Theory 15/Structural Health Monitoring
Life Depends on the Spectrum Ratio
The claim
Remaining fatigue life is set by the ratio of measured stress range to design stress range raised to the fatigue exponent, so modest exceedances consume life disproportionately.
01Mechanism
Crack growth scales with stress range to a power; a small ratio above one removes a large fraction of life.
02Predictions
- P1Life should fall sharply above a ratio of one.
- P2Average stress should mispredict.
03Refutation
Life tracking average stress would remove the exponent.