Correction for particle surface topography in inter-particle tangential shearing tests

Inter-particle behaviour at the microscale is most fundamental in multi-scale modelling of granular materials. A few experimental studies have been performed to obtain inter-particle behaviour on different types of granular materials; however, the resolution of forces is not yet accurately worked out due to the unknown plane of contact. This article discusses the estimation of orientation of contact plane at each point of sliding profile and resolution of contact forces and displacements to obtain coefficient of friction in tangential sliding. The tangent along sliding direction was obtained using the locus of top and base particles during sliding; and tangent along out of plane direction was obtained using force equilibrium. These two tangents are then used to calculate the contact normal. The three forces and three incremental displacements obtained from experimental data are resolved along true tangential and normal directions. The tangential displacement, tangential force, and normal force are used to calculate the coefficient of friction.