Creep Tensile Instability Solutions in Design Applications

“Creep Tensile Instability” W. J. O’Donnell and J. S. Porowski, presented at the Fourth International Conference on Pressure Vessel Technology, London, England, Proceedings, May 1980.

Keywords: membrane load stresses; pressurized spherical vessels; pressurized cylindrical vessels; elevated temperature; cyclic loading; triaxiality effects; thermal stresses; allowable strains

Creep tensile instability solutions are obtained herein for most cases encountered in design applications. These include: (1) membrane load stresses of arbitrary biaxiality (2) pressurized spherical vessels, and (3) pressurized cylindrical vessels and piping with combined axial loads. Solutions are obtained for both the effective (Mises) strains and the maximum tensile strains at instability. The results show that neither Triaxiality Factors nor factors based on plastic tensile instability solutions can be used to convert creep rupture ductility to safe allowable design values for components operating in the creep regime. The present solutions can be used to obtain allowable strains for design applications using available uniaxial creep rupture ductility data.

President, Bill, Sr. serves as a Contributing Member of the ASME (BPV III) Working Group on Fatigue Strength, and has co-authored numerous papers on creep, fatigue and fracture. 

O’Donnell Consulting performs engineering design and analysis in Elevated Temperature Applications.

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