DEVELOPMENT OF A GENERAL CONSTITUTIVE RELATIONSHIP FOR AN ELASTIC/VISCOPLASTIC MATERIAL UNDER HIGH RATES OF LOADING

The dynamic behavior of a cohesive soil under high rates of loading has been studied. The experimental results on the soil specimens indicated that the material displays elastic and viscoplastic response under high rates of loading conditions. The viscoplastic response which reflects the nonlinearity and work-hardening behavior of the material was found to be highly affected by the rate of loading. The general constitutive relationship for the test material was developed based upon an elastic/viscoplastic relationship for a rate sensitive material. In order to obtain the general constitutive relationship, various uniaxial impact loading tests were performed on a specially designed fabricated split Hopkinson pressure bar (SHPB) test apparatus. The tests were performed for several axial strain rates ranging from 50 in/in per second to 250 in/in per second. Uniaxial stress pulse tests were also conducted by subjecting the specimens to various hydrostatic confining pressure ranging from 0 to 40 psi. Based upon the experimental results, a yield criterion as defined by Drucker and Prager was developed to characterize the viscoplastic behavior of the soil material.