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 CONSTRAINT EFFECT IN FRACTURE WHAT IS IT written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The meaning of the phrase 'constraint effect in fracture' has changed in the past two decades from 'contained plasticity' to a broader description of 'dependence of fracture toughness value on geometry of test specimen or structure'. This paper will first elucidate the fundamental mechanics reasons for the apparent 'constraint effects in fracture', followed by outlining a straightforward approach to overcoming this problem in both brittle (elastic) and ductile (elastic-plastic) fracture. It is concluded by discussing the major difference in constraint effect on fracture event in elastic and elastic-plastic materials.

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 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 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 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 Behavior written by J. A. Smith and published by . This book was released on 1997 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Constraint Effects on Fracture Toughness for Circumferentially Oriented Cracks in Reactor Pressure Vessels written by B. R. Bass and published by . This book was released on 1992 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Three Dimensional Variable Constraint Effects in Fracture Initiation written by and published by . This book was released on 1991 with total page 55 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many naturally occurring cracks are three dimensional and cannot be evaluated using numerical techniques derived using two dimensional simplifications. The high stress and strain levels experienced in modern high toughness alloys prior to fracture require means to accurately simulate the nonlinear response of ductile materials in this regime. An accurate constitutive representation must be combined with a fracture criterion which is valid for the high strain regime to achieve accurate computerized simulations of fracture and near fracture behavior. In the current work, nonlinear numerical simulations are performed to determine the global and local responses of two surface cracked plates of HY-100 steel with varying crack propagation and crack depths. Failure is defined by a local fracture criterion using strain energy density. Differences in constraint along the crack perimeter are taken into account by recognizing the stress-strain history dependence of the critical strain energy density. Crack growth patterns determined from the numerical simulations accurately reflect experimental observations.

Download or read book Constraint Effect in Brittle Fracture written by Y-J Chao and published by . This book was released on 1997 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: Variation of apparent fracture toughness under predominantly (elastic) brittle fracture is investigated. Williams' asymptotic series solutions, including higher order terms, are used to characterize the crack tip stress and strain fields for various specimen geometries. Using a fracturing stress or a strain as the material property, it is demonstrated that a fracture event can be quantified by two mechanics parameters, K and A3 for stress-controlled fracture or K and T for strain-controlled fracture. A set of test data that covers a wide range of T and A3 is used to demonstrate the proposed fracture assessment procedure. Constraint-related issues such as size, crack depth, and biaxial stress effect are investigated. The material's failure locus is discussed relative to the ASTM recommended specimen geometries. It is shown that the ASTM in-plane size requirements place a finite-size window on the complete material failure locus. Since real structures may possess constraint levels either higher or lower than the ASTM standard test specimens, structures may fracture at an applied K either higher or lower than KIC. It is demonstrated that KIC determined according to ASTM E 399 and based on a linear elastic solution is not conservative when used to predict the fracture of specimens with low-constraint geometries. This trend is opposite to the corresponding constraint effect in cleavage fracture when the crack tip deformation at fracture is characterized by large-scale yielding.

Download or read book The Effect of Crack tip Region Constraint on Fracture in the Ductile to brittle Transition Region written by T. L. Anderson and published by . This book was released on 1983 with total page 398 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Interpretation of Constraint Effects Under PTS Conditions Based on J Q Fracture Methodology written by DKM Shum and published by . This book was released on 1995 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study explores the possibility of using J-Q-related constraint concepts to describe the nature of the crack-tip loading in a reactor pressure vessel (RPV) under pressurized thermal shock (PTS) conditions. The fracture response of an RPV subjected to three postulated PTS transients that incorporate effects of loading, unloading and reloading (via repressurization) of the crack tip has been examined. Analysis results indicate that minimal loss of constraint relative to conditions of K-dominant small-scale yielding (SSY) is observed during the monotonic-loading phase of the transients. The extent of constraint loss upon reloading is sensitive to the time of repressurization, with minimal (significant) loss of constraint observed for the transient with "early" ("late") repressurization. The nature of the constraint loss, when it occurs, corresponds to a spatially varying hydrostatic field relative to K-dominant SSY conditions. Based on an assumed correlation between loss of crack-tip constraint and fracture toughness, preliminary analysis results indicate that inclusion of constraint effects could provide significant reduction in the value of the calculated conditional probability of vessel failure relative to their exclusion.

Download or read book Geometry and Constraint Effects in Mixed Mode Fracture written by Majid Reza Ayatollahi and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Constraint Effects in Fracture Theory and Applicatons Second Volume written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Biaxial Loading and Shallow flaw Effects on Crack tip Constraint and Fracture Toughness written by B. R. Bass and published by . This book was released on 1994 with total page 61 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effects of Constraint on Upper Shelf Fracture Toughness written by JA. Joyce and published by . This book was released on 1995 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: The upper shelf fracture toughness and tearing resistance of two structural steels, HY-100 and ASTM A533, Gr. B, were determined over a wide range of applied constraint. The constraint conditions were varied by changes in specimen geometry and loading mode. Bend specimens with shallow and deep cracks, compact specimens, and single and double edge notched tension specimens were used in this study. A rotation correction was developed for the single edge notch tension specimen which greatly improved the behavior of the J-R curves determined using this specimen. The experimental results were used to investigate the applicability of the Q and T stress parameters to the correlation of upper shelf initiation toughness, JIc, and tearing resistance, Tmat. The J-Q and J-T stress loci, and corresponding plots of material tearing resistance plotted against Q and T, were developed and compared with the expectations of the O'Dowd and Shih and the Betégon and Hancock analyses. The principle conclusions of this work are that JIc does not appear to be dependent on T stress or Q while the material tearing resistance, Tmat, is dependent on T stress and Q, with the tearing modulus increasing as constraint decreases.