HyperNex proposes to develop the technology for a portable instrument to determine fatigue damage and remaining service life for aging metal structures. The technology will be based on a state-of-the-art fatigue damage instrument currently being developed at HyperNex, for Al and Ti alloys. This instrument measurement measures the microstructural dislocation density non-destructively, using a very parallel x-ray beam. While proved for Al and Ti alloys, micro-structural problems make the current techniques useless for martensitic steels. HyperNex proposes to study the fatigue progression in martensitic steels, and to examine the applicability of an intensity analysis. HyperNex will then compare these results with the lattice strain throughout the fatigue life cycle. The program will proceed as follows: The martensitic steel samples will undergo loading. Surface and subsurface dislocation density and lattice strain will be measured. Results from the two measurements will be tracked against the fatigue life cycle. Validation of the life span map will be accomplished by interrupting high cycle fatigue tests, predicting remaining life, and subsequently cycling the samples to failure. Finally, upon completion of the Phase II program, a portable Fatigue Damage Assessment instrument usable for martensitic steels, as well as Al and Ti alloys, will be built and delivered
