Methods for the Definition of the Destruction Deformation of High Strength Sheet Steels Depending on the Deformation Rate

The complex of methods necessary to experimentally study the effect of the deformation rate on the high strength sheet steels (as exemplified by DP780, DP980, and BH240 steels) on the increase in their plasticity during uniaxial and biaxial stretching is determined. The deformation rates of steels were measured in a wide range from 10 –4 to 17 × 10 3 s –1 . An FP 10/1 HECKERT tensile testing machine, a P6324 hydraulic press with special tools, a Hopkinson–Kolsky machine and a T1226B electro-hydraulic press were used. The deformations of the materials destructed during the biaxial stretching were defined using a control grid on their surfaces. Dependences of the destruction deformations of DP780, DP980, and ВН240 steels vs. the deformation rate and their stress-strain state showing an increase in plasticity of DP780 steel up to 2.9 were determined.