Spruce pellets in compression loading

Abstract

Compression loading of sawdust pellets could be useful for studying the mechanical and structural properties of materials. Mechanical properties such as the failure stress and strain, the modulus of elasticity, the bulk modulus, the compressibility and the deformation energy can be used to evaluate the behaviour of pellets under static loading. The deformation energy as the apparent energy density was determined by integrating loading stress-strain curves between the initial point and the point of strength failure. A testing machine Andilog Stentor 1000 was employed for compression testing. The pellet samples were tested at a constant speed of 10 mm.min-1. The true stresses and the Hencky's strain were determined in compression loading. The Cauchy's strain gives the relative deformation with regard to the initial sample height. The Hencky's strain derives from the integration of the infinitesimal strain. The true stress is evaluated using the instantaneous cross section of the sample. The loading curves of the dependence of the stress on the strain were realized, and the moduli of elasticity and the bulk moduli were determined from the compression diagrams respectively.