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Author : T Miyata
Publisher :
ISBN 13 :
Total Pages : 14 pages
Book Rating : 4.:/5 (839 download)
Download or read book Probabilistic Analysis of Cleavage Fracture Stress and Fracture Toughness of Steels written by T Miyata and published by . This book was released on 1990 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : C S Wiesner
Publisher : Abington Publishing
ISBN 13 :
Total Pages : 78 pages
Book Rating : 4.3/5 (91 download)
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.
Author : Jianhong Chen
Publisher : Butterworth-Heinemann
ISBN 13 : 0128010517
Total Pages : 488 pages
Book Rating : 4.1/5 (28 download)
Download or read book Micromechanism of Cleavage Fracture of Metals written by Jianhong Chen and published by Butterworth-Heinemann. This book was released on 2014-09-15 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this book the authors focus on the description of the physical nature of cleavage fracture to offer scientists, engineers and students a comprehensive physical model which vividly describes the cleavage microcracking processes operating on the local (microscopic) scale ahead of a defect. The descriptions of the critical event and the criteria for cleavage fracture will instruct readers in how to control the cleavage processes and optimize microstructure to improve fracture toughness of metallic materials. Physical (mechanical) processes of cleavage fracture operating on the local (microscopic) scale, with the focus on the crack nucleation and crack propagation across the particle/grain and grain/grain boundaries Critical event, i.e., the stage of greatest difficulty in forming the microcrack, which controls the cleavage fracture Criteria triggering the cleavage microcracking with incorporation of the actions of macroscopic loading environment into the physical model Effects of microstructure on the cleavage fracture, including the effects of grain size, second phase particles and boundary Comprehensive description of the brittle fracture emerging in TiAl alloys and TiNi memory alloys
Author : Karin Rosahl
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (847 download)
Download or read book The Combined Effects of Residual Stress and Warm Prestressing on Cleavage Fracture in Steels written by Karin Rosahl and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: When the structural integrity of the reactor pressure vessel (RPV) in a pressurised water re- actor (PWR) is analysed, certain types of postulated accidents have to be considered. The conditions during a loss-of-coolant accident (LOCA) resemble a warm prestressing (WPS) sce- nario. Warm prestressing refers to a prior overload sequence which in certain circumstances improves the fracture resistance of a ferritic steel structure. Furthermore, a RPV is a welded structure. The welding process gives rise to residual stresses (RS) that can have a significant influence on the integrity of the RPV. Tensile residual stresses are often regarded as unwanted and detrimental. Previous work has not studied the combined effects of WPS and RS on the fracture behaviour of ferritic steel components. The purpose of this dissertation is to explore the combined effects of WPS and RS by means of robust statistical techniques. To describe the effects of WPS, two models are investigated. A local model using the near crack tip stresses and strains (often called the Beremin model) is usually used to predict the fracture probability of as-received material and can be adapted to include the effects of WPS. However, this requires the use of a detailed finite element analysis. The Chell model, on the other hand, is a deterministic model developed to explain the beneficial effects ofWPS on fracture toughness. Using a Monte Carlo (MC) simulation approach, the Chell model is extended to enable failure probability distributions to be determined. The failure probabilities are compared with both experimental data from the literature and results of an experimental test programme on compact tension specimens. It is found that the MCS approach used in conjunction with the Chell model provides robust and accurate predictions of the failure probability following WPS. To extend the analysis to include residual stress, a novel preloading rig model for introducing a known tensile RS into laboratory fracture specimens is investigated. It is found that the Chell model is to be preferred over the Beremin model. The Chell model provides robust and accurate predictions of the fracture behaviour after WPS, yet its application is straight forward and less time expensive than the Beremin model. The combined effects of WPS and a tensile RS field on the failure probabilities can be analysed by combining the Chell model with the preloading rig model and applying a Monte Carlo simulation approach. Contrary to expectations, it is shown that a tensile RS field can have a significant beneficial effect on the failure distribution after WPS.
Author : Jacques Besson
Publisher : Presses des MINES
ISBN 13 : 2911762738
Total Pages : 121 pages
Book Rating : 4.9/5 (117 download)
Download or read book Local Approach to Fracture written by Jacques Besson and published by Presses des MINES. This book was released on 2006 with total page 121 pages. Available in PDF, EPUB and Kindle. Book excerpt: Improving the structural integrity together with the performance (weight, time to failure,...) of structures requires a persisting effort in the field of mechanics of materials and structures. This can be achieved by a better understanding of the relationships between microscopic mechanisms and the macroscopic material behavior and structural response with respect to damage and fracture. This improvement strategy of materials, structures and assement methods can be described as local approach to fracture. The local approach to fracture is an active research field. Initially developped in the context of steel structures (pressure vessels), its application domain has become wider and now deals with various kinds of materials (metallic alloys, metal matrix composites, polymers, elastomers, concrete) as well as various physical deformation and damage mechanisms (plasticity, creep, fatigue, ductile fracture, brittle fracture, ...). This volume contains the proceedings on an international conference dedicated to these issues.
Author :
Publisher : ASTM International
ISBN 13 :
Total Pages : 156 pages
Book Rating : 4./5 ( download)
Download or read book Properties Related to Fracture Toughness written by and published by ASTM International. This book was released on 1976 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Ivo Dlouhý
Publisher : Springer Science & Business Media
ISBN 13 : 9401006083
Total Pages : 380 pages
Book Rating : 4.4/5 (1 download)
Download or read book Transferability of Fracture Mechanical Characteristics written by Ivo Dlouhý and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 380 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 : Heikki Kotilainen
Publisher :
ISBN 13 :
Total Pages : 140 pages
Book Rating : 4.:/5 (31 download)
Download or read book The Micromechanisms of Cleavage Fracture and Their Relationship to Fracture Toughness in a Bainitic Low Alloy Steel written by Heikki Kotilainen and published by . This book was released on 1980 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Heikki Kotilainen
Publisher :
ISBN 13 : 9789513807320
Total Pages : pages
Book Rating : 4.8/5 (73 download)
Download or read book Determination of the Cleavage Fracture Stress and the Temperature Dependence of the Fracture Toughness of Cr-Mo-V Steel written by Heikki Kotilainen and published by . This book was released on 1979 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 190 pages
Book Rating : 4.:/5 (318 download)
Download or read book Fracture Toughness of High-strength Materials: Theory and Practice written by and published by . This book was released on 1970 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Robert Kulka
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (835 download)
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.
Author : John D. Landes
Publisher : ASTM International
ISBN 13 : 0803119909
Total Pages : 805 pages
Book Rating : 4.8/5 (31 download)
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:
Author : Gerard P. Mercier
Publisher :
ISBN 13 :
Total Pages : 12 pages
Book Rating : 4.:/5 (125 download)
Download or read book Application of the Reference Temperature to the Evaluation of Cleavage Fracture in HSLA-100 Steel written by Gerard P. Mercier and published by . This book was released on 2006 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this study was to evaluate the fracture behavior of HSLA-100 steel at a temperature of -40°C (-40°F). Tests were conducted on three different compositions and two orientations of HSLA-100. HY-100 was also tested to provide a baseline for comparison. Various fracture-related tests were conducted, including traditional test methods, such as the Charpy V-notch and the Dynamic Tear, and more recent methods, such as ductile crack growth initiation (Jic) and the reference temperature. Transition temperatures from the Charpy tests were all very similar, falling around -129°C (-200°F), although the upper shelf Charpy energy for the HY-100 was lower than the HSLA-100 steels. Dynamic tear energies at -40°C for the four steels ranged from 800 to 1800 J. The average reference temperature of all four steels, measured according to ASTM E 1921, was around -151°C (-240°F), with one composition of HSLA-100 coming in as low as -179°C (-290°F) and another as high as -123°C (-190°F). Fracture toughness tests were conducted according to E 1820 at temperatures of -40, -29, and -8°C. These temperatures were more than 83°C above the highest of the reference temperatures, so cleavage fracture was not expected to occur. The HY-100 specimens exhibited an average initiation toughness of 227 kJ/m2 (1296 Ib/in.) and crack growth remained ductile throughout the tests. Even though the HSLA-100 exhibited initiation toughnesses more than twice as high as the HY-100, many of the tests terminated in cleavage fracture after amounts of ductile crack growth varying from 0 to 1.85 mm (0.073 in.). This was an unexpected result based on good Charpy and dynamic tear energies at -40°C, and low reference temperatures. The higher initiation toughness and tearing resistance of HSLA-100 allowed very high stresses to develop in the fracture process zone. As ductile crack growth occurred, the fracture process zone swept through an increasing volume of metal, which increased the probability of cleavage fracture. It is shown that the load required to reach these levels of crack driving force may be above gross section yielding of a typical structure. In this case failure by gross section yielding would occur before fracture. This is demonstrated with the aid of a failure assessment diagram.
Author : B. Farahmand
Publisher :
ISBN 13 :
Total Pages : 14 pages
Book Rating : 4.:/5 (125 download)
Download or read book Probabilistic Fracture Toughness and Fatigue Crack Growth Estimation Resulting From Material Uncertainties written by B. Farahmand and published by . This book was released on 2004 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: A new approach is introduced which can evaluate fracture toughness of aircraft and aerospace alloys by using static parameters that are obtainable from full stress-strain curves available in the MIL-HDBK. With this approach, the energy absorption rates related to the plastic deformation at the crack tip and near crack tip are estimated and used to extend the Griffith theory of brittle fracture to fracture mechanics of ductile metals. An equation has been established that can define the critical crack length as a function of fracture stress. Having fracture stress and critical crack length on hand, the plane strain and plane stress fracture toughness can be calculated by applying the stress intensity factor equation. The calculated fracture toughness for 2219-T8, 2014-T6 aluminums, and Ti-6Al-4V titanium alloy was compared against the experimental test data generated from reliable sources. Excellent agreement between test data and the theory was found. When fracture toughness was calculated by this method, fatigue crack growth curves for the above-mentioned alloys were then generated and compared with test data. The threshold stress intensity factor value, ?Kth, in region I of the da/dN curve, was approximated by establishing a point on the Kitagawa diagram associated with the region of linear elastic fracture mechanics. Results of ?Kth values estimated by this method were in fine agreement with values observed for many materials in the NASGRO database. Two additional points were estimated in region II that enable to establish the Paris region. Probabilistic evaluation of fracture toughness and fatigue crack growth analysis considered a 5 to 10% coefficient of variation of material Kc, and Kth random variables.
Author : A. R. Rosenfield
Publisher :
ISBN 13 :
Total Pages : 14 pages
Book Rating : 4.:/5 (227 download)
Download or read book Micromechanisms and Toughness for Cleavage Fracture of Steel written by A. R. Rosenfield and published by . This book was released on 1986 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: A complete understanding of the fracture mechanisms of steel in the ductile/brittle transition region requires analysis not only of crack initiation, but also of crack propagation. This paper reviews micrographic and fractographic experiments that give insight into both phenomena, and suggests a frame-work through which both may be related. Unstable cleavage crack initiation can occur after some blunting of the original fatigue precrack or after some stable crack growth. In either event, instability appears to be triggered by the fracture of a brittle micro-constituent ahead of the precrack. The large scatter in reported KIc values within the transition region reflects the size distribution and relative scarcity of these trigger particles. While a large number of models have attempted to correlate toughness in the ductile/brittle transition regime to events occurring ahead of the crack tip, surprisingly little attention has been paid to events occurring behind the crack front. Fractographic evidence as well as metallographic sectioning of arrested cracks show that the mechanism of rapid crack propagation by cleavage is affected strongly by partial crack-plane deflection which leaves unbroken ligaments in its wake. The tearing of these ligaments by dimple-rupture is the dominant energy-absorbing mechanism. Etch-pit experiments using an Fe-Si alloy show that the crack-tip stress intensity based on plastic zone size is extremely low. Keywords: HSLA(High Strength Low Alloy), Ductile fracture, Shear fracture, Fracture toughness.
Author : MR. Goldthorpe
Publisher :
ISBN 13 :
Total Pages : 23 pages
Book Rating : 4.:/5 (125 download)
Download or read book Micromechanical Prediction of Fracture Toughness for Pressure Vessel Steel Using a Coupled Model written by MR. Goldthorpe and published by . This book was released on 1999 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: A method of analyzing the ductile to brittle transition region of a ferritic steel using a coupled micromechanical model of ductile damage, stable crack growth and cleavage fracture has been developed to improve the definition of upper shelf behavior for actual structures. Ductile damage is modelled using the Gurson model as modified by Tvergaard, along with a specially developed crack growth user element. The probability of cleavage fracture is predicted by post-processing the finite element results using the Beremin model of cleavage fracture. Predictions are made of ductile tearing and cleavage fracture in test specimen and wide plate configurations of A533B steel for a range of temperatures. The coupled model is capable of predicting transition toughness and transition temperature shifts for different levels of structural constraint. An analytically-based definition of the onset of upper shelf temperature (OUST) is the temperature at which the coupled ductile damage/cleavage fracture model predicts a probability of failure by cleavage fracture of 5%. Estimates of the shift in the OUST due to different levels of in-plane crack tip constraint are made using the elastic T-stress as a measure of constraint. There is potential for using the T-stress as a measure of structural constraint in order to determine shifts in transition temperature for materials with degraded toughness.
Author : V. Bicego
Publisher :
ISBN 13 :
Total Pages : 16 pages
Book Rating : 4.:/5 (125 download)
Download or read book Prediction of Cleavage Fracture Probability for Ferritic Steels in the Transition Region written by V. Bicego and published by . This book was released on 1995 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: A method is described for modelling the stochastic variability of toughness data for ferritic steels in the brittle to ductile transition regime. The present model is based on two ingredients: a weakest link approach using Weibull statistics with a suitable modification to include the effect of ductile tearing, and an accurate expression of the material J-R curve, determined from fractography. The model provides a rationale for the different fracture behaviour of a material over the whole range of temperature, from fully stable J-R behaviour at high temperature down to brittle fracture under LEFM conditions at low temperature.
