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Author: TL. Anderson Publisher: ISBN: Category : Cleavage Languages : en Pages : 12
Book Description
The article utilizes plane strain elastic-plastic finite element analysis and a local criterion for cleavage fracture to establish specimen size requirements for the ductile-brittle transition region. Critical J and CTOD values, relative to the small-scale yielding value, were predicted as a function of specimen size, strain hardening exponent, and a/W. These analyses predict an increase in the apparent toughness with decreasing specimen size due to a loss in crack tip constraint; this effect is particularly pronounced in shallow notched specimens and low hardening materials. For deeply notched bend and compact specimens, the following size requirement must be met for critical J values for cleavage to be size independent: b,B,a>200Jc?Y where b is ligament length, B is thickness, a is crack length, and ?? is flow stress. This criterion is eight times more severe than the size requirements in ASTM E 813-87, but it is less stringent than the requirements of ASTM E 399-83. In order for a CTOD value to be nearly size independent, it must be less than 1/300 times the relevant specimen dimensions.
Author: TL. Anderson Publisher: ISBN: Category : Cleavage Languages : en Pages : 12
Book Description
The article utilizes plane strain elastic-plastic finite element analysis and a local criterion for cleavage fracture to establish specimen size requirements for the ductile-brittle transition region. Critical J and CTOD values, relative to the small-scale yielding value, were predicted as a function of specimen size, strain hardening exponent, and a/W. These analyses predict an increase in the apparent toughness with decreasing specimen size due to a loss in crack tip constraint; this effect is particularly pronounced in shallow notched specimens and low hardening materials. For deeply notched bend and compact specimens, the following size requirement must be met for critical J values for cleavage to be size independent: b,B,a>200Jc?Y where b is ligament length, B is thickness, a is crack length, and ?? is flow stress. This criterion is eight times more severe than the size requirements in ASTM E 813-87, but it is less stringent than the requirements of ASTM E 399-83. In order for a CTOD value to be nearly size independent, it must be less than 1/300 times the relevant specimen dimensions.
Author: M. Nevalainen Publisher: ISBN: Category : Brittle fracture Languages : en Pages : 15
Book Description
As part of a test program to introduce small specimen test techniques, fracture toughness tests have been performed with 20% side-grooved small (10•10•55 mm) and "ultra-small" (3•4•27, 5•5•27 and 5•10•55 mm) specimens. The objectives were to evaluate the measuring capacity of small specimens and to verify the applicability of the statistical cleavage fracture model of VTT for such test data. Two pressure vessel steels were used in the study. Most of the tests were performed in the transition range and ended at cleavage fracture, but some tests were also conducted in the temperature range of ductile tearing. According to the measured data, the 100 MPa?m reference temperatures (T0), determined even with 3•4 mm specimens, are in good agreement with those of the larger specimens. The statistical specimen size correction only was applied in the analyses, i.e., without any consideration of specimen constraint. The measurements made in the ductile range indicate that practically similar fracture resistance curves can be obtained with the 5•10 mm and larger specimens up to the J-level of 500 kN/m. Also, correlations have been developed, by applying a fracture mechanics approach, for estimating the Charpy transition temperatures of ferritic structural steels from small specimen test data. The correlations were verified by analyzing test data produced with Charpy (ISO-V) and KLST-type subsize specimens (3•4•27 mm). Two energy criterion combinations were applied for determining transition temperatures, i.e., the criteria based on the area of the specimen ligament, being in accordance with the master curve definition, and those derived from an empirical mean relationship found between the upper-shelf energies measured with ISO-V and KLST specimens for various steels. The results show that both of these criteria can be used to give a satisfactory correlation between the transition temperatures and that the standard deviations of the correlations are approximately equal, i.e., around 15°C. A method is proposed for estimating the Charpy upper-shelf energy from subsize specimen data.
Author: Pranav H. Darji Publisher: BoD – Books on Demand ISBN: 1789231582 Category : Science Languages : en Pages : 288
Book Description
This book contains two sections: Chapters 1-7 deal with contact mechanics, and Chapters 8-13 deal with fracture mechanics. The different contributions of this book will cover the various advanced topics of research. It provides some needed background with respect to contact mechanics, fracture mechanics and the use of finite element methods in both. All the covered chapters of this book are of a theoretical and applied nature, suitable for the researchers of engineering, physics, applied mathematics and mechanics with an interest in computer simulation of contact and fracture problems.
Author: John E. Srawley Publisher: ISBN: Category : Fracture mechanics Languages : en Pages : 80
Book Description
A comprehensive survey is presented of current methods of fracture toughness testing that are based on linear elastic fracture mechanics. General principles are discussed in relation to the basic two-dimensional crack stress field model and in relation to real three-dimensional specimens. The designs and necessary dimensions of specimens for mixed mode and opening mode (plane strain) crack toughness measurement are considered in detail. Methods of test instrumentation and procedure are described. Expressions for the calculation of crack toughness values are given for the common types of specimens.
Author: J. Heerens Publisher: ISBN: Category : Cleavage Languages : en Pages : 15
Book Description
A method is proposed for determining a lower-bound fracture toughness value from the result of a single test in the transition region for steels. The method is based on the size criterion of Iwadate et al. for determining the number of tests needed to characterize toughness adequately at a given condition and a Weibull statistical distribution. The method was evaluated by determining a lower-bound toughness value for 68 sets of data, which include over 700 fracture toughness values in the transition. The lower-bound estimate was judged to be conservative if all of the lower-bound estimates were lower than the lowest toughness value in the set. The method was conservative for more than 60% of the data sets and for more than 95% of the individual toughness values. In addition, the method was evaluated by comparing it with 4 methods that used multiple specimens for determining a lower-bound toughness. The single-specimen method gave essentially the same lower-bound estimates as the other multiple-specimen methods.
Author: E. van Walle Publisher: ISBN: Category : Loss of constraint Languages : en Pages : 15
Book Description
The objective of the study presented here is the validation of direct fracture toughness measurements using two small-size geometries, which can be obtained from machining broken Charpy-V specimens: • the miniaturized precracked Charpy-V specimen (MPCCv); • the miniaturized Cracked Round Bar (MCRB). Fracture toughness results have been obtained in the ductile-to-brittle transition regime for two well-characterized reactor pressure vessel steels, and compared using the Master Curve analysis to reference data measured using bigger samples of the more conventional C(T) geometry.
Author: K. Wallin Publisher: ISBN: Category : Cleavage fracture initiation Languages : en Pages : 25
Book Description
The effect of specimen thickness, side grooving, large-scale yielding of the ligament, and ductile tearing upon the probability of cleavage fracture initiation is examined within the framework of a general statistical model for cleavage fracture initiation. First, a derivation of the statistical model is presented, and then the model is used to explain the effects of different factors affecting the cleavage fracture probability. As a result, a specimen size requirement for elastic-plastic cleavage fracture toughness testing with bend-type specimens is obtained. Additionally, a simple correction function to validate invalid test results with insufficient ligament size and prior ductile tearing is presented.
Author: Gyoujin Cho Publisher: Elsevier ISBN: 0857093223 Category : Technology & Engineering Languages : en Pages : 309
Book Description
Within the last decade there has been an increasing awareness that use of standards deeply notched fracture mechanics test specimens can result in substantial over-or-under-assessments of the real fracture toughness associated with shallow surface cracks.
Author: Ivo Dlouhý Publisher: Springer Science & Business Media ISBN: 9401006083 Category : Science Languages : en Pages : 380
Book Description
Five laboratories from France, Hungary and the Czech Republic have solved a Project supported fmancially by NATO within the Science for Peace Program (under Nr. 972655) for three years. The project, titled Fracture ResistanceofSteelsfor Containers of Spent Nuclear Fuel, was focused (i) on the generation of data needed for the qualification procedure of a new container introduced by Skoda Nuclear Machinery and (ii) on a number of topics of scientific nature associated with the interesting field of transferability of fracture mechanical data-, It has been found during numerous conference presentations of project results that the knowledge developed within the project would be more attractive when published in a more comprehensive form. This was the reason why the final project workshop was arranged as a meeting of project collaborators and contributing invited experts working in very similar field. The main scope of the final project workshop, titled Transferability of Fracture Mechanical Data and held in Brno from 5 to 6 November 200I, was to bring together project collaborators with a number of invited international experts, both covering the spectrum of topics solved within the project and reviewing the project results in the presence ofthese specialists. A totalof34 colleagues from 7 European countries and the USA participated in the workshop.
Author: TL. Anderson
Author: TL. Anderson
Author: M. Nevalainen
Author: Pranav H. Darji
Author: John E. Srawley
Author: J. Heerens
Author: E. van Walle
Author: K. Wallin
Author: Gyoujin Cho
Author: United States. Ship Structure Committee
Author: Ivo Dlouhý