Wear anisotropy of MnZn ferrite part III: A wear model

Abstract

The wear against magnetic tape of MnZn ferrite has been shown to be highly anisotropic (Part I), with a dependence on orientation which resembles the sensitivity to first plastic deformation under a sliding contact (Part II). The load at which the first slip steps become visible under a sliding sphere is shown here to be directly related to the resolved shear stress in the active {100} 〈011〉 and {111} 〈01̄1〉 slip systems. Moreover, the angular dependence of the wear of ferrite against soft pigment tapes correlates with that of the maximum resolved shear stress in the {100} 〈01̄1〉 slip systems only. For pigments with higher hardnesses, activation of more slip systems reduces the wear anisotropy. A model is proposed for mild wear of crystalline ceramic materials, in which the surface roughness induced by slip is worn away by passing asperities of the counterface.