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Добірка наукової літератури з теми "Crack initiation prediction"

Автор: Grafiati
Опубліковано: 3 липня 2024

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Статті в журналах з теми "Crack initiation prediction":

1

Mars, W. V. "Multiaxial Fatigue Crack Initiation in Rubber." Tire Science and Technology 29, no. 3 (July 1, 2001): 171–85. http://dx.doi.org/10.2346/1.2135237.

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Abstract This paper describes a new model for predicting multiaxial fatigue crack initiation in rubber. The work is motivated by a need to predict crack initiation life in tires, based on strain histories obtained via finite element analysis. The new model avoids the need to explicitly include cracks in the finite element model, and applies when the cracks are small compared to the strain gradient. The model links the far-field strain state to the energy release rate of an assumed intrinsic flaw. This is accomplished through a new parameter, the cracking energy density. The cracking energy density is the portion of the total elastic strain energy density that is available to be released on a given material plane. The model includes an algorithm to select the material plane which minimizes the life prediction for a given strain history. The consequences of the theory for simple strain histories are presented, as well as predictions for more complicated histories. The theory is compared with published data, and with new results from recent combined axial/torsion fatigue experiments.
2

An, J., J. Chen, G. Gou, H. Chen, and W. Wang. "Prediction of corrosion fatigue crack initiation behavior of A7N01P-T4 aluminum alloy welded joints." International Journal of Modern Physics B 31, no. 16-19 (July 26, 2017): 1744034. http://dx.doi.org/10.1142/s0217979217440349.

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Through investigating the corrosion fatigue crack initiation behavior of A7N01P-T4 aluminum alloy welded joints in 3.5 wt.% NaCl solution, corrosion fatigue crack initiation life is formulated as [Formula: see text] and the mechanism of corrosion fatigue crack initiation is proposed. SEM and TEM tests revealed that several corrosion fatigue cracks formed asynchronously and the first crack does not necessarily develop into the leading crack. The uneven reticular dislocations produced by fatigue loading are prone to piling up and tangling near the grain boundaries or the second phases and form the “high dislocation-density region” (HDDR), which acts as an anode in microbatteries and dissolved to form small crack. Thus the etching pits, HDDR near the grain boundaries and second phases are confirmed as the main causes inducing the initiation of fatigue crack.
3

Shiraiwa, Takayuki, Fabien Briffod, and Manabu Enoki. "Prediction of Fatigue Crack Initiation of 7075 Aluminum Alloy by Crystal Plasticity Simulation." Materials 16, no. 4 (February 14, 2023): 1595. http://dx.doi.org/10.3390/ma16041595.

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The 7075 aluminum alloy is a promising material for the aerospace industry due to its combination of light weight and high strength. This study proposed a method for predicting fatigue crack initiation of the 7075 aluminum alloy by crystal plasticity finite element analysis considering microstructures. In order to accurately predict the total fatigue life, it is necessary to calculate the number of cycles for fatigue crack initiation, small crack growth, and long crack growth. The long crack growth life can be estimated by the Paris law, but fatigue crack initiation and small crack growth are sensitive to the microstructures and have been difficult to predict. In this work, the microstructure of 7075 aluminum alloy was reconstructed based on experimental observations in the literature and crystal plasticity simulations were performed to calculate the elasto-plastic deformation behavior in the reconstructed polycrystalline model under cyclic deformation. The calculated local plastic strain was introduced into the crack initiation criterion (Tanaka and Mura, 1981) to predict fatigue crack initiation life. The predicted crack initiation life and crack morphology were in good agreement with the experimental results, indicating that the proposed method is effective in predicting fatigue crack initiation in aluminum alloys. From the obtained results, future issues regarding the prediction of fatigue crack initiation were discussed.
4

Man, Xiaolan, Long Li, Hong Zhang, Haipeng Lan, Xiuwen Fan, Yurong Tang, and Yongcheng Zhang. "Study on the Relationship between Crack Initiation and Crack Bifurcation in Walnut Shells Based on Energy." Agriculture 14, no. 1 (December 29, 2023): 69. http://dx.doi.org/10.3390/agriculture14010069.

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Clarifying the dissipated energy required for crack expansion is an effective way to control material crushing. Therefore, based on the material fracture probability model and fractal theory, the energy range required for crack extension was determined, and the morphology of the cracks was quantified. This study investigates the influence of walnut size on crack propagation characteristics; this includes its effects on the crack initiation threshold energy, representing resistance to crack initiation, and the crack bifurcation threshold energy, representing resistance to crack bifurcation. The results show that crack extension has a well-defined threshold energy below which cracks do not initiate or bifurcate. The size of walnuts significantly impacts crack propagation characteristics, showing that both crack initiation threshold energy and crack bifurcation threshold energy decrease with increasing walnut sizes. In addition, there is a positive correlation function between the crack initiation threshold energy and the crack bifurcation threshold energy. The experimental results can offer fresh insights into material fracture prediction and serve as a reference for numerical simulations.
5

Shen, Qingqing, Qiuhua Rao, Quan Zhang, Zhuo Li, Dongliang Sun, and Wei Yi. "A New Method for Predicting Double-Crack Propagation Trajectories of Brittle Rock." International Journal of Applied Mechanics 13, no. 02 (March 2021): 2150026. http://dx.doi.org/10.1142/s1758825121500265.

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Multi-crack propagation is investigated mainly by experimental measurement and little by theoretical prediction. The classical fracture criteria can better predict tensile fracture under arbitrary loading conditions (pure tensile, pure shear and mixed-mode), but have difficulty in predicting shear fracture. In this paper, Mode I and Mode II SIFs of branch-cracks initiated by the original cracks were calculated by the complex function and superposition method, and a new theory of multi-crack propagation was established based on the criterion of maximum tensile-shear SIF ratio. Theoretical results of two collinear cracks under uniaxial compression show that the cracks initiate more easily at [Formula: see text] (the crack inclination angle) than other angles. Coalescence of branch-crack only occurs at [Formula: see text] with the maximum crack propagation length. Peak stress [Formula: see text] reaches minimum when [Formula: see text] (inner friction angle of rock), and the larger the [Formula: see text], the closer to the compressive strength of rock the [Formula: see text]. Mechanism of the crack initiation and propagation are all Mode I under uniaxial compression. Uniaxial compressive test results of red sandstone (the rock material is assumed to be homogeneous) pre-cracked specimens agree well with predicted results of the crack initiation, stable and unstable propagation, which can prove the validity of the new multi-crack propagation prediction method.
6

Ohata, Mitsuru, Takuya Fukahori, and Fumiyoshi Minami. "Prediction of Ductile Crack Growth from Ductility of Steel." Materials Science Forum 539-543 (March 2007): 2186–91. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.2186.

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This study pays attention to reveal the material properties that control resistance curve for ductile crack growth (CTOD-R curve) on the basis of the mechanism for ductile crack growth, so that the R-curve could be numerically predicted only from those properties. The crack growth tests using 3-point bend specimens with fatigue pre-crack were conducted for two steels that have different ductile crack growth resistance with almost the same CTOD level for crack initiation, whereas both steels have the same “Mechanical properties” in terms of strength and work hardenability. The observation of crack growth behaviors provided that different mechanisms between ductile crack initiations from fatigue pre-crack and subsequent growth process could be applied. It was found that two “Mechanical properties” associated with ductile damage of steel could mainly influence CTOD-R curve; one is a resistance of ductile crack initiation estimated with critical local strain for ductile cracking from the surface of notched specimen, and the other one is a dependence of stress triaxiality on ductility obtained with circumferentially notched round-bar specimens. The damage model for numerically simulating the R-curve was proposed taking the two “ductile properties” into account, where ductile crack initiation from crack-tip was in accordance with critical local strain based criterion, and subsequent crack growth GTN (Gurson-Tvergaard-Needleman) based triaxiality dependent damage criterion. The proposed model accurately predicted the measured R-curve for the two steels used with the same “strength properties” through ductile crack initiation to growth.
7

Lei, Dong, Ge Li, Bin Kai Shi, and Jian Hua Zhao. "An Improved Model for Predicting Fatigue Crack Initiation Life of GH4169." Applied Mechanics and Materials 29-32 (August 2010): 468–73. http://dx.doi.org/10.4028/www.scientific.net/amm.29-32.468.

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An improved model has been developed to predict fatigue crack initiation life using the criterion of minimizing the Gibbs free energy change considering plastic energy. The prediction process was described in this paper and used to predict the fatigue crack initiation life of notched GH4169 superalloy rolled bar at room temperature and 450°C. The results are acceptable for fatigue crack initiation life prediction in engineering experience and show that the improved model for predicting fatigue crack initiation life as an extension of the concept of minimizing the Gibbs free energy change considering plastic energy is adoptable to some superplastic materials such as GH4169.
8

Wu, Tong Yu, David Arye, Philip E. Irving, Fang Ming Zhao, and Paul Jackson. "Fatigue Crack Development in Epoxy Coatings on Steel Substrate: The Role of Coating and Substrate Properties in Determination of the Onset of Fatigue Cracks." Advanced Materials Research 891-892 (March 2014): 854–59. http://dx.doi.org/10.4028/www.scientific.net/amr.891-892.854.

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Development of service cracks in epoxy based corrosion protective coatings limits the life of the substrate structure. If cracks develop, corrosion protection is lost and costs of repair and re-protection of large marine structures can be crippling. Factors controlling development of cracks in the coating are poorly understood, and predictions of coating lifetime approximate. For bulk tanker applications service strains imposed on coatings arise from both low frequency thermal mismatch strains and mechanical strains from wave action. In this work the number of cycles to crack initiation has been measured during strain controlled fatigue of two selected 300 μm thick coatings applied to a 5.5 mm thick steel substrate. Cycling was performed at frequencies of 1 Hz, and strain amplitudes between ±0.16% and ±0.5%. Coating crack development was monitored optically. It was found that cycles to crack initiation depended on both strain amplitude and on the static ductility of the coating. After initiation crack growth rates in the coating reduced with increasing surface crack length. The significance of the results is considered in the light of requirements for quantitative models for service life prediction of coatings on metallic substrates.
9

Jiang, Yanyao, Fei Ding, and Miaolin Feng. "An Approach for Fatigue Life Prediction." Journal of Engineering Materials and Technology 129, no. 2 (November 9, 2005): 182–89. http://dx.doi.org/10.1115/1.2400260.

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Fatigue process is described as the nucleation and growth of cracks to final failure. These two stages are generally modeled with completely different methods with no quantitative relationships between them. A number of fitting parameters are needed to consider different effects. The current work is aimed at developing a robust approach to predicting fatigue life from crack initiation to final fracture. Fatigue damage is related to the stresses and strains. Both crack nucleation and crack growth are governed by the same fatigue damage mechanisms and a single fatigue damage criterion can model both stages. A basic rule is that any material point fails to form a fresh crack if the total accumulated fatigue damage reaches a limit. The approach consists of two steps. Elastic-plastic stress analysis is conducted to obtain the detailed stress-strain responses. A general fatigue criterion is used to predict both fatigue crack nucleation and growth. Notched specimens made of 1070 steel were experimentally tested from crack initiation until fracture. The approach was applied to predict the fatigue life of 1070 steel and the predicted fatigue lives were in excellent agreement with the experimental observations.
10

Liu, Xueshu, Bingrong Yan, and Hongtu Sun. "Fatigue Life Prediction of High Strength Steel with Pitting Corrosion under Three-Point Bending Load." Metals 13, no. 11 (November 2, 2023): 1839. http://dx.doi.org/10.3390/met13111839.

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Offshore structures often suffer from pitting corrosion, which leads to local stress concentrations, a decrease in the cross-sectional area, the subsequent initiation and gradual propagation of cracks, and a shorter service life as a result. This study aims to investigate the impact of pitting corrosion on the fatigue life endurance of high-strength steel used for offshore structures. To this end, a three-point bending fatigue test was first performed on the specimens to obtain the fatigue test data. Then, a fatigue life prediction model consisting of two terms is proposed based on fracture mechanics, and the fatigue test data are used to verify the reliability of the model. Finally, the experimental results are discussed, and conclusions are drawn. The first term was designed for crack initiation. Combining with the energy theory and slip band dislocation theory, a novel equivalent surface defect model was proposed and used to predict the fatigue life of pitted corroded specimens before crack initiation. The second term is designed for crack propagation. The generalized Paris model is adopted for fatigue life prediction during the crack propagation process after the crack angle is taken as a variable. The mathematical model for predicting three-point bending fatigue life was finally obtained, and the average relative error of the data validation results did not exceed 16%, which proved the reliability of the prediction model.
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Статті в журналах

Дисертації з теми "Crack initiation prediction":

1

Røneid, Viggo. "LIFE PREDICTION FOR HEAVY STRUCTURES BASED ON FATIGUE CRACK INITIATION AND GROWTH." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for produktutvikling og materialer, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19001.

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The main goal for this thesis has been to perform fatigue life predictions on large components.Dierent methods were to be chosen and reviwed critically. Experimental datafor girth welded pipes was assessed by means of a version of BS7910 which were modeledfrom scratch. This version was veried with results from CrackWise, and used to predictthe fatigue life for loade cases matching the selected experimental data. The fatigue assessmenttool P-FAT was used to predict the fatigue life for the same experimental data,and the results were compared. Except for some deviations recorded for embedded cracks,a generally good agreement was found between the two tools.Both the modeled BS7910 and P-FAT predicted conservative but accurate fatigue livesfor the experimental data that had signicant defects. They predicted non conservativeresults for specimens that did not have signicant defects, when the initial crack depthwas set to 0.1 mm. When the initial crack depth was set to 0.5 mm the modeled versionpredicted fatigue lives in agreement with the experimental results.Fatigue life predictions were also performed by assistance of S-N curves provided by DNVRP-C203.The results from these predictions were in agreement with the experimentaldata, except for four specimens. These four specimens had signicant aws, which reducedthe fatigue life signicantly.A review of a two-phase fatigue assessment model was made. This model uses a strainedbased approach to assess the fatigue crack initiation phase, and the fracture mechanicapproach suggested in the BS7910 to assess fatigue crack growth. This method haveshown promising results for fatigue assessment of llet welds in the literature, but themodel needs further investigation and calibration to be used to predict fatigue life ofgirth welded structures. A specic area to investigate is the proposed transition depth of0.1 mm. This depth is dubious based on the results
2

Cadario, Alessandro. "Life prediction and mechanisms for the initiation and growth of short cracks under fretting fatigue loading." Doctoral thesis, KTH, Hållfasthetslära (Inst.), 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4185.

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Fretting fatigue is a damage process that may arise in engineering applications where small cyclic relative displacements develop inside contacts leading to detrimental effects on the material fatigue properties. Fretting is located in regions not easily accessible, which makes it a dangerous phenomenon. It is therefore important to be able to make reliable predictions of the fretting fatigue lives. The work presented in this thesis has its focus on different aspects related to fretting fatigue in the titanium alloy Ti-17. A fretting experiment was developed which allowed for separate control of the three main fretting loads. Initially, the evolution of the coefficient of friction inside the slip region was investigated experimentally and analytically. Subsequently, 28 fretting tests were performed in which large fatigue cracks developed. The fretting tests were firstly evaluated with respect to fatigue crack initiation through five multiaxial fatigue criteria. The criteria predicted a too high fretting fatigue limit. A possible clue to the discrepancy was found in the fretting induced surface roughness with the asperity-pit interactions. The fatigue growth of the large fretting cracks was numerically modelled through a parametric crack growth procedure. The predicted lives were compared to the experimental outcome. The numerical simulations showed that linear elastic fracture mechanics was an appropriate tool for the prediction of fretting fatigue propagation lives in the long crack regime. Fatigue cracks spend most of their propagation life in the small crack regime. The possibility of modelling the small crack behaviour is therefore very important from the engineering point of view. The fatigue growth of through thickness short cracks was studied experimentally and numerically in the four-point bend configuration. It was found that linear elastic fracture mechanics and closure-free material growth data furnished conservative estimates for cracks longer than 50 μm. One method to improve fretting fatigue life is to shot peen the contact surfaces. Experimental results on fretting life with or without shot peening were simulated. The fatigue life enhancement in shot peened specimens could be explained by slower crack growth in the surface material layer with residual compressive stresses.
QC 20100827
3

Yuen, Dick Kwan Kenneth. "Brake disc life prediction for material evaluation and selection : the application of finite element and fatigue analysis to the prediction of crack initiation in brake discs during operation." Thesis, University of Bradford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363977.

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4

Baum, Christian. "Methode zur Anrisslebensdauervorhersage bei beliebigen mehrachsigen Beanspruchungen (EVICD): Fortschrittliches Werkzeug für die ingenieurmäßige Praxis und Verifikation / Crack initiation life prediction method for arbitrary multiaxial loadings (EVICD): Advanced tool for the engineering practise and verification." Gerhard-Mercator-Universitaet Duisburg, 2006. http://www.ub.uni-duisburg.de/ETD-db/theses/available/duett-05302006-204151/.

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In the frame of the current work the incremental EVICD(EVent Independent Continuous Damage) crack initiation life prediction method for arbitrary multiaxial loading was consequently further developed. A modular concept was established to account also for an application of the EVICD method in the engineering practise. Numerous comparisons of EVICD predictions and experimental results have shown satisfactory prediction results of the EVICD method which is recommended in its present stage as a high-grade crack initiation life prediction tool for engineering practise.
5

Visvanatha, Sanjeev K. "A study on the use of Neuber's rule in fatigue crack initiation predictions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0012/MQ36898.pdf.

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6

Malm, Richard. "Predicting shear type crack initiation and growth in concrete with non-linear finite element method." Doctoral thesis, KTH, Bro- och stålbyggnad, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10156.

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In this thesis, the possibility to numerically describing the behaviour that signifies shear type cracking in concrete is studied. Different means for describing cracking are evaluated where both methods proposed in design codes based on experiments and advanced finite element analyses with a non-linear material description are evaluated. It is shown that there is a large difference in the estimation of the crack width based on the calculation methods in design codes. The large difference occurs due to several of these methods do not account for shear friction in the crack face. The finite element method is an important tool for analysing the non-linear behaviour caused by cracking. It is especially of importance when combined with experimental investigations for evaluating load bearing capacity or establishing the structural health. It is shown that non-linear continuum material models can successfully be used to accurately describe the shear type cracking in concrete. A method based on plasticity and damage theory was shown to provide accurate estimations of the behaviour. The methods based on fracture mechanics with or without inclusion of damage theory, overestimated the stiffness after crack initiation considerably. The rotated crack approach of these methods gave less accurate descriptions of the crack pattern and underestimated the crack widths. After verification of the material model, realistic finite element models based on plasticity and damage theory are developed to analyse the cause for cracking in two large concrete structures. The Storfinnforsen hydropower buttress dam is evaluated where the seasonal temperature variation in combination with the water pressure have resulted in cracking. With the numerical model the cause for cracking can be explained and the crack pattern found in-situ is accurately simulated. The model is verified against measurements of variation in crest displacement and crack width with close agreement. The construction process of a balanced cantilever bridge, Gröndal Bridge, is numerically simulated and a rational explanation of the cause for cracking is presented. It is shown that large stresses and micro-cracks develop in the webs during construction, especially after tensioning the continuing tendons in the bottom flange. Further loads from temperature variation cause cracking in the webs that is in close agreement with the cracking found in-situ. The effect of strengthening performed on this bridge is also evaluated where the vertical Dywidag tendons so far seem to have been successful in stopping further crack propagation.
QC 20100730
7

Cadario, Alessandro. "Life prediction and mechanisms for the initiation and growth of short cracks under fretting fatique loading /." Stockholm : Solid mechanics, Royal Institute of Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4185.

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8

Wang, Yaou. "Failure mechanism and reliability prediction for bonded layered structure due to cracks initiating at the interface." Columbus, Ohio : Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1236645979.

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9

Yang, Yao-Dong, and 楊耀東. "Life Prediction of Rail Fatigue Crack Initiation under Multi-train Braking Condition." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/82710267035457914248.

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碩士
國立屏東科技大學
車輛工程系所
96
In this thesis, the life of rail fatigue crack initiation under multi-train braking condition is explored using the elastic-plastic finite element model. The kinematic hardening behavior of the rail steel is employed throughout the numerical simulations. The temperature-dependent material properties and friction coefficients are also considered in numerical analyses. Numerical simulations are performed to explore the effects of the braking speed, number of cars, axle load and distance between wheelsets. The results show that the crack initiation occurs on rail surface and is located at the maximum value of fatigue parameter, FPmax. The results also indicate that the life of fatigue crack initiation decreases rapidly with increasing number of trains and then gradually approaches to a constant value. The life of fatigue crack initiation decreases as the braking speed increases. Based on the numerical results, a curve-fitted equation is proposed to predict the life of rail fatigue crack initiation, 2Nf , using the number of trains for various braking speeds. The life 2Nf for braking speeds of v=60, 120, 180 and 360 km/h predicted from the results of three trains are only 30%、11%、16%and 35% of the one train situation, respectively.
10

Lavres, Joana Isabel Rodrigues da Costa. "Previsão de vida de iniciação de fendas por fadiga em ligas de alta resistência sujeitas a esforços de flexão-torção." Master's thesis, 2020. http://hdl.handle.net/10316/92167.

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Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e Tecnologia
O objetivo do presente trabalho traduz-se no estudo do comportamento à fadiga de peças entalhadas geradas a partir da liga de alta resistência DIN 34CrNiMo6 e sujeitas a carregamentos proporcionais de flexão combinada com torção. Propriedades como a elevada ductilidade, alta temperabilidade, elevada tenacidade e resistência garantem que a liga supracitada seja selecionada para uma vasta gama de componentes de engenharia. Com efeito, é usual esses mesmos componentes estarem sujeitos a condições de serviço severas e a carregamentos complexos. Além disso, devido a requisitos funcionais é também usual apresentarem descontinuidades geométricas precursoras de fenómenos de concentração de tensões. A combinação de todos estes fatores torna a falha por fadiga suscetível, razão pela é imperativo encontrar uma metodologia de previsão de vida à fadiga exequível e fiável, a fim de reduzir o risco de falha inesperada em serviço. Nesta dissertação pretende-se explorar o conceito de densidade de energia de deformação, assim como o seu potencial na previsão das vidas de iniciação das peças. Para além disto, pretende-se também explorar a capacidade do parâmetro Smith-Watson-Topper (SWT), parametrizando a sua evolução, e tentando estabelecer uma possível relação com a vida à fadiga. O comportamento elasto-plástico do material, quer em termos de relações energéticas, quer em termos de parâmetro SWT, foi estudado com base em ensaios de fadiga oligocíclica. Estes ensaios foram realizados em controlo de deformação, para amplitudes de deformação, ∆ε/2, a variar entre 0,4% e 2%, num total de oito ensaios, e com uma razão de deformação, R_ε, igual a -1. No que toca aos ensaios de fadiga multiaxial, mais concretamente aos carregamentos proporcionais de flexão combinada com torção, foram consideradas duas razões entre o momento fletor (B) e o momento torsor (T): B=2T e B=T. A orientação do momento fletor relativamente à raiz do entalhe foi igual a 0º, 45º e 90º, e a razão de tensão, R, foi de aproximadamente zero. As geometrias dos provetes utilizados nos ensaios de fadiga consistiram em barras de secção circular com entalhes laterais em forma de U.O efeito do entalhe no comportamento à fadiga foi contabilizado com recurso à Teoria das Distâncias Críticas (TCD). As previsões de vida à fadiga foram obtidas com recurso aos modelos Smith-Watson-Topper (SWT), densidade de energia de deformação plástica, densidade de energia de deformação total, parâmetro Smith-Watson-Topper (SWT) e, ainda, com base na deformação plástica cíclica. No que diz respeito às previsões de vida à fadiga, o modelo SWT e o modelo da densidade de energia de deformação total foram aqueles que deram melhores resultados, traduzindo-se em valores mais próximos das vidas experimentais e desvios-padrão inferiores.
The main objective of the present work is the study of fatigue crack initiation behaviour in notched DIN 34CrNiMo6 steel bars under proportional bending-torsion loading. Properties such as high ductility, deep hardenability, toughness and strength make this alloy a prime choice for a vast range of engineering components. In fact, these components are often subjected to severe service conditions and complex loading. Furthermore, due functional requirements, they contain geometric discontinuities which are likely to cause stress concentration phenomenona. The combination of all these factors makes these components susceptible to fatigue failure, reason why it is imperative to find reliable fatigue life prediction models in order to minimize the risk of unexpected failure. In this dissertation, it is intended to explore the concept of strain energy density as well as its potential to predict the fatigue crack initiation life. In addition, it is also intended to explore the capacity of the Smith-Watson-Topper (SWT) parameter, parameterizing its evolution, and trying to establish a possible relationship with fatigue life. The elasto-plastic behavior of the material, in terms of both energy relationships and SWT parameter, was studied based on uniaxial low-cycle fatigue tests. These tests were performed in strain-controlled conditions, for total strain amplitudes, ∆ε/2, varying between 0.4% and 2%, in a total of eight tests, and with a strain ratio, R, equal to -1. With regard to the multiaxial proportional bending-torsion fatigue tests, two ratios of the bending moment (B) to the torsion moment (T) were considered, more specifically B = 2T and B = T. The orientation of the bending moment with respect to the notch root was equal to 0º, 45º and 90º, and the stress ratio, R, was approximately equal to zero. The specimens used in experimental tests consisted of circular cross-section round bars with lateral U-shaped notches.The notch effect on fatigue behavior was accounted for using the Theory of Critical Distances (TCD). Fatigue life predictions were obtained using the following approaches: Smith-Watson-Topper (SWT) model, plastic strain energy density model, total strain energy density model , a model based on the Smith-Watson-Topper (SWT) parameter, and a model based on the cyclic plastic strain. With regard to fatigue life predictions, the SWT model and the total strain energy density model exhibited the best results, i.e. values closer to the experimental lives and lower standard deviations.

Книги з теми "Crack initiation prediction":

1

Alfred, Buch. Ratio of crack initiation life to total fatigue life and use of local strain approach for prediction of fatigue life. Haifa: Technion Israel Institute of Technology, Dept. of Aeronautical Engineering, 1988.

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Alfred, Buch. Prediction of fatigue life of notched specimens under aircraft loading and importance of the relative method in the case of local strain approach. Haifa: Technion Israel Institute of Technology, Dept. of Aeronautical Engineering, 1986.

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3

S, Johnson W., and Langley Research Center, eds. Prediction of matrix fatigue crack initiation in notched SCS-6/Ti-15-3 metal matrix composites. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1991.

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4

McManus, Hugh L. N., 1958- and United States. National Aeronautics and Space Administration., eds. Prediction of microcracking in composite laminates under thermomechanical loading. [Washington, D.C: National Aeronautics and Space Administration, 1995.

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5

Koning, A. V. de. Finite element analyses of stable crack growth in thin sheet material. Amsterdam: National Aerospace Laboratory, 1985.

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1950-, Harris Charles E., and Langley Research Center, eds. Analytical methodology for predicting the onset of widespread fatigue damage in fuselage structure. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1996.

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7

Wong, A. K. On the application of the strain energy density theory in predicting crack initiation and angle of growth. Melbourne, Australia: Aeronautical Research Laboratories, 1986.

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An investigation of crack-tip stress field criteria for predicting cleavage-crack initiation. Washington, DC: Division of Engineering, Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, 1991.

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Частини книг з теми "Crack initiation prediction":

1

Sakaguchi, Ryota, Takayuki Shiraiwa, and Manabu Enoki. "Prediction of Fatigue Life Induced by Defects Considering Crack Initiation." In Proceedings of the 17th International Conference on New Trends in Fatigue and Fracture, 335–40. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-70365-7_39.

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2

Sallam, Hossam El-Din M., and Amr A. Abd-Elhady. "Prediction of Crack Initiation Site in Fastener Hole of Composite Laminate." In Advanced Composites for Aerospace, Marine, and Land Applications II, 185–98. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2015. http://dx.doi.org/10.1002/9781119093213.ch14.

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Sallam, Hossam El-Din M., and Amr A. Abd-Elhady. "Prediction of Crack Initiation Site in Fastener Hole of Composite Laminate." In Advanced Composites for Aerospace, Marine, and Land Applications II, 187–98. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-48141-8_14.

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4

Osterstock, Stephane, Christian F. Robertson, Maxime Sauzay, Suzanne Degallaix, and Veronique Aubin. "Prediction of the Scatter of Crack Initiation under High Cycle Fatigue." In The Mechanical Behavior of Materials X, 363–66. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-440-5.363.

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5

Nurtjahjo, A., W. Ott, R. Marissen, K. H. Trautmann, and H. Nowack. "Comparison of the Prediction Capability of Crack Initiation Life Prediction Methods for Biaxial Loading Conditions." In Low Cycle Fatigue and Elasto-Plastic Behaviour of Materials—3, 317–24. Dordrecht: Springer Netherlands, 1992. http://dx.doi.org/10.1007/978-94-011-2860-5_52.

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Martikainen, Jukka, Esa Hiltunen, Fisseha Brhane, Victor Karkhin, and S. Ivanov. "Prediction of Liquation Crack Initiation in Al-Mg-Si Alloy Welded Joints." In Hot Cracking Phenomena in Welds III, 71–86. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-16864-2_5.

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Schütz, W., and P. Heuler. "A Review of Fatigue Life Prediction Models for the Crack Initiation and Propagation Phases." In Advances in Fatigue Science and Technology, 177–219. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-2277-8_8.

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Branco, R., J. D. Costa, F. Berto, A. Kotousov, and F. V. Antunes. "Prediction of Fatigue Crack Initiation Life in Notched Cylindrical Bars Under Multiaxial Cycling Loading." In Structural Integrity, 271–77. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-13980-3_35.

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Glinka, G., and A. Newport. "Effects of Notch-Tip Stress-Strain Calculation Method on the Prediction of Fatigue Crack Initiation Life." In Low Cycle Fatigue and Elasto-Plastic Behaviour of Materials, 473–78. Dordrecht: Springer Netherlands, 1987. http://dx.doi.org/10.1007/978-94-009-3459-7_73.

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Taheri, S. "A Damage Cumulation Law under Non Proportional Cyclic Loading with Overloads for the Prediction of Crack Initiation." In Anisotropy and Localization of Plastic Deformation, 459–62. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3644-0_107.

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Тези доповідей конференцій з теми "Crack initiation prediction":

1

Davies, Catrin M., Noel P. O’Dowd, Kamran M. Nikbin, and George A. Webster. "Prediction of Creep Crack Initiation Under Transient Stress Conditions." In ASME 2006 Pressure Vessels and Piping/ICPVT-11 Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/pvp2006-icpvt-11-93104.

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A method to predict the time for creep crack initiation (CCI) from a stationary crack tip is presented. The method is relevant to situations where small scale yield or widespread plasticity conditions prevail on initial loading. Initiation is considered to occur at the attainment of a critical creep strain at a small distance from the crack tip. The model proposed here considers the integrated effects of creep strain accumulation as the stress distribution changes from that on initial loading (controlled by J) to the steady state creep stress distribution (controlled by C*). Material properties are chosen to represent Type 316H stainless steel at 550°C and plane strain conditions are considered. For the conditions examined, the CCI times predicted are significantly shorter times than those predicted using a steady state creep model.
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Bednarz, Piotr, and Jaroslaw Szwedowicz. "Crack Propagation Prediction Using Haensel Damage Model." In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-68162.

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The Haensel damage model correlates lifetime of a component until crack initiation to the dissipated and stored energy in the material during cyclic loading. The crack initiation is influenced by mean stresses. The Haensel damage model considers the mean stress effect by including compressive and tensile stresses in calculations of elastic strain energy during cyclic loading conditions. The goal of the paper is to extend the above model to predict crack propagation under large cyclic plasticity and non-proportional loading conditions. After voids initiation onset of necking, voids growth and linking takes place among them. During this process a mesocrack is created. This stage of fracture involves the same amount of released energy for new crack surface creation as dissipated energy for mesocrack initiation. The amount of dissipated and stored energy is related to the process zone size and to the number of cycles. Ilyushin’s postulate is used to calculate the amount of dissipated energy. In order to consider a contribution of tensile stresses only during loading to crack propagation, tensile/compressive split is performed for the stress tensor. One of the key drivers of this paper is to provide a straightforward engineering approach, which does not require explicit modelling of cracks. The proposed mathematical approach accounts for redistribution of stresses, strains and energy during crack propagation. This allows to approximate the observed effect of distribution of dissipated energy on the front of a crack tip. The developed approach is validated through FE (Finite Element) simulations of the Dowling and Begley experiment. The Haensel lifetime prediction of Dowling’s experiment is in good agreement with the experimental data and the explicit FE results. Finally, the proposed mathematical approach simplifies significantly the engineering effort for Nonlinear Fracture Mechanics lifetime prediction by avoiding the requirement to simulate real crack propagation using node base release methods, XFEM or remeshing procedures.
3

Wu, Guiyi, David Smith, and David Tanner. "Prediction of Fatigue Crack Initiation and Growth During Thermal Cycling." In ASME 2015 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/pvp2015-45235.

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Conventional approaches to assess fatigue under combined thermal and mechanical loading often utilize a fatigue design curve. In this paper models based on the physics and mechanics for the initiation and growth of fatigue cracks in stainless steel are first explained. The models are based on experimental evidence gathered for the initiation and growth of small cracks created during strain controlled laboratory tests. This evidence is then linked with data for the growth of large fatigue cracks in stainless steel. In the paper these models are coupled with finite element analyses to explore the fatigue initiation and growth of cracks in stainless steel pipes subjected to thermal cycling. It is assumed that the material behaviour is elastic-perfectly plastic, rate independent and fatigue occurs in air. The stress and strain fields for pipes subjected to a range of thermal loading conditions are explored. The fields are shown to be sensitive to parameters such as the Biot and Fourier numbers that include pipe dimensions, physical properties, dwell time and thermal conditions. Of particular interest is the temperature range and dwell time during thermal loading. Finite element analyses are then used to determine the stress and strain ranges created by thermal loading and these ranges are used in the crack initiation and growth models to estimate fatigue life.
4

Besel, Michael, and Angelika Brueckner-Foit. "Lifetime Prediction of Components Including Initiation Phase." In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-90710.

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The lifetime distribution of a component subjected to fatigue loading is calculated using a micro-mechanics model for crack initiation and a fracture mechanics model for crack growth. These models are implemented in a computer code which uses the local stress field obtained in a Finite Element analysis as input data. Elemental failure probabilities are defined which allow to identify critical regions and are independent of mesh refinement. An example is given to illustrate the capabilities of the code. Special emphasis is put on the effect of the initiation phase on the lifetime distribution.
5

Lecheb, S., T. Djedid, A. Chellil, A. Nour, M. Cherigui, and H. Kebir. "Fatigue crack initiation and vibration prediction life of turbine blade." In 2013 5th International Conference on Modeling, Simulation and Applied Optimization (ICMSAO 2013). IEEE, 2013. http://dx.doi.org/10.1109/icmsao.2013.6552600.

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6

Karimzadanzabi, A., A. Fahimifar, M. Khalili, and P. Ghayour. "Crack Initiation Prediction in Rock Samples using Digital Image Correlation." In 84th EAGE Annual Conference & Exhibition. European Association of Geoscientists & Engineers, 2023. http://dx.doi.org/10.3997/2214-4609.2023101258.

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Rinehart, Adam J., and Peter B. Keating. "Fatigue Life Prediction for Short Dents in Petroleum Pipelines." In ASME 2002 Pressure Vessels and Piping Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/pvp2002-1268.

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Pipeline dent fatigue behavior has been shown to be strongly dependent upon dent length and external force dent restraint characteristics. Full-scale laboratory tests have shown that short dents that are unrestrained by an external force typically experience fatigue cracking in the dent periphery outside of the dent contact region. A fatigue life prediction method for short dents is presented here. In order to assess method accuracy, predictions are made for cases in which fatigue life has been measured experimentally. The predictions account for both crack initiation life and crack propagation life. Stress concentration values used in the predictions are determined using finite element modelling on a case-by-case basis for comparison purposes. Appropriate crack initiation life estimates, stress intensity factor predictions, and crack propagation models are taken from existing literature. Predicted and measured fatigue lives are compared for the cases studied.
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Tarnowski, K. M., C. M. Davies, G. A. Webster, and D. W. Dean. "Predictions of Creep Crack Initiation Periods in Pre-Compressed 316H Stainless Steel." In ASME 2013 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/pvp2013-97769.

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Pre-compression of 316H stainless steel significantly alters its tensile, uniaxial creep and crack growth behaviour. It has previously been shown that reliable and conservative creep crack initiation predictions can generally be obtained for as-received 316H stainless steel using a variety of prediction methods. Given the changes in material behaviour caused by pre-compression, this paper applies similar prediction methods to pre-compressed 316H stainless steel at 550°C. Several procedures are available for estimating creep crack initiation time periods. The suitability of a procedure depends on the availability of the necessary material data. The procedures considered in this paper include the use of the creep fracture mechanics parameter C*, the crack opening displacement concept, the sigma-d approach and the time dependent failure assessment diagram. Creep crack growth tests have been performed on compact tension specimens manufactured from 316H stainless steel which was uniformly pre-compressed by 4% and 8% at room temperature. For each test, the time for creep crack initiation to occur was recorded. Predicted creep crack initiation times have been compared with the experimentally determined values. Comparisons with as-received material are also included. For pre-compressed material, conservative creep crack initiation predictions were only consistently achieved using steady state creep crack growth rates predicted from C*. This is a significant difference to as-received material for which conservative predictions were generally obtained by a variety of methods. At this time, there is only a limited set of pre-compressed data making it difficult to draw firm conclusions about the appropriateness of the various creep crack initiation prediction methods. The differences in the results between the pre-compressed and as-received material do however highlight the need for further tests on pre-compressed material.
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CARRARO, PAOLO, SIMONETTO MIRKO, LUCIO MARAGONI, and MARINO QUARESIMIN. "DAMAGE EVOLUTION IN CROSS-PLY LAMINATES UNDER VARIABLE AMPLITUDE CYCLIC LOADINGS." In Thirty-sixth Technical Conference. Destech Publications, Inc., 2021. http://dx.doi.org/10.12783/asc36/35891.

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Predicting the initiation and propagation of multiple off-axis cracks in multidirectional laminates under cyclic loadings is essential in a stiffness-driven design approach. Even under a constant amplitude cyclic load, the multiple crack initiation represents always an inherently variable amplitude (VA) problem. Indeed, the initiation of cracks causes a stress re-distribution so that each point in a laminate is subjected to a stress state that changes continuously during the fatigue life. At present, no models or experimental evidences on the crack initiation phenomenon under VA loadings are available in the literature. Crack density prediction models usually rely on a simple linear damage accumulation rule, even if its validity has not been proved yet. In this work, two types of fatigue tests were carried out on glass/epoxy cross-ply laminates under VA two-block loadings: 1) Initially, the number of cycles in the first block was chosen low enough to prevent the initiation of transverse cracks in the first block; then the load was changed and the crack initiation phenomenon was characterized in the second block. 2) Then, two block loadings were applied on other specimens, with a high enough number of cycles in the first block to promote the initiation of multiple cracks; the crack density evolution was thus characterized in both blocks. A model recently developed by the authors was applied to the experimental data, revealing the suitability of the linear damage accumulation rule under block loadings, at least from a phenomenological point of view.
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Munson, Kurt, Jeff Mentley, and Andrew Halfpenny. "A Finite Element Based Methodology for Combined Crack Initiation and Crack Growth Prediction in Welded Structures." In WCX SAE World Congress Experience. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2019. http://dx.doi.org/10.4271/2019-01-0537.

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Звіти організацій з теми "Crack initiation prediction":

1

Yuasa, Hitoshi, Kazuya Okubo, Toru Fujii, and Tsuyoshi Nakatsuji. Prediction of Crack Initiation for One-Piece Type Brake Disc for Motorcycles under Overload Condition. Warrendale, PA: SAE International, October 2005. http://dx.doi.org/10.4271/2005-32-0047.

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2

Chen, Weixing. PR-378-083601-R02 Effect of Pressure Fluctuations on Growth Rate of Near-Neutral pH SCC. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), August 2017. http://dx.doi.org/10.55274/r0011010.

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This report summarizes the work completed in Phase 1 and Phase 2 of PRCI SCC-2-12 project: Effect of Pressure Fluctuations on Growth Rate of Near-Neutral pH SCC. The following two insights from the two-phase PRCI SCC 2-12 project can be proven to be the most important: 1) The identification of three types of pressure fluctuations and their different susceptibility to crack growth; 2) The importance of load interaction effects during variable amplitude pressure fluctuations in the prediction of crack growth rate. The work has enabled us to divide near-neutral pH SCC cracking into the following two governing processes: the dissolution growth process for crack initiation and early stage crack growth and the hydrogen facilitated fatigue growth after crack initiation and dormancy. The first process features very high rate of dissolution at the pipe surface caused by various forms of galvanic processes and reduced crack growth in the depth direction leading to crack dormancy. The hydrogen facilitated fatigue growth process has been determined to be predominant for the crack growth after crack initiation and dormancy. Depending on the location of pipeline sections, the pressure fluctuations could be characterized into three types based on the relative pressure levels of the large loading events and the minor cycles. It has been determined from extensive experimental investigations that crack growth under Type I pressure fluctuations with frequent underload cycles, which is often found within 30 km downstream of a compressor station, can be enhanced significantly because of effects of load interactions of variable amplitude of cyclic loading. The load-interactions during SCC of pipeline steels in near-neutral pH environments are complex, which include both the time independent load-history interactions and the time dependent load interactions related to the rate of diffusion of hydrogen and hydrogen embrittlement in response to various scenarios of pressure fluctuations. Based on the experimental findings obtained, strategies for mitigating near-neutral pH crack initiation and crack growth during field operations have been proposed. The experimental findings have also been integrated into a software, namely the Pipe-Online, for making crack growth and remaining life prediction. For the purpose of capturing all the crack-growth contributing events of pressure fluctuations for life predictions, a method of recording pressure fluctuations has also been developed.
3

Arumugam, Udayansankar, Pablo Cazenave, and Ming Gao. PR-328-133702-R01 Study of the Mechanism for Cracking in Dents in a Crude Oil Pipeline. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), February 2019. http://dx.doi.org/10.55274/r0011556.

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Phase one report: Crack fields (colonies) in dents are often observed in liquid pipe lines. Because of their colonial appearance, these cracks in dents are often thought to be associated with stress corrosion cracking (SCC). However, a recent full-scale dent fatigue testing under a PRCI mechanical damage program showed that crack colonies in dents can be produced by fatigue. This observation facilitated PRCI to launch a further study of the cracking mechanism in dents using samples extracted from a liquid pipeline. A total of 6 pipe samples containing dent with crack/metal loss were investigated. Evidences from this investigation showed that cracks in dents are aligned in an axial direction with appearance similar to crack colony. Fractographic analyses showed that the mechanism for cracking in these dents was fatigue. No evidence of stress corrosion cracking (SCC) was found. Fractographic analyses also showed that cracks in the colony were associated with a corrosion pit, suggesting corrosion pits are the initiation sites for fatigue crack. A combination of corrosion pitting and fatigue crack growth is the overall mechanism for the observed cracking, that is, corrosion may be the first degrading mechanism followed by the fatigue crack growth. Based on the understanding of the mechanism for cracking, a review is given to the currently available pit-to-crack transition and overall life prediction models. Applicability and limitations of these models to cracks in dent are discussed. Gaps and areas for further study are discussed. An example of rate competing between pit and crack growth and for overall life estimate is illustrated. In this report, sample selection and the approach used in this investigation are presented first. The findings from fractographic analysis are summarized. Currently available modelling efforts for pitto-fatigue are reviewed. Gaps and further research areas are discussed.
4

Christman. L51577 Prediction of SCC Susceptibility Based on Mechanical Properties of Line Pipe Steels. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), August 1988. http://dx.doi.org/10.55274/r0010278.

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If a relationship between the deformation properties of a line pipe steel and its stress-corrosion cracking resistance can be established, then steels may be selected or designed for improved stress-corrosion resistance, based on their mechanical properties. Benefit: In this research program three line pipe steels, removed from long-term service, were examined to determine if there is a correlation between their mechanical properties and stress-corrosion cracking resistance. The hypothesis was that the steel with the greatest tendency for strain hardening, under cyclic and monotonic stress conditions would also have the highest threshold stress for stress-corrosion crack initiation. This hypothesis was verified by the laboratory experiments, which showed the steel with the greatest tendency for strain hardening to have the highest resistance to stress-corrosion. Two other steels, with distinctly lower resistance to plastic deformation, had lower threshold stresses for stress-corrosion. This observation is consistent with the present concept of stress-corrosion crack growth, which holds that crack tip dissolution, and hence crack propagation, occurs because localized plastic deformation ruptures passive films or prevents film formation resulting in crack growth. Result: The cyclic strain behavior of these three steels is consistent with their monotonic stress-strain curves. Both Steels A and B showed a point of extreme strain as the cyclic stress was increased. Their monotonic stress-strain curves both showed well pronounced yield points above which a considerable strain accompanied a small stress increment (low strain hardening). For both steels the rapid increase in cyclic strain occurred at approximately the elevated temperature yield point (\45 ksi for Steel A
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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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Chen, Weixing. PR378-173601-Z01 Effect of Pressure Fluctuations on the Growth Rate of Near-Neutral pH SCC. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), July 2021. http://dx.doi.org/10.55274/r0012112.

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This report summarizes the work completed in PRCI SCC-2-12A project: The Effect of Pressure Fluctuations on the Growth Rate of Near-Neutral pH SCC, which is Phase 3 of the work on the same subject of investigation. The following insights from the current phase of the PRCI SCC-2-12A project are thought to be the most important: - Near neutral pH crack initiation is pressure-fluctuation dependent. Severe pressure fluctuations accelerate the fracture and spallation of mill scale on the pipeline steel surfaces, making it harder to initiate SCC cracks from the bottom of pits that are developed at flawed mill scale sites. On the other hand, the presence of a primer layer before application of the protective coating preserves the mill scale on the pipe steel surface and promotes crack initiation. - The early-stage crack growth primarily features crack length extension on the pipe surface but limited crack growth in the depth direction. Three different mechanisms of crack length extension have been identified, including that determined by the geometry of coating disbondment, a chaotic process of crack coalescence, and the ability of existing cracks to induce further crack initiation and growth. This latter process is pressure-fluctuation sensitive. - A complete set of equations governing crack growth in Stage 2 has been established based on experimental specimens with surface cracks under mechanical loading conditions realistic to pressure fluctuations during the operation of oil and gas pipelines. - The contribution to crack growth by direct dissolution of the steel at the crack tip has been determined, which has been found to be crack depth-dependent and pressure-fluctuation-sensitive. Gas pipelines operated under high mean pressure show higher rates of dissolution. - The severity of crack growth and the accuracy of the predictive model can be significantly affected by crack tip morphology, either sharp or blunt, and this would yield different threshold values for Stage 2 crack growth and therefore different lengths of remaining life. - Full scale testing was performed and has validated the crack growth models contained herein. - The PipeOnline software has been revised to incorporate the new experimental results obtained from the current PRCI SCC 2-12A project. This PipeOnline software was previously developed from the two earlier phases of the PRCI project.
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Keeney-Walker, J., B. R. Bass, and J. D. Landes. An investigation of crack-tip stress field criteria of predicting cleavage-crack initiation. Office of Scientific and Technical Information (OSTI), September 1991. http://dx.doi.org/10.2172/5205137.

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Cox, James V., John M. Emery, Luke N. Brewer, Earl David, Jr Reedy, Joseph David Puskar, Timothy James Bartel, Remi P. M. Dingreville, James W. ,. III Foulk, Corbett Chandler Battaile, and Brad Lee Boyce. Microstructure-based approach for predicting crack initiation and early growth in metals. Office of Scientific and Technical Information (OSTI), September 2009. http://dx.doi.org/10.2172/1001018.

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Shim, D. J., Gery Wilkowski, Mohammed Uddin, Sureshkumar Kalyanam, and P. Mincer. PR-276-094509-R01 Develop Fracture Initiation Criteria for High-Strength Steel Line Pipe Phase II. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), August 2013. http://dx.doi.org/10.55274/r0010072.

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This report summarizes the major findings from a PRCI Project on developing fracture initiation criteria for axial flaws (both through-wall and surface flaws) in high-strength line-pipe materials. This work was originally done on the basis to see if improvements were needed for higher-grade steels, but interestingly there were several outcomes that affect predictions for all piping steels. One of the outcomes of this work is a new correlation between Charpy USE and J-R curve for high-strength materials. Although it is based on limited data, it was demonstrated that there is significant difference compared to the existing correlation. Another interesting finding is the effect of the internal patch on burst pressure of axial through-wall-cracked pipe test. Careful experimental and detailed finite element analyses showed patching affects burst pressure by at least 10-percent which affects the leak-rupture boundary. For axial surface-cracked pipes, the effect of crack shape on the crack-driving force was investigated. Finally, it was demonstrated that the actual axial surface-cracked pipe bulging factor is considerably lower than bulging factor empirically derived at Battelle in the 1970s. If past bulging factor is used for subcritical crack growth (e.g., for SCC or fatigue analyses), the crack growth and start of ductile tearing can be significantly overpredicted. Overall, J-T analysis provided the most accurate results when proper crack-driving forces and J-R curves were used (both for axial through-wall-cracked pipe and axial surface-cracked pipe). This report also includes recommendations for future work.
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Chan, Kwai S. Development of a Physically-Based Methodology for Predicting Material Variability in Fatigue Crack Initiation and Growth Response. Fort Belvoir, VA: Defense Technical Information Center, December 2004. http://dx.doi.org/10.21236/ada429459.

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