Abstract
Mechanical harvesting can be considered an important factor to reduce the costs in coffee production and to improve the quality of the final product. Coffee harvesting machinery uses mechanical vibrations to accomplish the harvesting. Therefore, the determination of the natural frequencies of the fruit-stem systems is an essential dynamic parameter for the development of mechanized harvesting system by mechanical vibrations. The objective of this study was to develop a three-dimensional finite element model to determine the natural frequencies and mode shapes of the coffee fruit-stem systems, considering different fruit ripeness. Moreover, it was carried out a theoretical study, using the finite element three-dimensional model, based on the linear theory of elasticity, for determining the generated stress in a coffee fruit-stem system, during the harvesting process by mechanical vibration. The results showed that natural frequencies decrease as the ripeness condition of the fruit increases. Counter-phase mode shape can provide better detachment efficiency considering the stress generation on coffee fruit-stem system during the harvesting by mechanical vibrations and presented a difference greater than 40 Hz between the natural frequencies of the green and ripe fruit.
Highlights
Coffee price is directly associated with quality parameters
Coffee harvesting can be considered the most expensive operation related to the coffee production chain due to the large labor contingent demanded
Mechanical harvesting can be considered an important factor to reduce the costs in coffee production, since cost reduction is directly related to the mechanization level employed in the execution of operations (BARBOSA et al, 2005; OLIVEIRA et al, 2007)
Summary
Coffee price is directly associated with quality parameters. Fruit selection during the harvesting has an important role in the quality of the final product (CIRO, 2001). Mechanical harvesting can be considered an important factor to reduce the costs in coffee production, since cost reduction is directly related to the mechanization level employed in the execution of operations (BARBOSA et al, 2005; OLIVEIRA et al, 2007). This mechanization process is influenced by the variability of many factors such as Maringá, v. Lewis et al (2007) applied the finite element method on determination of the mechanical damages in apples, through the stress analysis, during its transportation
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