Blunt or Sharp Indenters: A Size Transition Analysis

The first event occurring in a glass or a ceramic material beneath a blunt punch is conical crack initiation and beneath a sharp punch is plastic deformation. These behaviors are here analyzed as punch size transition. The transition radius of the punch is determined by using the method first proposed by Kendall (1978), based on both fracture (Griffith) criterion and yield (Von Mises) criterion analyses. The effect of the punch geometry or of the punch sliding is computed. The transition radius appears then as a quantitative brittleness indicator, which also provides a mechanical definition for the sharpness or the bluntness of the punch.

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