Predicting Residual Thermal Stresses in Friction Stir Welding

2003 ◽  
Author(s):  
Mir H. Zahedul Khandkar ◽  
Jamil A. Khan
Keyword(s):  
Friction Stir Welding ◽  
Residual Stresses ◽  
Thermal Model ◽  
Thermal Stresses ◽  
Three Dimensional ◽  
Welding Process ◽  
Temperature History ◽  
Temperature Dependent ◽  
Friction Stir ◽  
Input Torque

Sequentially coupled finite element models of the friction stir welding process have been proposed to study the residual stresses caused by the thermal cycles during friction stir welding of metals. This is a two step simulation process. In the first step, the thermal history is predicted from an input torque based thermal model. The temperature history generated by the thermal model is then sequentially coupled to a mechanical model that predicts the residual stresses. The model does not deal with the severe plastic deformations within the weld nugget and the thermo-mechanically affected regions, a fact that may cause modeled results to deviate from experimentally measured residual stresses. The model is three dimensional and uses temperature dependent material and thermophysical properties.

Mathematical Model for Multi-Component Forces and Torque Determination in Friction Stir Welding

2011 ◽  
Vol 230-232 ◽  
pp. 1255-1259
Author(s):  
T. Khairuddin Jauhari ◽  
I.P. Almanar ◽  
Hussain Zuhailawati
Keyword(s):  
Mathematical Model ◽  
Friction Stir Welding ◽  
Early Stage ◽  
Three Dimensional ◽  
Welding Process ◽  
Temperature Dependent ◽  
Metallic Material ◽  
Friction Stir ◽  
Work Material ◽  
Force Components

Major works concentrated on the energy conversion from mechanical friction work to heat; emphasized on the immediate contact surface of work material and rotating welding tool but with no in-depth analytical study to relate the loads that are transferred to the work material and the welding fixture especially at early stage of heat generation. In this work, a mathematical model is developed to predict three-dimensional force components and axial torque of the rotating tool based on contact mechanic principle in relation to Al6061 temperature-dependent material properties. The model shows the ability to be possibly adapted for different metallic material and physical properties. It suggests the exerted torque and loads calculation endured by work material involving friction and shear mechanism of two static-dynamic contacting surface; rotating rotational tool and the fixed work material, to be used as one of the option for optimization of the welding process such as to determine the ratio of slip, non-slip contact condition through comparisons of experimental and computer simulation on the Friction Stir Welding process.

Computational Analysis on Weld Formation Mechanism during Self-Reacting Friction Stir Welding

2020 ◽  
pp. 1-15
Author(s):  
Chenyu Zhao ◽  
Xun Liu
Keyword(s):  
Boundary Condition ◽  
Shear Stress ◽  
Friction Stir Welding ◽  
Shear Layer ◽  
Formation Mechanism ◽  
Fluid Model ◽  
Three Dimensional ◽  
Welding Process ◽  
Weld Formation ◽  
Friction Stir

Abstract Three-dimensional computational fluid dynamics models are developed to understand physical principles of self-reacting friction stir welding process. A novel approach of predicting the weld microstructure based on plastic strain distribution at cross-section behind the tool is proposed and verified with experimental results. Limitations and credibility of shear stress and velocity tool/workpiece boundary condition are evaluated from the perspective of the weld formation mechanism. The importance of the shear layer and its sticking/sliding transition state in weld formation mechanism is emphasized. From modeling perspective, shear stress boundary, which only represents a sliding condition, neglects the movement and effects of this shear layer. When shear layer is formed, due to the velocity discontinuity which could not be captured in fluid model, velocity boundary condition, which represents an averaging effect of sticking/sliding transition between tool and shear layer, is needed.

Numerical Simulations of Friction Stir Welding Process and Subsequent Post Weld Cold Rolling Process

2009 ◽  
Vol 419-420 ◽  
pp. 433-436 ◽  
Author(s):  
Yu Jie Sun ◽  
Yong Zang ◽  
Qing Yu Shi
Keyword(s):  
Residual Stress ◽  
Friction Stir Welding ◽  
Three Dimensional ◽  
Welding Process ◽  
Rolling Process ◽  
Mechanical Analysis ◽  
Fusion Welding ◽  
Work Piece ◽  
Friction Stir ◽  
Longitudinal Residual Stress

A sequential coupled three-dimensional thermo-mechanical analysis was conducted first to simulate friction stir welding (FSW) of aluminum alloy. In thermal analysis, the model included adaptive heat source, contact heat transfer both between work piece and clamps and between work piece and backing board etc; in the mechanical analysis, the model involved contact interaction both between work piece and clamps and between work piece and backing board, mechanical load of tool etc. The simulation results indicate that the longitudinal residual stress is unsymmetrical about weld centerline; the magnitude of longitudinal residual stress for FSW process is lower than that for fusion welding process. Based on simulated results of FSW process, a three-dimensional elastic-plastic analysis was then carried out to simulate rolling process, the simulation result show that rolling process not only causes a marked reduction in the longitudinal tensile residual but also reverse the sign of the longitudinal residual stress.

scholarly journals Technology and equipment for friction stir preweld edge preparation

2021 ◽  
Vol 21 (2) ◽  
pp. 163-170
Author(s):  
Y. G. Lyudmirsky ◽  
А. N. Soloviev ◽  
М. V. Soltovets ◽  
R. R. Kotlyshev ◽  
I. V. Mironov ◽  
...  
Keyword(s):  
Finite Element ◽  
Theoretical Model ◽  
Friction Stir Welding ◽  
Geometric Model ◽  
Three Dimensional ◽  
Welding Process ◽  
Element Model ◽  
Element Mesh ◽  
Laboratory Equipment ◽  
Friction Stir

Introduction. Friction stir welding is widely used due to certain advantages of this method. Factors that reduce the strength of joints made of high-strength aluminum alloys are considered. When welding flat sheets, an effective way to increase the strength of the weld is edge thickening. The paper proposes a method for such thickening. A device is developed, calculations and experiments are carried out. Materials and Methods. Laboratory equipment has been developed to provide simultaneous thickening of two edges to be welded. The main component of this equipment is a steel roller, which is rolled along the edges of two blanks and thickens them due to plastic deformation. The same setup can be used for the friction stir welding process. To calculate the geometry of the thickened edges and the parameters of the deforming roller depending on the value of the edge settlement, a mathematical model based on the contact problem for elastic (roller) and elastoplastic (blank) bodies with a bilinear hardening law has been developed. A three-dimensional simplified geometric model of the facility with account of its symmetry has been constructed. On the contact surfaces, special contact finite elements were selected and the finite element mesh was refined. The numerical implementation of the model was carried out in the ANSYS package. Results. The theoretical model provides assessing the stress-strain state of interacting elements. On the basis of the developed finite element model, the parameters of the thickened edges are calculated, and the geometry of the thickened edges is defined. Using the developed laboratory equipment, full-scale experiments on thickening the edges of the blanks were carried out. The experimental results confirm the adequacy of the developed theoretical model and calculations based on it. The possibility of adjusting the size of the thickened edges is shown.Discussion and Conclusion. A technology for obtaining thickened edges in places of welds is proposed. It will reduce the metal consumption of structures and ensure the bearing capacity of welded joints not lower than similar characteristics of the base metal. A theoretical model of the process is developed, and a numerical experiment providing the selection of the process parameters is carried out. 

Study on the effect of the welding environment on the dynamic recrystallization phenomenon and residual stresses during the friction stir welding process of aluminum alloy

2021 ◽  
pp. 146442072110251
Author(s):  
Mahmoud Abbasi ◽  
Amin Abdollahzadeh ◽  
Behrouz Bagheri ◽  
Ahmad Ostovari Moghaddam ◽  
Farzaneh Sharifi ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
Friction Stir Welding ◽  
Residual Stresses ◽  
Welding Process ◽  
Friction Stir ◽  
Friction Stir Welding Process ◽  
Underwater Friction Stir Welding ◽  
Processed Sample ◽  
Vibration Welding ◽  
Strength And Ductility

Various methods have been proposed to modify the friction stir welding. Friction stir vibration welding and underwater friction stir welding are two variants of this technique. In friction stir vibration welding, the adjoining workpieces are vibrated normal to the joint line while friction stir welding is carried out, while in underwater friction stir welding the friction stir welding process is performed underwater. The effects of these modified versions of friction stir welding on the microstructure and mechanical characteristics of AA6061-T6 aluminum alloy welded joints are analyzed and compared with the joints fabricated by conventional friction stir welding. The results indicate that grain size decreases from about 57 μm for friction stir welding to around 34 μm for friction stir vibration welding and about 23 μm for underwater friction stir welding. The results also confirm the evolution of Mg2Si precipitates during all processes. Friction stir vibration welding and underwater friction stir welding processes can effectively decrease the size and interparticle distance of precipitates. The strength and ductility of underwater friction stir welding and friction stir vibration welding processed samples are higher than those of the friction stir welding processed sample, and the highest strength and ductility are obtained for underwater friction stir welding processed samples. The underwater friction stir welding and friction stir vibration welding processed samples exhibit about 25% and 10% higher tensile strength compared to the friction stir welding processed sample, respectively. The results also indicate that higher compressive residual stresses are developed as underwater friction stir welding and friction stir vibration welding are applied.

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