Experimental study on micro-mechanical model for two different bonded granules under complex stress conditions

The micro-mechanical properties of idealized bonded granules are experimentally studied. The bonded granules are idealized by two aluminum rods glued together. Two types of bonded granules different from the bond thickness between rods are investigated, namely thin bonded rods and thick bonded rods. The mechanical tests are performed on these two bonded rods. The experimental results show that the bond thickness and the normal force have a significant effect on the mechanical properties of the bonded granules. The tensile strength and ductility both increase with the increase of the bond thickness. The compression curve exhibits strain hardening in the thin bonded rods but strain softening in the thick bonded rods. The peak shear/rotational strength increases with the increase of the normal force in the thin bonded rods, while they increase with the normal force at first, and then decrease in the thick bonded rods. Moreover, the strength envelope in the normal-torsion-shear space is an elliptic paraboloid in the thin bonded rods and a teardrop in the thick bonded rods.