Modal properties of macaw palm fruit-rachilla system: an approach by the stochastic finite element method (SFEM)

Abstract

In the last few years, the trend towards the use of fossil fuels has been enormously discouraged, driving research and development into new energy sources, joining efforts from both the scientific community and industry. The global trend to increase the use of renewable energy sources is essential to develop appropriate technologies for the cultivation and management of crops in order to obtain production on an industrial scale, associated with the least environmental impact. The Macaw palm (Acrocomia aculeata), a palm tree native to Tropical America, has great potential as a raw material for the biodiesel production. Macaw palm fruits can be harvested by mechanical vibrations and the modal properties identification, such as natural frequencies and modes of vibration, of the fruit-rachilla system is fundamental for the development of harvesting machines and devices that use this principle. This paper presents a systematic approach to identify the modal properties of macaw palm fruit-rachilla system, when the inherent variability of the biological systems are involved. The inherent variability of the specific mass and elasticity modulus of the fruit-rachilla systems of macaw palm in different plantation sites, as well as the influence of the fruit maturation stage, were considered in the analysis, as random variables. Using the stochastic finite element model it was possible to determine the spectral response of the natural frequencies of interest, as well as its statistical parameters in order to serve as base of knowledge for design harvesting machines. The analysis and discussions had contributed to establish three possible operating frequency ranges to design macaw palm harvesting machines.