PREDICTION OF VARIATION IN FRACTURE TOUGHNESS FROM SMALL SPECIMEN TESTS.

A model is developed which can relate K//I//c to microscopic parameters. The present work was undertaken to evaluate this model experimentally on several different low alloy steels that had been subjected to extensive prior investigation. The results of this work indicate that at temperatures ranging from minus 196 degree up to 100 degree C, the model is able to predict accurately the temperature dependence of K//I//c and K//I//d from toughness measurements at minus 196 degree C and measurements of the yield strength sigma //y over the temperature range of interest. The model is able to explain why shifts in Charpy transition temperature in going from slow bend to impact correlate well with K//I//c to K//I//d shifts. The model illustrates how a low-temperature measurement of K//I//d coupled with an instrumented Charpy test allows the prediction of K//I//d up to higher temperature.