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Technical Paper

Properties of a Newly Developed Galvannealed Steel Sheet with Modified Surface

A galvannealed steel sheet (GA) with a Ni-base inorganic lubricant film has been developed to meet the needs of the automotive industry, especially for improved press formability. This paper describes the results of tests performed to evaluate formability, spot weldability, phosphatability, paintability and corrosion resistance of the GA with the Ni-base lubricant film. The coefficient of friction as measured by flat sliding test decreases with increasing Ni content in the lubricant film. The spot weldability evaluated by electrode tip life test is slightly improved after the application of the lubricant film. Phosphatability, paintability and corrosion resistance of the GA with the lubricant film are equivalent to those of GA without the lubricant film.
Technical Paper

A Study on Improving Crashworthiness of Automotive Parts by using High Strength Steel Sheets

In order to estimate and improve the crashworthiness of practical automotive parts, dynamic crash test was conducted by using double hat specimen composed of the materials with different strength and thickness. Estimation method of the average force of the specimen was discussed. From the test results, it was clear that absorbed energy of the specimen composed of the materials with different strength and thickness of plate can be evaluated from the linear mixture law for the relations of the absorbed energy and the thickness of the materials used. And the “effective width theory” is useful way to estimate the average force of the parts.
Technical Paper

Crashworthiness of Automotive Stamped Parts Using High Strength Steel Sheets

Forming and strain rate effects on crashworthiness of automotive body components were investigated in this study. Dynamic tensile tests were carried out to establish the stress-strain relationships at elevated strain rates. Dynamic tests of bending and axial crashing at various speeds were conducted using a stamped hat square column. The experimental results indicate that the absorbed energy of the hat square column decreased with the increase of material thinning in case of high strength steels. FEM analyses using material models with both strain rate sensitivity and forming effects were carried out to evaluate the computer prediction accuracy of crashworthiness.
Technical Paper

Dent Simulation of Automotive Outer Panel Using High Strength Steel Sheets

In this study, an FEM simulation method was investigated in order to predict the dent resistance and stiffness performance of automotive exterior body panels. The method was based on the combination of a forming simulation and a static dent simulation. The dent simulation was carried out with material models taking forming effects, such as work hardening and thickness variation into account. The modeling method of material properties with the forming effects was discussed to improve the prediction accuracy. For the validation of the accuracy, forming and denting tests were carried out for a door model panel using mild steels or high strength steels. The results of the dent simulations showed good agreement with the experimental results.