Prediction of fatigue crack initiation under biaxial loading

J.V Sahadi,R.J.H Paynter,D Nowell

doi:10.3221/igf-esis.41.15

Abstract

This investigation revisits biaxial fatigue experiments carried out with the nickel-based superalloy termed Waspaloy. Recently, yield criteria extended to multiaxial fatigue and stress based approaches were analysed and their performance to correlate the biaxial test data was evaluated. It was concluded that despite their reliable results, the parameters did not properly represent the physical behaviour of the material. In this context, an extension of this study was executed considering the strain based critical plane approaches proposed by Fatemi-Socie (FS) and Smith- Watson-Topper (SWT). The first parameter presented overly conservative predictions with large scatter of results. In contrast, more accurate predictions were obtained with the SWT parameter.

Highlights

Advances in material testing equipment and techniques during the past 40 years enabled the development of more realistic multiaxial fatigue tests by applying loads representative of service life, at different temperature settings, test frequencies and load phase shift
Among the most used techniques, cruciform specimens and thin-walled tubular specimens have been broadly used for fatigue testing under biaxial stress states
For cruciform specimens the assessment of biaxial compression region is commonly challenging due to testing machine limitations

Summary

Introduction

Advances in material testing equipment and techniques during the past 40 years enabled the development of more realistic multiaxial fatigue tests by applying loads representative of service life, at different temperature settings (room, low or elevated temperatures), test frequencies and load phase shift. The present paper presents further developments on the investigation of multiaxial fatigue criteria and their predictions for the biaxial test results presented at [8] In the case of plane stress and no shear, a uniaxial stress with equivalent strain energy to a biaxial stress state is formulated as:

Results

Conclusion