Limiting stresses and elastic properties of biological material under axial and radial compression as related to their handling and containerization

Abstract

This is a report on the evaluation of elastic properties of UTC tomato fruit to determine the maximum contact pressure, contact stresses and elastic modului relevant to design of transportation system of the biomaterial. A universal compression test rig developed at the Department of Industrial and Production Engineering of the Nnamdi Azikiwe University, Awka, Nigeria was used to test the biomaterial properties under axial and radial loading condition to ascertain the engineering stress-strain, true stress-strain, isotropic and anisotropic condition of the material under investigation. The elastic properties evaluated under longitudinal(axial) and transverse loading were found to be approximately the same, giving the elastic modulus and Poisson’s ratio for engineering stress-strain as 0.1628MPa and 0.2563 respectively while the transverse loading gave 0.2158 and 0.2596 respectively. The Hertz’s maximum contact pressure was evaluated as 0.063MPa at contact radius of 0.01m, while the principal Hertzian stresses were equally evaluated and the maximum shearing stress of 0.3Pmax = 0.02281MPa while maximum principal stress was found to be -0.0736MPa. Above all the study found that within the elastic limit the material biomechanical properties are isotropic giving approximate elastic modulus of about 0.2MPa and Poisson’s ratio of 0.3 and the shear modulus of 0.06479MPa-0.0857MPa. Other properties evaluated are the ultimate compressive strength which was found within the range 14.595KPa-16.7731KPa, fracture limit found within the range 12.3250KPa - 14.3940KPa, while the bioyield point was found to be within the range 8.7961KPa-9.4666KPa. The designers of transportation for tomato should therefore ensure that the maximum contact stresses between the tomato and container does not exceed the maximum contact pressure and the maximum shear stress evaluated in this study.