed to the fine microstructure and good dispersion of the alloying elements. Spatial variation within the material was recorded after the T6 heat treatment due to phase transformation. This study is also the first to report on the compressive behaviour of solid SLM material, which is important for developing prediction and simulation models. The heat treatment softened the material and provided it with an increased ductility under indentation, tensile, and compressive types of loading. In addition, the material showed good fatigue performance, which was further improved by heat treatment and machining to obtain a smoother surface roughness. This investigation has, therefore, developed an understanding of the various aspects of the SLM process yielding near fully dense parts and defined the microstructure-mechanical property interrelation promoting the process for Al alloys in a number of industrial sectors.

To manufacture a high precision component, the aircraft industry in particular, employs computer numerical control machining to produce the aircraft components. However, it has often been found that problems of distortion occur when thin and slender components are manufactured this way. It is believed that the distortion arises due to the re-distribution of the residual stress field that was present in the original component in addition to the effects of cutting forces and temperatures that were induced during the machining process. At present, the process to produce a component with acceptable tolerance limits is one of trial and error. This often consumes a lot of time and produces considerable material wastage. The finite element method has been used to develop a methodology to model the actual machining process that produced the aircraft component. The finite element model that has been developed so far was able to demonstrate the effects of redistribution of the residual stresses on the distortion of the final machined component. It was found that the final component distorted differently when the materials were simply removed from a solid billet with different material removal sequences. A preliminary investigation on the effects of cutting temperature and forces has also been made. The investigation showed that such effects could not be totally ignored as they significantly affect the distortion of the final component. In addition to modelling the machining process, a methodology has also been developed to introduce and simulate the clamps and machine worktable that are part of the machining process. Although there is a considerable amount of work relating to modelling machining processes, there has not been any previous attempt to address the problem as a whole as described in this thesis. It is hope that the work undertaken here would be able to provide a stepping-stone to such attempts in future. However, further experimental data would be required to complement a more refined model in the attempt to accurately predict the distortion in machined components. It is believed that it would be possible to then extend the developed methodology to minimise the distortion by changing the machining sequence and the shape of the material to be removed. This would reduce the timescales involved to correct the problems of distortion and eliminate material wastage.

Rapid manufacture refers to those processes in which a component can be manufactured without the need for specific tooling. This reduces the time between the design stage and production of finished parts compared with traditional methods such as forging or casting. There are a number of laser based rapid manufacture processes currently available such as selective laser sintering and direct laser deposition which are both based on adding powder form material to a substrate in a layer-by-Iayer fashion. Subtractive methods such as laser milling have been developed to a lesser extent but are lirriited by low removal rates and problems caused by heat affected zones. Here, three new subtractive methods of laser rapid manufacture of near net shape titanium components were developed. Each was investigated and the most promising was chosen for further research. The chosen method is based on water assisted laser processing of partially sintered titanium powder. A block is made by partial sintering of titanium powder in a furnace such that it has the properties of being strong enough to be handled but still porous, with the powder particles retaining their spherical shape. The block is then soaked in liquid so that the interconnected pores become filled. A laser is used to irradiate the surface of the block which causes material removal from the irradiation site in a predictable way. The process was characterised by investigating the influence of process parameters: sintering temperature, laser energy density, powder particle size, laser repetition rate and type of liquid used to soak the blocks. The process was also analysed using high- . speed photography, emission spectroscopy and the probe-beam extinction technique to gain an understanding of the material removal mechanism. A computational model of the process was proposed based on the Smoothed Particle Hydrodynamics method. It was found that the mechanism of material removal is based on the explosive boiling of the liquid in the pores of the partially sintered block caused by heating from the laser. The rapid expansion of the exploding water creates a pressure which breaks the weak bonds between particles and ejects them from the surface. The new method can be faster than the current additive laser based rapid manufacture techniques and uses lower laser powers than the current laser milling processes. This is achieved through the choice of experimental conditions and laser parameters.

Today, high levels of precision and accuracy are needed in manufacturing to meet the increased complexities in product designs. Most products consist of multiple assembled parts, and fitting these parts together can present a major challenge, especially for complex products. Thus manufacturing with high precision is particularly required, and CNC machining is typically used as a machining process to reduce the risk of parts not fitting together in the assembly process, especially for automatic assembly. Thereby improving quality control and reducing scrap in high-value and low volume production. Over the last 60 years, NC and CNC machines have been used to improve product quality due to their increased accuracy. However, even with today’s more sophisticated machine tools, errors still occur during machining. The literature shows that there are numerous sources of error in machining processes. Additionally, different methods are being used to define and subsequently correct these errors. The methods used to compensate these errors typically depend on offline error compensation. A gap in the existing research methods has been identified as a lack of online error compensation methods to enable parts to be manufactured to specification and corrected during the machining process. The major contribution of this research is the design and implementation of a method for production of right-first-time parts based on an online error compensation. The proposed framework, CLosEd loop MAchining and inspecTIon System (CLeMatiS), is considered to be an important approach for industry to improve the machining and measuring accuracy for high-cost parts. A computational model has been developed, where an algorithm within this model can handle different types of feature relationships and is able to update feature positions based on on-machine measurements. This research shows that the proposed method for compensating the machining errors in order to machine parts right-first-time provides advantages over traditional methods. The method thus improves the positional accuracy of machined features while maintain the relationships between them, compared to the traditional machining.

Thèse (M.Eng.) -- Université du Québec à Chicoutimi, 2007.
La p. de t. porte en outre: Mémoire présenté à l'Université du Québec à Chicoutimi comme exigence partielle de la maîtrise en ingénierie. CaQQUQ Bibliogr.: f. 117-120. Document électronique également accessible en format PDF. CaQQUQ

The automotive industry has shown an increasing interest in the use of aluminium castings to produce, light, high performance, complex shaped parts. In gravity die-castings, the die and its design are central features. The project is designed to enhance the understanding of the influence of the die on the solidification behaviour of commercial Aluminium-Silicon Alloy (LM25) casts and addresses the question of how closely a numerical model can simulate an industrial casting process. The simulation work was based on the MAVIS FD-casting package. Experimental measurement methods were developed and were applied to monitor and analyse the temperature profiles of some production and test dies during industrial batch trials. The results were correlated with trends in parameters obtained from the numerical model. Extensive numerical heat transfer and solidification modelling was applied in order to predict the effects of specific changes to the die construction. Attempts were made to manage die thermal-gradients using targeted water-cooling. Measurements of the 'as-cast' microstructures were correlated with monitored thermal-profiles of the dies and with the predictions of numerical models. Both the simulation studies and measurements confirmed that die shapes tended to have very little influence on the macro-freezing pattern of the castings. The water-cooling had the effect that the die temperature dropped and the dendrite arm spacings were reduced but the principle-freezing pattern remained the same. However, the freezing pattern was found to be sensitive to the presence or absence of the mould coating. Measured die temperatures and the principle-freezing patterns were predicted well by the numerical model. The precision of spot parameter values however depended very much on the tuning of the model. Values of simulation variables evaluated for a test-piece casting were not necessarily transferable to simulation of commercially cast automotive brackets.

Thesis (MEng)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: There is a strong focus on the use of titanium and its alloys in the aerospace industry due to the high ultimate tensile strength and high strength-to-weight ratio of the material. The high performance nature of the material also makes it difficult and costly to machine. South Africa has the second most abundant titanium resources in the world in the form of rutile and ilmenite but no value chain to produce titanium parts from the ore. Currently, the ore is sold overseas at low prices. There exists an initiative to create a full titanium value chain in South Africa by the Department of Science and Technology. This project forms part of this initiative, where local industry is equipped with knowledge and skills to produce and machine titanium parts. The focus of this study is to determine whether it is possible to machine titanium aerospace parts at a local industry partner and equip the industry partner with knowledge and skills in order to facilitate effective and economical machining of these parts. Daliff Precision Engineering was selected as the local industry partner and specific demonstrator parts were selected on which to base the study. The process the industry partner currently uses to machine aerospace parts from difficult-to-machine alloys was studied and evaluated. It was found that about 70% of the machining time was spent on a single roughing process, hence the decision to study the roughing process in an attempt to establish whether improvement was possible. Pilot tests were done at the facilities of the industry partner and time savings of 95% were realised on the roughing process. A 2-level 3-factor Design of Experiments methodology was followed for experimentation and analysis of titanium machining at the industry partner. The roughing process of the demonstrator part was simulated on the CNC machining centre and the depth of cut, cutting speed and feed per tooth were selected as the factors, and the response was tool wear. A statistical analysis was done using Modde 9.1 design of experiments software and an optimisation model was created in order to determine a feasible set of cutting parameters, maximise material removal rate and have a target amount of tool wear. The findings show that it is possible to economically machine titanium aerospace parts with a selected geometry at the industry partner without the need for significant capital investments. The industry partner can use the knowledge generated in this project to validate their titanium machining capabilities and form part of the titanium value chain that is being developed in South Africa.
AFRIKAANSE OPSOMMING: Daar is ‘n groot fokus op die gebruik van titaan allooie in die lugvaart nywerheid, as gevolg van die material se hoë trek-sterkte en hoë sterkte-tot-gewig verhouding. Die eienskappe wat die material so aantreklik maak, is ook die rede wat dit moeilik en duur maak om te masjineer. Suid-Afrika het die tweede grootste titaan reserwes in die wêreld in die vorm van rutiel en ilmeniet erts, maar geen waarde ketting om titaan onderdele te vervaardig van die erts af nie. Die erts word tans oorsee verkoop teen lae pryse. Daar is tans ‘n inisiatief om ‘n titaan waardeketting in Suid-Afrika te skep deur die Departement van Wetenskap en Tegnologie. Hierdie projek vorm deel van hierdie inisiatief om die plaaslike nywerheid toe te rus met kennis en vaardighede om titaan produkte te vervaardig. The fokus van hierdie studie is om te bepaal of dit moontlik is om titaan lugvaart onderdele te masjineer by ‘n plaaslike industrie-vennoot en om hierdie vennoot met kennis en vaardighede toe te rus om hierdie onderdele effektief en ekonomies te vervaardig. Daliff Precision Engineering is gekies as die plaaslike industrie-vennoot en spesifieke demonstrator onderdele is gekies om die studie op te baseer. Die proses wat die industrie-vennoot tans gebruik om moeilik-om-te-masjineer allooie te masjineer is bestudeer en ge-evalueer. Daar was bevind dat 70% van die masjineringstyd bestee word aan ‘n enkele uitrof-proses. Daar is besluit om vas te stel of die uitrof-proses verbeter kan word. Loods-eksperimente is gedoen by die industrie-vennoot se fasiliteite en ‘n tydsbesparing van 95% is gevind op die uitrof-proses. ‘n 2-Vlak 3-faktor eksperimentele ontwerp metodologie is gevolg om eksperimente by die industrie-vennoot op titaan uit te voer en te analiseer. Die uitrof-proses van die demonstrator onderdeel is gesimuleer op die CNC masjineringsentrum en die diepte van snit, snyspoed en voer per tand is gekies as die faktore en beitel-slytasie is gekies as die respons. ‘n Statistiese analise is gedoen deur Modde 9.1 eksperimentele ontwerp sagteware te gebruik om ‘n moontlike stel van sny-parameters te identifiseer om die materiaal-verwyderingstempo te maksimeer en die teiken waarde vir beitel-slytasie te bereik. Daar is gevind dat dit moontlik is on titaan lugvaart onderdele met ‘n spesifieke geometrie ekonomies te masjineer by die industrie-vennoot, sonder om enige beduidende kapitaal uitgawes aan te gaan. Die industrie-vennoot kan die kennis gebruik wat geskep is deur die projek om hulle titaan masjineringsvaardighede te valideer en om deel te vorm van die titaan waardeketting wat besig is om in Suid-Afrika ontwikkel te word.

Pallets are the single largest consumer of hardwood lumber in the United States. While the pallet industry has effectively adopted widespread pallet recycling, many pallets still go into landfills with little or no value gained from their material. Recovered pallet lumber has been proposed as a potential source of material for value added wood products. This study sought preliminary data on issues pertinent to the development of pallet parts as a source of raw material for value added products, with a focus on oak strip flooring. Issues examined included pallet disassembly efficiency, characteristics of recovered boards, and yield of blanks compatible with commercial flooring production. Disassembly of pallets was affected by pallet design. Overall 81% of the deckboards from all pallet designs were recovered, along with 70% of stringers. Oak boards useable in strip flooring represented 21% of the recovered boards studied. Proper board stacking was found to maintain a uniform (MC) which would reduce drying defects and complications. The manufactured blank dimensions would allow production of some of the thinner strip flooring commercially available. National Oak Flooring Manufacturers Association Pre-finished Oak Strip Flooring Grading Rules found almost 80% of the blanks made Prime and Standard Grades. Wide spread adoption of flooring production from recovered pallet would increase the value of recovered pallets, presumably justifying an increased rate and expanded scope of pallet recovery. Economics favoring such valued added recovery would create recovery-related jobs, decrease pallets going into landfills, and ease the demand on timber resources.
Master of Science

This PhD-Thesis focuses on initial investigations of tube hydroforming (THF) as a new technology in the field of micro-part manufacture. THF has been widely adopted in the automotive industry for approximately fifteen years and is now commonly used in many other industries. In the forming process the semi-finished part is formed with the aid of a forming liquid which acts inside the hole of the tube. Under the influence of hydrostatic pressure and additional mechanical loads the tubular blank is forced to conform to a given die cavity giving the part its final shape. In comparison to "conventional" procedures for the manufacturing of hollow-shaped constructional work pieces, as for instance the welding of deep-drawn metal sheets, THF offers many advantages by enabling the production of parts having: - Complex and variable cross sections in their longitudinal axis - High strength due to cold-work hardening and homogenous grain structure - High rigidity achieved by closed cross-s ections - Narrow tolerances in their outer dimensions - Optimized transitions for fluid transport Further on, THF especially offers a considerable time saving potential for manufacturing hollow shaped components compared to currently used techniques based on the removal of material. However, current state-of-the-art manufacturing of hydro-formed parts is still restricted to conventional parts which well exceed micro-part dimensions. Micro-THF as a new technology would add all these advantages to the micro technology sector and can establish access to other new fields and application. Examples of micro-hydroformed components are all hollow straight as well as bent components with complex shapes which currently cannot be (mass-)produced with any other micro manufacturing technology; components such as elements for micro-fluidic chips, micro heat exchangers and fluidic sensors or tubular parts for endoscopes etc. The research performed aimed at carrying out the fundamentals of process design necessary for hydroforming micro-parts. Investigations were carried out on tubular parts having an outer diameter smaller than 1 mm and a length of ca. 10 mm. Extensive studies regarding material properties of micro-tubes especially its forming abilities were conducted and procedure limitations identified and analysed. In order to examine extended forming limits and to approach the so-called size effects which arise from scaling down a traditional forming process to micro-level, the process has further been investigated under the influence of laser energy. A diode Laser was used to increase the temperature of the tube material during forming, reducing the flow stress and increasing the ductility in the required area of the part. Additionally, numerous theoretical design studies had been performed which led to the development of the entire forming machine components. As a result of the intensive research and development work carried out, process specific fundamentals suitable f or an industrial application were established as well as the world's first micro tube hydroforming prototype machine was constructed that successfully manufactured hollow shaped micro components.

Automotive and aerospace industries consume a significant amount of Al alloys in structures and framing. There is, however, a significant challenge to join the alloy components by laser welding. A key problem is the presence of large amount of porosity in the welds. This research work aimed to understand factors affecting porosity formation in laser welding of AA6014 Al alloy and identification and verification of a suitable method for the porosity reduction and elimination. AC-170PX (AA6014) Al alloy was welded, for the first time, using a 5 kW disk laser in two different configurations: fillet edge and flange couch joints using a number of different filler wires. The experimental results showed that laser power (2-5 kW) and welding speed (20-50 mm/s) had a significant influence on porosity generation. Also, the introduction of a 0.2 mm gap between the sheets significantly reduced porosity for the fillet edge joint while it had a marginal effect for the flange couch joint. The effect of the chemical composition of the filler wire on the AA6014 weld quality was also evaluated for the first time by using different filler wires (AA3004, AA4043, AA4047 and AA5083) over a range of laser powers and welding speeds. The increase in Mg and Mn content in the filler wire's composition was found to reduce porosity in comparison with high silicon content filler wires. Nanosecond pulsed Nd:YAG laser cleaning was investigated as a surface preparation method for laser welding for AA6061, and its effect on porosity at various welding parameters was examined. The effect of laser cleaning on porosity reduction during laser welding using a filler wire has not been reported before. The surface characteristics before and after laser cleaning were analysed. The results showed that laser cleaning played an essential role in significantly reducing porosity in both the fillet edge and flange couch joints at different levels of power and laser welding speed. The developed surface preparation technology as a method for porosity reduction in laser welding has been successfully implemented in one of the largest UK/international car manufacturers. To study the laser cleaning process, a novel Smoothed particle hydrodynamics (SPH) meshless model has been implemented using a new 3-D multi-phase transient model. For the first time, a study was conducted to validate the temperature field distribution predicted in SPH method under nanosecond pulsed laser heating. The need for special surface treatment of the kernel truncation was also investigated. The proposed model accurately predicted the laser ablation depth and the crater shape and was validated using a significant number of experimental and numerical data reported in the literature. Moreover, a primitive laser welding model has been created to predict the material flow inside the welding pool. The research work has resulted in four publications in peer-reviewed journals. The research highlighted that future work should include the development of a more advanced SPH model for the prediction of porosity in laser welding and to fully describe the relationship between laser cleaning and porosity reduction in laser welding.

This thesis presents two models for optimizing and guiding the micro injection moulding process. The models are generated by the use of a mathematical procedure, an understanding of the process, and empirical data obtained from several sets of experiments. Micro injection moulding is a well-known process that is heavily used in the mass production of micro polymer parts. It is a very reliable process and apart from the initial investment required for manufacturing a mould, the process is very low cost. Furthermore, polymer developments have led to the process being suitable for the production of micro parts in equipment used in several industries such as medical, automotive, aerospace and sensing. Due to these important industrial applications, several quality criteria have been the subject of research in recent years. One of the main challenges in micro moulding is the modelling of the process in terms of polymer flow and accuracy. This is because current available models use PVT data (pressure, volume, temperature) that is used for modelling of conventional injection moulding. Furthermore, these models ignore several factors in micro moulding such as the high shear rates and 3D flow of the polymer melt. Moreover, modelling of the mechanical properties of the micro parts based on mathematical systems used for macro parts leads to large errors. This study proposes a new method for modelling the effect of process parameters on the dimensional accuracy and UTS (Ultimate tensile strength) of micro walls. This results in reduction of risk and cost, and optimization of the process. The “accuracy model” relates the dimensional error to four process parameters (polymer melt and mould temperature, and injection velocity and pressure), polymer characteristics (density, specific heat capacity and thermal conductivity) and a characteristic of the machine (plunger diameter). The “mechanical model” relates the part’s UTS to the same parameters as in the accuracy model. In order to develop the “accuracy model” an understanding of the effect of process parameters on dimensional accuracy and the polymers needs to be obtained. Several sets of experiments were conducted to investigate and establish this effect. Two polymers, Polyoxymethylene (POM) and Polypropylene (PP), were used to conduct the study. The results showed that the polymer melt temperature had the highest effect, followed by injection pressure, injection velocity and mould temperature. Amongst these, injection velocity had an adverse effect on dimensional accuracy. Further analysis was done to investigate whether the effect was consistent for several sets of the parameters. Results of the experiments showed that while the effect was not linear, the trends obtained earlier were correct. The same procedure was applied to investigate the effect of process parameters on the UTS of the micro walls. Polymer melt temperature had the highest level of influence, followed by injection velocity, injection pressure and mould temperature. Increase in all parameters resulted in reduction of the UTS, except for the mould temperature. Next, the two models were developed through a method called dimensional analysis. Several dimensionless expressions were developed to form a general relationship between the parameters and the quality criteria. Then, the obtained results and data were used to find the constants and the specific form of the functions. The overall models were validated by a fresh set of selected experiments using an original brass insert. The achieved trends and models were validated experimentally, using a different mould insert with a micro channel with a different dimension. While the values for the dimensional error and UTS were different, the trends obtained before were correct for the new insert. The same trend was observed with the models. Again, predictions for PP parts had better agreement with experimental data compared to those of POM. In addition, the amount of error for the steel insert was higher, due to different thermal conductivity of the insert material and surface roughness of the micro channels.

This project sought to design, implement and evaluate a process for the manufacture of porous, spherical salt beads, in order to enhance the reproducibility in mechanical properties of open cell aluminium foams made by a replication-based manufacturing technique. Porous beads were favoured in order to increase the dissolution rate of the salt from the preform, thereby making the manufacture of large foam parts practical. Salt beads were made by a novel method using fine NaCI powder, flour and water to make a paste that was subsequently disintegrated into large beads by mechanical stirring in oil. The NaCI paste viscosity was found to be important to the production of spherical beads and by varying the intensity of mechanical disintegration of the paste, control of the bead size was possible. The salt beads with sizes from 0.5 to 3 mm diameter were compacted into preforms and made into moulds for infiltration with molten pure aluminium by pressure- assisted investment casting. The heat treatment used to "cure" the plaster mould containing the preform was sufficient to remove the flour from the beads, sinter the preform and increase its strength. The effect of preform compaction conditions on the size, shape and volume fraction of porosity was quantified using a number of techniques, including mercury porosimetry, which was used to model the infiltration process. At the highest infiltration pressure 0.25 MPa (2.5 bar) the resulting foam densities were higher, but led to extensive penetration of molten aluminium into the porous beads, slowing down salt removal. In general, the compression strength increased with increasing foam density, and was highly reproducible, but where metal infiltration into the beads was extensive, the foam density increased but with little improvement in the compressive strength.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2011.
ENGLISH ABSTRACT: Vacuum assisted resin transfer moulding (VARTM) belongs to the category of resin infusion techniques that use lower than atmospheric pressure to infiltrate a reinforced cavity. This technique has various advantages; however, manufacturing costs can be relatively high due to more difficult shapes fabricated and a lack of knowledge regarding cost driving factors. The objective of this study was to develop a cost model for composite parts. Such a model allows the estimation of manufacturing costs of shapes of different geometries. Therefore, it provides a comparison to alternative manufacturing techniques, such as metal forming or composite spray lay-up and helps to avoid unnecessarily expensive design features. The proposal was made to split complex shaped composite parts into individual basic shapes, which are further investigated here. For the basic shapes, an experimental approach was used where the manufacturing times of each process step are measured and then statistically analysed. Infusion simulation software was used to obtain additional filling times to complete the design of experiments. This method allows the estimation of manufacturing times of composite parts with different geometries. The manufacturing times were validated to that of a complex shaped industrial part, with reasonable results. Finally, a flexible cost model was developed to compare different manufacturing techniques and to estimate the manufacturing costs.
AFRIKAANSE OPSOMMING: Vakuumgesteunde harsinspuitingsgietwerk (VARTM) behoort tot die kategorie harsinspuitingstegnieke wat laer-as-atmosferiese druk gebruik om ʼn versterkte holte binne te dring. Hierdie tegniek hou verskeie voordele in. Tog kan vervaardigingskoste betreklik hoog wees wanneer dit by ingewikkelder vorms en ʼn gebrek aan kennis met betrekking tot kostesnellers kom. Die doelwit van hierdie studie was om ʼn kostemodel vir saamgestelde onderdele te ontwikkel. Die model maak voorsiening vir die raming van die vervaardigingskoste vir verskillende afmetings. Sodoende bied dit ʼn vergelyking met alternatiewe tegnieke, en help voorkom onnodig duur ontwerpkenmerke. Daar is voorgestel dat dele met ingewikkelde vorms in individuele basiese vorms verdeel word, wat dan hier verder ondersoek word. Vir die basiese vorms word ʼn eksperimentele benadering gebruik waar die vervaardigingstye in elke prosesstap gemeet en statisties ontleed word. Voorts word inspuitingsimulasiesagteware gebruik om komplementêre inspuitingstye te bepaal ten einde die eksperimentele ontwerp te voltooi. Hierdie metode maak dit ook moontlik om die vervaardigingstye vir saamgestelde materiaal onderdele van verskillende afmetings te raam. Die vervaardigingstye word dan bevestig aan die hand van dié van ʼn kompleks gevormde industriële onderdeel, met redelike resultate. Uiteindelik word ʼn buigsame kostemodel ontwikkel om verskillende vervaardigingstegnieke te vergelyk en die vervaardigingskoste te raam.

Published Article
This paper is based on tests performed on die component specimens manufactured by EOS-DMLS (direct metal laser sintering) and LENS (laser engineered net shape) RP (rapid prototyping) technology platforms, as well as manufactured specimens machined out of preferred standard hot work steel DIN 1.2344. These specimens resemble typical components used in metal high pressure die casting tool sets. The specimens were subjected to a programme of cyclic immersion in molten aluminium alloy and cooling in water-based die release medium. The heat checking and soldering phenomena were analyzed through periodic inspections, monitoring crack formation and evidence of surface washout. At the end of the thermal tests, mechanical strength and hardness tests were performed to assess toughness and core resistance variations in relation to the initial conditions. Finally metallographic investigations were performed through optical microscopy on all the specimens considered. The outcomes of this research will be presented and used by the CSIR for further development and application of the assessed EOS-DMLS and LENS rapid prototyping technologies in rapid die manufacturing techniques and die design principles, including time and economic feasibility criteria to be applied when considering rapid die manufacture.

Hot cracking is a serious problem that encounters during welding of aluminium-magnesium alloys. In the present study, solidification and liquation type of hot cracks in weld metal and the heat-affected zones of 5086-H32 aluminium alloy were investigated by using Modified Varestraint Test (MVT) with TIG-AC and TIG-DC welding. With determining the size, type and number of cracks, a relation was established between welding line energy and strain on the hot crack formation. This information was used to determine the hot crack safe parameter ranges. The hot cracking tendency as a function of applied parameters were discussed in the frame of temperature fields around the moving heat source. Moreover, the characteristic hot crack locations on the 5086-H32 MVT specimens were generalized. The results of the study indicated that the increase in line energy and strain increased the hot cracking tendency of the specified aluminium alloy. In the low line energy range, the main hot cracking mechanism is the solidification cracking which could be overcome by the use of a suitable filler material. At high line energy range, due to the increased amount of interdendritic liquid, the amount of solidification cracking decreases by healing mechanism. However, because of the enlarged-temperature-field around the weld zone, fraction of HAZ cracking increases. The comparison between the hot cracking tendencies in low and high line energies indicates that the low line energy ranges with low augmented strains resulted in hot crack safer parameters.

Parallel-plate avalanche counters, PPACs, are commonly used to detect fission fragments. The PPAC detects them and mark (very accurately) the time of detection. Such measurements can be used to measure the neutron energy (via time-of-flight) to study neutron-induced fission.This project report provides a method that, together with the discussed improvements, allows the fabrication of good quality PPAC detectors. Several PPACs are manufactured and the electrodes are built from 0.9 µm thick mylar foils which are evaporated with a 40-80 nm thin layer of aluminum.The developed PPACs are characterized with well known radioactive Cf and Am sources (the source characterization also found in this report), and compared against each other. Additionally, the PPAC signal amplitude spectrum are found to follow theoretical expectations with regards to angular dependence, gas pressure and an applied electrode voltage.At a specific applied electrode voltage and range of gas pressures (3-9 mbar), the measured time resolutions are 2.24-1.38 ns. A trend is observed for finer time resolutions at higher gas pressures.
Parallel-plate avalanche counters, PPACs, används ofta för att detektera fissionsfragment. PPAC:en detekterar fragmenten med väldigt god tidsupplösning och således kan PPAC detektorer användas till att mäta neutron energier (mha. flygtidsmetoden), vilka uppmätts för att studera neutroninducerad fission.Det här projektet och den här rapporten beskriver en metod, med föreslagna förbättringar, som möjliggör tillverkning av PPAC detektorer av bra kvalitet. Under projektet har flera PPACs byggts med elektroder gjorda av 0.9 µm tunn mylar förångade med 40-80 nm aluminium. De tillverkade PPAC detektorerna är karaktäriserade med väl kända radioaktiva Cf- och Am-källor (dessa karaktäriseras även i den här rapporten). Detektorerna är sedan jämförda mot varandra och är funna att följa teoretiska förväntningar med avseende på vinkel-, gastryck- och pålagd elektrodspänningsberoende.Resultaten av projektet, som besvarar flera tidigare frågeställningar och bekräftar vissa antaganden, flyttar utsikten och förståelsen framåt för hur PPACs fungerar och vad forskarna kan uppnå med dem.

Metal foams have many attractive properties such as light weight, low relative density, energy absorption capability etc. One of the main advantages of metal foam is that the foam inherits several properties of the parent metal, at the same time, at a fraction of the weight. Metal foams are basically of two types; closed pore and open pore. In the open pore configuration the highly porous structure with large surface to volume ratio is attractive in thermal applications such as heat exchangers, small scale refrigeration, diesel exhaust cooling and heat sink for electronics. Large surface area to volume ratio of the heat transfer area is an important parameter in design of heat exchangers. Application of open cell metal foam as a heat exchanger involves production of the metal foam, cutting/drilling the metal foam to required dimensions and attaching it to a substrate or duct. Foams are cut by various methods such as by using circular saw, band saw, abrasive sawing wire or electrical discharge machining. Cutting or drilling operations plastically deform the struts and affect the surface roughness of the struts and hence, the contact area between the foam and the substrate. The foam and the substrate are then joined to get the final product. Various techniques are adopted to join the foam and substrate that includes, press fit, welding, soldering, brazing and use of epoxy adhesives or thermal glue. These methods either deform the foam plastically or involve a bonding material which involves an additional step in manufacturing and is generally necessary to reduce the thermal resistance at the interface. Every secondary step involved in machining the foam and joining it to substrate/duct add to the energy, time and cost of the component. Significant amount of materials wastage occurs during the production and machining steps of the metal foam. Bonding material used for attaching foam to the substrate makes the recycling of the heat exchangers difficult. In the present research work the above issues were rectified by introducing a novel method of fabricating the heat exchanger in a single step. This can be done by producing open cell foam, bonded to the substrate in a single step to get the ready to use heat exchanger. The uniqueness of the method/ process is that it provides an advantage of manufacturing heat exchangers consisting of open cell aluminium foam both inside and outside the aluminium duct/substrate. Here open cell metal foam is metallurgic ally bonded to the aluminium duct without producing any distortion in the aluminium duct. The present method avoids the secondary cutting and joining operations, hence reducing material and energy wastage. This heat exchanger does not need a bonding material at the foam duct interface which makes the product completely recyclable without even having to separate the aluminium foam and, many-at-times, the copper substrate. Further, in the present process no hazardous material is involved in the fabrication process of the heat exchanger and all the materials used for the foam production can be recycled. Another unique advantage of this process is that the foam can also be cast inside and outside the tube in a single step. This helps increase the heat transfer area per unit volume inside the tube increasing the effectiveness significantly. First, an attempt was made to cast aluminium foam over a Cu substrate. Spheres made of Plaster of Paris (PoP) were used as space holders to create pores in the foam. First, a dough of PoP was prepared by mixing sufficient amount of water with the powder of PoP. Small pieces of PoP were taken from the dough and were rolled by hands to prepare spherical balls. Next, a casting setup was made where a die made of stainless steel was placed in a crucible whose bottom was filled with sand. A tube/duct made of copper was placed at the centre of the die and PoP balls were dropped around the duct. This setup was then placed in a furnace and was preheated to remove all the moisture from the PoP. Molten aluminium at around 700 °C was poured into the preheated die. After solidification, the die was opened and cast was allowed to cool in ambient air. PoP balls were removed by using a sharp needle and by dipping the casting in acetic acid. After removal of PoP from the cast, interconnected holes/cavities formed in the place of space holders/PoP balls, forming pores in the foam. There are some limitations of this method such as removal of PoP was tedious and needed chemicals that need to be discarded, PoP cannot be recycled and creates waste, small amount of moisture present in PoP balls can cause an explosion. The bonding between aluminium foam and Cu substrate obtained was not good, giving rise to thermal contact resistance. Due to the above limitations further implementation of this process using PoP was not explored further. There was a need of space holder material which can withstand the temperature of molten Al and also can be removed easily from the cast without any use of chemicals. Obtaining metallic bonding between foam and Cu substrate was difficult due to the corrosion layer formation at the interface of Al and Cu substrate due to preheating. If preheating was not carried out full penetration of the molten aluminium did not take place in the space available in between the spheres. Therefore, it was decided to cast Al foam over Al substrate. The main challenge and difficulty was to cast open cell Al foam inside and outside the tube/duct made of the same material (Al) without distorting the tube/duct as well as achieving consistent metallic bonding between the two. This has been successfully done by gravity casting method a single step manufactured and ready to use open cell Al foam heat exchanger were fabricated. A casting setup was prepared, which consisted of a commercially pure aluminium tube placed in the middle of a stainless steel split die. The gap between the tube and die was filled with the salt spheres. An uncommon and new approach was adopted to produce NaCl salt spheres. NaCl salt balls (spherical and ovoid) of different diameters were processed by casting route. The casting step of NaCl is necessary as the moisture present in NaCl can be completely removed during the melting of NaCl. NaCl was chosen as it had a melting point higher than aluminium. The casting setup was placed in a furnace and was preheated to various temperatures up to 550 °C. Commercially pure aluminium was melted separately in a crucible and was poured into the steel die at 700oC. The liquid metal flows through the die and fills the cavities between the salt balls. The die was opened immediately after solidification of molten Al and cast was allowed to cool in ambient air. The salt (NaCl), which was still solid, was dissolved in water to get the foam structure. With proper control of the preheat temperature and temperature of liquid aluminium no distortion of the aluminium duct was observed throughout the length of the heat exchanger. Consistent and complete fusion/ metallic bonding was observed at the interface of Al foam and Al substrate/duct. Several heat exchangers with different porosity and pore geometry with the aluminium foam cast outside the tube and both inside and outside of the tube were fabricated. The beauty of the designed method is that it is simple and cost effective and eliminates the major issue of thermal contact resistance since the foam and the duct are made of the same material and are bonded in the liquid state leaving no interface between the foam and the duct. Further, foam can also be cast inside the duct in the same step while casting the foam outside the tube, giving an integral heat exchanger which has higher heat transfer surface area to volume ratio inside and outside the duct. This is expected to further improve the efficiency and effectiveness of the heat exchanger An added advantage of this method is that the heat exchanger can be recycled easily in a single step re-melting route. Further, the heat exchanger does not use any hazardous material during manufacture that needs attention during recycling. After the production and fabrication of the heat exchangers, the thermal performance or effectiveness of the heat exchangers was assessed, to evaluate its usefulness and suitability for heat transfer application. An experimental test setup was fabricated in the laboratory to perform the heat transfer tests. The experimental test setup consists of the following major components;1) A test chamber whose function was to insulate the heat exchangers from the surroundings and to avoid any heat loss to the surroundings, 2) An air blower used to supply cold fluid (air) to the test chamber, 3) A constant temperature bath was used to supply the hot fluid, which was water in this case, in the duct of the heat exchanger, 4) A rotameter was used to measure the volumetric flow rate of the cold fluid and 5) A pressure gauge having the pressure measurement range between 1 mbar to 160 mbar to measure the pressure drop across the test chamber. K-type chromel – alumel thermocouples having temperature measurement range between -270 °C to 1,260 °C were used to measure the temperature of hot and cold fluids during the experiments. By aid of the data logger system and computer, temperature readings were recorded during the tests and were used further for the heat transfer calculations. For testing the aluminium foam heat exchangers was placed in the insulated test chamber. Hot water was supplied inside the duct of heat exchanger whereas air at room temperature was supplied around the foams at varying flow rates during the tests. During the tests, temperature readings were taken at steady state condition. NTU-Effectiveness method was used to evaluate the thermal performance of heat exchangers. Overall results obtained by this experimental study are as follows • As the inlet temperature difference between hot and the cold fluids increases the heat transfer rate and the effectiveness of the heat exchangers also increases. • At a constant flow rate of hot fluid, heat exchangers exhibits significantly better thermal performance at lower flow rate of cold fluid compared to higher flow rate. As the flow rate of cold fluid increases, the velocity of the fluid increases and consequently, reduces the optimum interaction time between hot and the cold fluids required for the efficient heat transfer. • At a constant and low flow rate of cold fluid the effectiveness of the heat exchanger increases as the porosity of the foam increases. But when the flow rate of cold fluid was increased further after a certain limit, the effectiveness value of the heat exchanger decreases. • Heat exchanger consisting of foam of higher porosity exhibits higher effective. • Heat exchanger having foam inside and outside of the duct/tube exhibits significantly higher effectiveness compared to Al duct, Cu duct and other heat exchanger tested. • At a higher flow rate of the cold fluid, the heat exchangers consisting of foams of higher porosity, experience more drop in effectiveness compared to the heat exchanger having foams of low porosity. • Pressure drop across the length of the foam/fin increases as the volumetric flow rate of the cold fluid (m3/s) increases. • Surface area per unit volume and effectiveness values for bare Al tube is very low compared to Al foam heat exchangers resulting in the bare Al tube exhibiting much lower effectiveness compared to heat exchanger made of Al foam. • For a certain flow rate of fluids, the effectiveness of the heat exchanger increases up to a certain thickness of the Al foam. • Regardless of the thickness of the foam, the effectiveness of the heat exchangers is low at higher flow rate of cold fluid compared to lower flow rate. • These foam based heat exchanger had a much higher effectiveness when compared to that of other heat exchangers, data of which were got from literature. The present experimental study concludes that fuse bonding open cell aluminium foam over an Al duct or Al substrate can improve the thermal performance of the heat exchanger significantly. The thesis includes five chapters. Chapter 1 gives a detailed introduction about the metal foam, heat exchangers, thermal contact resistance and its effect on the heat transfer rate has been explained. This chapter also includes the overall aim and motivation for the research work. Chapter 2 covers the literature available on production methods of metal foam and its limitations has been listed out. And conventional methods of manufacturing open cell metal foam heat exchangers and its disadvantages have been explained in detailed. Chapter 3 covers in detail the novel method of production and fabrication of open cell metal foam heat exchangers. Chapter 4 includes an experimental study, where thermal performance of heat exchangers has been assessed through heat transfer experiments. Chapter 5 is the conclusions and future works.

碩士
國立臺北科技大學
機電整合研究所
102
In recent years, with the development and application of additive manufacturing technology. Such as aerospace, automotive, medical and dental, etc. Therefore, the stability of the sample which is product by additive manufacturing is more important. There are not testing standard system and specification of strength value for additive manufacturing product in far. Strength value of materials and elastic modulus has a direct relationship. Therefore, this article will use laser ultrasound technology to detect additive manufacturing products for non-destructive testing. By exploring elastic modulus values, and understand the impact of the manufacturing process for the product in material hardening process. In this study, using laser ultrasound technique to detect the additive manufacturing parts. Laser as excitation and interferometer as receiver to do linear scan. Obtained the time-domain signal after linear scan, and stacked into B-sacn image. B-sacn image to do fast fourier transform, and obtain the experiment dispersion curve. Obtained the quantitative elastic modulus value by particle swarm optimization. Validate the laser ultrasound technique through tensile test. Using recursive asymptotic stiffness matrix method to simulate that guided wave propagation in the multilayer structure.

碩士
雲林科技大學
資訊管理系碩士班
98
In order to cut down cost and improve equipment throughput, manufacturing is more and more automatically in operation equipment. How to provide more effective use in equipment becomes a very import issue in manufacturing. It also hopes to find out the most important key related factors of throughput. Therefore, this paper proposed a procedure to extract the rule of key performance indicator (KPI) by rough set theory in automobile industry This paper practically collects manufacturing supplier dataset in auto parts industry. The dataset includes production records, and there are 18 attributes such as production scheduling, scheduled downtime, process, etc. For comparison, decision tree, naive bayesian, and multi-layer perceiving are utilized to compare with the proposed procedure in classification accuracy. The results show that the correct rate of rough set theory is not only superior to decision trees, naive bayesian, and multi-layer perceiving, and the proposed procedure can be easy to understand and produce fewer rules. In managerial implication, the results can generate predictive model, and classifiable rule which can help manufacturing to find out key related factors in equipment throughput and use the rules generated as a capacity planning assessment.

碩士
嘉南藥理科技大學
產業安全衛生與防災研究所
97
This research organizes the case study object to the status of occupational safety and health in vehicle parts and accessories manufacturers, affiliated companies, satellite factories and sizable Taiwan public companies and case study cognition Questionnaire to the problem analysis of safety and health on the companies. The research shows: (1) Since the company of the case study has had their own safety and health department and management system, also already passed several items of quality excellent audit by Council of Labor Affairs, but the injuries during the work and defects found by an authorized labor inspector were not decreased and reduced obviously due to meeting with a bottleneck of improvement policy. (2) The survey of safety and health status shows that most of vehicle parts and accessories manufacture and sizable factories (public companies) have conformed to the regulations under the frequent inspection by the authorized labor inspector, yet needs to enhance the performance of safety and health. (3) In the majority of small vehicle parts and accessories manufacturers having employees fewer then 30 members, they have not established the system of safety and health. (4) Because of the assistance and support from the parent company, those small affiliated companies of the case study object have conformed to the request of safety and health regulations. (5) According the safety cognition survey, it is of the above middle grade on the whole. The intersection analysis shows the quality strict controlled departments, male employees, younger staffs and senior staffs are with lower safety cognition. Key words: vehicle parts and accessories manufacture, safety and health.

碩士
國立高雄科技大學
模具工程系
107
In recent years, the global plastics industry has ignited a lightweight cyclone. Therefore, the application of fiber-reinforced plastic composite materials with light weight, high strength and high rigidity has been gradually popularized and valued. At present, various types of plastic composite products are produced. Two of the most popular processes for manufacturing plastic composite products are injection molding and thermoforming. However, the addition of long fiber reinforcing material in the injection machine is often caused by the rotation and twisting of the screw. The fiber length is shortened, resulting in a fiber reinforcement effect that is less than expected. Therefore, most of the plastic composite parts with continuous long fibers are produced by thermoforming. The process and mold design of this method are relatively simple, and the structure of long fibers is not arbitrarily cut, but it is not suitable for shape complex and sophisticated products. In the light of this, this research proposes a hybrid molding technology of thermoforming and injection molding, and hopes to successfully produce high-performance composite parts with both long and short fiber structures through proper mold design and process integration. In this study, the standard tensile test, impact test, three-point bending test are used for determining the mechanical properties of the composite parts. An experimental study, based on the Taguchi orthogonal array design, was conducted to characterize the effect of different processing parameters on the hybrid molding of composite parts, so that steps can be taken to optimize the molding process.

碩士
萬能科技大學
資訊管理研究所在職專班
102
Taiwan’s manufacturing was prosperous in 80s and plays an important role in Taiwan’s economy until now. Automobile parts manufacturing is one of the important manufacturing in Taiwan’s economy, but there’re still lots of parts industry managed by artificial billing methods till now and usually caused materials account incompatible with stock. The modes of enterprises operation also face the adjustment of transition due to the international competition in the meantime. To implement ERP will be a feasible approach to be a complete solution for solving the management and transition problems. However, implementing ERP is not always successful. Therefore through this research to find out the CSF of implementation and assist enterprises to execute the ERP implementation then reduce the risk of failure. In this case study, 25 CSF of the ERP implementation are brought up after interviewing with executives management of company. Further to use the Data Mining association rules to find out the meaningful combination of CSF and proceed to analyze and study that aims to find the combination of CSF. And then brings up the suitable CSF to business which is based on the results of data mining. There are 5 items as follows: 1.Leader’s support and leadership. 2.Leader’s listen internal demand timely. 3.Requirements feedback to employees, the employees has a higher willingness to execute the ERP system. 4.ERP implementation team need to arrange the training and education for employees, so that employees can understand how to operate the system as soon as possible. 5.During the implement process, employees should communicate and condone with each other to ease the tense situation and atmosphere.

Student Number: 9400670E School of Chemical and Metallurgical Engineering Faculty of Engineering and Built Environment
The selection of a particular steel grade for an application is extremely important to ensure that the final components have a long serviceable life. The chemical compositions of the steels are critical, and minor changes in chemistry can make substantial differences. Aluminium and vanadium are used in heat treatable steels as grain refining agents. These elements affect the properties of the steels. Two steels with identical chemical composition except for the aluminium and vanadium additions were comparatively tested to determine the better steel for a particular automotive coil spring. The tests included mechanical testing and on site fatigue testing. Fatigue resistance is extremely important especially for automotive coil springs. The mechanical properties revealed superior tensile strength in the vanadium grain refined spring steel while the aluminium grain refined spring steel had superior ductility and fatigue resistance.

碩士
銘傳大學
企業管理學系
106
As the social issues of environmental maintenance and society relationship are given more attention, the government encourages or regulates companies to perform corporate social responsibility (CSR). Meanwhile, many firms takes CSR either as part of operation activities or as part of core strategies for sustainable development. Furthermore, Taiwan Stock Exchange launched the TWSE Corporate Governance 100 Index (CG 100) in 2015 with the goal of encouraging corporations to comply with good governance practices according to the corporate governance evaluation criteria. Through the sample from the listed manufacture of computers and peripheral equipment (MCPE) and the manufacture of other electronic parts and components (MOEPC), this study investigates the relationship between CSR and operation efficiency, and analyzes the impact factors on efficiency. There are 75 firms in the sample with the period during 2013-2016. The methodology and testing methods include data envelopment analysis (DEA), Person correlation coefficients, Tobit regression model, t-test, F-test, and VIF analysis. The result suggests that the four variables of capital size, ratio of stockholding of directors and supervisors, dummy of MCPE versus MOEPC, and dummy of eligibility into CG100 index constituents are the influential factors on efficiency. In addition, the significant and positive value on the dummy of eligibility into CG100 index constituents indicates that the more the firms perform CSR, the more the operation efficiency.