In Situ Prediction of Metal Fatigue Life Using Frequency Change

A reliable technique for rapid prediction of the remaining useful life (RUL) of components experiencing fatigue degradation is introduced. The approach is based on measuring the temperature signature of a component upon rapidly changing its operating frequency for a short period of time. The temperature variations caused by alterations in plastic work rate are correlated to the loading history. The efficacy of the approach is investigated by conducting a series of axial fatigue tests on stainless steel 316 specimens. The material characterization involves subjecting the material to a constant amplitude fatigue load at 4 Hz and 12 Hz frequencies. The operating frequency is temporarily adjusted to the characterization frequencies for a brief duration. During this period, the change in the slope of temperature rise is recorded. Subsequently, the operation frequency is reverted to its original state, and the remaining useful life is predicted based on the recorded data. The model provides predictions for operation frequencies of 6 Hz, 8 Hz, and 12 Hz, and notably, the error of predictions is consistently under 12% for all cases. The method allows the operator to reliably estimate the remaining usefulness for field applications without interrupting the operation.