SBIR-STTR Award

The Air Force maintains landing gear systems to ensure acceptable structural integrity during their service life.As landing gear systems throughout the Air Force are pushed further and further beyond their original design life, there is a crucial need to develop more precise predictive models addressing the fatigue characteristics of landing gear parts. Fatigue life reduction due to surface finish and microstructure changes caused by exposure to environments and chemicals during processing must be researched and K factors associated with specific material/process combinations must be determined. During Phase I performance, SES will develop K factors, based on a proven statistical methodology. These K factors will then be used to accurately debit strain-life curves which are needed for landing gear fatigue models to ensure the safety of the aircraft fleet as it continues in heavy use far past its originally intended design life. Knowledge of how various processes affect fatigue life will also aid in selecting processes that have the least influence on fatigue.

Air Force landing gear systems are subjected to surface treatment processes (e.g., chrome plating, cadmium plating, anodizing) an indefinite number of times throughout their service life. During these processes, components are exposed to environments and chemicals which affect material surface conditions (e.g., roughness, residual stresses, microstructure) and reduce fatigue life. This reduction in fatigue life has not been quantified in Air Force digital fatigue analysis (DFA) models. In order to increase the accuracy of Air Force DFA models, Phase II efforts will continue the development of k factors which represent the fatigue life debit due to processing (once or multiple times) and refine the methods/tools for determining k factors. Additionally, the Phase I prototype user interface for k factor input to HBM nCode (DFA software used by the Air Force) will be further developed in Phase II. The use of k factors in DFA models will aid in determining the conditions for timely removal of landing gear components from service to reduce risks and associated costs. Risks include both the removal of landing gears before it is necessary as well as potential catastrophic failures if left in service too long. As aircraft are pushed further beyond their original design life