Vibration and strain signal acquisition for numerical simulation of a coffee harvester

Abstract

Coffee harvesters utilize vibration systems to dislodge coffee beans. The vibration system is usually coupled to the end of an axis (rod cylinder). This cylinder can fail in the field, which usually occurs by means of cracks close to its flange in the region that promotes vibration. Numerical simulations are typically used to predict strains and stresses based on vibration signals in machines in general. This work acquired the vibration and strain signals of a coffee harvester rod cylinder prototype and compared the results using finite element analysis. To this end, a rod cylinder system was prototyped on a reduced scale (1:3) to recreate frequency and strain data, which were used for numerical simulation comparisons. The results showed that the predicted von Mises stress in the analyzed zone was 16.47 MPa (below the material yield strength, 250 MPa) based on a frequency of 14.2 Hz applied to the rod cylinder. This confirmed that cracks found in rod cylinders in the field are not generated by high stresses, as reported in the literature. The results demonstrated the potential of finite element analysis for strain and stress prediction when applied to agricultural machine components.