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Fracture and damage in ouasibrittle structures: Experiment, modelling and computer analysis
1584
BOOK REVIEWS
Vol. 30, No. 12
composition, compressibility, magnetism, and some others. What is needed in materials science education is a comprehensive introduction to thermodynamical treatment of a number of phenomena which solid state physics literature generally covers but is sometimes too involved mathematically to be instructive for materials scientists. Such a treatment would discuss cooperative phenomena, for example, of magnetic or ferroelectric materials. Besides according recognition to modern fields of materials science, a basic introduction to rather old but still important concepts of thermodynamics could help stimulate students into being more interested in thermodynamics than they presently seem to be. Nevertheless, the present edition represents a valuable introduction to classical concepts of chemical thermodynamics. It is written in a clear style with appropriate figures, tables, and enough didactic touch. As many other textbooks of its kind, it could be useful as an introductory text, although its title is somethwat misleading. Reviewed University
by Jtirg Hulliger, Institute for Inorganic, Analytical of Berne, Freiestr. 3, CH-3012 Switzerland
and Physical
Chemistry,
FRACTURE
AND DAMAGE IN OUASIBRITTLE STRUCTURES: EXPERIMENT, AND COMPUTER ANALYSIS, by Z.P. Bazant, Z. Bittnar, M. Jirasek, and (Eds). Chapman & Hall, New York, 1994, pp. xiv + 646, price $59.95 ISBN o-419-19280-8.
MODELLING
J. Mazars paperbook,
This book represents the proceedings of the US-Europe Workshop on Fracture and Damage in Quasibrittle Structures held in Prague, Czech Republic during 2 l-23 September 1994. The workshop covered the highly complicated area of mathematical descriptions of intermediate behavior between ductile materials, where plastic flow dominates and brittle materials, well described by linear elastic fracture mechanics (LEFM). Many important materials fall into this category, such as concretes and mortars, rocks, toughened ceramics and alloys, wood and particle board, paper, and many fiber reinforced composites. The need for theoretical development has become apparent from the realization that without nonlinear generalization of fracture mechanics, reformulation of damage concepts, and increased attention to phenomena such as microcracks, bond failures, etc., current theories and finite element codes can not correctly predict failures of quasibrittle materials. The book is comprehensive, starting with reviews of continuum-based theories incorporating various foundations of statistics, thermodynamics and stress analyses of failure and damage models. The current trend, conspicuous in most of the articles in Part 1 is towards a blending of theories of classical fracture mechanics, nonlocal continuum theories and continuum damage mechanics. Part 2 addresses discrete crack models, and parts 3 and 4 cover dynamic and scale effects, respectively. Finite element and several numerical methods are covered next, followed by a description of a few experimental approaches. Specific materials are then covered, such as masonry, rocks, reinforced concrete and general fiber reinforced composites, particularly those with brittle matrices. As is apparent from Part 1, most of the present continuum failure theories spring from efforts intended at the modeling of strain-softening, i.e., the progressive development of regions of decreasing moduli under static or fatigue loading. Publications on this topic started to appear regularly in the early 1980s. The inadequacy of LEFM and classical fracture mechanics to handle the failure of concrete forced researchers in the civil
Vol. 30, No. 12
BOOK REVIEWS
1585
engineering area to build theories able to model the essential features of these failure processes. A key issue with the post-peak negative slope in the stress strain curves of concrete is to explain how damage localization eventually leads to fracture by the propagation of a macrocrack. Several articles (7,8,11) in Part 1 present theories that model the strain-softening zone as a damaged area. This approach is logical since stiffness decrease arises naturally from the central postulate of strain-averaging in damage mechanics. Article 6 deals with the so-called microplane model, which itself incorporates the concept of nonlocality, and extends it to anisotropic materials. Most noticeable are articles 3 and 10, which focus on modification of strain-softening theories to incorporate strong and weak shock discontinuities. The introduction of the latter in the balance laws allows a modeling of the propagation of the strain-softening zone. Article 5 also links the localization of failure to the formation of discontinuities, within the realm of tensile to mixed-mode failure transition in the failure envelopes. Articles 2, 4, and 7 in Part 1 tackle the issue of the anisotropy in damage initiation or development. It is a welcome trend to see attempts at extending the above-mentioned theories to materials other than cementitous, following previous literature where damage mechanics has been applied to light-weight composite materials. This is done in article 7 for unidirectional fibers composites, as well as in Part 9 of these proceedings. Special emphasis has been put on the issue of mesh sensitivity in the finite element analysis of strain-softening and localization phenomena, as well as in other models which deal with dynamic behavior, size effects, shear band computations, orthotropic laminates and damage and failure in general. A limited index is based on the key words assigned to individual papers. We note as expected a heavy emphasis on damage, softening, etc., as mentioned above, but also coverage of a small range of experimental techniques, including standard mechanical tests, acoustic emission, stereophotogrammetry, moire interferometry and laser speckle photography. Deformation processes such nonlinear viscoelasticity are unfortunately mentioned only in an abstract (article 61), while viscoplasticity is discussed in just two articles (20 and 36). This leaves plenty of room for future work on related materials such as polymer concretes, interlayer laminates and other toughened materials, matrices and/or structures. We can consider these proceedings as a milestone in the development of the science of “failure mechanics,” which both encompasses and links fracture mechanics, developed in the first half of this century, and damage mechanics, which emerged about a decade ago. We are thus dealing with research still in its infancy, where most questions are unanswered. In order to guide the reader in this uncharted area, it was therefore essential to adopt a format where all aspects of research would be tackled simultaneously: theoretical models, experiments and numerical results. This has been done in these proceedings. Reviewed by Ernest University,. Corvallis,
G. Wolff, Department OR 9733 1
of Mechanical
Engineering,
Oregon
State
AN INTRODUCTION TO METAL MATRIX COMPOSITES by T.W. Clyne and P.J. Withers. Cambridge Solid State Series. Cambridge University Press, 1995, pp. xiii + 509, price $47.95 paperback, ISBN O-521-48357-3. This book is an excellent introduction to the class of composite materials with metal matrices, with emphasis on the research work carried out over the last 30 years at
BOOK REVIEWS
Vol. 30, No. 12
composition, compressibility, magnetism, and some others. What is needed in materials science education is a comprehensive introduction to thermodynamical treatment of a number of phenomena which solid state physics literature generally covers but is sometimes too involved mathematically to be instructive for materials scientists. Such a treatment would discuss cooperative phenomena, for example, of magnetic or ferroelectric materials. Besides according recognition to modern fields of materials science, a basic introduction to rather old but still important concepts of thermodynamics could help stimulate students into being more interested in thermodynamics than they presently seem to be. Nevertheless, the present edition represents a valuable introduction to classical concepts of chemical thermodynamics. It is written in a clear style with appropriate figures, tables, and enough didactic touch. As many other textbooks of its kind, it could be useful as an introductory text, although its title is somethwat misleading. Reviewed University
by Jtirg Hulliger, Institute for Inorganic, Analytical of Berne, Freiestr. 3, CH-3012 Switzerland
and Physical
Chemistry,
FRACTURE
AND DAMAGE IN OUASIBRITTLE STRUCTURES: EXPERIMENT, AND COMPUTER ANALYSIS, by Z.P. Bazant, Z. Bittnar, M. Jirasek, and (Eds). Chapman & Hall, New York, 1994, pp. xiv + 646, price $59.95 ISBN o-419-19280-8.
MODELLING
J. Mazars paperbook,
This book represents the proceedings of the US-Europe Workshop on Fracture and Damage in Quasibrittle Structures held in Prague, Czech Republic during 2 l-23 September 1994. The workshop covered the highly complicated area of mathematical descriptions of intermediate behavior between ductile materials, where plastic flow dominates and brittle materials, well described by linear elastic fracture mechanics (LEFM). Many important materials fall into this category, such as concretes and mortars, rocks, toughened ceramics and alloys, wood and particle board, paper, and many fiber reinforced composites. The need for theoretical development has become apparent from the realization that without nonlinear generalization of fracture mechanics, reformulation of damage concepts, and increased attention to phenomena such as microcracks, bond failures, etc., current theories and finite element codes can not correctly predict failures of quasibrittle materials. The book is comprehensive, starting with reviews of continuum-based theories incorporating various foundations of statistics, thermodynamics and stress analyses of failure and damage models. The current trend, conspicuous in most of the articles in Part 1 is towards a blending of theories of classical fracture mechanics, nonlocal continuum theories and continuum damage mechanics. Part 2 addresses discrete crack models, and parts 3 and 4 cover dynamic and scale effects, respectively. Finite element and several numerical methods are covered next, followed by a description of a few experimental approaches. Specific materials are then covered, such as masonry, rocks, reinforced concrete and general fiber reinforced composites, particularly those with brittle matrices. As is apparent from Part 1, most of the present continuum failure theories spring from efforts intended at the modeling of strain-softening, i.e., the progressive development of regions of decreasing moduli under static or fatigue loading. Publications on this topic started to appear regularly in the early 1980s. The inadequacy of LEFM and classical fracture mechanics to handle the failure of concrete forced researchers in the civil
Vol. 30, No. 12
BOOK REVIEWS
1585
engineering area to build theories able to model the essential features of these failure processes. A key issue with the post-peak negative slope in the stress strain curves of concrete is to explain how damage localization eventually leads to fracture by the propagation of a macrocrack. Several articles (7,8,11) in Part 1 present theories that model the strain-softening zone as a damaged area. This approach is logical since stiffness decrease arises naturally from the central postulate of strain-averaging in damage mechanics. Article 6 deals with the so-called microplane model, which itself incorporates the concept of nonlocality, and extends it to anisotropic materials. Most noticeable are articles 3 and 10, which focus on modification of strain-softening theories to incorporate strong and weak shock discontinuities. The introduction of the latter in the balance laws allows a modeling of the propagation of the strain-softening zone. Article 5 also links the localization of failure to the formation of discontinuities, within the realm of tensile to mixed-mode failure transition in the failure envelopes. Articles 2, 4, and 7 in Part 1 tackle the issue of the anisotropy in damage initiation or development. It is a welcome trend to see attempts at extending the above-mentioned theories to materials other than cementitous, following previous literature where damage mechanics has been applied to light-weight composite materials. This is done in article 7 for unidirectional fibers composites, as well as in Part 9 of these proceedings. Special emphasis has been put on the issue of mesh sensitivity in the finite element analysis of strain-softening and localization phenomena, as well as in other models which deal with dynamic behavior, size effects, shear band computations, orthotropic laminates and damage and failure in general. A limited index is based on the key words assigned to individual papers. We note as expected a heavy emphasis on damage, softening, etc., as mentioned above, but also coverage of a small range of experimental techniques, including standard mechanical tests, acoustic emission, stereophotogrammetry, moire interferometry and laser speckle photography. Deformation processes such nonlinear viscoelasticity are unfortunately mentioned only in an abstract (article 61), while viscoplasticity is discussed in just two articles (20 and 36). This leaves plenty of room for future work on related materials such as polymer concretes, interlayer laminates and other toughened materials, matrices and/or structures. We can consider these proceedings as a milestone in the development of the science of “failure mechanics,” which both encompasses and links fracture mechanics, developed in the first half of this century, and damage mechanics, which emerged about a decade ago. We are thus dealing with research still in its infancy, where most questions are unanswered. In order to guide the reader in this uncharted area, it was therefore essential to adopt a format where all aspects of research would be tackled simultaneously: theoretical models, experiments and numerical results. This has been done in these proceedings. Reviewed by Ernest University,. Corvallis,
G. Wolff, Department OR 9733 1
of Mechanical
Engineering,
Oregon
State
AN INTRODUCTION TO METAL MATRIX COMPOSITES by T.W. Clyne and P.J. Withers. Cambridge Solid State Series. Cambridge University Press, 1995, pp. xiii + 509, price $47.95 paperback, ISBN O-521-48357-3. This book is an excellent introduction to the class of composite materials with metal matrices, with emphasis on the research work carried out over the last 30 years at