Construction of constitutive model and parameter determination of green Sichuan pepper (Zanthoxylum armatum) branches

The harvesting of green Sichuan pepper (Zanthoxylum armatum) is achieved by cutting the branches, and it is important to investigate the biomechanical properties of the branches for harvesting. In this study, based on the elastic mechanics of composite materials, the Yamada and Sun yield strength criterion, hardening model, and flow law were selected, and a damage factor was introduced to establish the constitutive model of green Sichuan pepper branches. This model can characterise the complex biomechanical properties of green Sichuan pepper branches, which provides a new way and saves time for green Sichuan pepper branch testing, and lays a theoretical foundation for the design and optimisation of green Sichuan pepper production machinery. Furthermore, the constitutive parameters of the green Sichuan pepper branches were measured for the first time to meet the needs of the established model. In addition, an effective bending indenter-branch finite element model was established by compiling the constitutive model into the simulation software Abaqus through the Umat subroutine, and a three-point bending simulation test was conducted on the branch of green Sichuan pepper. Finally, relative deviation from maximum pressure founded to be less than 6% by comparing the experimental results with the simulation, which proved that the model was reliable and the measured constitutive parameters were accurate. Looking forward, these findings may contribute to the development of green Sichuan pepper harvesting equipment worldwide.