ASME STP-PT-097-2023Stress Intensification Factor, K-Factor, and Sustained Stress Index Development—Phase II
standard by ASME International, 08/16/2023
In support of ASME B31J and B31H standards, physical testing for stress intensification factors (SIFs), flexibility factors (k‐Factors), and sustained stress indices (SSIs) can be used to confirm differences between the Markl and Hinnant curves in the low‐cycle ranges and finite element predictions of fatigue, stiffness, collapse and burst.
Improvement in analytical capability since the 1950s (when Markl developed the basic rules in the B31 piping codes used today) has improved the ability to numerically predict stress states. Unfortunately, not all piping components are well defined geometrically or dimensionally in ASME standard documents.
Large D/T (ratio of mean header diameter to header nominal thickness) and d/D (ratio of mean branch diameter to mean header diameter) failures involve nonlinear characteristics that may not be well represented by elastic analyses. In these cases, verification by test is considered essential to verify the predicted values and the method of analysis considered.
This publication documents the results of phase II of work undertaken to investigate deficiencies in the existing test data sets identified during the data collection effort from ST-LLC Publication STP-PT-073.