Xin Yun Wang

A Study of Hole Flanging-Upsetting Process

A combined process of hole flanging and flange upsetting was proposed. Both elastic-plastic FEM and experiments were employed to analyze the process. A 2mm thick 08AL sheet with 120mm outer diameter and 24.6mm center hole diameter was used as the blank. The effect of the Rf and the Rc values on the flanging quality were analyzed, where Rf was defined as the ratio of the die fillet size to the workpiece thickness t and Rcwas defined as the ratio of the clearance C to the workpiece thickness t. Also the effect of Rf and Rc on upsetting ratio Ru which was defined as the ratio of thickness before and after upsetting were studied. The finite element results were validated by experimental results. Also a 2mm thick flange without thinning and defects was gained in a reasonable range of Rc and a certain value of Rf.

Hot Deformation Behavior and Processing Maps of 7050 Aluminum Alloy

The hot deformation behavior of 7050aluminum alloy was investigated by hot compression tests in the temperature range of 573-773K and the strain rate ranging from 0.001s-1 to 10 s-1.The flow curves showed that the flow stresses increase with the increase of strain rate or the decrease of temperature.In order to determine the optimal processing conditions, hot processing maps were established based on experimental data and Dynamic Materials Model. The processing maps indicate that instability occur at low temperature and high strain rate. The optimum hot working region is the domain in the temperature range of 673-723K and strain rate range of 0.001-0.01 s-1,where typical recrystallization was observed in the optical microstructures.

Microstructure and Texture Evolution of 2024 Aluminum Alloy Sheet under Different Loading Conditions

To study microstructure and texture evolution of 2024 aluminum alloy sheet under different loading conditions, thermal tensile and compression experiments of 2024 aluminum alloy rolled sheets were carried out at temperatures ranging from 300 °C to 450 °C and under strain rates ranging from 0.001 s-1 to 0.1 s-1. During tensile deformation, the HABs of original grains are directly elongated until abruption. DRX process occurs during compression. Dislocations appear during deformation, migrate and accumulate into LABs, and then rotate into HABs to form new grain.The three-dimensional orientation distribution functions (ODFs) in different stress states were measured, with related texture types and distribution laws compared. According to ODFs with a constant φ2, the deformation texture of {011} <100>Goss texture is gradually strengthened during thermal tension at high temperature and low strain rate (450°C/0.001s-1). The deformation texture of {011} <100>Goss texture is weakened with the strain increasing. Furthermore, the increase of deformation temperature or the decrease of strain rate slows down the weakening process of {011} <100> Goss texture, which is attributed to the recrystallization behavior during tensile deformation. Besides, since the recrystallization process proceeds more completely during hot compression, it produces a quasi-random texture.

Study on Multi-Step Spinning Process for Disk-Like Part with Thickened Rim

This paper studies the process of a five-step spinning to thicken the edge of the disc-like part. By using finite element simulation and experiment, the sectional shape and flow-line distribution of the rim were studied. The results showed that the flow lines of the cross-section of the formed part are distributed along the shape of the part. The disc-like part with thickened rim can be well formed by a multi-step spinning process. A large bottom radian of roller groove can lead a folding in the first step and a reduced r can overcome the folding. An over-small angle αin step 2 will lead a pit defect, it can be solved by increasing the angle.

Investigation of a Two-Step Rotary Rim-Thickening Process of Disc-Like Blanks

A two-step rotary rim-thickening process of disc-like blanks was investigated by FE simulation and spinning experiments. The preforming shape of cross section for first step was designed as trapezium before forming rectangular-shape rim in the second step. The main factors influencing the blank forming in the first step were groove bottom height h1 and the inclination angle α of the roller. With the increase of h1 and α of the roller in FE simulation, the workpiece will be more prone to lose stability and cause defects. The forming limit diagram was obtained in first step, including stable forming zone, unstable forming zone and failed forming zone. Considering the stability and efficiency of thickening, four groups of h1 and α were selected for the second step simulation. Maximum rim thickness (h2) after second-step forming was 9 mm, obtained by trial and error in FE simulations. The spinning experiments were carried out to verify the validity of numerical simulation.

Numerical Simulation Research on Warm Forging Process for Spur Gear with Large Module Based on Floating Die Method

The warm forging process of spur gear with large module using floating die set was studied in the paper. The influence of process parameters such as billet temperature, web position, web thickness, frictional factor on the filling of die cavity and forging load were investigated by finite element method. It was concluded that the corner filling of gear can be improved by using free floating die. The forging load decreased with the increase of billet temperature or the decrease of frictional factor. The best web position for die cavity filling was that the web was located in the middle of the forged part.

Numerical Simulation of Residual Stress during Stamping-Forging Forming of 2024 Aluminum Alloy Sheet Metal

The unreasonable residual stress field in sheet part has an adverse effect on the dimensional accuracy and performance. A forming method combined stamping and forging was proposed to reduce the residual stress of the sheet part. The residual stress field in 2024 aluminum alloy V-shaped piece after bending and forging was analyzed by the finite element software Abaqus. The results showed that the stamping-forging forming process can significantly reduce the residual stress in round corner of V-shaped piece, and simultaneously decrease springback and improve the dimensional precision of sheet part.

Thermoplastic Deformation Behavior of 4032 Al Alloy

The effect of processing temperature and strain on microstructure and mechanics property of 4032 Al alloy was performed with hot extrusion experiment and finite element method. The results show that the primary silicon distributes more uniformly along with the increase of strain at a certain deformation temperature, and the tensile stress and elongation have less variation. However, elongation decreases obviously when the strain are higher than 70%. At a certain strain, tensile strength increases and elongation decreases when deformation temperature are higher than 400 °C. Primary silicon also grows obviously. Finally, finite element calculated load data testified the experimental results.

Optimal Design of Pre-Forging for Gear Blank Using BP Neural Network and Genetic Algorithm

The design of pre-forging is very important during multistage forging of producing gear blank. It directly affects the behavior of metal flowing, filled situation of die cavity of finish forging, quality of products and die life. Most designs of pre-forging for gear blank are based on trial and error method. This paper presents a suitable method for practical designation of pre-forging for gear blank by proposing an improved algorithm, which combines Back Propagation Neural Network and Genetic Algorithm. Firstly, the mathematical model between the size parameters of pre-forging and forming force and maximum die stress of finish forging was established by using Back Propagation Neural Network which has the feature of processing highly nonlinear problems. Secondly, the established model was set as the fitness function of Genetic Algorithm. At last, the most superior pre-forging shape and the size parameters were solved by using the Genetic Algorithm with the function of overall situation optimization. These can lead to lower cost and time in the stages of designing pre-forging for gear blank.

Effect of Deformation Temperature on Deformation Behavior and Service Performance of 7050 Aluminum Alloy

Compression tests of 7050 aluminum alloy have been conducted at different temperatures (340, 380, 420, and 460 °C) with strain rate of 0.1 s-1. The deformation behavior and service performance of the alloy are investigated using EBSD technique, TEM and hardness measurement. Results show that the volume fraction of recrystallized grains increases with the increase of deformation temperature. The primary softening mechanisms of the alloy deformed at 340, 380, and 420 °C are dynamic recovery, and dynamic recrystallization is the main softening mechanism of the alloy deformed at 460 °C. The hardness of the 7050 aluminum alloy deformed increases with increasing deformation temperature. Dynamic precipitation appears when the 7050 aluminum alloy was deformed at 340, 380, and 420 °C, and strengthening mechanisms include mechanical hardening and precipitation strengthening. When deformation temperature is 460 °C, solid solution strengthening and grain boundary strengthening are primary strengthening mechanisms.