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 Constraint Effects in Fracture written by E. M. Hackett and published by ASTM International. This book was released on 1993 with total page 514 pages. Available in PDF, EPUB and Kindle. Book excerpt: Papers presented at the symposium on [title] held in Indianapolis, Indiana, May 1991, provide a framework for quantifying constraint effects in terms of both continuum mechanics and micro-mechanical modeling approaches. Such a framework is useful in establishing accurate predictions of the fracture
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 3 D Constraint Effects on Models for Transferability of Cleavage Fracture Toughness written by RH. Dodds and published by . This book was released on 1997 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the late 1980s there has been renewed interest and progress in understanding the effects of constraint on transgranular cleavage in ferritic steels. Research efforts to characterize the complex interaction of crack tip separation processes with geometry, loading mode and material flow properties proceed along essentially two major lines of investigation: (1) multi-parameter descriptions of stationary crack-tip fields under large-scale yielding conditions, and (2) rational micromechanics models for the description of cleavage fracture which also reflect the observed scatter in the ductile-to-brittle transition (DBT) region. This article reviews the essential features of a specific example representing each approach: the J-Q extension to correlative fracture mechanics and a local approach based on the Weibull stress. Discussions focus on the growing body of 3-D numerical solutions for common fracture specimens which, in certain cases, prove significantly different from long-established plane-strain results.
Download or read book Constraint Effects on Fracture Toughness written by and published by . This book was released on 2001 with total page 47 pages. Available in PDF, EPUB and Kindle. Book excerpt: The crack growth resistance (toughness) of a structural material depends on the geometry of the crack and the type of loading. These produce differences in the crack tip stress state referred to as the constraint. The stress state controls the deformation required to initiate fracture, and the mechanisms of fracture in steels are profoundly affected by the local constraint. This report describes the crack tip behaviour of 350WT ship steel, based on tests that characterized the fracture toughness of a ship steel plate over a range of constraint conditions. The tests were performed at room temperature on three-point bend bars that were pre-cracked to different crack depths. The mode of fracture was ductile tearing and resistance curves were calculated. Results for initiation toughness and growth resistance are characterized in both the linear elastic and elastic plastic formats. In addition, finite element modelling was used to determine numerically the crack tip stress fields, with special attention to the crack tip blunting behaviour.
Download or read book Influence of Material and Constraint Variation on the Fracture Toughness Behaviour of Steels written by Robert Kulka and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The analysis of fracture toughness test data from standard specimens is often based upon the assumptions of planar crack fronts and homogenous material properties. However, these assumptions do not hold true for all test geometries or real components. The overall objective of this EngD was therefore to develop the methodologies used in fracture assessment of steel components, by incorporating a reduction in the conservatisms inherent in the assessment procedures. These conservatisms are associated with applying a 'lower bound' treatment to steel components, which in reality contain significant variability in effective fracture toughness, due to either material considerations (macroscopic or microstructural), or geometrical considerations including the effect of crack tip constraint. The first method developed allows a comparison of a variation of fracture toughness values throughout a component, to a variation of the localised effective crack driving force. The main feature of this method takes advantage of the nature of the ductile-to-brittle transition regime of fracture toughness, where there is significant scatter. This leads to a probabilistic prediction of the location of fracture initiation, and a less conservative estimate of failure load, used to derive enhanced fracture toughness for the component. The second method calculates less conservative fracture toughness values for steels where there is significant heterogeneity in the dataset. The effects of measurement uncertainty on derived fracture toughness values can be monitored to improve probabilistic estimates of the heterogeneous fracture toughness values. These methods have been developed into predictive software tools, validated against data from the literature. Finite element analysis of various configurations of compact tension and bend specimen, under different constraint conditions, was used to identify fracture mechanics parameters and constraint factors that will be of use in deriving accurate fracture toughness relationships from future testing programmes. The viability of low constraint specimens for accurately characterising increases in fracture toughness has been assessed. These recommendations enhance the relationships and advice suggested in the testing standards and literature. Loss of constraint in thin components can be quantified by a triaxiality parameter, which can be used to predict an increase in fracture toughness through use of a damage model, in this case developed based on a ductility exhaustion approach. This model can be used to predict initiation of ductile fracture in configurations with low constraint, leading to less conservative fracture toughness values, enhancing the guidance in the various defect tolerance assessment procedures.
Download or read book Fracture Mechanics written by Fazil Erdogan and published by ASTM International. This book was released on 1995 with total page 716 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ductile Fracture of Metals written by P. F. Thomason and published by Pergamon. This book was released on 1990 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: An account of the recent developments in research into ductile fracture in metals and alloys. Aspects covered include localized fracture at the root of notches and sharp cracks, and fracture in bulk plastic-deformation processes of the metal and metal forming type. Also discusses various theoretical
Download or read book A Void Growth Model Relating Fracture Toughness and Constraint written by TC. Miller and published by . This book was released on 1994 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: Loading of a metal results in the nucleation of voids around particles. Further deformation results in void growth and coalescence. This work combines mathematical models for void nucleation, growth, and coalescence into a simulation of a ductile fracture to examine the effects of stress triaxiality and constraint loss on ductile fracture.
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 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 Constraint and Statistical Adjustment Models Applied to Transition Fracture Toughness Data written by JD. Landes and published by . This book was released on 1995 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: Constraint and statistical models were applied to fracture toughness data in the transition for steels to determine to what extent either or both are required to deal with size and geometry effects in the transition. A Weibull model was used for statistical adjustment to try to remove size effects from the data. The small-scale yield model was used as a constraint adjustment model to try to do the same. Results showed that no single adjustment worked in every case. To remove size effects a Weibull statistical adjustment taken alone worked best. However, statistical adjustment has not been used to remove geometry effects. To insure accurate transferability of fracture toughness data from one geometry to the next a constraint based model is needed. For this the model based on the J-Q two parameter crack tip stress field characterization was used. Fracture toughness measured on a compact specimen was used to predict the fracture toughness of center cracked and double-edge cracked tension geometries. These predictions were compared with actual data. The results showed that the model was able to predict the fracture behavior of the double-edge cracked geometry but was nonconservative for the center-cracked geometry. These results show that both statistical and constraint models are necessary for dealing with transition fracture toughness data.
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 Fracture Mechanics of Concrete written by Surendra P. Shah and published by John Wiley & Sons. This book was released on 1995-09-28 with total page 588 pages. Available in PDF, EPUB and Kindle. Book excerpt: FRACTURE MECHANICS OF CONCRETE AND ROCK This book offers engineers a unique opportunity to learn, frominternationally recognized leaders in their field, about the latesttheoretical advances in fracture mechanics in concrete, reinforcedconcrete structures, and rock. At the same time, it functions as asuperb, graduate-level introduction to fracture mechanics conceptsand analytical techniques. Reviews, in depth, the basic theory behind fracture mechanics * Covers the application of fracture mechanics to compressionfailure, creep, fatigue, torsion, and other advanced topics * Extremely well researched, applies experimental evidence ofdamage to a wide range of design cases * Supplies all relevant formulas for stress intensity * Covers state-of-the-art linear elastic fracture mechanics (LEFM)techniques for analyzing deformations and cracking * Describes nonlinear fracture mechanics (NLFM) and the latestRILEM modeling techniques for testing nonlinear quasi-brittlematerials * And much more Over the past few years, researchers employing techniques borrowedfrom fracture mechanics have made many groundbreaking discoveriesconcerning the causes and effects of cracking, damage, andfractures of plain and reinforced concrete structures and rock.This, in turn, has resulted in the further development andrefinement of fracture mechanics concepts and tools. Yet, despitethe field's growth and the growing conviction that fracturemechanics is indispensable to an understanding of material andstructural failure, there continues to be a surprising shortage oftextbooks and professional references on the subject. Written by two of the foremost names in the field, FractureMechanics of Concrete fills that gap. The most comprehensive bookever written on the subject, it consolidates the latest theoreticalresearch from around the world in a single reference that can beused by students and professionals alike. Fracture Mechanics of Concrete is divided into two sections. In thefirst, the authors lay the necessary groundwork with an in-depthreview of fundamental principles. In the second section, theauthors vividly demonstrate how fracture mechanics has beensuccessfully applied to failures occurring in a wide array ofdesign cases. Key topics covered in these sections include: * State-of-the-art linear elastic fracture mechanics (LEFM)techniques for analyzing deformations and cracking * Nonlinear fracture mechanics (NLFM) and the latest RILEM modelingtechniques for testing nonlinear quasi-brittle materials * The use of R-Curves to describe cracking and fracture inquasi-brittle materials * The application of fracture mechanics to compression failure,creep, fatigue, torsion, and other advanced topics The most timely, comprehensive, and authoritative book on thesubject currently available, Fracture Mechanics of Concrete is botha complete instructional tool for academics and students instructural and geotechnical engineering courses, and anindispensable working resource for practicing engineers.
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 Methods and Models for Predicting Fatigue Crack Growth Under Random Loading written by and published by ASTM International. This book was released on with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Void Growth Model Relating Fracture Toughness and Constraint written by Timothy Clark Miller and published by . This book was released on 1992 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt:
