Authors

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.

Abstract in Chinese

压缩过程中粪污的力学特性尚不清晰，严重制约固液分离机具的优化改进。为研究排水条件下牛粪压缩及应力松弛的力学特性，以牛粪为对象开展试验，分别采用改进西原模型和五元件广义 Maxwell 模型对压缩和应力松弛的应力应变曲线进行描述。通过定义的本构模型对不同含水率、压缩质量的牛粪力学试验数据进行参数辨识，确定相关模型参数，并探究各因素对压缩及松弛过程的影响规律。研究结果表明：改进西原模型、五元件广义 Maxwell 模型可以较好地描述牛粪压缩、应力松弛特性，拟合求解的本构模型参数决定系数均大于 0.9，拟合精度高。压缩过程分为排气、排水和粘弹塑性变形3个阶段；应力衰减速率呈先快后慢变化趋势，压缩质量、含水率与应力衰减速度呈负相关关系。Duncan均值比较结果发现：牛粪压缩本构模型参数中不同含水率/压缩质量组间弹性模量差异均显著（P＜0.05）；应力松弛模型参数中不同含水率组间弹性模量和粘性衰减系数差异均显著（P＜0.05）。压缩与应力松弛力学特性的研究结果可为牛粪压缩脱水机理研究、仿真模拟提供理论依据，为畜禽粪便固液分离机具提供支撑。