Improvement of Profile Accuracy Coincidence Rate in Press-Forming Simulation of High Tensile Strength Steel Considering the Bauschinger Effect

Introduction

In order to improve the fuel efficiency of transportation machinery, reduction of vehicle body weight is demanded. Use of high tensile strength steel has attracted attention as one approach to weight reduction, as it is possible to design vehicle bodies with thinner materials. However, when using high tensile strength steel, shape defects easily occur after press forming, and the excessive time and cost required to manufacture press dies was a problem. Although springback is one factor in shape defects, accuracy in the predictions of the springback phenomenon has improved in recent years as a result of progress in CAE (Computer Aided Engineering) analysis technology and improvement of the computational speed of personal computers. CAE analysis is also used in production of press- forming dies, and is a focus of interest as a technique for shortening development time and realizing a large reduction in costs. The property values (default values) of general metal materials are recorded in advance in the press-forming simulation analysis software used in CAE analysis, and simple analyses using these values are possible. However, the default values cannot be applied without modification because large differences with the ideal shape of press-formed products occur in simulations only using those values. This means that it is necessary to acquire various property values by using a material testing machine, and apply those values in simulations, in order to achieve high accuracy in press-forming simulations. As described in this article, material property data obtained from a uniaxial tensile test and in-plane reverse loading test using a Shimadzu Autograph precision universal testing machine were applied in simulations. This article introduces an example in which high accuracy simulation of press-forming for an automotive part with a complex shape was successfully achieved by using data obtained from actual measurements, and the profile accuracy coincidence rate with actual press-formed parts was dramatically improved.

July 9, 2019 GMT