Download or read book Local Modeling of Constraint and Ductile Tearing Effects on Brittle Fracture Under Small Scale Yielding written by Euclydes Trovato Neto and published by . This book was released on 1999 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Constraint Effects in Fracture Theory and Applications written by Mark Kirk and published by ASTM International. This book was released on 1995 with total page 546 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Numerical Modeling of Ductile Tearing Effects on Cleavage Fracture Toughness written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Experimental studies demonstrate a significant effect of specimen size, a/W ratio and prior ductile tearing on cleavage fracture toughness values (J[sub c]) measured in the ductile-to-brittle transition region of ferritic materials. In the lower-transition region, cleavage fracture often occurs under conditions of large-scale yielding but without prior ductile crack extension. The increased toughness develops when plastic zones formed at the crack tip interact with nearby specimen surfaces which relaxes crack-tip constraint (stress triaxiality). In the mid-to-upper transition region, small amounts of ductile crack extension (often
Download or read book Numerical Modeling of Ductile Tearing Effects on Cleavage Fracture Toughness written by Robert H. Dodds and published by . This book was released on 1994 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Local Approach to Cleavage Fracture written by C S Wiesner and published by Abington Publishing. This book was released on 1995-12-14 with total page 78 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report assesses the current state of knowledge of the 'local approach' to cleavage fracture, reviews application to ferritic steels and their weldments and addresses limitations and disadvantages of the methodology.
Download or read book Effects of Prior Ductile Tearing on Cleavage Fracture Toughness in the Transition Region written by and published by . This book was released on 1993 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: Previous work by the authors described a micromechanics fracture model to correct measured J sub c-values for the mechanistic effects of large- scale yielding. This new work extends the model to also include the influence of ductile crack extension prior to cleavage. Ductile crack extensions of 10-15 X the initial crack tip opening displacement at initiation are considered in plane-strain, finite element computations The finite element results demonstrate a significant elevation in crack-tip constraint due to macroscopic 'sharpening' of the extending tip relative to the-blunt tip at the initiation of growth. However this effect is offset partially by the additional plastic deformation associated with the increased applied J required to grow the crack. The initial a/W ratio, tearing modulus, strain hardening exponent and specimen size interact in a complex manner to define the evolving near-tip conditions for cleavage fracture. The paper explores development of the new model, provides necessary graphs and procedures for its application and demonstrates the effects of the model on fracture data sets for two pressure vessel steels (A533B and A515). J- integral, Constraint, Scaling model, Ductile-brittle, Crack growth effects.
Download or read book Modeling the Constraint Effects on Fracture Toughness of Materials written by Sunil Kumar Prakash and published by . This book was released on 2009 with total page 87 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Cleavage fracture has been a very important subject for engineers for a long time because of the catastrophic result it may cause. The experimental results of cleavage fracture exhibit a large amount of scatter and show significant constraint effect, which motivated the development of statistical and micromechanics based methods in order to deal with such problem. The Weibull stress model, which is based on the weakest link statistics, uses two parameters, m and [sigma]u?, to describe the inherent distribution of the micro-scale cracks once the plastic deformation has occurred and to define the relationship between the macro and micro-scale driving forces for cleavage fracture. In this paper we examine constraint effects on cleavage fracture toughness numerically using a constraint function g(M) derived from the Weibull stress model. The non-dimensional function g(M) describes the evolution of constraint loss effects on fracture toughness relative to reference plane-strain small scale yielding (SSY) condition (T-stress=0). We performed detailed finite element analyses of single-edge notched bending speciments and compute g(M) functions for them. The g-function varies with parameters of the Weibull stress model, material flow properties and speciment geometry but not with absolute specimen size. Knowing the g-function one can construct fracture driving force curves for each absolute size of interest."--Abstract.
Download or read book A Combined Statistical and Constraint Model for the Ductile Brittle Transition Region written by TL. Anderson and published by . This book was released on 1988 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: A model is presented which uses weakest link statistics to predict the fracture toughness of ferritic steels in the ductile-brittle transition region. This model is different from previous analyses in that it considers large-scale yielding and specimen geometry effects.
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 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 Behaviour of Materials written by Dominique François and published by Springer Science & Business Media. This book was released on 2012-12-24 with total page 688 pages. Available in PDF, EPUB and Kindle. Book excerpt: Designing new structural materials, extending lifetimes and guarding against fracture in service are among the preoccupations of engineers, and to deal with these they need to have command of the mechanics of material behaviour. This ought to reflect in the training of students. In this respect, the first volume of this work deals with elastic, elastoplastic, elastoviscoplastic and viscoelastic behaviours; this second volume continues with fracture mechanics and damage, and with contact mechanics, friction and wear. As in Volume I, the treatment links the active mechanisms on the microscopic scale and the laws of macroscopic behaviour. Chapter I is an introduction to the various damage phenomena. Chapter II gives the essential of fracture mechanics. Chapter III is devoted to brittle fracture, chapter IV to ductile fracture and chapter V to the brittle-ductile transition. Chapter VI is a survey of fatigue damage. Chapter VII is devoted to hydrogen embrittlement and to environment assisted cracking, chapter VIII to creep damage. Chapter IX gives results of contact mechanics and a description of friction and wear mechanisms. Finally, chapter X treats damage in non metallic materials: ceramics, glass, concrete, polymers, wood and composites. The volume includes many explanatory diagrams and illustrations. A third volume will include exercises allowing deeper understanding of the subjects treated in the first two volumes.
Download or read book Fracture Mechanics written by John D. Landes and published by ASTM International. This book was released on 1994 with total page 805 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Constraint based Model for Fracture in the Ductile to brittle Transition Region written by Ted L. Anderson and published by . This book was released on 1984 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fatigue Fracture and High Temperature Design Methods in Pressure Vessels and Piping written by Kenneth K. Yoon and published by . This book was released on 1998 with total page 460 pages. Available in PDF, EPUB and Kindle. Book excerpt: Comprises 49 papers (including two student papers) from the July 1998 Conference. Topics include reactor pressure vessel integrity assessment; piping and elbow and materials, welding and other aspects; elevated temperature design methods; fracture mechanics analysis; and fatigue and fracture analysi
Download or read book Effects of Constraint on Elastic plastic Fracture and Ductile brittle Fracture Transition written by Cheng Yan and published by . This book was released on 1997 with total page 412 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Steady Crack Growth Through Ductile Metals Computational Studies written by James C. Sobotka and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis examines the crack-front response during sustained ductile tearing in structural metals at quasi-static rates using high resolution finite element computations. At load levels approaching the steady-growth regime, well-established computational methods that model material damage break down numerically as vanishingly small load increments produce increasingly large amounts of crack extension. The computational model adopted here determines the deformation history of a steadily advancing crack directly without the need for a priori (transient) analysis that considers blunting of the pre-existing stationary crack and subsequent growth through the associated initial plastic zone. Crack extension occurs at the remotely applied, fixed loading without the need for a local growth criteria. This numerical scheme utilizes a streamline integration technique to determine the elastic-plastic fields, generalized from a two-dimensional to a fully three-dimensional setting and implemented within mixed Matlab/C++/F-90 based software. Modifications of the conventional finite element formulation lead to an efficient procedure -- readily parallelized -- and determine the invariant near-front fields, representative of steady-state growth, on a fixed mesh in a boundary-layer framework. In the small-scale yielding regime, the crack front does not sense the existence of remote boundaries, and computational results retain a strong transferability among various geometric configurations where near-front, plastic deformation remains entirely enclosed by the surrounding linear-elastic material. The global stress intensity factor (KI) and imposed T-stress fully specify displacement constraints along the far-field boundary, and in a three-dimensional setting, the panel thickness reflects the only natural length scale. The initial studies in this work consider steady crack advance within the small-scale yielding context under plane-strain conditions and mode I loading. These analyses focus on steady crack growth within a hydrogen-charged material to explore primary features of the streamline integration methodology while providing new results relevant to hydrogen embrittlement at engineering scales. Ductile crack propagation occurs through a homogeneous, high solubility material characteristic of niobium and through a steel weld in the presence of hydrogen. The constitutive model includes the influence of hydrogen on elastic-plastic regimes of material response at the continuum level, emph{e.g.} hydrogen-induced material softening, based on the hydrogen-enhanced, localized plasticity (HELP) mechanism, and reflects the amount of hydrogen in the material under stress and the intensity of hydrogen-induced softening in the material. Achievements using this two-dimensional framework encouraged further extensions of the research to a fully three-dimensional setting. Subsequent work, and the focal point of this thesis, develops a finite element formulation to investigate key features of the elastic-plastic fields near a steadily advancing crack under three-dimensional, small-scale yielding conditions. The computational model represents a structurally thin component constructed of a material (e.g. Al and Ti alloys) with flow stress and fracture toughness properties that together limit the size of the in-plane plastic zone during steady growth to no more than several multiples of the plate thickness. These studies consider a straight crack front advancing under local and global mode-I loading in a moderately hardening material. The nonsingular T-stress provides a first-order estimate of geometry and loading mode (e.g. tension vs. bending) effects on elastic-plastic, crack front fields. The T-stress has a marked effect on measured crack-growth resistance curves (J-da) -- trends most computational models confirm using a two-dimensional setting. In the first computations of this type to be modeled, the 3D numerical results here demonstrate similarity scaling of the crack front response -- stresses, strains, and displacements -- in terms of two non-dimensional loading parameters. These fields serve as input to key engineering failure models for brittle and ductile crack growth and provide estimates of the apparent fracture toughness linked to changes of the material flow response, geometry, and applied loading. For the first time in the scientific literature, these studies document 3D analyses of steady-state crack growth and represent a key advance in computational analyses of crack extension.
Download or read book Fracture Mechanics written by J. P. Gudas and published by ASTM International. This book was released on 1990 with total page 615 pages. Available in PDF, EPUB and Kindle. Book excerpt: Papers from the 21st National Symposium on Fracture Mechanics, held in Annapolis, Md., June 1988, present new work in elastic-plastic fracture, dynamic fracture, transition fracture in steels, micromechanical aspects of the fracture process, computational mechanics, fracture mechanics testing, and a
