Tool sharpness as a factor in machining tests to determine toughness

An orthogonal cutting test has recently been proposed for determining Gc in polymers. This is of particular value when applied to tough and/or ductile polymers, when the conditions of LEFM are often violated. However, concerns exist about the effects of tool sharpness and the contribution of ploughing to Gc. Here, tools with varying sharpness have been employed and the results critically analysed. It is shown that cutting with sharp tools does give Gc, and that when cutting with blunter tools the ploughing contribution can be rationalised by comparing the tool tip radius with the height of the fracture process zone.