Download or read book Micromechanics Modelling of Ductile Fracture written by Zengtao Chen and published by Springer Science & Business Media. This book was released on 2013-04-02 with total page 335 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book summarizes research advances in micromechanics modeling of ductile fractures made in the past two decades. The ultimate goal of this book is to reach manufacturing frontline designers and materials engineers by providing a user-oriented, theoretical background of micromechanics modeling. Accordingly, the book is organized in a unique way, first presenting a vigorous damage percolation model developed by the authors over the last ten years. This model overcomes almost all difficulties of the existing models and can be used to completely accommodate ductile damage developments within a single-measure microstructure frame. Related void damage criteria including nucleation, growth and coalescence are then discussed in detail: how they are improved, when and where they are used in the model, and how the model performs in comparison with the existing models. Sample forming simulations are provided to illustrate the model’s performance.
Download or read book Application of Micromechanical Models to the Analysis of Ductile Fracture Under Dynamic Loading written by W. Böhme and published by . This book was released on 1995 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dynamic tensile tests and instrumented impact tests with Charpy-V-notch specimens and precracked Charpy specimens (SENB) are performed and simulated. Two strain-rate dependent micromechanical models based on the modified Gurson flow function are compared by simulating different dynamically loaded specimens. One purpose of the study is to investigate the influence of strain rate on the parameters of the micromechanical models and thus to check the applicability of these models for dynamic loading. Another purpose is to find out the relation between the micromechanical approach and conventional fracture mechanics.
Download or read book Ductile Fracture in Metal Forming written by Kazutake Komori and published by Academic Press. This book was released on 2019-10-11 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ductile Fracture in Metal Forming: Modeling and Simulation examines the current understanding of the mechanics and physics of ductile fracture in metal forming processes while also providing an approach to micromechanical ductile fracture prediction that can be applied to all metal forming processes. Starting with an overview of different ductile fracture scenarios, the book then goes on to explain modeling techniques that predict a range of mechanical phenomena that can lead to ductile fracture. The challenges in creating micromechanical models are addressed alongside methods of applying these models to several common metal forming processes. This book is suitable for researchers working in mechanics of materials, metal forming, mechanical metallurgy, and plasticity. Engineers in R&D industries involved in metal forming such as manufacturing, aerospace, and automation will also find the book very useful. - Explains innovative micromechanical modeling techniques for a variety of material behaviors - Examines how these models can be applied to metal forming processes in practice, including blanking, arrowed cracks in drawing, and surface cracks in upset forging - Provides a thorough examination of both macroscopic and microscopic ductile fracture theory
Download or read book Micro mechanical Simulation of Ductile Fracture Processes in Structural Steel written by Ryan James Cooke and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The micro-mechanics based approach to the study of ductile fracture has successfully overcome many of the limitations (such as large scale material yielding, cyclic loading, and size/scale dependence of J) of traditional fracture mechanics approaches (i.e. K, J and CTOD's). A number of the currently available micro-mechanics models (i.e. SMCS, Hancock and McKenzie, 1975; VGM, Kanvinde and Deierlein, 2006) predict fracture accurately under high triaxiality and axisymmetric conditions; however, the mentioned conditions do not encompass the full range of stress states (including low-triaxiality or non-axisymmetric conditions) which are relevant to the structural, mechanical and aerospace industries. As such, the primary objective of the work presented in this dissertation is to inform the development of a more general damage model which is applicable to a broader range of stress states and seismic (i.e. cyclic) loading which can result in ultra-low cycle fatigue (ULCF) failures. New model development is realized through a collaborative multi-scale approach which combines the results of an extensive test series (Smith, 2014) and a series of computational void simulations. To probe the full range of practical stress/loading conditions, a more general finite element (FE) framework for simulating the response of micro-voids is developed. The new void cell framework and the results of the 146 void simulations comprise the primary body of work presented in this dissertation. The void simulations can be divided into two groups: (1) those which effectively simulate an array of voids while modeling a representative void cell, and (2) those which explicitly model an array of voids. Void growth rates measured from the single void model (SVM) are used to inform the selection of a new functional form for the damage model presented in this dissertation while the multi-void model (MVM) provides qualitative and quantitative insights regarding localized deformation between neighboring voids. Findings from the MVM simulations are (1) in agreement with observations obtained from sectioned images (Smith, 2014) of fracture coupons that expose undergrown voids in the near vicinity of the failure surface and (2) are used to develop a strain-based indicator for localization initiation that shows strong agreement with failure strains observed from coupon scale tests (Myers, 2009). Moreover, the trends observed from both model types indicate that there is minimal void growth and that localization does not occur at low triaxialities. Both finding suggest that an alternate fracture mechanism than the traditionally excepted 'growth to coalescence' mechanism is active under these conditions. Despite the power of micro-mechanics based models, the ability to arrive at accurate fracture predictions is contingent on the calibration of the parameters which define the material constitutive response. The capability for complementary FE simulations to reproduce the force-displacement response obtained from physical tests (which is typically relied upon for model calibration) provides a false sense of security and neglects issues (i.e. non-uniqueness of the model parameter set) associated with model over-fitting. To investigate the susceptibility of typical calibration approaches to result in non-unique fits, a simple example is employed. Results of the example demonstrate that (1) multiple (and therefore non-unique) parameter sets may adequately reproduce the force-displacement response of typical calibration specimen and (2) that local plastic strains (often used to evaluate local fracture criteria) can result in error more than 65% despite agreement with the calibration metric. Thus, selection of parameter sets based solely on qualitative agreement between test data and complementary simulations can lead to erroneous results when evaluating material resistance to fracture.
Download or read book Micromechanics Based Simulation of Ductile Fracture in Structural Steels written by Ravi Kiran Yellavajjala and published by . This book was released on 2014 with total page 380 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Micromechanical Modelling of Damage and Fracture of Ductile Materials written by Dirk Steglich and published by . This book was released on 1998 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fracture Mechanics written by Dietmar Gross and published by Springer. This book was released on 2017-11-28 with total page 366 pages. Available in PDF, EPUB and Kindle. Book excerpt: - self-contained and well illustrated - complete and comprehensive derivation of mechanical/mathematical results with enphasis on issues of practical importance - combines classical subjects of fracture mechanics with modern topics such as microheterogeneous materials, piezoelectric materials, thin films, damage - mechanically and mathematically clear and complete derivations of results
Download or read book Application of Micromechanical Models to the Prediction of Ductile Fracture written by R. Kienzler and published by . This book was released on 1992 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ductile fracture behavior of different specimens is analyzed by continuum damage-mechanics techniques. A model introduced by Gurson and modified by Needleman and Tvergaard has been implemented in the finite element program package, ADINA. The damage parameters of the model are measured and calculated from smooth tension tests, and the characteristic material distance is estimated from compact tension experiments.
Download or read book Begynnelsebokst vernas placering m m written by Wald Zachrisson and published by . This book was released on 1920 with total page 224 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Application of Micromechanical Models of Ductile Fracture Initiation to Reactor Pressure Vessel Materials written by R. Chaouadi and published by . This book was released on 1996 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: The aim of the current study is the application of local micromechanical models to predict crack initiation in ductile materials. Two reactor pressure vessel materials have been selected for this study: JRQ IAEA monitor base metal (A533B C1.1) and Doel-IV weld material. Charpy impact tests have been performed in both un-irradiated and irradiated conditions. In addition to standard tensile tests, notched tensile specimens have been tested.
Download or read book Fracture Mechanics written by Walter G. Reuter and published by ASTM International. This book was released on 1995 with total page 842 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Relationship Between Constraint and Ductile Fracture Initiation as Defined by Micromechanical Analyses written by TL. Panontin and published by . This book was released on 1995 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: The overall objective of this study is to provide a proven methodology to allow the transfer of ductile fracture initiation properties measured in standard labora tory specimens to large, complex, flawed structures. A significant part of this work involved specifically addressing effects of constraint on transferability under large scale yielding conditions. The approach taken was to quantify constraint effects through micro-mechanical fracture models coupled with finite element generated crack tip stress-strain fields to identify the local condition corresponding to fracture initiation. Detailed finite element models predicted the influence of specimen geometry, loading mode, and material flow properties on the crack tip fields.
Download or read book Micromechanics of Fracture and Damage written by Luc Dormieux and published by John Wiley & Sons. This book was released on 2016-03-31 with total page 249 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book deals with the mechanics and physics of fractures at various scales. Based on advanced continuum mechanics of heterogeneous media, it develops a rigorous mathematical framework for single macrocrack problems as well as for the effective properties of microcracked materials. In both cases, two geometrical models of cracks are examined and discussed: the idealized representation of the crack as two parallel faces (the Griffith crack model), and the representation of a crack as a flat elliptic or ellipsoidal cavity (the Eshelby inhomogeneity problem). The book is composed of two parts: The first part deals with solutions to 2D and 3D problems involving a single crack in linear elasticity. Elementary solutions of cracks problems in the different modes are fully worked. Various mathematical techniques are presented, including Neuber-Papkovitch displacement potentials, complex analysis with conformal mapping and Eshelby-based solutions. The second part is devoted to continuum micromechanics approaches of microcracked materials in relation to methods and results presented in the first part. Various estimates and bounds of the effective elastic properties are presented. They are considered for the formulation and application of continuum micromechanics-based damage models.
Download or read book Stochastic Micromechanical Modeling of Cleavage Fracture in the Ductile brittle Transition Region written by David I. Auen Stienstra and published by . This book was released on 1990 with total page 504 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Modeling of Defects and Fracture Mechanics written by G. Herrmann and published by Springer. This book was released on 2014-05-04 with total page 211 pages. Available in PDF, EPUB and Kindle. Book excerpt: All materials contain numerous defects, such as microcracks, microvoids, inhomogeneities, dislocations, etc., which precede possible fracture. Thus mathematical modeling becomes necessary. This volume contains some introductory material, aspects of fracture mechanics, the theory of crystal defects, computational micromechanics, and the heterogenization methodology.
Download or read book Studies on Strain Localization Ductile Fracture and Damage in Structural Metals written by Yazhi Zhu and published by . This book was released on 2017 with total page 666 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the most important limit states in structural metals is ductile fracture, and the prediction of ductile fracture is of great importance in many engineering applications. The overall objective of the research reported in this dissertation is to advance the understanding and modeling of ductile fracture in metals. This research addresses three main issues: micromechanical modeling of ductile fracture, the development of a micromechanics-based ductile fracture model and its numerical implementation, and a numerical investigation of geometry and damage induced strain localization based on a nonlocal formulation. It has long been recognized that stress triaxiality is a key parameter affecting initiation of ductile fracture. More recently, shear stress has been identified as another important parameter, in addition to stress triaxiality, that influences the process of ductile fracture. In this research, a micromechanics-based model is proposed for predicting initiation of ductile fracture that couples both stress triaxiality and shear stress. The new model is based on a combination of the existing Rice-Tracey and modified maximum shear stress models. The new model is applied to construct the fracture locus of different types of metal alloys and is used to predict fracture initiation by numerical tools. The predicted results are in good agreement with experimental data reported in literature that covers a wide range of triaxialities and shear stress. Another portion of this research, within the framework of micromechanics, investigated the effect of combined normal and shear stress components on micro-void evolution and material behavior. This work involved finite element modeling of a cubic unit cell associated with a spherical void. The results show that the void growth process and macroscopic stress-strain response is highly dependent on the shear stress component. At different ranges of triaxialities, and with different void growth and coalescence mechanisms, shear stress has an important effect on the ductile fracture process. Numerical modeling of strain localization in ductile metals based on standard continuum mechanics exhibits non-convergent mesh sensitivity. This issue is addressed in the final portion of this research. A one-dimensional model based on the nonlocal theory is proposed to analyze geometry-induced strain localization, i.e., necking in structural metals. A nonlocal continuum damage model using the same enhanced continuum law is developed to deal with the damage induced strain localization in metals. Both models provide encouraging performance in eliminating the non-convergent mesh sensitivity problem. Such improved strain localization modeling techniques show potential to be useful for further exploration of ductile fracture phenomena.
Download or read book Micromechanisms of Fracture and Fatigue written by Jaroslav Pokluda and published by Springer Science & Business Media. This book was released on 2010-05-27 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: Micromechanisms of Fracture and Fatigue forms the culmination of 20 years of research in the field of fatigue and fracture. It discusses a range of topics and comments on the state of the art for each. The first part is devoted to models of deformation and fracture of perfect crystals. Using various atomistic methods, the theoretical strength of solids under simple and complex loading is calculated for a wide range of elements and compounds, and compared with experimental data. The connection between the onset of local plasticity in nanoindentation tests and the ideal shear strength is analysed using a multi-scale approach. Moreover, the nature of intrinsic brittleness or ductility of perfect crystal lattices is demonstrated by the coupling of atomistic and mesoscopic approaches, and compared with brittle/ductile behaviour of engineering materials. The second part addresses extrinsic sources of fracture toughness of engineering materials, related to their microstructure and microstructurally-induced crack tortuosity. Micromechanisms of ductile fracture are also described, in relation to the fracture strain of materials. Results of multilevel modelling, including statistical aspects of microstructure, are used to explain remarkable phenomena discovered in experiments. In the third part of the book, basic micromechanisms of fatigue cracks propagation under uniaxial and multiaxial loading are discussed on the basis of the unified mesoscopic model of crack tip shielding and closure, taking both microstructure and statistical effects into account. Applications to failure analysis are also outlined, and an attempt is made to distinguish intrinsic and extrinsic sources of materials resistance to fracture. Micromechanisms of Fracture and Fatigue provides scientists, researchers and postgraduate students with not only a deep insight into basic micromechanisms of fracture behaviour of materials, but also a number of engineering applications.
