Fracture Phenomena in Metal Plates: Theoretical and Experimental Analysis of Crack Propagation in Metallic Alloys

By comparing data obtained from tensile tests at room temperature on plates containing cracks of various lengths, it has been found that alloys of metal can be classified into three groups. Each of these groups differs distinctly with respect to the effect of cracks on strength reduction, crack propagation and mode of failure. Theory is presented on (i) the mode of failure, (ii) effect of finite width on critical stress and (iii) size effect. Resulting formulae are expressed in simple parameters: nominal stress, critical crack length and material constant. For the two most common material groups, criteria of fast fracture is deter‐mined. In the case of the group characterized, on one extreme, by large strength reduction and high velocity of crack propagation, fracture still remaining shear type, application of Griffith theory of fracture is discussed and circumstances are described leading to this type of instability. Experimental results presented in support of theory given herein, include tests on plates of varying width and of alloys of magnesium, aluminium, titanium and iron.