Estimation of stress in specimens loaded with ultrasonic fatigue machines

•The largest deviation on frequency is caused by the uncertainty on Young's modulus.•Frequency deviations from machining are lower than that induced from Young's modulus.•The uncertainty in stress estimation using a laser coupled with FEM is 3.2%.•The uncertainty in stress estimation using strain gauges is 3%.•The uncertainty in stress estimation using XRD is 10%.•These uncertainties underline a good agreement in stress amplitude estimation.•The stress amplitude was found to vary linearly with the displacement amplitude.•The material response at the macroscopic scale can be considered as purely elastic.•XRD provides an experimental 1D profile of stress amplitude along the sample length.