Fatigue Reliability For Aircraft Structure And Health Monitoring For Mechanical Hand On Space Shuttle

This paper consists of study on aircraft structure fatigue reliability and health monitoring of the space shuttle mechanical hand, including calculation of the residual strength of Multiple-Site Damage (MSD) panel on aging aircraft, and health monitoring scheme and verification system of the space shuttle mechanical hand.Multiple-site damage (MSD) phenomenon of aging aircraft and calculation of MSD panel's residual strength have been of great concern since the Aloha accident in 1988. An approach which considers interaction of cracks and stable tearing based on the Swift criterion of Dugdale-type cracks is employed to calculate the residual strength of MSD panel in chapter 2. Stress function alternating iteration method is used to evaluate the plastic zone sizes under the interaction. This model assumes that the material follows elastic-perfectly plastic behaviour. Both fracture toughness and R-curve are considered in the crack propagation process as MSD panel on aging aircraft is under plane stress state, which means that the growth rate of stress intensity factor is greater than the propagation resistance. Consequently, the residual strength of MSD panel will be relatively accurately evaluated by the proposed approach including both interaction of cracks and the effect of stable tearing. Calculation of residual strength is performed for Dugdale model of symmetric collinear MSD panel by proposed approach. Numerical results of 13 different configuration MSD panels of 2024-T3 aluminum alloy are compared with the test results. The agreement between analysis and experiment is shown to be reasonable. Comparison indicates that proposed approach can give a better prediction and will be useful for the investigation of MSD phenomenon on aging aircraft.In chapter 3, three type fault modes of space shuttle mechanical hand are investigated including arm damage, joint block, and joint abrasion failure, based on the function environment. A health monitoring and fault detect primary scheme is given including optimization on monitoring position and quantity, transducer type selection, fault information abstraction and detect methods. In chapter 4, the digital models of space shuttle mechanical hand and three type fault modes are developed. A health monitoring demonstration verification scheme is formed, and a virtual health monitoring demonstration verification system is developed by LabVIEW. The test results show that the method can distinguish the four typical faults of the space shuttle mechanical hand, and the scheme can realize aircraft health monitoring.Finally, summary of the whole thesis and prospect of the related techniques development are presented.