Parametric study of friction stir welding using elastic return

Friction stir welding (FSW) and friction stir spot welding (FSSW) techniques are becoming widely popular joining techniques because of their increasing potential applications in automotive, aerospace, and other structural industries. These techniques have not only successfully joined similar and dissimilar metal and polymer parts but have also successfully developed polymer-metallic hybrid joints. This study classifies the literature available on the FSW and FSSW of thermoplastic polymers and polymer composites on the basis of joining materials (similar or dissimilar), joint configurations, tooling conditions, medium conditions, and study types. It provides a state-of-the-art and detailed review of the experimental studies available on the FSW and FSSW between similar thermoplastics. The mechanical properties of FSW (butt- and lap-joint configurations) and FSSW weld joints depend on various factors. These factors include the welding process parameters (tool rotational speed, tool traverse speed, tool tilt angle, etc.), base material, tool geometry (pin and shoulder size, pin profile, etc.) and tool material, and medium conditions (submerged, non-submerged, heat-assisted tooling, cooling-assisted tooling). Because of the dependence on many factors, it is difficult to optimize the welding conditions to obtain a high-quality weld joint with superior mechanical properties. The general guidelines are established by reviewing the available literature. These guidelines, if followed, will help to achieve high-quality weld joints with least defects and superior mechanical properties. Apart from parametric-based studies, the statistical-based studies (e.g., analysis of variance (ANOVA)-based studies) are covered, which helps with the determination of the influential parameters that affect the FSW and FSSW weld joint strength. Also, the optimal ranges of the most influential process parameters for different thermoplastic materials are established. The current work on the development of general guidelines and determination of influential parameters and their operating ranges from published literature can help with designing smart future experimental studies for obtaining the global optimum welding conditions. The gaps in the available literature and recommendations for future studies are also discussed.

Summary This paper describes the possibility of optimum friction welding conditions being selected through adoption of a joining evaluation equation derived from friction welding behaviour as determined by the response surface method in welding tests of 12 mm dia. SUS304 stainless steel. Through initial analysis of the relationship between the welding behaviour and tensile strength of friction-welded joints in a multiple regression analysis, a joining evaluation equation for non-destructive estimation of joint performance is derived. The optimum welding conditions are next selected by the response surface method using the joining evaluation values determined by the joining evaluation equation as dependent variables and the friction welding conditions as independent variables. This procedure enables the optimum friction welding conditions to be determined without the need for tensile tests to be conducted. The optimum friction welding conditions determined by this procedure are friction pressure P1 = 30 MPa, upset pressure P2 = 170 MPa, friction time t1 =3.5 sec, and rotational speed N = 2425 rpm. These conditions enable a satisfactory joint efficiency ηf of 102.5% to be obtained.

Friction stir welding (FSW) is a solid-state welding technique in which the joint quality was predominantly subjected to heat formation throughout the metal welding process. The weld joint produced from FSW was better than the other fusion welding process. In this research, the base plates AA6101 and C11000 of 5 mm thickness were joined using the hardened oil-hardened nonshrinkable steel(OHNS) tool by the FSW method. The design of experiment (DOE) was used to optimize the input parameters such as tool rotational speed (rpm), feed rate (mm/min), and tool pin offset (mm) on output parameter ultimate tensile strength (UTS). The design of experiment (DOE) was carried out by employing a Taguchi L9 orthogonal array, three factors, and three levels for obtaining a quality joint with good strength. The results of nine trial runs from the Taguchi experimental approach were formulated and analyzed using the statistical tool analysis of variance (ANOVA) using MINITAB 19 software. ANOVA analysis was employed to find the contribution of the input parameters toward the output. The optimized input process parameters will help to create effective weld joints. This study revealed that tool pin offset towards softer metal at medium tool rotational speed would create joints with the highest UTS. Scanning Electron Microscope (SEM) was applied to investigate the structural changes in the FSW of Al-Cu joints.Friction stir welding (FSW) is a solid-state welding technique in which the joint quality was predominantly subjected to heat formation throughout the metal welding process. The weld joint produced from FSW was better than the other fusion welding process. In this research, the base plates AA6101 and C11000 of 5 mm thickness were joined using the hardened oil-hardened nonshrinkable steel(OHNS) tool by the FSW method. The design of experiment (DOE) was used to optimize the input parameters such as tool rotational speed (rpm), feed rate (mm/min), and tool pin offset (mm) on output parameter ultimate tensile strength (UTS). The design of experiment (DOE) was carried out by employing a Taguchi L9 orthogonal array, three factors, and three levels for obtaining a quality joint with good strength. The results of nine trial runs from the Taguchi experimental approach were formulated and analyzed using the statistical tool analysis of variance (ANOVA) using MINITAB 19 software. ANOVA analysis was employed to find the contribution of the input parameters toward the output. The optimized input process parameters will help to create effective weld joints. This study revealed that tool pin offset towards softer metal at medium tool rotational speed would create joints with the highest UTS. Scanning Electron Microscope (SEM) was applied to investigate the structural changes in the FSW of Al-Cu joints.

In the present study, parameters of tool rotation speed, tool travel speed and tool offsetting with different levels were used in the friction stir welding (FSW) of aluminum-copper tailor welded blanks (TWBs). The FSW of pure copper to 5052 aluminum alloy were carried out by varying tool rotation speed from 800 rpm to 1200 rpm, tool travel speed from 40 mm/min to 80 mm/min and tool offsetting from 1 mm to 2 mm. The L9 orthogonal array of Taguchi was used to design 9 experimental tests and each test was repeated three times. The uniaxial tensile test based on the ASTM-E8 was used for mechanical properties extraction of TWBs. The tool rotation speed of 1200 rpm, tool travel speed of 60 mm/min and tool offsetting of 1.5 mm resulted in the optimum range of heat input to form a stir zone with good quality. Using these FSW parameters caused the formation of thin intermetallic layers which stopped the motion of dislocation in the tensile test and resulted in higher tensile strength and joint quality. The scanning electron microscope (SEM) was used to scan the tensile fracture surface of TWBs.

A technology is developed for single-pass friction stir welding (FSW) of 11- and 35-mm-thick plates of Al–Mg–Sc alloys. The microstructural and mechanical heterogeneity of the welded joints is investigated. The welded joints obtained under the optimum welding conditions are free from macrodefects. The strength of the welded joint equals 98% of the strength of the parent metal, which is higher than the strength of fusion-welded joints. It is concluded that the FSW of thick plates of Al–Mg–Sc alloy can be used efficiently in practice.

Welding dissimilar metals by fusion welding is challenging. It results in welding defects. Friction stir welding (FSW) as a solid-state joining method can overcome these problems. In this study, 304L stainless steel was joined to copper by FSW. The optimal values of the welding parameters traverse speed, rotational speed, and tilt angle were obtained through Response surface methodology (RSM). Under optimal welding conditions, the effects of welding pass number on the microstructures and mechanical properties of the welded joints were investigated. Results indicated that appropriate values of FSW parameters could be obtained by RSM and grain size refinement during FSW mainly affected the hardness in the weld regions. Furthermore, the heat from the FSW tool increased the grain size in the Heat-affected zones (HAZs), especially on the copper side. Therefore, the strength and ductility decreased as the welding pass number increased because of grain size enhancement in the HAZs as the welding pass number increased.

Friction stir welding (FSW) is increasingly used in joining the high strength aluminum alloys. Compared to traditional fusion welding methods, one of advantages of FSW is to obtain defect– free joints more easily. Besides the forms of FSW tools and welding parameters, certain characteristics of the base material can also affect the quality of welded joints. There is usually a protective layer on aluminum alloy surface to prevent corrosion, called Al clad. Generally the mechanical properties of Al clad are significantly lower than those of the base metal. In this paper, tensile and three–point bending tests were applied to investigate the influence of accumulated Al clad on mechanical properties of joints. The mechanism of reducing the mechanical properties of joints, caused by the accumulated Al clad was analyzed by OM, SEM and EDS. The results show that the mechanical properties of the welded joints are lower than those of the joint with which the bottom Al clad on the base material is removed before or after welding. The Al clad tiled on bottom of the base material is squeezed to both sides of the onion ring in the role of the FSW tool and gathered in the bottom after welding. Due to the poorer mechanical properties of Al clad than the base metal, the Al clad aggregation positions become the weak areas in the joints, leading to the formation of the micro cracks in the joints under tensile stress where the micro cracks continue extending to generate macro cracks under the continuous * Q Ik^6~6F? 6 50875146 $xU7rP : 2010–06–10, $x+27rP : 2010–08–17 T 4 : X 0, 9, 1985 A , 5 DOI: 10.3724/SP.J.1037.2010.00276

Tungsten Inert Gas welding process (TIG) has been widely used in industries. A robotic arm has been adopted in the industry with objectives to replace or efficiently improved some severe welding conditions where it is dangerous for human and to increase productivity and quality. This research is aimed to find the optimal conditions of TIG welding process on AISI 304 stainless steel. The design of experiments used a statistical method to determine the optimal TIG welding conditions providing the strongest tensile strength across the weldment. The fractional factorial experimental design and then the central composite design were used as a response surface method to find the optimal TIG welding conditions for AISI 304 stainless steel using robotics system. The statistically significant factors and their optimal values are the welding current (136 Ampere), welding speed (13 cm/min), wire feed rate (93 cm/min), and the arc gap (2.5 mm). After that, the residual stress caused by TIG welding at the optimal condition was measured by X-ray diffraction (XRD) technique. The results showed that the weldment obtained from the optimal welding conditions provides compressive residual stresses which cause the materials to be stronger.

This paper describes a simple numerical model for predicting the heat generation in friction stir welding (FSW) from the material hot deformation and thermal properties, the process parameters, and the tool and plate dimensions. The model idealises the deformation zone as a two-dimensional axisymmetric problem, but allowance is made for the effect of translation by averaging the three-dimensional temperature distribution around the tool in the real weld. The model successfully predicts the weld temperature field and has been applied with minimal recalibration to aerospace aluminium alloys 2024, 7449 and 6013, which span a wide range of strength. The conditions under the tool are presented as novel maps of flow stress against temperature and strain rate, giving insight into the relationship between material properties and optimum welding conditions. This highlights the need in FSW for experimental high strain rate tests close to the solidus temperature. The model is used to illustrate the optimisation of process conditions such as rotation speed in a given alloy and to demonstrate the sensitivity to key parameters such as contact radius under the shoulder, and the choice of stick or slip conditions. The aim of the model is to provide a predictive capability for FSW temperature fields directly from the material properties and weld conditions, without recourse to complex computational fluid dynamics (CFD) software. This will enable simpler integration with models for prediction of, for example, the weld microstructure and properties.

This study investigates the use of heat-treated H13 steel tools in friction stir welding (FSW) of brass plates. In FSW, H13 steel tools are commonly used but may suffer damage or pin loss under high-duty cycles due to friction between the tool and workpiece. While most FSW research focuses on aluminum alloys, brass welding has received less attention. Fusion welding of brass can degrade mechanical properties, making solid-state processes like FSW essential for preserving these properties. The study varied tool rotational speed (1250, 1600, and 2000 rpm) and feed rate (12, 16, and 20 mm/s) to evaluate the effects of tool heat treatment and welding parameters on the mechanical and microstructural properties of FSW brass joints. Results showed that heat-treating H13 tools increased their strength. Higher rotational speeds and lower feed rates improved fracture strength and microhardness in the weld nugget zone, while reducing microhardness in the heat-affected zone. The nugget zone exhibited a compact structure with finer grains at optimal parameters. The highest fracture force (15201 N) and microhardness (167.2 Vickers) in the nugget zone were achieved under optimal welding conditions.

In the last decade there has been significant research into joining steel alloys using the Friction Stir Welding technique due to its ability to carry out welding below the melting point of the parent material and without using fillers such as in fusion welding techniques. This coincided with the increased use of DH36 and EH46 steel grades for ship building. The main reason for joining these steel grades by the friction stir welding technique is to reduce the weight of the vessel, as well as, the high welded joint quality especially mechanical properties such as fatigue and impact resistance. Other improved physical characteristics include increased tensile strength, microhardness and surface finish. This research project has attempted to model friction stir welding using Computational Fluid Dynamics (CFD). Three different approaches have been used when considering the interface between the tool and the workpiece; these are torque, sticking/slipping and fully sticking. The project also investigates the mechanical properties of the welded joints including tensile, fatigue and microhardness. The microstructural evolution of welded joints carried out using different welding parameters is also investigated. The phenomenon of elemental precipitation/segregation during the friction stir welding process has been investigated and the limit of tool rotational speed at which the segregation occurs has been determined by modelling and also by heat treatment to simulate FSW. The purpose of the heat treatment trials was to attempt to replicate the temperature and time that the parent materials experiences during the FSW process. Defects in the weld joints associated with unsuitable friction stir welding parameters were also investigated and two new types of defect have been identified for the first time. Finally, tool wear has been investigated in the different weld joints in order to understand the suitable welding parameters that can prolong tool life. The results from the mathematical modelling of FSW using CFD showed that the fully sticking assumption is the most effective approach for modelling friction stir welding of steel. The model also revealed that local melting at the advancing-trailing side of the tool is likely to occur at high tool rotational speeds. The experimental findings were in agreement with the results from the CFD model as the high tool rotational speed welded joints showed elemental segregation of Mn, Si, Al and O which only occurs when the peak temperature during welding approaches the melting point of steel. Experimental work has also shown significant improvement in the mechanical properties of the welded joints in terms of fatigue and tensile strength after friction stir welding compared to the parent metal. However, the joints welded at high tool rotational/traverse speeds have shown lower mechanical properties as a result of defects such as weld root defect and microcrackes which have been introduced. Tool wear was found to increase with the increasing tool rotational speed as a result of the tools W-Re binder softening. Tool wear was also found to increase with increasing plunge depth as a result of the high shear stress originating from the high thermo-mechanical action at the FSW tool surface. The current project has contributed to knowledge in the friction stir welding of steel by revealing the limits of tool speed that causes elemental segregation. The new technique for estimating the peak temperature and cooling rate using TiN precipitates can also be an alternative to thermocouple measurements which can significantly underestimate the tool-workpiece interface temperature.

The application of aluminium alloy, which is a typical lightweight material, has been expected in the construction of transportation vehicles to achieve energy saving by reduction of weight. However, structures made of whole aluminium alloy have problems with low strength and high cost. Thus, hybrid structures made of Al alloy and steel are useful because of light weight and higher strength. To construct the hybrid structure, it is necessary to weld aluminium alloy and steel. However, conventional welding methods, like brazing and mechanical fastening, have problems such as low mechanical strength and low productivity. Also, it is difficult to weld Al alloy and steel by conventional fusion welding. In this study, spot welding between aluminium alloy and low carbon steel by friction stirring was carried out. Especially, optimization in welding conditions was carried out. Moreover, the effect of welding conditions on the joint strength and weld interface was studied. As a result, relatively higher tensile shear strength of the weld, which was achieved at optimum welding conditions, was obtained. Temperature near weld interface measured by K-type thermocouple during welding was found to be lower than the melting point of A5052. From the observation results on microstructure of the weld interface, it was found that a Fe/Al intermetallic compound layer was formed.

Friction Stir Welding Process of Aluminum-lithium Alloy 2195

Welding input parameters play a very significant role in determining the quality of a weld joint. The quality of the joint can be defined in terms of mechanical properties, distortion and weld-bead geometry. Generally, all welding processes are employed with the aim of obtaining a welded joint with the desired characteristics. The purpose of this study is to propose a method to decide near optimal settings for the welding process parameters in friction welding of (AISI 904L) super austenitic stainless steel by using non conventional techniques and genetic algorithm (GA). Grey relational analysis and the desirability approach were applied to optimize the input parameters by considering multiple output variables simultaneously. An optimization method based on genetic algorithm was then applied to resolve the mathematical model and to select the optimum welding parameters. The main objective of this work is to determine the friction welding process parameters to maximize the fatigue life and minimize the width of the partial deformation zone (left & right) and welding time. This study describes how to obtain near optimal welding conditions over a wide search space by conducting relatively a smaller number of experiments. The optimized values obtained through these evolutionary computational techniques were also compared with experimental results. ANOVA analysis was carried out to identify the significant factors affecting fatigue strength, welding time and partially deformed zone and to validate the optimized parameters.

As an important factor in friction stir welding (FSW) process, temperature directly affects the microstructures and mechanical properties of welded joints. The present work aims to investigate the welding temperature and joint characteristics of AZ31 magnesium alloy under three FSW conditions: conventional friction stir welding (FSW), ultrasonic assisted friction stir welding (UaFSW), and ultrasonic and heat pipe assisted friction stir welding (UHaFSW), respectively. The results show that the welding temperature distributions and the characteristic of “non-uniformity” are presented in the FSW and UaFSW joints along the welding and horizontal directions. Compared with conventional FSW, UaFSW can effectively balance and improve the non-uniform temperature distribution in the joints, resulting in the significant decreases in the peak temperatures and durations of high temperature. Hence, the grains are refined in the microstructure of the nugget zone in the UHaFSW joints, which enhances their microhardness and tensile properties. Based on these results, it can be concluded that UHaFSW could be an effective method to improve the mechanical properties of AZ31 magnesium alloy welded joints.