Finite element modal analysis of the fruit-peduncle of Coffea arabica L. var. Colombia estimating its geometrical and mechanical properties

• Geometric model of fruit-peduncle system (Coffea arabica L. var. Colombia).
• Mechanical properties of fruit-peduncle system (Coffea arabica L. var. Colombia).
• Finite element modal analysis of a coffee fruit-peduncle system.
• Results: Elastic properties and validation of the geometric model.
• Results: Identification of natural frequencies and modes of vibration.

This study shows a heuristic process for identification of natural frequencies and modes of vibration of the fruit-peduncle system of Coffea arabica L. var. Colombia by means of a modal analysis. From experimental data, the real topology of the fruit-peduncle system was approached with a proposed theoretical model. The geometric models can be generated in any ripening stage and these showed a good agreement when these are compared with real coffee fruits. The elastic properties of the fruit were determined from a sensitive analysis using experimental data of firmness for each ripening stage. It was observed that with the increase in the days of ripening, the fruit loses its elastic capacity. From a finite element modal analysis, the natural frequencies were identified for the fruit-peduncle system and the first 20 modes of vibration were selected and analyzed. A dynamic criterion was established to identify and define frequency intervals in which the modes of vibration produce rotations at the fruit-pedicel interface. The results shows that the modes associated to natural frequencies in specific intervals probably facilitate the separation between the interface fruit-pedicel for the ripe stage but these intervals are different from other ripening stages. The heuristic process developed in this study may be extrapolated to other varieties of coffee.