MECHANICAL PROPERTIES AND CONSTRUCTION OF CONSTITUTIVE MODEL FOR COMPRESSION AND STRESS RELAXATION OF CATTLE MANURE

Abstract

In order to study the mechanical properties of compression and stress relaxation of manure under drainage conditions, the experiment was carried out with cattle manure as the object, and the constitutive models were improved to describe the stress-strain curves of compression and stress relaxation. The defined constitutive model was determined by parameter identification, and the influence laws of moisture content and filling mass on the compression and relaxation process were investigated. The results show that the improved Nishihara model and the five-component generalized Maxwell model can better describe the compression and stress relaxation properties of cattle manure, and the coefficients of determination of the parameters of the fitted intrinsic model are all greater than 0.9, with high fitting accuracy. The compression process was divided into three stages: exhaust, drainage, and viscoelastic-plastic deformation. The stress decay rate tended to change quickly and then slowly, and there was a negative correlation between the compressed mass, moisture content, and stress decay rate. Duncan's mean comparisons revealed that the differences in elastic modulus between different moisture content / compressed mass groups in the parameters of the cattle manure compression principal model were all significant (P<0.05). The differences in elastic modulus and coefficient of viscous attenuation between different moisture content groups in the parameters of the stress relaxation model were all significant. The study's results can provide the theoretical basis for the study and simulation of CM's compression and dewatering mechanism and provide support for the solid-liquid separator for livestock and poultry manure.