Failure Experiments on Pipes With Local Wall Thinning Subjected to Multi-Axial Loads

Piping lines in nuclear power plants may experience multi-axial loads including tensile force, bending, and torsion moments during operation. There is a lack of guidance for failure evaluation of locally wall-thinned pipes under the multi-axial loads including tor-sion moment. The ASME B& PV Code Section XI Working Group is currently developing fully plastic failure evaluation procedures for pressurized piping items containing local wall thinning subjected to multi-axial loads. A failure estimation method for locally wall-thinned pipes subjected to multi-axial loads including torsion moment has been proposed through numerical analyses. In this study, in order to investigate the failure behavior of the pipes with local wall thinning subjected to multi-axial loads including the torsion, failure experiments were performed on 20mm diameter carbon steel pipes with a local wall thinning. Based on the experimental results, the proposed failure estimation method is confirmed to be applicable to pipes with local wall thinning.