The adiabatic shear band formation is one of the high speed deformation phenomena, in which adiabatic shear failure is physically observed as a narrow band of the continuous shear strain. The localized shear strain is generally of a magnitude far higher than the material would normally be expected to sustain without fracture. The adiabatic shear band plays a significant role in the area of high speed rotor, high speed forming, high speed machining and penetration of a target by a projectile.
In this study, the experiment and finite element analysis of the formation of an adiabatic shear band in sheet metal are carried out for high strength steel sheet 60C and 60TRIP. In order to carry out experiments with a tension split Hopkinson bar, shear specimens are designed to induce large shear strains. The shear deformation of the two sheet metals of 60TRIP and 60C is quite different and the adiabatic shear band is observed with 60C only. The width of a shear band is measured by comparison of the hardness in a crack tip. The shear deformation in 60TRIP is restrained and the crack is propagated by a tensile mode since the strain hardening of 60TRIP in the high strain rate is large. The load-displacement curves show that the load with 60TRIP becomes higher than that with 60C as the displacement increases.
Numerical simulations are carried out with an elasto-plastic explicit finite element method. In order to integrate the Johnson-Cook constitutive equation over a time step, the plastic predictor-elastic corrector (PPEC) method is used. The stress could be accurately calculated in a single step with no iteration. For the numerical integration, the reduced integration scheme is used to reduce the computation time and eliminate the locking problem. An assumed strain method is used to control the hourglass mode. The shear localization calculated from the numerical simulation shows similar behavior to experimental results.
