Dynamic test for determining the elastic modulus of coffee fruit-stem-branch system

Abstract

The finite element method, which has been used to determine natural frequencies and mode shapes, is used to generate and solve differential equations that describe the investigated physical phenomenon. However, this method requires the use of geometric and mechanical properties as input parameters, which may be difficult to obtain experimentally. The objective of this study was to develop a method for determining the elastic moduli of coffee stems and branches by comparing the experimentally obtained natural frequency with the frequency obtained using the finite element method. The natural frequency was experimentally obtained using a dynamic sweep test of frequencies, in which the fruit-stem-branch system was excited over a range from 10 to 30 Hz. The natural frequency of the fruit-stem system was higher at the green stage than at the cherry stage, and the elastic modulus of the stem at the cherry stage was higher than for the green stage. The mean elastic modulus values were 15.74, 23.90 and 4645.90 MPa for the stem at the green and cherry stages and for the branch, respectively.