Failure analysis of microflawed ductile matrix materials

It is shown in this study that linear elastic fracture mechanics techniques do not provide a consistent geometry-independent means of predicting failure in microflawed ductile matrix materials. Several aspects of microflawed material behavior during fracture testing suggest that considerable plastic behavior occurs on the microscale in microflawed materials. It is suggested that limit analysis techniques applied first on the microscale then extended to the macroscale may provide a consistent means of failure prediction. Three-dimensional limit surfaces are developed for several types of microflawed materials. Comparison of these limit criteria with currently available theories and experimental data on microflawed materials in the absence of macroscale notches shows that the proposed theory is valid for smooth material failure predictions. Subsequent extension of the microscale limit surfaces to continuum macroscale structural analysis shows that the proposed theory will provide an upper bound failure prediction. It is also shown that linear elastic fracture mechanics methods will provide a lower bound failure prediction.Advanced Research Projects Agency, ARPA Order No. 2169, 74/0