Preface. About the authors. Contents. A brief introduction to fatigue and fracture mechanics. Conventional fatigue (high and low cycle fatigue). Background. Cyclic or fluctuating load. Fatigue spectrum. The S-N diagram. Constant-life diagrams. Linear cumulative damage. Crack initiation and stable crack growth. Low cycle fatigue and the strain-controlled approach. The conventional or engineering stress-strain curve. The natural or true stress-strain curve and hysteresis loop. Cyclic stress-strain curve. Strain-life prediction models. Universal slope method. References. Linear elastic fracture mechanics (LEFM). Energy balance approach (the Griffith theory of fracture). The stress intensity factor approach. Fracture Toughness. Residual strength of a cracked structure. Plasticity at the crack tip. Plastic zone shape based on the Von Mises's yield criterion. Surface or part through cracks. References. Fatigue crack growth. Introduction to fatigue crack growth. Crack growth rate empirical descriptions. Crack closure phenomenon. Variable amplitude stress and the retardation phenomenon. Cycle by cycle fatigue crack growth analysis. Structural integrity Analysis of a bolted joint under cyclic loading. References. Fracture control program and non-destructive inspection. Introduction. Fracture control plan. Non-destructive inspection (NDI) for safe-life assessment. References. Fracture mechanics of ductile metals (FMDM) theory and the ASTM fracture toughness test. Introduction. Fracture mechanics of ductile metals (FMDM). Determination of terms. Octahedral shear stress theory (plane stress conditions). Octahedral shear stress theory (plane strain conditions). applied stress, and half crack length, relationship. Mixed mode fracture and thickness parameters. The stress-strain curve. Verification of FMDM results with the experimental data. Brief description of ASTM fracture toughness determination. Appendixes. Subject index.
In the preliminary stage of designing new structural hardware that must perform a given mission in a fluctuating load environment, there are several factors the designers should consider. Trade studies for different design configurations should be performed and, based on strength and weight considerations, among others, an optimum configuration selected. The selected design must be able to withstand the environment in question without failure. Therefore, a comprehen sive structural analysis that consists of static, dynamic, fatigue, and fracture is necessary to ensure the integrity of the structure. During the past few decades, fracture mechanics has become a necessary discipline for the solution of many structural problems. These problems include the prevention of failures resulting from preexisting cracks in the parent material, welds or that develop under cyclic loading environment during the life of the structure. The importance of fatigue and fracture in nuclear, pressure vessel, aircraft, and aerospace structural hardware cannot be overemphasized where safety is of utmost concern. This book is written for the designer and strength analyst, as well as for the material and process engineer who is concerned with the integrity of the structural hardware under load-varying environments in which fatigue and frac ture must be given special attention. The book is a result of years of both acade mic and industrial experiences that the principal author and co-authors have accumulated through their work with aircraft and aerospace structures.
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