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Über dieses Buch

Intended for engineers, researchers, and graduate students dealing with materials science, structural design, and nondestructive testing and evaluation, this book represents a continuation of the author's "Fracture Mechanics" (1997). It will appeal to a variety of audiences: The discussion of design codes and procedures will be of use to practicing engineers, particularly in the nuclear, aerospace, and pipeline industries; the extensive bibliography and discussion of recent results will make it a useful reference for academic researchers; and graduate students will find the clear explanations and worked examples useful for learning the field. The book begins with a general treatment of fracture mechanics in terms of material properties and loading and provides up-to-date reviews of the ductile-brittle transition in steels and of methods for analyzing the risk of fracture. It then discusses the dynamics of fracture and creep in homogeneous and isotropic media, including discussions of high-loading-rate characteristics, the behavior of stationary cracks in elastic media under stress, and the propagation of cracks in elastic media. This is followed by an analysis of creep and crack initiation and propagation, describing, for example, the morphology and incubation times of crack initiation and growth and the effects of high temperatures. The book concludes with treatments of cycling deformation and fatigue, creep-fatigue fractures, and crack initiation and propagation. Problems at the end of each chapter serve to reinforce and test the student's knowledge and to extend some of the discussions in the text. Solutions to half of the problems are provided.



1. Structural-Integrity Assessment: The Relevant Fracture-Toughness Evaluation

In this chapter, we describe how fracture strength of materials was evaluated before the Linear Elastic Fracture Mechanics theory appeared fifty years ago, and how this property is now currently evaluated. The fracture behaviors at issue are the three basic ones, i.e. brittle fracture, ductile tearing with or without instability, and failure by brittle fracture after some amount of ductile tearing.
Dominique P. Miannay

2. Structural Integrity Assessment: The Relevant Loading Evaluation

In the design of components such as pressure vessels and piping systems, the different modes of failure to be considered are:
excessive elastic deformation, including elastic instability
excessive plastic deformation
brittle fracture and unstable fracture after ductile tearing
stress rupture and creep deformation
plastic instability-incremental collapse
high-strain low-cycle fatigue
stress corrosion
corrosion fatigue.
Dominique P. Miannay

3. Dynamic Fracture: Elementary Dynamics and Microscopic Fracture

The practical phenomena treated are the start of the extension of a crack, or crack initiation, its propagation with its characteristics, which are the path, straight ahead or along-branching or kinking, the growth rate, and its arrest.
Dominique P. Miannay

4. Dynamic Fracture: The Stationary Crack

We consider in this chapter an isotropie homogeneous continuum in which there is a geometrie discontinuity at rest. The discontinuity is also said to be static or stationary, and is subjected to an increasing load applied rapidly. The case of the discontinuity in motion will be treated in the next chapter. However, some features of this late case are also addressed.
Dominique P. Miannay

5. Dynamic Fracture: The Moving Crack

First the case of a crack moving dynamically in a linearly elastic isotropie body is considered, and the contribution by Mott, who recognized the importance of accounting for the kinetic energy when analyzing dynarnic-crack propagation, is presented. The singular stress-and-strain fields can be fully described by dynamic and cinematic stress-intensity factors. The modification from the stationary crack is explained by the inertia effect. General energetic analysis shows that the strain-energy-release rate, defined as a contour integral that is not in general path-independent, or through aglobai energetic balance, is in the case of an elastic material a path-independent integral, and directly related to the stress intensity factors.
Dominique P. Miannay

6. Creep Fracture: Creep Laws and Elementary Microscopic-Fracture Models

This chapter begins with some background on the theory of creep-flow behavior by dislocation motion, by defect motion, or by the combined effect of both. This elementary knowledge allows for the establishment of laws and rules of creep flow on a macroscopic scale. Then the application to a smooth body introduces the notions of skeletal-point and reference stresses.
Dominique P. Miannay

7. Creep Fracture Mechanics

We consider a homogeneous, isotropic body containing a crack and subjected to external loading. To this crack is associated the usual coordinate system. This body is of a creeping material.
We present in succession the stress-and-strain singularities in the vicinity of the crack, which is at first stationary, and then moving. These singularities are described with the help of various loading parameters. Experimental correlation of initiation of extension and growth with these parameters are presented with their shortcomings. Then various relations between micromechanisms and macromechanics are given in the case of one controlling micromechanism and one creep law, which is the secondary-creep law. Finally, damage-continuum mechanics are presented.
Dominique P. Miannay

8. Fatigue and Creep Fatigue

Fatigue consists of the cycling loading of a structure over time, that is loading and unloading. Thus, the new aspect introduced is the unloading, which suppresses proportional loading at the crack tip and leads to the accumulation of residual stresses after unloading.
When creep phenomena are superimposed to fatigue phenomena at high temperatures, the creep singularity, which can be described by loading parameters C(t), C*, etc., is destroyed and residual stresses are built up during unloading. During subsequent loading, the creep process is resumed, but no satisfactory analytical solutions exist at present. Finite-element computation can be carried out to obtain the stress-and-strain fields around the crack tip, but these computations are time consuming and may be umeliable.
Dominique P. Miannay


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