Optimization of Friction Stir Weld Joint Quality Using a Meshfree Fully-Coupled Thermo-Mechanics Approach

Abstract

Abstract:There is currently a need for an efficient numerical optimization strategy for the quality of friction stir welded (FSW) joints. However, due to the computational complexity of the multi-physics problem, process parameter optimization has been a goal that is out of reach of the current state-of-the-art simulation codes. In this work, we describe an advanced meshfree computational framework that can be used to determine numerically optimized process parameters while minimizing defects in the friction stir weld zone. The simulation code, SPHriction-3D, uses an innovative parallelization strategy on the graphics processing unit (GPU). This approach allows determination of optimal parameters faster than is possible with costly laboratory testing. The meshfree strategy is firstly outlined. Then, a novel metric is proposed that automatically evaluates the presence and severity of defects in the weld zone. Next, the code is validated against a set of experimental results for 1 /2" AA6061-T6 butt joint FSW joints. Finally, the code is used to determine the optimal advancing speed and rpm while minimizing defect volume based on the proposed defect metric.

Temperature and Stress Evaluation during Three Different Phases of Friction Stir Welding of AA 7075-T651 Alloy

“…e temperature keeps growing up at the same site until the shoulder comes in contact with the AA 7075 plate; subsequently, the maximum temperature skips to the corner zone between the pin and shoulder interfacial surfaces. At 12.1 sec the contact between tool and workpiece increased causing the temperature to grow up to its maximum value of 599°C around the shoulder-workpiece interface; this is due to the occurrence of complete contact between the workpiece and the tool; in addition, the plunging force and the torque granted to the tool were higher than the other steps, as described by Fraser et al [25]. Later on, the temperature decreased slightly and tended to be more stable in the dwell and traverse stages.…”

Main Issues in Quality of Friction Stir Welding Joints of Aluminum Alloy and Steel Sheets

“…Although they work were carried out on FSW of aluminum alloys, it provides general recommendations also for dissimilar FSW with steel. As pointed out in Figure 23, sound joints can be normally obtained by using a proper weld pitch range (it was in the range of 0.5 to 0.80 in the study by Fraser et al [56]), whereas different defects can appear outside this range. A low weld pitch (i.e., too high rotational speed or too low welding speed) gives rise to excessive heat inputs associated with an undesired metal plasticity, with ensuing defects such as flash, tunnel, voids, sticking of metals to pin tool surfaces, as well as excessive pin tool wear.…”

“…In fact, Al/steel FSW can often be optimized only by acting on rotational and welding speed without any careful handling of other welding parameters, which can be set based on experience and good sense. An example of how a preliminary study could be initially conducted can be well summarized by a study by Fraser et al [56]. They evaluate the combined effects of rotational and welding speed on the formation and kind of defects in terms of weld pitch (i.e., ratio of welding speed to rotational speed), Figure 23.…”

Recent Achievements in Rotary, Linear and Friction Stir Welding of Metals Alloys

“…In more detail, the contributions have concerned the following topics.The effect of cold rolling performed after friction stir welding (FSW) on the mechanical properties and formability of joints in AA5754-H114 aluminum alloy [1].The microstructure evolution of the welded joints of AA6082-T6 obtained using the bobbin friction stir welding process with a focus on grain refinement [2].The characteristic features of the entry and exit defects in the weld structure and formation mechanism of them during the BFSW process. The issue was investigated using stacked layers of multi-colored plasticine for the material flow detection [3].The thermo-structural analysis of material behavior, material flow, and defect generation during the friction stir butt-welding of 5083-O sheets [4].The characterization of the dissimilar friction stir weld of Ti-6242 S and Ti-54M in terms of microstructure, microhardness, fracture morphology, and material migrating from the retreating (RET) side to the advancing (ADV) one [5].The characterization of the interface of friction stir lap welding joints of 6082-T6 aluminum alloy and Q235A steel [6].The investigation of the microstructure evolution and properties response of a friction-stir-welded copper-chromium-zirconium alloy [7].The study of the influence of the process parameters on the vertical force generated during friction stir welding of AA6082-T6 aluminum alloy sheet blanks [8].The role of mechanical connection in friction stir keyholeless spot welding of AZ31B Mg alloy, Mg99.50, DP600, and non-zinc-coated DP600 lap welding [9].The application of a fully coupled thermo-mechanical model together with an enhanced friction law for the simulation of an FSW process with a cylindrical threaded pin tool [10].The identification of the chemical composition of etchant reagents for metallographic examination of the friction-stir welded A6082-T6 alloy [11].The study of an advanced meshfree computational framework to be used for the determination of optimal process parameters for the friction stir welding of an AA6061-T6 butt joint [12].The numerical modeling approach to the study of the linear friction welding of 30CrNiMo8 high strength steel Hero chain [13].…”

“…The study of an advanced meshfree computational framework to be used for the determination of optimal process parameters for the friction stir welding of an AA6061-T6 butt joint [12].…”