Academic literature on the topic 'Crack growth'
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Journal articles on the topic "Crack growth"
1
Kamaya, Masayuki. "Evaluation of Fatigue Crack Growth of Interacting Surface Cracks." Advanced Materials Research 33-37 (March 2008): 187–98. http://dx.doi.org/10.4028/www.scientific.net/amr.33-37.187.
Full textAbstract:
Since mechanical interaction between multiple cracks affects the rate of crack growth due to fatigue and stress corrosion cracking, it is important to consider its influence when predicting growth. In this study, a procedure predicting the growth of interacting surface cracks was developed. First, using the results of fatigue crack growth tests performed in a previous study, the transient growth behavior during coalescence and growth under interaction was evaluated based on area of crack face. It was shown that the area is a representative parameter of the growth of interacting surface cracks as well as independent cracks. The growth in area showed good correlation with the crack driving force defined using size of area. Then, in order to investigate the relationship between growth of interacting cracks and their relative spacing, crack growth simulations were carried out. The body force method was used to evaluate the change in stress intensity factors (SIF) during crack growth under interaction, and the simulation could reproduce the crack configurations obtained in the fatigue crack growth test. SIF of an interacting crack tip converges to that of a coalesced crack as the distance between cracks decreases. It was concluded that when the distance between cracks is small enough, the cracks can be replaced with a semi-elliptical crack of the same area of crack face for a growth evaluation. The threshold offset distance for the replacement was suggested to be less than 0.1Rx, where Rx is the span length of two cracks on the surface.
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Yoda, M. "Subcritical Crack Growth Characteristics on Compact Type Specimens and Indentation Cracks in Glass." Journal of Engineering Materials and Technology 111, no. 4 (October 1, 1989): 399–403. http://dx.doi.org/10.1115/1.3226486.
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For the purpose of comparing crack growth characteristics on small indentation cracks with those for long cracks, subcritical crack growth data on soda-lime glass were obtained using the compact type (CT) specimens with long cracks and the indentation cracks. It was found that there is apparently a small crack effect in the as-indented cracks which increases crack growth. However, the annealed indentation crack shows the same trend of crack growth as that for the CT specimens. A residual stress effect can be used to explain this anomalous growth behavior of the as-indented cracks.
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Jin, Huijin, Bing Cui, and Ling Mao. "Fatigue Growth Behaviour of Two Interacting Cracks with Different Crack Offset." Materials 12, no. 21 (October 28, 2019): 3526. http://dx.doi.org/10.3390/ma12213526.
Full textAbstract:
Under cyclic fatigue load, multiple cracks would significantly deteriorate the service life of the components with respect to the case of a single crack owing to the crack interaction. The present study aims to explore the effect of crack interaction on the fatigue growth behaviour of samples with different crack offset. In this study, fatigue crack growth tests were performed for samples containing a single crack and non-collinear cracks of different crack offset in an aluminum–lithium alloy. It was shown that the two facing non-collinear cracks changed their growth direction when the cracks were overlapped, resulting in load mode transfers from mode I to I + II mixed mode. Then, the interaction behaviour was studied by establishing the finite element models to calculate the stress intensity factor K of samples with different crack offset. The results indicated that the K decreased, largely owing to the shielding effect as the two cracks overlapped, leading to retardation of crack growth in the position of overlap, especially for the specimens with a small crack offset. It was also shown that the interaction effect could change from positive to negative during the process of the multiple cracks’ growth, thus leading to the acceleration or deceleration of crack growth rates, suggesting that the influence of interaction on cracks’ growth behaviour could vary with the different stages of crack growth.
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McEvily, A. J. "Recent Advances in Fatigue Crack Growth." Key Engineering Materials 510-511 (May 2012): 15–21. http://dx.doi.org/10.4028/www.scientific.net/kem.510-511.15.
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Many of the recent advances in the understanding of the fatigue crack growth process have resulted from an improved realization of the importance of fatigue crack closure in the crack growth process. Two basic crack closure processes have been identified. One of which is known as plasticity-induced fatigue crack closure (PIFCC), and the other is roughness-induced fatigue crack closure (RIFCC). Both forms occur in all alloys, but PIFCC is a surface-related process which is dominant in aluminum alloys such as 2024-T3, whereas RIFCC is dominant in most steels and titanium alloys. A proposed basic equation governing fatigue crack growth is (1) where where Kmax is the maximum stress intensity factor in a loading cycle and Kop is the stress intensity factor at the crack opening level. is the range of the stress intensity factor at the threshold level which is taken to correspond to a crack growth rate of 10-11 m/cycle. The material constant A has units of (MPa)-2, and therefore Eq. 1 is dimensionally correct. Eq.1 has been successfully used in the analysis of both long and short cracks, but in the latter case modification is needed to account for elastic-plastic behavior, the development of crack closure, and the Kitagawa effect which shows that the fatigue strength rather than the threshold level is the controlling factor determining the rate of fatigue crack growth in the very short fatigue crack growth range. Eq. 1 is used to show that The non-propagating cracks observed by Frost and Dugdale resulted from crack closure. The behavior of cracks as short as 10 microns in length can be predicted. Fatigue notch sensitivity is related to crack closure. Very high cycle fatigue (VHCF) behavior is also associated with fatigue crack closure.
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Han, Zhichao, Caifu Qian, and Huifang Li. "Investigation of the Enhancement Interactions between Double Parallel Cracks on Fatigue Growth Behaviors." Materials 13, no. 13 (July 1, 2020): 2952. http://dx.doi.org/10.3390/ma13132952.
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In this paper, interactions of double parallel cracks were studied by performing experiments and numerical simulations. Fatigue crack propagation tests were carried out to measure crack growth rates in the specimens with double parallel cracks or a single crack. Finite element method was adopted to calculate stress intensity factors at the crack tips. Results show that the double parallel cracks at different positions present a shielding effect or enhancement effect on crack growth rates and stress intensity factors. When the double parallel cracks are offset, crack interactions mostly behave as enhancement effects. Empirical formulas were obtained to calculate the stress intensity factor at the “dangerous” crack tip of the double parallel cracks. By modifying the material parameters in Paris equation of the single crack, the double parallel cracks are simplified into a single crack with the same crack growth rates.
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Han, Zhichao, Caifu Qian, and Huifang Li. "Study of the Shielding Interactions between Double Cracks on Crack Growth Behaviors under Fatigue Loading." Metals 10, no. 2 (January 31, 2020): 202. http://dx.doi.org/10.3390/met10020202.
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In this paper, the interactions between double cracks with a co-bisector-line were investigated theoretically and experimentally. Fatigue crack growth tests of specimens with a single crack or double cracks were carried out to measure the crack growth rates, and finite element calculations were performed to obtain the stress intensity factors at crack tips. It was found that when the double cracks are in co-bisector-line, they present shielding interactions which reduce the stress intensity factors at crack tips as well as the crack growth rates. By modifying the stress intensity factors and the Paris equation considering the shielding interactions, a new simplification method was proposed to simplify the double cracks into a single crack with the same crack growth rates.
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Prakash, R. V. "Fatigue crack growth at stress concentrators under spectrum loading." Journal of Strain Analysis for Engineering Design 40, no. 2 (February 1, 2005): 117–27. http://dx.doi.org/10.1243/030932405x7764.
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Fatigue cracks initiate at stress raisers such as notches, discontinuities, and surface defects. Many of the field failures that indicate the presence of a fatigue crack at failure can be traced to crack initiation from one or more crack initiation sites and merger of cracks over a period of service. Substantial service life is spent in the growth of small cracks from an initial size of few micrometres before they coalesce and grow to critical dimensions that cause fracture. This paper summarizes research that was carried out in order to understand the kinetics of crack growth of small cracks at notches under simulated FALSTAFF service loading. This paper also presents a method used to understand crack growth kinetics in a pin-loaded lug joint through a crack-front-mapping technique.
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Kutsenko, O. G., L. V. Kharytonova, and R. M. Krush. "Regularities of flat cracks growth in plates." Bulletin of Taras Shevchenko National University of Kyiv. Series: Physics and Mathematics, no. 2 (2023): 124–27. http://dx.doi.org/10.17721/1812-5409.2023/2.19.
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The general regularities of the influence of the geometric parameters of a fatigue crack on the direction of its growth in elastic plates under uniaxial tension were studied. Straight cracks, cracks in the form of a full cosine period, cracks in the form of a circle arc and kinked cracks were considered in a broad range of their geometric parameters variations. The direction of crack growth was determined in accordance with the criteria of maximum tangential (circumferential) stresses. The stress intensity factor of mode I and mode II of fracture were determined numerically using the finite element method. The obtained results made it possible to conclude that in the case of smooth crack faces, the direction of its growth primarily depends on the angle between the tangent at the crack tip and the direction of tension. It was established that the presence of a corner point of the faces near crack tip significantly affects the direction of crack growth in the case of small angles, between the tangent and the direction of tension. For such cases, numerically, it was not possible to achieve a continuous limiting transition in the results when the corner point approaches the tip. This circumstance complicates the issue of choosing the size of the initial crack growth step.
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Takahashi, Akiyuki, Ayaka Suzuki, and Masanori Kikuchi. "Fatigue Crack Growth Simulation Using S-Version FEM: Application to Interacting Subsurface Cracks." Key Engineering Materials 741 (June 2017): 82–87. http://dx.doi.org/10.4028/www.scientific.net/kem.741.82.
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In this paper, fatigue crack growth simulation of interacting subsurface cracks using the s-version finite element method (SFEM) is presented. In order to evaluate the accuracy and reliability of the proximity rules published by the ASME, during the fatigue crack growth simulations, the subsurface cracks are approximated to either a single elliptical crack or semi-elliptical surface crack in accordance with the proximity rules. Then, the proximity rules are slightly modified for improving the accuracy and reliability. The results of crack depth evolution calculated by the SFEM with the use of the new proximity rules suggest that the approximation to deep cracks drastically improves the accuracy of the fatigue crack growth evaluation. Thus, the approximation to deep cracks must be a promising approach for having better evaluation of fatigue crack growth of subsurface cracks.
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Lukaszewicz, Mikolaj, Shen Gi Zhou, and Alan Turnbull. "Novel Concepts on the Growth of Corrosion Fatigue Small and Short Cracks." Solid State Phenomena 227 (January 2015): 3–6. http://dx.doi.org/10.4028/www.scientific.net/ssp.227.3.
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Corrosion fatigue small, short and long crack growth rates have been determined for a 12Cr steam turbine steel in aerated 300 ppb Cl- + 300 ppb SO42- solution and in air at 90 °C. The crack growth rate for short and long cracks was monitored by direct current potential drop (DCPD) and for the small cracks by combining high resolution optical microscopy and DCPD. Comparison of the fatigue growth rate demonstrated that in solution the short crack growth rate was remarkably enhanced in comparison to long cracks, when the crack size is smaller than 250 μm. This enhancement was attributed to the electrochemical crack size effect associated with greater anodic polarisation of the short crack in such low conductivity solution. However, such enhanced growth was not observed for small cracks, which was rationalised on the basis of additional contribution of current from the pit limiting crack-tip polarisation.
Dissertations / Theses on the topic "Crack growth"
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McFadyen, Neil B. (Neil Barry) Carleton University Dissertation Engineering Mechanical. "Fatigue crack growth in semi-elliptical surface cracks." Ottawa, 1987.
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CORBANI, SILVIA. "CRACK GROWTH WITH PARTIAL BENDING-INDUCED CRACK CLOSURE." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2012. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=23847@1.
Full textAbstract:
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Neste trabalho são investigadas experimentalmente e numericamente as mudanças de geometria em trincas inicialmente passantes submetidas a carregamento remoto de flexão pura induzindo fechamento parcial das faces da trinca. Esse crescimento de trinca pode ocorrer numa variedade de estruturas com defeitos pré-existentes, tais como fuselagens de aviões, cascos de navios, vasos de pressões e pontes metálicas. O carregamento de flexão pura ocasiona regiões de tração e compressão na frente da trinca. É inquestionável que parte das faces da trinca sob compressão fecha independentemente de qualquer mecanismo de fechamento; e outra parte das faces da trinca, por outro lado, sob tração cresce mudando gradualmente de geometria. Após realizar ensaios em corpos-de-prova de aço ASTM A-36, foi observado que tais carregamentos geram uma quina na frente da trinca, que é a transição de uma geometria parcialmente passante e um trecho remanescente da geometria inicial. Para entender a distribuição do fator de intensidade de tensão em tais frentes de trinca, suas geometrias foram reproduzidas em um modelador tridimensional de mecânica da fratura linear elástica, o FRANC3D, acoplado a um programa de análise de elementos finitos (ABAQUS). Com este sistema acoplado, foram executadas análises considerando efeitos não lineares causados pelo contato das faces da trinca sob compressão. Verificou-se a necessidade de propor metodologias para tratamento dos resultados numéricos na quina, obtendo-se predições eficientes das mudanças na geometria da trinca. Contudo, a estimativa de vida, quando se compara taxas de crescimento da trinca obtidas em um corpo-de-prova sob tração cíclica e as taxas em um corpo-de-prova sob flexão com fechamento parcial da trinca, foi melhor reproduzida usando um fator de correção de fechamento da trinca. Adicionalmente, uma série de expressões empíricas normalizadas para geometrias da trinca e fatores de intensidade de tensão são propostas.
This work investigates experimentally and numerically how the front of initially through edge cracks in plate changes after they pass to be remotely fatigue loaded under pure bending to induce partial closure of the crack faces. This type of crack growth problem can occur in a variety of structures with preexisting defects, such as aircraft fuselages, ship hulls, pressure vessels components, and steel bridges. The bending loads induce tension and compression regions along the crack front, with the part of the crack faces that work under compression undoubtedly closed by the load, independently of any other closure mechanism. The part of the crack faces that work under tension; on the other hand, crack grows by fatigue gradually changing its shape. After performing tests on ASTM A36 steel specimens, it was observed that the bending load induces a kink on the crack front, in the transition between the part through crack created on the tension side and initial crack geometry. To understand the distribution of the stress intensity factor along such crack fronts, the measured crack shapes were reproduced in a three-dimensional fracture mechanics modeler (FRANC3D) coupled to a finite element analysis program (ABAQUS). With this coupled system, linear elastic stress analysis simulations were performed considering the nonlinear effects caused by the crack face contact in the compressed region. In particular, methods had to be proposed to treat numerical noise around the kink. The proposed methodology efficiently predicts the observed crack front shape changes; although the observed fatigue lives were better reproduced using a crackclosure correction factor when compared to crack growth data obtained from standard compact tension specimens. In addition, a series of normalized empiric expressions for both crack front shapes and stress intensity factors are proposed.
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Hejman, Ulf. "On initiation of chemically assisted crack growth and crack propagation paths of branching cracks in polycarbonate." Licentiate thesis, Malmö högskola, Teknik och samhälle, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-7790.
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Stress corrosion, SC, in some cases gives rise to stress corrosion cracking, SCC, which differs from purely stress intensity driven cracks in many aspects. They initiate and grow under the influence of an aggressive environment in a stressed substrate. They grow at low load and may branch. The phenomenon of SCC is very complex, both the initiation phase and crack extension itself of SCC is seemingly associated with arbitrariness due to the many unknown factors controlling the process. Such factors could be concentration of species in the environment, stress, stress concentration, electrical conditions, mass transport, and so on.In the present thesis, chemically assisted crack initiation and growth is studied with special focus on the initiation and branching of cracks. Polycarbonate plates are used as substrates subjected to an acetone environment. Experimental procedures for examining initiation and branching in polycarbonate are presented. An optical microscope is employed to study the substrate.The attack at initiation is quantified from pits found on the surface, and pits that act as origin for cracks is identified and the distribution is analysed. A growth criterion for surface cracks is formulated from the observations, and it is used to numerically simulate crack growth. The cracks are seen to coalesce, and this phenomenon is studied in detail. Branching sites of cracks growing in the bulk of polycarbonate are inspected at the sample surface. It is found that the total width of the crack branches are approximately the same as the width of the original crack. Also, angles of the branches are studied. Further, for comparison the crack growth in the bulk is simulated using a moving boundary problem based algorithm and similar behaviour of crack branching is found.
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Ahmad, Haider Yousif. "Fatigue crack growth at notches." Thesis, University of Sheffield, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360410.
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Shin, C. S. "Crack growth at stress concentrations." Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355680.
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Sheu, Yih-Chyun. "Dynamic elastic-viscoplastic crack growth /." The Ohio State University, 1988. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487587604133479.
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Patel, Surendra Kumar. "Experimental And Numerical Studies On Fatigue Crack Growth Of Single And Interacting Multiple Surface Cracks." Thesis, Indian Institute of Science, 2000. https://etd.iisc.ac.in/handle/2005/276.
Full textAbstract:
Design based on damage tolerance concepts has become mandatory in high technology structures. These concepts are also essential for evaluating life extension of aged structures which are in service beyond originally stipulated life. Fracture analysis of such structures in the presence of single or multiple three-dimensional flaws is essential for this approach. Surface cracks are the most commonly occurring flaws and development of accurate methods of analysis for such cracks is essential for structural integrity evaluation of newly designed or aged structures. The crack fronts of these surface flaws are usually approximated mathematically to be of either part-elliptical or part-circular in geometry. In this thesis, some of the issues related to fatigue crack growth of single and multiple surface cracks are studied in detail. Here emphasis is given to the development of simple and accurate post-processing techniques to estimate stress intensity factors for surface cracks, development and/or implementation of simple numerical methods to simulate three-dimensional single and multiple cracks in fatigue and their experimental verification.
Modified virtual crack closure integral (MVCCI) technique for estimation of strain energy release rates has been improved (chapter II) to deal with curved crack front and unequal elements across the crack front. The accuracy of this method is evaluated and presented in this chapter for certain benchmark surface flaw problems. The improved MVCCI is used in the investigation of interaction between multiple surface cracks in three-dimensional solids. The interaction effects are studied for both interacting and coalescing phases as observed to occur in the growth of multiple surface cracks. Extensive numerical work is performed to study the effects of various parameters such as aspect ratio, thickness ratio, interspacing on the interaction factors. These solutions are used in formulating empirical equations to estimate interaction factors. This facilitated the development of a simple semi-analytical method to study fatigue crack growth of multiple cracks.
The growth of surface cracks under fatigue loading in the finite width specimens of an aero-engine superalloy has been studied experimentally (presented in chapter III). Four configurations for single semi-elliptical cracks are considered. Fatigue crack growth is simulated by two models viz. two degrees of freedom and "multi degrees of freedom with ellipse fit'. These models are sometimes referred to as semi-analytical models as the crack growth is predicted by numerical integration combining Paris equation with an empirical form of stress intensity factor solution. In order to use two degrees of freedom model for fatigue crack growth prediction of semi-elliptical cracks, empirical solution for the Ml range of geometric parameters for stress intensity factor is required for the considered
configurations. The available Newman-Raju solution is useful for this purpose within a limited range of surface crack length to width (c/W) of the specimen. Based on the present finite element results, the empirical equations are developed for extended values of c/W. It is well understood that the fatigue prediction for two-dimensional crack can be improved by inclusion of crack closure effects. Usually, in semi-analytical models for growth of surface cracks under fatigue loading, the crack closure is included as a ratio of crack closure factor at surface and depth locations of semi-elliptical crack. In the present work, this ratio for the considered material of specimens is obtained by an experimental study. The difference in characteristics of preferred propagation path between semi-elliptical crack in a finite width plate and a wide plate is clearly brought out.
Current crack growth predictions for most of the structures are based on the presence of only a single crack. However, in structures several cracks may initiate simultaneously within a stress critical zone and may interact depending upon their geometry, spatial location, structure geometry and mode of loading. In this work various configurations of twin semi-elliptical cracks have been studied by experiments. The beachmarks created on the specimens during experiments are used in the investigation of crack shape progression during fatigue. A three degrees of freedom crack growth model for interacting and coalescing cracks has been proposed. The experimentally determined crack shape and lives have been compared with the corresponding values from numerical simulation.
The correlation of experimental results with numerical predictions was carried out through improved MVCCI for eight-noded brick elements. This has worked well in the configurations analysed. However, it is known in literature that there are benefits of using 20-noded singular elements. There could be special situations where the regular elements could fail, and singular elements could be essential. For this purpose, further development of MVCCI were carried out using 20-noded quarter-point elements (presented in chapter IV). Also a novel technique of decomposed crack closure integral (DCCI) was developed (presented in chapter V) for both regular and singular elements to represent the variation of MVCCI more accurately along the crack front.
It is well known that quarter-point elements at crack front produce the required singularity at the crack tip and give accurate stress distribution with fewer degrees of freedom than conventional elements. Thus to develop more efficient post-processing tools, the MVCCI expressions are formulated for 20-noded singular quarter-point element for various assumptions regarding stress and displacement distributions in the elements across the crack front. A comprehensive study is presented (chapter IV) on MVCCI for 20-noded singular brick element including various simplified expressions for three-dimensional part-through cracks in pure and mixed-mode state of deformation of fracture. The developed MVCCI expressions are also valid for 15-noded quarter-point Penta elements. The reduction in model size can further be obtained if 12-noded three-dimensional singular element is employed at the crack front and eight-noded elements are used away from the crack front. The MVCCI expressions are also developed for 12-noded singular element and their accuracy is evaluated by numerical solutions.
Presently, MVCCI, estimates the average stress intensity factor at the center of each element along the crack front. In this thesis, a Decomposed Crack Closure Integral (DCCI) is formulated to represent an assumed variation of stress intensity factor along the crack front in each element. The DCCI is formulated for 8-noded brick, 20-noded conventional brick and 20-noded singular brick elements. The numerical examples presented here deal with three-dimensional problems of patch repair technology and part-through cracks. The technique showed a major advantage for the patch repair problems where SIF variations along the crack front are of significance and large mesh sizes are computationally expensive. This along with MVCCI for 12-noded and 20-noded singular elements formed a part of the work on development of accurate and effective post-processing tools.
It is expected that the present work will be helpful in damage tolerance design and assessment of aerospace structures and the experimental work performed as a part of this thesis will enhance confidence in the damage tolerance analysis.
The thesis is concluded in chapter VI presenting the contributions of this thesis and projecting future lines of work possible in this area.
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Patel, Surendra Kumar. "Experimental And Numerical Studies On Fatigue Crack Growth Of Single And Interacting Multiple Surface Cracks." Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/276.
Full textAbstract:
Design based on damage tolerance concepts has become mandatory in high technology structures. These concepts are also essential for evaluating life extension of aged structures which are in service beyond originally stipulated life. Fracture analysis of such structures in the presence of single or multiple three-dimensional flaws is essential for this approach. Surface cracks are the most commonly occurring flaws and development of accurate methods of analysis for such cracks is essential for structural integrity evaluation of newly designed or aged structures. The crack fronts of these surface flaws are usually approximated mathematically to be of either part-elliptical or part-circular in geometry. In this thesis, some of the issues related to fatigue crack growth of single and multiple surface cracks are studied in detail. Here emphasis is given to the development of simple and accurate post-processing techniques to estimate stress intensity factors for surface cracks, development and/or implementation of simple numerical methods to simulate three-dimensional single and multiple cracks in fatigue and their experimental verification.
Modified virtual crack closure integral (MVCCI) technique for estimation of strain energy release rates has been improved (chapter II) to deal with curved crack front and unequal elements across the crack front. The accuracy of this method is evaluated and presented in this chapter for certain benchmark surface flaw problems. The improved MVCCI is used in the investigation of interaction between multiple surface cracks in three-dimensional solids. The interaction effects are studied for both interacting and coalescing phases as observed to occur in the growth of multiple surface cracks. Extensive numerical work is performed to study the effects of various parameters such as aspect ratio, thickness ratio, interspacing on the interaction factors. These solutions are used in formulating empirical equations to estimate interaction factors. This facilitated the development of a simple semi-analytical method to study fatigue crack growth of multiple cracks.
The growth of surface cracks under fatigue loading in the finite width specimens of an aero-engine superalloy has been studied experimentally (presented in chapter III). Four configurations for single semi-elliptical cracks are considered. Fatigue crack growth is simulated by two models viz. two degrees of freedom and "multi degrees of freedom with ellipse fit'. These models are sometimes referred to as semi-analytical models as the crack growth is predicted by numerical integration combining Paris equation with an empirical form of stress intensity factor solution. In order to use two degrees of freedom model for fatigue crack growth prediction of semi-elliptical cracks, empirical solution for the Ml range of geometric parameters for stress intensity factor is required for the considered
configurations. The available Newman-Raju solution is useful for this purpose within a limited range of surface crack length to width (c/W) of the specimen. Based on the present finite element results, the empirical equations are developed for extended values of c/W. It is well understood that the fatigue prediction for two-dimensional crack can be improved by inclusion of crack closure effects. Usually, in semi-analytical models for growth of surface cracks under fatigue loading, the crack closure is included as a ratio of crack closure factor at surface and depth locations of semi-elliptical crack. In the present work, this ratio for the considered material of specimens is obtained by an experimental study. The difference in characteristics of preferred propagation path between semi-elliptical crack in a finite width plate and a wide plate is clearly brought out.
Current crack growth predictions for most of the structures are based on the presence of only a single crack. However, in structures several cracks may initiate simultaneously within a stress critical zone and may interact depending upon their geometry, spatial location, structure geometry and mode of loading. In this work various configurations of twin semi-elliptical cracks have been studied by experiments. The beachmarks created on the specimens during experiments are used in the investigation of crack shape progression during fatigue. A three degrees of freedom crack growth model for interacting and coalescing cracks has been proposed. The experimentally determined crack shape and lives have been compared with the corresponding values from numerical simulation.
The correlation of experimental results with numerical predictions was carried out through improved MVCCI for eight-noded brick elements. This has worked well in the configurations analysed. However, it is known in literature that there are benefits of using 20-noded singular elements. There could be special situations where the regular elements could fail, and singular elements could be essential. For this purpose, further development of MVCCI were carried out using 20-noded quarter-point elements (presented in chapter IV). Also a novel technique of decomposed crack closure integral (DCCI) was developed (presented in chapter V) for both regular and singular elements to represent the variation of MVCCI more accurately along the crack front.
It is well known that quarter-point elements at crack front produce the required singularity at the crack tip and give accurate stress distribution with fewer degrees of freedom than conventional elements. Thus to develop more efficient post-processing tools, the MVCCI expressions are formulated for 20-noded singular quarter-point element for various assumptions regarding stress and displacement distributions in the elements across the crack front. A comprehensive study is presented (chapter IV) on MVCCI for 20-noded singular brick element including various simplified expressions for three-dimensional part-through cracks in pure and mixed-mode state of deformation of fracture. The developed MVCCI expressions are also valid for 15-noded quarter-point Penta elements. The reduction in model size can further be obtained if 12-noded three-dimensional singular element is employed at the crack front and eight-noded elements are used away from the crack front. The MVCCI expressions are also developed for 12-noded singular element and their accuracy is evaluated by numerical solutions.
Presently, MVCCI, estimates the average stress intensity factor at the center of each element along the crack front. In this thesis, a Decomposed Crack Closure Integral (DCCI) is formulated to represent an assumed variation of stress intensity factor along the crack front in each element. The DCCI is formulated for 8-noded brick, 20-noded conventional brick and 20-noded singular brick elements. The numerical examples presented here deal with three-dimensional problems of patch repair technology and part-through cracks. The technique showed a major advantage for the patch repair problems where SIF variations along the crack front are of significance and large mesh sizes are computationally expensive. This along with MVCCI for 12-noded and 20-noded singular elements formed a part of the work on development of accurate and effective post-processing tools.
It is expected that the present work will be helpful in damage tolerance design and assessment of aerospace structures and the experimental work performed as a part of this thesis will enhance confidence in the damage tolerance analysis.
The thesis is concluded in chapter VI presenting the contributions of this thesis and projecting future lines of work possible in this area.
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Vethe, Stine. "NUMERICAL SIMULATION OF FATIGUE CRACK GROWTH." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for produktutvikling og materialer, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18721.
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The purpose of this study was to explore the posibilities and challenges with simulating fatigue crack growth (FCG) by the extended finite element method (XFEM). Another aim was to develope a procedure for XFEM FCG simulations in Abaqus by means of scripting. Finally was the procedure used to simulate FCG in an API standard, cone shaped threaded connection. Different FCG models were reviewed by a limited litterature search and a procedure 2D FCG simulations was carried out by a python script. The procedure succeeded with the simulation of FCG when applied to a model with refined mesh around the crack tip. In the suggested partial tasks of the thesis description were a procedure 3D FCG simulation also suggested, but as this required more computer capacity than available in the study this was not carried out.
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Baldie, Keith David. "Crack growth in hardened cement paste." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/37934.
Full textBooks on the topic "Crack growth"
1
Richard, Hans Albert, and Manuela Sander. Fatigue Crack Growth. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-32534-7.
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M, Fisher Douglas, Holka Donna, and Lewis Research Center, eds. Variables controlling fatigue crack growth of short cracks. [Cleveland, Ohio: National Aeronautics and Space Administration, Lewis Research Center, 1986.
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Krausz, A. S., and K. Krausz. Fracture Kinetics of Crack Growth. Dordrecht: Springer Netherlands, 1988. http://dx.doi.org/10.1007/978-94-009-1381-3.
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Recho, Naman. Fracture Mechanics and Crack Growth. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2012. http://dx.doi.org/10.1002/9781118387184.
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Krausz, A. S. Fracture Kinetics of Crack Growth. Dordrecht: Springer Netherlands, 1988.
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K, Krausz, ed. Fracture kinetics of crack growth. Dordrecht: Kluwer Academic Publishers, 1988.
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Recho, Naman. Fracture mechanics and crack growth. London: ISTE Ltd., 2012.
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Prasad, N. N. V. Thermomechanical crack growth using boundary elements. Southampton: WIT Press, 1998.
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Heinrich, Gert, Reinhold Kipscholl, and Radek Stoček, eds. Fatigue Crack Growth in Rubber Materials. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-68920-9.
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Mi, Yaoming. Three-dimensional analysis of crack growth. Southampton, UK: Computational Mechanics Publications, 1996.
Find full textBook chapters on the topic "Crack growth"
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Richard, Hans Albert, and Manuela Sander. "Designing Components and Structures According to Strength Criteria." In Fatigue Crack Growth, 1–25. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-32534-7_1.
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Richard, Hans Albert, and Manuela Sander. "Damages Caused by Crack Growth." In Fatigue Crack Growth, 27–53. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-32534-7_2.
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Richard, Hans Albert, and Manuela Sander. "Fundamentals of Fracture Mechanics." In Fatigue Crack Growth, 55–112. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-32534-7_3.
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Richard, Hans Albert, and Manuela Sander. "Fatigue Crack Growth Under Cyclic Loading with Constant Amplitude." In Fatigue Crack Growth, 113–51. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-32534-7_4.
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Richard, Hans Albert, and Manuela Sander. "Experimental Determination of Fracture-Mechanical Material Parameters." In Fatigue Crack Growth, 153–86. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-32534-7_5.
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Richard, Hans Albert, and Manuela Sander. "Fatigue Crack Growth Under Service Loads." In Fatigue Crack Growth, 187–221. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-32534-7_6.
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Richard, Hans Albert, and Manuela Sander. "Simulations of Fatigue Crack Growth." In Fatigue Crack Growth, 223–37. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-32534-7_7.
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Richard, Hans Albert, and Manuela Sander. "Crack Initiation Under Cyclic Loading." In Fatigue Crack Growth, 239–50. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-32534-7_8.
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Richard, Hans Albert, and Manuela Sander. "Practical Examples." In Fatigue Crack Growth, 251–83. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-32534-7_9.
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Farahmand, Bahram, George Bockrath, and James Glassco. "Fatigue Crack Growth." In Fatigue and Fracture Mechanics of High Risk Parts, 177–252. Boston, MA: Springer US, 1997. http://dx.doi.org/10.1007/978-1-4615-6009-8_4.
Full textConference papers on the topic "Crack growth"
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Lamborn, Lyndon, Greg Nelson, and James Harter. "Negligible Crack Growth Thresholds." In 2020 13th International Pipeline Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/ipc2020-9248.
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Abstract This paper initiates use of fracture mechanics best practice growth models and tools for pipeline steels with full tri-region da/dN characterization. The utilities associated with establishing negligible crack growth thresholds are demonstrated. Pipeline operators are often presented with decisions that could be supported with scientifically vetted and situationally accurate stress thresholds for negligible crack growth. The threshold stress-intensity factor, ΔKth, is the value for ΔK where the crack growth rate, da/dN, approaches the minimum threshold crack growth rate. Stress-intensity factors at or below this threshold value result in crack growth small enough for operators to practically ignore it in pipeline integrity assessments. Previously, a ΔKth value of 2.0 MPa*m0.5 had been suggested for general use in API 579[1]. The API 579 value appears conservative when compared to industry experience and established ΔKth for similar steel alloys across all stress ratios. By establishing an on-shore pipeline specific ΔKth which considers a pipeline-specific da/dN threshold and stress ratio effects, operators are afforded the opportunity to: • exclude certain pipelines or portions of pipelines from crack growth susceptibility, • identify features with no life limit, • adjust load / boundary conditions to preclude growth, • improve computational efficiency by discarding load cycles below threshold, and, • more accurately simulate crack growth scenarios Pipeline crack growth testing has been researched to derive reasonable and prudent negligible ΔKth values through a closer examination of loading scenarios and environments which affect ΔKth. A da/dN threshold for when diminishingly small crack growth rates can be neglected for typical pipeline assets was determined based on observed pressure fluctuation frequencies. Applications and value derived from deployment of ΔKth are illustrated for North American pipeline assets. Environmental and blunting effects on ΔKth for near-neutral pH stress corrosion cracking previously developed are shown for comparison and utility. Fully established negligible growth thresholds pave the way toward adoption of next-level fracture mechanics best practice models and tools such as AFGROW and NASGRO, and facilitates crack growth simulations and root-cause analysis.
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Mellings, S. C., and J. M. W. Baynham. "Automatic Fatigue Crack Growth." In ASME 2009 Pressure Vessels and Piping Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/pvp2009-77252.
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One of the critical requirements of fatigue crack growth simulation is calculation of the remaining life of a structure under cyclic loading. This paper presents a method which predicts the remaining fatigue life of a part, and gives information on the eventual mode of failure. The path of a growing crack needs to be understood so that informed assessment can be made of the structural consequences of eventual fast growth, and the likelihood of leakage and determination of leakage rates. For these reasons the use of standard handbook solutions for crack growth is generally not adequate, and it is essential to use the real geometry and loading. The reasons for performing such simulation work include preventive investigations performed at the design stage, forensic investigations performed after failure, and sometimes forensic investigations performed during failure-when the results provide input to the planning of remedial work. This paper focuses on the 3D simulation of cracks growing in metal structures exposed to cyclic loading, and explains the techniques which are used. The loading might arise from transients of pressure or other mechanical forces, or might be caused by thermal-stress variations. The simulation starts from an initial crack which can be of any size and orientation. The relevant geometry of the cracked component is modelled, and the loading is identified using one or more load cases together with a load spectrum which shows how the loading cycles. The effects of the crack are determined by calculating stress intensity factors at all positions along the crack front (it would be called the crack tip if the modelling was performed in 2D). The rate and direction of crack growth at each part of the crack front are calculated using one of the available crack growth laws, together with appropriate material properties. The effects of such growth are accumulated over a number of load cycles, and a new crack shape is determined. The process is repeated as required. The use of multi-axial and mixed mode techniques allows the crack to turn as a result of the applied loading, and the resulting crack path is therefore a consequence of both the detail of the geometry and the loading to which the structure is subjected. Gas or other fluid pressures acting on the crack faces can have significant impact, as can the contact between opposing crack faces when a load case causes part of the crack to close.
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Welch, Donald E., Lee M. Hively, and Ray F. Holdaway. "Nonlinear Crack Growth Monitoring." In ASME 2000 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/imece2000-2459.
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Abstract Structures subject to crack growth spend 90–95% of their lifetime in nucleation of very tiny flaws into measurable crack sizes. Due to the large variation in initial flaw sizes and the mathematics of flaw growth, the fatigue lifetimes, even of high-quality structures, can vary by a factor of as much as 10 to 20 even in a small fleet. This large variation in fatigue lifetimes leads to conservative statistics, which often prompts the premature retirement or overhaul of structures, since they focus on the weakest members of the fleet, while the remainder of the fleet is sound. In the past two years, Oak Ridge National Laboratory (ORNL) has developed a new Griffith energy-based technique that can provide useful warning of the impending failure of a structure due to end-of-life crack propagation. This technique has been demonstrated by test and analysis in fiberglass composite for tension-tension fatigue.
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Cláudio Roberto Ávila da Silva Júnior, Rodrigo Villaca Santos, Lucas Gimenis de Moura, and Waldir Mariano Machado Júnior. "Bounds for Crack Growth." In 23rd ABCM International Congress of Mechanical Engineering. Rio de Janeiro, Brazil: ABCM Brazilian Society of Mechanical Sciences and Engineering, 2015. http://dx.doi.org/10.20906/cps/cob-2015-2658.
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Kim, Nak Hyun, Yun Jae Kim, Catrin M. Davies, Ali Mehmanparast, and Kamran M. Nikbin. "The Effect of Discontinuous Crack in Creep Crack Growth Tests." In ASME 2013 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/pvp2013-98142.
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Discontinuous cracks ahead of the leading crack tip may be present in observedcertain creep crack growth tests as well as in components. In this work, a single crack of different dimensions and distance from the leading crack has been numerically modeled in a compact tension specimen using elastic, elastic-plastic and elastic-plastic-creep loading. In order to examine their effects on fracture mechanics parameters a sensitivity analysis was performed to determine the effects of size and distance of the secondary crack with respect to the main crack. t The elastic analysis shows that the compliance is insensitive small cracks ahead of the main crack. Limit load analyses, assuming an elastic-perfectly plastic material, show that the limit load decreases due to the presence of discontinuous cracks ahead of the main crack. Theload versus plastic load-line displacement response of the specimen was significantly influenced by discontinuous cracking. The J contour parameter and C*-integral have been evaluated at the three crack tips and the average of all of them derived for the appropriate contours were compared with the valuesobtained from on ASTM E1820(1) and E1457(2). Whilst the average values of the contour integral are similar to the ASTM J and C* values there is significant differences in J and C* for the individual crack tip values. This need to be further evaluated in future work.
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Van Arsdell, William W., and Stuart B. Brown. "Crack Growth in Polysilicon MEMS." In ASME 1998 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/imece1998-1253.
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Abstract We have developed an experimental protocol for studying slow crack growth in MEMS materials, and we have used this protocol to show that polycrystalline silicon (polysilicon) MEMS are susceptible to stress corrosion cracking. Using a model of the nonlinear dynamics of the specimen, we were able to estimate crack length and crack closure from the frequency response of the specimen. The procedure can resolve 1 nm crack extensions and crack growth rates below 10−13m/s. Crack closure, which has a pronounced effect on the dynamics of this nonlinear system, is possibly associated with the native oxide which grows on the faces of the crack. The data show that subcritical crack growth in polysilicon MEMS is driven by the synergistic effects of water and stress. In contrast to macroscale stress corrosion cracking behavior, we have not found a clear relationship between crack growth rate, stress intensity, and humidity.
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Lee, Gi-Bum, Youn-Young Jang, Nam-Su Huh, Sung-Hoon Park, Noh-Hwan Park, Jun Park, and Kyoungsoo Park. "Crack Growth Simulation Using Iterative Crack-Tip Modeling Technique." In ASME 2022 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/pvp2022-84684.
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Abstract Because of the long-term operation of nuclear power plants, the assessment of crack growth in pipelines has become one of the most important issues. Crack growth resistance in operating nuclear power plants is typically evaluated using linear elastic fracture mechanics based on ASME B&PV Section XI. However, the ASME method predicts the results conservatively, for complex shapes and conditions, while the finite element analysis, which is more accurate, consumes a substantial amount of time and cost. In this study, a finite element analysis-based iterative crack growth program was created to evaluate cracks with more accuracy and time efficiency. The verification of the program was carried out in two cases. By comparing the produced program with the test result of the three-point bending of the beam with rivet holes, it was shown that the program simulates crack propagation in the right direction. In addition, by comparing the results of the fatigue crack growth (FCG) test of CCT/SENT specimens, it was shown that the program can be applied to the evaluation of major failure mechanisms in the nuclear power plants such as stress corrosion crack (SCC) growth and FCG.
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Brust, F. W., D. J. Shim, G. Wilkowski, and D. Rudland. "PWSCC Crack Growth Modeling Approaches." In ASME 2011 Pressure Vessels and Piping Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/pvp2011-57974.
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Flaw indications have been found in some dissimilar metal (DM) nozzle to stainless steel piping welds and reactor pressure vessel heads (RPVH) in pressurized water reactors (PWR) throughout the world. The nozzle welds usually involve welding ferritic (often A508) nozzles to 304/316 stainless steel pipe) using Alloy 182/82 weld metal. The welds may become susceptible to a form of corrosion cracking referred to as primary water stress corrosion cracking (PWSCC). It can occur if the temperature is high enough (usually >300C) and the water chemistry in the PWR is typical of operating plants. The weld residual stresses (WRS) induced by the welds are a main driver of PWSCC. Several mechanical mitigation methods to control PWSCC have been developed for use on a nozzle welds in nuclear PWR plants. These methods consist of applying a weld overlay repair (WOR), using a method called mechanical stress improvement process (MSIP), and applying an inlay to the nozzle ID. The purpose of a mitigation method is to reduce the probability that PWSCC will occur in the nozzle joint. The key to assessing the effectiveness of mitigation is to determine the crack growth time to leak with and without the mitigation. Indeed, for WOR and MSIP, the weld residual stresses are often reduced after application while for inlay they are actually increased. However, all approaches reduce crack growth rates if applied properly. Procedures for modeling PWSCC growth tend to vary between organizations performing the analyses. Currently, the prediction of PWSCC crack growth is based on the stress intensity factors at the crack tips. Several methods for evaluating the stress intensity factor for modeling the crack growth through these WRS fields are possible, including using analytical, natural crack growth using finite element methods, and using the finite element alternating method. This paper will summarize the methods used, critique the procedures, and provide some examples for crack growth with and without mitigation. Suggestions for modeling such growth will be provided.
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Salzman, Ronald N., Neville F. Rieger, and Letian Wang. "Turbine Blade Fatigue Crack Growth." In ASME 2004 Power Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/power2004-52138.
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This paper presents an approach that has not previously been applied to predict power plant component fatigue failure. While many computer tools and procedures do exist for life prediction, recent experience shows that those methods often lack needed precision. In addition detailed knowledge of the material fracture mechanics properties and of the component load history, including the sequence of events. For complex load applications the sequence of events has been shown to be significant. For these applications Linear Damage Models (Minors Rule) are inadequate. A case where the accuracy of existing methods was found to be insufficient involved a steam power plant. Fatigue cracks were observed in the blade root area of 10% of the L-0 row turbine blades. The cracked blades were removed and replaced with new blades. The question to be answered was how safe are the reinstalled blades that had no visible damage. A successful solution was obtained by integrating NASA technology with STI experience in the analysis of steam and gas turbine blades. This led to the development of a proprietary, advanced life prediction computer code that: • incorporates contributions from both HCF and LCF to calculate crack growth, • treats the actual sequence in which all HCF and LCF loading has been applied, and • initiates the crack growth process from the microscopic inclusions and flaws. Complete analysis included comprehensive material tests, performed at a qualified material-testing laboratory. Test specimens were created from actual components, which had been subjected to over 30 years of service. Realizing that fatigue testing data variations can be relatively large, results from Life Cycle showed solid agreement with both short-term (105 to 106 cycles) material tests and with long-term (∼160×109 cycles) operation under high strain steady load and low strain cyclic load conditions.
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Zuo, Jianzheng, Xiaomin Deng, and Michael A. Sutton. "Computational Aspects of Three-Dimensional Crack Growth Simulations." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-60699.
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An important task in mixed-mode fracture analysis and prediction is the simulation of crack growth under mixed-mode conditions. To complete such a task, one must have (a) a computer code capable of handling the kinematics of general crack growth and determining the stress and deformation states during crack growth, and (b) a fracture criterion that can properly predict the onset and direction of crack growth. A current challenge is the simulation of mixed-mode crack growth under three-dimensional (3D) conditions, such as the growth of surface cracks, corner cracks, embedded cracks, and cracks with a curved crack surface and/or a curved crack front. This paper focuses on item (a) in the above discussion and describes the computational aspects of a simulation procedure, which can be used together with a given fracture criterion to simulate crack growth. For illustration purposes, a CTOD fracture criterion (e.g. [11]) will be used when needed. The associated algorithms for simulating arbitrary 3D crack growth under general loading conditions have been developed and successfully implemented by the authors in a custom, finite element based, crack growth analysis and simulation code—CRACK3D. In particular, this paper will present strategies for automatic re-meshing of regions around growing crack fronts in a 3D body, and will discuss verification examples.
Reports on the topic "Crack growth"
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Christman. NR198704 Crack Initiation and Growth Modeling and Definition of Crack Growth Behavior in Line Pipe Steels. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), January 1987. http://dx.doi.org/10.55274/r0011199.
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The objective of the Crack Growth Modeling effort is to develop an understanding of the factors that control stress-corrosion crack growth. This effort has two main tasks: initiation and growth modeling; and definition of crack growth behavior. The model is used to predict crack growth based on determining when conditions are conducive to crack growth. Since the model deals with early crack growth, the properties of the metal nearest the surface must be considered. The second task, definition of crack growth behavior, deals with the growth of large cracks up to the point of failure. Of particular interest is the crack length-to-depth ratio because a crack with a small ratio gives a greater chance of leaking before breaking into a larger ratio. Also there is less chance of small crack linkage to form larger cracks when the lengthwise crack velocity is reduced. Thus a good understanding of the factors that control crack shape is essential for formulating a predictive model for long term crack growth.
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Post, Roger A. Crack Growth Testing. Fort Belvoir, VA: Defense Technical Information Center, March 1994. http://dx.doi.org/10.21236/ada361403.
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Welch, DE. Nonlinear Crack Growth Monitoring. Office of Scientific and Technical Information (OSTI), March 2001. http://dx.doi.org/10.2172/814371.
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Welch, D. E. Nonlinear Crack Growth Monitoring. Office of Scientific and Technical Information (OSTI), January 2000. http://dx.doi.org/10.2172/816619.
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Kirchner, Ted E., and John McCoy. Automated Fatigue Crack Growth Measurement. Fort Belvoir, VA: Defense Technical Information Center, July 1988. http://dx.doi.org/10.21236/ada198642.
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Brust. L51576 Crack Growth Behavior and Modeling. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), March 1989. http://dx.doi.org/10.55274/r0010642.
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The objective of the Crack Growth/Modeling effort of the NG-18 Line Pipe Supervisory Committee's Stress-Corrosion Phase is to develop an understanding of the factors that control stress-corrosion crack growth. This information can be used to develop models for predicting crack growth and to mitigate crack growth through control of metallurgical parameters and operating conditions. This effort has been divided into the following four main tasks: (1) Characterization of crack shape,(2) Identification of a crack force driving parameter,(3) Determination of the effects of mechanical properties on crack growth and shape, and(4) Examination of the effects of crack interaction on overall crack growth. The background, procedures, and results of the work done in each of these tasks will be described separately.
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Hoyt, Jeffrey John. Atomistic simulations of brittle crack growth. Office of Scientific and Technical Information (OSTI), April 2007. http://dx.doi.org/10.2172/908078.
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Hatch, P., J. VanDenAvyle, and J. Laing. Fatigue crack growth automated testing method. Office of Scientific and Technical Information (OSTI), June 1989. http://dx.doi.org/10.2172/5909955.
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Healy, Thomas E. Fatigue crack growth in lithium hydride. Office of Scientific and Technical Information (OSTI), September 1993. http://dx.doi.org/10.2172/95360.
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Bubenik and Nestleroth. L51619 Effects of Loading on the Growth Rates in Deep Stress-Corrosion Cracks. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), August 1990. http://dx.doi.org/10.55274/r0010094.
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With the development of improved techniques for detection of stress corrosion cracks in existing pipelines, the pipeline industry is faced with the problem of estimating the growth rates of these cracks. Current efforts in model development are addressing the problem but, in order to verify these models, accurate average crack velocity data are needed (average crack velocity being defined as the average rate of crack growth with time, crack velocity is the instantaneous rate of crack tip dissolution.) Currently available data are limited and are based primarily on either slow-strain rate tests or tapered tensile tests. The loading conditions in the former are unrepresentative of actual operating conditions while the crack depths in the latter are much shallower than those observed in service. Some fracture mechanics data also are available for this system but the specimen and crack geometry used in these tests are not similar to the geometry of the field failures*. In addition, results of recent PRCI research suggest that the stress intensity parameter, K, which is used to relate different cracking geometries, is a poor crack driving force parameter for SCC in line pipe steels. The overall objective of this work is to obtain accurate average crack velocity data as a function of crack depth and loading conditions. The program is divided into two tasks: Task 1 - Effect of Crack Depth and Cyclic Loading Conditions on Crack Growth and Task 2 - Inhibition of Crack Growth.