PSI - Issue 75

Sixin Liu et al. / Procedia Structural Integrity 75 (2025) 200–204 Sixin Liu/ Structural Integrity Procedia (2025)

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but in a proportional and calibratable fashion. For instance, finite element modelling and experimental validation showed that when the aluminium substrate endured approximately 60,000 cycles, the sensor consistently fractured at ~30,000 cycles, thereby signalling the mid-life point of the host component. By altering notch geometry or thickness, the sensor can be tuned to indicate other fractions of fatigue life (e.g., 25% or 75%). This calibrated life-fraction mechanism establishes a direct and practical relationship between sensor behaviour and host structure degradation. The visible fracture of the sensor is therefore not a simple reflection of elapsed cycle count but a scaled physical manifestation of cumulative fatigue damage in the monitored component. In this way, the sensor provides operators with an intuitive, passive, and cost-effective tool for estimating remaining life within To predict fatigue crack initiation and propagation behaviour under cyclic tensile loading, a detailed finite element model of the sensor-substrate assembly was developed using ANSYS Workbench. The sensor model consisted of a polypropylene strip (1 mm thickness, 5 cm length, 2 cm width), with symmetric V-notches applied on both lateral edges to induce stress concentration. The geometry was discretised using a tetrahedral mesh with a total of 9,152 elements and 16,059 nodes, achieving a mesh quality factor of 0.24, which was deemed sufficient for fatigue life estimation and crack evolution analysis. Boundary conditions replicated the experimental configuration: one end of the sensor was fully constrained, while the opposite end was subjected to a uniaxial tensile displacement. A sinusoidal loading profile was applied to simulate the actual cyclic loading scenario, characterised by a stress R=0.5. Mean stress effects were incorporated using the Goodman correction, enabling a more realistic estimation of fatigue damage under non-zero mean stress conditions [5]. structural health monitoring frameworks. 3. Finite Element Simulation and Results

Figure 3.1: Directional deformation contour

The simulation output, shown in Figure 3.1, illustrates the X-directional deformation field, revealing a symmetric elongation pattern consistent with uniaxial tensile loading. Notably, the maximum deformation occurred at the notched region, where local strain concentration is expected due to geometric discontinuity. This finding underscores the effectiveness of the notch design in localising deformation and fatigue damage.