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Abstract: Residual stresses are a common and often undesired result of material processing, introduced through non-linear deformation and/or phase transformation of material under mechanical or thermo-mechanical loading. These macro stresses alter mechanical properties and the intrinsic fatigue crack growth characteristics of the material. Residual stress artifacts can introduce inconsistencies and significant errors when the true material behavior is needed for material development and optimization and for structural component design. The effects of quenching residual stresses on fatigue crack propagation behavior of various materials were investigated. In parallel, residual stresses similar in magnitude and distribution with the quenching residual stresses were generated using mechanical processes to decouple the effects of residual stresses from microstructural effects. Mechanical residual stress distributions predicted by 3D elastic-plastic finite element analysis showed good agreement with the stresses measured on fatigue crack growth testing specimens using fracture mechanics approaches. Crack propagation characteristics in fields with low and high residual stresses were studied using optical and scanning electron microscopy, and the effects of residual stress on crack path behavior were assessed. An original residual stress analytical correction to fatigue crack growth data was developed, compared to existing corrective methodologies, and validated using residual stress free data. Overall, the work provides tools to understand, control, and correct the effects of processing residual stresses on fatigue crack growth for accurate fatigue critical design and life predictions.
Annotation Contains 24 papers from the November, 1998 symposium of the same name, sponsored by the ASTM Committee E8 on Fatigue and Fracture, and presented by Newman and Piascik (both of the NASA Langley Research Center). The papers focus on such areas as fatigue-crack growth threshold mechanisms, loading and specimen-type effects, analyses of fatigue-crack-growth-threshold behavior, and applications of threshold concepts and endurance limits to aerospace and structural materials. Annotation copyrighted by Book News, Inc., Portland, OR.
Experimental results on the effects of compressive and tensile residual stresses on Mode I fatigue crack growth are briefly reviewed. Prediction methods that attempt to account for the observed effects are compared. Current limitations of the methods and their relative advantages and drawbacks for use in design analysis are discussed. The possible role of residual stress re-equilibration on growth behavior, caused by crack extension itself, is also discussed.
The purpose of this Handbook is to provide a review of the knowledge and experiences in the field of fatigue fracture mechanics. It is well-known that engineering structures can fail due to cyclic loading. For instance, a cyclically time-varying loading reduces the structure strength and can provoke a fatigue failure consisting of three stages: (a) crack initiation (b) crack propagation and (c) catastrophic failure. Since last century many scientists have tried to understand the reasons for the above-mentioned failures and how to prevent them. This Handbook contains valuable contributions from leading experts within the international scientific community and covers many of the important problems associated with the fatigue phenomena in civil, mechanical and nuclear engineering.
Fatigue of structures and materials covers a wide scope of different topics. The purpose of the present book is to explain these topics, to indicate how they can be analyzed, and how this can contribute to the designing of fatigue resistant structures and to prevent structural fatigue problems in service. Chapter 1 gives a general survey of the topic with brief comments on the signi?cance of the aspects involved. This serves as a kind of a program for the following chapters. The central issues in this book are predictions of fatigue properties and designing against fatigue. These objectives cannot be realized without a physical and mechanical understanding of all relevant conditions. In Chapter 2 the book starts with basic concepts of what happens in the material of a structure under cyclic loads. It illustrates the large number of variables which can affect fatigue properties and it provides the essential background knowledge for subsequent chapters. Different subjects are presented in the following main parts: • Basic chapters on fatigue properties and predictions (Chapters 2–8) • Load spectra and fatigue under variable-amplitude loading (Chapters 9–11) • Fatigue tests and scatter (Chapters 12 and 13) • Special fatigue conditions (Chapters 14–17) • Fatigue of joints and structures (Chapters 18–20) • Fiber-metal laminates (Chapter 21) Each chapter presents a discussion of a speci?c subject.
An investigation was conducted into fatigue crack growth in samples of as-received and autofrettaged, high-strength, low-alloy steel tubing containing residual stresses. Compact tension and C-shaped and ring specimens were used to measure properties in the axial and radial directions. Internally and externally flawed ring specimens were employed to propagate cracks through the original residual stress field. Experiments were performed for load ratios ranging between -0.5 and 0.8. Fatigue crack growth rates were substantially reduced by compressive residual stresses. The data were corrected for residual stress effects using the superposition principle. An effective stress intensity factor range, ?Keff, was defined that incorporates the residual stress intensity factor, Kres, and the applied ?K range. Using this approach, the correlation with the characteristics for no residual stress was very good. In addition, it was shown that fatigue crack growth rate characteristics measured with C-specimens can significantly misrepresent the actual behavior of the material and tubing under investigation if the remaining residual stress field is not taken into consideration.
Fatigue of Materials covers a broad spectrum of topics that represent the truly diverse nature of the subject that has grown to become a key area of scientific and applied research. Constituting an international forum for the materials industry, the book provides the perspectives of operators, engineers, and researchers regarding all aspects of current and emerging technologies for materials.