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

Paper Number: 122388

122388 - Investigation of the Api 579-1/asme Ffs-1 Kptc Stress Intensity Factor for Bending Stress 

The API 579-1/ASME FFS-1 2021 Fitness-For-Service stress intensity factor solution for a plate with a through-wall center crack (KPTC) subject to bending stress was investigated. Finite element models of through-thickness center cracked plates subjected to bending stress fields were created and used to estimate stress intensity factors (K) along the crack fronts, which were then used to establish influence coefficient values. For fitness for service applications it is a common practice to extrapolate K along the crack front to obtain an effective K at the surface. The method chosen for extrapolation can have a minor impact on the results. The method of extrapolation used for this assessment is consistent with other through-thickness crack solutions in API-579. The new influence coefficient values presented herein are recommended for fitness for service assessments that involve KPTC subjected to bending stress. Most of the FE results were cross checked against results generated using the dual boundary element method, which showed excellent agreement. The comparison of the newly calculated stress intensity factors to the existing API 579-1 KPTC values showed modest differences for some cases and substantial differences for others. The largest differences were associated with high plate width-to-thickness ratios. The new influence coefficients were also compared to values published by Marie et al (2007). Good agreement was found for almost all cases, but there were some notable discrepancies for high plate width-to-thickness ratios. Some cautionary notes are provided to help delineate the range of applicability for fitness for service assessments.

Presenting Author: Scott Bouse Wiss, Janney, Elstner Associates, Inc.

Presenting Author Biography: Scott Bouse joined WJE in 2018 with diverse experience in finite element, fracture mechanic failure, and fitness for service analyses, as well as instrumentation and monitoring in laboratory and field applications. Mr. Bouse is highly proficient in API 579 (Fitness for Service), including Level 3 analysis, Calculations per ASME B31, ASME VIII (Div. 1,2), TEMA, PCC-1, PCC-2, API 530 (Heater Tubes), API 620 (Low-Pressure Tanks), and API 650 (Atmospheric Tanks). In the laboratory and in the field, he has applied high-temperature strain gages, standard resistive-foil gages, thermocouples, and other sensors to gather data needed to both feed analysis inputs and validate results.

Prior to joining WJE, Mr. Bouse spent ten years at Stress Engineering Services, where he performed detailed engineering calculations on a wide variety of equipment types, including vessel-to-structure interactions and damage assessments. He has authored and presented papers and presentations on assessment and analysis topics to the refining and petrochemical industries.

Authors:

Steven Altstadt Becht
Sharon Mellings CM BEASY
Scott Bouse Wiss, Janney, Elstner Associates, Inc.
Ryan Ryan Butchers CM BEASY