The bending behavior investigation of plants with elliptical cross-section and tapered stalks (case study: privet stalk)

Abstract

Unlike metals with elastic behaviour, most agricultural products are viscoelastic and they behave differently under various loads. With knowledge of agricultural products behaviour, it is possible to fabricate the best operation machine. To design a new hedge trimmer machine, the bending behavior analysis of hedge plants stalks like privet were carried out. Given that the privet stalk is similar to tapered rod and cross-section of the stalk is oval, the stalk specimens were performed in a bending process at rate of loading from 5 to 20mm/min, four internode positions of fifth, tenth, fifteenth and twentieth and two directions of applying force of x direction (major diameter of the stalk cross-section) and y direction (minor diameter of the stalk cross-section). The variance analysis of the data indicated that the loading rate and internode position created a significant effect on the stalk Young’s modulus and bending strength (P<0.05) in the both force applying directions. Also the moisture content created a significant effect on the stalk Young’s modulus and bending strength (P<0.01) in the both force applying directions. The results showed, the Young’s modulus at y direction of applying force had about 10-20% higher values than that of the x direction for all loading rates, moisture contents and internode positions. Also the bending strength at y direction of applying force had about 5-10% lower values than the x direction for all loading rates, moisture contents and internode positions. Results show the maximum value for the privet stalk Young’s modulus was found to be 14.20Gpa for the moisture content of 30% at bending speed 5mm/min and y direction of applying force and the minimum value was found to be 5.06Gpa for the moisture content of 75%, at bending speed 20mm/min and x direction of applying force.

Keywords: Bending stress, Force, Major diameter, Minor diameter