New J and COD estimates for thin-walled pipes with axial through-wall cracks and high strain hardening exponents

• Published in: Theoretical and applied fracture mechanics 2017-08, Vol.90, p.75-84
• Main Authors: Surh, Han-Bum, Jang, Youn-Young, Kim, Se-Chang, Shim, Do-Jun, Huh, Nam-Su
• Format: Article
• Language: English
• Subjects: Approximation; Austenitic stainless steels; Axial through-wall crack; Crack opening displacement; Cracks; Enhanced reference stress method; Exponents; Finite element method; Fracture mechanics; Influence functions; Internal pressure; J-integral; Optimized reference load; Pipes; Plastic influence functions; Stainless steel; Strain hardening; Studies; Thin-walled pipes; Three dimensional analysis
• ISSN: 0167-8442; 1872-7638
• DOI: 10.1016/j.tafmec.2017.03.001

•New h1 and h2 of GE/EPRI method are proposed for thin-walled pipe with an axial TWC.•For the new h1 and h2, high strain hardening exponents are considered for thin-walled pipe.•New optimized reference load is given for reference stress based J and COD estimates.•The proposed J and COD estimates are validated against 3-D finite element results. In this study, the approximate estimates of elastic-plastic J and COD for thin-walled pipes with axial through-wall cracks (TWCs) and high strain hardening exponents under internal pressure are developed based on the GE/EPRI and enhanced reference stress (ERS) methods. For the estimations based on the GE/EPRI method, the proposed tabulated plastic influence functions for fully plastic J and COD are derived from three-dimensional finite element (FE) analyses. On the basis of these plastic influence functions, an optimized reference load (which plays an important role in the ERS method) is newly suggested. Finally, the present elastic-plastic J and COD estimations are verified by comparing the predicted results with the FE results using actual tensile behavior of SA312 type 304 SAW stainless steel. The estimations based on both GE/EPRI and ERS methods provide better approximations for thin-walled pipes with axial TWC and high strain hardening exponent, than do the existing estimations. The importance of the elastic-plastic fracture mechanics assessment, using the present solutions for thin-walled pipe with axial TWC and high strain hardening exponent, are also discussed.