Measuring tensile, shear and torsional strength of solid bridges between particles in the millimeter regime

In this paper we present a novel experimental setup created to measure the strength of solid bridges between double-particle systems in the millimeter range. Beside the tensile strength, shear and torsional strength can be measured as well. Urea particles are used which are known for creating solid bridges under well defined climatic conditions. The measurements indicate that unlike to isotropic materials the bridge between two particles has higher shear than tensile strength. Moreover, the strengthening of the bridges with storage time is very inhomogeneous, suggesting the use of wide distribution for bridge strength instead of mean values in modelling.