RESIDUAL STRESSES ON INCONEL 718 TURBINE SHAFT SAMPLES AFTER TURNING

Abstract

Results of X-ray residual stress measurements on Inconel 718 turbine shaft samples are here proposed. The paper presents part of the EU STREP project VERDI activity, where the aim was to supply those who numerically simulate machining process with an experimental database of proved reliability. Measurements were planned on a set of samples machined with different levels of cutting speed and feed rate. Due attention was given to the assessment of the uncertainty of experimental results. A database of surface residual stress values and depth profiles is presented with the estimated uncertainty both on stress and depth values. The stress proved to be always tensile at the surface and compressive below the surface. Higher cutting speed and feed rates produce higher surface tensile stresses but the trends are different for the two measurement directions.

Keywords:

• Inconel 718
• residual stresses
• turbine shaft
• turning
• X-ray

ACKNOWLEDGMENTS

The authors are grateful to EU for financing this work in the FP6 STREP VERDI project. Moreover the authors express their thanks to Mr. Marco Cherubini of Avio Propulsione Aerospazio S.p.a.—Aeroengines division—Industrial Technologies Dept. for his collaborative support in the technological planning and manufacturing of the turned samples.