An empirical model for friction force versus relative displacement between maize, rice and soybeans on galvanized steel

Shear tests were performed to study the frictional response of three types of grain, maize (shelled corn), rice and soybeans on galvanized steel surfaces. The friction (tangential) force and the relative displacement between grain and a galvanized flat sheet steel surface were measured for normal pressures between 9.8 kPa and 38.8 kPa. Based on the experimental data, an empirical model is proposed for simulating the pre- and post-peak frictional force as a function of relative displacement. Comparison of the test data with empirical model values showed that: (a) the average relative differences were 8.0, 11.5 and 6.8% for maize (shelled corn), rice and soybeans, respectively, (b) at the high normal stress (38.8 kPa), the empirical model values were larger than the measured values, whereas at the low normal stress (9.8 kPa), the model values were smaller than the measured values, and (c) the χ² test, at the 0.05 level of significance, verified the goodness of the empirical model for simulating the frictional behaviour.