Failure of Dynamically Loaded Thermoelastoviscoplastic Rectangular Plate

The initiation and propagation of a crack and an adiabatic shear band in three-dimensional finite coupled thermomechanical deformations of a homogeneous and isotropic thermoelastoviscoplastic rectangular 4340 steel plate containing a centrally located through-the-thickness elliptic void and deformed in simple tension are analyzed numerically by using thefinite element computer codeDYNA3D. Initially, themajor and theminor axes of the elliptic void coincide with the centroidal axes of the plate. An element is assumed to have failed when the damage parameter defined in terms of histories of the effective plastic strain, the effective plastic strain rate, the triaxiality factor, and the temperature at its centroid equals one; an adiabatic shear band initiates at a point when the effective plastic strain there equals one, while the material point is deforming plastically and deformations of the surrounding material are inhomogeneous. It is found that the ratio R of lengths of the two principal axes of the void significantly influences when and where a crack and an adiabatic shear band initiate and which one initiates first. They usually originate fromapoint on the surface of the elliptic voidwhich is also on themidsurface of the plate, and they propagate faster in the thickness direction. An adiabatic shear band initiates sooner in the three-dimensional simulations than when displacements in the thickness direction are constrained to vanish. The crack tip follows a zigzag path that does not lie in one plane.