Fatigue is a cumulative, path-dependent phenomenon: the order and severity of load cycles matter, not just their count. A personal twin's advantage over generic maintenance intervals is that it simulates the actual load history one vehicle experienced, rather than assuming a standardized duty cycle no real driver follows exactly.
The multi-body solver's continuous stress output is first reduced with the rainflow-counting algorithm into discrete stress-range cycles, mirroring the technique used in physical strain-gauge fatigue testing. Each cycle's amplitude is looked up against the component's S-N curve to yield a small damage increment, which is summed cycle by cycle under Miner's rule into a running total that the twin persists across the vehicle's entire operating history rather than resetting at each service interval.
Alerting the owner at exactly 100% consumed fatigue life is too late for a safety-relevant component and too early is meaningless noise. The twin pipeline sets a component-specific alert threshold—typically 70 to 80% for steering and suspension parts—calibrated against the historical variance between simulated damage fraction and observed real-world failures across an anonymized population of similarly calibrated twins, balancing early-enough warning against needless replacement of parts with genuine remaining life.