Papers by Author: Jun Ying Min

Abstract: To study the effects of temperature and thickness on forming limits of boron steel 22MnB5, Nakajima tests have been performed for the steels with thickness of 1.0mm and 1.4mm at 600°C and 700°C, respectively. The forming limit curve (FLC) of the steel at 700°C is higher than that at 600°C, and the FLC of the steel with 1.4mm is higher than that of the steel with 1.0mm. With increasing the forming temperature, the strain rate sensitive exponent m increases, and it results in a longer Swift’s diffuse instability phase and greater limit strains. The effect of thickness on yield path is different from the case at room temperature, due to the half angle of pointed Vertex, θ₀, which increases with increasing of the thickness, and then the limit strains increase.

Abstract: The finite element model of bulging at elevated temperature was established by using of pam-stamp 2007. The bulging tests of boron steel sheets were also performed on the self-designed and manufactured tool system. The simulated results of bulging height, limit strain and the minimum temperature of specimens are consistent with that of tests. It demonstrates the validity and accuracy of the finite element model established in pam-stamp. The influences of the friction coefficient, the temperature and the stamping velocity on the hot bulging are analyzed numerically. The friction condition should be improved and the minimum temperature gradient is recommended in practical hot stamping production.