• Demazel, N.
• Laurent, H.
• Carin, Muriel
• Boyer, A.
• Coër, J.
• Oliveira, M. C.

Abstract

International audience ; A novel hydraulic bulge test device was developed to evaluate high temperature biaxial stress–strain curvesof quenchable boron steel sheets. The work mainly focuses on the resistance heating designed to assure ahomogeneous temperature field in the dome area of the circular blank where the hydraulic pressure will beapplied. The practical hot stamping conditions, including the heating and cooling steps, were reproduced toperform hydraulic bulge tests on the Usibor®1500P steel for a temperature range between 700 to 900 ◦C, afteran austenization step at 900 °C. Stress–strain curves were obtained from these expansion tests using the dataextracted with a laser profilometer, due to the difficulties associated with the use of Digital Image Correlationat such high temperatures. Although the profilometer is a compromise solution, the comparisons betweentensile and biaxial stress–strain results enable to verify the feasibility of the new device for the evaluationof the stress–strain curves at a high temperature in a biaxial state. The results point-out that, besides thedifficulties with the acquisition of the strain fields and in the strain-rate control, there are also challenges inthe interpretation of the metallurgical evolutions that can occur during the tests, which can affect the biaxialflow curves.

Topics

• impedance spectroscopy
• steel
• stress-strain curve
• Boron
• forming
• formability test