Contact properties determination of macroscopic fine disperse glass particles via compression tests under cyclic loading/unloading

Abstract

To investigate the permanent compressive stress of single particles in a cohesive bulk solid during handling or transport, uniaxial compression tests were carried out with cyclic loading/unloading. This involves a continuation of our previous studies (contact properties determination of macroscopic fine disperse glass particles via compression tests in normal direction). The experiments were implemented by means of a home-built compression tester. By repeated loading/unloading cycles with spherical, dry and smooth soda lime glass particles with a mean diameter of d50,3=513.20μm, a set of micromechanical contact properties was determined. It is a model-based back-calculation of experimentally generated normal force-displacement curves of the elastic-plastic sample material. For this purpose, the contact model ‘stiff particles with soft contacts’, which was developed by Tomas, is used. In order to influence the flowability of soda lime glass particles and to verify the effect of the characteristic adhesion force on the elastic-plastic contact, the particles were altered to be hydrophilic and hydrophobic.Finally, the effect of the number of cyclic loading/unloading tests on the contact stiffness, the effective modulus of elasticity and the resulting contact radius was explained and discussed. According to this, there is an increase of the elastic-plastic contact stiffness up to a saturation of the plastic deformation during the repeated loading of the contact with a constant load rate of FN,max=45N.The determined residual plastic deformations in cyclic compression tests are directly correlated to the densification in the contact area of soda lime glass particles due to the absent long-range order in the glass structure.