Projectile Impact Of Steel In The Process Of Adiabatic Shear Behavior

As the hardness of steel plate increasing, the resistance of steel plate against the projectile impact increases obviously, and it has become an effective way to improve the ballistic behavior by adopting steel plate with high hardness. While the hardness get to the stated level, plugging failure absorbed lower energy turn into the one of the most common failure during projectile impact the target, and adiabatic shear band is considered to be the important reason for the plugging failure. So it is very significative to give comprehensive studies on adiabatic shear band in order to improve the ballistic behavior. In this paper, adiabatic shear behavior was studied by the way of combining experimentation with simulation. The experimentation mostly studied adiabatic shear band produced during projectile impact 40CrNi2Mo steel after tempered at different temperatures. The form and distribution of adiabatic shear band, the microhardnesses of adiabatic shear band in the matrixes tempered at different temperatures, and the microstructural characteristic of the adiabatic shear band were emphasize. The processes of simulation made use of the finite element software ANSYS/LS-DYNA to study adiabatic shear behavior during projectile impact the target. The influence of different shapes and at different strength to the adiabatic shear behavior were chiefly studied.It was found that the form and distribution of adiabatic shear band had obvious differences in the steel plates tempered at different temperatures. Adiabatic shearing sensitivity was relevant to the hardness of steel, and it was easy to find adiabatic shear band in the steel plate with high strength. The hardness of adiabatic shear band was much higher than the hardness of the matrix, having no relation to the hardness of the matrix, and the hardness of adiabatic shear band decreased after it was heat treated again, so the adiabatic shear band under this experimental condition was a transformed band. Adiabatic shear band consisted of two areas: the transition area and the center area. The transition area of adiabatic shear band was composed of heavily distorted martensite laths, while within the center area, which was made of fine equiaxed grains with the size 200～300nm, there was an phase transformation. With the hardness of the steel plate decreasing, the width of the transition area increased.The simulation results showed that when the flat projectile and the sharp projectile impacted the target, the concentration of strain arised more easily during the flat projectile impacted the target, and the adiabatic shear behavior occured. The stress and the strain of target element were obviously different, and resulted in the obvious difference of the target's damage form. The differences of the stress and the strain explained the difference of adiabatic shear behavior too. The simulation of projectile impacted the target showed that adiabatic shear behavior produced more easily in the target with high strength, and it was coincident with the results exhibited by the early experimentation.