Abstract
The current study performs an explicit nonlinear finite element simulation to predict temperature distribution and consequent stresses during the friction stir welding (FSW) of AA 7075-T651 alloy. The ABAQUS® finite element software was used to model and analyze the process steps that involve plunging, dwelling, and traverse stages. Techniques such as Arbitrary Lagrangian–Eulerian (ALE) formulation, adaptive meshing, and computational feature of mass scaling were utilized to simulate sequence events during the friction stir welding process. The contact between the welding tool and workpiece was modelled through applying Coulomb’s friction model with a nonlinear friction coefficient value. Also, the model considered the effect of nonlinear material properties as well as heat transfer conditions such as heat losses due to convection and thermal contact conductance between the workpiece and the backing plate interface on the thermal history. To validate the computational model results, an experimental procedure was carried out to measure temperature history on both sides of the specimen as well as the plunging force throughout the whole process time. The results obtained showed that symmetrical temperature distribution throughout the workpiece width was distinguished, implying that the tool rotation has a minor effect on the final temperature distribution. In addition, asymptotic V shape with high gradient temperature value in the weld nugget region after the full plunging was distinguished. Mechanical stresses and related plastic deformations generated, while achieving the FSW samples were evaluated in addition to the tool reaction force and heat generated to protect against tool failure.
Highlights
AA 7075 alloy is a heat treatable aluminum alloy that possesses prominent mechanical properties such as functional corrosion protection, maintaining of high strength properties, flexible machinability, and lightweight functions.e high strength properties are usually achieved through the precipitation of Mg2Zn and Al2CuMg phases
To control the probability of having process defects, it is urgent to get more precise data regarding the temperature distribution in the welding zone and about the treated region since it dominates the microstructural map and precipitate distribution. e embedded thermocouples that used to measure the maximum temperature as well as temperature history during the friction stir welding process were usually located at some remote locations that are away from the nugget zone. is indicates a fact that measuring temperature variations in the nugget zone using the thermocouples can not be achieved accurately. To cope with this problem, the finite element method has been proposed as a second option efficient method to develop the simulation models that can predict temperature history, stresses and associated deformations, and material flow engaged during the FSW process
15 mm 20 mm Backing supporting plate temperature, stresses, and plastic strains of the AA 7075 material interacting with the welding tool were quantitatively calculated through using ABAQUS/EXPLICIT [18] in conjunction with the Arbitrary Lagrangian–Eulerian (ALE) adaptive meshing technology in addition to temperature and rate-dependent failure criteria to implement a fully coupled explicit analysis of the AA 7075-T651 FSW process. e governing equation for the transient temperature distribution in the workpiece is like the governing equation of 3D heat conduction with suitable boundary condition, as described by Spencer [19]: zT
Summary
AA 7075 alloy is a heat treatable aluminum alloy that possesses prominent mechanical properties such as functional corrosion protection, maintaining of high strength properties, flexible machinability, and lightweight functions. Is indicates a fact that measuring temperature variations in the nugget zone using the thermocouples can not be achieved accurately To cope with this problem, the finite element method has been proposed as a second option efficient method to develop the simulation models that can predict temperature history, stresses and associated deformations, and material flow engaged during the FSW process. Riahi and Nazari [12] conducted a finite element simulation to model temperature distribution and resulting residual stresses in friction stir welding of aluminum alloy 6061-T6. Many studies were conducted to model the temperature history during the friction stir welding of AA 7075-T651 alloy using three-dimensional geometry with a Pseudo-heat transfer model, but none of these applied ALE approach with time-varying friction coefficient value to simulate both thermal and mechanical actual material behaviours during the plunging, dwelling, and traversing steps of the FSW process. To verify the simulation output, an experimental procedure is carried out to measure temperature distribution throughout the full time of the FSW process
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