Innovative Approaches to Flaw-Tolerant Design and Certification of Airframe Components

The development of a procedural and computational framework for improved prediction of damage accumulation caused by cyclic loading in metallic airframe components is proposed. This framework will be based on the idea that models formulated for the prediction of crack nucleation, i.e., for the purpose of supporting flaw tolerance analysis, and models formulated for the prediction of crack growth, i.e., for the purpose of supporting damage tolerance analysis, are similar in the following sense: In both cases the physical events of interest; crack nucleation and crack growth, are highly nonlinear processes that occur on length scales less than about 0.5 mm for metals used in airframes and are controlled by stress and strain fields computable from mathematical models based on small strain and small deformation theory. Therefore the driving force for damage accumulation can be correlated with functionals that depend on models based on small strain theory. The problem is to identify the functionals that reliably correlate predicted and observed damage accumulation events. The proposed procedural and computational framework will be designed to support this effort.