NUMERICAL STUDY OF SPALL IN AN ALUMINUM-ALLOY UNDER PLANAR IMPACT LOADING

Numerical analysis has been performed by implementation of a cumulativ e dynamic fracture criterion [1] which depends on the free energy of a ctivation of separation, temperature and the load history. First serie s of calculation has been performed for elastic case to obtain minimum critical spall-fracture stress as a function of critical time of load ing. Next, a viscoplastic constitutive relation which includes the eff ects of strain hardening, strain rate and temperature, along with cumu lative criterion and heat conduction, because of temperature increase due to volume dilatation and dissipation of plastic work, has been imp lemented in FE code. Also, free surface velocity-time profiles have be en calculated for a number of impact velocities, showing creation of n ew free surfaces inside the target plate. The influence of physical pa rameters is discussed on the basis of numerical results.