Figure 9
The graph is titled “Illustrative Physics-Informed Fit to Degradation Data”. The horizontal axis is labeled “Operational time (normalized)”, ranging from 0.0 to 1.0 with an interval of 0.2, and the vertical axis is labeled “Normalized degradation state”, ranging from 0.0 to 1.0 with an interval of 0.2. Two datasets are shown and identified in a legend at the upper left: circular markers labeled “Experimental data (normalized)” and a solid line labeled “Physics-informed digital twin (fit)”. The experimental data points increase over time from near (0.0, 0.0) to (1.0, 0.9), showing a generally increasing trend with some scatter. The blue fitted curve starts at (0.0, 0.0), rises smoothly, and closely follows the trend of the data points, capturing the nonlinear increase and gradual saturation. The curve approaches a value near 0.9 by time 1.0. Note: All numerical values are approximated.Illustrative physics-informed fit to normalized degradation data. Comparison between representative experimentally reported normalized degradation data (symbols) and the fitted physics-informed digital twin response (solid line). The fit is obtained by calibrating a single degradation rate parameter. Despite experimental noise and sparse sampling, the model reproduces the global degradation envelope while enforcing monotonicity, boundedness, and asymptotic saturation (NRMSE ≈ 3–6%)