Mathematical models describing the relaxation behaviour of Jatropha curcas L. bulk seeds under axial compression

• Wiechert model with three branches and five elements was suitable.
• Peleg model similarly described the relaxation behaviour of Jatropha bulk seeds.
• Wiechert model with two branches and three elements was inappropriate.

Mathematical models to describe the relaxation response of Jatropha curcas L. bulk seeds in axial compression were investigated. Models investigated included two Wiechert models, model A with three branches and five elements and model B with two branches and three elements denoted as model B. The Peleg model was also investigated. Relaxation stress and time dependence were determined during the relaxation process at strain values of 0.56, 0.63, 0.69, 0.75 and 0.81 for Jatropha bulk seeds at an initial pressing height 80 mm and the results fitted to the mathematical models. Based on the relaxation characteristics of the bulk seeds, it was observed that the Wiechert model A and the Peleg model better described the experimental data and it was not easy which of the two was the most suitable. The Wiechert model B did not suitably describe the relaxation behaviour.