Abstract
Seed cotton compression molding solves the inconvenience of seed cotton transportation and storage after mechanical harvesting. Stress relaxation is closely related to the performance of the compressed seed cotton. In this study, an electronic universal testing machine with a homemade compression device was used to study the stress relaxation characteristics of machine-harvested seed cotton. The stress relaxation model of machine-harvested seed cotton was established, the influence of test factors on the response indexes was analyzed and, finally, stress relaxation characteristics of machine-harvested seed cotton were simulated. Results show that machine-harvested seed cotton stress relaxation characteristics can be described by the five-element Maxwell model. The equilibrium elastic modulus is negatively correlated with moisture content and cross-section dimensions, and the equilibrium elastic modulus is positively correlated with trash content and compression density. The rapid decay time and the residual stress ratio are negatively correlated with moisture content and compression density, but the influence of trash content and cross-section dimensions are limited. The stress relaxation process of machine-harvested seed cotton was simulated using virtual prototype technology, and the maximum error between the experimental and simulated values was obtained as 4.96%. The feasibility of the virtual prototype technique for the viscoelastic simulation of biomaterials was demonstrated.
Highlights
Cotton, flax and hemp plants are the main textile materials in the world [1]
We investigated the effect of moisture content, trash content, compression density and cross-sectional dimensions on the stress relaxation characteristics of machineharvested seed cotton through stress relaxation tests during the harvest period
Using Origin 2017 to fit the regression to it using the Maxwell model and generalized Maxwell model, we can obtain the expression of stress relaxation characteristics of machine-harvested seed cotton, which can be used in 2 Maxwell cells and 1 equivalent spring parallel five-element model [23], as shown in Figure 3a, and the expression is shown in Equation (3)
Summary
Flax and hemp plants are the main textile materials in the world [1]. While cotton is an important material, it is one of the most important economic crops in Xinjiang, China, where the main planting of cotton is upland cotton [2,3]. Cotton harvested by cotton pickers is collectively referred to as machine-harvested seed cotton, which has a small bulk density and belongs to a loose agricultural fiber material [6]. Research on the stress relaxation characteristics of common agricultural fiber materials has matured. The compression, stress relaxation and creep of the material have been investigated, and rheological models have been developed to analyze the effects of moisture content and compression force on their rheological properties [26,27,28,29,30]. We investigated the effect of moisture content, trash content, compression density and cross-sectional dimensions on the stress relaxation characteristics of machineharvested seed cotton through stress relaxation tests during the harvest period
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