Zheng Hua Guo

Numerical Simulation of Temperature Field for TIG Welding of Aluminum Alloy Sheet Based on the SYSWELD

Using SYSWELD to simulate welding temperature field for TIG welding of aluminum alloy sheet, The transient temperature field distribution and features of the thermal cycle curve is given. As a result, the calculated data is in good agreement with literature data, the model can provide a basis for technical parameters optimization during the process of TIG welding of aluminum alloy.

3D Numerical Simulation of Linear Friction Welding of 45# Carbon Steel

A 3D finite-elements model of 45# carbon steel of linear friction welding is built with the dynamic explicit code ABAQUS/explicit based on the solution of several key techniques, such as contact boundary condition treating, material properties definition, meshing technology, etc. Then the reliability of the model is validated by comparison with experiments in the literature. Furthermore, numerical simulation and analysis of the linear friction welding process of 45# steel have been carried out by using the model. The temperature field of workpiece, the temperature change of center point of welding interface and the metal flow behavior of welding interface are showed in results.

Evolution Regularity of Temperature Filed in Hot Power Backward Spinning for 7075 Cast Aluminium Alloy Tube

The spinning temperature is one of key factors affected the uneven deformation during the hot power backward spinning for brittle material tubes, such as cast 7075 aluminium alloy tube. To analyze the evolution regularity of temperature filed in the spinning process, a 3D thermo-mechanical FE model of the process is developed under ABAQUS/Explicit environment. Then, the evolution of temperature filed during the process is analyzed based on the FE model. The results show that: The contact areas temperatures between lock ring, spinning rollers and tube decrease sharply during the initial spinning stage. The high temperature region is transferred from unformed zone of the tube to the contact area between spinning roller and tube. In the spinning zone, the temperature of internal surface of the tube is apparently higher than that of outer face.

Finite Element Analysis of Materials Flow Behavior in Friction Stir Welding of 7075 Aluminum Alloy Plate

A 3D elastic-plastic and coupled thermo-mechanical FE model for friction stir welding(FSW) of 7075 aluminum alloy plate was developed based on the dynamic explicit code ABAQUS/explicit, then the FSW process of 7075 aluminum alloy plate was simulated and the materials flow behavior was analyzed. The results show that in the horizontal direction of the plate, two patterns of materials migration are produced: (1) the material rotates with the tool and finally deposits the tentative cavity behind the pin; (2) the material transfers in the mode of laminar flow. Furthermore, the streamlines of material in advanced side (AS) are bent along the reverse welding direction. After bypassing the pin, the material of retreating side (RS) moves backward it, and extends to AS.

Simulation Experiment on Friction Coefficients during Warm Deep Drawing of Magnesium Alloy Sheet

In sheet metal forming, friction condition between sheet metal and mold is a very important problem for it influences the formability and the variation of stress, strain and thickness of sheet metal, and so on. Simulation experiments had been done to measure friction coefficients online at punch and die rounded corners under different process parameters during warm deep forming of magnesium alloy sheet. The results made it clear: temperature shows the greatest effect on friction coefficients, the effect of blank holding force (BHF) secondly, and no significant effect of lubricant on the friction coefficients. The friction coefficients at die rounded corner are larger than those at punch rounded corner. The dynamic changed friction coefficients models with temperature and BHF were fitted by the experimental data respectively, and they were added into simulation software through further development by user subroutine VFRIC using FORTRAN language to improve the accuracy of the numerical simulation.

Plastic Deformation Behavior of High Strength Cast Aluminium Cylinder in Hot Power Backward Spinning

The hot power backward spinning(HPBS) of the high strength cast aluminums (HSCA) cylinder is a complex metal forming process. To analysis the plastic deformation of HSCA cylinder in HPBS process, a 3D coupled thermo-mechanical FE model of the process was built under the ABAQUS/explicit environment based on the solution of several key techniques, such as heat boundary condition treating, material properties definition, ALE adaptive meshing technology, etc., and verified by theoretical evaluation. Then simulation and analysis of HPBS of the process were carried out. The results show that the strain gradient which leads to the serious inhomogeneous deformation is produced in the thickness direction of the workpiece during the process.

Coupled Thermo-Flowing 3D Steady State Model of Friction Stir Welding Process

The coupled thermo-flowing 3D steady-state model of friction stir welding model is established based on fluid mechanics. With analyzing the impact of pin shoulder and pin on heat producing, the model considers the influence of pin on the heat producing processing. The model applies viscoplastic constitutive equations to describe the material, and turbulence model to simulate the material flowing behavior. With the additional turbulence kinetic energy equations and flow boundary condition equations, the model is established. With Comsol Multiphysics finite analysis software, a process simulation was carried out, and the results reflect that the model can reveal the steady state characteristics of thermo and material flowing behavior of friction stir welding.

Effects of Process Parameters on Elongation during Hot Power Backward Spinning for 7075 Cast Aluminium Alloy Tube

To obtain the effects of parameters on elongation of 7075 cast aluminium alloy tube in hot power backward spinning accurately, a method to accurately describe the elongation of the spun tube has been proposed. Combined with the FE analysis, the change regularities of elongation with the variation of process parameters were obtained. The results show that the elongation of the spun tube increases gradually with the increase of preheating temperature, and the trend becomes larger and larger. The elongation sharply decreases firstly, and then tends to a stable value with the increase of roller feed rate. With the increase of roller fillets radius, the elongation increases gradually, but the trend becomes weaker.

Fabrication and Microstructure of Zn-Sn Target Material Alloy

In this paper, Zn-Sn target material alloys were prepared in an electric resistance furnace. The effects of cooling condition on casting macro-defect, microstructure and segregation of ingots during solidification have been investigated by SEM and EDX analyses. The results show that the alloys casted in air-cooled and water-cooled steel moulds have not apparent casting macro-defects. The measured Sn concentration of alloys is very close to the nominal composition. The microstructures of Zn-Sn alloys are consisting of Zn-rich primary dendrite phase and divorced eutectic Sn-rich phase. The ingots solidified in water-cooled steel moulds have smaller grains than in air-cooled moulds.

A Study of Material Flow Behavior in Thickness Direction in Friction Stir Welding of 7075 Alloy Plate

Friction stir welding, which is considered to be a solid-state welding, possesses several advantages over conventional welding processes, is an effective approach to weld high-strength, large thickness and dissimilar materials. Material flow behavior on FSW was generally acknowledged to have effects on weld property. The material flow behavior in thickness direction of advancing and retreating side was analyzed by a numerical model established with cone-shape tool pin. Numerical results indicate that there exist material flow in thickness direction on both sides and the behavior was affected by welding and tool pin rotation speed. Decrease welding speed or increase rotation speed would make material deformation intensified, and increase the fluidity of the material.