THE TROUSERS TEARING TEST WITH DUCTILE METAL SHEETS

A general elastoplastic analysis for the tearing of sheet materials is applied to the well-known "trousers tearing test" which is used to determine R, the specific work of fracture (the fracture toughness), of materials. It is shown that the Cotterell-Mai rigid-plastic analysis for the testpiece [3] has to be modified to take account of differences in local sheet curvature at the tear tip. In consequence, their simple linear plot (back extrapolation of which gives the toughness R) is really a curve with a lower intercept giving the true toughness according to our model. Differences are also revealed at large widths of torn material, where the normalised pulling force at constant R decreases. Experiments over a wide range of tear widths confirm the analysis and also explain why the linear plot of the earlier Cotterell-Mai analysis appeared to be satisfactory.