Modeling stress relaxation response of wheat en masse using the triaxial test

Time dependent load response data were obtained from triaxial tests to characterize the stress relaxation behavior of wheat en masse. Stress relaxation data were measured for two axial strains, two confining pressures, two moisture contents, and two initial bulk densities. The generalized Maxwell model was used to simulate the stress relaxation response of wheat. The test data were transformed into dimensionless quantities using initial or maximum elastic modulus E_max and half relaxation time T₅₀. The data converged for t < T₅₀ using dimensionless modulus φ = E/E_max as dependent variable and dimensionless time θ = t/T₅₀ as independent variable. Two boundary condition variables - confining pressure and axial strain, significantly affected the initial elastic modulus; whereas, three variables - confining pressure, initial bulk density and moisture content, significantly affected the half relaxation time.