An improved strength-measurement technique for brittle materials

An improved apparatus for determining the fracture strength of brittle materials by a hydraulic bursting technique is described. The new design greatly reduces the number of specimens which fail at their edge and reduces the scatter in the results. To complement this, a more detailed theory is developed to analyse results. An investigation of the strength of silicon nitride as a function of the impact velocity of a water jet illustrates the use of the apparatus. A method for converting fracture stress data to equivalent flaw size data is given which allows a more physically meaningful and useful presentation of results.