ROUGH-SURFACE CONTACT ANALYSIS AND ITS RELATION TO PLASTIC-DEFORMATION AT THE HEAD-DISK INTERFACE

Ni-P coated Al-Mg (Ni-P) and glass-ceramic (GC) substrates for magneti c recording are measured by an atomic force microscope (AFM) using dif ferent scan sizes and sampling resolution. AFM measurements of the Ni- P and GC surfaces at smaller sampling intervals reveal finer details. The GC surface contains more high frequency details than the Ni-P surf ace. The correlation length beta, a spatial parameter, is used in add ition to the rms roughness R(q) to characterize the surfaces. Contact analysis using a three-dimensional elastic-plastic rough surface conta ct model shows that the asperity pressure of the GC surface increases more rapidly than the Ni-P surface as the sampling interval decreases. For both surfaces, asperity contact starts from plastic deformation, the scale of which depends on different surface topographical structur es. The GC surface is shown to have higher asperity pressure because i t has higher frequency structures. The high frequency structure will f acilitate plastic deformation, and it can help explain previously publ ished results why the disk with Ni-P substrate has better durability t han the disk with GC substrate in different environments. (C) 1996 Ame rican Institute of Physics.