Fracture Kinetics Of Crack Growth

Over the past few years, we have made numerous presentations, delivered several series of lectures, and participated in many discussions on the processes of time-dependent crack growth. We felt that the understanding of these processes had reached a degree of maturity: the basic physical principles were established and their application to engineering practice was now feasible. We concluded that the best way to organize this knowledge was to write it up in a single, coherent system. Martinus Nijhoff kindly encouraged us and generously offered their collaboration. Hence, this book. The physical process of time-dependent subcritical crack growth is rigorously defined by statistical mechanics. If well presented, the principles can be readily understood by practitioners of fracture research and design engineers. We present the physical processes of crack growth in terms of atomic interactions that assume only a working knowledge of the standard engineering materials course contents. From this, we develop a framework that is valid for any type of material, be it metallic, polymeric, ceramic, glass or mineral - indeed, any solid. We also assume an elementary exposure to fracture mechanics. An appendix is provided that outlines those aspects of fracture mechanics that are needed for an introduction to fracture kinetics analyses; it also provides a common ground for concepts and terminology (see Appendix A). We proceed through theory to applications that are of interest in research, development and design, as well as in test and operating engineering practice.

This book presents recent advances related to the following two topics: how mechanical fields close to material or geometrical singularities such as cracks can be determined; how failure criteria can be established according to the singularity degrees related to these discontinuities. Concerning the determination of mechanical fields close to a crack tip, the first part of the book presents most of the traditional methods in order to classify them into two major categories. The first is based on the stress field, such as the Airy function, and the second resolves the problem from functions related to displacement fields. Following this, a new method based on the Hamiltonian system is presented in great detail. Local and energetic approaches to fracture are used in order to determine the fracture parameters such as stress intensity factor and energy release rate. The second part of the book describes methodologies to establish the critical fracture loads and the crack growth criteria. Singular fields for homogeneous and non-homogeneous problems near crack tips, v-notches, interfaces, etc. associated with the crack initiation and propagation laws in elastic and elastic-plastic media, allow us to determine the basis of failure criteria. Each phenomenon studied is dealt with according to its conceptual and theoretical modeling, to its use in the criteria of fracture resistance; and finally to its implementation in terms of feasibility and numerical application. Contents 1. Introduction. Part 1: Stress Field Analysis Close to the Crack Tip 2. Review of Continuum Mechanics and the Behavior Laws. 3. Overview of Fracture Mechanics. 4. Fracture Mechanics. 5. Introduction to the Finite Element Analysis of Cracked Structures. Part 2: Crack Growth Criteria 6. Crack Propagation. 7. Crack Growth Prediction in Elements of Steel Structures Submitted to Fatigue. 8. Potential Use of Crack Propagation Laws in Fatigue Life Design.

Many people find the concept of fracture and damage mechanics to be somewhat problematic, mainly because, until recently, close attention in mechanics was focused especially on the strength and resistance of materials. In this sense, to speak of fracture is as uncomfortable for some as it is to speak of a deadly disease. In confronting and preventing a fatal disease, one must understand its complexity, symptoms, and behavior; by the same token, in securing the strength of an engineering structure, one must understand the reasons and type of its potential failure. This book will provide knowledge and insights on this matter to its readers.

The planning meeting for a conference on Dynamic Crack Propagation was held at M.LT. in February 1971 and attended by research workers from several industrial, governmental and academic organizations. It was felt that a more specialized meeting would provide a better opportunity for both U.S. and foreign researchers to exchange their ideas and views on dynamic fracture, a subject which is seldom emphasized in national or international fracture conferences. Dynamic crack propagation has been a concern to specialists in many fields: continuum mechanics, metallurgy, geology, polymer chemistry, orthopedics, applied mathematics, as well as structural design and testing. It impinges on a wide variety of problems such as rock breaking and earthquakes, pressure vessels and line pipes, comminution and the per formance of armament and ordnance, etc. Advances have been numerous, covering theories and experiments from both the microscopic and macro scopic points of view. Hence, the need for comparing the theoretical and experimental results and bridging the gaps between the atomistic and continuum approaches must be constantly emphasized. It also appeared that the overall problem of dynamic fracture could benefit from a con solidation of crack models proposed for the various types of materials: metals, ceramics, composites, rocks, glasses, polymers and biomaterials.

The book gives a description of the failure phenomena of ceramic materials under mechanical loading, the methods to determine their properties, and the principles for material selection. The book presents fracture mechanical and statistical principles and their application to describe the scatter of strength and lifetime, while special chapters are devoted to creep behaviour, multiaxial failure criteria and thermal shock behaviour. XXXXXXX Neuer Text Describing how ceramic materials fracture and fail under mechanical loading, this book provides methods for determining the properties of ceramics, and gives criteria for selecting ceramic materials for particular applications. It also examines the fracture-mechanical and statistical principles and their use in understanding the strength and durability of ceramics. Special chapters are devoted to creep behavior, criteria for multiaxial failure, and behavior under thermal shock. Readers will gain insight into the design of reliable ceramic components.

Cracks and Fracture consists of nine chapters in logical sequence. In two introductory chapters, physical processes in the vicinity of the crack edge are discussed and the fracture process is described. Chapter 3 develops general basic concepts and relations in crack mechanics, such as path independent integrals, stress intensity factors and energy flux into the crack edge region. Chapters 4-7 deal with elastostatic cracks, stationary or slowly moving elastic-plastic cracks, elastodynamic crack mechanics and elastoplastic aspects of fracture, including dynamic fracture mechanics. Appendices include general formulae, the basic theory of analytic functions, introduction to Laplace and Hankel transforms and description of certain basic relations, for instance for stress waves in solids. There is an extensive bibliography, containing references to both classical and recent work, and a comprehensive index. Presents an extensive bibliography containing references to both classical and recent works and a comprehensive index Appendices include general formulas, the basic theory of analytic functions, introduction to Laplace and Hankel transforms, and descriptions of certain basic relations, for instance for stress waves in solids