Elastic-plastic fracture mechanics method for poor penetration crack in welded piping branch junction

摘要

This paper provides two types of engineering J estimation equations for weldedrnpiping branch junctions with poor penetration crack under internal pressure. The firstrntype is the so-called GE/EPRI type J estimation equation based on Ramberg -Osgoodrn(R-O) materials. Based on detailed 3-D FE results using deformation plasticity, plasticrninfluence functions for fully plastic J components are tabulated for practical ranges ofrnthe inner radius of brace to the inner radius of chord ratio, the thickness of brace to thernthickness of chord, the thickness of chord to the inner radius of chord ratio, the crackrndepth to the thickness of chord ratio, the strain hardening index for the R-O material,rnand the location along the poor penetration crack front. Based on tabulated plasticrninfluence functions, the GE/EPRI-type J estimation equation along the crack front isrnproposed. For more general application, the effective remote stress method based onrnGE/EPRI-type solutions is provided. This method provides a simpler equation for J,rnwhich could be used for any stress-strain relationship material, including Ramborg-rnOsgood(R-O) material and non-R-O materials under monotonic increasing loading.rnThe proposed effective remote stress based J estimation equation is compared withrnelastic-plastic 3-D FE results using actual stress–strain data for a Type 304 strain lessrnsteel. Good agreement between the FE results and the proposed reference stress basedrnJ estimation provides confidence in the use of the proposed method for elastic-plasticrnfracture mechanics of pressurized welded piping branch junction.