The wear process of particulate magnetic tapes by rotary heads in video tape recorders was investigated. It was found that the plastic flow of the polymer binder in the top layer on the surface asperities (low swellings) of a magnetic layer of a tape caused by head rubbing forms the smoothed surface. The increase in the real contact area on these surfaces asperities by smoothing creates a frictional force increase up to the shear strength of the asperities. When the frictional force exceeds that strength, the asperities are fractured by the shear stress. The wear debris from many fractured asperities gathers into large lumps and retransfers onto the tape surface. The increased frictional force between a rotating head and retransferred lumps of wear debris with an increasing number of head traces causes a larger shear fracture inside a magnetic layer under the retransferred lumps. Wear debris from the scars made by large shear fracture, combined with retransferred lumps, scratches the tape surface as a prow.
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