摘要
A combination of a continuum approach and a particleparticle approach to describe the multiscale nature of the mechanical properties of bulk solids may be beneficial to scientific and engineering applica tions. In this paper, a procedure is proposed to estimate the interparticle forces beginning with the bulk flow properties as measured with standardized techniques. In particular, the relationship between inter particle forces and bulk solid tensile strength is adopted based on the microscale approaches of Rumpf （1970） and Molerus （1975）. The flow properties of fluid cracking catalyst （FCC）, corundum and glass bead powders were all characterized with a modified Schulze ring shear cell capable of operating at tempera tures up to 500 ~C. The powder test conditions were selected such that the van der Waals forces were the most significant particleparticle interactions. The model equations describe two cases, in which either elastic or plastic deformation of the contact points is assumed. The results indicate that the model pro vides the correct order of magnitude for the values of the tensile strength when proper values for the mean curvature radius at the contact points are taken into account. A sensitivity analysis for the main parameters in the model was performed. This analysis indicated that the assumption of plastic deforma tion at contact surfaces coupled with a decrease in porosity justified an increase of the tensile strength with consolidation stress. Furthermore, the effect of temperature on the measured flow behavior can be explained as a change in the strength of the material.
A combination of a continuum approach and a particleparticle approach to describe the multiscale nature of the mechanical properties of bulk solids may be beneficial to scientific and engineering applica tions. In this paper, a procedure is proposed to estimate the interparticle forces beginning with the bulk flow properties as measured with standardized techniques. In particular, the relationship between inter particle forces and bulk solid tensile strength is adopted based on the microscale approaches of Rumpf （1970） and Molerus （1975）. The flow properties of fluid cracking catalyst （FCC）, corundum and glass bead powders were all characterized with a modified Schulze ring shear cell capable of operating at tempera tures up to 500 ~C. The powder test conditions were selected such that the van der Waals forces were the most significant particleparticle interactions. The model equations describe two cases, in which either elastic or plastic deformation of the contact points is assumed. The results indicate that the model pro vides the correct order of magnitude for the values of the tensile strength when proper values for the mean curvature radius at the contact points are taken into account. A sensitivity analysis for the main parameters in the model was performed. This analysis indicated that the assumption of plastic deforma tion at contact surfaces coupled with a decrease in porosity justified an increase of the tensile strength with consolidation stress. Furthermore, the effect of temperature on the measured flow behavior can be explained as a change in the strength of the material.
