ON THE BEST FIT CURVE THROUGH CRACK-GROWTH FRACTURE-RESISTANCE DATA

The ESIS recommendations for determining the fracture resistance of du ctile materials make use of an offset power law to evaluate the best f it curve to crack growth fracture resistance data, Evaluation of the o ffset power law requires the use of non-linear regression analysis, al though an iterative linear regression analysis can be used if the data are transformed by taking logarithms. The two analyses are compared w ith a proposed alternative formulation for the offset power law which can be evaluated using an iterative linear regression analysis without the need to transform the data. Confidence limits are evaluated for t he J-DELTAa data of two steels and are shown to depend on the analysis procedures.