Tensile strength calculations in simulated cohesive granular assemblies

An intrinsic and essential feature of powders is their ability to resist an applied tensile pressure. This macroscopic resistance has its origin in the attraction due to the van der Waals force existing between individual grains. After the analysis using the Discrete Elements Method, we report some preliminary results obtained from applying progressive leaps of tensile pressure on different granular assemblies, until the breakage of the structure occurs. A continuous and slow isotropic rate stress is also imposed to investigate the breakage. We focus our attention on three related issues: (i) the dependence between the maximum tensile stress resisted and the initial degree of bulk compactness, (ii) the effect of two different procedures to induce the structural stretching until the breakage, and (iii) the adequacy of simplified models commonly used to predict the typical intergranular force in non-cohesive granular materials (Rumpf, 1958). In that respect, since the very loosely cohesive simulated packings present a numerically computable porous distribution, we suggest some conceptual modifications in the existing model: the aim is to find an appropriate theoretical framework within which all those predictions of the interparticle adhesive forces fit, taking into account both the fabrication process and the interparticle parameters. This preliminary study of tensile strength suggests a transition from ductile to fragile behavior as density increases, as well as an important role of the initial connectivity of the contact network