ELASTIC-VISCOPLASTIC CYCLIC CONSTITUTIVE MODEL PARAMETER DETERMINATION AND EVALUATION FOR WHEAT EN-MASSE

A set of elastic-viscoplastic (EVP) constitutive equation parameters for cyclic load response is presented for wheat en masse at one moisture content (10% w.b.), two initial bulk densities (801 and 849 kg/m3), and four confining pressures (20.7, 34.5, 48.3, and 62.1 kPa). The chi-square test was used to compare the EVP model predicted deviatoric and isotropic load response with the experimental data. When data for all cycles were pooled in one set, the comparison of the measured and predicted values at the 0.05 level of significance showed that there was no statistical difference for: 1) the deviatoric and isotropic load responses; and 2) the volumetric strain response for high density samples. The cycle-by-cycle comparison of the measured and predicted values at the 0.05 level of significance showed that there was no statistical difference for the deviatoric and isotropic load responses for the first two cycles and the volumetric strain response for high density samples for the first two cycles (except at confining pressure of 34.5 kPa).