Measurement of stress distribution for rotating shaft using thermography

A rotating shaft is designed by comparing calculated stress for expected load with material strength. Because unexpected force is often applied to the shaft in an actual machine, the generated stress can be larger than the calculated one. Strain gauge method is generally applied rotating shafts by using a slip ring or telemetry. However measurement accuracy is decreased by electrical noise generated from motors in the machine. In the paper, the method of two-dimensional thermoelastic stress measurement was developed to determine fluctuating distribution of stress in the rotating shaft. Bending stress in the rotating shaft could be accurately identified by using inverse analysis with images taken from multiple positions of a thermographic camera. Validity and efficiency of the method were confirmed on the basis of numerical and the experimental results and the accuracy of the stress was also found to depend on reference temperature in the measurement.