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In this study, the failure process of the cement mortar-clay rock (C–C) binary was analyzed using a composite hybrid FEM/DEM model. First, an improved pressure-related cohesive element was used to simulate the mechanical properties of the binary interface. Then, a numerical model of the cement anchorage body in clay rocks was constructed based on the new interfacial cohesive element and FDEM model of clay rock. Finally, the debonding and slip failure process of the anchorage was analyzed by the numerical model and a corresponding physical model test. The results show that: except for the debonding of the interface, the fracture of weaker side material (clay rock) is also a potential failure mode of the C–C binary. The clay rocks have a larger internal friction angle but smaller cohesion, so the failure mode changes from the shear failure of clay rock to the debonding of the interface when the normal pressure is up to 200 kPa. The failure of the anchor may also cause by the generation of the shear failure zone in soft rock instead of the interface debonding. Therefore, the shear strength of the rock should also be considered in the calculation of anchorage resistance. [ABSTRACT FROM AUTHOR]

Magnetic multilayer stacks incorporating several layers of graphene have been predicted to produce very high magnetoresistance and high conductivity, a combination of properties that would be useful in magnetic sensors and future spin-based data storage and processing technologies such as MRAM. To realize the theoretically modeled heterostructures and probe their properties, a clean, high-quality graphene-ferromagnet interface, such as one that results from CVD of graphene directly on ferromagnetic films, is required. However, past works using Ni and Co films for CVD of graphene employ the ferromagnetic film as a sacrificial layer to be dissolved after graphene growth and ignore changes to its morphology and magnetic properties. Here we investigated the effect of graphene CVD growth conditions on the properties of Co, Ni, Co 90 Fe 10 and Ni 80 Fe 20 ferromagnetic films. The magnetic films were grown by dc magnetron sputtering with different growth conditions onto c-Al 2 O 3 , Si/AlN and MgO substrates. The crystalline orientation, surface morphology/roughness and magnetic properties of the films were measured using X-ray diffraction, atomic force microscopy and vibrating sample magnetometry, respectively. Cobalt films grown at 500 °C were found to be hcp and heteroepitaxial on c-Al 2 O 3 . CoFe, Ni, and NiFe films on c-Al 2 O 3 were found to be fcc and to be (111) textured but with grains having in-plane rotation differing by 60°. The CoFe and NiFe films on c-Al 2 O 3 retained their small coercivity and high remanence while the pure Co and Ni films exhibited much smaller remanence after graphene growth, making them unsuitable for magnetic memory technologies. Films on Si/AlN were found to have the same rotational domains as those on sapphire c-Al 2 O 3 . The NiFe films on (111) MgO were found to be mostly single domain. [ABSTRACT FROM AUTHOR]

Discrete element simulations are performed to better understand the breakage of marble spheres upon oblique impact. The influence of the contact friction coefficient and impact angle on the impact-induced breakage is considered. A modelling method for oblique impact is proposed. Detailed parameter calibration and verification of the modelling method were performed. The oblique simulations show that the laboratory breakage behaviour of marble spheres upon normal and oblique impact is well matched through the proposed modelling method. Tensile and shear breakage patterns are observed in laboratory tests and simulations and are significantly influenced by the contact friction coefficient and impact angle. The shear component of the impact velocity determines the breakage at a low impact angle and high contact friction coefficient, while the normal component dominates the breakage at a high impact angle or low contact friction coefficient. The damage ratio, contact force and fragment characteristics are also analysed. Two constants, i.e., the critical shear contact force and critical normal contact force, are obtained. Finally, a comprehensive breakage criterion for brittle particles under oblique impact is proposed. The breakage patterns of brittle particles can easily be determined through the proposed breakage criterion. [ABSTRACT FROM AUTHOR]