Surface cracks three dimensions

Three attempts are knovm to define, and to account for, a work of rupture which is independent of the sample dimensions and thus may represent a property of the material studied. The most common mode of rupturing a solid involves the growth of a crack. In many instances it is possible, more or less convincingly, to separate the work / (ergs or joules) necessary for this gro rth from the v/ork done on the simultaneous gross deformation of the test sample (and the instrument employed). Usually it is found that this U is proportional to the area A of the new crack surfaces, so that fg/sec or kg/sec ) remains constant... 

---