Review of NDT Methods Applied to Fatigue Reliability Assessment of Structures by Jamshid Mohammadi: ASCE, Reston, Va.; 2004; ISBN 0-7844-0742-8; 168 pp. Price: $55.00.

This book is a special-topic publication by the Fatigue and Fracture Reliability Committee (FFRC) of the American Society of Civil Engineers–Structural Engineering Institute (ASCE-SEI). The intent of this book is to report the applications of nondestructive testing (NDT) methods for fracture-critical structures with an emphasis on the reliability of fatigue assessment. NDT methods have been an important component of structural inspection, especially for detecting critical damages. With nine papers reporting specific case studies, this book is not intended to be a comprehensive coverage of fatigue reliability or NDT methods, but instead provides “practicing engineers with an introduction of NDT methods with immediate applications to real world problems.”

This book furnishes a general overview of fatigue reliability and probabilistic methods that gives the audience a concise description of the relationship between NDT and the probabilistic analysis of structural fatigue. The goal of this relationship should result in establishing a “fatigue reliability profile of the structure,” and a “cost-effective scheduling of future repair, retrofit or reconstruction activities” (Mohammadi). Although applications of NDT to engineered structures for detecting other damage types are possible, this paper nicely sets the focus of the paper collection, which covers issues about aging aircraft (Braun and Mohammadi) and civil structures (Son and Mohammadi; Mohammadi, Guralnick and Poleppeddi; and Zhao and Halder). Braun and Mohammadi describe fatigue monitoring using a specific assessment methodology and program that includes the permanent placements of sensors (motion transducer, temperature gauge, and strain sensors) and data recorders on a plane. A data quality-assurance program is established to ensure no error in recorded data. Fatigue reliability is determined from fatigue life projection either by using the Miner-Palmgren damage rule or by the crack growth method. The first-order reliability method is then used to establish fatigue reliability versus flight-hour matrix.

For bridge-type structures, Fu and Son et al. review available NDT techniques. Fu differentiates NDT techniques into local and global diagnostic methods, which include liquid penetrant testing, magnetic particle testing, radiographic testing, ultrasonic testing, and acoustic emission testing and visual inspection. Son et al., on the other hand, give more in-depth descriptions of the NDT techniques and differentiates them according to material types: for steel, acoustic emission, the electromagnetic method, portable hardness tests, liquid penetrant inspection, magnetic particle inspection, radiography, the hole-drill method, ultrasonic, dynamic response, and visual inspection; for concrete, chain drag, cover meter, cross-hole sonic logging, half-cell potential test, impact echo, induced polarization, induction field, infrared thermography, radar, rebound hammer, resistivity measurements, slab impulse, sonic echo/impulse response, spectral analysis of surface waves, tomographic imaging, and ultrasonic pulse velocity. Three techniques have been described has new, including fiber-optic Bragg grating sensor, aerial visual inspection, and advanced ground-penetrating radar. Mohammadi, Guralnick, and Poleppeddi describe the use of stress cycle measurements on critical bridge components as an NDT method, which is used to quantify fatigue damage, fatigue life, and bridge life-cycle cost analysis. The significance of bridge overload and increased truck weight has also been addressed. Zhao and Halder discuss the issue of bridge fatigue reliability assessment by using linear elastic fracture mechanics (LEFM) model. The LEFM model is used to establish damage limits as well as the probability of failure. Nondestructive testing inspection is then suggested as an updating technique for bridge-fatigue reliability assessment.

Specific issues of weld inspection have been addressed by Sarkani et al., and Sarkani and Michaelov. Sarkani, Michaelov, and Lutes describe the use of X-ray diffraction and neutron diffraction methods for weld joint residual stress measurements. A stochastic method for fatigue assessment is presented in which predicted fatigue life is defined as a function of the root-mean-square residual stress range, fatigue-life coefficient, and fatigue-strength exponent terms. This paper also discusses the effects of material hardening, elastic-perfectly-plastic behaviors, and stress decay on fatigue-life projection. Sarkani and Michaelov’s paper specifically addresses the issue of numerical simulation of welding residual stresses. The finite-element method is used in this case to help compute residual stresses on a welded joint. Issues addressed include heat transfer, as well as 2D and 3D modeling techniques.

Reliability analysis has been addressed in various books and other literature of particular relevance to manufacturing; whereas in civil engineering practice, reliability has been incorporated into structural designs (LRFD design methodology). Because of the rapidly aging infrastructure, addressing the issue of health monitoring of existing structures is critical. This collection of papers, although it is not decisively authoritative work on the subjects of NDT or fatigue reliability, does present a concise illustration of the applications of NDT for fatigue assessment and reliability. The reliability of fatigue-life prediction can be accurate only when the reliability of the NDT technique used is addressed. It should include determining the probability of detection, false call probabilities, and the accuracy of fatigue fracture-size measurement (Mahadevan and Zhang). The papers also address other practical issues, including proper reliability indexes for target reliability and permissible maintainability (Zhao and Haldar) and cost implications (Mohammadi, Guralnick, and Polepeddi).

The Committee for Forensic Investigation of the Technical Council on Forensic Engineering reviews this publication, since qualitatively evaluating the testing techniques used in forensic studies and quantitatively describing the reliability of interpretation of forensic data are essential. This publication is a timely presentation of the need to address issues of monitoring techniques and the ability to accurately quantify utility and the remaining life span of our nation’s infrastructure.