The assessment of crack initiation and/or propagation has been the subject of many past discussions on fracture mechanics. Depending on how the chosen failure criterion is combined with the solution of a particular theory of continuum mechanics, the outcome could vary over a wide range. Mod elling of the material damage process could be elusive if the scale level of observation is left undefined. The specification of physical dimension alone is not sufficient because time and temperature also play an intimate role. It is only when the latter two variables are fixed that failure predictions can be simplified. The sudden fracture of material with a pre-existing crack is a case in point. Barring changes in the local temperature,* the energy released to create a unit surface area of an existing crack can be obtained by considering the change in elastic energy of the system before and after crack extension. Such a quantity has been referred to as the critical energy release rate, G e, or stress intensity factor, K Ie. Other parameters, such as the crack opening displacement (COD), path-independent J-integral, etc. , have been proposed; their relation to the fracture process is also based on the energy release concept. These one-parameter approaches, however, are unable simultaneously to account for the failure process of crack initiation, propagation and onset of rapid fracture. A review on the use of G, K I, COD, J, etc. , has been made by Sih [1,2].

Proceedings of First USA-Greece Symposium on Mixed Mode Crack Propagation, Athens, Greece, 18-22 August, 1980

The purpose of this book is to present, describe and demonstrate the use of numerical methods in solving crack problems in fracture mechanics. The text concentrates, to a large extent, on the application of the Boundary Element Method (BEM) to fracture mechanics, although an up-to-date account of recent advances in other numerical methods such as the Finite Element Method is also presented. The book is an integrated presentation of modem numerical fracture mechanics, it contains a compilation of the work of many researchers as well as accounting for some of authors' most recent work on the subject. It is hoped that this book will bridge the gap that exists between specialist books on theoretical fracture mechanics on one hand, and texts on numerical methods on the other. Although most of the methods presented are the latest developments in the field of numerical fracture mechanics, the authors have also included some simple techniques which are essential for understanding the physical principles that govern crack problems in general. Different numerical techniques are described in detail and where possible simple examples are included, as well as test results for more complicated problems. The book consists of six chapters. The first chapter initially describes the historical development of theoretical fracture mechanics, before proceeding to present the basic concepts such as energy balance, stress intensity factors, residual strength and fatigue crack growth as well as briefly describing the importance of stress intensity factors in corrosion and residual stress cracking.

This International Conference on Analytical and Experimental Fracture Me chanics was organized jointly by the Centro Sperimentale Metallurgico, S. p. A. , Lehigh University and Italsider S. p. A. It took place at the Hotel Midas Palace in Rome, Italy, during 23-27 June, 1980. There were more than 150 attendees from 19 different countries: Australia, Austria, Belgium, Canada, People's Re public of China, Czechoslovakia, Finland, Federal Republic of Germany, Hungary, Israel, Italy, Japan, The Netherlands, Poland, Switzerland, Turkey, UK, USA and USSR. Dr. G. M. Costa from Finsider officially opened the Conference and gave the Welcome Address. More than 70 technical papers were presented at three con current sessions. There were six plenary lectures that helped to integrate the diverse efforts, e. g. , analytical fracture mechanics, testing methods, metallur gical effects, corrosion fatigue, dynamic crack propagation and weldments of in dividual researchers. In addition to providing an overall view of the current status of fracture mechanics technology, particular emphasis was given to methods of controlling fracture in gas pipeline structures. The members of the Organizing Committee made a special effort to organize a panel discussion on the application of fracture mechanics technology to the safe design of large diameter pipelines. Dr. Michele Civallero from Italsider and Professor George C. Sih from Lehigh University served as panel Co-Chairmen and delivered survey lectures to stimulate questions from the audience.

From time to time the International Journal of Fracture has presented matters thought to be of special interest to its readers. In previous special issues (December 1980 and April 1981), Dr H.W. Liu as Guest Editor presented a series of review papers dealing with fatigue processes and characteristics in metals and non-metals. Continuing this policy, which is consistent with our stated objectives, a second review dealing with time depen dence in the fracture process, including the effect of material inertia but essentially excluding very strong shock effects in solids, has been assembled under the generic term "dynamic fracture." We hope that the ensuing state-of-the-art review will yield an instructive and timely product which readers will find useful. To assist us in presenting this subject, we have prevailed upon a well-known worker in dynamic fracture, Dr W.G. Knauss, Professor of Aeronautics and Applied Mechanics, California Institute of Technology to act as Guest Editor for this special double issue. On behalf of the editors and publisher, I wish to express our indebtedness to Professor Knauss and his invited authors for undertaking this special effort."

Failures of many mechanical components in service result from fatigue. The cracks which grow may either originate from some pre-existing macroscopic defect, or, if the component is of high integrity but highly stressed, a region of localized stress concentration. In turn, such concentrators may be caused by some minute defect, such as a tiny inclusion, or inadvertent machining damage. Another source of surface damage which may exist between notionally 'bonded' components is associated with minute relative motion along the interface, brought about usually be cyclic tangential loading. Such fretting damage is quite insidious, and may lead to many kinds of problems such as wear, but it is its influence on the promotion of embryo cracks with which we are concerned here. When the presence of fretting is associated with decreased fatigue performance the effect is known as fretting fatigue. Fretting fatigue is a subject drawing equally on materials science and applied mechanics, but it is the intention in this book to concentrate attention entirely on the latter aspects, in a search for the quantification of the influence of fretting on both crack nucleation and propagation. There have been very few previous texts in this area, and the present volume seeks to cover five principal areas; (a) The modelling of contact problems including partial slip under tangentialloading, which produces the surface damage. (b) The modelling of short cracks by rigorous methods which deal effectively with steep stress gradients, kinking and closure. (c) The experimental simulation of fretting fatigue.

For a brief period during the latter part of World War II, Nevill F. Mott led a theoretical group at Fort Halstead in the United Kingdom that tackled scientific issues related to pressing war-time concerns. Among later awards and honors, Mott was knighted and a recipient of the Nobel Prize. While at Fort Halstead, he undertook an effort to theoretically describe the statistical fragmentation of munitions subjected to intense explosive loading. Mott`s original internal reports contain seminal theoretical concepts on the physics and statistics of dynamic fracture and fragmentation, which have provided the inspiration for numerous later modeling efforts and engineering formulae. Some of his most forward-looking thoughts on the micromechanical and molecular aspects of fracture are included in these publications. The present book surveys the theoretical analysis put forth by Mott with particular focus on his efforts to characterize the size and distribution of fragments resulting from a dynamic fragmentation event. Copies of the original internal reports of Mott and his co-workers are included. The book also pursues additional theoretical analysis with the intent of delving further into the physical ideas and unfinished analysis implicit in Mott`s original studies. This book will be of interest to all scientists and engineers concerned with the dynamic fracture and fragmentation of solid bodies subject to intense transient loads imparted by explosive detonation and high-velocity impact from both the historical and modern perspective.

1) Includes a chapter on early theories on fracture as well as modern understandings 2) Contains a chapter on fatigue crack and creep fatigue crack 3) Provides an in-depth discussion of both linear elastic and nonlinear fracture mechanics 4) Includes both solved and unsolved example problems and end of chapter problems, and instructor support materials are also available

From time to time the International Journal of Fracture has presented matters thought to be of special interest to its readers. The last special topic review was presented by Drs W.G. Knauss and AJ. Rosakis as Guest Editors in four issues, January-April 1990, under the general title of Non Linear Fracture. It contained sections on damage mechanisms, interfaces and creep, time depen dence, and continuum plasticity insofar as they affect the mechanisms of the fracture process. Continuing this policy, which is consistent with our stated objectives, the two September issues deal with the behavior of concrete and cementious materials during fracture initiation and propagation. We hope that the ensuing state-of-the-art review will yield another instructive and timely product which readers will find useful. To assist us in presenting this subject, we have prevailed upon a well-known international expert in concrete behavior, Dr. Z.P. Bazant, Walter P. Murphy Professor of Civil Engineering, of Northwes tern University to act as Guest Editor. On behalf of the editors and publishers, I wish to thank Professor BaZant and his invited authors for undertaking this special effort. M.L. WILLIAMS Pittsburgh, Pennsylvania Editor-in-Chief September 1991 International Journal of Fracture 51: ix-xv, 1991. Z.P. Bafant (ed.), Current Trends in Concrete Fracture Research.

In this volume a survey of the most relevant nonlinear crack models is provided, with the purpose of analyzing the nonlinear mechanical effects occurring at the tip of macrocracks in quasi-brittle materials - such as concrete, rocks, ceramics, polymers, high-strength metallic alloys - and in brittle-matrix fibre-reinforced composites. Such local effects, as, for example, plastic deformation, yielding, strain-hardening, strain-softening, mechanical damage, matrix microcracking, aggregate debonding, fibre bridging, fibre slippage, crazing, and so on, are properly described through different simplified models, representing the peculiarities of the phenomena involved. The models are introduced and described separately and then compared in the last part of the book. This volume will be of interest to students, professionals and researchers in the field of nonlinear fracture mechanics.

The main scope of this Cargese NATO Advanced Study Institute (June 5-17 2000) was to bring together a number of international experts, covering a large spectrum of the various Physical Aspects of Fracture. As a matter of fact, lecturers as well as participants were coming from various scientific communities: mechanics, physics, materials science, with the common objective of progressing towards a multi-scale description of fracture. This volume includes papers on most materials of practical interest: from concrete to ceramics through metallic alloys, glasses, polymers and composite materials. The classical fields of damage and fracture mechanisms are addressed (critical and sub-critical quasi-static crack propagation, stress corrosion, fatigue, fatigue-corrosion . . . . as well as dynamic fracture). Brittle and ductile fractures are considered and a balance has been carefully kept between experiments, simulations and theoretical models, and between the contributions of the various communities. New topics in damage and fracture mechanics - the effect of disorder and statistical aspects, dynamic fracture, friction and fracture of interfaces - were also explored. This large overview on the Physical Aspects of Fracture shows that the old barriers built between the different scales will soon "fracture." It is no more unrealistic to imagine that a crack initiated through a molecular dynamics description could be propagated at the grain level thanks to dislocation dynamics included in a crystal plasticity model, itself implemented in a finite element code. Linking what happens at the atomic scale to fracture of structures as large as a dam is the new emerging challenge.

Today, Fracture Mechanics is a well known topic within the scientific community. Applications of Fracture Mechanics can be found in various fields ranging from solid mechanics and structures to materials sciences and computational mechanics. However, most of these results apply only to linear fracture mechanics of two-dimensional and homogeneous isotropic solids. Therefore there are still incompletely solved problems; such as non-linearity, frictional contact cracks, residual stresses in fracture mechanics, three-dimensional crack geometry, coupled cracked solid/fluid, etc. Recently, new topics related to crack detection based on different physical phenomena have appeared.

This book is an attempt to present, in a unified manner, different topics of Continuum and Fracture Mechanics: energy methods, conservation laws, mathematical methods to solve two-dimensional and three-dimensional crack problems. Moreover, a series of new subjects is presented in a straightforward manner, accessible to under-graduate students. These new topics take into consideration the thermodynamics of continuous media, including thermal and dynamical aspects. In addition, the book introduces the notion of duality or symmetry in Solids Mechanics. The loss of symmetry is exploited to provide a unique and powerful tool, called the reciprocity gap functional introduced by the authora (TM)s groups, to solve explicitly some important inverse problems arising in crack determination as well as in the earthquake inverse problem.

With its emphasis, initially on physical or experimental back-grounds, and then on analysis and theoretical results, rather than on numerical computations, this monograph is intended to beused by students and researchers in solids mechanics, mechanical engineering and applied mathematics.

This volume contains the papers presented at the IUT AM Symposium of "Mesoscopic Dynamics of Fracture Process and Materials Strength", held in July 2003, at the Hotel Osaka Sun Palace, Osaka, Japan. The Symposium was proposed in 2001, aiming at organizing concentrated discussions on current understanding of fracture process and inhomogeneous deformation governing the materials strength with emphasis on the mesoscopic dynamics associated with evolutional mechanical behaviour under micro/macro mutual interaction. The decision of the General Assembly of International Union of Theoretical and Applied Mechanics (IUT AM) to accept our proposal was well-timed and attracted attention. Driven by the development of new theoretical and computational techniques, various novel challenges to investigate the mesoscopic dynamics have been actively done recently, including large-scaled 3D atomistic simulations, discrete dislocation dynamics and other micro/mesoscopic computational analyses. The Symposium attracted sixty-six participants from eight countries, and forty two papers were presented. The presentations comprised a wide variety of fundamental subjects of physics, mechanical models, computational strategies as well as engineering applications. Among the subjects, discussed are (a) dislocation patterning, (b) crystal plasticity, (c) characteristic fracture of amorphous/nanocrystal, (d) nano-indentation, (e) ductile-brittle transition, (f) ab-initio calculation, (g) computational methodology for multi-scale analysis and others.

This book is concerned with the numerical solution of crack problems. The techniques to be developed are particularly appropriate when cracks are relatively short, and are growing in the neighbourhood of some stress raising feature, causing a relatively steep stress gradient. It is therefore practicable to represent the geometry in an idealised way, so that a precise solution may be obtained. This contrasts with, say, the finite element method in which the geometry is modelled exactly, but the subsequent solution is approximate, and computationally more taxing. The family of techniques presented in this book, based loosely on the pioneering work of Eshelby in the late 1950's, and developed by Erdogan, Keer, Mura and many others cited in the text, present an attractive alternative. The basic idea is to use the superposition of the stress field present in the unfiawed body, together with an unknown distribution of 'strain nuclei' (in this book, the strain nucleus employed is the dislocation), chosen so that the crack faces become traction-free. The solution used for the stress field for the nucleus is chosen so that other boundary conditions are satisfied. The technique is therefore efficient, and may be used to model the evolution of a developing crack in two or three dimensions. Solution techniques are described in some detail, and the book should be readily accessible to most engineers, whilst preserving the rigour demanded by the researcher who wishes to develop the method itself.

As Directors of this NATO Workshop, we welcome this opportunity to record formally our thanks to the NATO Scientific Affairs Division for making our meeting possible through generous financial support and encouragement. This meeting has two purposes: the first obvious one because we have collected scientists from East, far East and west to discuss new development in the field of fracture mechanics: the notch fracture mechanics. The second is less obvious but perhaps in longer term more important that is the building of bridges between scientists in the frame of a network called Without Walls Institute on Notch Effects in Fatigue and Fracture." Physical perception of notch effects is not so easy to understand as the presence of a geometrical discontinuity as a worst effect than the simple reduction of cross section. Notch effects in fatigue and fracture is characterised by the following fundamental fact: it is not the maximum local stress or stress which governs the phenomena of fatigue and fracture. The physic shows that a process volume is needed probably to store the necessary energy for starting and propagating the phenomenon. This is a rupture of the traditional "strength of material" school which always give the prior importance of the local maximum stress. This concept of process volume was strongly affirmed during this workshop.

Concrete has traditionally been known as a material used widely in the construction of roads, bridges and buildings. Since cost effectiveness has always been one of the more important aspects of design, concrete, when reinforced and/or prestressed, is finding more use in other areas of application such as floating marine structures, storage tanks, nuclear vessel containments and a host of other structures. Because of the demand for concrete to operate under different loading and environmen tal conditions, increasing attention has been paid to study concrete specimens and structure behavior. A subject of major concern is how the localized segregation of the constituents in concrete would affect its global behavior. The degree of nonhomogeneity due to material property and damage. by yielding and/or cracking depends on the size scale and loading rate under consideration. Segregation or clustering of aggregates at the macroscopic level will affect specimen behavior to a larger degree than it would to a large structure such as a dam. Hence, a knowledge of concrete behavior over a wide range of scale is desired. The parameters governing micro-and macro-cracking and the techniques for evaluating and observing the damage in concrete need to be better understood. This volume is intended to be an attempt in this direction. The application of Linear Elastic Fracture Mechanics to concrete is discussed in several of the chapters."

These volumes contain contributions from a conference on the themes of measurement and prediction of residual stress in railroad rails. The subtitle, Effects of rail integrity and railroad economics', expresses an ultimate goal of reducing technical results to practical knowledge of interest to transportation engineers. Volume I contains elements of practical railway experience, laboratory tests, including experimental strees analysis, and theoretical evaluations of residual stress, crack propagation, and rail fracture. Observations of the effects of residual stress on rails in service, field tests, and laboratory experiments and recounted in the first three chapters of the volume. Experiments in which samples of new rail are subjected to precisely controlled rolling contact loads under laboratory conditions are dealt with in Chapters 4 and 5. Chapter 6 describes a method for programming loads on compact tension specimens to stimulate the stress intensity factor history of an internal transverse crack in rail head. Chapter 7 outlines a method for setting rail inspection intervals in service, based on what is presently known about the behaviour of transverse cracks in the rail head. The remainder of the volume deals with experimental stress analysis. Chapter 8 describes an elaborate procedure for combining stair change and length to evaluate internal stress distribution, and several other measurement techniques are also evaluated as possible alternates. Chapter 9 discusses the neutron diffraction method and its recent application to rail. Chapter 10 summarizes a technique based on MoirA(c) interferometry and reports on the first step in the developments of rail stress measurementprocedure based on this alternate. Chapter 13 concludes the experimental contributions with a summary of some typical measurements of the residual stress states in rails from several different producers and service environments in Europe. The reader will find that a reasonable qualitative picture of the rail residual stress field emerges from the experimental stress analyses. However, the details always vary from one rail to another, and there are sufficient differences to prevent the drawing of general quantitative conclusions from the experimental work alone. Theoretical and numerical analyses' are presented in Volume II, in the hope that models based on solid mechanics can correlate the experimental stress measurements and lead to a better understanding of the effects of residual stress upon crack propagation, fracture, and ultimately the economics of rail in the modern railroad environment.

In this volume on the mechanics of fracture of Portland cement concrete, the general theme is the connection between microstructural phenomena and macroscopic models. The issues addressed include techniques for observation over a wide range of scales, the influence of .microcracking on common measures of strength and de formability , and ultimately, the relationship between microstructural changes in concrete under load and its resistance to cracking. It is now commonly accepted that, in past attempts to force-fit the behavior of concrete into the rules of linear elastic fracture mechanics, proper attention has not been paid to scale effects. Clearly, the relationships among specimen size, crack length and opening, and characteristic material fabric dimensions have been, in comparison to their counterparts in metals, ceramics, and rocks, abused in concrete. Without a fundamental understanding of these relationships, additional testing in search of the elusive, single measure of fracture toughness has spawned additional confusion and frustration. No one is in a better position to document this observation than Professor Mindess.

An International Conference on the Application of Fracture Mechanics to Ma terials and Structures was held at the Hotel Kolpinghaus in Freiburg, West Ger many, June 20-24, 1983. It was attended by more than 250 participants from different countries which include Austria, Canada, Czechoslovakia, Democratic Republic of Germany, Denmark, Federal Republic of Germany, Finland, France, Greece, Hungary, Israel, Italy, Japan, Netherlands, Norway, People's Republic of China, Portugal, Sweden, Switzerland, United Kingdom, United States of America, USSR and Yugoslavia. Conference Co-Chairmen were Professor G. C. Sih, Lehigh University, Bethle hem, Pennsylvania, U. S. A., Dr. E. Sommer, Fraunhofer-Institut fur Werkstoff mechanik, Freiburg, FRG and Professor W. Dahl, Rheinisch-Westfalische Technische Hochschule, Aachen, FRG. Dr. Wenrich, as the representative of the Land Baden-WUrttemberg, delivered the opening address with the remarks that International Conferences can serve the means to further enhance the technology development of a country. He empha sized that the Federal Republic of Germany is presently in need of strengthening the engineering manpower in order to keep her in a competitive position. The Conference was officially cast off with the leading plenary lectures that under lined the theme of the technical lectures for the first day. This pattern was observed for the five-day meeting. The interplay between material and design re quirements was the theme and emphasized in many of the technical presentations that amounted to approximately ninety (90) papers."

This book was written to serve as both a professional's overview of the entire field of fatigue and fracture mechanics as it is currently practiced, and as an introduction to the application of the Fracture Mechanics of Ductile Metals (FMDM) theory. Particular benefits include: Application of fracture mechanics concepts to metallic structure, composites, welds and bolted joints. Extensive discussion of two welding techniques currently used in aerospace and aircraft structure, with emphasis given to state-of-the-art friction stir welding techniques. Life assessment of welded and bolted joints, with example problems. Damage tolerance and durability assessment of composites, not found in any other book published in this area. Presentation of Elastic-Plastic Fracture Mechanics (EPFM). Application of multi-specimen and single-specimen techniques to obtain fracture properties. Introduction to Fracture Mechanics of Ductile Metals (FMDM) theory to determine residual strength capability of structural metals. Discussion of techniques to determine the material fracture toughness properties without the need for laboratory testing. This is the first single text to present applications of fatigue and fracture mechanics to metals and composites and also include practical applications and example problems. It will be an essential reference for researchers, practitioners, and students alike.

Intended for engineers from a variety of disciplines that deal with structural materials, this text describes the current state of knowledge of how fractures in materials form and propagate, leading to failure. The book begins by describing the fracture process at the two extremes of scale: first in the context of atomic structures, then in terms of a continuous elastic medium. Treating the fracture process in increasingly sophisticated ways, the book then considers plastic corrections and the procedures for measuring the toughness of materials. Practical considerations are then discussed, including crack propagation, geometry dependence, flaw density, mechanisms of failure by cleavage, the ductile-brittle transition, and continuum damage mechanics. The text concludes with discussions of generalized plasticity and the link between the microscopic and macroscopic aspects. The text is suitable for advanced undergraduates. Problems are provided at the end of each chapter.

Composites offer great promise as light weight and strong materials for high performance structures. One of the major advantages of these materials as compared with metals is the basic way in which heterogeneity resist crack extension. In a fiber/matrix composite system, the fibers tend to cause cracks to form at closer spacing and delay the formation of a large crack. The enhancement of local failure such as fiber breaking, matrix cracking and interface debonding further reduces the energy level which might have otherwise reached the point of catastrophic failure. Even though substantial tests have been made on composite materials, little has been gained in the understanding and development of a predic tive procedure for composite failure. There are fundamental difficulties associated with incorporating the nonhomogeneous and anisotropic prop erties of the composite into the continuum mechanics analysis. Additional uncertainties arise from voids and defects that are introduced in the composite during manufacturing. Even a small quantity of mechanical imperfections can cause a marked influence on the composite strength. Moreover, the interface properties between the fibers and matrix or bonded laminae can also affect the load transmission characteristics significantly. It would be impossible to establish predictive procedures for composite failure unless realistic guidelines could be developed to control the manufacturing quality of composite systems."

In this book a systematic discussion of crack problems in elastic-plastic materials is presented. The state of the art in fracture mechanics research and assessment of cracks is documented, with the help of analytic, asymptotic methods as well as finite element computations. After a brief introduction to fracture mechanics, the two-parameter concept for stationary cracks is studied in addition to the issues in three-dimensional crack fields under coupling with strong out-of-plane effects. Cracks along interfaces and crack growth problems under mixed mode conditions are also treated. A systematic study of stress singularities for different notches is accompanied by detailed finite element computations.

This is not just another book on fracture mechanics. In recent years, there have been many books published on this subject in an attempt to assess the state of the art and its applications. The majority of the work dealt with energy release rate or critical stress intensity factor and is applicable only to fracture toughness testing. The main reason for this restriction is that the energy release concept cannot easily be extended to mixed mode fracture that occurs in practice as the rule rather than the exception. Cracks will normally curve or turn because the direction of loading can change as a function of time. Their directions of growth cannot be assumed as an a priori and must be determined from a pre-assumed criterion. Analysts are still perplexed with selecting an appropriate fracture criterion because it requires much discernment and judgement. Criteria which often appeared valid for idealized situations are quickly dis credited when encountering more complex physical phenomena. Moreover, the claim of generality cannot be justified on the basis of agreement between theory and experiment for a few simple examples."

Within the last two decades fracture theory has been one of the most rapidly advancing fields of continuous media mechanics. Noteworthy suc cess has been achieved in linear fracture mechanics where the propagation of the macrocrack in elastic materials is under study. However, fracture of materials is by no means a simple process since it involves fracture of structural elements ranging from atomic sizes to macrocracks. To obtain all information about how and why materials fail, all stages of the process must be studied. For a long time both mechanical engineers and physicists have been concerned with the problem of the fracture of solids. Unfortunately, most of their work has been independent of the others. To solve the problem not only requires the minds and work of mechanical engineers and physicists but chemists and other specialists must be consulted as well. In this book we will consider some conclusions of the "physical" and "mechanical" schools acquired by the A. F. Joffe Physics-Technical Institute of the USSR Academy of Sciences in Leningrad and the Institute of Polymer Mechanics of Latvian SSR Academy of Sciences in Riga. The methods for studying the phenomena of fracture applied at both Institutes are different yet complimentary to one another; the materials tested are also sometimes different."