Statistical determination of surface flaw distributions in brittle materials

A computational method is presented for determining the distribution of surface flaws in brittle materials from a series of fracture tests. The number of cracks per unit area with sizes within a range c to c+ Δc can be determined by the solution of a system of simultaneous linear equations. As long as the stress intensity factor for the cracks causing fracture can be calculated then results can be obtained from any loading method; the method therefore assumes that the shape of the cracks causing fracture is known. The only data inputs are the fracture loads themselves. Accurate estimates of the flaw density can only be obtained if proper consideration is given to the variation of the stress intensity factor with the angle between the crack-face normal and the tensile stress. Results are shown for computer simulations of 3-point bend testing.