Session: MF-06-02 Materials and Technologies for Nuclear Power Plants II

Paper Number: 60449

Start Time: Tuesday, July 13, 2021, 08:00 PM

60449 - Secondary Stress Weighting Factor and Plastic Reduction Factor for Circumferential Surface Cracked Pipe and Elbow Tests at Elevated Temperature and Internal Pressure 

Current flaw evaluation procedures in piping system use elastic design analysis for secondary stresses (load-controlled), but fracture analysis uses elastic-plastic loading behavior. The actual rotations or displacements of the pipe system that occur due to the non-linear fracture behavior are much higher than the elastically calculated rotations/displacements.  These actual non-linear rotations provide margins on the elastically calculated rotation values that come from uncracked pipe-design analysis.  To account for the inconsistency, a Secondary Stress Weighting Factor (SSWF) was established which is the ratio of elastic-plastic moment to the elastic moment calculated through an elastic stress analysis.  As long as the remote uncracked pipe stresses are below yield, the SSWF is 1.0, and if the uncracked pipe plastic stresses are above the yield stress, the SSWF reaches a limit which is called the Plastic Reduction Factor (PRF).  A methodology to determine SSWF and PRF was developed in an earlier investigation for outer diameter surface cracked pipe tests at room temperature (RT). In this study, a PRF factor was developed for internal diameter (ID) surface-cracked pipes and elbows at an elevated temperature from recently conducted experiments. This methodology can be used on any pipe size, material, and pipe system geometry.  To validate this methodology further, SSWF and PRF values were determined for ID surface-cracked pipes and elbows of two different materials at elevated temperature of 550°F with internal pressure of 2,250 psi.  The PRF values at RT (70°F) and 550°F were compared. The two materials used in this study were TP304 stainless steel and Alloy600.

Presenting Author: Sushma Pothana Engineering Mechanics Corportion of Columbus

Authors:

Sushma Pothana Engineering Mechanics Corportion of Columbus
Gery Wilkowski Engineering Mechanics Corporation of Columbus
Suresh Kalyanam Engineering Mechanics Corporation of Columbus
Yunior Hioe Engineering Mechanics Corporation of Columbus
Bud F Brust Engineering Mechanics Corporation of Columbus
Fabian Orth Engineering Mechanics Corporation of Columbus
Prabhat Krishnaswamy Engineering Mechanics Corporation of Columbus
Gary Hattery Engineering Mechanics Corporation of Columbus
Steve Burger Naval Nuclear Laboratory
Steven Gilbert Naval Nuclear Laboratory