Session: DA-08-01 Fracture Mechanics in FFS Assessment

Paper Number: 122298

122298 - Expanding the Api 579-1/asme Ffs-1 Stress Intensity Factor Solution for a 360 Degree Surface Cracked Bar (Kbscl)) 

The current library of API 579-1/ASME FFS-1 2021 Fitness-For-Service stress intensity factor solutions found in Annex 9B includes round bars with various surface crack configurations. However, the stress intensity factor solutions are limited to axial membrane and global bending stress inputs for all listed cracked round bar configurations. These stress inputs can be insufficient for some fitness for service applications. Considering this, a long-term effort is underway by the authors and others to expand the stress intensity factor solutions to accommodate generalized stress distributions for all applicable cracked round bar configurations. This paper reports on recent new analysis efforts for the Round Bar, Surface Crack – 360 Degrees, Through-Wall Membrane and Bending Stress (KBSCL) configuration. The objective was to estimate stress intensity factors using parametric, linear elastic finite element models for a generalized stress distribution. A portion of the results were used to calibrate the respective influence coefficient values for a 4^th order polynomial stress field in the radial direction. The study also assessed the use of the API 579-1 three term weight function method, commonly used for arbitrary stress distributions, for the KBSCL crack configuration.  Finally, a comparison of the newly expanded stress intensity factor solution results to previous results by Mangard (2017) was conducted, where the results are within less than one percent.   

Presenting Author: Steven Altstadt Becht

Presenting Author Biography: Steven Altstadt is a Fellow at Becht. Steven’s primary technical focus is the strength and behavior of metal structures and pressurized equipment, with a specialization in fracture and fatigue. He works with clients on new designs, fitness for service of existing assets, and forensic investigations. At Becht he routinely collaborates with NDT inspectors, welding engineers, and metallurgists. He has fifteen years of experience in industry, and a PhD from Purdue University where his primary focus was fracture mechanics. He is a licensed professional engineer in Texas and twenty-five other states.

Authors:

Steven Altstadt Becht
Melanie Sarzynski Becht