Mechanical properties of the macaw palm fruit-rachilla system1

Abstract

The fruit of the native macaw palm [Acrocomia aculeata (lacq) Lood. ex Mart] is an alternative for biodiesel production because of the plant characteristics, as well as its adaptability, hardiness and high vegetable oil yield. However, its exploitation remains extractive and there are significant difficulties in its harvest. This study aimed to determine the mechanical properties of the macaw palm fruit-rachilla system that will support the design of harvest machines based on mechanical vibration. Ten samples of four accessions in the immature and mature stages of maturity were used. Traction and vibration tests were conducted to determine the mechanical properties of the macaw palm fruit-rachilla system. The elastic modulus of the rachilla was 188.39-385.09 MPa for the immature stage and 109.02-320.54 MPa for the mature stage. The Poisson's ratio for the rachilla varied between 0.20 and 0.52 for the immature stage and between 0.16 and 0.52 for the mature stage. The damping ratio varied between 0.02 and 0.12 for the immature stage and between 0.06 and 0.12 for the mature stage. The fruit-rachilla system was characterized as underdamped.

Dynamic behavior of the macauba palm (Acrocomia aculeata) fruit-rachilla system using the stochastic finite element method

“…Tables 1 and 2 show the specific mass values of the fruit and rachilla of the macauba palm as well as the elasticity modulus of the rachilla according to the study of Rangel et al (2019). Velloso, Santos, Pinto, Villar, and Valente (2017), evaluating the relationship between the maturation stage and the physical properties of the macauba palm, found values close to those obtained in this work for fruit size. The mean modulus of elasticity values found in this study were 100-fold higher than those obtained by Villar, Pinto, Santos, Grossi, and Velloso (2017).…”

Geometric, Physical and Mechanical Properties of the Fruit-rachilla of the Macauba Palm (Acrocomia aculeata) Considering Different Sampling Sites in the State of Minas Gerais in Brazil

“…Regarding the green and ripe fruit maturation stages, in sampling sites BD27 and BGP29 was observed an increase and a decrease in mean fruit diameter, respectively, along fruit maturation (Table 1). Velloso et al, [9] evaluated solely the different fruit maturation stages and obtained diameter values that did not differ significantly.…”

Modeling and simulation of the dynamic behavior of the macaw palm fruit-rachilla system

“…38 Thus, the natural frequency of the fruit-rachilla system tends to undamped natural frequency. 14,15,38 For modeling, a system with multiple degrees of freedom was considered and can be represented by the matrix equation ½Mf€ xg + ½Kfxg = fFg, where [M] and [K] are symmetric matrices of mass and stiffness, respectively; {x} and f€ xg are the vectors of displacement and acceleration, respectively; and {F} is the vector of the external forces applied.…”

“…11,12 Domestication, physical properties, and fruit harvesting systems have been studied to learn how to obtain quality raw material for macaw palm production. [13][14][15][16][17][18][19] The use of computational modeling through numerical simulations is a skillful way of designing, understanding, and evaluating harvesting mechanisms without the need for destructive testing and the design of prototypes. [20][21][22][23] It is believed that the principle of mechanical vibration is applicable to the harvest of macaw palm fruits, 18 so the determination and knowledge of modal properties, natural frequencies, and modal forms of the plants, or part of them, are necessary when computationally studying the behavior and the interaction of the plant with the machines that can promote the harvest of its fruits.…”