Volume 30, Issue 3 (May 2002)
Application of a Relativistic Conservation Equation to Crack Initiation
Given the load versus deformation diagram, including the load maximum of a specimen with a known stress intensity factor, the initiation of stable crack growth can be calculated exactly from measurement results by introducing equations analogous to those found in the theory of general relativity. This can be done by means of the two-observer principle. A point on the plastic curve can be equivalently correlated to a given point on the elastic curve. In deriving the equivalence, it can be seen that the different geometrical configurations with respect to the loading direction and the crack plane have to be modified by the introduction of a factor. It was found that this factor is analogous to the Doppler effect (Lorentz transformation.) The agreement of the mathematical procedure using analytical functions with the experimental results (potential-drop technique) has been found to be excellent, using qualified steels. For those materials with significant deformation before crack initiation, the agreement between mathematical procedure and experiment is less good.