Investigation of the overall friction coefficient in single-pass scratch test

Single-pass scratch test on bilinear elastic–plastic materials with a conical indenter was simulated using a three-dimensional finite element model. The influence of the interfacial friction coefficient μs and the apical angle α of the indenter on the induced maximum tangential force FT, normal force FN, and the overall friction coefficient μ=FT/FN, were systematically studied. It was found that the induced tangential force is greater than the normal force when the apex is small and vice versa when the apex is large. The tangential force increases with μs, but the normal force decreases with μs. The overall friction coefficient μ was found to increase linearly with μs and tangent of the attack angle of the indenter. The relationship between the adhesion frictional component (μa), the plowing frictional component (μp), and the interfacial friction coefficient μs was analyzed. An analytical model for the overall friction coefficient μ was also developed based on the interaction between the indenter and the specimen and compared to the numerical results. The model was found to yield a good agreement with the finite element simulation results.