AN INSTABILITY ANALYSIS FOR A CRACK GROWTH SITUATION BASED ON THE COMMON FORMAT

摘要

The Common Format Equation (CFE) approach, together with a crack growth law that relates crack extension to plastic displacement, are used to develop a relation between load, P, and crack extension, Δa, for a situation where there is stable crack growth. The P-Δa relation is then differentiated in order to obtain the condition for which dP = 0, i.e., the critical value of crack length for which maximum load is attained. Substitution of the critical crack length on the CFE with crack growth incorporated, and in the crack growth law, will yield the values of maximum load and critical plastic displacement, respectively. The overall P-υ curve with crack growth is obtained by combining the Common and Concise Formats, the latter giving the value of the elastic component of the displacement due to crack growth. Some examples of C(T) specimen P-υ-a data are analysed to show the potential of the method.