Modeling and evaluation of a threshing drum under vertical vibration

Abstract

A threshing drum in a power thresher has a main function for separating seeds from stems via threshing teeth. This part undergoes with high exposure of vibrations, which has a greater chance to work improperly and experiences a fatigue failure that can reduce the efficiency. The main objective of this paper is to obtain vibration characteristics of the proposed design of the threshing drum. In order to achieve the objective, the threshing drum is to be modeled as an equivalent spring and a mass, which is coupled in series mode with equivalent springs and dampers generated from bearings. The mathematical models of the system are derived only in vertical direction. The transfer function approach is established to obtain time and frequency domain analysis. Force and displacement transmissibility are plotted in the wide range of frequencies to perform transmitted force to the main frame, while vertical vibration exposures are evaluated based on ISO 2372. The result shows that the threshing drum design is in the good criterion that means the Root Means Square of the velocity lying from 0.11 m/s to 2.8 m/s taken from vibration severity index in the range of 400 rpm to 1000 rpm.