Gang Yao Zhao

Numerical Simulation on Influence of Clearance and Friction on Wrinkling in Bending of Aluminum Alloy Rectangular Tubes

The clearance and friction have large influence on wrinkling in rotary draw bending process of thin-walled rectangular tube. In this paper, a three-dimension Al FEM model of rotary draw bending of thin-walled rectangular tube is built under the ABAQUS/ Explicit environment. Based on the model, simulation and analysis of rotary draw bending for aluminum alloy 3A21 thin-walled rectangular tube have been carried out. The results show that the height of wrinkling wave decreases obviously with the decrease of the clearance between mandrel and tube or with the increase of the friction coefficient between wiper die and tube; however, the effect of friction coefficient on wrinkling becomes weaker while increasing the clearance between mandrel and tube. The achievements of this study provide a guideline for determining the process parameters for thin-walled rectangular tube in rotary draw bending process.

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.

Experimental Research on Strain Distribution Characteristics of Thin-Walled Rectangular Tube in Rotary-Draw Bending

The rotary-draw bending process of thin-walled rectangular tube is a complex process with large deformation, large displacement and finite strain which makes the defects, such as wrinkling, distortion and crack be easily produced. To study the complex plastic deformation characteristics of thin-walled rectangular 3A21 aluminum tube during rotary-draw bending, the distributions of tangential, circumferential and normal strain have been studied by experiment using grid method. The results show that the maximum value of three-direction strain appears in the ridges of rectangular tube and tangential strain is the maximum principal strain. The value of maximum tangential tensile strain is lager than the maximum tangential compressive strain; it is the reason why crake is prone to occur during rotary-draw bending. The strain distribution curve along bending direction is not completely symmetrical with middle cross-section. With the increase of bending angle, three-direction strain of tube also increases and circumferential strain increases relatively smaller.

Design of Assistance System Based on OpenCV for Color-Blindness

With the wide application of image processing as well as continuous improvement of processing means, carrying out rotation transformation of H component of the color space with OpenCV can improve the resolution for color and make up for the color discrimination capacity of the achromat effectively. Experiments have shown that when the type of color-blindness is given and the colors of the image are confusing for the given achromat, rotate the H component by 105~130°, the achromat can identify the colors well.

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.

Effects of Process Parameters on Wall Thinning Ratio during One Pass Hot Power Backward Spinning for 7075 Cast Aluminium Alloy Tube

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

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

To obtain the effects of parameters on wall distribution homogeneity of 7075 cast aluminium alloy tube in hot power backward spinning accurately, a new method to accurately describe the wall-nonuniformity of the tube has been proposed. Combined with FE analysis, the change regularities of the wall-nonuniformity with the process parameters varying were obtained. The results show that wall-nonuniformity first increases slightly, and then decreases with the increase of preheating temperature. With roller feed rate increasing, wall-nonuniformity increases firstly, and then decreases. Furthermore, the wall-nonuniformity reaches a minimum value when the roller feed rate is 0.6mm/r. The wall-nonuniformity increases firstly, and then decreases with the increase of roller fillets radius, but the trend becomes weaker.

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.