Transfer rule of compression and springback stress in compression process of alfalfa

This study attempted to investigate the transfer rule of the axial stress and spring-back models at the different locations of the compression chamber in the compression process of alfalfas, in which the alfalfa was compressed from the loose state into a grass piece. In order to measure the axial stress, including the compression and spring-back stress, the 10 moveable pressure sensors were used for the cross-section size of the compression chamber, and 2 pressure sensors and 3 displacement sensors were installed in each section. All data was imported into the software Matlab and the axial stress curves versus the location of the grass piece in the compression of alfalfa were given. Then curve fitting of the maximum stress and the minimum spring-back stress were done respectively, the transfer rule of the compression and spring-back stress and the corresponding mathematic model were obtained. The study revealed that the envelop line of minimum sping-back stress increased with increasing compression displaceme