Fatigue life assessment and analysis based on weak perturbation effects

Fatigue damage in materials is a critical factor affecting the safe operation of nuclear power components. Magnetic response is highly sensitive to material degradation processes and serves as an important means for assessing material integrity. Based on theoretical analysis, this paper establishes a coupling model between low-frequency weak-perturbation inductance signals and fatigue damage. The application potential of this signal in fatigue life assessment is explored using point-by-point measurement. Simulation and experimental results demonstrate that changes in inductance signals effectively characterise the evolution of fatigue damage, maintain good consistency across different detection methods, and provide reliable early warning for fatigue failure. Microstructural analysis validated the effectiveness of voids in fatigue damage theory and revealed multiple microscopic mechanisms – including the phase transformation from metastable austenite to magnetic martensite and the pinning of magnetic domains by dislocations – that collectively drive nonlinear magnetic response changes during damage evolution.