Vibratory Stress Relief—An Investigation of the Underlying Processes

Abstract

The use of vibration to reduce residual stress levels in fabrications is potentially an attractive alternative to thermal annealing. The application of the process has hitherto been limited by the lack of coherent theory of operation. In this study, residual stresses were introduced into a low-alloy steel EN3b by rolling. It was shown that prolonged low-amplitude vibration at 100 Hz induced a stress relaxation of as much as 40 per cent, where the original level was close to yield. A model has been developed to explain the diverse effects resulting from low-amplitude vibration; the model involves the motion of dislocations under the influence of the combined residual and external cyclic stress fields. This model, which has been validated by detailed X-ray line profile analysis and elasticity measurements, is an extension to the currently available explanation for VSR (vibratory stress relief). The standard model, which assumed the need to exceed the local yield stress, only comes into operation at the higher levels of applied stress amplitude. The development of accurate and validated methods for the application of VSR may now be contemplated.