Firmness evaluation of melon using its vibration characteristic and finite element analysis

Abstract

Analysis of the vibration responses of a fruit has been suggested as a non-destructive measure of its elastic properties (firmness). In this study, 'Huang gua' melons were excited using three types of balls (wooden, steel and rubber) and the vibration was detected by an accelerometer. The modulus of elasticity of the inner, middle and outer portions of melon flesh were determined using flat plate compression of cylindrical samples. The Instron device was used to measure the static elastic modulus and the Finite Element (FE) technique was used to determine the optimum location of the excitation on fruits. Four types of mode shapes were found: torsional or flexural mode shape, first-type of longitudinal mode shape, second-type of longitudinal mode shape and breathing mode shape. The results from FM simulation were in good agreement with experimental results and there was good correlation between the fruit firmness and its resonant frequency.