The indentation of materials by wedges

Abstract

It is shown that the mechanism and extent of the deformation of materials by wedges depends upon the angle of the indenter, and on the elasticity of the indented material as well as on its yield point. The theory for a plastic rigid solid applies only when the angle of the wedge is acute and the indented materials are of low elasticity. At more acute angles, the mechanism of deformation has been shown by Mulhearn to become one of radial compression. It is shown here that this mode of deformation is also favoured when more elastic materials are used. It is also shown that the indentation pressure approximates to that for the expansion of a semicylindrical cavity in an infinite elastic medium with definite yield point and takes the form $P/Y = m \ln (E/Y)+C$ where m and C are constants, E is the Young modulus, Y the yield point in simple extension and P the flow pressure. The value of C depends upon the angle of the wedge. The result is analogous to that obtained by Marsh using a 136$^\circ$ pyramidal indenter, but elastic effects are more important in wedge indentation than when indenting with a pyramid. For blunt wedges and elastic materials, elastic effects predominate in importance; the process can then be regarded as that of the indentation of an ideally elastic solid by a rigid wedge. The pressure distribution on the indentation has been determined. It is shown that elastic theory satisfactorily predicts this distribution of pressure, as well as its mean value. For the indentation of highly elastic materials by acute angled wedges, the elastic and plastic deformations become comparable and the mode of deformation is very complex.