US Patent 10379020 Vibration fatigue testing

A method to determine a fatigue limit for a material. Form a test component including the material. Identify a resonant frequency of the component and an excitation frequency which causes the component to vibrate. Measure a response parameter of the component when excited at the excitation frequency. Test the component to determine its fatigue limit by sub-steps to: apply an excitation force to the component at the excitation frequency to cause vibration of the component; alter the applied excitation force at constant excitation frequency to maintain the response parameter constant; measure at least one of an input parameter and an output parameter; iterate the sub-steps to alter and measure until the first order, second order, or first and second order derivatives of the input parameter and/or output parameter exhibit a discontinuity. Repeat the steps for a different excitation frequency. The fatigue limit for the material includes all the identified discontinuities.