General Preface The act of switching on an electric light brings with it the almost total expectation that it will work. However, for this simple act to have a successful outcome, a massive and highly integrated network of machines, structures, and systems must swing into operation. This network transcends whole continents, national boundaries, and oceans, and involves structures from the smallest scale, the nanoscales of computer, control and communication systems, to those of the most massive scale, like concrete dams. The fact that the expectation is rarely denied is testimony to the robustness of the total system and to the functionality of the individual components. The electricity generating and supply industry is only one of the many integrated systems of which we have such high expectations. Of the others, the most visible are the water supply industry, the transport industry, the fuel supply industry, the construction industry, the health industry, the textile industry, the food industry, and the most modern, the communications industry; all these rely on machines, control and communication systems, and structures to operate successfully and reliably. Some of these involve engineered products which operate in the domestic field, like textiles, cars, and domestic appliances, while others, like telecommunications and the petrochemical industry, involve services both to the manufacturing industry and to domestic customers. Yet others, like the health industry or the financial services industry, rely on all these industries implicitly or explicitly, to provide the products and services for their successful operation. Successful operation requires that all components of an industry operate to their designed intent. The mechanical integrity required for these components to function as designed is what is meant by the term structural integrity in the context of these volumes, and they are dedicated to the assurance of this structural integrity. There are a number of ways in which components can fail mechanically. They may simply be overloaded, or they may wear out. They may be exposed to a corrosive environment outside of that for which they were designed. They may suffer extremes of loads in an unanticipated incident, or even in an earthquake. They may also be badly designed, or manufactured, or be operated in an abusive way, or they may be fabricated from an inappropriate or defective material. However, one of the most frequent causes of failure is the presence of crack-like defects. These defects are particularly significant because they can lead to structural failure well within the original design envelope of the structure, and the failure can be highly disruptive and without warning. The scientific and engineering disciplines involved in assuring structural integrity encompass the physical, chemical, mathematical, materials and engineering sciences, and in extremis involve also the biological sciences and nanotechnology. This is not simply because of the range of industries involved, but because of the interdisciplinary nature of the issues that can contribute to structural failure. It is axiomatic that any analysis of structural integrity must be based upon detail that can only be obtained by rigorous application of each of these disciplines in turn, whereas the overall assessment must take a more global view. This view must not only integrate the separate outcomes of the individual disciplines, but also must involve a vision of the whole picture which transcends these disciplines, and which may also involve judgments on cost and safety implications that are not immediately obvious. Indeed, it is extremely important to obtain the correct balance between costs and the technical implications, as the price of making a wrong decision is almost always excessive. In addition, although any single failure event may seem to be relatively inconsequential in isolation, more often than not it can be the forerunner of a chain of events, which results in truly catastrophic consequences. vii
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This treatise, called Comprehensive Structural Integrity, comprises 10 separate volumes, each addressing different aspects of structural integrity assessment. It begins with an introductory volume, Structural Integrity Assessment—Examples and Case Studies. This volume attempts to put structural integrity into perspective. It contains 19 chapters. The first chapter introduces the whole treatise. It is aimed at providing an out-of-the-frame reference to structural integrity issues, demonstrating their ubiquitous nature, the costs to the community, the implications of structural failure on whole industries, and the fact that failures do not occur out of the blue, but arise from a technical error, a lack of technical foresight, or from a management failure. Structural integrity is not something that simply happens because of good design and construction. It requires proper assessment and active management throughout all phases of the life of a structure. This volume contains a further 18 chapters, each one addressing issues associated with a specific industry or a specific technology. They draw from case studies, in some presenting these in detail, and in others presenting only a broad outline of the main components. These chapters are not meant to provide detailed scientific studies, but are to give examples of historic and current issues, with sufficient technical detail to provide a coherent account of the causes and effects, and to give insights into how case studies are performed, or how they are made use of, both commercially and technically. They are meant to demonstrate the need to view the whole picture, and that too close a focus on one part of it risks serious consequences. They raise most of the technical issues addressed in the remaining volumes, but reveal some of the complexities of real-life engineering structures and operation. The importance of a sub-optimal combination of features appears in many of these chapters as does the significance of event chains, not only in causing the failure of a component but also in contributing to the magnitude of the consequences. There are elements of bad practices identified, solutions given, and lessons to learn. Volumes 2–9 address the details of the various technical theories, mechanisms, and other components required to ensure structural integrity of engineering structures of all types, large and small. Volumes 2–7 tend to be discipline oriented, and attempt to provide a full description of the methods used. As far as possible, each of these is self-contained, although some cross-fertilization is unavoidable. Volumes 8 and 9 are special volumes, addressing in turn nanostructures and structures engineered for biological purposes. These have been separated from other volumes, as they tend to address specialist aspects associated with their own technologies. Nevertheless, the fundamental sciences and technologies on which they are based are contained in the most part within Volumes 2–7. Additional fundamental issues specific to the nanoscale are addressed in Volume 8. The final volume, Volume 10, contains the subject index. Volume 2, Fundamental Theories and Mechanisms of Failure, describes the fundamental theories and mechanisms of failure in materials and structures. The first five chapters describe the general theories, with only a minimum of material-specific details, which form the foundations of the stress analysis and design of all structures. The remaining 10 chapters are devoted to specific materials and, on the one hand, describe the influence of the microstructure of the material on its performance, and, on the other, how this influence is accounted for in the general theories. The first chapter of this volume gives an overview of the existing strength theories, including elasticity and plasticity theories. It also covers theoretical aspects of limit analysis, shakedown, progressive damage accumulation, creep, and multiaxial fatigue. The second chapter describes theories of elastic and inelastic buckling and of large strains. The next chapter describes in detail linear elastic (LEFM) and elastic–plastic fracture mechanics (EPFM). It introduces the important concepts of fracture toughness and toughness for linear elastic and elastic–plastic materials with limited ductility. For materials that exhibit extensive plasticity, it is shown that the crack resistance description may require two or even three parameters. Fracture mechanics is one of the most valuable tools for examining the safety of cracked structures, for developing effective remedial measures, if required, and for determining their remnant useful life. All structures are designed and manufactured in such a way as to avoid, as far as possible, cracklike defects. Such defects can, however, form during the service of the structure. The formation of defects is an evolutionary process resulting from the accumulation of damage as a result of working environment, e.g., creep and fatigue. This damage is usually distributed in the structure initially and only tends to localize into discrete cracks just before failure. The distributed damage can be handled in a manner similar to that of plasticity in the framework of continuum damage mechanics. This framework is elucidated in another chapter. This is followed by a chapter describing the theory of fracture under dynamic and/or impact loads, highlighting the considerable differences in the performance of structures under high strain rates from their performance under quasi-static and cyclic loads.
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The remaining chapters of this volume are devoted to the mechanisms of failure in different engineering materials, ranging from concrete and steel to composites, such as metal–matrix composites, ceramic composites, functionally graded materials, and ferroelectrics. Polymer composites are dealt with elsewhere. Each of these chapters highlights the role of microstructure of the material in its observed behavior under various working conditions. In many instances, the observed behavior has been captured through appropriate changes to the general theories described in the first five chapters. Volume 3 covers Numerical and Computational Methods. Accurate stress analysis of real structures containing diffuse or localized damage is a very difficult task even in the elastic state. The task is further complicated if the material is in plastic state and if the structural geometry is complex. This task cannot be accomplished analytically in all but the simplest structures, yet it has to be performed in order to assess the integrity of the structure. This volume addresses the computational methods for an accurate stress analysis of real structures. Thus, computational methods based on finite and boundary elements are described. Whilst the boundary element method is limited to elastic structures, methods based on the finite elements are useful for both LEFM and EPFM under static and dynamic loads, as well as the calculation of the residual stresses induced by welding. These computational methods have been described. For structures containing diffuse damage (microcracks), as opposed to discrete macrocracks, computational methods based on continuum damage mechanics have been introduced. Such methods are particularly useful for stress analysis of structures made from composites and concrete. Alternatively, methods based on mathematical programming are necessary for limit and shakedown analysis, while those based on neural networks and filtering approaches are appropriate for the inverse identification of material and system parameters from their observed responses. This volume also introduces the latest developments in finite element techniques which avoid remeshing when analyzing one or several growing cracks in a structure. Volume 4, Cyclic Loading and Fatigue, provides a comprehensive, multidisciplinary description of the broad topic of deformation and failure due to cyclic fatigue in engineering materials and structures from all relevant viewpoints, including mechanics, modeling, application design and life prediction, microscopic mechanisms, and material class. Following a general introduction, the first two chapters focus on the general engineering analysis and accompanying mechanistic aspects of low-cycle-fatigue failures (including cyclic deformation and crack initiation) and high-cycle-fatigue failures (including ultra-long-life behavior—also called gigacycle fatigue). The treatment here includes a description of the mechanisms of cyclic deformation, crack initiation and growth (principally for ductile, i.e., metallic materials), as well as the relevant mechanics associated with fatigue analysis. This is followed by chapters devoted to the principal ways in which design against fatigue is achieved, namely, total life or S/N approaches (as described in the chapter on local strain approach) and the damage-tolerant approach (as described in the chapter on fatigue crack propagation). Subsequent chapters are centered on specific topics, specifically modeling (analytical and numerical), multiaxial fatigue, variable-amplitude effects, and fretting/contact fatigue. In these chapters the topics are presented in terms of both total life and crack propagation methodologies, again with a balanced mechanics/mechanistic perspective. These are followed by a set of chapters describing the fatigue behavior of specific materials, namely, brittle materials (ceramics and intermetallics), polymeric materials and composites, and finally four shorter chapters reviewing the importance of fatigue: (a) in combination with high temperatures (creep/fatigue) and active environments (corrosion fatigue), and (b) in small-volume structures. These last topics are treated in more complete fashion in Volumes 5, 6, and 8, respectively. Of interest here is how the fatigue behavior of ceramics and polymeric materials is, in many ways, mechanistically quite different from that in metals, yet can still be described within the same framework. Specifically, by considering fatigue crack growth as a mutual consequence of intrinsic damage mechanisms ahead of a crack tip, which promote cracking, opposed by extrinsic crack-tip shielding mechanisms behind the tip, which impede it, the distinction between the fatigue behavior of ductile versus brittle materials can be described simply in terms of the relative importance of each class of mechanism— intrinsic mechanisms dominating in ductile materials, whereas extrinsic mechanisms dominate in brittle materials. The volume ends with a chapter on the application of the concepts to actual fatigue failures in service through a description of several case studies. Volume 5, Creep and High-temperature Failure, addresses the topic of high-temperature performance of materials and structures, which requires consideration of new deformation and damage modes. High-temperature operation involves time-dependent deformation known as creep,
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changes in strength, crack initiation and growth resistance and fracture properties due to the high temperatures, enhanced oxidation kinetics, and time- and stress-dependent changes in microstructure that influence the properties as a function of time. The volume opens with a chapter presenting the mechanisms of creep deformation and rupture and physical models that allow us to predict these phenomena. Most structures that operate at high temperatures are also subjected to cyclic loading and quite frequently to transient and steady-state temperature gradients. This leads to conditions of creepfatigue interaction and/or thermal–mechanical fatigue. Invariably, this involves crack initiation and growth and this is treated in the next two chapters, one addressing mainly how cracks are initiated under these conditions, the other mainly on crack growth under these conditions. The two chapters that follow describe the time-dependent fracture mechanics approach for predicting crack growth under creep conditions. The first of the two chapters focuses on basic time-dependent fracture mechanics concepts while the second focuses on experimental methods for characterizing the creep crack growth behavior. Finally, the volume is completed by chapters addressing the prediction of creep-fatigue crack growth and the assessment of remnant life in both ferritic materials and non-ferritic materials. Volume 6, Environmentally Assisted Failure, addresses fracture where an environmental component is involved. Environment can affect structural integrity in a number of ways: general corrosion, pitting corrosion, crevice corrosion, stress corrosion, and corrosion fatigue being the most obvious. The volume opens with an introductory chapter explaining the general nature of environmentally assisted failure, the types of environments involved, and a brief description of how these may compromise structural integrity and how they interact. Although the chemical effect of the environment is often the same under both steady loading and cyclic loading, the mechanical effects may be different. Accordingly, this is treated separately by chapters addressing these mechanisms as if they were discrete. Thus, there are chapters included on stress corrosion cracking and environmentally assisted fatigue, and the latter is separated further into mechanisms in liquid environments and in gaseous ones. Environmental degradation in nonmetallic structures is as important as in metallic ones, and chapters are included to address such degradation in reinforced concrete structures, and in polymers. Hydrogen is often treated as a special case in environmentally assisted cracking, as it can influence structural integrity in one of two ways. Hydrides may form in some metals, which can induce a crack to form under the influence of a tensile stress. More commonly, hydrogen dissolves in the metal, which is embrittled particularly where hydrogen can accumulate, such as in the plastic zone at the tip of a crack or defect. Thus, two chapters are included treating hydrogen effects, one where hydride formation affects cracking, and another on hydrogen cracking in nonhydride forming alloys. Oxygen can also have an effect, of course, especially in higher-temperature applications, and a chapter is included that addresses the interaction of creep, fatigue, and oxidation. Finally, one of the most damaging of environmental effects arises from neutron irradiation. This is different from other forms of environmental degradation, in that it simply causes embrittlement, and is neither crack forming nor does it contribute to a general reduction of the load bearing area. But the amount of embrittlement is potentially large, and in the presence of crack-like defects that may arise due to other mechanisms, it can have severe consequences on structural integrity. The final chapter gives a detailed account of the mechanisms of irradiation embrittlement, its measurement, and prediction. Volume 7, Practical Failure Assessment Methods, describes global codes for failure assessment of structures containing crack-like defects from the underlying philosophies, to their implementation in fitness-for-purpose standards. Standards based on failure assessment diagrams and on estimation of crack driving force parameters are presented and the equivalence of these two approaches is discussed. Essential inputs to both approaches are fracture toughness data and a description of the crack-like defects. Methods for measuring and interpreting the required fracture toughness data in all fracture regimes are presented. Guidance on characterizing the size and shape of a defect is given. Practical issues such as the treatment of thermal and residual stresses, warm prestressing, and dynamic problems are addressed. In addition to fracture assessment methods, the volume also covers special approaches such as the local approach to fracture, leak-before-break arguments for pressurized components, and probabilistic fracture mechanics. Although the volume largely addresses metallic structures, fracture assessment methods for concrete and ceramics are covered. Also included is a chapter presenting experiments to demonstrate the behavior and
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performance of large-scale structures under a variety of loading systems and the validation of the assessment techniques. The volume concludes with a discussion of the features and the logic that can be applied in making the final decision. Volume 8, Interfacial and Nanoscale Fracture, considers the structural integrity issues specific to interfacial and nanoscale fracture and their potential implications for new and emerging technologies. The first three chapters develop interfacial fracture theories under static and dynamic loads. The next five chapters are devoted to reliability issues in electronic packaging, electronic materials, microelectronic circuits, and MEMS. Unique techniques for experimentation at micro- and nanoscales are described in the next two chapters. Failure at nanoscale and reliability of nanostructures are addressed in the remaining chapters. The exposition is comprehensive, without duplication of material from Volumes 2–4. Thus, only those theoretical aspects that are specific to nanoscale are covered in this volume. Likewise, numerical techniques for continuum or quasi-continuum analysis described in Volume 3 are not considered, but computational techniques based on a combination of atomistic and continuum analysis are included. Volume 9, Bioengineering, addresses the very special structural integrity issues related to dental, orthopedic, and cardiovascular implants engineered for body implantation. This volume is organized differently from the others, with chapters focusing on the special materials used for medical devices, and on some specific types of them. It addresses fundamental issues of fatigue fracture, contact mechanics, wear, and biocompatibility, which is an environmental issue different from those associated with more conventional engineering plants. The human body is considered to be one of the most aggressive environments. The environments here cannot be controlled, of course, so the material performance in the environment is the only means of management available. This is emphasized in the opening chapter, where fatigue and wear issues are addressed using, among other things, heart valves and hip prosthesis as examples. Methods of fatigue evaluation are presented, including predictive tools for in vivo assessment and environmental stability. The mechanics of hard and soft tissues are then addressed, which includes their cell structure–property relationships and the methods of evaluation. Knowledge of soft and hard tissue enables a proper basis for the application of biomaterials for specific implants. This is followed by four chapters on biomaterials, covering in turn metals, polymers, ceramics, and composites. These chapters typically cover the relevant applications, their mechanical properties, biocompatibility, fracture behavior, and their microstructure–property relationships, and include where possible some case studies of failures and expected future advances. Special chapters are included on heart valves, joint prosthesis and dental bridges, and also on rehabilitation bioengineering, which addresses artificial limbs, materials used, muscle forces and stresses due to walking and running, etc., and the standard testing of prosthesis. This 10-volume Comprehensive Structural Integrity set provides a first point of entry to the literature for both the engineer and the researcher across a wide range of disciplines. In all there are 130 chapters with contributions from over 190 distinguished experts from 21 different countries. It takes the form of a definitive research and reference tool that links the various technical disciplines which comprise the whole spectrum of structural integrity. The volumes will be of use to students, researchers, and practicing engineers alike. I. Milne Structural Integrity Management, Matlock, UK B. Karihaloo University of Wales, Cardiff, UK R. O. Ritchie University of California, Berkeley, USA
