Study On The Compressibility Of Leymus Chinensis And Its Stress Relaxation Characteristics Analyzed By Virtual Prototyping Technology

The agricultural fiber material is a kind of viscoelastic material. And its compression properties have great effect on the compression process, the compression equipments and the quality of hay products. Therefore, these properties of hay should be studied. This will help us select the compression process, develop and optimize the compression equipments, etc.Given the shortness in present compression theory, the compressibility of leymus chinensis and its stress-relaxation characteristics were studied through experiments in this paper. The factors, which mainly influence the compressibility and stress-relaxation of leymus chinensis, were tested in the experiments. Then the relationships between parameters were discovered after analyzing the results of experiments. Moreover, the stress-relaxation of leymus chinensis was firstly analyzed by the Virtual Prototyping Technology with the virtual prototype model of stress-relaxation.(1) The rules of compression density, compression velocity and initial density influence on the compressibility of leymus chinensis were found out. The results showed that the higher the compression density got, the lower the compressibility of leymus chinensis would be. And when the compression density was higher than 200kg/m3, the compressibility of leymus chinensis would descend quickly. There were no rules for compressibility of leymus chinensis when the compression density was lower than 200kg/m3. But above the 200kg/m3, the compressibility of leymus chinensis would be better with higher compression velocity at the same initial density. However, the compressibility of leymus chinensis would be lower when the initial density was higher. According to the same compression velocity, the compressibility of leymus chinensis would descend quickly with higher initial density during compressing process.(2) The best compression density range of leymus chinensis was found out according to the compressibility of leymus chinensis. In respect to different initial densities and compression velocities, the range is 200~300kg/m3.(3) The stress-relaxation rules of leymus chinensis under different initial densities and compression velocities were discovered. Then the rheological model of stress-relaxation was established. It included two Maxwell Models and one spring with a parallel connection. The equation of stress-relaxation is ( ) (4) The opinion that the compression frequency of equipments can be decided by stress drop time when the compression density is higher than 400kg/m3 was put forward. According to the stress-relaxation of leymus chinensis, there was a stress drop during the process when the compression density is higher than 400kg/m3. Of the different initial densities, the higher the compression density was, the clearer the phenomenon (i.e. stress drop) would be. However, this phenomenon would disappear in only one second. And the best compression frequencies of different compression densities under different initial densities were analyzed and calculated. The results showed that the compression frequency would be lower while the compression density was getting higher at the same initial density. But when the compression density was the same, the initial density had a little influence on the compression frequency.(5) The virtual prototype model of stress-relaxation was established by the Virtual Prototyping Technology. And the correctness of the model was verified by comparing the simulation curve with experiment curve in ADAMS/PostProcessor. With the virtual prototype model, the stress and deformation velocity of elements in the stress-relaxation model were analyzed. Then the stress-relaxation process of leymus chinensis was simulated through ADAMS. So the rules of stress-relaxation of leymus chinensis and every element in the model could be observed and analyzed in real time.