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Bagaitkar, Harish. "Design for manufacturing for friction stir welding." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/Bagaitkar_09007dcc805a2c42.pdf.
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Thesis (M.S.)--Missouri University of Science and Technology, 2008.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed December 2, 2008) Includes bibliographical references.
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Erickson, Jonathan David. "Design and Characterization of a Plunge-Capable Friction Stir Welding Temperature Feedback Controller." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/7461.
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Temperature control in friction stir welding (FSW) is of interest because of the potential to improve the mechanical and microstructure characteristics of a weld. Two types of active temperature control have been previously implemented for steady-state friction stir welding conditions: PID Feedback Control and Model Predictive Control. The start-up portion of a weld is an obstacle for these types of active control.To date, only minimal exploratory research has been done to develop an active temperature controller for the start-up portion of the weld. The FSW temperature controller presented in this thesis, a Position-Velocity-Acceleration (PVA) controller implemented with gain-scheduling, is capable of active control during the start-up portion of a weld. The objectives of the controller are (1) to facilitate fully-automated active temperature control during the entire welding process, (2) to minimize the rise time, the settling time, the percentage maximum post-rise error (overshoot calculated as a percentage of the settling band half-width), and the post-settled root-mean-square (RMS) of the temperature error, and (3) to maintain the steady state performance of previous control methods.For welds performed in 6.35 mm plates of 7075-T651 Aluminum with controller gains identified through a manual tuning process, the mean controller performance is a rise time of 10.82 seconds, a settling time of 11.35 seconds, a percentage maximum post-rise error of 69.86% (as a percentage of the 3◦C settling band half-width), and a post-settled RMS error of 0.92◦C.Tuning of the start-up controller for operator-specified behavior can be guided through construction of regression models of the weld settling time, rise time, percent maximum post-rise error, and post-settled RMS error. Characterization of the tuning design space is performed through regression modeling. The effects of the primary controller tuning parameters and their interactions are included. With the exception of the post-settled RMS error model, these models are inadequate to provide useful guidance of the controller tuning, as significant curvature is present in the design space. Exploration of higher-order models is performed and suggests that regression models including quadratic terms can adequately characterize the design space to guide controller tuning for operator-specified behavior.
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Covington, Joshua L. "Experimental and Numerical Investigation of Tool Heating During Friction Stir Welding." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd961.pdf.
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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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Record, Jonathan H. "Statistical Investigation of Friction Stir Processing Parameter Relationships." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd732.pdf.
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Zhou, Xingguo. "Friction stir welding simulation, optimization and design." Thesis, University of Strathclyde, 2013. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=25244.
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Friction stir welding is an advanced welding technology mainly used to join aluminum alloys but with potential for other materials like steel, titanium and its alloys. The aim of this work is to provide a combination of numerical and experiment tools to understand the mechanisms of friction stir welding, optimizing the friction stir welds and characterizing the material properties for welds. The thesis is broadly divided into three themes. In the first theme, an automatic procedure to estimate friction stir welding model parameters, particularly those difficult to measure directly, is proposed and developed. The proposed methodology is seen to predict heat input power from the welding tool and contact conductivity between the workpiece and its supporting plate in good agreement with experimental temperature history data. In the second theme, discontinuous and distributed cooling methods, which use periodical and non-uniformly distributed cooling medium flow to cool the welding workpieces, are proposed to reduce the residual stress of friction stir welds and investigated using multi-physics numerical simulation to predict transient temperature field, residual stress and mechanical performance of welds. The discontinuous cooling method is found to be more effective than conventional active cooling, leading to a lower drop in induced welding temperature and reduced residual stress. The distributed cooling provides another method to balance residual stress and welding temperature for butt welding. The effect of discontinuous cooling on microstructure is evaluated using the multi-physics model. The third part presents small punch beam testing method to characterize material properties of base material, welded material and material property distribution. The small punch beam test utilizes miniaturized specimen and is therefore suited to measuring material properties in local regions of structure, such as the friction stir welding nugget.
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Pehkonen, Henri. "Design of Gas Shield for Friction Stir Welding Machine." Thesis, Linköpings universitet, Maskinkonstruktion, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-126605.
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The research and development of the final disposal of the nuclear waste produced by the nuclear power plants is an important work done by The Swedish Nuclear Fuel & Waste Management Co. (SKB). As the demands on a final disposal increase the laboratory equipment has to be better in order to do valid experiments. Research on how the copper canister for the spent fuel will be manufactured and handled is done at the Canister laboratory in Oskarshamn, Sweden. The work presented in this report was to design a new gas shield for the friction stir welding machine at the laboratory. The welding machine seals the canisters containing the spent fuel which are then transported to the final disposal 500 meter down in basement rock. To minimize the amount of oxide particles in the weld zone SKB have to design a better gas shield that should deliver the required atmosphere around the welding area. The work contains a pre study phase where the important things to consider when designing are collected. Then ideas are generated and concepts created for a new gas shield. These concepts are evaluated by a pair wise comparison method in order to find the most promising concept. The concept chosen is then detail designed to come as close to a manufacturable design as possible.Utvecklingen av ett slutförvar för det urbrända kärnbränslet som blir avfallsprodukten vid framställning av energi via kärnkraft är ett viktigt arbete som drivs av Svensk Kärnbränslehantering AB. Då kraven och bevisningen på huruvida ett slutförvar ska utföras på ett säkert sätt måste experimenten och försöksutrustningen bli bättre för att generera tillförlitliga resultat. Forskning om hur kopparkapseln för det urbrända kärnbränslet ska konstrueras och hanteras pågår vid Kapsellaboratoriet i Oskarshamn. Arbetet som presenteras i denna rapport tar upp konstruktionen av ett nytt gasskydd till friktionsomrörningssvetsningsmaskinen på Kapsellaboratoriet. Svetsmaskinen försluter kapslarna med radioaktivt avfall vilka sedan transporteras 500 meter ner i det svenska urberget. För att minska mängden oxidpariklar kring svetsområdet måste SKB tillverka ett nytt gasskydd vilket bör uppfylla de krav på atmosfären kring svetsområdet som finns. Arbetet består av en forsknings- och informationssamlingsfas där viktiga aspekter och problemområden hittas. Sedan genereras idéer och nya koncept på gasskydd fås fram. Koncepten utvärderas parvis med metoden ”pair wise comparison” för att hitta det mest lovande konceptet. Konceptet detaljkonstrueras och tillslut fås en design vilken är så nära tillverkningsbar som möjligt.
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Liechty, Brian C. "Material Flow Behavior in Friction Stir Welding." Diss., CLICK HERE for online access, 2008. http://contentdm.lib.byu.edu/ETD/image/etd2403.pdf.
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Blignault, Calvin. "Design, development and analysis of the friction stir welding process." Thesis, Port Elizabeth Technikon, 2002. http://hdl.handle.net/10948/1350.
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The development of a CNC-based technology FSW machine to accurately produce friction stir weld samples that can be analyzed for research purposes is implemented and discussed. A process diagnosis and control scheme to improve the process monitoring and weld evaluation capabilities of an FSW machine are proposed and implemented. Basic CNC-based hardware implementation such as optical encoders and inverters for process control are explained and verified. The control scheme and framework of interfaces to the digital I/O cards for PC user interface are explained. An advanced monitoring system which senses process performance parameters such as tool temperature, 3-axis tool forces, torque and spindle speed are explained. Mechanical designs and manufacturing techniques such as tool, clamp and backing plate designs are explained and verified. The process parameters for quality optimization are investigated and optimized by making use of Correlation and Regression Analysis. The statistical data and analytical relationships between welding parameters (independent) and each of the performance parameters (dependent) are obtained and used to simulate the machining process. The weld research samples are tested for strength and integrity making use of various scientific testing techniques. The reliability of the samples are also evaluated and compared to that of other institutions. Process variables and the optimum operating range of the Friction Stir Welding machine is determined and a framework for further research into weld quality optimization is set.
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Tipaji, Pradeep Kumar. "E-design tools for friction stir welding: cost estimation tool." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.mst.edu/thesis/pdf/Tipaji_09007dcc8043f642.pdf.
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Thesis (M.S.)--University of Missouri--Rolla, 2007.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed February 5, 2008) Includes bibliographical references (p. 29-31).
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Marrero, Robert L. Jr. "Analysis of Variable Insensitive Friction Stir Welding Parameters." ScholarWorks@UNO, 2017. http://scholarworks.uno.edu/td/2385.
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Friction Stir Welding (FSW) was used to perform a Design of Experiment (DOE) to determine the welding parameters effects on yielding consistent mechanical properties across the length of the weld. The travel speed was varied across set forge force and RPM conditions, to find a dataset that will yield consistent mechanical properties independent of the travel speed. Six different welds were completed on two different aluminum panels, the advancing side being Aluminum alloy 2195-T8 at a thickness of .350”, with the retreating side being Aluminum alloy 2219-T851 with a gauge thickness of .360”. A Left-hand Right-hand self-reacting pin tool was used for each weld. The mechanical properties of interest are the Ultimate Tensile Strength, Yield Strength, Elasticity and Hardness. The strengths were evaluated by tensile testing, with the Elasticity being measure post break. Specimens were then polished where macrograph and micrograph analysis was completed. Micro-hardness testing was then completed on the weld nuggets.
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Stratton, Daryl A. "Characterizing the Frictional Interface in Friction Stir Welding." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1757.pdf.
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Strand, Seth R. "Effects of Friction Stir Welding on Polymer Microstructure." Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd338.pdf.
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Martinez, Nelson Y. "Friction Stir Welding of Precipitation Strengthened Aluminum 7449 Alloys." Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc862775/.
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The Al-Zn-Mg-Cu (7XXX series) alloys are amongst the strongest aluminum available. However, they are considered unweldable with conventional fusion techniques due to the negative effects that arise with conventional welding, including hydrogen porosity, hot cracking, and stress corrosion cracking. For this reason, friction stir welding has emerged as the preferred technique to weld 7XXX series alloys. Aluminum 7449 is one of the highest strength 7XXX series aluminum alloy. This is due to its higher zinc content, which leads to a higher volume fraction of eta' precipitates. It is typically used in a slight overaged condition since it exhibits better corrosion resistance. In this work, the welds of friction stir welded aluminum 7449 were studied extensively. Specific focus was placed in the heat affected zone (HAZ) and nugget. Thermocouples were used in the heat affected zone for three different depths to obtain thermal profiles as well as cooling/heating profiles. Vicker microhardness testing, transmission electron microscope (TEM), and differential scanning calorimeter (DSC) were used to characterize the welds. Two different tempers of the alloy were used, a low overaged temper and a high overaged temper. A thorough comparison of the two different tempers was done. It was found that highly overaged aluminum 7449 tempers show better properties for friction stir welding. A heat gradient along with a high conducting plate (Cu) used at the bottom of the run, resulted in welds with two separate microstructures in the nugget. Due to the microstructure at the bottom of the nugget, higher strength than the base metal is observed. Furthermore, the effects of natural aging and artificial aging were studied to understand re-precipitation. Large improvements in strength are observed after natural aging throughout the welds, including improvements in the HAZ.
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Altenkirch, Jens. "Stress engineering of friction stir welding : measurement and control of welding residual stresses." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.505389.
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Friction stir welding (FSW) is a maturing welding technique using a rotating tool for simultaneous heating and stir deforming th~ material interface to form a solid bond. Significant tensile residual stresses (RS) and component distortion may be produced even with optimized FSW parameters. Recent stress engineering techniques such as global mechanical or roller tensioning may reduce tensile RS and distortion. This dissertation reports on the first systematic investigation into the efficiency of insitu global mechanical tensioning (IS GMT) as well as roller tensioning applied in-situ (ISRT) and post welding (PWRT) for mitigation of tensile RS and plate distortion in high strength aluminium alloy plates joined by FSW. The techniques were evaluated by measuring the distribution of RS across the weld-line by means of neutron and synchrotron X-ray diffraction as well as' the levels of plate distortion. In each case the weld microstructure and hardness distribution were characterised. The data were rationalised against the ISGMT load and roller tensioning down force respectively. The results have shown that ISGMT and PWRT significantly mitigate longitudinal tensile RS and component distortion. ISGMT was found to decrease the tensile RS by an amount approximately equal to that of the load applied. Consequently, a stress free weld is produced with an ISGMT load equal to the magnitude of the weld-line RS in the as-welded condition~ PWRT decreases the tensile RS as the rolling down force increases and significant compression may be introduced once a certain magnitude is exceeded. ISRT, at least for the range tested, was found to be less effective. The component distortion reduced along with RSÇ'ú mitigation. No effects on the microstructure or hardness distribution due to mechanical stress engineering were observed. Furthermore, it was demonstrated that in order to make accurate stress measurements by diffraction, the effect of precipitation on the stress free lattice spacing must be taken into account for age hardening alloys. In order to complete this study an automated robotic sample manipulation system was developed. Finally, the degree of stress relaxation occurring on cutting down large welds was evaluated by progressively shortening test welds and determining the RS for each length. The amount of stress relaxation for each weld follows the same behaviour and appears to depend on the width of the tensile weld zone only.
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Olsen, Eric Michael. "Friction Stir Welding of High-Strength Automotive Steel." BYU ScholarsArchive, 2007. https://scholarsarchive.byu.edu/etd/951.
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The following thesis is a study on the ability to create acceptable welds in thin-plate, ultra-high-strength steels (UHSS) by way of friction stir welding (FSW). Steels are welded together to create tailor-welded blanks (TWB) for use in the automotive industry. Dual Phase (DP) 590, 780, and 980 steel as well as Transformation-Induced Plasticity (TRIP) 590 steel with thicknesses ranging from 1.2 mm to 1.8 mm were welded using friction stir welding under a variety of processing conditions, including experiments with dissimilar thicknesses. Samples were tested under tensile loads for initial determination if an acceptable weld had been created. Acceptable welds were created in both TRIP 590 and DP 590 at speeds up to 102 centimeters-per-minute. No acceptable welds were created in the DP 780 and DP 980 materials. A series of microhardness measurements were taken across weld samples to gain understanding as to the causes of failure. These data indicate that softening, caused by both excessive heat and insufficient heat can result in weld failure. Not enough heat causes the high concentration of martensite in these materials to temper while too much heat can cause excessive hardening in the weld, through the formation of even more martensite, which tends to promote failure mode during forming operations. Laser welding is one of the leading methods for creating tailor-welded blank. Therefore, laser welded samples of each material were tested and compared to Friction Stir Welded samples. Lower strength and elongation are measured in weld failure while the failure location itself determines the success of a weld. In short, an acceptable weld is one that breaks outside the weld nugget and Heat Affected Zone (HAZ) and where the tensile strength (both yield and ultimate) along with the elongation are comparable to the base material. In unacceptable welds, the sample broke in the weld nugget or HAZ while strength and elongations were well below those of the base material samples.
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Hartman, Trent J. "Friction Stir Spot Welding of Ultra-High Strength Steel." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3302.
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Friction stir spot welding (FSSW) is quickly becoming a method of interest for welding of high strength steel (HSS) and ultra high strength steel (UHSS). FSSW has been shown to produce high quality welds in these materials, without the drawbacks associated with fusion welding. Tool grade for polycrystalline cubic boron nitride (PCBN) tools has a significant impact on wear resistance, weld quality, and tool failure in FSSW of DP 980 steel sheet. More specifically, for a nominal composition of 90% CBN, the grain size has a significant impact on the wear resistance of the tool. A-type tools performed the best, of the three grades that were tested in this work, because the grain size of this grade was the finest, measuring from 3-6 microns. The effect of fine grain size was less adhesion of DP 980 on the tool surface over time, less abrasive wear, and better lap shear fracture loads of the welds that were produced, compared to the other grades. This is explained by less exposure of the binder phase to wear by both adhesion and abrasion during welding of DP 980. A-type tools were the most consistent in both the number of welds per tool, and the number of welds that reached acceptable lap shear fracture loads. B-type tools, with a bimodal grain size distribution (grain size of 4 – 40 microns) did a little bit better than C-type tools (grain size of 12-15 microns) in terms of wear, but neither of them were able to achieve consistent acceptable lap shear fracture load values after the first 200 welds. In fact only one out of five C-type tools was able to produce acceptable lap shear fracture loads after the first 100 welds.
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De, Backer Jeroen, and Bert Verheyden. "Robotic Friction Stir Welding for Automotive and Aviation Applications." Thesis, University West, Division of Production Engineering, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-2171.
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Friction Stir Welding (FSW) is a new technology which joins materials by using frictional heat. Inthe first part of this thesis, a profound literature study is performed. The basic principles, therobotic implementation and possibilities to use FSW for high strength titanium alloys areexamined. In the next phase, a FSW-tool is modelled and implemented on an industrial robot in arobot simulation program. Reachability tests are carried out on car body parts and jet engineparts. By using a simulation program with embedded collision detection, all possible weldinglocations are determined on the provided parts. Adaptations like a longer FSW-tool and amodified design are suggested in order to get a better reachability. In different case studies, thenumber of required robots and the reduction of weight and time are investigated and comparedto the current spot welding process.
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Hunt, Johnathon Bryce. "Defect Detection in Friction Stir Welding by Measureable Signals." BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8676.
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Friction stir welding (FSW) is an advantageous solid-state joining process, suitable for many materials in the energy, aerospace, naval and automotive industries. Like all other welding processes, friction stir welding requires non-destructive evaluation (NDE). The time and resources to preform NDE is expensive. To reduce these costs, nontraditional NDE methods are being developed for FSW. Spectral based defect recognition uses the forces during the welding process to validate weld quality. Although spectral NDE methods have shown promise as an alternative NDE processes, many research welding speeds do not correspond to manufacturing speeds, nor do they explain the relationship between the spectral data and the process. The purpose of this work is to explore the possibility of acquiring additional information about the defect. Namely the defect’s type, location, and magnitude. In this study, welds with “wormhole” defects were produced at 2000, 2500 and 3000 mmpm in 5754 aluminum. The welding process forces and torque were measured and analyzed spectrally. The welded plates were then imaged with x-ray photography, a validated NDE method. It was found that low frequencies (0 – 4 Hz) in the y & z force signals correlate with defect presence in high speed FSW. In addition, the strong correlation between the spectral data and the presence of a defect allowed for defect magnitude predictions. Linear fits were applied to the defect measurements and the spectral data. Large error inhibits the wide use of this prediction method.
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Karogal, Nikhil Uday. "Microstructural evolution in friction stir welding of Ti-6AI-4V." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1407152313.
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Owen, Charles Blake. "Two Dimensional Friction Stir Welding Model with Experimental Validation." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1200.pdf.
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Larsen, Brigham Ammon. "Increasing the Manufacturing Readiness of Refill Friction Stir Spot Welding." BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8513.
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Refill friction stir spot welding (RFSSW) is an emerging technology, capable of joining thin sheets of aluminum alloys. The present thesis comprises two studies which were conducted to address two challenges faced by RFSSW: the long cycle time traditionally associated with welding and the poor life of existing RFFSW tools. In the first study, welds were made in AA5052-H36, at various cycle times and with various process parameters. It was shown that RPM, cycle time, and material thickness, all have an effect on the machine response. Decreasing RPM or weld duration leads to increased force and torque response during welding. Welds with cycle times below one second were successfully made without severely impacting joint quality, suggesting that prior work may have been limited by machine capabilities rather than by phenomena inherent to the process. On average, the sub-one second welds caused a peak probe force of 9.81 kN, a plunge torque of 26.3 N*m, and showed average lap-shear strengths of 7.0kN; compared to a peak probe force of 5.14 kN, a plunge torque of 17.3 N*m, and lap-shear strength of 6.89kN for a more traditional four-second welding condition. In the second study, the life of a steel toolset was quantified as consecutive welds were made in AA5052-H36 until the toolset seized from material accumulation/growth. At a one-second welding condition, the toolset was only capable of producing 53 welds before seizure. At a two-second welding condition, the toolset was only capable of producing 48 welds. In subsequent temperature experiments, thermocouples were embedded into welding coupons at various locations near weld center, allowing novel temperature data to be collected for welds with varying cycle times and parameters. The collected temperature data shows that as cycle time increases, so does weld temperature. At weld center, temperatures in excess of 500°C were observed in welds with 4 second durations. At these temperatures, Fe-Al intermetallic growth is anticipated as a mechanism limiting the tool life observed. The results suggest that steel is not an appropriate choice for RFSSW tools, and future evaluation of other materials is merited.
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Pew, Jefferson W. "A Torque Based Power Input Model for Friction Stir Welding." BYU ScholarsArchive, 2006. https://scholarsarchive.byu.edu/etd/1100.
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For decades models have been developed for predicting the size of the weld nugget and heat affected zones in fusion welded structures. The basis for these models is the welding heat input, which is fairly well understood for most arc welding processes. However, this traditional approach is not as straightforward for Friction Stir Welding (FSW). To date, there is no definitive relationship to quantify the heat input for FSW. An important step to establish a heat input model is to identify how FSW process parameters affect weld power. This study details the relationship between FSW process parameters and torque for three different aluminum alloys: 7075, 5083 and 2024. A quantitative weld power and heat input model is created from the torque input. The heat input model shows that decreasing the spindle speed or increasing the feed rate significantly decreases the heat input at low feed rates. At high feed rates, feed rate and spindle speed have little effect on the heat input. Process parameter versus heat input trends are verified by measurements of the weld heat affected zones. In addition, this study outlines and validates the use of a variable spindle speed test for determining torque over a broad range of parameters. The variable spindle speed test provided significant improvements over previous methods of determining torque as this new method enabled the torque to be modeled over a broad range of parameters using a minimum number of welds. The methods described in this study can be easily used to develop torque models for different alloys and materials.
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Fuller, Michael D. "Friction stir processing and fusion welding in nickel aluminum propeller bronze." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2006. http://library.nps.navy.mil/uhtbin/hyperion/06Mar%5FFuller.pdf.
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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, March 2006.Thesis Advisor(s): Terry R. McNelley. "March 2006." Includes bibliographical references (p. 69-70). Also available in print.
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Taysom, Brandon Scott. "Temperature Control in Friction Stir Welding Using Model Predictive Control." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/6027.
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Temperature is a very important process parameter in Friction Stir Welding (FSW), but until lately active control of temperature has not been practiced. Recently, temperature control via a PID controller has proven to be effective. Model Predictive Control (MPC) is a control method that holds promise, but has not been attempted in FSW before. Two different model forms are developed for MPC and are evaluated. The first is a simple first-order plus dead time (FOPDT) model. The second is the Hybrid Heat Source model and is more complex; it combines the heat source method and a 1D discretized thermal model of the FSW tool. Model parameters were determined by fitting model predictions to actual weld data. The models were evaluated for their performance in modeled and unmodeled disturbances once the process was already at a quasi steady state condition and also were evaluated for control immediately after plunge. The FOPDT based MPC controller has very good performance and was comparable in performance to previously proven and well-tuned PID controllers. For small modeled disturbances the FOPDT controller settled within 1°C of the setpoint in 10s with almost no oscillations and only 2°C of overshoot. For large unmodeled disturbances, the FOPDT controller settled within 1°C of the setpoint in 30s with no oscillations and 16°C of overshoot. For the same disturbances, the PID servo controller settled in 30s with no oscillations and 9°C of overshoot, and the PID regulator controller settled in 15s but had almost a full oscillation and 13°C of overshoot.The Hybrid Heat Source MPC controller and the PID regulator controller were also able to control temperature within 5°C of the setpoint immediately after the plunge during the highly transient portion of the weld, which previously had been assumed to be too difficult to control. The PID regulator controller had a high degree of variability between the two runs (a settling time of 10s and 30s, and .5 and 4.5 oscillations before settling), but settled quickly and once settled was able to hold the temperature within 2°C of the setpoint. The HHS MPC controller on the other hand had far fewer oscillations (0 and 1 oscillation) before settling, but could only hold the temperature within 5°C of the setpoint. Both of these controllers performed far better than the FOPDT MPC and PID servo controllers.
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Wright, Arnold David. "Effective Temperature Control for Industrial Friction Stir Technologies." BYU ScholarsArchive, 2021. https://scholarsarchive.byu.edu/etd/9134.
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Systematic investigation of the Friction Stir Welding (FSW) process shows that a fixed rotational velocity and feed rate may not yield uniform mechanical properties along the length of a weldment. Nevertheless, correlations between process parameters and post-weld material properties have successfully demonstrated that peak temperature and cooling rate drive post-weld properties. There have been many reported methodologies for controlling friction stir welding, with varying degrees of cost to implement and effectiveness. However, comparing data from uncontrolled FSW of AA 6111-T4 sheet with controlled FSW at temperatures ranging from 375 °C to 450 °C demonstrates that a simplified methodology of a single-loop PID controlling with spindle speed may be used to effectively control temperature. This methodology can be simply used with any machine that already has the ability to actively control spindle speed, and has been previously shown to be able to be auto-tuned with a single weld. Additionally, implementation of this method compared to uncontrolled FSW in AA6111 at linear weld speeds of 1-2 meters per minute showed improved mechanical properties and greater consistency in properties along the length of the weld under temperature control. Further results indicate that a minimum spindle rpm may exist above which tensile specimens did not fracture within the weld centerline, regardless of temperature. This work demonstrates that a straight-forward, PID-based implementation of temperature control at high weld rates can produce high quality welds with auto-tuned gains. This method also shows promise in application to other processes in the Friction Stir family, and preliminary results in an application to the Additive Friction Stir Deposition (AFSD) process are also presented.
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Dansie, Ty Samual. "Simulation of the Inertia Friction Welding Process Using a Subscale Specimen and a Friction Stir Welder." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/6749.
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This study develops a method to simulate a full-scale inertia friction weld with a sub-scale specimen and modifies a direct drive friction stir welder to perform the welding process. A torque meter is fabricated for the FSW machine to measure weld torque. Machine controls are modified to enable a force control during the IFW process. An equation is created to measure weld upset due to deflection of the FSW machine. Data obtained from a full-scale inertia friction weld are altered to account for the geometrical differences between the sub-scale and full-scale specimens. The IFW are simulated with the sub-scale specimen while controlling spindle RPM and matching weld power or weld RPM. The force used to perform friction welding is scaled to different values accounting for specimen size to determine the effects on output parameters including: HAZ, upset, RPM, torque, power and energy of the weld. Increasing force has positive effects to upset, torque, power and energy of the welds, while reducing the size of the HAZ.
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Reese, Gordon Scott. "Analytical Thermal Model of Friction Stir Welding with Spatially Distributed Heat Source." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3328.
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Friction stir welding (FSW) has been studied extensively for the past two decades. Thermal modeling has been of particular interest, as the quality of the weld is dependent upon the temperature history of the work piece during the process. Since direct temperature measurements of the welded zone are not possible, an analytical model was developed to predict the temperature in this area. This model requires parameters that cannot be easily experimentally determined, so a best fit for these parameters was acquired via regression analysis by comparing the model to experimental data acquired outside of the weld zone. The model was then validated by comparing it to additional temperature data, not including the data used for regression analysis.
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Pemberton, W. Patrick. "Predictive relationships in friction stir processing of nickel-aluminum bronze." Thesis, Monterey, Calif. : Naval Postgraduate School, 2005. http://handle.dtic.mil/100.2/ADA441369.
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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, September 2005.Thesis Advisor(s): Terry R. McNelley. "September 2005." Includes bibliographical references (p. 45-47). Also available in print.
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Thompson, Brian Thomas. "Tool Degradation Characterization in the Friction Stir Welding of Hard Metals." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1273602433.
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Ross, Kenneth A. "Investigation and Implementation of a Robust Temperature Control Algorithm for Friction Stir Welding." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3919.
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In friction stir welding, the temperature of the process zone affects the properties of the resulting weld and has a dramatic effect on tool life in PCBN (polycrystalline cubic boron nitride) tools. Therefore an active control system that changes process parameters to control weld temperature is desirable. Mayfield and Sorensen proposed a two-stage control model that contains an inner loop that controls the spindle speed to keep power constant and an outer loop for setting the desired power based on weld temperature. This work contains the analysis and implementation of a temperature control method based on their work. This research shows that power input to the stir zone leads tool temperature. Due to the inertia associated with the spindle, power control is best achieved by commanding torque rather than spindle speed. Heat transfer in the tool and stir zone is explored and analytical models are developed. It is shown that the temperature response to power is nonlinear. Nevertheless a first-order approximation with time delay is sufficient to select functional controller gains for a PID controller. Standard manual PID tuning techniques can be used to achieve a desired rise time, settling time and overshoot. Gains for an H-13 tool steel FSW tool were tuned to produce a rise time of approximately 7 seconds, settling time of approximately 30 seconds and overshoot of approximately 30%. Welds were run using these gains in various plate thicknesses, commanded temperatures, backing plates and feed rates. In all cases temperature control functioned properly and the commanded temperature was held with a standard deviation of less than one degree Celsius. Similar results are presented for welds run using PCBN tools.
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Oliphant, Alma H. "Numerical Modeling of Friction Stir Welding: A Comparison of Alegra and Forge3." Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd417.pdf.
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Prymak, David John. "A New Method of Measuring Flow Stress for Improved Modeling of Friction Stir Welding." BYU ScholarsArchive, 2021. https://scholarsarchive.byu.edu/etd/9081.
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Deficiencies in friction stir welding (FSW) numerical modelling are identified. Applicability of flow stress data derived from hot compression, hot torsion, and split Hopkinson bar testing methods is assessed. A new method of measuring flow stresses in the stir zone of a friction stir welding tool is developed. This test utilizes a non-consumable flat-faced cylindrical tool of different geometries that induces a vertical and rotational load on the material of interest. A constant vertical load and rpm value is used for each test yielding the resulting motor torque and temperature generation to define the material response. Experimental samples are cross-sectioned, polished, and etched to reveal the material flow behavior below the tool. A viscosity-based model is used to quantify the shear stress and rim shear rate present in the shear layer below the tool. This test is referred to as the high-pressure shear (HPS) experiment. A parameter window is developed for two alloys of interest, AA6061-T6 and AA2219-T87 and results are reported. The HPS experiments yields flow stress estimates that are pressure and strain rate dependent. Different tool geometries are explored to understand the impact of the "dead zone"at the center axis of the tool. When compared to hot compression and hot torsion the HPS flow stress datasets trend 20-86 % lower across the two materials tested.
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Saunders, Nathan David. "High Speed Friction Stir Spot Welding on DP 980 Steel:Joint Properties and Tool Wear." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3003.
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With the desire to improve passenger safety and fuel efficiency, Ultra High Strength Steels (UHSS) have been developed for use in the automotive industry. UHSS are high strength steels with high ductility and strength. DP 980 is one of these UHSS being applied in automobile manufacturing. DP 980 is difficult to join with Resistance Spot Welding (RSW) because of the high carbon content and alloying in this material. The weld becomes brittle when it solidifies during the welding process. With the desire and motivation of widely using UHSS, new welding processes are needed to be developed in order to effectively join DP 980. Friction Stir Spot Welding (FSSW) is a developing welding process aimed to replace RSW in the automotive industry because of its ability to join materials at a lower temperature. Currently the welding loads of the tools are higher than 2000 pounds, ranging from 3,000 to 5,000 pounds, which exceeds the limit of the welding robots in the automotive factories. It is proposed that the welding loads can be reduced by increasing the spindle speed of the FSSW tool. Other focuses in the research include increasing the life of the tool and developing acceptable welding parameters for High Speed FSSW. The experimental work done for this thesis provided support that weld strength can be obtained at levels above the acceptable standard for DP 980 material (greater than 2400 pound lap shear fracture load for 1.2 mm material) while keeping the vertical load on the welding machine spindle below 2000 lbs.
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Failla, David Michael II. "Friction Stir Welding and Microstructure Simulation of HSLA-65 and Austenitic Stainless Steel." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243969697.
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Gonser, Matthew J. "Microstructure Evolution and Material Flow Behavior in Friction-Stir Welded Dissimilar Titanium Alloys." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1268138325.
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Rosemark, Brian P. "Friction stir processing parameters and property distributions in cast nickel aluminum bronze." Thesis, Monterey, Calif. : Naval Postgraduate School, 2006. http://bosun.nps.edu/uhtbin/hyperion.exe/06Dec%5FRosemark.pdf.
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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, December 2006.Thesis Advisor(s): Terry R. McNelley, Srinivasan Swaminathan. "December 2006." Includes bibliographical references (p. 49-50). Also available in print.
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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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Lasley, Mark J. "A Finite Element Simulation of Temperature and Material Flow in Fricton Stir Welding." BYU ScholarsArchive, 2004. https://scholarsarchive.byu.edu/etd/220.
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The purpose of this research was to use the Transvalor S.A. product, Forge3, to develop a finite element simulation of the friction stir welding process that improves the predictability of temperature evolution and material flow within the plunge portion of the process. Previous modeling created more heating within the billet than experimental results, probably due to the simplification of the simulation with adiabatic boundary conditions. More realistic tooling temperatures were included in this model as these affect heat evolution which is a determining factor in microcrystalline growth. These results were validated by experimental efforts using a billet and tooling instrumented with thermocouples used to evaluate the temperatures at specific locations over time. Simulation results were compared with previous experiments to validate the predicted material flow.
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Handyside, Alan Bruce. "Dual-function fixture design for dynamic testing of automotive bumper/crash-box case study utilizing friction stir welding." Thesis, Wichita State University, 2011. http://hdl.handle.net/10057/3957.
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Recent advancements in friction stir welding (FSW) technology and pin (probe) tool design for aluminum have made FSW applications in aerospace and automotive structures quite attractive. FSW has the potential for better fit, form and function when compared to fusion welding. The aim of this research was to design, develop and fabricate a fixture to meet the requirement of a standard automotive impact test on an FSW bumper/crash-box assembly. A fusion welded bumper/crash-box design was provided to Wichita State University (WSU) by the General Motors Corporation (GM). For this case study, the bumper design was not changed, but the existing crash box was altered to satisfy two FSW assembly designs, incorporating unique lap and hybrid welds for the closeout area at each end of the bumper. Both designs use a common butt weld along a nested interface between the crash box and the bumper. The goal of this test fixture was to facilitate a dynamic vehicle test on FSW bumpers and compare the test results to that of fusion-welded bumpers.
Functional use of FSW in bumper design was to be determined through this case study. Since the test fixture uses similar type welds as the bumper geometry, FSW was also incorporated into the test fixture design. Several design constraints related to vehicle testing, FSW and the University Impact Laboratory were met. Process simulation of dynamic forces on the bumper and test fixture welds, along with standard static analysis, were used for design verification. Parameter bounding and test coupons of FSW in aluminum were used to determine parent and weld material properties as well as optimum weld parameters for manufacturing the test fixture. Aluminum alloys 6063-T6, 6061-T6, 7050-T7451, concrete and structural fusion welded steel were selected for materials in the test fixture design. A linear bearing rail system was used to facilitate the gravity-fed drop tower and dynamically fed sled test functionsThesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering.
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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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Abbasi, Gharacheh Majid. "Microstructural Evaluation in Friction Stir Welded High Strength Low Alloy Steels." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/3099.
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Understanding microstructural evolution in Friction Stir Welding (FSW) of steels is essential in order to understand and optimize the process. Ferritic steels undergo an allotropic phase transformation. This makes microstructural evolution study very challenging. An approach based on Electron Backscattered Diffraction (EBSD) and phase transformation orientation relationships is introduced to reconstruct pre-transformed grain structure and texture. Reconstructed pre-transformed and post-transformed grain structures and textures were investigated in order to understand microstructural evolution. Texture results show that there is evidence of shear deformation as well as recrystallization in the reconstructed prior austenite. Room temperature ferrite exhibits well-defined shear deformation texture components. Shear deformation texture in the room temperature microstructure implies that FSW imposes deformation during and after the phase transformation. Prior austenite grain boundary analysis shows that variant selection is governed by interfacial energy. Variants that have near ideal BCC/FCC misorientation relative to their neighboring austenite and near zero misorientation relative to neighboring ferrite are selected. Selection of coinciding variants in transformed prior austenite Σ3 boundaries supports the interfacial-energy-controlled variant selection mechanism.
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Karki, Utsab. "Experimental and Numerical Study of High-Speed Friction Stir Spot Welding of Advanced High-Strength Steel." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5521.
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With the desire to lighten the frame while keeping or increasing the strength, Advanced High-Strength Steels (AHSS) have been developed for use in the automotive industry. AHSS meet many vehicle functional requirements because of their excellent strength and acceptable ductility. But joining AHSS is a challenge, because weldability is lower than that of mild steels. Friction stir spot welding (FSSW) is a solid state joining process that can provide a solution to the weldability issues in AHSS, but FSSW has not been studied in great detail for this application. In this work, Si3N4 tools were used for FSSW experiments on DP 980 steel with 1.2mm thickness. Joint strength was measured by lap shear tension testing, while thermocouples were used for the temperature measurements. A finite element model was developed in order to predict material flow and temperatures associated with FSSW. Since a 3D model of the process is very time consuming, a novel 2D model was developed for this study. An updated Lagrangian scheme was employed to predict the flow of sheet material, subjected to the boundary conditions of the fixed backing plate and descending rotating tool. Heat generation by friction was computed by including the rotational velocity component from the tool in the thermal boundary conditions. Material flow was calculated from a velocity field while an isotropic, viscoplastic Norton-Hoff law was used to compute the material flow stress as a function of temperature, strain and strain rate. Shear stress at the tool/sheet interface was computed using the viscoplastic friction law. The model predicted welding temperatures to within 4% of the experiments. The welding loads were significantly over predicted. Comparison with a 3D model of FSSW showed that frictional heating and the proportion of total heat generated by friction were similar. The position of the joint interface was reasonably well predicted compared to experiment.
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Sanderson, Samuel C. "The Effect of Friction Stir Welding Process Parameters on Charpy V-Notch Impact Toughness in HSLA-65." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3745.
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HSLA-65 steel (6.4 mm thick) was friction stir welded at various welding speeds and spindle speeds. Varying weld parameters provided a range of heat inputs. Impact toughness was evaluated as a function of the different weld parameters and corresponding weld heat inputs. Charpy V-Notch (CVN) tests were conducted in parent material and at both the weld nugget centerline and heat-affected zone (HAZ) locations. The upper shelf CVN impact energy of the weld nugget was above that of the base metal for all weld parameters. The upper shelf impact toughness in the HAZ was largely unaffected by changing weld parameters. The nil-ductility transition (NDT) temperature in the weld nugget increased with increasing heat input. The toughness, with respect to the ductile-to-brittle transition, was negatively affected by the increase in heat input. The NDT temperature in the HAZ did not correlate with heat input. The microstructures and microhardness data were examined. Aspects of variation in the impact energy results were identified as the inhomogeneity of the weld microstructure and the placement of the V-notch. Weld nugget microstructures were more inhomogeneous than base metal. Hardness results showed varying values of hardness from the weld crown to the root, transversely across the weld, and longitudinally along the length. Variation due primarily to the inhomogeneity of the weld microstructure is compounded by the location of the V-notch.
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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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Sterling, Colin J. "Effects of Friction Stir Processing on the Microstructure and Mechanical Properties of Fusion Welded 304L Stainless Steel." Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd440.pdf.
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Kennard, Kirtis Frankland. "A Simple Method for Evaluating Wear in Different Grades of Tooling Applied to Friction Stir Spot Welding." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5529.
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In this study tools consisting of a 5mm cylindrical pin and a 12mm shoulder held by a simple tool holder were used to compare the wear of 11 tooling materials. The objective was to determine if using these tools in a spot welding configuration to simulate friction stir welding could differentiate the potential performance of tooling materials. All tools were made of varying percentages of polycrystalline cubic boron nitride (PCBN), tungsten (W) and rhenium (Re). The materials are referred to herein as GV1, GV2, G1, G2, G3, G4, G5, G6, G7, G8 and G9.The tools were run to 205 welds if they did not fracture first. The grades averaged the following quantities of welds before fracture failure GV-1:0; GV-2:200; G1:82; G2:204; G3:205; G4:205; G5:96; G7:102.73; G8:21.2; G9:38.5. Of the tools that ran the full 205 welds without chipping, the average calculated volume loss, which was the best indication of wear, was as follows G2:1.83%; G3:2.53%; G4:2.41%; G5:1.93%; and G7:2.30%.The study showed that G2 had the least wear and G6 had the most wear, of those tools that completed all 205 spot welds. Fracture was the failure mode of all grades with over 70% CBN content. It was found that small CBN grain size was not correlated to better wear performance, as has been seen in a prior study.
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Ivanov, Rosen. "The effect of friction stir welding on the microstructure and mechanical properties of a third generation Al-Cu-Li alloy." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=110517.
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The effect of friction stir welding on the microstructure, precipitation, mechanical properties, and tensile fracture has been studied. Friction stir welding has been applied to a third generation Al-Cu-Li alloy, the AA2199, in the T3 condition. Post weld heat treatment (PWHT) to the T8 condition, was carried out to artificially age the welds and improve mechanical properties. Welds were characterised using field emission scanning electron microscopy (FE-SEM) with electron channeling contrast imaging (ECCI), differential scanning calorimetry (DSC), micro-hardness, and tensile testing. Welds created with tool rotation speed of 877RPM showed ultimate tensile strength level of 93% of base metal in the T8, an elongation of 6% at fracture, and microhardness values ranging between 120-140 HV across the welds. The ability of welds to gain in hardness and strength during PWHT has been linked to the limited formation of large scale precipitates which act as sinks for alloying elements.L'effet du soudage par friction-malaxage sur la microstructure, la precipitation, les propriétés mécaniques et la rupture par traction ont été étudiés. Le soudage par friction-malaxage a été appliqué à une troisième génération d'alliage d'Al-Cu-Li, le AA2199-T3. Un traitement thermique après soudage (PWHT) sur l'alliage AA2199-T8 a été réalisé pour vieillir les soudures artificiellement et en améliorer les propriétés mécaniques. Les soudures ont été caractérisées par microscopie électronique à balayage (FE-SEM), par imagerie en contraste cristallographique (ECCI), par calorimétrie différentielle à balayage (DSC) et par des essais de micro-dureté et de traction. Les soudures créées avec une vitesse de rotation d'outil de 877RPM ont montré une limite à la rupture de 93% par rapport la plaque de depart, un allongement à la rupture de 6% , et des valeurs de microdureté variant entre 120 à 140 HV dans les soudures. Le gain en dureté et en résistance du matériau dans les zones soudées au cours du traitement thermique PWHT est lié à la formation à grande échelle de précipités absorbant les éléments d'alliage.
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Tribe, Allan M. "Study on the Fracture Toughness of Friction Stir Welded API X80." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3740.
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High strength low alloy (HSLA) steels have been developed to simultaneously have high yield strength and high fracture toughness. However, in practical applications steel must be welded. Traditional arc welding has proven detrimental to the fracture toughness of HSLA steels. Friction stir welding has recently shown mixed results in welding HSLA steels. The range of welding parameters used in these recent studies however has been very limited. With only a few welding parameters tested, the effect of spindle speed, travel speed, and heat input on the fracture toughness of friction stir welded HSLA steel remains unknown. To understand how the friction stir welding process parameters affect fracture toughness, double sided welds in API X80 were performed and analyzed. Results show that at room temperature friction stir welded API X80 exceeded industry minimum fracture toughness requirements in both the API Standard 1104 and DNV-OS-F101 by 143% and 62%, respectively. The process parameters of spindle speed and HI have been shown to effectively control the fracture toughness of the stir zone. Relationships have been established that show that fracture toughness increased by 85% when spindle speed decreased by 59% and heat input decreased by 46%.
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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.