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1
Tumanov, N. V. "Steady fatigue crack growth: micromechanism and mathematical modeling." Industrial laboratory. Diagnostics of materials 84, no. 11 (December 3, 2018): 52–69. http://dx.doi.org/10.26896/1028-6861-2018-84-11-52-69.
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A universal energy-intensive micromechanism of periodic splitting-rupture (PSR) is revealed which proceeds at the front of the fatigue cracks in metallic materials, providing their steady growth, forming T-shaped crack tip and striated microrelief of the fracture surface. The PSR micromechanism is caused by a critical (prior to fracture) fragmentated structure formed in the area of the crack front where the material is subjected to multiple and increasing plastic deformation. This universal prefracture structure is a final stage of the evolution of the deformational structures emerged in front of the fatigue crack at the stage of stable crack growth in metallic materials with different initial structural states. This is responsible for universality of PSR micromechanism and fatigue striations. Fatigue striations are the traces of extending crack front with T-shaped tip formed during brittle transverse microsplitting along the overstressed boundaries of critical fragmentated structure. Based on 3D finite element modeling of the stress-strain state in front of the cracks with T-shaped tip, it is established that the value and the location of maximum of normalized in-plain stresses (acting in front of crack tip in the plane of crack along the normal to its front) are close or coincide for the cracks of different configuration and different types of tensile load under condition that splitting in the T-shaped crack tip is considerably less than the crack length. Taking into account the PSR micromechanism and asymptotic stress distribution in front of T-shaped crack tip the physically based mathematical model for steady fatigue crack growth is developed along with the techniques for prediction of steady fatigue crack growth in full-scale components under simple and complex loading cycles.
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GRAY, L. J., D. O. POTYONDY, E. D. LUTZ, P. A. WAWRZYNEK, L. F. MARTHA, and A. R. INGRAFFEA. "CRACK PROPAGATION MODELING." Mathematical Models and Methods in Applied Sciences 04, no. 02 (April 1994): 179–202. http://dx.doi.org/10.1142/s021820259400011x.
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In this paper, we review recent advances in mathematical and computer science techniques for modeling crack propagation in solids. The fracture mechanics aspect of this problem is attacked by boundary integral equation methods, in particular the use of hypersingular integral equations for analyzing crack geometries. Key issues in the development of a software system capable of efficient crack propagation studies are also discussed. As an illustration of these techniques, calculations analyzing crack growth in a fuel door hinge on the Space Shuttle are presented.
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Altabey, Wael A., Mohammad Noori, Tianyu Wang, Ramin Ghiasi, Sin-Chi Kuok, and Zhishen Wu. "Deep Learning-Based Crack Identification for Steel Pipelines by Extracting Features from 3D Shadow Modeling." Applied Sciences 11, no. 13 (June 29, 2021): 6063. http://dx.doi.org/10.3390/app11136063.
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Automatic crack identification for pipeline analysis utilizes three-dimensional (3D) image technology to improve the accuracy and reliability of crack identification. A new technique that integrates a deep learning algorithm and 3D shadow modeling (3D-SM) is proposed for the automatic identification of corrosion cracks in pipelines. Since the depth of a corrosion crack is below the surrounding area of the crack, a shadow of the crack is projected when the crack is exposed under light sources. In this study, we analyze the shadow areas of cracks through 3D shadow modeling (3D-SM) and identify the evolving cracks through the shape analysis of the shadows. To denoise the 3D images, the connected domain analysis is implemented so that the shadow groups of the evolving cracks can be retained and the scattered shadow groups that occur due to insignificant defects can be eliminated. Moreover, a novel deep neural network is developed to process the 3D images. The proposed automatic crack identification method successfully processes the 3D images efficiently and accurately diagnoses the corrosion cracks. Experimental results show that the proposed method achieves satisfactory performance with 93.53% accuracy and a 92.04% regression rate.
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Wang, Zhaohua, Yichang (James) Tsai, and Menghua Ding. "Use of Crack Characteristics in Crack Sealing Performance Modeling and Network-Level Project Selection." Transportation Research Record: Journal of the Transportation Research Board 2612, no. 1 (January 2017): 11–19. http://dx.doi.org/10.3141/2612-02.
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Crack sealing (CS) and crack filling (CF) are commonly used crack treatment methods. However, the study of their performance is still very limited, making it difficult for highway agencies to systematically and optimally select network-level CS-CF projects within available budgets. To address this issue, a generalized performance model for CS-CF–treated pavements is proposed. Detailed crack characteristics—including crack type, density, and width—are employed in the model. In the proposed performance model, crack density related to three types of cracks (transverse cracks, nonwheelpath longitudinal cracks, and wheelpath longitudinal cracks) is used to determine performance gain. Two discount functions are incorporated to consider the negative impact caused by alligator cracks and cracks that are very tight or very wide. The proposed model is instantiated and estimated using the practices of the Georgia Department of Transportation on CS and CF and the department’s pavement distress survey protocol. The case study—which uses three-dimensional laser data collected from a 1-mi pavement section on State Route 26 (US-80) near Savannah, Georgia, from 2011 to 2016—validates the feasibility and reasonableness of the model. An integer programming method is formulated for network-level CS-CF project selection. The testing results of 53 pavement segments show that the model and programming method can be used to select CS-CF projects within budget constraints while maximizing the length-weighted average performance gain. The proposed performance model and integer programming method show promise for use in incorporating CS and CF into a highway agency’s pavement management system. Conclusions and recommendations are offered.
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Wang, K. F., Y. Q. Wang, B. L. Wang, and L. Zheng. "A double cantilever beam incorporating cohesive crack modeling for superconductors." Modern Physics Letters B 34, no. 15 (March 30, 2020): 2050166. http://dx.doi.org/10.1142/s0217984920501663.
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In this paper, a double cantilever beam (DCB) specimen incorporating cohesive crack is developed for superconductors which have potential applications in high temperature superconducting cables in space solar power station. The cohesive interface is introduced along the crack front of the DCB model under electromagnetic force. The load-separation relation (i.e. the crack opening displacement) is used as the fracture mechanics parameter and the corresponding curves during fracture process are obtained and verified by the finite element numerical method. Results show that the presence of tensile electromagnetic force makes crack propagate easily. Superconductors with small cracks have good adaptability to the oscillation of magnetic fields while that with large cracks are easier to fracture during the descent of the magnetic field. In addition, the ductility ratio of the cohesive interface can significantly increase the fracture strength. The length of fracture zone decreases as the crack length increases.
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Gavrilov, A. A., G. I. Grebenyuk, V. I. Maksak, and N. A. Morozov. "Crack modeling of metal rod eigen-frequencies." Vestnik Tomskogo gosudarstvennogo arkhitekturno-stroitel'nogo universiteta. JOURNAL of Construction and Architecture 23, no. 2 (April 30, 2021): 56–64. http://dx.doi.org/10.31675/1607-1859-2021-23-2-56-64.
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The paper presents the development of approaches to the crack detection in metal rod structures based on the analysis of the lowest eigen-frequency modes. Full-scale experiments and numerical calculations are carried out, and the obtained results are compared. A vibration analyzer is used for full-scale experiments, and numerical calculations are performed by using Autodesk Inventor. With regard to the internal friction, the antinodes of various vibration forms were identified using a specially developed program. The model includes sensors for the the field experiment as masses affecting the frequency-response characteristics. The dependences are obtained for eigen-frequencies in the presence of cracks and for the crack locations. The polynomial dependences of the crack location on the lowest eigen-frequency modes of the rod can be used to analyze the crack position of in cantilever beams.
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Hu, Jiang, and Suhua Wu. "Statistical modeling for deformation analysis of concrete arch dams with influential horizontal cracks." Structural Health Monitoring 18, no. 2 (March 10, 2018): 546–62. http://dx.doi.org/10.1177/1475921718760309.
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Several concrete dams all over the world exhibit severe cracks. It is very important to investigate the influence of cracks on the long-term behavior of dam structures to ensure safe operation. The interpretation of measured dam displacements is usually based on statistical hydrostatic-seasonal-time and hydrostatic-thermal-time models. The main purpose of this article is to present a statistical hydrostatic-thermal-crack-time model to interpret displacements of concrete arch dams with influential horizontal cracks. The hydrostatic-thermal-crack-time model is applied to analyze the Chencun dam, an arch–gravity dam with a large-scale horizontal crack on the downstream face. The crack stretches horizontally across most of the dam blocks. Its crack mouth opening displacement had been continually increasing even after reinforcement treatment, accompanied by abnormal deformation characteristics of the arch–cantilever system. A three-dimensional finite element model, containing the pre-existing crack using special gap elements, is built to reproduce the structural response, assess the contribution of the crack on the registered movements, and obtain the relationship between the crack mouth opening displacement and the dam crest displacement. Based on this, the hydrostatic-thermal-CMOD-time model considering crack mouth opening displacement is developed. Compared with the traditional models, the hydrostatic-thermal-crack-time model is expected to provide a better fit accuracy. The results also show that the crack and the corresponding reinforcement measure have a significant effect on the deformation behavior of the dam. This can provide some useful indications for concrete structures with similar problems.
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Takagaki, Masakazu, and Toshiya Nakamura. "Fatigue Crack Modeling and Simulation Based on Continuum Damage Mechanics." Journal of Pressure Vessel Technology 129, no. 1 (March 10, 2006): 96–102. http://dx.doi.org/10.1115/1.2388993.
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Numerical simulation of fatigue crack propagation based on fracture mechanics and the conventional finite element method requires a huge amount of computational resources when the cracked structure shows a complicated condition such as the multiple site damage or thermal fatigue. The objective of the present study is to develop a simulation technique for fatigue crack propagation that can be applied to complex situations by employing the continuum damage mechanics (CDM). An anisotropic damage tensor is defined to model a macroscopic fatigue crack. The validity of the present theory is examined by comparing the elastic stress distributions around the crack tip with those obtained by a conventional method. Combined with a nonlinear elasto-plastic constitutive equation, numerical simulations are conducted for low cycle fatigue crack propagation in a plate with one or two cracks. The results show good agreement with the experiments. Finally, propagations of multiply distributed cracks under low cycle fatigue loading are simulated to demonstrate the potential application of the present method.
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Li, Qingbo, Nengxiong Xu, Weifeng Wan, and Yazhe Li. "Modeling of Shear Crack Propagation in Rock Masses Using Mesh-Free LRPIM." Advances in Civil Engineering 2021 (March 25, 2021): 1–13. http://dx.doi.org/10.1155/2021/6654812.
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The modeling of shear cracks in materials is critical in various engineering applications, such as the safety analysis of concrete structures and stability analysis of rock slopes. Based on the idea of Goodman element, the elastic-plastic constitutive model of the shear cracks is derived, and the elastic-plastic analysis of shear crack propagation is realized in the local radial basis point interpolation method (LRPIM). This method avoids the loss of accuracy caused by the mesh in the analysis of fracture propagation, and the crack propagation of rock brittle material is simulated. The investigation indicates that (1) the LRPIM results are close to the FDM results, which demonstrates that it is feasible to analyze shear cracks in rock masses. (2) Compared with the results of the built-in oblique crack model, when the LRPIM is used to analyze crack propagation, the results are close to the experimental results, showing that the LRPIM can model shear crack propagation in a rock mass. (3) The propagation path using the LRPIM is not sufficiently smooth, which can be explained as the crack tip stress and strain not being sufficiently accurate and still requiring further improvement.
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Pais, Jorge. "The Reflective Cracking in Flexible Pavements." Romanian Journal of Transport Infrastructure 2, no. 1 (July 1, 2013): 63–87. http://dx.doi.org/10.1515/rjti-2015-0012.
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Abstract Reflective cracking is a major concern for engineers facing the problem of road maintenance and rehabilitation. The problem appears due to the presence of cracks in the old pavement layers that propagate into the pavement overlay layer when traffic load passes over the cracks and due to the temperature variation. The stress concentration in the overlay just above the existing cracks is responsible for the appearance and crack propagation throughout the overlay. The analysis of the reflective cracking phenomenon is usually made by numerical modeling simulating the presence of cracks in the existing pavement and the stress concentration in the crack tip is assessed to predict either the cracking propagation rate or the expected fatigue life of the overlay. Numerical modeling to study reflective cracking is made by simulating one crack in the existing pavement and the loading is usually applied considering the shear mode of crack opening. Sometimes the simulation considers the mode I of crack opening, mainly when temperature effects are predominant.
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Wang, Shui Lin, Xia Ting Feng, Yu Yong Jiao, Xiu Run Ge, and Chun Guang Li. "Manifold Method and Its Applications for Modeling Fracturing in Solids." Key Engineering Materials 306-308 (March 2006): 511–16. http://dx.doi.org/10.4028/www.scientific.net/kem.306-308.511.
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A numerical technique based on using manifold elements in finite element method, for modeling propagation of arbitrary cracks in solids, is described. When the region with crack(s)is subjected to external loading and the crack(s) starts to extend, the crack growth may intersect boundaries of nearby finite elements. Those intersected finite elements are replaced by manifold elements. The technique, by which the initial finite element mesh can be kept unchanged during the processes of crack propagation, is called manifold elements in finite element method. The crack growth is governed by the theories of linear elastic fracture mechanics. The stress intensity factors are computed by a contour integral technique and crack trajectory is determined by applying the maximum tangential stress criterion. Finally, test examples are given to verify the new method and the predicted trajectories are compared to experimentally obtained crack growth paths with good agreements
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Veluri, Badrinath, and Henrik Myhre Jensen. "Modeling Delamination of Interfacial Corner Cracks in Multilayered Structures." Key Engineering Materials 525-526 (November 2012): 509–12. http://dx.doi.org/10.4028/www.scientific.net/kem.525-526.509.
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Multilayered electronic components, typically of heterogeneous materials, delaminate under thermal and mechanical loading. A phenomenological model focused on modeling the shape of such interface cracks close to corners in layered interconnect structures for calculating the critical stress for steady-state propagation has been developed. The crack propagation is investigated by estimating the fracture mechanics parameters that include the strain energy release rate, crack front profiles and the three-dimensional mode-mixity along the crack front. The developed numerical approach for the calculation of fracture mechanical properties has been validated with three-dimensional models for varying crack front shapes. A custom quantitative approach was formulated based on the finite element method with iterative adjustment of the crack front to estimate the critical delamination stress as a function of the fracture criterion and corner angles.
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Pryl, Dobromil, Jitka Mikolášková, and Radomír Pukl. "Modeling Fatigue Damage of Concrete." Key Engineering Materials 577-578 (September 2013): 385–88. http://dx.doi.org/10.4028/www.scientific.net/kem.577-578.385.
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Numerical model for fatigue crack propagation within the framework of finite element smeared crack analysis is presented. It concentrates on modeling of fatigue behavior of material under tensile load which causes initiation and growth of cracks in concrete. The fatigue material model is an extension of existing static three-dimensional fracture-plastic material model, and as such it has been implemented into the ATENA Finite Element software package. The developed model has been used to model experiments with high-cycle loading of three point bending concrete specimens tested by collaborating institutions. Analysis results are compared to the measurements.
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Słowik, M., and P. Smarzewski. "Numerical Modeling Of Diagonal Cracks In Concrete Beams." Archives of Civil Engineering 60, no. 3 (September 1, 2014): 307–22. http://dx.doi.org/10.2478/ace-2014-0021.
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AbstractIn the paper, the method of a numerical simulation concerning diagonal crack propagation in concrete beams was presented. Two beams reinforced longitudinally but without shear reinforcement were considered during the Finite Element Method analysis. In particular, a nonlinear method was used to simulate the crack evaluation in the beams. The analysis was performed using the commercial program ANSYS. In the numerical simulation, the limit surface for concrete described by Willam and Warnke was applied to model the failure of concrete. To solve the FEM-system of equations, the Newton-Raphson method was used. As the results of FEM calculations, the trajectories of total stains and numerical images of smeared cracks were obtained for two analyzed beams: the slender beam S5 of leff = 1.8 m and the short beam S3k of leff = 1.1 m. The applied method allowed to generate both flexural vertical cracks and diagonal cracks in the shear regions. Some differences in the evaluation of crack patterns in the beams were observed. The greater number of flexural vertical cracks which penetrated deeper in the beam S5 caused the lower stiffness and the greater deformation in the beam S5 compared to the short beam S3k. Numerical results were compared with the experimental data from the early tests performed by Słowik [3]. The numerical simulation yielded very similar results as the experiments and it confirmed that the character of failure process altered according to the effective length of the member. The proposed numerical procedure was successfully verified and it can be suitable for numerical analyses of diagonal crack propagation in concrete beams.
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He, Wen Tao, Jing Xi Liu, and De Xie. "Two-Dimensional Crack Growth Simulation under Mixed-Mode Loading." Applied Mechanics and Materials 577 (July 2014): 301–4. http://dx.doi.org/10.4028/www.scientific.net/amm.577.301.
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In this paper, an efficient simulation program (FCG-System) is proposed to simulate 2D fatigue crack growth under mixed-mode loading conditions. The simulation is basically an incremental crack extension procedure. An object-oriented modeling frame is proposed for simulating fatigue crack growth of complex structures. The modeling frame is developed in the context of the commercial FE code ABAQUS, utilizing Python language and ABAQUS Scripting Interface (ASI). The highly automatic finite element simulation method is not only used for a single crack tip, but also has been extended to the system of interactive multiple cracks. The robustness and the accuracy of the new simulation code will be shown by two examples, including single crack growth and multiple cracks growth. Those applications indicate that the implementation of the FCG-System, as proposed herein, can be a useful tool for this class of fatigue crack growth.
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Thomas, D. J., and R. C. Wetherhold. "Modeling the Effective Elastic Behavior of a Transversely Cracked Laminated Composite." Journal of Engineering for Gas Turbines and Power 120, no. 1 (January 1, 1998): 191–98. http://dx.doi.org/10.1115/1.2818075.
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The solution for the stress state present in the vicinity of transverse matrix cracks within a composite laminate is typically obtained by assuming a regular crack spacing geometry for the problem and applying a shear-lag analysis. In order to explore the validity of this underlying assumption, the probability density function for the location of the next transverse matrix crack within a crack bounded region is examined. The regular crack spacing assumption is shown to be reasonable from an engineering point of view. Continuing with this assumption, a generalized shear-lag model for multilayer, off-axis laminates subjected to full in-plane loads is developed. This model is used to quantitatively evaluate the effective elastic properties of the damaged material. The results are applicable to materials such as ceramic matrix or polymer matrix unidirectional fiber systems where damage in the form of transverse matrix cracks arises.
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Ortiz, K., and A. S. Kiremidjian. "A Stochastic Model for Fatigue Crack Growth Rate Data." Journal of Engineering for Industry 109, no. 1 (February 1, 1987): 13–18. http://dx.doi.org/10.1115/1.3187085.
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This paper summarizes a new approach to the probabilistic modeling of fatigue crack growth. The material’s resistance to fatigue crack growth is modeled as a stochastic process, which varies randomly along the crack path. Model parameters are determined through time analysis of fatigue crack growth rate data. Predictions of the statistics of crack growth are excellent, especially for small cracks.
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Falkenberg, Rainer. "Simulation of Environmentally-Assisted Material Degradation by a Thermodynamically Consistent Phase-Field Model." Key Engineering Materials 713 (September 2016): 38–41. http://dx.doi.org/10.4028/www.scientific.net/kem.713.38.
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Environmentally-assisted material degradation involves mass transport and mechanical processes interacting in the material. A well-known example is hydrogen-induced stress-corrosion cracking. One major challenge within this scope is the quantification of the coupling mechanisms in question. The computational modeling of environmentally-assisted cracks is the key objective ofthis investigation and realised within the theory of gradient-extended dissipative continua with length-scales. The modeling of sharp crack discontinuities is replaced by a diffusive crack model based onthe introduction of a crack phase-field to maintain the evolution of complex crack topologies. Withina thermodynamical framework allowing for mechanical and mass transport processes the crack phase-field is capable to model crack initiation and propagation bythe finite element method. As complexcrack situations such as crack initiation, curvilinear crack patterns and crack branching are usuallyhard to realise with sharp crack models, they can be assessedwithout the requirement of a predefinedcrack path within this method. The numerical modeling of a showcase demonstrates a crack initiationas well as a crack propagation situation with respect to the determination of stress-intensity factors; acrack deviation situation with a curvilinear crack path is modeled by the introduction of a geometricalperturbation and a locally enhanced species concentration
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Ramos‐Martínez, Jaime, Andrey A. Ortega, and George A. McMechan. "3-D seismic modeling for cracked media: Shear‐wave splitting at zero‐offset." GEOPHYSICS 65, no. 1 (January 2000): 211–21. http://dx.doi.org/10.1190/1.1444712.
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Splitting of zero‐offset reflected shear‐waves is measured directly from three‐component finite‐difference synthetic seismograms for media with intersecting vertical crack systems. Splitting is simulated numerically (by finite differencing) as a function of crack density, aspect ratio, fluid content, bulk density, and the angle between the crack systems. The type of anisotropy symmetry in media containing two intersecting vertical crack systems depends on the angular relation between the cracks and their relative crack densities, and it may be horizontal transverse isotropy (HTI), tetragonal, orthorhombic, or monoclinic. The transition from one symmetry to another is visible in the splitting behavior. The polarities of the reflected quasi‐shear waves polarized perpendicular and parallel to the source particle motion distinguish between HTI and orthorhombic media. The dependence of the measured amount of splitting on crack density for HTI symmetry is consistent with that predicted theoretically by the shear‐wave splitting factor. In orthorhombic media (with two orthogonal crack systems), a linear increase is observed in splitting when the difference between crack densities of the two orthogonal crack systems increases. Splitting decreases nonlinearly with the intersection angle between the two crack systems from 0° to 90°. Surface and VSP seismograms are simulated for a model with several flat homogeneous layers, each containing vertical cracks with the same and with different orientations. When the crack orientation varies with depth, previously split shear waves are split again at each interface, leading to complicated records, even for simple models. Isotropic and anisotropic three‐component S-wave zero‐offset sections are synthesized for a zero‐offset survey line over a 2.5-D model of a carbonate reservoir with a complicated geometry and two intersecting, dipping crack sets. The polarization direction of the fast shear wave, propagating obliquely through the cracked reservoir, is predicted by theoretical approximations for effective properties of anisotropic media with two nonorthogonal intersecting crack sets.
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S.Y., Wee, R. A. @. R. B. Chan, and Teo H.W. "Potential Modeling Of Pavement Deterioration Rate Due To Cracking." Journal of Civil Engineering, Science and Technology 1, no. 1 (August 1, 2009): 1–6. http://dx.doi.org/10.33736/jcest.62.2009.
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Bitumen pavements tend to crack at some point of their life under the combined action of traffic and the environment. These cracks are defects in the pavement surfacing which weakens the pavement and allows water to penetrate and cause further weakening. Once initiated, cracking usually increases in extent, severity and intensity, leading eventually to pavement failure. Cracking has therefore been an important indicator for road pavement maintenance. In view of the extensive road network in Malaysia covering more than 80,000 kilometers in total, the government has to spend huge sums of money on the repair of cracks under its annual road maintenance program. However, the resurfacing works have not always been successful and cracks tend to reappear after some time. The accurate prediction of crack occurrence and the effectiveness of resurfacing works to control cracks are key factors in predicting the timing and costs of road maintenance. In view of this, it is imperative that a suitable model for the prediction of crack development be derived. This model will then be able to predict the deterioration rate of pavement cracking in the future. It in turn will enable effective road rehabilitation programs be implemented in time before cracking deteriorates and leads to eventual pavement failure.
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Jiang, Yanyao, and Miaolin Feng. "Modeling of Fatigue Crack Propagation." Journal of Engineering Materials and Technology 126, no. 1 (January 1, 2004): 77–86. http://dx.doi.org/10.1115/1.1631026.
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Fatigue crack propagation was modeled by using the cyclic plasticity material properties and fatigue constants for crack initiation. The cyclic elastic-plastic stress-strain field near the crack tip was analyzed using the finite element method with the implementation of a robust cyclic plasticity theory. An incremental multiaxial fatigue criterion was employed to determine the fatigue damage. A straightforward method was developed to determine the fatigue crack growth rate. Crack propagation behavior of a material was obtained without any additional assumptions or fitting. Benchmark Mode I fatigue crack growth experiments were conducted using 1070 steel at room temperature. The approach developed was able to quantitatively capture all the important fatigue crack propagation behaviors including the overload and the R-ratio effects on crack propagation and threshold. The models provide a new perspective for the R-ratio effects. The results support the notion that the fatigue crack initiation and propagation behaviors are governed by the same fatigue damage mechanisms. Crack growth can be treated as a process of continuous crack nucleation.
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Okabe, Tomonaga, Sota Onodera, Yuta Kumagai, and Yoshiko Nagumo. "Continuum damage mechanics modeling of composite laminates including transverse cracks." International Journal of Damage Mechanics 27, no. 6 (June 5, 2017): 877–95. http://dx.doi.org/10.1177/1056789517711238.
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In this study, the continuum damage mechanics model for predicting the stiffness reduction of composite laminates including transverse cracks is formulated as a function of crack density. To formulate the model, first the damage variable in the direction normal to the fiber of a ply including transverse cracks is derived. The damage variable is derived by the model assuming a plane strain field in the isotropic plane and using the Gudmundson–Zang model for comparison. The effective compliance based on the strain equivalent principle proposed by Murakami et al. and classical laminate theory are then used to formulate the elastic moduli of laminates of arbitrary lay-up configurations as a function of the damage variable. Finally, the results obtained from this model are compared to the finite-element analysis reported in previous studies. The model proposed in this paper can predict the stiffness of laminates containing damage due to transverse cracks (or surface crack) from just the mechanical properties of a ply and the lay-up configurations. Furthermore, this model can precisely predict the finite-element analysis results and experiment results for the elastic moduli of the laminate of arbitrary lay-up configuration, such as cross-ply, angle ply, and quasi-isotropic, including transverse cracks. This model only considers the damage of the transverse crack; it does not consider damage such as delamination. However, this model seems to be effective in the early stage of damage formation when transverse cracking mainly occurs. The model assuming plane strain field in the isotropic plane which is proposed in this paper can calculate the local stress distribution in a ply including transverse cracks as a function of crack density. The damage evolution of transverse cracks can thus be simulated by determining the fracture criterion.
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Gumbsch, Peter. "An atomistic study of brittle fracture: Toward explicit failure criteria from atomistic modeling." Journal of Materials Research 10, no. 11 (November 1995): 2897–907. http://dx.doi.org/10.1557/jmr.1995.2897.
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Atomistic techniques are used to study brittle fracture under opening mode and mixed mode loading conditions. The influence of the discreteness of the lattice and of the lattice-trapping effect on crack propagation is studied using an embedded atom potential for nickel to describe the crack tip. The recently developed FEAt (Finite Element-Atomistic) coupling scheme provides the atomistic core region with realistic boundary conditions. Several crystallographically distinct crack-tip configurations are studied and commonly reveal that brittle cracks under general mixed mode loading situations follow an energy criterion (G-criterion) rather than an opening-stress criterion (Kl-criterion). However, if there are two competing failure modes, they seem to unload each other, which leads to an increase in lattice trapping. Blunted crack tips are studied in the last part of the paper and are compared to the atomically sharp cracks. Depending on the shape of the blunted crack tip, the observed failure modes differ significantly and can drastically disagree with what one would anticipate from a continuum mechanical analysis.
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Ghelichi, Ramin, and Ken Kamrin. "Modeling growth paths of interacting crack pairs in elastic media." Soft Matter 11, no. 40 (2015): 7995–8012. http://dx.doi.org/10.1039/c5sm01376c.
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Leonovich, S. N. "Modeling of Capillary Shrinkage and Cracking in Early-Age Concrete." Science & Technique 17, no. 4 (July 31, 2018): 265–77. http://dx.doi.org/10.21122/2227-1031-2018-17-4-265-277.
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. Scientific hypothesis on moistening shrinkage mechanism for cement stone and concrete has been assumed as a basis for the present paper. Physical ideas on a mechanism for cracks volume increment in a concrete model presented as two-level structure have been accepted as a theoretical basis for a calculation method of crack resistance during capillary shrinkage. These ideas are the following: a matrix of hardening cement stone with inclusions and emptiness of various forms (cracks) as result of influences that change an intense deformed state in a point and a volume. The following assumptions have been accepted while making a theoretical justification for a calculation method of shrinkable concrete crack resistance. Following this methodology approaches of fracture mechanics according to a generalized criterion have been applied in the paper. Concrete is considered as an elastic quasi-homogeneous two-component medium which consists of the following parts:a) constructive part: a matrix – a cement stone with structural elements of crushed stone, sand; b) destructive part: emptiness – capillaries cracks and pores (cavities with initial cracks in walls). Emptiness in a matrix and contact zones are presented by a coordinated five-level system in the form and sizes which are multiple to a diameter due to impacts while reaching critical sizes. These critical sizes make it possible to pass from one level into another one according to the following scheme: size stabilization – accumulation delocalization – critical concentration in single volume – transition to the following level. Process of cracks formation and their growth are considered as a result of non-power influences on the basis of crack theory principles from a condition that fields of deformation and tension creating schemes of a normal separation and shift occur in the top part of each crack at its level in the initial concrete volume. Ксij(t) parameter as algebraic amount of critical values Kij in the whole system of all levels of cracks filling canonical volume up to critical concentration has been accepted as a generalized constant of property for concrete crack resistance in time, its resistance to formation, accumulation in volumes of micro-cracks and formation of trunk cracks with critical values. External temperature, moistening long influences create fields of tension in the top parts of cracks. Concrete destruction processes due to cracks are considered as generalized deformedintensed state in some initial volume having physical features which are inherent to a composite with strength and deformative properties. It is possible to realize analytical calculations for assessment of tension and crack resistance of concrete at early age on the basis of a generalized criterion in terms of stress intensity factor due to modern experimental data on capillary pressure value (70 kPa in 180 min after concrete placing). The developed algorithm of calculation allows to consider factors influencing on capillary pressure: type of cement, modifiers and mineral additives, concrete curing conditions.
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Lee, Jin Yi, Ji Seoung Hwang, Tetsuo Shoji, and Jae Kyoo Lim. "Modeling of Characteristics of Magneto-Optical Sensor Using FEM and Dipole Model for Nondestructive Evaluation." Key Engineering Materials 297-300 (November 2005): 2022–27. http://dx.doi.org/10.4028/www.scientific.net/kem.297-300.2022.
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The magneto-optical nondestructive inspection system (hereafter refer to as RMO system) using magneto-optical sensor (hereafter refer to as MO sensor) offers the benefits of providing image data and LMF information at the same time. Therefore this system makes it possible to carry out remote and high speed inspection of cracks from the intensity of the reflected light and to estimate the shape of a crack more effectively than by already existing methods. In other words, the shape of crack could be evaluated using image data, and crack depth can be determined by calculating the intensity of reflected light. The purposes of this study were to confirm the vertical components of leakage magnetic flux from a crack using RMO system and to verify the effects of MO sensor using the finite element method and dipole model calculation. The effectiveness of these analysis methods was compared with experiments using a RMO system and several types and sizes of the crack on plate specimens. The volume of a crack could be estimated using the optical intensity regardless of the shape of cracks.
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Zhang, Lin, Jing Ba, José M. Carcione, and Weitao Sun. "Modeling wave propagation in cracked porous media with penny-shaped inclusions." GEOPHYSICS 84, no. 4 (July 1, 2019): WA141—WA151. http://dx.doi.org/10.1190/geo2018-0487.1.
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Understanding acoustic wave dispersion and attenuation induced by local (squirt) fluid flow between pores and cracks (compliant pores) is fundamental for better characterization of the porous rocks. To describe this phenomenon, some squirt-flow models have been developed based on the conservation of the fluid mass in the fluid mechanics. By assuming that the cracks are represented by isotropically distributed (i.e., randomly oriented) penny-shaped inclusions, this study applies the periodically oscillating squirt flow through inclusions based on the Biot-Rayleigh theory, so that the local squirt flow and global wave oscillation of rock are analyzed in the same theoretical framework of Hamilton’s principle. The governing wave-propagation equations are derived by incorporating all of the crack characteristics (such as the crack radius, crack density, and aspect ratio). In comparison with the previous squirt models, our model predicts the similar characteristics of wave velocity dispersion and attenuation, and our results are in agreement with Gassmann equations at the low-frequency limit. In addition, we find that the fluid viscosity and crack radius only affect the relaxation frequency of the squirt-flow attenuation peak, whereas the crack density and aspect ratio also affect the magnitudes of dispersion and attenuation. The application of this study to experimental data demonstrates that when the differential pressure (the difference between confining pressure and pore pressure) increases, the closure of cracks can lead to a decrease of attenuation. The results confirm that our model can be used to analyze and interpret the observed wave dispersion and attenuation of real rocks.
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Petitpas, Eric, and B. Campion. "Crack Propagation in a Gun Barrel Due to the Firing Thermo-Mechanical Stresses." Journal of Pressure Vessel Technology 125, no. 3 (August 1, 2003): 293–98. http://dx.doi.org/10.1115/1.1592813.
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The thermo-mechanical effects of firing induce very considerable stresses on the internal surface of the gun barrels. Consequently, micro-cracks appear very soon in the life of the tube. So it is important to control the propagation of these cracks. For more than 10 years, modeling has been used by Giat-Industries to understand and to control this phenomenon. This paper focuses on the study of short crack propagation kinetics during firings. Two-dimensional modeling taking into consideration the residual stresses from a hydraulic autofrettage and the thermo-mechanical stresses due to the successive firings is presented. The cyclic plastic behavior of the material is taken into consideration. This makes it possible to observe the effect of loss of the residual stresses at the surface due to the firings. Cracks of increasing length are introduced in the model to calculate the stress intensity factor. An innovative point is the modeling of the contact between the crack lips in order to take into account the effect of crack closing during cooling. Indeed the effective stress intensity factor range is calculated using this model for numerous crack lengths. A classic Paris law is then used to predict the crack propagation kinetics. Sensitivity analysis has been carried out using this model; in particular, the effect of autofrettage on crack propagation is analyzed as well as the effect of the use of lower-strength steels.
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Kitamura, Takayuki, Louis J. Ghosn, and Ryuichi Ohtani. "Stochastic Modeling of Crack Initiation and Short-Crack Growth Under Creep and Creep-Fatigue Conditions." Journal of Applied Mechanics 59, no. 2S (June 1, 1992): S35—S42. http://dx.doi.org/10.1115/1.2899505.
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A simplified stochastic model is proposed for crack initiation and short-crack growth under creep and creep-fatigue conditions. Material inhomogeneity provides the random nature of crack initiation and early growth. In the model, the influence of microstructure is introduced by the variability of (1) damage accumulation along grain boundaries, (2) critical damage required for crack initiation or growth, and (3) the grain-boundary length. The probabilities of crack initiation and growth are derived by using convolution integrals. The model is calibrated and used to predict the crack density and crack-growth rate of short cracks of 304 stainless steel under creep and creep-fatigue conditions. The mean crack initiation lives are predicted to be within an average deviation of about ten percent from the experimental results. The predicted cumulative distributions of crack-growth rate follow the experimental data closely. The applicability of the simplified stochastic model is discussed and the future research direction is outlined.
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Lepikhin, A. M., N. A. Makhutov, and Yu I. Shokin. "Probabilistic multiscale modeling of fracture in heterogeneous materials and structures." Industrial laboratory. Diagnostics of materials 86, no. 7 (July 18, 2020): 45–54. http://dx.doi.org/10.26896/1028-6861-2020-86-7-45-54.
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The probabilistic aspects of multiscale modeling of the fracture of heterogeneous structures are considered. An approach combining homogenization methods with phenomenological and numerical models of fracture mechanics is proposed to solve the problems of assessing the probabilities of destruction of structurally heterogeneous materials. A model of a generalized heterogeneous structure consisting of heterogeneous materials and regions of different scales containing cracks and crack-like defects is formulated. Linking of scales is carried out using kinematic conditions and multiscale principle of virtual forces. The probability of destruction is formulated as the conditional probability of successive nested fracture events of different scales. Cracks and crack-like defects are considered the main sources of fracture. The distribution of defects is represented in the form of Poisson ensembles. Critical stresses at the tops of cracks are described by the Weibull model. Analytical expressions for the fracture probabilities of multiscale heterogeneous structures with multilevel limit states are obtained. An approach based on a modified Monte Carlo method of statistical modeling is proposed to assess the fracture probabilities taking into account the real morphology of heterogeneous structures. A feature of the proposed method is the use of a three-level fracture scheme with numerical solution of the problems at the micro, meso and macro scales. The main variables are generalized forces of the crack propagation and crack growth resistance. Crack sizes are considered generalized coordinates. To reduce the dimensionality, the problem of fracture mechanics is reformulated into the problem of stability of a heterogeneous structure under load with variations of generalized coordinates and analysis of the virtual work of generalized forces. Expressions for estimating the fracture probabilities using a modified Monte Carlo method for multiscale heterogeneous structures are obtained. The prospects of using the developed approaches to assess the fracture probabilities and address the problems of risk analysis of heterogeneous structures are shown.
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Liang, Jiachen, Bo Chen, Chenfei Shao, Jianming Li, and Bangbin Wu. "Time Reverse Modeling of Damage Detection in Underwater Concrete Beams Using Piezoelectric Intelligent Modules." Sensors 20, no. 24 (December 19, 2020): 7318. http://dx.doi.org/10.3390/s20247318.
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Underwater cracks in concrete structures are often difficult to detect due to their complexity of the service environment. With numerical and experimental analysis of concrete beams immersed in water, an active monitoring system, based on a cement-based piezoelectric intelligent module array (CPIMA), was developed to locate and quantify the underwater cracks. Time reversal (TR) of the stress wave field is accomplished to focus on the crack area through the concrete beam specimen by the system. First, a piezoelectric actuator is applied to emit the initial propagating wave, which can be reflected, attenuated, and diffracted by the crack, transmitted through water filled in the crack, as well as diffracted by the coarse aggregates. To extract the damage waveforms associated with the crack and analyze the robust time-reversal invariance under the high-order multiple scattering effect, a pair of homogeneous and heterogeneous forward finite element (FE) models is established. Then, the damage waveforms are time-reversed and re-propagated in the inverse numerical model, where an optimal refocusing is achieved on the crack that behaves as an acoustic source. Finally, the damage area is obtained in the form of the stacked energy distribution of each time step. The focus results are represented by cloud images and compared with root-mean-square deviation (RMSD) values. Numerical simulation and experiments show that this method can identify and quantify underwater cracks effectively.
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Qi, Jing Hua, Zhen Nan Zhang, and Xiu Run Ge. "Numerical Study on Progressive Failure of the Marble Plate Based on the Thin-Layer Tri-Node Jointed Element." Advanced Materials Research 255-260 (May 2011): 1867–72. http://dx.doi.org/10.4028/www.scientific.net/amr.255-260.1867.
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In order to model the mechanical behavior of joints efficiently, a thin-layer tri-node joint element is constructed. The stiffness matrix of the element is derived in the paper. For it shares the common nodes with the original tri-node triangle element, the tri-node joint element can be applied to model the crack propagation without remeshing or mesh adjustment. Another advantage is that the cracked body is meshed without consideration of its geometry integrity and existence of the joints or pre-existed crack in the procedure of mesh generation, and then the triangular element intersected by the crack or joint is automatically transformed into the tri-node joint element to represent pre-existed cracks. These make the numerical simulation of crack propagation highly convenient and efficient. After CZM is chosen to model the crack tip, the mixed- energy simple criterion is used to determine whether the element is intersected by the extended crack or not, the extended crack is located in the model. By modeling the marble plates with two edge cracks subjected to the uniaxial compressive loads, it is shown that the numerical results are in good agreement with the experimental results, which suggests that the present method is valid and feasible in modeling rock crack propagation.
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Hirobe, Sayako, and Kenji Oguni. "Modeling and Simulating Methods for the Desiccation Cracking." International Journal of Computational Methods 16, no. 05 (May 28, 2019): 1840011. http://dx.doi.org/10.1142/s021987621840011x.
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The desiccation cracks can be observed on dry-out soil fields or other various materials under desiccation. These cracks have a net-like structure and tessellate the surface of the materials into polygonal cells. The averaged cell size changes systematically depending on the size of the specimen. In spite of the varieties of the materials, these fundamental features of the cell topology are conserved. This implies the existence of the governing mechanism behind the desiccation crack phenomenon regardless of the materials. In this paper, the desiccation crack phenomenon is modeled by the coupling of desiccation, deformation, and fracture. We perform simulations for the reproduction of the desiccation cracking based on this coupling model. In the simulations, the finite element analysis for the desiccation problem and the analysis of particle discretization scheme finite element method for the deformation and the fracture problems are weakly coupled. The results of the simulations show the satisfactory agreements with the experimental observations in terms of the geometry of the crack pattern, the increase tendency of the averaged cell size depending on the size of the specimen, and the hierarchical sequence of the cell formation. These agreements indicate that the proposed model and method capture the fundamental features and the mechanism of the desiccation cracking.
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Izvekov, Yury, Olga Torshina, Alexander Anisimov, Galina Kameneva, and Tatyana Bondarenko. "Probabilistic modeling of crack growth in large structures." MATEC Web of Conferences 329 (2020): 03021. http://dx.doi.org/10.1051/matecconf/202032903021.
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The allowance for various defects including cracks represents a critical issue related to structural risk analysis. The complexity and the ambiguity involved with such allowance for the amount and growth of defects (cracks) is demonstrated on the real structure of a metallurgical overhead crane. The problem of distribution function conversion must be solved to allow for any variations in defects starting from the point of time when the initial (technological) defectiveness is determined and ending with the estimated time of risk analysis. Due to the lack of data on cyclic resistance to cracking for Вст3сп5 steel, it does not yet seem possible to construct the distribution functions and to determine the estimated theoretical average and dispersion of crack sizes. However, by using the previously obtained calculated data on active stresses and strains, it is now possible to simulate growth of cracks based on Weibull distribution. Different engineering solutions can be accepted at various stages of operating large structures, according to the obtained results.
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Zhao, Yong Xiang, and Bing Yang. "Modeling to the Fatigue Crack Growth Rates of the Cast Steel for Chinese Railway Rolling Wagon Bogie Frames." Advanced Materials Research 118-120 (June 2010): 105–10. http://dx.doi.org/10.4028/www.scientific.net/amr.118-120.105.
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Compact tensional specimens are fatigued for modeling the fatigue crack growth rates of the cast steel for Chinese railway rolling wagon bogie frames. Typical fracture surface observations indicate that the fatigue cracks grew with distinct fatigue striations, river-like flowers, and second cracks in perpendicular to the fatigue crack path. Lots of dimples appeared in the transient fracture district to indicate that present material is ductile. Similar to the previous NASGRO’s exploration, a full modeling is proposed from fatigue cracking threshold to the transient fracture corresponding to the material fracture roughness. Availability has been verified to be applied for the present material. In addition, this modeling is very simple that the modeling can be performed by the conventional tests of fatigue cracking thresholds, growth rates, and fracture roughness values.
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Pang, John Hock Lye, and You Xiang Chew. "Fatigue Crack Growth and Coalescence Algorithm Starting from Multiple Surface Cracks." Advanced Materials Research 891-892 (March 2014): 1003–8. http://dx.doi.org/10.4028/www.scientific.net/amr.891-892.1003.
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Fatigue crack growth and propagation analysis in welded joints have to deal with the complexity of modeling multiple weld toe surface cracks originating from weld toes. Fitness-For-Service (FFS) assessments for weld toe surface cracks employ a fracture mechanics and Paris Law approach to predict the fatigue crack propagation life of a semi-elliptical surface crack (SESC) to failure. A fatigue crack growth algorithm for assessing multiple surface crack growth, coalescence and propagation life was initially validated with previuously report crack growth data for a fillet shoulder specimen. Next a parametric study for single, double, and triple SESCs located along the weld toe line of a fillet weld was investigated with three starting crack depth sizes (0.1mm, 0.5mm, 1.0mm) coupled with three different crack aspect ratios (a/c = 1.0, a/c = 0.5 and 0.25) giving a total of 27 cases studied.
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Bostro¨m, Anders. "Review of hypersingular integral equation method for crack scattering and application to modeling of ultrasonic nondestructive evaluation." Applied Mechanics Reviews 56, no. 4 (July 1, 2003): 383–405. http://dx.doi.org/10.1115/1.1574522.
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The scattering of elastic waves by cracks in isotropic and anisotropic solids has important applications in various areas of mechanical engineering and geophysics, in particular in ultrasonic nondestructive testing and evaluation. The scattering by cracks can be investigated by integral equation methods, eg, boundary element methods, but here we are particularly concerned with more analytically oriented hypersingular integral equation methods. In these methods, which are only applicable to very simple crack shapes, the unknown crack opening displacement in the integral equation is expanded in a set of Chebyshev functions, or the like, and the integral equation is projected onto the same set of functions. This procedure automatically takes care of the hypersingularity in the integral equation. The methods can be applied to cracks in 2D and 3D, and to isotropic or anisotropic media. The crack can be situated in an unbounded space or in a layered structure, including the case with an interface crack. Also, problems with more than one crack can be treated. We show how the crack scattering procedures can be combined with models for transmitting and receiving ultrasonic probes to yield a complete model of ultrasonic nondestructive testing. We give a few numerical examples showing typical results that can be obtained, also comparing with some experimental results. This review article cites 78 references.
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Veluri, Badrinath, and Henrik Myhre Jensen. "A Computational Method for Modeling Interface Corner Crack under Steady-State Delamination." Advanced Materials Research 486 (March 2012): 457–63. http://dx.doi.org/10.4028/www.scientific.net/amr.486.457.
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Corner cracks under steady-state delamination were investigated. The fracture mechanics parameters that include the strain energy release rate and the three-dimensional mode-mixity along the interface crack front are estimated. A numerical approach was then applied for coupling the far field solutions based on the Finite Element Method to the near field (crack tip) solutions based on the J-integral methodology. A quantitative approach was formulated based on the finite element method with iterative adjustment of the crack front nodal coordinates to estimate the critical delamination stresses as a function of the fracture criterion and corner angles.
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Kim, Eui-Keun, Habeun Choi, Kyoungsoo Park, and Won-Hee Kang. "Deterministic and Probabilistic Investigation on Multiple Crack Interactions in a Semi-Infinite Domain." Mathematical Problems in Engineering 2015 (2015): 1–9. http://dx.doi.org/10.1155/2015/305397.
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The investigation of multiple crack interactions in fracture mechanics is important to predict the safety and reliability of structures. This study aims to investigate the interactions of multiple parallel cracks in a semi-infinite domain in both deterministic and probabilistic ways by using an automated finite element modeling procedure and the Monte Carlo simulation. The stress intensity factor is considered as an indicator of failure and accurately evaluated by using the domain integral technique. The variation of the stress intensity factor according to the position, the length, and the number of cracks is demonstrated. In a probabilistic investigation, the effects of the number of cracks, the random distribution of the crack lengths, and the crack interactions to the failure probability are studied for a semi-infinite domain. The stress redistribution among multiple cracks, the effect of unevenly distributed crack lengths, and the combined effect of crack length uncertainties and a crack shielding effect have been examined.
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Oussoren, Andrew, Jovica Riznic, and Shripad Revankar. "ICONE23-2115 MODELING CRITICAL FLOW IN CRACK GEOMETRIES USING TRACE." Proceedings of the International Conference on Nuclear Engineering (ICONE) 2015.23 (2015): _ICONE23–2—_ICONE23–2. http://dx.doi.org/10.1299/jsmeicone.2015.23._icone23-2_44.
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Sun, Xizhen, Fanbao Meng, Ce Zhang, Xucai Zhan, and He Jiang. "Progressive Failure and Acoustic Emission Characteristics of Red Sandstone with Different Geometry Parallel Cracks under Uniaxial Compression Loading." Advances in Materials Science and Engineering 2021 (March 11, 2021): 1–11. http://dx.doi.org/10.1155/2021/5569091.
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The geometric distribution of initial damages has a great influence on the strength and progressive failure characteristics of the fractured rock mass. Initial damages of the fractured rock were simplified as parallel cracks in different geometric distributions, and then, the progressive failure and acoustic emission (AE) characteristics of specimens under the uniaxial compression loading were analyzed. The red sandstone (brittle materials) specimens with the parallel preexisting cracks by water jet were used in the tests. The energy peak and stress attenuation induced by the energy release of crack initiation were intuitively observed in the test process. Besides, three modes of rock bridge coalescence were obtained, and wing crack was the main crack propagation mode. The wing crack and other cracks were initiated in different loading stages, which were closely related to the energy level of crack initiation. The propagation of wing crack (stable crack) consumed a large amount of energy, and then, the propagation of shear crack, secondary crack, and anti-wing crack (unstable crack) was inhibited. The relationship between the crack propagation mode and the geometric distribution of existing cracks in the specimen was revealed. Meanwhile, the strength characteristic and failure mode of fractured rock with the different geometric distributions of preexisting crack were also investigated. The energy evolution characteristics and crack propagation were also analyzed by numerical modeling (PFC2D).
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Eltahan, Ahmed A., and Robert L. Lytton. "Mechanistic-Empirical Approach for Modeling Reflection Cracking." Transportation Research Record: Journal of the Transportation Research Board 1730, no. 1 (January 2000): 132–38. http://dx.doi.org/10.3141/1730-16.
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Models developed to predict reflective cracking in flexible pavement overlays do not explicitly incorporate the combined effect of the cracked and uncracked areas in the original pavement. This affects the development of cracks in the overlay. Therefore, a model is needed that will incorporate this factor explicitly, making predicting of cracking in pavement overlays more realistic in pavement management systems and pavement reliability. A mechanistic approach based on fracture mechanics with an empirical stochastic form to develop the desired model is presented. This approach has been adopted because the new design trends (such as the new 2002 AASHTO design guide) will follow a more mechanistic approach than the current trends. In addition, this approach is lacking in the literature for data of in-service roads. The use of the developed model for the study of crack initiation is presented. Data obtained from the Florida Department of Transportation are divided into Interstates and arterials. The results show that the proposed model predicts the observed cracking with an R2 of 0.72 for the Interstates and 0.40 for the arterials. Because the exact time of crack initiation is not recorded, the observed crack-initiation time is approximated by the last time no cracking was observed (i.e., right before cracking was first recorded). The proposed methodology predicts the crack-initiation time with an average absolute error of 18.6 percent.
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Amiri, M., and M. Modarres. "Short fatigue crack initiation and growth modeling in aluminum 7075-T6." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 229, no. 7 (August 12, 2014): 1206–14. http://dx.doi.org/10.1177/0954406214546880.
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A series of fatigue tests is carried out to investigate the behavior of microcrack initiation and propagation in Al 7075-T6. Plate specimens with semi-circular single edge notch are tested under uniaxial loading at different load amplitudes. Optical microscopy is used to detect the initiation and growth of short cracks. Continuum damage mechanics is used to model the crack initiation. After the initiation, crack growth is studied using fracture mechanics models. For both regions of crack initiation and growth, Bayesian estimation method is used to account for uncertainties in the parameters of the model. Results of the entire fatigue life, including initiation and growth, are compared with experiments. Good agreement is observed.
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Chen, Bo, Zhongru Wu, Jiachen Liang, and Yanhong Dou. "Time-Varying Identification Model for Crack Monitoring Data from Concrete Dams Based on Support Vector Regression and the Bayesian Framework." Mathematical Problems in Engineering 2017 (2017): 1–11. http://dx.doi.org/10.1155/2017/5450297.
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The modeling of cracks and identification of dam behavior changes are difficult issues in dam health monitoring research. In this paper, a time-varying identification model for crack monitoring data is built using support vector regression (SVR) and the Bayesian evidence framework (BEF). First, the SVR method is adopted for better modeling of the nonlinear relationship between the crack opening displacement (COD) and its influencing factors. Second, the BEF approach is applied to determine the optimal SVR modeling parameters, including the penalty coefficient, the loss coefficient, and the width coefficient of the radial kernel function, under the principle that the prediction errors between the monitored and the model forecasted values are as small as possible. Then, considering the predicted COD, the historical maximum COD, and the time-dependent component, forewarning criteria are proposed for identifying the time-varying behavior of cracks and the degree of abnormality of dam health. Finally, an example of modeling and forewarning analysis is presented using two monitoring subsequences from a real structural crack in the Chencun concrete arch-gravity dam. The findings indicate that the proposed time-varying model can provide predicted results that are more accurately nonlinearity fitted and is suitable for use in evaluating the behavior of cracks in dams.
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Wijerathne, M. L. L., Muneo Hori, T. Okinaka, and Hide Sakaguchi. "Application of PDS-FEM for Simulating 3D Wing Crack Growth." Applied Mechanics and Materials 553 (May 2014): 725–30. http://dx.doi.org/10.4028/www.scientific.net/amm.553.725.
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3D wing crack growth is not a well understood phenomenon, although it is one of the key mechanisms of the failure of brittle materials under compression. Using PDS-FEM, we simulated the growth of 3D wing cracks emerging from pre-existing cracks in blocks of brittle linear elastic solids, under compression. The complex 3D wing crack profiles are reproduced with PDS-FEM, which uses non-overlapping shape functions of conjugate geometries to approximate functions and their derivatives. PDS-FEM provides numerically efficient failure treatment for modeling 3D cracks, making use of the numerous discontinuities in the approximated displacement field. Large scale models with several million elements are used to reproduce the experimentally observed details of wing crack profiles. The bending of crack surfaces at the tip of mode-I regions, extension of wing cracks and the growth of tensile openings or petal cracks at mode-III regions are reproduced, demonstrating the applicability of PDS-FEM for studying 3D wing crack growth phenomena.
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Zhao, Yong Xiang, Z. He, and B. Yang. "Short Fatigue Crack Propagation Threshold of Railway LZ50 Axle Steel." Advanced Materials Research 544 (June 2012): 274–79. http://dx.doi.org/10.4028/www.scientific.net/amr.544.274.
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Collective short fatigue behaviour nearby material micro-structural barrier threshold is experimentally observed for the smooth specimens of Chinese railway LZ50 axle steel. Effective micro-cracks which result in the specimens’ failure were initiated from the material ferrite particles on the surfaces of the specimens. Four elements i.e. crack size, orientation angle, and the two crack tip orientation angles should be contained for each micro-crack. The collective micro-crack behaviour should be described by an equivalent dominant effective short fatigue crack (ESFC) concept using an ESFC theory. And an equivalent method is then developed with an equivalent growth driving energy concept. A random modeling of the equivalent dominant ESFC growth rates is further constructed for describing the random behaviour of the collective ESFCs nearby the material micro-structure barrier threshold. And the kinetic threshold is subsequently conducted from the modeling.
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Petrangeli, Marco, and Joško Ožbolt. "Smeared Crack Approaches—Material Modeling." Journal of Engineering Mechanics 122, no. 6 (June 1996): 545–54. http://dx.doi.org/10.1061/(asce)0733-9399(1996)122:6(545).
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Stepanov, G. V., and A. V. Shirokov. "Modeling of crack propagation kinetics." Strength of Materials 42, no. 4 (July 2010): 426–31. http://dx.doi.org/10.1007/s11223-010-9233-1.
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Sehitoglu, Huseyin, and Wei Sun. "Modeling of Plane Strain Fatigue Crack Closure." Journal of Engineering Materials and Technology 113, no. 1 (January 1, 1991): 31–40. http://dx.doi.org/10.1115/1.2903380.
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Mechanisms and models proposed for plane strain fatigue crack closure are evaluated. A mechanism based on out-of-plane plastic strain component, εzp, in plane strain is shown not to be adequate in explaining closure over a wide range of applied load levels. In the second model, partial relief of compressive stresses in front of the crack tip upon crack advance is forwarded as responsible for crack closure in plane strain. It is argued that this model would hold only if the crack advanced into a compressive stress zone which is highly improbable. A third model based on compressive strain accumulation in the x-direction, εxp, (transverse or crack growth direction) is studied. Material ahead of the crack tip contracts in the transverse direction and this mechanism provides residual material for crack surfaces as the crack advances. Stress-strain history and material displacements as crack advances are presented for plane strain conditions that lend further support to the third model. The results are obtained with a specialized finite element analysis with provisions for crack advance and crack closure. The crack opening load corresponding to relief of compressive residual stresses behind the crack tip is determined for plane stress and plane strain cases under R= − 1, 0 and 0.3 loading. The load at which stresses ahead of the crack tip become tensile, Pt, is also determined for plane stress and plane strain conditions and is found to exceed the crack opening load in all cases. The relevance of this parameter on fatigue crack growth behavior is discussed.
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Kibey, S., H. Sehitoglu, and D. A. Pecknold. "Modeling of fatigue crack closure in inclined and deflected cracks." International Journal of Fracture 129, no. 3 (October 2004): 279–308. http://dx.doi.org/10.1023/b:frac.0000047787.94663.c8.
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