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Norton, Seth Jason. "Ferrous friction stir weld physical simulation." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1143252009.
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Adapa, Sujatha. "Evaluation of friction stir weld samples using digital image correlation /." Available to subscribers only, 2006. http://proquest.umi.com/pqdweb?did=1136092291&sid=5&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Thesis (M.S.)--Southern Illinois University Carbondale, 2006."Department of Mechanical Engineering and Energy Processes." Includes bibliographical references (leaves 70-74). Also available online.
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Pew, Jefferson W. "A torque-based weld power model for friction stir welding /." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1649.pdf.
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Sanders, Johnny Ray. "Understanding the material flow path of the friction stir weld process." Master's thesis, Mississippi State : Mississippi State University, 2005. http://library.msstate.edu/etd/show.asp?etd=etd-11102005-142957.
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Champagne, Matthew. "Investigation of 2195 and 2219 Post Weld Heat Treatments for Additive Friction Stir Lap Welds." ScholarWorks@UNO, 2017. https://scholarworks.uno.edu/td/2402.
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To evaluate potential uses for friction stir welding in additive manufacturing, two separate parts were fabricated, one of 2195-T84 and the other 2219-T87, utilizing fixed pin techniques and additive lap welds. The parts were cut into samples, artificially aged and subjected to Rockwell hardness (HRB), Vickers hardness, micrographic photography, and metallographic imaging on both pre- and post- heat treatment. Additionally, tensile testing was performed on the heat-treated samples. A comparisons of test results showed a minimal increase in the yield strength of the 2195-T84 samples compared to as-welded tensile results obtained from a previous project. The ultimate tensile strength was reduced by approximately 16%. Further testing will be required to determine the nature of this reduction. No previous results were available for the as-welded 2219-T87, but UTS of the artificially aged samples was approximately 91% that of the parent material.
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Stahl, Aaron L. "Experimental Measurements of Longitudinal Load Distributions on Friction Stir Weld Pin Tools." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd1018.pdf.
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Georgeou, Zacharias. "Analysis of material flow around a retractable pin in a friction stir weld." Thesis, Port Elizabeth Technikon, 2003. http://hdl.handle.net/10948/196.
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Friction StirWelding (FSW) has been researched for a number of years since its inception in 1991. The work thus far has been based on understanding the material and thermal flow using the standard fixed pin tool. The keyhole resulting during tool extraction in a FSW weld, is a disadvantage and a current limiting factor. Eliminating this effect from a weld using a movable pin tools would make FSW more commercially viable. This dissertation focuses on the design of a novel retractable pin tool, and highlights the problems encountered during the welding of Aluminum plates, Al2024 and Al5083. Previously studied techniques of material and thermal flow were used, to investigate the effect of the tool during extraction in a FSW weld. A prototype retractable tool was designed using parametric and axiomatic design theory, and implementing a pneumatic muscle actuation system. The resulting problems in the calibration of the retractable pin tool and the resulting welds are presented, these results confirming previous studies. The movable pin produced discrepancies the heat generation around the shoulder during a FSW weld. The failure of this tool to produce a reasonable weld showed that previous ideas into the workings of a retractable pin tool requires further investigation, furthermore a fresh approach to the interpretation and understanding of the FSW weld process needs consideration.
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Sun, Tianzhu. "Residual stress development in AA7050 stationary shoulder friction stir welds." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/residual-stress-development-in-aa7050-stationary-shoulder-friction-stir-welds(9c4066c2-f3cf-4a3d-bfd0-3f6842de1251).html.
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Stationary shoulder friction stir welding (SSFSW) is a recently developed variant of conventional friction stir welding (FSW). Recent studies have shown that SSFSW can join high strength aluminum alloys with improved mechanical strength and reduced distortion as a result of a narrower and more uniform thermal profile. However, a lack of understanding on the residual stress development in the SSFSW process makes it difficult to assess the structural integrity and delays a widespread application of this technique to industry. This dissertation reports the first systematic investigation into the development of residual stress induced by the SSFSW process and comparison between SSFSW and FSW techniques. Welding residual stresses were experimentally assessed with both the contour method and neutron diffraction. The weld microstructure and hardness distributions were characterized and used to understand the formation of residual stresses during the welding process. The results have shown that for both FSW and SSFSW processes, the residual stresses distribute in the form of âMâ shaped profile while the magnitude and size of tensile residual stress zone were effectively reduced (by 25%) in the SSFSW process, even when input welding power was identical. Other improvements seen in the SSFSW process include a reduction in the heat affected zone width, an increase in the minimum hardness and a more uniform through-thickness microstructure and hardness. The dominating welding process parameter affecting the welding residual stress was travel speed as compared to rotation speed and tool downforce. With a 90 degree shaped shoulder, SSFSW has been shown to produce defect-free T-sections by dual fillet welds. For these components, an asymmetrical distribution of microstructure, hardness and residual stresses were found as a consequence of the thermal effects induced by second weld on the first weld. The material softening caused by the first weld provides the potential of utilizing a lower heat input on the subsequent pass so as to optimize the welding parameters.
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Crook, Nolan Tracy. "Control of Post-Weld Fracture Toughness in Friction Stir Processed X-80 HSLA Steel." BYU ScholarsArchive, 2021. https://scholarsarchive.byu.edu/etd/9162.
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The present study investigates the fracture toughness of FSW X-80 HSLA steel welds. Weld cooling rate and peak temperature were varied among welds; indirectly manipulated through FSW travel speed, rpm, and weld preheat. Fracture toughness was tested according to ASTM 1820 standard along the weld centerline using surface-notched SEB specimen cooled to -40 °C. This study resulted in a reliable, repeatable process for generating friction stir welds with CTOD’s consistently above that of the original base metal. CTOD and microstructure of friction stir welds can be selected by controlling weld cooling rate and peak temperature. Material properties and microstructure similar to the original base metal can be recreated throughout the weld stir zone. CTOD of FSW X80 has a strong inverse linear correlation with post-weld cooling rate.
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McBride, Stanford Wayne. "A Numerical Model of the Friction Stir Plunge." BYU ScholarsArchive, 2009. https://scholarsarchive.byu.edu/etd/1772.
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A Lagrangian finite-element model of the plunge phase of the friction stir welding process was developed to better understand the plunge. The effects of both modeling and experimental parameters were explored. Experimental friction stir plunges were made in AA 7075-T6 at a plunge rate of 0.724 mm/s with spindle speeds ranging from 400 to 800 rpm. Comparable plunges were modeled in Forge2005. Various simulation parameters were explored to assess the effect on temperature prediction. These included the heat transfer coefficient between the tool and workpiece (from 0 to 2000 W/m-K), mesh size (node counts from 1,200 to 8,000), and material model (five different constitutive relationships). Simulated and measured workpiece temperatures were compared to evaluate model quality. As spindle speed increases, there is a statistically significant increase in measured temperature. However, over the range of spindle speeds studied, this difference is only about 10% of the measured temperature increase. Both the model and the simulation show a similar influence of spindle speed on temperature. The tool-workpiece heat transfer coefficient has a minor influence (<25% temperature change) on simulated peak temperature. Mesh size has a moderate influence (<40% temperature change) on simulated peak temperature, but a mesh size of 3000 nodes is sufficient. The material model has a high influence (>60% temperature change) on simulated peak temperature. Overall, the simulated temperature rise error was reduced from 300% to 50%. It is believed that this can be best improved in the future by developing improved material models.
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Dickson, Steven B. "An Investigation of Friction Stir Welding Parameter Effects on Post Weld Mechanical Properties in 7075 AA." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5672.
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The effects of weld temperature, travel speed, and backing plate thermal diffusivity on themechanical properties of a weld have been studied. A face centered cubic experiment of designwas completed in which the response variables were yield strength, minimum hardness in the HAZ, and charpy impact toughness. Three models were created from the data gathered usinga stepwise regression in order to see the effects of each parameter. For the yield strength andminimum hardness it was found that only travel speed and backing plate thermal diffusivities werestatistically significant to the properties. The charpy impact toughness saw that all three parameterswere statistically significant to its value. In all three models the travel speed had the greatest affecton the material properties.
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Pearl, David Lee. "A Novel Characterization of Friction Stir Welds Created Using Active Temperature Control." Miami University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=miami1618585976565749.
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Posada, Maria. "Comparison of 3-D Friction Stir Welding Viscoplastic Finite Element Model with Weld Data and Physically-Simulated Data." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3494.
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Models (both physical and numerical) of the friction stir (FS) welding process are used to develop a greater understanding of the influence of independent process parameters on dependent process output variables, such as torque, power, specific weld energy, peak temperature, cooling rates and various metallurgical factors (e.g., grain size and precipitates). An understanding of how the independent process parameters influence output variables and ultimately their effect on resultant properties (e.g., strength, hardness, etc..) is desirable. Most models developed have been validated primarily for aluminum alloys with relatively small amounts of experimental data. Fewer models have been validated for steels or stainless steels, particularly since steels and stainless steels have proven more challenging to friction stir than aluminum alloys. The Gleeble system is also a powerful tool with the capability to perform thermomechanical simulations in a known and controlled environment and provide physical representation of resultant microstructure and hardness values. The coupling of experimental data and physical simulated data can be extremely useful in assessing the capabilities of friction stir numerical process models. The overall approach is to evaluate Isaiah an existing three-dimensional finite element code developed at Cornell University by comparing against experimental and physically-simulated data to determine how well the code output relates to real FS data over a range of nine processing conditions. Physical simulations replicating select thermomechanical streamline histories were conducted to provide a physical representation of resultant metallurgy and hardness. Isaiah shows promise in predicting qualitative trends over a limited range of parameters and is not recommended for use as a predictive tool but rather a complimentary tool, Once properly calibrated, the Isaiah code can be a powerful tool to gain insight into the process, strength evolution during the process and coupled with a texture evolution model may also provide insight into microstructural and texture evolution over a range for which it is calibrated.
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Widener, Christian Aragon Talia George E. "Evaluation of post-weld heat treatments for corrosion protection in friction stir welded 2024 and 7075 aluminum alloys." Diss., Click here for available full-text of this thesis, 2005. http://library.wichita.edu/digitallibrary/etd/2005/d004.pdf.
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Thesis (Ph.D.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering."December 2005." Title from PDF title page (viewed on February 8, 2007). Thesis adviser: George Talia. Includes bibliographic references leaves 192-203).
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Nielsen, Bryce K. "Developing Response Surfaces Based on Tool Geometry for a Convex Scrolled Shoulder Step Spiral (CS4) Friction Stir Processing Tool Used to Weld AL 7075." BYU ScholarsArchive, 2009. https://scholarsarchive.byu.edu/etd/1782.
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The purpose of this study is to develop a series of response surfaces that define critical outcomes for welding in Al 7075 based on the tool geometry of a convex scrolled shoulder step spiral (CS4) friction stir processing tool. These response surfaces will be used to find critical minimums in forces which will decrease the required power input for the process. A comprehensive parameterization of the tool geometry is defined in this paper. A pilot study was performed to determine the feasibility of varying certain geometric features. Then a screening experiment eliminated those geometric features that were not as significant in determining the response surfaces. A central composite design with the five most important geometric features was used in order to develop response surfaces for nine different response variables. The nine response variables are the longitudinal, lateral and axial forces; the tool temperature, the spindle torque, the amount of flash, the presence of defects, the surface roughness and the ledge size. By using standard regression techniques, response surface equations were developed that will allow the user to optimize tool geometries based on the desired response variables. The five geometric features, the process parameters and several of their interactions were found to be highly significant in the response surfaces.
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Brzostek, Robson Cristiano [Verfasser], and Norbert [Akademischer Betreuer] Huber. "Damage tolerance of refill friction stir spot weld application for the aircraft industry / Robson Cristiano Brzostek ; Betreuer: Norbert Huber." Hamburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2019. http://d-nb.info/1189729784/34.
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Stringham, Bryan Jay. "Non-Dimensional Modeling of the Effects of Weld Parameters on Peak Temperature and Cooling Rate in Friction Stir Welding." BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6710.
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Methods for predicting weld properties based on welding parameters are needed in friction stir welding (FSW). FSW is a joining process in which the resulting properties depend on the thermal cycle of the weld. Buckingham's Pi theorem and heat transfer analysis was used to identify dimensionless parameters relevant to the FSW process. Experimental data from Al 7075 and HSLA-65 on five different backing plate materials and a wide range of travel speeds and weld powers was used to create a dimensionless, empirical model relating critical weld parameters to the peak temperature rise and cooling rate of the weld. The models created have R-squared values greater than 0.99 for both dimensionless peak temperature rise and cooling rate correlations. The model can be used to identify weld parameters needed to produce a desired peak temperature rise or cooling rate. The model can also be used to explore the relative effects of welding parameters on the weld thermal response.
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Danka, Labus Zlatanović. "Friction stir spot welding of ultrathin sheets made of aluminium – magnesium alloy." Phd thesis, Univerzitet u Novom Sadu, Fakultet tehničkih nauka u Novom Sadu, 2020. https://www.cris.uns.ac.rs/record.jsf?recordId=114672&source=NDLTD&language=en.
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Within the framework of presented PhD, friction stir spot welding (FSSW) ofmultiple ultrathin sheets of AA 5754 – H111 (AlMg3) alloy 0.3 mm thick, wasstudied. The influence of tool geometry and process parameters such as rotationalspeed and axial load have been analysed using numerous techniques. It has beenunderstood that during the welding at low rotational speeds weld zone undergoesstrain hardening, while at high rotational speeds weld zone undergoes thermalsoftening. It was observed that during FSSW at low rotational speeds a complexlayer at weld interface is present, which causes delamination when welded samplesare subjected to load.У оквиру ове докторске дисертације испитивано је тачкасто заваривање трењем са мешањем ултратанких лимова дебљине 0.3 mm од легуре АА 5754 – H111 (AlMg3). Утицај геометрије алата и параметара као што су угаона брзина и аксијално оптерећење су детаљно анализирани уз помоћ бројних техника. Установљено је да приликом заваривања ниским угаоним брзинама долази до деформационог ојачавања, док на високим угаоним брзинама долази до термичког омекшавања зоне завара. Код узорка завареног са најмањим бројем обртаја долази до формирања комплексног слоја на међуконтактној површини који изазива деламинацију приликом испитивања механичких особина.
U okviru ove doktorske disertacije ispitivano je tačkasto zavarivanje trenjem sa mešanjem ultratankih limova debljine 0.3 mm od legure AA 5754 – H111 (AlMg3). Uticaj geometrije alata i parametara kao što su ugaona brzina i aksijalno opterećenje su detaljno analizirani uz pomoć brojnih tehnika. Ustanovljeno je da prilikom zavarivanja niskim ugaonim brzinama dolazi do deformacionog ojačavanja, dok na visokim ugaonim brzinama dolazi do termičkog omekšavanja zone zavara. Kod uzorka zavarenog sa najmanjim brojem obrtaja dolazi do formiranja kompleksnog sloja na međukontaktnoj površini koji izaziva delaminaciju prilikom ispitivanja mehaničkih osobina.
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Clark, Tad Dee. "An Analysis of Microstructure and Corrosion Resistance in Underwater Friction Stir Welded 304L Stainless Steel." Diss., BYU ScholarsArchive, 2005. http://contentdm.lib.byu.edu/ETD/image/etd872.pdf.
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Smith, Travis Lee. "The Effect of Tool Rotation Speed and Clamping on Deformation in Friction Stir Welded 6061-T6511 Aluminum Extrusions." ScholarWorks@UNO, 2011. http://scholarworks.uno.edu/td/350.
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Friction Stir Welding (FSW) was used to perform Bead on Plate (BOP) welds on 6061-T6511 aluminum extrusions. Using a DOE approach, tool rotation speed, clamp spacing, and clamping force were altered to ascertain their effects on distortion in the welded panels. Mechanical forces were monitored during the weld process. Both linear and out of plane distortion were measured on the welded extrusions. The Vickers hardness of the weld nugget was measured. The effect of each parameter on weld distortion was discovered and the mechanism of this link was suggested.
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Baratzadeh, Farzad. "Friction stir weld development and dynamic crash testing of bumper-beam / crash-box assemblies made from AA66082-T6 and AA6063-T6 extrusions." Diss., Wichita State University, 2013. http://hdl.handle.net/10057/10607.
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Advancements in friction stir welding (FSW) have enabled the development and testing of a lightweight automotive bumper-beam/crash-box assembly. Previously, a test fixture to dynamically (crash) test the functionality of advanced bumper assemblies fabricated by FSW was developed. This FSW development work included microstructural examination and static mechanical testing. Results from coupon-level development were compared against results from component-level testing of prototype articles using micrographs and an advanced electronic (signal/frequency analysis) non-destructive evaluation (e-NDE) technique in order to detect weld anomalies primarily in the form of voids. Due to the geometry of the welded part joint, conventional mechanical testing methods (tensile and peel test) were not applicable. Therefore, a wedge test was devised to test the relative toughness of the FSW joint. From recorded data, toughness plots were calculated to select the best joint from three weld tools, each having the same basic threaded probe and WiperTM shoulder designs, and differing only in probe features. In addition to the basic tool configuration, one tool had a set of partial CounterFlowTM grooves, and the other had a set of partial straight flats. Each also had a special geometrical feature added to the tip of the tool probe, referred to as a concentrating tip, to improve metal flow at the end of the probe in order to inhibit void formation. Traditional sled testing for low-speed bumper requirements was performed at the General Motors (GM) Research and Development (R&D) facility in Detroit, Michigan, and drop tower tests were performed using an FSW test fixture at the National Institute for Aviation Research (NIAR) at Wichita State University (WSU). These dynamic tests were performed on bumpers using both FSW and gas metal arc welding (GMAW). Finite element analysis (FEA) was used to compare the predicted damage to the actual damage sustained by the bumpers fabricated by GMAW and FSW, respectively.Thesis (Ph.D.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering
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Nielsen, Bryce. "Developing response surfaces based on tool geometry for a convex scrolled shoulder step spiral (CS4) friction stir processing tool used to weld Al 7075 /." Diss., CLICK HERE for online access, 2009. http://contentdm.lib.byu.edu/ETD/image/etd2813.pdf.
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Ditzel, Peter J. "Microstructure/ Property Relationships in Aluminum Friction Stir Welds." The Ohio State University, 1997. http://rave.ohiolink.edu/etdc/view?acc_num=osu1381145015.
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Zhang, Cheng. "Robotic 3D friction stir welding : T-butt joint." Thesis, Högskolan Väst, Avd för automationssystem, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-8250.
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This Master Thesis was performed in terms of robotic three dimensional friction stir welding with T-butt joint. Friction stir welding (FSW) is a solid state welding method that achieves the weld temperature by friction of a rotating non-consumable tool with the workpiece. Science and technology fast developing requires for higher seam quality and more complex welding joint geometry like 3D welds. In order to acquire high productivity, capacity and flexibility with acceptable cost, robotic FSW solution have been proposed. Instead of the standard FSW machine, using a robot to perform complicated welds such as, three-dimensional. In this report, a solution for weld a 3D T-butt joint, which located in an aluminium cylinder with 1.5 mm thickness using a robot, was developed. Moreover, two new paths were investigated in order to avoid the use of two welds to perform this type of joint. The paths were tested on 2D and on 3D (with a 5050 curvature radius) geometries. Both paths had good results. What is more, the parameter developing methods of FSW process, which is composed of necessary parameter setting, positional compensation was introduced. Specially,the study demonstrates how complicate geometry can be welded using a robot. Also,it shows that TWT temperature control is able to acquire high quality 3D welds. In addition, an analysis of the 2D welding and 3D welding was performed, which exposed that, keeping exactly the same welding conditions, higher lateral forces on the tool were found during 3D welding. Basis on the special case in this paper, when the tool goes like "climbing" the sample, the suffering force of tool decreasing with increasing the height(Z position); nevertheless, when the tool goes like "downhill", the suffering force of tool decreasing with decreasing the height (Z position). What is more, in 2D weld, increasing the downforce (Fz) results increasing the lateral forces which can be Fx and/or Fy. Finally, the future works suggestions were presented in terms of (1) performing the new paths into a real cylinder, (2) performing tensile test on the paths and comparing it with conventional path which weld twice, (3) researching how the downforce (Fz) influence the Fx and Fy during welding of different 3D geometries, (4) how the cooling rate of backing bar influence the seam quality when it is use the same welding parameters and (5) the effect of performing welds in the same welding temperature achieved with different combination of the tool rotational speed and downforce on the material properties
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Padovani, Cristiano. "Corrosion protection of friction stir welds in aerospace aluminium alloys." Thesis, University of Birmingham, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.446319.
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Attallah, Moataz. "Microstructure property development in friction stir welds of aluminim based alloys." Thesis, University of Birmingham, 2008. http://etheses.bham.ac.uk//id/eprint/1024/.
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Friction Stir Welding (FSW) is known to result in a complex microstructural development, with features that remain unexplained, such as: the formation of the onion rings structure. Moreover, various microstructural factors have been suggested to control the strength in Al-Mg AA5xxx welds. The influence of the basemetal microstructural parameters (e.g. grains, intermetallic particles, stored energy) on the microstructure-property development has not been previously investigated, and is the subject of the present work. To rationalise the microstructural and local strength (hardness) development, especially within the heat affected zone (HAZ), a simple and rapid 3-D heat transfer model was established to predict the thermal fields associated with FSW. This numerical model utilises the alternating direction implicit method to simulate the transient thermal cycle based on the process parameters, thermo-physical and thermo-mechanical properties of the material. The model was fitted for the friction coefficient and contact conductance between the sheet and the backing plate using experimental torque and force data, as well as in-situ thermocouple measurements for AA2xxx and AA5xxx welds. The model predictions were consistent with the microstructural and microhardness development in the welds. Gleeble thermal simulations showed that the heating rate during welding affects the recrystallisation start temperature, which could delay or speed up recrystallisation. In the thermo-mechanically affected zone (TMAZ), the onion rings structure was studied in several AA5xxx and AA2xxx welds. This follows a thorough microstructural investigation of the basemetals sheets prepared by direct chill and continuous casting, to establish the influence of the microstructural heterogeneity in the basemetal on the onion rings formation and the microstructural development. Stereological studies of the intermetallic particle distributions in the basemetal and the welds revealed that there is a direct relation between the banding of constituent particles (Al(Fe,Mn)Si or Al6(Fe,Mn) in AA5xxx) or equilibrium phases (Al2CuMg or Al2Cu in AA2xxx) along the rolling direction, and the formation of the onion rings. A clear onion rings structure was defined by three microstructural features, which are: 1) the existence of fine and coarse grain bands, 2) grain boundary precipitates coinciding with the fine grain bands, and 3) coarse particle segregation in the coarse grain bands. Upon etching, these microstructural heterogeneities form the unique onion rings etching profile. The formation of the onion rings was rather independent of the process parameters and alloy type, as long as the intermetallic particles are banded regardless of their types. However, alloys with high area fraction of intermetallic particles (~> 0.02) were found to produce more pronounced microstructural heterogeneities, which resulted in a stronger etching intensity. The microstructural heterogeneities within the AA5xxx welds, especially the interaction between the dislocations and the fine Al6(Fe,Mn) dispersoids, indicated that establishing a structure-property model requires the incorporation of the various strengthening factors. Stereological studies of the grain size and intermetallic particle distributions in the TMAZ indicated that the hardness is a combination of various microstructural factors, with grain-boundary strengthening as the main factor, with additional contributions by Orowan strengthening by the Al6(Fe,Mn) particles in specific locations, as well as a minor contribution by solid solution strengthening which resulted from the dissolution of Mg2Si during welding. The high dislocation stored energy in the TMAZ, as measured by differential scanning calorimetry, was associated with the geometrically-necessary dislocations which resulted from the interaction with the intermetallic particles and grains, but do not contribute to the hardness.
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Murray, David L. "Friction stir processing of nickel aluminum propeller bronze in comparison to fusion welds." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Jun%5FMurray.pdf.
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Derry, Christopher Graham. "Characterisation and modelling of toughness in aerospace aluminium alloy friction stir welds." Thesis, University of Manchester, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494597.
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The effect of friction stir welding (FSW) on the toughness properties of two aerospace aluminium alloys has been investigated. Two typical aerospace alloys, high strength AA7449 and medium strength AA6013 have been studied in detail. The mechanical properties have been characterised via hardness testing, toughness testing and tensile testing incorporating strain analysis via digital image correlation. A notched 5ar test has been used to produce a profile of toughness across each of the welds and, in AA7449, through the depth of the welded plate. Each fracture surface was examined via FEGSEM to determine the mode of fracture and the microstructure was characterised, via optical microscopy and FEGSEM, such that the microstructural changes caused by FSW could be linked to the variations in toughness.
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Akinlabi, Esther Titilayo. "Characterisation of dissimilar friction stir welds between 5754 Aluminium alloy and C11000 copper." Thesis, Nelson Mandela Metropolitan University, 2010. http://hdl.handle.net/10948/1536.
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Friction Stir Welding (FSW) is a solid state welding process invented and patented by The Welding Institute (TWI) in 1991, for joining ferrous and non-ferrous materials1. The FSW of Aluminium and its alloys has been commercialised; and recent interest is focused on joining dissimilar materials. However, in order to commercialise the process, research studies are required to characterise and establish process windows. This research work through material characterisation of the welded joints establishes a process window for the Friction Stir welding of 5754 Aluminium Alloy and C11000 Copper. Furthermore, preliminary studies83,85 on the FSW of aluminium and copper have revealed the presence of intermetallic compounds which are detrimental to the weld qualities. This research work is also aimed at establishing process parameters that will result in limited or no intermetallic formation in the weld. The joint integrity of the resulting welds will also be correlated with the input process parameters. Based on the preliminary investigations conducted, a final weld matrix consisting of twenty seven welds was produced by varying the rotational speed between 600 and 1200 rpm, and the feed rate between 50 and 300 mm/min using three different shoulder diameter tools – 15, 18 and 25 mm to compare the heat input into the welds and to achieve the best results. The welds were characterised through microstructural evaluation, tensile testing, microhardness profiling, X-Ray Diffraction analysis, electrical resistivity and statistical analysis – in order to establish the interrelationship between the process parameters and the weld qualities. viii Microstructural evaluation of the weld samples revealed that the interfacial regions are characterised by mixture layers of aluminium and copper; while 33 percent of the tensile samples are within the acceptable range (> 75 percent joint efficiency). High Vickers microhardness values were measured at the joint interfaces, which corresponded with the intermetallic compounds. The Energy Dispersive Spectroscopy analysis revealed the presence of thin layers of intermetallics in nanoscale at the interfacial regions. The diffractograms of the X-Ray Diffraction analysis showed small peaks for intermetallics in some of the welds. Low electrical resistivities were measured at the joint interfaces. The statistical analysis showed that the downward vertical force, (Fz) can significantly influence the resulting weld qualities. An overall summary of the analysis of the weld qualities - with respect to the shoulder diameter tools employed showed that the 18 mm shoulder diameter tool is most appropriate among the three shoulder diameters considered, and a process window of medium spindle speed of 950 rpm and low-to-medium feed rate between 50 and 150 mm/min is established for FSW of Aluminium and Copper. Welds produced at 1200 rpm and 300 mm/min with low heat input did not have intermetallics formed at the joint interface.
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Baratzadeh, Farzad. "An investigation into methods to increase the fatigue life of friction stir lap welds." Thesis, Wichita State University, 2010. http://hdl.handle.net/10057/3293.
Full textAbstract:
Recent advancements in friction stir welding (FSW) technology have potential for applications in aerospace structures. Friction stir spot welds have been found to be much stronger than rivets in the same material thickness, while maintaining the discontinuous crack growth path preferred by aircraft designers. In this study, the test coupons have been investigated in fatigue with the weld aligned with the loading direction. The purpose of this study was to better understand crack initiation at friction stir weld exit holes in no-load transfer coupons representative of aircraft fuselage applications. The goal was to document the effects of weld exit location on fatigue life in discontinuous friction stir welded panels and to determine possible solutions in order to reduce the stress concentration around the exit hole location, thereby increasing the panel’s fatigue life. Aluminum alloys 7075-T6 and 2024-T3, which are commonly used in conventional airframe construction, were chosen for the FSW lap welds in this thesis. The methodology of this research was to weld the coupons with discontinuous friction stir lap welding using different exit hole configurations. The weld parameters such as rotation speed, travel speed, lead angle and load force had already been evaluated prior to this investigation in an earlier study during the first year of this project by Josh Merry. Once all of the coupons were welded, the next step was to fatigue test them with constant amplitude in order to determine the number of fatigue cycles and then compare all the different coupon results with the baseline coupon result that were determined in the previous study.
This project investigated a number of weld exit strategies with conventional one-piece weld tools. This study also included welds produced with a two-piece weld tool called Retractable Pin Tool (RPT) in which the length of the tool probe can be adjusted during welding. The RPT weld tool was used to eliminate the exit hole of the weld in order to reduce or eliminate
viii
the stress concentration around the weld exit. The ultimate goal of this research was to achieve equivalent or better fatigue life in discontinuous FSW joints as compared to riveted coupons.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering.
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Naidu, Rajesh Soschinske Kurt A. "Friction stir welding thermal effects of a parametric study on butt and lap welds /." Diss., A link to full text of this thesis in SOAR, 2006. http://soar.wichita.edu/dspace/handle/10057/669.
Full textAbstract:
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering."December 2006." Title from PDF title page (viewed on Nov. 4, 2007). Thesis adviser: Kurt A. Soschinske. Includes bibliographic references (leaves 70-72).
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Baker, Sarah. "Investigating the process-microstructure-mechanical property development in Ti-6AL-4V friction stir welds." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/6057/.
Full textAbstract:
The aim of the work reported in this thesis is to develop friction stir welding for superplastic titanium alloys. A number of studies have shown that friction stir welding is capable of retaining the fine-grained superplastic microstructure of the base metal and so there has been much commercial interest in combining it with superplastic forming processes. Within this programme friction stir welding was performed with a variety of process parameters and in both the conventional and stationary shoulder configuration. This meant that a number of welds were created with various rates of heat input. The elevated temperature and intense plastic deformation associated with the friction stir welding process substantially alters the base metal microstructure. As a result the influence of the process parameters on the microstructure, texture and residual stress development has been identified within this investigation. Tool wear and deformation also remains a hindrance in the commercialisation of friction stir welding titanium alloys. Wear and deformation of the tool not only changes its shape, but it can have further implications on the structural integrity of the weld. Thus the influence of the process parameters on wear and deformation of the tool have also been identified.
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Siggs, Eirian Bethany. "Laser and electron beam treatments for corrosion protection of friction stir welds in aerospace alloys." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/479/.
Full textAbstract:
Friction Stir Welding (FSW) is a suitable technology for aerospace structure development and is a possible replacement for mechanical fastening. To achieve the application of FSW, pre and post-weld treatments are required. A pre-weld treatment of surface preparation was required to ensure a weld with good mechanical properties. The surface preparation necessary is the removal of paint and anodising layers from aerospace alloys. Laser paint removal was assessed and designed to remove these layers with only an oxide remaining, which welded to produce high quality welds. The post-weld treatment was essential to increase the corrosion resistance of the welded area. The improvement in corrosion resistance was achieved with High Power Beam Surface Modification (HPBSM), which created a homogeneous surface through rapid surface melting and solidification. The rapid thermal processing dissolved and dispersed the precipitate solute atoms which were retained in solid solution through planar solidification. Electron beams and various lasers were used in the HPBSM processing. Excimer Laser Surface Melting (LSM) improved corrosion resistance but the layer depth was restricted by processing parameters. HPBSM processing studies using an electron beam, USP-CO\(_2\) laser and Nd:YAG laser provided understanding on how processing parameters controlled the modified layer characteristics.
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Lam, Tze Jian. "Low Z-force Octaspot™ swept friction stir spot welds welding—conventional tool and process development approach." Thesis, Wichita State University, 2010. http://hdl.handle.net/10057/3314.
Full textAbstract:
An investigation was conducted to develop low Z-force (normal/forge load) friction stir spot welds (FSSWs) using conventional tooling and process development approaches. Low Z-forces can be achieved by studying the relationship between pin tool features, geometries, processing parameters, and resultant strength of coupons produced by friction stir spot welding (FSSW). The effects of geometrical and feature changes of pin tool designs—including shoulder diameters, shoulder features, probe diameters, probe shapes, and probe features—on the joint properties of 0.040-inch-thick bare 2024-T3 aluminum alloy were evaluated. Welding tools included Psi™, Counterflow™, Modified Trivex™, and V-flute™ pin tools. A Box-Behnken design of experiments (DOE) approach was used to investigate the effects of three process parameters: spindle speed, Z-force (forge load), and travel speed. The goal of the investigation was to maintain the ultimate tensile load (UTL) in unguided lap shear coupons tested in tension while reducing the Z-force required for producing a sound joint. This goal was achieved on a specially built MTS Systems Corporation ISTIR PDS FSW gantry system. In addition to single-spot unguided lap shear tests, the performance of low Z-force FSSW joints was evaluated by optical metallographic cross-section analyses, which were then correlated with process parameters, UTL, and pin tool designs. The maximum Z-force spikes encountered during the initial plunge were reduced by an order of magnitude, and the Z-force processing loads were reduced by half for Octaspot™ swept FSSW, most effectively by controlling the plunge rate under force control. Additional reductions in Z-force were achieved by refining the conventional FSSW tool shoulder and probe designs. Therefore, it was demonstrated that weld forces can be reduced to the point where it would be feasible to perform robotic low Z-force FSSW for at least some applications.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering.
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Brown, Jeremy Micah. "The effects of sealants and surface treatments on the faying surface of swept friction stir spot welds." Thesis, Wichita State University, 2008. http://hdl.handle.net/10057/2088.
Full textAbstract:
The goals of this project were to determine and document the effects of sealants and surface treatments have on the ultimate strength, fatigue life, and corrosion resistance of swept Friction Stir Spot Welded (FSSW) joints. One sealant, the PRC-DeSoto PR-1432 GP and several surface treatments were examined. The surface treatments attempted were AlClad, Chromic Acid Anodization on bare sheets, and Alodine chemical conversion coating on bare sheets. Bare sheets without a surface treatment were also evaluated to establish a baseline comparison. Ultimate lap shear testing was based on the unguided NASM 1312-4 2-spot weld coupon configuration and the guided NASM 1312-21 4-spot weld coupon configuration. Results indicated that the sealants and surface treatments decreased the joint strength of the individual spot welded joints a relatively small amount compared to the bare material strength. However, the sealant’s adhesive properties can potentially compensate for this loss if there is sufficient sealant coverage. The guided NASM 1312-21 4-spot weld coupon configuration was used for fatigue testing. Uniform amplitude fatigue tests were conducted with a variety of load levels to generate a load-life curve. The sealants and surface treatment seemed to have no effect on fatigue life at medium to low fatigue load levels. However, at high fatigue load levels, the sealants and surface treatments were slightly detrimental. The fatigue lives of the swept FSSW coupons was less than those of the NAS 1097 AD4 riveted coupons at the medium to low loads. However, the swept FSSW coupons were not optimized for fatigue and may improve under such conditions. The results of the corrosion testing indicated that the integrity of the sealant was not compromised by the swept FSSW. Generally, the surface treatments were not affected by the FSSW operation except where the tools displaced the surface and on the anvil side of the coupon in the heat affected zone. Since these areas are more vulnerable to corrosion, some protection should be added after welding. In general, the results of this project show that swept FSSW can successfully weld through sealants and surface treatments with only a minimum loss of the ultimate strength or fatigue life of the joint. The FSSW operation can be performed while maintaining most of the corrosion resistance.Wichita State University, College of Engineering, Dept. of Aerospace Engineering
Includes bibliographic references (leaves 50-54)
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Ahmed, Mohamed Mohamed Zaky. "The development of Thick Section Welds and Ultra-Fine Grain Aluminium Using Friction Stir Welding and Processing." Thesis, University of Sheffield, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.515422.
Full text
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Brown, Jeremy Micah Horn Walter. "The effects of sealants and surface treatments on the faying surface of swept friction stir spot welds." A link to full text of this thesis in SOAR, 2008. http://hdl.handle.net/10057/2088.
Full text
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Furse, Devin Donaldson. "Optimization and Correlation of the Penn State Model of Friction Stir Welding to Experimental Welds in 304L Stainless Steel." BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2524.
Full textAbstract:
A numerical model of friction stir welding developed by T. DebRoy, R. Nandan, and others has been optimized to fit experimental data of eleven welds of 304L stainless steel at various weld feed rates and spindle speeds. Optimization was used to determine the values of five difficult-to-measure model parameters. The optimal parameter values were then correlated to the weld machine inputs. The mechanical efficiency and the coefficient of friction were not correlated with feed rate, spindle speed, or axial pressure. Tool slip was positively correlated with feed rate, negatively correlated with spindle speed, and not correlated with axial pressure. The heat partition factor was positively correlated with feed rate, negatively correlated with spindle speed, and negatively correlated with axial pressure. The heat transfer coefficient at the bottom face was positively correlated with feed rate, not correlated with spindle speed, and positively correlated with axial pressure. The above welds were instrumented with thermocouples at the mid-plane of the workpiece. Recently acquired three-dimensional temperature data indicates that the two-dimensionally optimized model does not sufficiently capture the thermal profiles in all three directions. However, optimizing the model to fit the three-dimensional data does not yield acceptable results either. Several potential sources for model improvement are identified, primarily the modeling of heat transfer at the bottom surface. It is shown that using a spatially-variable thermal contact resistance approach is more theoretically justifiable and yields better temperature predictions.
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Huang, Jin-fa, and 黃金發. "Characteristics of Friction Stir Weld of Al2O3 Particulate-reinforced Aluminum Matrix Composites." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/83799107617125091889.
Full textAbstract:
碩士國立中正大學
機械工程所
96
Friction stir welding (FSW) is an innovative welding process in which the metal can be welded or stirred together by a high speed rotating tool (probe) using a milling machine. The process has been successfully applied to join aluminum and many other alloys. Particulate-reinforced metal matrix composite Al/Al2O3p is a light weighted high strength composite material developed for light weight and high strength applications. Welding of Al/Al2O3p has always been a problem due to melting and solidification resulting in clustering of Al2O3 powder. FSW will be a potentially appropriate process for joining Al/Al2O3p composites. The objective of this project is to develop the FSW process for this composite for light weight high strength structural applications. In this investigation, the friction stir welding was applied to butt on Al2O3 particulate-reinforced aluminum matrix composites. The material used was a particulate-reinforced Al2O3/6061 aluminum alloy with 10%, 15% and 20% volume fraction of Al2O3 powder. The welding surface and the microstructure of nugget were observed. Hardness and tensile strength of the welded specimens were evaluated. Dynamic load history during FSW was measured. From the results above, the characteristics of nugget, the flow pattern, the mechanical properties and the relationship between them were studied. Through appropriate combination of welding parameters, defect-free friction stir welds were successfully achieved. The aspect of mechanical characteristics, the hardness in the friction stir welds were above the hardness of base material. The tensile strength in the friction stir welds are approximately at the same level as the tensile strength of base material. The results explain that the hardness and tensile strength were improved in the friction stir welds.
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Lin, Yi-Hsien, and 林益賢. "Using hardness statistics variable of weld to evaluate the friction stir welding quality." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/34528166732481174511.
Full textAbstract:
碩士義守大學
工業工程與管理學系碩士班
98
In engineering application, the evaluation of welding quality is typically by means of hardness testing, metallographic observation, microstructure examination, and tensile testing; however, to perform the full quality vilification procedure is a time consuming and costly process. For optimizing the process parameters, a simplified procedure but with the benefit of lower cost and shorter time is demanded. Among those tests, hardness testing is, relatively, to be an economical and easy testing method; nonetheless, how to apply the hardness distribution data to evaluate the welding quality required an in-depth study. To cope with this issue, this thesis analyzed the statistic property of hardness distribution sampled from Friction stir welded (FSW) aluminum alloy and then proposed a quality factor for optimal process parameter design. The hardness distribution in FSW weld appears “hardness valleys” on both sides of the stir zone. The statistical information responded from the base metal (BM), heat affected zone (HAZ), thermal-mechanical affected zone (TMAZ), and stir zone (STZ) will reveal the corresponding mechanical properties, however, it is usually overlooked by averaging the hardness in STZ or by comparing, simply, the distribution trend qualitatively. The hardness data have not been properly treated, hence, the relationship between hardness and tensile strength or fracture location cannot be well defined for FSW. Therefore, in this research, the statistic property of hardness in a wide range around the weld bead are examined in detail based on the gray relation grade to find out a proper quality factor for the application of welding process parameter design using S/N ratio of Taguchi method. Moreover, the verification of the optimal model was performed by examining the correspondence of tensile strength and elongation. The results show that the variance of hardness covering the range from the BM, HAZ, TMAZ, STZ in the distance of two times of shoulder diameter has the largest gray relation grade with the average hardness of base metal and proof strength, respectively. Apply this variance of hardness as a quality factor for Taguchi method analysis, the optimal process parameter combination can be predicted. The prediction was confirmed by the correlating tensile strength and elongation. It is concluded that the variance of hardness is a proper quality factor for process parameter design. Apply this factor can obtain the optimal tensile strength of the weld in a simplified testing procedure and shorter testing time.
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cheng, Chun-chieh, and 程群傑. "Characterization of Friction Stir Weld of Aluminum Matrix Composites and Analysis of Welding Mechanisms." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/58978353849582915496.
Full textAbstract:
碩士國立中正大學
機械工程所
97
Particulate-reinforced metal matrix composite Al/Al2O3p is a light weighted high strength composite material developed for light weight and high strength applications. Welding of Al/Al2O3p has always been a problem due to melting and solidification resulting in clustering of Al2O3 powder. Friction Stir Welding(FSW) will be a potentially appropriate process for joining Al/Al2O3p composites. The objective of this investigation is to further and to enhance the strength of weldment and to develop the FSW process for this composite for light weight high strength structural applications. In this investigation, the friction stir welding was applied to butt on Al2O3 Particulate-reinforced metal matrix composite. The material used was a particulate-reinforced Al2O3/6061 aluminum alloy with 10%, 15% and 20% volume fraction of Al2O3 powder. Microstructural (optical, scanning electron and transition electron microscopy) observation and mechanical evaluation(hardness and tensile tests) were performed to explored the relationship between the characteristics of microstructure, the flow pattern and mechanical properties. The results show that the hardness of the stirred zone was higher than that of the base material. Due to fine-grain microstructure within stirred zone. The highest hardness reached in stirred zone at traverse speed 2.37mm/s, higher traverse speed resulted in decrease of hardness. The tensile strength of friction stir welds was similar to that of the base material. The TEM images reveal that lower dislocation density was observed in the recrystallized fine-grained microstructure of stirred zone. The probe wear during FSW process increased with increasing rotation speed of tool and the decreased with increasing traverse speed of tool. Higher volume fraction of Al2O3 powder resulted in the higher probe wear.
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Kumar, K. "Studies On Friction Stir Welding Of Precipitation Hardenable Aluminium Alloys." Thesis, 2009. http://hdl.handle.net/2005/720.
Full textAbstract:
Friction Stir Welding (FSW) is an emerging solid state welding process. It has been a proven method for welding high strength aluminium alloys which were previously not recommended for conventional fusion welding. Since the invention of the process by The Welding Institute, United Kingdom, in 1991, a number of studies have been conducted on the material flow, microstructural evolution and mechanical properties of friction stir welds. However, there is not enough conceptual background available on FSW process for physical understanding of the mechanism of weld formation. In addition to that, FSW welds of high strength precipitation hardenable aluminium alloys suffer from reduced joint efficiency due to overaging in the heat affected zone. In the present investigation, experimental analysis has been carried out to understand the mechanism of weld formation and parameter optimization for aluminium alloys 7020-T6 and 6061-T6. For this purpose the investigations have been made on both the process aspects and the material aspects.
The process aspects are analyzed with the objective of learning the mechanism to produce defect free welds. For this purpose experiments have been carried out to analyze the effect of FSW parameters, material flow and the frictional characteristics between the tool and base metal. Preliminary experiments are conducted on aluminium alloy 7020-T6 with different tool geometries to analyze the interaction of the tool with the base metal using a knee-type vertical milling machine. Then, the tool geometry which produced defect-free weld is used for further experimentation. The role of tool pin, shoulder and axial load on the formation of defect free weld is analyzed in an innovative experiment, where the tool and base metal interaction is continuously increased by continuously increasing the interference between the tool and base metal. In another experiment the initial abutting interface position with respect to the tool is continuously varied to study the interaction of the tool with the initial interface and to find the positional information where the initial interface is completely eliminated. Further, the tool metal interface condition is studied using a specially designed tribological experiment which simulates the FSW condition.
From the base metal point of view, due to the strain, strain rate and temperature imposed on the base metal during the process, the microstructure is altered. In precipitation hardenable aluminium alloys the strengthening precipitates are dissolved or overaged in the weld region depending on the peak temperature in the region, which reduces the joint efficiency. However, the dissolution and overaging are kinetic process. In order to analyze this time dependant softening behavior of the base metal 7020-T6 and 6061-T6, isothermal annealing and differential scanning calorimetric studies are performed.
In order to obtain FSW welds with maximum joint efficiency, the welding temperature should not exceed the “softening temperature” of the base metal. But, to produce defect free welds favorable material flow in the weld nugget is necessary. The material flow and consolidation depend on the process temperature. Hence, for a given tool to produce defect free weld there is a need for minimum temperature. If the weld formation temperature is less than the base metal softening temperature, the weld can be made with 100% joint efficiency. In order to optimize the FSW parameter which gives defect free weld with lowest possible temperature, an instrumented programmable FSW machine is designed and developed. The machine is designed in such a way that welding parameters – rotation speed, traverse speed and plunging depth – can be continuously varied from the start to end of the weld between given two values. This reduces the number of experimental trials, material and time.
Based on the experimental results the following conclusions are derived.
1.The minimum diameter of the pin required for FSW depends on the base metal and tool material property for a given set of parameters. If the pin diameter is insufficient for a given set of welding parameters, it fails during plunging operation itself.
2.There is a minimum diameter of the shoulder for a given diameter of the pin which produces defect free weld. The ratio of pin to shoulder to produce a defect free weld is not a constant value. It changes with tool geometry and process parameters.
3.Increasing the area of contact between the tool and shoulder for a given set of parameters increases the heat input and results in increased weld nugget grain size.
4.Initial abutting interface of the base metal is eliminated at the leading edge of the tool. However, new surfaces are generated due to interaction with the tool and the newer surfaces are consolidated at the trailing edge of the tool. Importantly, the weld strength is controlled by the defects generated due the improper elimination of newly generated surfaces.
5.Optimal axial load is required to generate the required pressure to consolidate the transferred material at the trailing edge of the tool and should be equal to the flow stress of the material at the processing temperature. The optimal axial load is 8.1kN for a tool having 20mm diameter shoulder with 6mm diameter frustum shaped pin.
6.Only the material that approaches the tool at the leading edge on the advancing side is stirred and the remaining material is simply extruded around the tool. Further, the initial abutting interface is completely removed only when it is located in the stirring zone, otherwise the initial abutting interface is not eliminated. In the present study the interface is completely stirred when it is located on the advancing side of the tool between 0.5mm away from the centerline and edge of the tool.
7.The temperature and pressure at the tool–base metal interface is above the temperature and pressure required for seizure to occur for given tool material (H13) and base metal (7020-T6). Hence, it is clear that during FSW the base metal transfers on to the tool and interaction occurs between transferred layer on tool and base metal. The coefficient of friction between the given tool material and base metal in FSW condition is in the range of 1.2 – 1.4.
8.The minimum temperature requirement for FSW of 7020-T6 is 400oC and 6061-T6 is 430oC. However, 7020-T6 and 6061-T6 softens at lower temperatures than that of the minimum FSW temperature. 7020-T6 softens 30% in 7min at 250oC, 4min at 300oC, 2min at 350oC and 1min at 400oC. After softening 30%, there is 10% recovery in hardness and the hardness remains constant thereafter. Whereas 6061-T6 softens gradually up to 47% in 7min at 350oC and 400oC, below the temperature of 250oC for 7020-T6 and 350oC for 6061-T6 there is no softening observed in 7min.
9.The maximum joint efficiency of the 7020-T6 weld is 82% and 6061-T6 weld is 60%.
10. The reduction in joint efficiency is attributed to overaging of the material in the heat affected zone.
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James, Andre. "Localized Corrosion of FrictionStir Spot Welds in AZ31 Magnesium Alloys." Thesis, 2012. http://hdl.handle.net/1807/35538.
Full textAbstract:
A scanning reference electrode technique (SRET) apparatus has been designed and commissioned to investigate the corrosion of friction stir spot welds (FSSW) made in AZ31 magnesium alloys. The operational parameters of the apparatus have been calibrated to give good spatial resolution. By combining the SRET data with material flow data and immersion test data it was found that the FSSW process caused the formation of distinct noble and active regimes within the weld area. The noble region was aligned with the stir zone (SZ) and was caused by a dynamically recrystallized grain structure which is void of dislocations / twins, and β Mg17Al12. Localized corrosion attack was observed in both SRET and immersion testing along the thermo-mechanically affected zone (TMAZ). The same effect was consistently observed with a flat versus concave shoulder tool, and dwell times of 1s and 4s.
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Lin, Din-wei, and 林鼎崴. "Characterization of Weld and Analysis of Welding Mechanisms of Friction Stir Welding(FSW) on Aluminum Alloy." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/59428240718121205274.
Full textAbstract:
碩士國立中正大學
機械工程所
95
Aluminum alloys especially 6061 alloy have been extensitively applied to various parts. In aircrafts and automobiles Friction stir welding (FSW) is even more suitable for welding aluminum alloys compared with conventional are welding process. FSW is a solid state welding process, with metal plates can be welded together by stirring severe plastic any deformed metal matrix without melting. Due to less heat,the heat affected zone(HAZ) is small, so that a geometrical of the weldinent may not be necessary. This study mainly focused on 6061-T aluminum alloy. Friction stir welding was conducted under different conditions to investigate the material flow in the nugget. We coated a thin layer of Al2O3 powder on butt surfaces by means of flame sprayingand the power particles can be used as trace-revealing material.We also intended to form a metal-matrix composite in the stirred zone by mixing ceramic powder (Al2O3) to strengthen the nugget.A dynamometer was used to determine the dynamic axial loadings during FSW process. A defect-free nugget con be formed under appropriate rotation speed and feeding speed when tool rotated counterclockwise. Furthermore, when an optimized parameter combination in reached, the dynamic axial loading decreased significantly. Also the clear onion ring structure was observed at these conditions. As to mechanical properties, nugget hardness was lower than matrix and the lowest handness value was in HAZ. It is due to grain growth and solution of precipitate. The tensile strength under optimized parameters could was higher than 65% of that of matrix aluminum alloy. Ductility could reach half of that of matrix. The mechanical properties were better than conventional are welding process. Addition of Al2O3 powder would increase of defect. This might be due to that fact that Al2O3 is a thermal barrier material and hindered the heat transfer.
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Chang, Wei Lin, and 張維麟. "Study on the Friction Stir Welding of 6061 Aluminum Alloy and its Particulate-reinforced Weld Metal." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/39063863364593440138.
Full textAbstract:
碩士國立中正大學
機械系
93
The future trend of automotive manufacturing is to adopt aluminum or magnesium alloy to replace traditional steel materials to achieve weight reduction. The Audi all new automobile made of aluminum alloy have been on market, and that is the brand new milestone of weight reduction. It reveals that the mass production of lightened automobiles is successfully developed. Aluminum/magnesium metal-matrix composite (MMC) are the most potential materials for lightening. Since 1991, friction stir welding (FSW) has been applied for aircraft frame manufacturing. And FSW does have its potential application of manufacturing of chassis, structure of whole aluminum automobile. The distinguishing characteristic of FSW is solid phase welding process. The yield strength of aluminum alloy decreases with the increasing temperature. Thus, it is much easier to stir the easy plastic deformed matrix material and be welded without fusion-solidification. On the other hand, weld nugget strength is minor affected by the adjacent heat affected zone (HAZ) and therefore need no additional strengthening from structural design. Besides, there is no defect in weld nugget brought by FSW. The integrity of structure after weld is far better than that achieved by conventional traditional welding techniques, e.g. MIG, TIG and thus promotes the safety of impact. In this study, we try to develop FSW process suitable for advanced MMC or ceramic materials. The butt-weld FSW process was conducted for of aluminum alloy. Alumina powder is added to aluminum using flame-spray coating prior to FSW and is brought into nugget by FSW. Then we investigate the strengthening mechanism, materials properties of the welded structure and measure the dynamic load on XYZ axes respectively using dynameters and load cells. Optimum parameters can then be established for FSW the materials studied.
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Widener, Christian Aragon. "Evaluation of post-weld heat treatments for corrosion protection in friction stir welded 2024 and 7075 aluminum alloys." Diss., 2005. http://hdl.handle.net/10057/612.
Full textAbstract:
This dissertation presents the results of an investigation into the corrosion resistance of friction stir welding (FSW) for aerospace structures. Two of the most common aerospace aluminum alloys, 2024 and 7075, were investigated. In the as-welded condition, both alloys were found to be highly susceptible to exfoliation corrosion, and 7075 was found to be susceptible to stress corrosion cracking as well. The goal of this research was to identify proper initial temper selection and postweld aging treatments for enhancing the corrosion resistance of both 2024 and 7075 alloys, and their dissimilar joints. A large number of heat treatments were investigated for 7075 in the T6 and T73 tempers, including retrogression re-aging (RRA). Heat treatments were also investigated for 2024-T3 and 2024-T81. Samples were evaluated for resistance to exfoliation corrosion using optical microscopy. Microhardness, electrical conductivity, tension, and fatigue crack propagation tests were also performed on the samples. Beneficial heat treatments were found for both alloys as well as for their dissimilar joints."December 2005."
Thesis (Ph.D.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering
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Chang, Hung-Tu, and 張宏圖. "A study on the microstructure of weld nugget and mechanical properties of ductile iron jointed by friction stir welding." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/994ee6.
Full textAbstract:
博士國立臺灣科技大學
機械工程系
102
Abstract Friction stir welding (FSW) is a novel solid-state welding technology, which features a non-consumable rotating tool acting on metal plates. Because the spindle rotation and the feeding process cause severe plastic deformation in the stir zone of the metal plate, welding is achieved through thermo-mechanical reactions. During the entire welding process, the welding temperature remains lower than the melting point; thus, melting in the weld area does not occur, resulting in the development of weldments with low-deformability, high-quality, and low-cost characteristics. Ductile iron is widely applied in the field of mechanical engineering because, in addition to its affordability, it possesses outstanding formability, appropriate mechanical properties, and superior damping capacity. The objective of this study is to demonstrate the feasibility of friction stir butt-welding for joining of ferritic ductile iron by different welding parameter. According to the experimental results, the welding region was composed of deformed graphite, martensite phase, and dynamically recrystallized ferrite structures. In the surface region and on the advancing side (AS), the graphite displayed a striped configuration and the ferritic matrix transformed into martensite. On the retreating side (RS), the graphite surrounded by martensite remained as individual granules and the matrix primarily comprised dynamically recrystallized ferrite. A micro Vickers hardness test showed that the maximum hardness value of the martensite structures in the weld was approximately 800 HV. After welding, diffusion increased the carbon content of the austenite around the deformed graphite nodules, which transformed into martensite during the subsequent cooling process. To resolve the poor weldability of ductile irons, this study employed AISI-1008 low-carbon steel as the top plate and ferritic ductile iron as the bottom plate and varied the rotational and traveling speeds to conduct a friction stir lap welding test. After welding, the weldments underwent microstructure analysis and hardness testing followed by a tensile shear test to evaluate the joint strength. At a high rotational speed above 1000 rpm combined with traveling speeds that ranged between 40 and 70 mm/min indicated the following: An excellent joining effect was achieved; the interfacial regions of the carbon steel and cast iron primarily comprised pearlite, although the vicinity of the retreating side and the stir zone matrices of ductile irons were composed of martensite structures; individual graphite granules were present; the tensile shear strength of the weldments was high; and the fracture portion was located in the low-carbon steel base metal. In order to explore the weldability of austenitic ductile iron, this study employed AISI-1008 low-carbon steel as the top plate and austenitic ductile iron as the bottom plate and varied the rotational speed to conduct a friction stir lap welding test. According to the experimental results of tensile shear stress test, at the welding condition of 1100 rpm-50 mm/min indicated the tensile shear stress value was about 900 N. In addition to conducing post-welding friction stir processing that combined traveling speed 50 mm/min with rotational speed between 1200 and 2100 rpm. Consequently a well joining effect elevated tensile shear stress value above 6000 N.
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Wei, Chih, and 黃智威. "Analysis on Flow Behavior and Mechanical property of Lap Joint Friction Stir Weld of Aluminum-Clad 2024-T3 Aluminum Alloy Sheets." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/48713916385854171097.
Full textAbstract:
碩士國立中正大學
機械工程所
98
The objective of this research is to study the friction stir welding of lap joint of the Aluminum-Clad 2024-T3 sheet metal. Friction stir welding was conducted process at different parameters such as tool rpm, tool revolution direction, feeding rate, and tool geometris. During the welding process, dynamic load and temperature history use recorded, to observe the flow behavior at the stir zone. The appearance of the weld surface, macro-and microstructure of the weld cross section were observed to understand the flow behavior of the friction stir weld, the joining mechanisms of the lap joints, and the weld metal characteristics of the Aluminum-Clad 2024-T3 lap joints. The tool or probe geometries play an dominant role in the flow behavior of the friction stir lap joint. Probes with cylindrical thread caused a vertical flow in the stir zone at the interface of the pure aluminum layer in between the upper and lower plate. The vertical material flow resulted in a reduction of the effective sheet thickness. On the other hand, probes with eccentric triangular geometry to a horizontal flow behavior of the material, so that the aluminum surface coating remained maximal horizontal at the interface. With this tool effective sheet thickness in the stir zone is achieved. Rewelding on the same weld bead with different feeding rates resulted in an accumulative effect of the material flow. Four types of failure modes were concluded from the fracture analysis and tensile strength : fracture at efftective sheet thickness, the defect on which tensile stress concentrates, of the stir zone, HAZ, interface peeling. Material welded by FT13-2 tool revealed the best tensile stress. The fracture mode was the HAZ fracture. Dynamic load measurement was also combined to analyze the effects caused by different process parameters and the tool geometry. The T15.5 tool resulted in a horizontal material flow in the stir zone. Successive friction stir welding on the same plate resulted in temperature rise of the material, which had a negative effect in the tensile stress and fracture mode.
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Costa, Maria Inês Martins dos Santos. "Lap joining of very thin plates by friction stir welding: Mechanical characterisation of the welds and thermal distortion analysis." Doctoral thesis, 2019. http://hdl.handle.net/10316/87433.
Full textAbstract:
Tese de Doutoramento em Engenharia Mecânica, no ramo de Tecnologias de Produção, apresentada ao Departamento de Engenharia Mecânica da Faculdade de Ciências e Tecnologia da Universidade de CoimbraThe increasing use of aluminium alloys in welded construction brings new challenges concerning the joining of these non-ferrous materials using the conventional welding methods. The development of new methodologies has overcome these challenges, per example, using solid-state welding technologies, such as the Friction Stir Welding (FSW) or, due to the high interest in lap joining for industrial applications, the Friction Stir Lap Welding (FSLW). This type of technology involves temperatures below the melting point, which, as it is well-known, leads to lower levels of plates’ distortion, comparatively to the other welding processes. The use of thin plates, widely applied in the transportation industries, bring new challenges to nowadays assembling methodologies. Using thin plates welding magnifies the deleterious influence of the weld defects in the welds mechanical performance. However, nowadays literature is mostly based on thicker plates (> 2 mm) analysis. Moreover, works relating base material mechanical behaviour, welding parameters, weld strength and distortion, are inexistent or scarce. Present work titled “Lap joining of very thin plates by friction stir welding: mechanical characterization of the welds and thermal distortion analysis” aims to obtain a deep understanding of the base material and process parameters influence on defect formation and distortion during FSLW of thin plates. Similar and dissimilar welds were performed in a heat treatable and a non-heat heat treatable aluminium alloys, the AA6082-T6 and the AA5754-H22, respectively. The influence of the local mechanical properties heterogeneities and the presence of small defects on the mechanical behaviour of the welds, under monotonic and cyclic loading conditions, was assessed experimentally. The results obtained showed that the different mechanical behaviour of the base materials, at high temperatures, has a substantial impact on the defect formation and weld’s cross-section morphology. However, other factors such as tool geometry and process parameters are equally crucial for producing non-defective welds. In fact, an optimal tool geometry was found during this investigation. This tool minimises the amount of material from the bottom plate, being moved upwards, minimising the size of the hook defect, which is a typical FSLW defect. Despite the use of such tool, it was only possible to produce defect-free welds by using the AA5754 alloy, showing that the AA6082 aluminium alloy is more sensitive to the defects formation. Moreover, the presence and severity of defects, and the section reduction, promoted by the action of the tool during the process, are the main mechanisms affecting the welds mechanical strength. In addition, for the heat treatable alloy (AA6082) welds, the softening observed in the TMAZ and HAZ also contributed to the lower mechanical performance of these welds. In fact, due to the different base material strengthening mechanisms, the welds local mechanical properties varied differently with the process parameters. For the AA5754 aluminium alloy, a good mechanical efficiency was observed during tensile-shear testing, independently of the welding speed, and the weld side tested. Contrarily, for the AA6082 welds, it was found that tensile-shear strength strongly depends on the welding speed, and the weld side tested. The post-weld heat treatment of the AA6082 welds enabled to increase the joint efficiency of the welds at monotonic loading conditions, but decreases it at cyclic loading conditions, which made possible to conclude that the softening of the base material in as-welded condition has a useful contribution on welds’ fatigue life. Finally, the analysis of the weld induced distortion made possible to conclude that the plates’ size has a higher influence on the distortion mode and magnitude than the welding parameters and releasing conditions tested. Comparing the experimental distortion measurements with the numerical results of the residual stress distribution was possible to conclude that the distortion magnitude is strongly related with the compressive residual stresses magnitude; and that the distortion mode depends on the residual stress distribution. The magnitude of the compressive residual stresses evolution with the welding speed is non-linear with welding speed, but increases for increasing tool rotation speeds.
O uso crescente de ligas de alumínio na indústria dos transportes, gerou novos desafios em relação à união destes materiais através dos métodos convencionais de soldadura. Estes desafios têm sido superados pela introdução de tecnologias de soldadura inovadoras, como por exemplo, processos de soldadura em estado sólido, como a Friction Stir Welding (FSW) ou, devido ao elevado interesse das juntas sobrepostas em aplicações industriais, o Friction Stir Lap Welding (FSLW). Envolvendo temperaturas abaixo do ponto de fusão, o FSW, tenderá a reduzir a magnitude da distorção das chapas soldadas, quando se compara com a distorção observada nas chapas soldadas pelos processos convencionais de soldadura por fusão. A ampla utilização de chapas finas nas indústrias de transportes trouxe novos desafios para as atuais metodologias de fabrico. De fato, a influência dos defeitos de soldadura é ampliada quando se usam chapas finas, comprometendo o desempenho mecânico das mesmas. No entanto, a literatura atual baseia-se na sua maioria, no estudo da união de chapas com espessuras superiores a 2 mm. Ademais, os trabalhos que relacionam o comportamento mecânico do material de base, os parâmetros de soldadura, a resistência mecânica da soldadura e a distorção das chapas, são inexistentes ou escassos. O presente trabalho intitulado “Ligação em junta de chapas finas por friction stir welding: caracterização mecânica das soldaduras e análise da distorção térmica”, visa obter uma profunda compreensão da influência do comportamento mecânico do material de base e dos parâmetros do processo na formação de defeitos, e na distorção das chapas finas, soldadas por FSLW. Realizaram-se soldaduras similares e dissimilares, em ligas de alumínio tratáveis e não tratáveis termicamente, os alumínios AA6082-T6 e AA5754-H22, respetivamente. A influência de heterogeneidades das propriedades mecânicas e da presença de defeitos no comportamento mecânico das soldaduras foram avaliadas experimentalmente. Os resultados mostram que os diferentes comportamentos mecânicos dos materiais de base a altas temperaturas, têm um impacto preponderante na formação de defeitos e na morfologia da seção transversal das soldaduras. No entanto, outros fatores como a geometria da ferramenta e os parâmetros do processo são igualmente cruciais para a produção de soldaduras sem defeitos. De fato, foi possível selecionar uma geometria de ferramenta ótima, que permitiu minimizar a quantidade de fluxo de material ascendente, minimizando o tamanho dos defeitos ou até a sua eliminação. Apesar do uso desta ferramenta, só foi possível produzir soldaduras sem defeitos utilizando a liga AA5754, uma vez que a liga de alumínio AA6082 apresentou uma maior sensibilidade à formação dos mesmos. Ademais, a presença e a severidade dos defeitos, assim como a redução de espessura, promovida pela ação da ferramenta durante o processo, são os principais mecanismos que afetam a resistência mecânica das soldaduras. Para além dos defeitos de soldadura, o amaciamento observado nas soldaduras produzidas na liga tratável termicamente (AA6082), também contribuiu para o seu menor desempenho mecânico. De fato, devido aos diferentes mecanismos de endurecimento dos materiais de base, as propriedades mecânicas locais das soldaduras variam de forma diferente, conforme os parâmetros do processo. Para a liga de alumínio AA5754, foi observada uma boa eficiência mecânica durante o ensaio de tração em corte, independentemente da velocidade de soldadura e do lado da soldadura testado, contrariamente ao que se verificou na análise das soldaduras da liga AA6082. O tratamento térmico das soldaduras AA6082 possibilitou aumentar a eficiência mecânica das mesmas nas condições de carregamento monotónico, mas diminuiu a sua resistência nas condições de carregamento cíclico. Assim, foi possível concluir que o amaciamento do material da soldadura contribuiu positivamente para performance das soldaduras durante os ensaios de fadiga. Finalmente, a análise da distorção das chapas soldadas possibilitou concluir que o tamanho das chapas tem maior influência no modo e na magnitude da distorção, do que os parâmetros de soldadura e as condições de libertação testadas. Comparando as medições experimentais de distorção com os resultados numéricos da distribuição das tensões residuais, foi possível concluir que o modo de distorção depende da distribuição das tensões residuais, e a magnitude da distorção está fortemente relacionada com a magnitude das tensões residuais compressivas. A magnitude das tensões residuais de compressão varia não linearmente com a velocidade de soldadura, aumentando com o aumento da velocidade de rotação da ferramenta.
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Nguyen, Van Nhat, and 阮文一. "Study on the Welding Features of the Weld Joint betweenAluminum Alloy to Stainless Steel and Aluminum Alloy to DualPhase Steel by Using TIG and Friction Stir Welding." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/ehrwq7.
Full textAbstract:
博士國立高雄科技大學
機械工程系
107
Due to the advantages such as light weight, corrosion resistance and high oxidation resistance, the connection between aluminum alloys and stainless steel,aluminum alloys and dual phase steel has used more widely in industrial applications. However, to weld the metal together, there are still many challenges. Such as, the melting point of steel is much larger than that of aluminum, the difference in mechanical properties and chemical composition. Especially at the interface between the stainless steel and weld seam easily form an intermetallic compound (IMC) layer brittle and cracks. These problems will have a negative impact on the strength of the joint and the quality of the weld. To prevent the formation and development of the IMC layer and the formation of defects improving the quality of the welding joint, it is necessary to have a proper welding method and set of welding parameters. In this study, Friction Stir Welding (FSW) and Tungsten Inert Gas (TIG) welding were used to weld Aluminum AA6351/DP800 steel and aluminum A6061-T6/SUS304L steel, respectively. Lap joint between AA6351 to DP800 steel was carried out successfully by a friction stir welding method. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) technique was utilized to investigate the microstructural characteristics of the weld. The survey results showed that at the interface between steel and aluminum alloy have appeared intermetallic compound layer with a thickness less than of 7μm, and the phases exist in IMC layer includes Al3Fe, Fe3Al, and Al2Fe phases. Thermal cycles were also examined to show the relationship between the distributions of temperature with the formation of the intermetallic layer. The characteristics of Butt joint between aluminum and steel by using TIG welding with ER4047 filler metal were analyzed. The optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-Ray diffraction (EDS) have been done to demonstrate the microstructure of the weld. Test results illustrated that the appearance of the weld good, no defects, and the heat-affected zone is very small. Further, an intermetallic compound layer and cracks was also found at the interface between the steel and the welding seam, its thickness of 2 µm. The new phases formed in an intermetallic layer comprising Fe4Al13, Fe2Al5, and FeAl3 phases. The mechanical properties of the welded joint have been explored by means of a Vickers hardness test and tensile test method. As a result, the average value of hardness in the stainless steel, in the welding seam, and in the intermetallic layer is 218 HV, 79 HV, and 411 HV, respectively. Maximum tensile strength reached 226.5 Mpa and the fracture location occurred at the welding-brazing surface. Keywords: Tungsten Inert Gas (TIG) process, Friction Stir Welding (FSW) process, Filler metal, DP800 steel Intermetallic compound layer (IMC), Microstructure, Mechanical properties, Thermal Cycles