Download or read book Development of Numerical Approaches to Predict Ductile and Cleavage Fracture of Structural Materials written by Guihua Zhang and published by . This book was released on 2007 with total page 131 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Numerical simulations mainly using finite element method are playing a more and more important role in prediction of fracture-induced failure for high performance structure. This thesis seeks to develop numerical approaches to predict ductile and cleavage fracture in structural materials. For ductile fracture, the discrete void approach reveals the failure mechanisms explicitly and is used to study the trends of fracture toughness. The porous continuum approach provides an effective means to predict extensive crack propagation. We consider the occurrence of material failure (void coalescence) as when localization of plastic flow takes place in the inter-void ligament and obtain the failure criterion as a function of the stress triaxiality ratio and the Lode angle. The Gologanu-Leblond Devaux (GLD) model, which accounts for the evolution of both void volume and void shape, is used to describe the porous placticity behavior and is implemented into ABAQUS via a user subroutine. Numerical simulations are performed to predict extensive crack growth in ductile solids for a thin aluminum 2024-T3 plate and verified by successful predication of crack extension in various specimens, including the multiple site damage speciments. The effect of stress triaxiality and Lode angle is further analyzed and the Xue-Wierzbicki fracture locus is employed as a criterion for void colescence. Combination of GLD model and X-W fracture locus is then applied to a DH-36 steel with specimens experiencing a wide range of stress triaxiality and Lode angles at failure. The numerical simulation results agree very well with the experimental results. For cleavage fracture, a modified three parameter Weibull stress model is proposed and used to predict the fracture of A508 steel at three different temperatures. By integrating the Weibull stress model over the plastic process zone, the failure probability can be obtained and comparison is made with the experiment result. Issues addressed include calibration of the model parameters, introduction of a threshold parameter, dependencies of the model parameters on temperature, plastic strain effect and crack tip triaxiality effect, etc."--Abstract.

Download or read book Dissertation Abstracts International written by and published by . This book was released on 2008 with total page 994 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1969 with total page 1090 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Introducing Heterogeneity Into Brittle Fracture Modeling of a 22NiMoCr37 Ferritic Steel Ring Forging written by Xinglong Zhao and published by . This book was released on 2008 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: Microstructural observations of the 22NiMoCr37 "EURO" reactor pressure vessel (RPV) steel ring forging reveal that there is a banded structure along the radial direction, composed of alternate layers rich in bainite and ferrite of wavelength ~1.5 ±0.75 mm. Heterogeneity at this meso (millimetre)-scale as well as at the micro (micrometre)-scale is currently not considered by conventional fracture mechanics. This paper describes the development of two numerical approaches aimed at incorporating such heterogeneity into the Beremin local approach model of cleavage failure, a model that has been used extensively for predicting the brittle fracture of ferritic RPV steels. The approaches developed combine the crystal plasticity finite element method (CPFEM) with continuum finite element analysis (FEA). CPFEM is applied to predict stress distributions at the microscale and to obtain phase-specific yield and flow properties for continuum FEA that derives stresses at the mesoscale. The results confirm that deformation heterogeneity on the micro- and mesoscales influences the local development of stress. At the microscale, the stress distribution within a representative volume of material located within the crack-tip plastic zone is shown to follow a normal distribution with a ratio of mean stress to standard deviation tending towards 0.1. These results indicate local stress levels that are within approximately ±20 % of those derived using continuum FEA. At the mesoscale, a periodic variation of stress is predicted within the larger representative volume. This variation is less dramatic than that observed at the microscale, though it still gives a spatial variation in maximum principal stress of approximately ±7 % between bainite- and ferrite-rich microstructural regions. These results suggest a significant influence of deformation heterogeneity on local stress levels, particularly at the microscale. However, the conventional Beremin cleavage fracture model, modified to account for microscale stress distribution, predicts only a modest influence of deformation heterogeneity on cleavage fracture probability, increasing Pf by just 5 %. This highlights the need to account for both the spatial variation in cleavage initiation sites as well as the distribution in stress throughout the microstructure. The paper describes one approach for this development.

Download or read book Comprehensive Structural Integrity written by Ian Milne and published by Elsevier. This book was released on 2003-07-25 with total page 4647 pages. Available in PDF, EPUB and Kindle. Book excerpt: The aim of this major reference work is to provide a first point of entry to the literature for the researchers in any field relating to structural integrity in the form of a definitive research/reference tool which links the various sub-disciplines that comprise the whole of structural integrity. Special emphasis will be given to the interaction between mechanics and materials and structural integrity applications. Because of the interdisciplinary and applied nature of the work, it will be of interest to mechanical engineers and materials scientists from both academic and industrial backgrounds including bioengineering, interface engineering and nanotechnology. The scope of this work encompasses, but is not restricted to: fracture mechanics, fatigue, creep, materials, dynamics, environmental degradation, numerical methods, failure mechanisms and damage mechanics, interfacial fracture and nano-technology, structural analysis, surface behaviour and heart valves. The structures under consideration include: pressure vessels and piping, off-shore structures, gas installations and pipelines, chemical plants, aircraft, railways, bridges, plates and shells, electronic circuits, interfaces, nanotechnology, artificial organs, biomaterial prostheses, cast structures, mining... and more. Case studies will form an integral part of the work.

Download or read book A Stress weighted Damage Model for Ductile Fracture Initiation in Structural Steel Under Cyclic Loading and Generalized Stress States written by Christopher M. Smith and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Fracture in steel structures represents a critical limit state in evaluating the safety and resiliency of civil infrastructure during earthquakes. This importance was demonstrated by the widespread fractures observed in older steel connections during the 1994 Northridge Earthquake, and in modern connections during the 2011 Christchurch Earthquake. The application of traditional crack-tip fracture mechanics to structural design provisions has successfully delayed the onset of Northridge-type brittle fracture. However, the extreme strain capacity in modern ductile connections increases the relevance of ductile fracture. Recent developments in 'local' fracture models have proven successful at predicting ductile fracture under many conditions. However, the application of these models has been limited due to their limited scope and difficulty in evaluation of the necessary continuum parameters. The current objective in the structural engineering community of replacing full-scale experiments with advanced finite element simulations require accurate models and calibration techniques to evaluate cyclic plasticity and fracture predictions. Motivated by the above requirements, the objectives of the present study are to (1) further the understanding of the ductile fracture mechanism for all stress, (2) develop robust methods for the calibration of constitutive parameters and local fracture models in highly plastic materials, and (3) to develop a new damage-based model to predict ductile fracture under all relevant structural conditions states (especially those with low stress triaxiality). These objectives are accomplished through an extensive experimental program, including 48 monotonic and cyclic specimens in geometries designed to effectively interrogate the fracture criteria. A total of six specimen designs are tested, including three original designs developed for the current study. Complementary finite element analyses are used to evaluate the local fracture criteria, and micrographic examination and void cell simulations provide insight into the fracture mechanism at varying stress states. The data from these experiments and the derived fracture model demonstrate the importance of the deviatoric stress state, in addition to the hydrostatic pressure, in the fracture ductility of steel. Specifically, material in a plane strain condition is found to exhibit about 50\% more fracture ductility than material in an axisymmetric stress condition. Through meta-analysis of test data from this and previous studies, ductile fracture is found to be prohibited under negative (compressive) hydrostatic pressure.

Download or read book Application of Fracture Mechanics to Materials and Structures written by George C. Sih and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 1096 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Fracture of Structural Materials written by A. S. Tetelman and published by John Wiley & Sons. This book was released on 1967 with total page 724 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Micromechanism of Cleavage Fracture of Metals written by Jianhong Chen and published by Butterworth-Heinemann. This book was released on 2014-09-15 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this book the authors focus on the description of the physical nature of cleavage fracture to offer scientists, engineers and students a comprehensive physical model which vividly describes the cleavage microcracking processes operating on the local (microscopic) scale ahead of a defect. The descriptions of the critical event and the criteria for cleavage fracture will instruct readers in how to control the cleavage processes and optimize microstructure to improve fracture toughness of metallic materials. Physical (mechanical) processes of cleavage fracture operating on the local (microscopic) scale, with the focus on the crack nucleation and crack propagation across the particle/grain and grain/grain boundaries Critical event, i.e., the stage of greatest difficulty in forming the microcrack, which controls the cleavage fracture Criteria triggering the cleavage microcracking with incorporation of the actions of macroscopic loading environment into the physical model Effects of microstructure on the cleavage fracture, including the effects of grain size, second phase particles and boundary Comprehensive description of the brittle fracture emerging in TiAl alloys and TiNi memory alloys

Download or read book Fatigue and Fracture Mechanics written by John H. Underwood and published by ASTM International. This book was released on 1997 with total page 697 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mechanical Behavior and Fracture of Engineering Materials written by Jorge Luis González-Velázquez and published by Springer Nature. This book was released on 2019-08-29 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the theoretical concepts of stress and strain, as well as the strengthening and fracture mechanisms of engineering materials in an accessible level for non-expert readers, but without losing scientific rigor. This volume fills the gap between the specialized books on mechanical behavior, physical metallurgy and material science and engineering books on strength of materials, structural design and materials failure. Therefore it is intended for college students and practicing engineers that are learning for the first time the mechanical behavior and failure of engineering materials or wish to deepen their understanding on these topics. The book includes specific topics seldom covered in other books, such as: how to determine a state of stress, the relation between stress definition and mechanical design, or the theory behind the methods included in industrial standards to assess defects or to determine fatigue life. The emphasis is put into the link between scientific knowledge and practical applications, including solved problems of the main topics, such as stress and strain calculation. Mohr's Circle, yield criteria, fracture mechanics, fatigue and creep life prediction. The volume covers both the original findings in the field of mechanical behavior of engineering materials, and the most recent and widely accepted theories and techniques applied to this topic. At the beginning of some selected topics that by the author's judgement are transcendental for this field of study, the prime references are given, as well as a brief biographical semblance of those who were the pioneers or original contributors. Finally, the intention of this book is to be a textbook for undergraduate and graduate courses on Mechanical Behavior, Mechanical Metallurgy and Materials Science, as well as a consulting and/or training material for practicing engineers in industry that deal with mechanical design, materials selection, material processing, structural integrity assessment, and for researchers that incursion for the first time in the topics covered in this book.

Download or read book Advances in Fracture Research written by Alberto Carpinteri and published by Springer. This book was released on 2006-07-28 with total page 262 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a spin-off from the International Journal of Fracture and collects lectures and papers presented at the 11th International Conference on Fracture (ICF11), March 20-25, 2005. Included in this volume are introductory addresses, as well as remarks on the presentation of honorary degrees. A collection of papers follows, including presentations by such eminent scientists as B.B. Mandelbrot, G.I. Barenblatt, and numerous others, reviewing advanced research in fracture.

Download or read book Advances in Structures written by Gregory J Hancock and published by CRC Press. This book was released on 2003 with total page 724 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume is an outcome of the international conference on advances in structures: steel, concrete, composite and aluminium in Sydney in 2003. It focuses on researches in composite design, fire engineering, light gauge construction, advanced structural analysis and concrete filled tubes.

Download or read book Ductile Fracture at Intermediate Stress Triaxialities written by Matthieu Dunand and published by . This book was released on 2013 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt: Accurate predictions of the onset of ductile fracture play an increasingly important role in the design of lightweight sheet metal structures. With the development of virtual prototyping practices, most transportation vehicles are now computer-engineered in great detail before launching their mass production, thereby requiring reliable models for plasticity and fracture. This thesis reports on a comprehensive investigation into the effect of stress state on the onset of ductile fracture of an Advanced High Strength Steel (AHSS), covering development of new experimental procedures, material characterization and phenomenological as well as micro-mechanical modeling of the onset of fracture. Based on an extensive multi-axial experimental program, the anisotropic plasticity of the present material is described by a non-associated quadratic anisotropic model. Comparison of model predictions to experimental results reveals that the proposed model provides better predictions than associated isotropic or anisotropic quadratic models. Moreover, a structural validation is presented that demonstrates the higher prediction accuracy of the non-associated plasticity model. A hybrid experimental-numerical approach is proposed to investigate the dependence of the onset of fracture to stress state. The experimental program covers the complete range of positive stress triaxialities, from pure shear to equibiaxial tension. It includes different full thickness specimens as well as multi-axial fracture experiments where combinations of tension and shear loadings are applied to a newly developed butterfly-shaped specimen. Loading paths to fracture are determined for each experiment in terms of stress triaxiality, Lode angle parameter and equivalent plastic strain and show a non-monotonic and strong dependence of ductility to stress state. The extensive fracture characterization is used to evaluate the predictive capabilities of two phenomenological and physics-inspired fracture models (the Modified Mohr-Coulomb and a shear-modified Gurson model) that take the effect of the first and third stress tensor invariants into account in predicting the onset of fracture. Finally, a micro-mechanical model relating the onset of fracture to plastic localization into a narrow band at the micro-scale is developed. The effect of stress state on localization is investigated numerically by means of a 3D void-containing unit cell submitted to well-controlled and proportional loadings in the macroscopic stress state. Based on simulation results, an analytical localization criterion is proposed which defines an open convex envelope in terms of the shear and normal stresses acting on the plane of localization and correlates well with experimental results.

Download or read book IUTAM Symposium on Nonlinear Analysis of Fracture written by J.R. Willis and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 398 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume constitutes the Proceedings of the IUTAM Symposium on 'Nonlinear Analysis of Fracture', held in Cambridge from 3rd to 7th Septem ber 1995. Its objective was to assess and place on record the current state of understanding of this important class of phenomena, from the standpoints of mathematics, materials science, physics and engineering. All fracture phenomena are nonlinear; the reason for inclusion of this qualification in the title was to reflect the intention that emphasis should be placed on distinctive aspects of nonlinearity, not only with regard to material consti tutive behaviour but also with regard to insights gained, particularly from the mathematics and physics communities, during the recent dramatic ad vances in understanding of nonlinear systems in general. The expertise represented in the Symposium was accordingly very wide, and many of the world's greatest authorities in their respective fields participated. The Symposium remained focussed on issues of practical significance for fracture phenomena, with concentration on aspects that are still im perfectly understood. The most significant unifying issue in this regard is that of scale: this theme was addressed from several perspectives. One important aspect is the problem of passing information on one scale up or down, as an input for analysis at another scale. Although this is not always the case, it may be that the microscopic process of fracture is understood in some particular class of materials.

Download or read book Advances in Experimental Mechanics V written by Joao Quinta da Fonseca and published by Trans Tech Publications Ltd. This book was released on 2007-08-31 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt: Volume is indexed by Thomson Reuters CPCI-S (WoS). The papers contained in this useful volume fully reflect the diverse nature of the field of experimental mechanics. They have been compiled from contributions coming from all over the world and are grouped into the chapter-topics: Structural Integrity, Inverse Problems, Mechanical Modelling, Welded Structures, NDE, Micromechanical Testing, Impact of Composites, Impact and High Strain-Rate, and Dynamic Loading.

Download or read book Local Approach to Fracture written by Jacques Besson and published by Presses des MINES. This book was released on 2006 with total page 121 pages. Available in PDF, EPUB and Kindle. Book excerpt: Improving the structural integrity together with the performance (weight, time to failure,...) of structures requires a persisting effort in the field of mechanics of materials and structures. This can be achieved by a better understanding of the relationships between microscopic mechanisms and the macroscopic material behavior and structural response with respect to damage and fracture. This improvement strategy of materials, structures and assement methods can be described as local approach to fracture. The local approach to fracture is an active research field. Initially developped in the context of steel structures (pressure vessels), its application domain has become wider and now deals with various kinds of materials (metallic alloys, metal matrix composites, polymers, elastomers, concrete) as well as various physical deformation and damage mechanisms (plasticity, creep, fatigue, ductile fracture, brittle fracture, ...). This volume contains the proceedings on an international conference dedicated to these issues.