Theoretical Simulation of Stress-Strain Relations for Some Iraqi Clays Using the Endochronic Model


A constitutive law can be defined as a mathematical functional relation between physical quantities such as stress and strain and may take other factors like time ,temperature and additional material properties into account. In this paper , the endochronic model is used to predict the stress-strain relations of two Iraqi clays. This model is a viscoplastic one but without introducing a yield surface. It encompasses material behaviour such that the current stress state is a function of strain history through a time scale called “intrinsic time” which is not the absolute time but a material property. The simulation showed that the model overestimates the strains for all cases studied. This may be attributed to the material parameters which require a parametric study to determine their actual values for Iraqi clays