A Web-Based Uncertainty Plug-In (WUPI) for Fatigue Life Prediction Based on NDE Data and Fracture Mechanics Analysis

Abstract

Over the last thirty years, much research has been done on the development and application of failure event databases, NDE databases, and material property databases for pressure vessels and piping, as reported in two recent symposia: (1) ASME 2007 PVP Symposium (in honor of the late Dr. Spencer Bush), San Antonio, Texas, on “Engineering Safety, Applied Mechanics, and Nondestructive Evaluation (NDE).” (2) ASME 2008 PVP Symposium, Chicago, Illinois, on “Failure Prevention via Robust Design and Continuous NDE Monitoring.” The two symposia concluded that those three types of databases, if properly documented and maintained on a worldwide basis, could hold the key to the continued safe and reliable operation of numerous aging nuclear power or petrochemical processing plants. During the 2008 symposium, four uncertainty categories associated with causing uncertainty in fatigue life estimates were identified, namely, (1) Uncertainty-1 in failure event databases, (2) Uncertainty-2 in NDE databases, (3) Uncertainty-3 in material property databases, and (4) Uncertainty-M in crack-growth and damage modeling. In this paper, which is one of a series of four to address all those four uncertainty categories, we address Uncertainty-2 in NDE databases by developing a Web-based Uncertainty Plug-In (WUPI), which automates the uncertainty estimation algorithms of flaw sizing, fracture toughness, and crack growth vs. ΔK data such that NDE data from the field can be acted on by office engineers with a reduced feedback time for maintenance decision making.

A Risk-Uncertainty Formula Accounting for Uncertainties of Failure Probability and Consequence in a Nuclear Powerplant

“…In 2009, Fong, Marcal, Hedden, Chao, and Lam [65] responded to the suggestion in the Khaleel, et al report [64] by formulating an uncertainty equation for the life prediction model of an aging bridge. As shown in Fig.…”

“…In Table 2, Fong, et al [65] gave a more complete formulation by including two additional databases involving (4) loadings and constraints, and (5) physical-chemical composition and dimensional variability. A conceptual representation of the relationship between the result uncertainty of the remaining life estimates and a collection of six source uncertainties is given in Fig.…”

“…To illustrate the usefulness of the fracture-mechanicsbased failure probability uncertainty equation concept as introduced in Fig. 6 [65], we show its application to structural health monitoring in two practical cases, namely, (Case 1): An innovative inspection interval design based on "direct " NDE measurements of crack initiation and growth, as explained in Figures 7 [67] and 8 [65].…”

“…For a given pair of initial and final crack lengths, a given load range, S , and three known material property constants, C , F , and m , Dowling [67, pp. 519-524] and Fong, et al [65,Section IV] have shown that the number of cycles to failure, Nif , is given by:…”

“…Foremost among the databases considered i n Ref. [65] are: The Failure Event Database-1 (Uncertainty-1, or, e 1 ), the Flaw Detection, Location & Sizing or NDE Database-2 (Uncertainty-2, or, e 2 ), the Material Property Database-3 (Uncertainty-3, or, e 3 ), the Deterministic or Probabilistic Damage Model (Uncertainty-M, or, e M ), and the Remaining Life Estimates (Uncertainty-4, e 4 Table 1 of Ref. [65]).…”