Local stress and strain during crack growth by steady state creep

Experimental methods are used to measure the distribution of plastic strain ahead of a crack propagating under steady state creep conditions. Using these strains the local strain-rates are known, and from these the steady state stress distribution is deduced assuming power law behavior. The resulting information indicates that the exponential term of the stress distribution should be modified. It is shown that, for low values of the exponent m in the power law, creep crack growth should correlate with the elastic stress intensity factor, whereas at large m values a better correlation is expected with the net stress.