SBIR-STTR Award

During Phase I, we will develop the technology for a field use instrument to determine the residual stress, fatigue damage and remaining service life for aging metal structures. The technology will be based on a state-of -the-art wide-angle x-ray detector recently developed at ATMI. The life span estimation will use the measured micro-defect density to compare to a paramedic life span map based on the alloy composition, residual stress and loading conditions. The map will be based on the structural change of diffraction peaks form multiple individual grains during the course of fatigue life. We will demonstrate the feasibility of rapid fatigue damage determination for representative materials by testing representative samples of the three most common crystal cell structures for engineering metals, making the technology applicable for steels, aluminum, nickel and titanium alloys The samples will undergo high circle teensy/compression, bending and corosion loading. Validation of the life span map will be accomplished by interrupting high cycle fatigue tests, predicting remaining life, and subsequently cycling the sample to failure. Successful completion of the Phase I effort will culminate in the production of a field use instrument to be built and delivered at the completion of the Phase II program.

Benefits:
Successful completion of the Phase II program will provide a fast fatigue damage assessment tool, capable of determining the health of metal structure, including airframes, engine, power plants and pipelines, during all stages of service life. With successful completion of the life span map, this technology could be used to extend service life of components past previously arbitrarily set safety limits, making this instrument of great value to many industries with aging equipment.

Phase I results prove the capacity of an XRD multigrain peak broadening technique to measure and map fatigue damage throughout fatigue life of metal alloys. During Phase II, we will develop the technology for a full-scale instrument to determine the fatigue damage and remaining service life for aging metal structures. The technology will be based on state-of-the-art capillary x-ray optics, and an advanced fiber-optic/CCD x-ray detector recently developed at ATMI. The life span estimation will use the measured micro-defect density to compare to a parametric map based on the alloy composition, residual stress and loading conditions. The map will be based on the structural change of diffraction spots from individual grains during the course of fatigue life. The fatigue damage measurement methodology will be determined and validated by testing aluminum and titanium alloys with a variety of cold-working levels and interrupted cyclic loading experiments. Finally, a Fatigue Damage Assessment instrument will be built and delivered upon completion of the program. A successful Phase II program will result in a commercial turnkey system being introduced into the market almost immediately following the Phase II program.

Keywords:
NONDESTRUCTIVE EVALUATION, RESIDUAL STRESS, X-RAY DIFFRACTION, ROCKING CURVE, FATIGUE DAMAGE, LIFE-S