Journal articles: '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.

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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.

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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.

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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.

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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.

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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.

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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.

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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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Kumar, R. Ramesh, P. N. Dileep, S. Renjith, and G. Venkateswara Rao. "A Simple Method for Theoretical Prediction of Fracture Toughness of Multilayered Composites." Advanced Composites Letters 12, no. 4 (July 2003): 096369350301200. http://dx.doi.org/10.1177/096369350301200403.

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Intralaminar fracture toughness of a fibre-reinforced angle ply and cross ply laminates are generally obtained by testing compact tension specimen and theoretically predicted using the well-known MCCI approach. The crack initiation direction, which is treated as a branch direction for the theoretical prediction, is an apriori. A conservative estimation on the toughness value obtained by considering branch crack angle corresponding to each fibre orientation in a laminate shows a gross error with respect to test data. In the present study a new criterion for the prediction of crack initiation angle is arrived at based on Tsai-Hill minimum strain energy density criterion. This shows a very good agreement with test data available in literature on fracture toughness of various multilayered composites with large size cracks with a/w ≥ 0.3. It is interesting to note that in a multilayered composite a simple method of prediction in which crack initiation direction is assumed to be the fibre orientation that is close to the initial crack direction gives a good estimation of the intralaminar fracture toughness.

12

Osterstock, Stephane, Christian F. Robertson, Maxime Sauzay, Suzanne Degallaix, and Veronique Aubin. "Prediction of the Scatter of Crack Initiation under High Cycle Fatigue." Key Engineering Materials 345-346 (August 2007): 363–66. http://dx.doi.org/10.4028/www.scientific.net/kem.345-346.363.

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Under fatigue loading, the number of cycles to failure and its associated scatter increase when the loading level decreases. The High-Cycle Fatigue (HCF) regime is thus characterized by a large scatter in the number of cycles to failure [1]. Cracks initiation represents an important part of the lifetime of the structures. A stochastic method is used to study the fatigue crack initiation prediction in the 316L austenitic stainless steel. The present work proposes to show that this scatter can be attributed to the random orientation of individual grains, which influences the crack initiation localization. The stresses in grains are determined by finite element computations (FEM [2]), using a configuration representative of a polycrystalline aggregate. This approach takes into account the crystallographic orientations of the grains in the aggregate as well as the deformation incompatibilities between neighbouring grains due to crystalline anisotropic elasticity and elasticplasticity [3]. Then, the scatter of the number of cycles to crack initiation is derived from the FEM stress fields using two fatigue crack initiation criteria: an usual one, Mura’s criterion [4] and a more recent one [5], based on Discrete Dislocation Dynamics (DDD) simulations and taking into account plastic slips, cross slip and stress tensor components.

13

Bensussan, P., E. Maas, R. Pelloux, and A. Pineau. "Creep Crack Initiation and Propagation: Fracture Mechanics and Local Approach." Journal of Pressure Vessel Technology 110, no. 1 (February 1, 1988): 42–50. http://dx.doi.org/10.1115/1.3265566.

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Both the initiation and the propagation of macroscopic creep cracks have been studied in 316-L austenitic stainless steel, and, for comparison purposes, in 2219-T851 aluminum alloy. These alloys are, respectively, creep-ductile and creep-brittle. This difference in behavior is explained in terms of fracture mechanics concepts applied to creeping solids. The inability of fracture mechanics in providing unique correlations with K, C*, etc. . . for all the stages of both creep crack initiation and propagation is pointed out. Life prediction schemes using local rather than global fracture criteria are presented. A model based on creep ductility exhaustion concepts and the stress fields obtained by fracture mechanics is shown to provide good predictions for 316-L. Finite element analysis coupled to continuum damage mechanics is found to describe creep crack initiation in 2219-T851.

14

Kedir, Yahiya Ahmed, and Hirpa G. Lemu. "Prediction of Fatigue Crack Initiation under Variable Amplitude Loading: Literature Review." Metals 13, no. 3 (February 27, 2023): 487. http://dx.doi.org/10.3390/met13030487.

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Metallic materials are widely employed in engineering constructions, and one of the most common failure mechanisms in metals is fatigue failure. Even though metal fatigue has been studied for almost 160 years, many problems remain unsolved. Fatigue in metal occurs when the metallic material is subjected to varying loads, resulting in failure due to damage accumulation. The fatigue process consists of a buildup of damage that leads to crack initiation, followed by a period of crack growth until the critical flaw size is reached. The sum of a start phase and a propagation phase represents the total life. To better understand the fatigue phenomenon at its different stages and predict the fatigue life, various types of prediction models have been developed and reported in the literature. This paper reviewed the different models that include microstructure scale parameters that can be used to predict how fatigue cracks start under variable amplitude loading, including the Modified Tanaka-Mura Model, Acoustic Second Harmonic Generation, and the Probability of Crack Initiation on Defects. For perfect life prediction under variable amplitude loading, a stress-based approach, a strain-based approach, and a continuum damage mechanics approach are reviewed. The purpose of this paper is to get overview of the current state of approaches to the life prediction of fatigue crack initiation with variable amplitude. Finally, gaps in knowledge about the prediction of fatigue crack initiation under variable loading at high temperatures are pointed out.

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Kutin, Marina, Ivana Vasovic, Mirko Maksimovic, and Marko Ristic. "Prediction of Residual Life Assesment Using Thermography and Crack Growth Analysis." Applied Mechanics and Materials 157-158 (February 2012): 202–9. http://dx.doi.org/10.4028/www.scientific.net/amm.157-158.202.

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The most important characteristics for service safety of complex metal structures are those describing crack initiation and growth caused by static or dynamic, variable loading. Crack initiation and growth is subject of numerous investigations by different methods. The paper shows the possibility of applying infrared thermography to the problems of fracture mechanics. The main aim of testing was to qualitative relate the temperature changes of the spacemen measured by infrared thermography with the evaluation of fatigue cracks in steel specimen. Based on the distribution of temperature on the surface of the sample, during the action of force, the spread of plastic zones and crack tip are determined. The increase of temperature produced by the plastic deformation at the crack tip has been measured by infrared camera Thermal CAM SC640, FLIR Systems. SE(B) specimens were tested in three-point bending (TPB), following the procedures of ASTM E1820, on electrical mechanical testing machine with crack tip opening displacement (CTOD) control, at room temperature. Numerical simulation of stress distribution on the same model under same condition is presented, too. The results showed that thermography is a method suitable for monitoring and prediction of crack initiation and growth, as well as critical stress in elastic and elastic-plastic deformations. Fatigue crack growth behaviour of cracked TPB specimen made of S355 J2 G3 steel using Paris relation is considered.

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Tohgo, Keiichiro, Hiromitsu Suzuki, and Yoshinobu Shimamura. "Monte Carlo Simulation of Stress Corrosion Cracking in Structural Metal Materials Taking Account of Surface Crack Effects." Key Engineering Materials 353-358 (September 2007): 1068–71. http://dx.doi.org/10.4028/www.scientific.net/kem.353-358.1068.

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According to laboratory accelerated test data, stress corrosion cracking (SCC) in structural metal materials occurs by initiation and coalescence of micro cracks, subcritical crack propagation and multiple large crack formation or final failure under the combination of materials, stress and corrosive environment. In this paper, a Monte Carlo simulation for the process of SCC has been proposed based on the stochastic properties of micro crack initiation and fracture mechanics concept for crack coalescence and propagation. The emphasis in the model is put on the influence of the semi-elliptical surface cracks. The numerical examples for a sensitized stainless steel type 304 indicate the applicability of the present model to the prediction of the SCC behavior in real structures.

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Xue, Gaoge, Takashi Nakamura, Nao Fujimura, Kosuke Takahashi, and Hiroyuki Oguma. "Initiation and Propagation Processes of Internal Fatigue Cracks in β Titanium Alloy Based on Fractographic Analysis." Applied Sciences 11, no. 1 (December 25, 2020): 131. http://dx.doi.org/10.3390/app11010131.

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Uniaxial fatigue tests were conducted for a β titanium alloy Ti-22V-4Al up to a very high cycle fatigue (VHCF) regime. The initiation and propagation processes of the internal fatigue cracks were investigated using 3D fractographic analysis. Multiple facets were observed at the crack initiation site. Three facet initiation models were proposed based on the surface appearances and the 3D facet bonding patterns of the multiple facets, and the major facet was determined to be the true crack initiation site. Using the size of the major facet, a Tanaka–Akiniwa model, which can determine the material constants for the Paris law using only conventional fatigue tests, was applied to reveal the propagation process of the internal cracks. A reverse fatigue life prediction was also conducted to evaluate the accuracy of the material constants obtained using the Tanaka–Akiniwa model. When the facet initiation models were applied, the predictions showed less deviation and better agreement than when the facet initiation process was not considered. The findings of this study indicate that the formation of multiple facets in β titanium alloys is sequential rather than simultaneous.

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Tehrani, P. Hosseini, and M. Saket. "Fatigue crack initiation life prediction of railroad." Journal of Physics: Conference Series 181 (August 1, 2009): 012038. http://dx.doi.org/10.1088/1742-6596/181/1/012038.

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Besel, Michael, and Angelika Brueckner-Foit. "Lifetime Prediction of Components Including Initiation Phase." Journal of Engineering for Gas Turbines and Power 129, no. 2 (August 5, 2006): 542–48. http://dx.doi.org/10.1115/1.2436569.

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The lifetime distribution of a component subjected to fatigue loading is calculated using a micromechanics 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 us 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.

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Carter, Jace A., and Tarun Goswami. "Probabilistic Risk Assessment for Life Extension of Turbine Engine Rotors." Metals 12, no. 8 (July 28, 2022): 1269. http://dx.doi.org/10.3390/met12081269.

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Maintaining the component service life beyond its historical limits requires the ability to accurately quantify component reliability and address the uncertainties in material responses. A probabilistic method for predicting the total fatigue life was developed and applied to determine the probability of failure of a Ti-6Al-4V turbine disk component. The total fatigue life incorporates a dual mechanism approach including the crack initiation life and propagation life while simultaneously determining the associated initial flaw sizes. A microstructure-based model was employed to address the uncertainties in material response and relate the crack initiation life with crack size. The propagation life was characterized using both small and large crack growth models to ensure accurate fatigue life prediction. Fatigue life predictions were found to correlate with experimental data at high stress levels. The risk assessment can be used to estimate the expected initial crack sizes from variability in material properties, which can further be used to establish an enhanced inspection planning.

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Seibi, Abdennour C., and Sam Y. Zamrik. "Prediction of Crack Initiation Direction for Surface Flaws Under Biaxial Loading." Journal of Pressure Vessel Technology 125, no. 1 (January 31, 2003): 65–70. http://dx.doi.org/10.1115/1.1521712.

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This paper presents a simple method based on the strain energy density factor ΔS to study the fatigue characteristics of rhombic plates with induced angled flaws under biaxial stress field. The paper discusses in detail the procedures followed to predict the fracture crack initiation angle, θo, as a function of induced crack angle, β, the path of the crack trajectory at the initial stage of fracture and develop an expression for the crack growth rate. This method assumes that the crack extends in a radial direction and that the initial fracture crack angle, θo, is obtained by maximizing the hoop stress along a circumference of a radius r. Expressions for the stress-state near the crack tip were developed for computing the crack trajectory and the strain energy density factor. The crack trajectory path was estimated by computing the new values of the crack angle and a fictitious crack length. These computed values were in turn used to determine the strain energy density factor. The developed method revealed two important observations: i) The crack trajectory was in close agreement with the experimental data for the first 20% of the lifetime to failure, ii) the crack propagation rate is dependent on the crack angle using the stress intensity factor and exhibited no variation with respect to the crack angle when the strain energy density factor is used.

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Wong, Boon, and D. E. Helling. "A Mechanistic Model for Solder Joint Failure Prediction Under Thermal Cycling." Journal of Electronic Packaging 112, no. 2 (June 1, 1990): 104–9. http://dx.doi.org/10.1115/1.2904349.

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A mechanistic model for eutectic Pb/Sn solder life predictions has been developed and applied to leadless surface mount solder joints. This model can quantitatively describe both crack initiation and crack propagation processes in the solder. There are four parts to this model: a crack initiation model, a crack propagation model [1], a microstructural coarsening model and an analysis of the deformation in the solder during thermal cycling. By merging these models together, it is possible to predict the time to crack initiation and the time to failure of these solder joints. Solder joint life predictions show good agreement with data obtained on thermally cycled surface mount leadless chip resistors.

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Cheng, W., H. S. Cheng, T. Mura, and L. M. Keer. "Micromechanics Modeling of Crack Initiation Under Contact Fatigue." Journal of Tribology 116, no. 1 (January 1, 1994): 2–8. http://dx.doi.org/10.1115/1.2927042.

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Using dislocation pileup theory, a model is given for the prediction of crack initiation life under contact fatigue. Near surface crack initiation is investigated by introducing the sliding contact boundary condition. Crack initiation originated at the surface and substrate are treated as extreme cases. The new model physically explains how a surface crack can be initiated and shows that the surface crack initiation life should be shorter than the subsurface crack initiation life under the same stress amplitude conditions. A discussion is given about the influence of residual stress, hardness, temperature, irreversibility of the plastic deformation, as well as other parameters that affect the crack initiation life. Preliminary comparisons show that the new model agrees well with the experimental observations of surface and near surface crack initiation.

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Demir, O. "Prediction of crack initiation angle in brittle structures containing inclined cracks." Mechanics of Solids 56, no. 6 (November 2021): 1066–75. http://dx.doi.org/10.3103/s0025654421060054.

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Shao, Wei, Xiaoqing He, Danda Shi, and Wenjin Zhu. "Prediction of Crack Width in RC Piles Exposed to Local Corrosion in Chloride Environment." Materials 16, no. 19 (September 26, 2023): 6403. http://dx.doi.org/10.3390/ma16196403.

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A novel prediction model for crack development of reinforced concrete (RC) piles with localized chloride corrosion in the marine environment is proposed. A discrete method is used to solve the corrosion pit radius model and a crack extension model is developed to investigate the initiation and extension of cracks. The maximum corrosion degree of the reinforced concrete pile is predicted according to the limit crack criterion, and finally, a sensitivity analysis is carried out on the important parameters of crack extension. The results show that the radius of the corrosion pit, the depth corrosion pit, and the cross-sectional area loss of reinforcement gradually increase as the corrosion level increases. The loss of the local reinforcement section at crack initiation increases with the increase in the ratio of concrete cover to initial diameter and increases with the increase in the pitting factor. The required pit depth for reinforcement cracking increases with the increase in the ratio of concrete cover thickness to diameter. The loss of the cross-sectional area of reinforcement and the radius of the corrosion pit increase with the increase in the initial diameter of reinforcement. Increasing the pitting factor can reduce the pit depth and make the crack width develop faster before reaching the limit crack width. Increasing the concrete cover thickness can provide an improvement in the propagation of cracks. A comparative analysis shows that the localized corrosion pattern is more in conformity with marine engineering practice.

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Tan, Wen Feng. "Fatigue Crack Initiation Life Prediction of Backup Roll of Four High Mill." Advanced Materials Research 197-198 (February 2011): 1469–72. http://dx.doi.org/10.4028/www.scientific.net/amr.197-198.1469.

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By using of closed-form solution for predicting fatigue crack initiation life of a beam subjected to the transverse bending load in large range damage， fatigue crack initiation life of backup roll of four high mill is predicted. The method adopted in this paper is simple and effective. A new method is provided for predicting fatigue crack initiation life backup roll of four high mill.

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Hou, Hengjun, Zhengwei Zhu, Bo Wang, and Wenhao Zhou. "A Practical Model Study on the Mechanism of Clay Landslide under Static Loads: From the Perspective of Major Crack–Stress–Displacement." Applied Sciences 12, no. 7 (March 22, 2022): 3224. http://dx.doi.org/10.3390/app12073224.

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Stability assessment of cracked clay slopes has been a research hotspot in geotechnical engineering in recent years. The assessment work should include crack initiation/development and stability evaluation. However, there has been no universal method for predicting crack evolution until now. In addition, scholars have paid little attention to the coupling relationship between the evolution of cracks and the progressive failure process of macroscopic clay slopes and have seldom studied the ubiquitous diagonal cracks in clay slopes. In this work, the stress mechanism for initiation and development of major cracks was derived based on unsaturated soil mechanics and critical state soil mechanics considering the tensile, compression, and shear properties of clay. The correctness of the proposed theory was verified by constructing a large-scale, arc-shaped slip surface clay slope model. In the model test, earth pressure cells and displacement gauge were employed to monitor development of stresses within the clay slope and horizontal displacement of the slope shoulder, respectively, under the set load sequence. The results showed that the stress mechanism proposed in this paper could judge not only vertical cracks but also diagonal cracks. Horizontal stresses near the primary crack appeared as a result of stress saltation. The locations and depths of the major cracks could be determined by analyzing the differences in horizontal stress between adjacent measuring points under the same load step. The development of major crack–horizontal stress–displacement had intrinsic consistency, and the initiation and development of major cracks aggravated changes in displacement and horizontal stresses. The perspective of major crack–stress–displacement is helpful to wholly grasp the progressive failure process of cracked clay slopes and provide a reference for prediction of clay landslides.

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Lin, Yulong, Shourong Liu, Xueyan Zhao, Enrong Mao, Chao Cao, and C. Steve Suh. "Fatigue life prediction of engaging spur gears using power density." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 232, no. 23 (January 8, 2018): 4332–41. http://dx.doi.org/10.1177/0954406217751557.

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The high cycle fatigue performance of an input spur gear pair found in the gearbox of a 4LZ-2 combined harvester with a maximum walking power of 15 kW is investigated. A three-dimensional finite element model of the two engaging spur gears is developed to estimate the fatigue life of the pinion gear subject to bending induced crack initiation and propagation. The critical point of the pinion gear is obtained along with the associated bending stress-time history. The novel concept of power density is applied to the finite element result to correlate fatigue crack initiation and subsequent crack growth with the number of loading cycles undergone. After the location of crack initiation is identified, fatigue crack propagation is modelled using linear elastic fracture mechanics. The estimated fatigue life of the pinion gear is 886 h. A fatigue test rig is employed to physically demonstrate the feasibility of the power density concept for predicting gear fatigue life. It is shown that the power density concept is preferred over the Miner rule for higher accuracy in fatigue life prediction.

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Matsueda, Takahiro, Masayuki Ishida, and Koshiro Mizobe. "Distribution of Aspect Ratio of Fatigue Crack at Notch Root Depending on Crack Initiation Point of Annealed Steel, JIS S45C." Materials Science Forum 893 (March 2017): 240–44. http://dx.doi.org/10.4028/www.scientific.net/msf.893.240.

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Aspect ratio of crack is one of key factors of fatigue strength prediction in engineering design and civil structures using fracture mechanics. Their empirical shapes are changed by stress concentration. However, it was not clear how stress concentration affects empirical results including crack shape and size. In this study, in order to investigate the relationship between stress concentration and crack geometry, the aspect ratio of cracks at notch root was observed and discussed. We succeeded to capture two important relationships which are between stress concentration and crack shape, and between crack initiation point at notch root and crack shape, respectively.

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Lamacq, V., M. C. Dubourg, and L. Vincent. "Crack Path Prediction Under Fretting Fatigue—A Theoretical and Experimental Approach." Journal of Tribology 118, no. 4 (October 1, 1996): 711–20. http://dx.doi.org/10.1115/1.2831599.

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In this paper, the direction of crack growth under fretting fatigue loading is studied through an experimental and theoretical approach. The experimental work enabled the fretting conditions to be known and the site of initiation and crack trajectory to be viewed; theoretical work permitted a prediction of those processes. Fretting wear and fretting fatigue loadings induce non-proportional mixed mode loading at the tip of the cracks initiated within the contact zone. The classical criteria predicting the direction of crack growth cannot account for the non-proportional loading. Tests were carried out to study the cracking phenomena under cumulative effects of contact and external loadings, i.e., fretting fatigue loading. The fretting contact between the two contacting bodies is modeled to evaluate the operating contact loading conditions. The response of the cracked body is determined in terms of stress intensity factors using the continuous distribution of dislocations theory coupled with a unilateral contact analysis with friction. The angle of crack extension is then predicted, at different stages of crack life, according to a new approach. The correlation of the predicted angle of crack extension with the experimental observation enables the conclusion that, under fretting fatigue loading, cracks propagate by a mode I process.

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Fezazi, Amina Ismahène, Belaïd Mechab, Salem Mokadem, and Boualem Serier. "Numerical prediction of the ductile damage for axial cracks in pipe under internal pressure." Frattura ed Integrità Strutturale 15, no. 58 (September 25, 2021): 231–41. http://dx.doi.org/10.3221/igf-esis.58.17.

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This study presents a numerical prediction of the ductile damage for axial cracks in pipe subjected to internal pressure. The three dimensional finite element methods used to evaluate the J-integral. The effect of the external radius (Rext),the thickness (t), length crack (a) , the applied loads (P) and the crack position of the pipes has studied. The Monte Carlo method was used to determine the probabilistic characteristics of the J-integral. It’s also used later to predict the failure probability based on initiation of the crack growth. We note that the crack size and the geometries of the pipe are an important factor influencing on the durability of the pipe.

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Cui, Xiaodong, Eugene Fang, and Jim Lua. "A discrete crack network toolkit for Abaqus for damage and residual strength prediction of laminated composites." Journal of Composite Materials 51, no. 10 (July 18, 2016): 1355–78. http://dx.doi.org/10.1177/0021998316659914.

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The main objective of this article is to exploit a phantom paired element based discrete crack network toolkit for predicting the damage progression and residual strength of laminated composites without and with a hole under tension and compression. Both intra-ply matrix cracking and inter-ply delamination are considered under a co-simulation framework in the discrete crack network toolkit. A mesh-independent kinematic description of discrete matrix cracks is accomplished via user-defined phantom paired solid elements to capture the initiation and evolution of fiber orientation dependent matrix cracking. In-ply matrix crack initiation is realized by inserting a crack along the fiber direction when a matrix driven failure criterion is satisfied and a cohesive injection along the matrix crack interface is applied to account for energy dissipation during matrix crack opening. The delamination failure mode is characterized by applying Abaqus’ cohesive interaction at ply interfaces. The non-linear shear behavior is introduced by employing a power law based curve-fit model and the fiber failure is described using a continuum damage mechanics based model. Both the blind and recalibrated predictions are performed for specimens of three different layups under the Air Force Tech Scout 1 program. The predicted damage progression and the load displacement curves are compared with the testing results provided by the Air Force Research Laboratory.

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Sahadi, J. V., D. Nowell, and R. J. H. Paynter. "Prediction of fatigue crack initiation under biaxial loading." Frattura ed Integrità Strutturale 11, no. 41 (June 28, 2017): 106–13. http://dx.doi.org/10.3221/igf-esis.41.15.

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Ringsberg, J. "Life prediction of rolling contact fatigue crack initiation." International Journal of Fatigue 23, no. 7 (August 2001): 575–86. http://dx.doi.org/10.1016/s0142-1123(01)00024-x.

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LIU, Y., B. STRATMAN, and S. MAHADEVAN. "Fatigue crack initiation life prediction of railroad wheels." International Journal of Fatigue 28, no. 7 (July 2006): 747–56. http://dx.doi.org/10.1016/j.ijfatigue.2005.09.007.

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Oterkus, Erkan, and Erdogan Madenci. "Peridynamic Theory for Damage Initiation and Growth in Composite Laminate." Key Engineering Materials 488-489 (September 2011): 355–58. http://dx.doi.org/10.4028/www.scientific.net/kem.488-489.355.

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A recently introduced nonlocal peridynamic theory removes the obstacles present in classical continuum mechanics that limit the prediction of crack initiation and growth in materials. Furthermore, damage growth in composites involves complex and progressive failure modes. Current computational tools are incapable of predicting failure in composite materials mainly due to their mathematical structure. However, the peridynamic theory removes these obstacles by taking into account non-local interactions between material points. This study presents an application of the peridynamic theory for predicting damage progression from a central crack in fiber reinforced composite plates subjected to uniaxial tension loading.

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Wang, Zan Zhi. "Short Crack Propagation Law and Fatigue Life Prediction Method for Structural Alloy Steel." Advanced Materials Research 197-198 (February 2011): 1400–1405. http://dx.doi.org/10.4028/www.scientific.net/amr.197-198.1400.

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35CrMo and 42CrMo are the two main structural alloy steels in China, and are widely used in making important structural components subjected to heavy loads. In order to search after their fatigue properties under cyclic loads, 33 specimens were tested, under different stress level and different stress ratio from each other, to observe their crack initiation lives and the failure lives, together with the growing short crack lengths at various cycles. All tests were conducted using the MTS 810-22 material testing system. Based on the results from the tests, the relationships between the maximum stress range at crack tip and the number of cycles prior to crack initiation were determined, and in the meanwhile, the small crack propagation laws and the threshold stresses for fatigue crack initiation were obtained. In the end, the fatigue life prediction method for the two structural alloy steels was carried out.

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Hannes, Dave, and B. Alfredsson. "Rolling Contact Fatigue Crack Growth Prediction by the Asperity Point Load Mechanism." Key Engineering Materials 488-489 (September 2011): 101–4. http://dx.doi.org/10.4028/www.scientific.net/kem.488-489.101.

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The crack path and growth life of surface initiated rolling contact fatigue was investigated numerically based on the asperity point load mechanism. Data for the simulation was captured from a gear contact with surface initiated rolling contact fatigue. The evolvement of contact parameters was derived from an FE contact model where the gear contact had been transferred to an equivalent contact of a cylinder against a plane with an asperity. Crack propagation criteria were evaluated with practically identical crack path predictions. It was noted that the trajectory of largest principal stress in the uncracked material could be used for the path prediction. The mode I fracture mechanism was applicable to the investigated rolling contact fatigue cracks. The simulated path agreed with the spall profile both in the entry details as in the overall shape, which suggested that the point load mechanism was valid not only for initiation but also for rolling contact fatigue crack growth. Different equivalent stress intensity factor ranges were used to estimate the fatigue life, which agreed with the life of the investigated gear wheels.

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Lindström, Thomas, Robert Eriksson, Daniel Ewest, Kjell Simonsson, Jan-Erik Lundgren, and Daniel Leidermark. "Crack initiation prediction of additive manufactured ductile nickelbased superalloys." MATEC Web of Conferences 165 (2018): 04013. http://dx.doi.org/10.1051/matecconf/201816504013.

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A model to predict crack initiation life of an additive manufactured nickel-based superalloy similar to Hastelloy X subjected to low-cycle fatigue loading at room temperature has been developed, taking material anisotropy into account. An anisotropic constitutive model based on the Hill yield criterion was developed, with linear kinematic hardening up to a saturation value of the back stress, above which the material behaves perfectly plastic. Low-cycle fatigue experiments has been performed on additive manufactured smooth bars with two different build orientations, with an angle of 0⁰ and 90⁰ relative to the building platform. A total of 20 experiments at room temperature were conducted with different strain ranges and R-values. To predict the crack initiation life of the specimens, a model based on the Smith-Watson-Topper (SWT) parameter has been established, where ten of the specimens were used to calibrate the initiation model, and the remaining specimens were used for validation. Using this model, the obtained crack initiation life agrees well with the experiments.

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Christodoulou, Peter I., and Alexis T. Kermanidis. "A Combined Numerical–Analytical Study for Notched Fatigue Crack Initiation Assessment in TRIP Steel: A Local Strain and a Fracture Mechanics Approach." Metals 13, no. 10 (September 27, 2023): 1652. http://dx.doi.org/10.3390/met13101652.

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In the fatigue design of metallic components using the safe-life approach, fatigue crack initiation as a development of slip systems at the nanoscale, followed by microstructurally short crack growth, is critical for the onset of structural failure. The development of reliable analytical tools for the prediction of crack initiation, although very complex due to the inherent multiscale fatigue damage processes involved, is important for promoting a more sophisticated design but, more importantly, enhancing the safety in regard to fatigue. The assessment of fatigue crack initiation life at the root of a V-shaped notch is performed by implementing a local strain and a fracture mechanics concept. In the low cycle fatigue analysis, the finite element method is used to determine the local stress–strain response at the notch root, which takes into account elastoplastic material behavior. Fatigue crack initiation is treated as the onset of a short corner crack by incremental damage accumulation and failure of a material element volume at the notch root. The finite element results are compared against established methodologies such as the Neuber and strain energy density methods. In the fracture mechanics approach, fatigue crack initiation is treated as the onset and propagation of a corner crack to a finite short crack. Fatigue experiments in two different transformation-induced plasticity (TRIP) steels were conducted to evaluate the analytical predictions and to determine the physical parameters for the definition of crack initiation. The analytical results show that the finite element method may be successfully implemented with existing fatigue models for a more accurate determination of the local stress–strain behavior at the notch tip in order to improve the assessment of fatigue crack initiation life compared to the established analytical methodologies.

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Xuanbao, Wang, Si Liang, Wang Jiaxing, Wang Zilong, Wang Shuo, Hu Ping, and Duanmu Fanshun. "Durability analysis of large and medium-sized unmanned aerial vehicles based on load spectrum and probabilistic fracture mechanics." Journal of Physics: Conference Series 2764, no. 1 (May 1, 2024): 012015. http://dx.doi.org/10.1088/1742-6596/2764/1/012015.

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Abstract The analysis of unmanned aerial vehicle (UAV) durability is crucial for cost-effective repair and maintenance. Assessing the degree of damage and predicting the economic lifespan of a UAV is a critical component of its design and use. To evaluate the durability of large and medium-sized UAVs, data is gathered, and simulations are performed under real-world working conditions. The analysis includes creating a crack growth model for small cracks and determining the distribution of crack sizes, estimating the distribution of Time to Crack Initiation (TTCI), and calculating the general Equivalent Initial Flaw Size (EIFS) distribution. The results obtained from these analyses meet the UAV’s flight hour requirements and help to predict its economic life. This prediction is also beneficial for managing and maintaining the UAV’s life cycle.

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Deng, Tie Song, Xin Zhao, Bing Wu, Wei Li, Ze Feng Wen, and Xue Song Jin. "Prediction of Crack Initiation of Rail Rolling Contact Fatigue." Applied Mechanics and Materials 344 (July 2013): 75–82. http://dx.doi.org/10.4028/www.scientific.net/amm.344.75.

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A plain-strain finite element (FE) model of the rail is developed by ABAQUS. The 1070 rail steel is considered in the model by Jiang and Sehitoglu's cyclic plastic constitutive equation. The wheel-rail rolling contact is represented by a moving load applied on the contact surface. Based on the FE results the initiation of rolling contact fatigue (RCF) crack is further evaluated by Jiang's fatigue model. Effects of the rail material inner defect and the friction coefficient are also investigated. The results show that the stress-strain state of the rail surface material becomes stable after about thirty passages. The maximum residual stress and strain are located in the subsurface. The life of a defected rail can be as low as 1/27~1/17 of a qualified rail, and the most probable location for crack initiation is highly dependent on the inner defect. The fatigue life is found to considerably decrease with the friction coefficient, while the location of crack initiation and its direction of propagation are less affected.

43

Xue, Gang, Ren Fu Wang, Wang Ping Deng, Hong Yuan Fang, and Jian Guo Yang. "Low-Cycle Fatigue Behavior of Large-Size Dissimilar Steel Welded Tube-Plate Structure." Materials Science Forum 704-705 (December 2011): 780–85. http://dx.doi.org/10.4028/www.scientific.net/msf.704-705.780.

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Based on the FEM analysis of the distributions and varieties of the stresses and the strains of the large-size dissimilar steel welded tube-plate structure under cyclic loading, the fatigue crack initiation sites of this structure were predicted. The low-cycle fatigue test was performed to verify the prediction and to study the cracks propagating paths as well. The results indicated that the weld toes linked to the two surfaces of the plate were the positions with the peak values of the maximum stress and the stress amplitude. The plastic deformations in the first loading cycle introduced the tensile-compressive repeated stress cycle at the weld toes during the subsequent loading cycles. It induced the fatigue cracks initiating at the weld toes linked to the two surfaces of the plate respectively. After initiating from the surfaces the cracks propagated along the fusion lines with a short distance then turn into the base metal in the sections vertical to the surfaces. The depth of the crack initiating from the compressed surface was shorter than the one from the tensioned surface.

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Han, Zhongying, Xiaoguang Huang, and Zhicheng Yang. "Effect of Al–Zn Alloy Coating on Corrosion Fatigue Behavior of X80 Riser Steel." Materials 12, no. 9 (May 9, 2019): 1520. http://dx.doi.org/10.3390/ma12091520.

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This paper presents a corrosion fatigue cyclic failure test for X80 steel, which has arc sprayed with an Al–Zn coating in natural seawater under different stress levels. We found that the Al–Zn coating can significantly improve the corrosion fatigue resistance and slow the crack initiation of X80 steel. The effect of the Al–Zn coating on the corrosion fatigue crack initiation is mainly attributed to its physical isolation, cathodic protection and residual prestress while the effect on crack propagation is due to its inhibition of the formation and evolution of secondary cracks. Moreover, according to the test results, a new life prediction model for corrosion fatigue based on the damage evolution law is proposed and the effect of corrosion–fatigue coupling damage in the proposed model is also considered.

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Halford, G. R., T. G. Meyer, R. S. Nelson, D. M. Nissley, and G. A. Swanson. "Fatigue Life Prediction Modeling for Turbine Hot Section Materials." Journal of Engineering for Gas Turbines and Power 111, no. 2 (April 1, 1989): 279–85. http://dx.doi.org/10.1115/1.3240249.

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This paper presents a summary of the life prediction methods developed under the NASA Lewis Research Center’s Hot Section Technology (HOST) program. A major objective of the fatigue and fracture efforts under the HOST program was to significantly improve the analytic life prediction tools used by the aeronautical gas turbine engine industry. This has been achieved in the areas of high-temperature thermal and mechanical fatigue of bare and coated high-temperature superalloys. Such technical improvements will eventually reduce life cycle costs. The cyclic crack initiation and propagation resistance of nominally isotropic polycrystalline alloys and highly anisotropic single crystal alloys have been addressed. A sizeable data base has been generated for three alloys [cast PWA 1455 (B–1900 + Hf), wrought Inconel 718, and cast single-crystal PWA 1480] in bare and coated conditions. Two coating systems, diffusion aluminide (PWA 273) and plasma-sprayed MCrAlY overlay (PWA 286), were employed. Life prediction modeling efforts were devoted to creep-fatigue interaction, oxidation, coatings interactions, multiaxially of stress-strain states, mean stress effects, cumulative damage, and thermomechanical fatigue. The fatigue crack initiation life models developed to date include the Cyclic Damage Accumulation (CDA) Model of Pratt & Whitney and the Total Strain Version of Strainrange Partitioning (TS-SRP) of NASA Lewis for nominally isotropic materials, and the Tensile Hysteretic Energy Model of Pratt & Whitney for anisotropic superalloys. The fatigue model being developed by the General Electric Company is based upon the concepts of Path-Independent Integrals (PII) for describing cyclic crack growth under complex non-linear response at the crack tip due to thermomechanical loading conditions. A micromechanistic oxidation crack extension model has been derived by researchers at Syracuse University. The models are described and discussed in the paper. Only limited verification has been achieved to date as several of the technical programs are still in progress and the verification tasks are scheduled, quite naturally, near the conclusion of the program. To date, efforts have concentrated on developement of independent models for cyclic constitutive behavior, cyclic crack initiation, and cyclic crack propagation. The transition between crack initiation and crack propagation has not been thoroughly researched as yet, and the integration of these models into a unified life prediction method has not been addressed.

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Shao, Peng, Yong Zhang, Wen Ming Gao, and Yong Qiang Liu. "Dynamic Response of Intermittent Jointed Rock Mass Subjected to Blast Waves." Key Engineering Materials 306-308 (March 2006): 1415–20. http://dx.doi.org/10.4028/www.scientific.net/kem.306-308.1415.

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The propagation of blast waves in intermittent jointed rock masses will result in a complex interaction between propagating waves and rock joints. Such being the case, the analysis of dynamic response of rock masses is important to rock engineering design and stability prediction. In this paper, the fracture process of intermittent jointed rock mass subjected to blast waves and initial static field, including wing crack initiation, propagation and arrest, is analyzed using linear superposition principle and sliding crack model. Crack initiation conditions and propagation lengths under incident P-waves is put forward, and the kinking effect of propagating wing cracks subjected to S-wave is also discussed. Additional, it is demonstrated that crack arrest is controlled by static field. In order to validate the correctness of dynamic response analysis, experimental investigations were performed using lucite specimens, and the experimental results show good agreement with the analytical results.

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Yahiaoui, R., R. Noureddine, and B. Ait Saadi. "A STOCHASTIC MODEL FOR CRACK INITIATION LIFE PREDICTION OF AN AUSTENITIC STAINLESS STEEL UNDER CONSTANT AMPLITUDE LOADING." Journal of the Serbian Society for Computational Mechanics 14, no. 1 (June 30, 2020): 29–36. http://dx.doi.org/10.24874/jsscm.2020.14.01.03.

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Predicting crack initiation life (CIL) of a mechanical component or a structure in service remains difficult since the crack formation process is of stochastic nature. To ensure a high level of safety and reliability, it is essential to have an appropriate probability distribution law of the CIL to ensure that cracks can be detected before reaching a critical length. In the present study, a stochastic model is used to predict the number of cycles corresponding to the formation of a crack 500 Î¼m long resulted from the nucleation, growth, and coalescence of multiple microcracks. The model is applied in the case of a 316L austenitic stainless steel for different plastic strain ranges.

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Zavattieri, Pablo D. "Modeling of Crack Propagation in Thin-Walled Structures Using a Cohesive Model for Shell Elements." Journal of Applied Mechanics 73, no. 6 (December 23, 2005): 948–58. http://dx.doi.org/10.1115/1.2173286.

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A cohesive interface element is presented for the finite element analysis of crack growth in thin specimens. In this work, the traditional cohesive interface model is extended to handle cracks in the context of three-dimensional shell elements. In addition to the traction-displacement law, a bending moment-rotation relation is included to transmit the moment and describe the initiation and propagation of cracks growing through the thickness of the shell elements. Since crack initiation and evolution are a natural outcome of the cohesive zone model without the need of any ad hoc fracture criterion, this model results in automatic prediction of fracture. In particular, this paper will focus on cases involving mode I/III fracture and bending, typical of complex cases existing in industrial applications in which thin-walled structures are subjected to extreme loading conditions (e.g., crashworthiness analysis). Finally, we will discuss how the three-dimensional effects near the crack front may affect the determination of the cohesive parameters to be used with this model.

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Matsueda, Takahiro. "A New Evaluation Method to Calculate Crack Initiation Limit with Modified Crack Aspect Ratios in Notched Specimen of Carbon Steels." Applied Mechanics and Materials 563 (May 2014): 80–84. http://dx.doi.org/10.4028/www.scientific.net/amm.563.80.

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Aspect ratio is a key factor to calculate stress intensity factor (SIF) K using fracture mechanics. While cracks are approximated to be semi-circle or semi-ellipse for simply evaluation, their shapes are changed by stress concentration source. In this study, a new method to modify aspect ratio of a crack at a notch root is proposed. Modified aspect ratio in this method succeeded to decrease prediction error of fatigue crack initiation stress, σw1 which was calculated using experimental value.

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Swaminathan, V. P., N. S. Cheruvu, and A. Saxena. "Life Assessment of an HP-IP Rotor Under Creep Service Conditions." Journal of Engineering for Gas Turbines and Power 112, no. 2 (April 1, 1990): 237–42. http://dx.doi.org/10.1115/1.2906169.

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A CrMoV high and intermediate-pressure (HP-IP) rotor exhibited in-service cracking in the blade groove walls. Cracks initiated from a notch and propagated under creep conditions to a depth of 0.255 in. (6.5 mm). Since the unit was base loaded, the contribution of cyclic loading (startups and shutdowns) was not significant. The total life of the groove walls is predicted by applying a life prediction approach that accounts for both crack initiation and propagation. Crack initiation life is based on short-term creep tests extrapolated to long times using a time-temperature parameter. Crack propagation time is estimated using a newly developed time-dependent fracture mechanics concept. A parameter Ct is used to express the crack growth rate under creep loading conditions. Pertinent material properties such as creep deformation and creep crack growth rate were obtained by testing the material from the subject rotor. The results obtained by this analysis show that about 50 percent of the estimated life was spent in crack propagation. Predicted service life time compares very favorably with the actual operating life of the rotor.

Journal articles on the topic 'Crack initiation prediction'

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