Damage detection and fatigue life estimation under random loads: A new structural health monitoring methodology in the frequency domain

This paper presents a methodology for structural health monitoring of fatigue cracks under stationary random loads. The methodology is composed of two parts: an empirical correlation to monitor the evolution of damage indices and a numerical scheme for fatigue life estimation. The damage indices are based on the variation of the vibrational response of the structure due to crack propagation. Two damage metrics are studied, and the methodology is verified for a cantilever beam subjected to random base excitation. The case study validates the effectiveness of the methodology and shows that both metrics have the potential for damage detection. For the numerical estimation of the fatigue life, the proposed framework uses the probability density function of the stress, which is obtained from frequency-domain methods, and an equivalent stress approach based on the Walker's equation for fatigue crack growth. Excellent agreement is found between the predicted fatigue life and the experimental values.