Papers by Author: Sheng Yi Chang

Abstract: This study uses the finite element method (FEM) to predict the workpiece surface parameters, including contact area ratio and surface roughness, of asperity flattening in indentation and sliding contact for magnesium alloys sheet during warm isothermal forming. Contact area ratio and surface roughness are investigated for different process and material parameters, such as sliding distance, temperature, normal pressure and bulk strain rate by finite element analysis. The predicted results of the surface parameters from the finite element analysis are in good agreement with the results obtained from experiments.

Abstract: This study applies the finite element method (FEM) to predict maximum forging load and effective strain in helical-bevel gear forging. Maximum forging load and effective strain are determined for different process parameters, such as modules, number of teeth, and die temperature of the helical bevel gear forging, using the FEM. Finally, the prediction of the power requirement for the helical-bevel gear warm forging is determined.

Abstract: Scratch test is mainly used to study mechanical properties of materials near their surface. This study applies the finite element method (FEM) in conjunction with an abductive network to predict the scratch character such as rear contact angle, shape ratio and hardness for strain hardening bulk material of scratch process. To verify the prediction of FEM simulation of scratch process, the experimental data are compared with the results of current simulation. A finite element analysis is also utilized to investigate the material properties on side view contour, rear contact angle, hardness and shape ratio. Additionally, the abductive network was applied to synthesize the data sets obtained from the numerical simulation. The prediction models are then established for the rear contact angle, hardness and shape ratio of nanoscratch process under a suitable range of material parameters.

Abstract: This study applies the finite element method (FEM) in con-junction with an abductive network to predict springback’s angle during the U-shaped bending process with counter force. To verify the prediction of FEM simulation for springback, the experimental data are compared with the results of current simulation. Bending force, effective stress distribution and springback are investigated for different process parameters, such as profile radius of die, blank holder force and counter force of U-shaped bending process, by finite element analysis. The abductive network is then utilized to synthesize the data sets obtained from numerical simulations. Finally, prediction model is established for predicting springback’s angle under a suitable range of process parameters.

Abstract: This study applies the finite element method (FEM) in conjunction with an abductive network to predict the workpiece surface parameters, including contact area ratio, surface roughness, skewness and kurtosis, of asperity flattening in sliding contact for metallic thin film on die material during the metal forming process. Contact area ratio, surface roughness, skewness and kurtosis are investigated for different process and material parameters, such as sliding distance, elastic modulus of film, normal pressure and bulk strain rate by finite element analysis. The abductive network is then utilized to synthesize the data sets obtained from numerical simulations, and the prediction model is established for predicting surface parameters. The predicted results of the surface parameters from the prediction model are in good agreement with the results obtained from the FEM simulation of workpiece asperity flattening in sliding contact for metallic thin film on die material.

Abstract: Wire and rod drawing is widely used in metal forming processes to obtain products such as rods and wires. Rods having shaped sections such as square, rectangle and irregular section are necessary to produce connecting pins and components of transformers. Important characteristics of the shaped drawing process are the corner filling and inhomogenious factor of strain that influence the dimensional accuracy and the good quality of the product. In this paper, a three-dimensional rigid-plastic finite element analysis is used to simulate the drawing process of a square rod from a round bar. A finite element method is also used to investigate the corner filling, forming load, stress distribution and inhomogenious factor of effective strain under various process parameter conditions, including the reduction of area, the die semi-angle, and the friction factor

Abstract: In the deep drawing of cups, the earing defect is caused primarily by planar anisotropy in the sheet. In order to obtain the optimal products in deep drawing process, blank shape is a very important formability factor. In this study, the finite element method was used to investigate the cup height and forming force of the cylindrical cup drawing process. A finite element analysis was also utilized to acquire the designed profile of the drawn products, a reverse forming method for obtaining the initial blank’s shape according to the forward cylindrical cup drawing simulation is proposed. The design of initial blank’s shape is also confirmed to obtain the designed profile of drawn cups. The influences of the blank’s shape on the height of product, the forming force, the effective stress and the effective strain were also examined.

Abstract: In this study, the predictive model of friction coefficient using cylindrical compression was constructed through combining the finite element method and neutral networks. Namely, the related data of the materials characters, cylinder compression bulging, and how they were associated with friction coefficient was obtained by the finite element method. Based on those analysis data, the relationship model, reflecting the relationship among the materials characters such as strength coefficient and strain-hardening exponent, the compression bulging such as reduction height, expanding in upper ending, expanding in bottom ending, maximum expanding in outside diameter and the friction coefficient in workpiece/die interface, was constructed. Finally, the cross verification between finite element analysis, prediction by neutral network model and the experiments of cylindrical compression testing and ring compression testing are repeatedly checked to ensure the accuracy and reliability of the constructed model. Results of the current study indicate that their errors are extremely limited, and the developed predictive system is reliable and feasible.