Utilizing Force-State Mapping for Detecting Fatigue Damage Precursors in Aerospace Applications

The Force-State-Mapping (FSM) method is utilized to identify and monitor precursors to fatigue damage in aerospace alloy structures exposed to vibratory loads. The method is created originally to detect nonlinearity in a dynamical system via a direct non-parametric identification. In this paper, FSM is constructed at various stages of the fatigue-life using the Masri-Caughey method. The experimental results show that FSM is a sensitive indicator for monitoring the health state of a structure prior to the development of cracks. The required restoring force due to fatiguing is obtained as a function of the vibration cycles and input loads. FSM appears to be a promising method in connecting the global structural dynamic response to the evolution in the micro-behavior of the materials due to fatigue degradation. For aerospace applications, the objective of this effort is to estimate the required restoring force using current structural health monitoring systems and supply this value to the control laws of an aircraft. Thus, an aircraft can prevent or slow crack development by autonomously readjusting its maneuver based on its health-state.