Papers by Keyword: Friction Stir Spot Welding

Abstract: In order to evaluate the corrosion fatigue property of dissimilar joint by the simultaneous fatigue-corrosion test, an original compact shear fatigue test machine has been developed and installed in the combined cycle corrosion equipment. The material used were an innovative ultra-high strength steel (i-UHSS) with the ultimate strength of 1.5 GPa & large elongation of 20 % and an innovative Al-Mg alloy with high ductility. The dissimilar lap joints were fabricated by resistance spot welding (RSW) or refill friction stir spot welding (RFSSW). An innovative adhesive was also employed for producing the weld-bonded (WB) joints. An accelerated corrosion condition conducted in this research was the climate of high temperature & high humidity. The natural corrosion fatigue tests were also performed outdoor on Miyakojima Island in Japan and indoor in an air-conditioned room. The accelerated corrosion fatigue tests suggest that the corrosion fatigue property of the dissimilar WB joint joined by RSW seems to be better than that of the WB joint joined by RFSSW because of the difference in the area of adhesive interface. In addition, it is considered that the crack would propagate in the adhesive interface and then lap joint might break suddenly after achieving the crack to the circumference of joint interface produced by RSW or RFSSW. Moreover, it can be concluded that the accelerated corrosion condition employed in the research seems to be an appropriate condition for examining the corrosion fatigue property of lap joint in the climate of high temperature and high humidity.

Abstract: An artificial neural network (ANN) system was created to analyze and simulate the relationship between process parameters of dissimilar weld joints of Aluminum alloy 6061 (AA60061) and pure copper and their resulting mechanical properties. In this study, 2.2 mm thick Aluminum Alloy 6061 and 1.4 mm thick pure copper lap joints are welded using friction stir spot welding (FSSW) process. Tensile-shear tests were performed to evaluate the mechanical characteristics of the lap joints. The welding process parameters are tool speed, plunge depth, and dwell weld time. Optimum friction stir spot welding (FSSW) parameters are identified to achieve the maximum shear load for Aluminum alloy (AA 6061) and pure copper lap joints. This is accomplished at a rotational speed of 2000 rpm for a duration of 20 seconds, with a plunge depth of 0.2 mm. At 15s dwell time and 2000 rpm tool speed, the shear load increases with increasing plunge depth. The best regression neural network that has the least mean squared error of 0.10192 and coefficient of correlation of 0.85033 is the model of 5 neurons in the hidden layer of the system

Abstract: Friction stir spot welding as a solid state processing technique is used to join dissimilar and similar metals, composites and polymers. This study illustrates the implementation of friction stir spot welding (FSSW) on additive manufactured nylon-based composites with chopped carbon fibre reinforcements. The purpose of this study is to employ FSSW technique for joining additive manufactured carbon fibre composites. The utilization of pinless tool serves a crucial function in the formation of sound welded joints. The joining process consists of two mechanisms: the piercing and melting of the sheets and the adhesive bonding during the re-solidification. As a result of the FSSW process, the joints indicate a decent mechanical performance with a lap shear failure force (LSFF) of about 250N.

Abstract: Dissimilar metal lap joining of A5052 aluminum alloy plate and C1100 pure copper plate was performed by using friction stir spot welding. The rotating welding tool, which was composed of a probe part and a shoulder part, was plunged from the aluminum alloy plate which was overlapped on the copper plate, and residual aluminum alloy thickness under the probe part of the welding tool after plunging of the welding tool was controlled in the range from 0 mm to 0.4 mm. The strength of the welding interface was evaluated by using tensile-shear test. Microstructure of the welding interface was examined by using an optical microscope and a field emission scanning electron microscope. The welding was achieved at the residual aluminum alloy thickness under the probe part of the welding tool below 0.3 mm. The welded area was formed at aluminum alloy/copper interface located under the probe part of the welding tool, and its width increased with decreasing the residual aluminum alloy thickness. A characteristic laminate structure was produced in the copper matrix near the welding interface. In the joint fabricated at the residual aluminum alloy thickness below 0.1 mm, hook of Cu was formed at edge of the welded area. The fracture did not occur at the welding interface. A remarkable improvement in strength was observed in the joint fabricated at the residual aluminum alloy thickness below 0.1 mm. The formation of laminate structure and hook is considered to result in joint strength improvement.

Abstract: Zink (Zn) in galvanized steel has a positive effect on improving the properties of the dissimilar metals weld between aluminum alloy and galvanized steel. Its distribution is important to be evaluated. The aim of this work is to investigate the effect of rotation speed and dwell time on the Zn distribution of the friction-stir-spot-welded (FSSW) dissimilar metals between aluminum alloy and galvanized steel. FSSW was subjected to 3 mm thick of Aluminum and 1 mm thick of galvanized steel with a plunge depth of 2.7 mm and a penetration rate of 0.9 mm/s. High strength steel (HSS) with a hardness of 70 HRC and a diameter of 12 mm was used as FSSW tool. Tool rotation was varied at 1000 rpm, 1200 rpm, 1600 rpm, and 2000 rpm while dwell time was varied of 3 s, 5 s, and 7 s. A Scanning Electron Microscope (SEM) was performed to reveal the Zn distribution after cross-sectioning, polishing, and etching. During the FSSW process, the heat was generated, Zn softened, and carried away by the materials flow due to tool rotation. Both the rotation speed and the dwell time played a role in increasing the distance and the amount of Zn flow in the welded zone. FSSW process in dissimilar metals between aluminum and galvanized steel formed the unique pattern of Zn distribution.

Abstract: In an initiative to reveal the property of welded joint, investigation and assessment of the welding parameters in friction stir spot welding (FSSW) was carried out. In this study, the AA5052-H112 sheets with 2mm thickness was welded using cylindrical tool pin profile under different combinations of main process parameters i.e. spindle speed, tool depth, and dwell time. The fatigue test under cyclical load condition was performed to investigate the dynamic behavior of the welded joint. Failure mode analysis on the fracture of the weld joint after fatigue test was took also consideration. Finally, results from the test were evaluated using analysis of variance (ANOVA) to deter-mine statistically significant factors and associated percentage contribution together with the generation of main effects plots. From ANOVA results, dwell time had the highest influence on fatigue load with a PCR of 52.8%, followed by the spindle speed 37.1%, and then tool depth 6%.

Abstract: The quality of welded joints of FSSW is mainly dependent on the processing parameters while the main disadvantage of this process is the creation of an exit hole. Process parameters, namely tool dimensions, tool rotational speed, and stir time were changed and their impact on bond dimensions and weld strength was investigated using 2024-T3 Al Alloy. Macro- and microstructures of the welded samples were examined; shear fracture loads were measured and the optimum set of operation variables was determined. To decrease the exit hole of the first stage the present paper proposes a modified two-stage weld-refill process employing the same welding machine. In this work, this two-stage process was referred to as reversed friction stir spot welding (ReFSSW). In the second stage, a smaller pin was used and the shoulder diameter was designed such that to force the metal of the upper plate to flow towards the exit hole of the first stage decreasing its dimensions. The metal flow in the second stage was evaluated by examining the microstructure of the metal that filled the exit hole of the first stage. Thin stir zone was found around the pin of the second stage followed by thermomechanically affected zone consisting of grains elongated in the vertical direction. The proposed process resulted in smaller exit hole dimensions and consequently higher mechanical properties compared with the conventional single-stage FSSW.

Abstract: Surface finish accrued extra-production cost, reduced effective sheet thickness, stir zone galling, undesirable flash-root stress concentration and fatigue cracks are consequences of bulk expulsion of flash during friction stir spot welding of aluminum alloys. This paper attempts to cutback the abovementioned challenges and improves the weld strength (shear failure load) of friction stir spot welded joints of an Al alloy by adopting an integrated Grey relational analysis-entropy measurement method as a multi-objective optimization tool. Shear failure load, and expelled flash properties (pushed out length and thickness) are the three examined quality characteristics of the joint while tool rotational speed (600-1400 rpm), dwell time (3-6 s) and plunge depth (1.5-1.7 mm) are the studied process parameters. The experiment was planned via the use of Taguchi method whereas the entropy measurement method facilitated the identification of the precise weighting values required for the estimation of the unified grey relational grade. The failure load of the joint was maximized while both flash height and pushed-out length were minimized. The optimized shear failure load and flash properties were attained at a parameter setting of 1400 rpm rotational speed, 6 s dwell time and 1.5 mm plunge depth. The tool rotational speed was found to have the most significant effect and percentage contribution on the combined responses with 67.75%, followed by plunge depth (12.88 %) and dwell time (11.94 %) respectively. The validation results confirm the robustness of the entropy measurement-based multi-objective optimization as a tool for improving the quality responses of friction stir spot welds.

Abstract: This article presents an experimental investigation of the friction stir spot welding process in thin-walled plates by using a special HSS tool. A review of the literature dealing with the analyzed problem was conducted and the experimental setup for FSSW experiments was described. The experiments were carried out on non-ferrous 5754 aluminum alloy, copper M2 and brass CuZn37. Variations of experimental axial force were obtained.

Abstract: In the present study, we attempt to use powder of glass spheres filler and reinforce material in HDPE to produce composite structure and then evaluate its mechanical properties to study the effect of welding parameters and filler content on mechanical properties of HDPE. The effect of welding parameters (tool rotational speed, the plunge depth and the dwell time) on friction stir spot welding properties of high density polyethylene/glass spheres (hollow) polymer composites sheets was studied.