Papers by Author: Hu Jie

Abstract: This paper proposed some improvement measures of Genetic Programming (GP) in data fitting, including developed new ways of crossover and mutation, improved the calculation efficiency greatly, and avoided the problem of parse tree expansion. The new adopted mutation method improved the problem of constant modification to some extent. Numerical simulation obtained a considerable good fitting and prediction precision.

Abstract: Numerical simulation technology has been used widely in plastic forming area. However, the simulation of increasingly complex forming process leads to the generation of vast quantities of data, which implies much useful knowledge. Consequently domain knowledge is very significant to product design and process development in metal plastic forming area. The paper presented a new robust optimization method based on knowledge discovery from numerical simulation. Firstly, the knowledge discovery model from numerical simulation is established. In this model, interval-based rule presentation is adopted to describe the uncertainty of design parameters quantitatively to enhance the design robustness. Secondly, the optimization process based on knowledge discovery and management is presented, and genetic arithmetic is used to obtain the robust optimization parameter. Finally, the application to robust optimization of extrusion-forging processing is analyzed to show the scheme to be effective. The proposed method can overcome the pathologies in simulation optimization and improve the efficiency & robustness in design optimization.

Abstract: Blank holder force (BHF) plays an important role in sheet metal forming. Previous studies demonstrated that variable blank holder forces can improve the cold formability of steel blank, but the research on the application of variable blank holder force in warm forming of magnesium sheet forming has not been well investigated. In this study, the mechanical property of AZ31 magnesium alloy sheet is measured through some uniaxial tensile tests. In order to obtain the variational rule of the BHF, a mathematical model of BHF is deduced based on the energy theory. The variational rule of the BHF over the punch stroke is analyzed. Finally, three profiles of the BHF curve are designed, and the numerical simulation of warm deep drawing process of magnesium alloy sheet is also performed. A suitable variable blank holder force scheme is obtained through comparison among three results of simulation. The simulation indicates that the limiting drawing ratio of AZ31 magnesium alloy sheet can be improved from 3.0 to 3.5 with the suitable blank holder force varied by an inverted V curve.