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1
Ballarini, R., i S. Muju. "Stability Analysis of Bridged Cracks in Brittle Matrix Composites". Journal of Engineering for Gas Turbines and Power 115, nr 1 (1.01.1993): 127–38. http://dx.doi.org/10.1115/1.2906667.
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The bridging of matrix cracks by fibers is an important toughening mechanism in fiber-reinforced brittle matrix composites. This paper presents the results of a nonlinear finite element analysis of the Mode I propagation of a bridged matrix crack in a finite size specimen. The composite is modeled as an orthotropic continuum and the bridging due to the fibers is modeled as a distribution of tractions that resist crack opening. A critical stress intensity factor criterion is employed for matrix crack propagation, while a critical crack opening condition is used for fiber failure. The structural response of the specimen (load-deflection curves) as well as the stress intensity factor of the propagating crack is calculated for various constituent properties and specimen configurations for both tensile and bending loading. By controlling the length of the bridged crack, results are obtained that highlight the transition from stable to unstable behavior of the propagating crack.
2
Chao, Xu, i Shang Lei Yang. "Analysis on Fatigue Crack Propagation and Fractography of A7075 Aluminum Alloy". Applied Mechanics and Materials 217-219 (listopad 2012): 390–94. http://dx.doi.org/10.4028/www.scientific.net/amm.217-219.390.
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The fatigue fractography and surface of A7075 aluminum alloy was investigated by means of optical microscope, scanning electron microscope and technology of metallurgic replica. The results show that the fatigue crack generally initiated in the surface or near the surface of the sample area, such as hole and inclusion. The crack propagation regions under high stress amplitude was characterized by furrow and hollow, and obviously presented fine ripple vein. While lots of fatigue striations and sidesteps with the holes and secondary cracks generated in the crack propagation regions of low stress amplitude. Fatigue transient breaking area is a mixed fracture of brittle and ductile fracture. In the fatigue crack propagation stage, with the increasing of cycle times, secondary cracks gradually merged into primary crack on the path of crack propagation. The dislocation of crack tip,grain boundaries and different grain orientations have great influence on the path of crack growth, which can make cracks bending.
3
Sun, Yazhen, Ting Yan, Changyu Wu, Xiaofang Sun, Jinchang Wang i Xuezhong Yuan. "Analysis of the Fatigue Crack Propagation Process of the Stress-Absorption Layer of Composite Pavement Based on Reliability". Applied Sciences 8, nr 11 (30.10.2018): 2093. http://dx.doi.org/10.3390/app8112093.
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The stress-absorption layer in cement concrete pavement delays the development of reflection cracks and is good at fatigue resistance. Laboratory investigations of the anti-crack performance of the high viscous asphalt sand stress-absorption layer (HVASAL) and rubber asphalt stress-absorption layer (RASAL) were carried out by force-controlled fatigue crack propagation tests, for which three types of overlay structures with three types of pre-crack (i.e., the middle crack, the side crack, and the 45° inclined crack) were designed. A probability model was established to describe the propagation of the fatigue cracks. The fatigue crack propagation, the fatigue life, the crack propagation rate, and the crack propagation mechanism of the three types of overlay structure were compared and analyzed. The results show that the stress-absorption layers have good anti-crack fatigue performance, and that the RASAL is better than the HVASAL. The crack propagation patterns of the three types of overlay structure were found. In the double logarithmic coordinate, the curves of the three types of cracks are straight lines with different intercepts and slopes. The probability model quantifies the relationship between the crack propagation rate and ∆K. The influences of the three types of crack on the fatigue properties of the asphalt overlays are different.
4
Zhu, Yong, Ray K. L. Su i Qi Cai Yu. "Initial Crack Propagation Directions of Branched Crack under Tension with Finite Element Analysis". Advanced Materials Research 168-170 (grudzień 2010): 2553–57. http://dx.doi.org/10.4028/www.scientific.net/amr.168-170.2553.
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The initial crack propagation directions of branched cracks under tension are investigated. In this study, the material is assumed to be brittle and deformed linear elastically. The elastic stress fields and stress intensity factors are obtained by using finite element analysis method. Various parameters which including the lengths, the directions and the locations of branched cracks are investigated to study their effects on the crack initiation angles. Three kinds of crack propagation criteria are employed to obtain the crack initiation angles. The effects of crack propagation directions due to the use of different crack initiation criteria are studied and discussed in details.
5
Li, De Jian, Fei Zhao, Run Jie Ma, Li Qiang Han i Xiao Hu Wu. "Analysis of Cracking Processes of Sandstone in Rockburst Test". Applied Mechanics and Materials 256-259 (grudzień 2012): 1052–59. http://dx.doi.org/10.4028/www.scientific.net/amm.256-259.1052.
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High speed camera system is used to record crack propagation on rock surface during the lab rocburst experiment. This paper presents the specific analytical method of crack propagation with high speed images. Crack propagation types and directions are briefly described, and the lengths, growth rate and fractal dimension of cracks are calculated. The results show that the crack grows mainly along the horizontal line on the unloading surface, at a low speed before rockburst and reaches a very high speed abruptly near the burst point. The fractal dimensions demonstrated that the crack turns to be rough when rockburst happens. The study on the crack propagation is benefit to the understanding on the mechanism of rockburst.
6
Liu, Ning, i Chun Sheng Zhang. "Numerical Analysis on Splitting Failure of Brittle Material". Advanced Materials Research 143-144 (październik 2010): 156–60. http://dx.doi.org/10.4028/www.scientific.net/amr.143-144.156.
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Realize the basic process of fracture analysis in ANSYS. The fore treatment program of crack propagation simulation is compiled by parameterization method of apdl. The calculation and analysis is automatic. ANSYS is well for simulating the structures which contain cracks and bugs. When the parameters are suitable, the propagation of cracks can be simulated well in ANSYS. The different phases of crack propagation are simulated. To compare with the results by theory, perfect the formation process and mechanism of splitting cracks.
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Chen, Zhong Hui, Jing Jing Feng, Li Li i He Ping Xie. "Fracture Analysis on the Interface Crack of Concrete Gravity Dam". Key Engineering Materials 324-325 (listopad 2006): 267–70. http://dx.doi.org/10.4028/www.scientific.net/kem.324-325.267.
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Some numerical parameters-sensitivity analysis has been conducted to evaluate the stability and propagation of the interface cracks at heel of concrete gravity dam. In this paper, utilizing the software ANSYS to simulate the stress and displacement fields of the tip of the interface cracks between concrete gravity dam and foundation, the stress intensity factor (SIF) of the interface crack is analyzed using facture mechanics. Three impacting factors have been discussed, such as the crack length, the angle of crack, and the water height. Critical length and loads of interface crack propagation are obtained using composite fracture criteria. The results indicate that the coarse interface retards the propagation of interface crack, and redounds to stability of gravity dam. It is found that the interface crack often propagates alone the interface between dam and foundation, simultaneously the branch crack kinks to foundation at the specific condition.
8
Gulzar, Mubashir. "Linear Analysis of Crack Propagation in a Solid Rocket Propellant". Applied Mechanics and Materials 229-231 (listopad 2012): 742–46. http://dx.doi.org/10.4028/www.scientific.net/amm.229-231.742.
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The Solid Rocket Propellant in its crude form is a rubber like material. This rubber like material performs very interestingly when used to study crack propagation. Blunting of crack tips occurred in the composite when the load is applied, which is generally non-linear phenomenon. The crack propagation analysis for such case is generally taken for double edge cracks but the presence of central cracks in the composites cannot be ignored. This trend is nonlinear and complex. In order to simplify things, optical grade polyurethane material is used instead. The polyurethane material we used for our experimental work was PSM-4. In this research work, an extensive study is made regarding crack propagation analysis using the basic principles of fracture mechanics and its different techniques for finding out the parameter necessary for tracing crack propagation. Mode 1 (Opening Mode) is considered for the central crack propagation analysis. The objectives set in this context are the determination of Stress Intensity Factor of central crack in the specimen using photoelastic experimental data and simulation of central crack in softwares (ANSYS, Pro-e). For this purpose a rectangular plate with Central Crack was used to be experimented upon using the techniques of Photoelasticity. A comparative analysis technique is adopted to compare the effectiveness of results from experiments as well as software simulations.
9
Yuan, Duan Cai, Guo Jin Tang, Yong Jun Lei i Shang Yang Meng. "Analysis of the Surface Cracks of Long Range Storage Solid Motor Grain". Key Engineering Materials 324-325 (listopad 2006): 93–96. http://dx.doi.org/10.4028/www.scientific.net/kem.324-325.93.
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The surface cracks are easy to occur in the solid missile motor grain. The solid missile motor grain with cracks is very dangerous when it is lunched, because the surface cracks might be propagation unstable when the internal pressure enters the surface cracks cavity. In order to analyze the surface crack of solid motor grain, with accelerated aging test, the variation law of mechanics properties of propellant in the storage period is obtained. Under internal pressure and axial acceleration loading, the three-dimension finite element models of the motor grain are established, three-dimension singular crack elements at the tips of surface cracks are established to simulate the cracks propagation. Along with the surface crack propagation, the stress intensity factors of the crack tips in different storage period are calculated to prejudge its stability respectively. The method and conclusions are available for using solid missile motor grain with surface cracks.
10
Chen, Hao. "Instable Crack Propagation Analysis with PDS-FEM". Applied Mechanics and Materials 234 (listopad 2012): 53–58. http://dx.doi.org/10.4028/www.scientific.net/amm.234.53.
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This paper studies the stability of dynamic crack propagation in a homogeneous plate with 2 parallel cracks located in an anti-symmetric manner. PDS-FEM is extended to the dynamic setting, and a method to randomly generate unbiased mesh is developed. Monte-Carlo simulation is carried out to study the crack patterns. It is shown that a solution for low and high loading rate displacement loading condition is stable or instable, respectively, since the crack pattern loses anti-symmetricity for the latter boundary condition.
11
Shao, Peng, Yong Zhang, Wen Ming Gao i Yong Qiang Liu. "Dynamic Response of Intermittent Jointed Rock Mass Subjected to Blast Waves". Key Engineering Materials 306-308 (marzec 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.
12
Hu, Mingtao, Zihan Li i Zhongjue Wang. "Numerical Simulation Analysis of Rock Fracture Propagation Based on VUMAT". Highlights in Science, Engineering and Technology 52 (4.07.2023): 70–75. http://dx.doi.org/10.54097/hset.v52i.8815.
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The study of crack propagation in rock is of great significance to the stability of structural engineering. In this paper, through ABAQUS software, a simulation method of rock fracture propagation law is proposed. The D-P criterion of shear effect (Drucker Prager criterion) is embedded into the VUMAT subroutine in ABAQUS software, and the rule of rock fracture propagation is analyzed by using the element deletion method. The results show that: (1) stress concentration occurs first at the tip of the prefabricated crack, and then fracture occurs; (2) The fracture pattern is perpendicular to the crack, develops symmetrically, and produces secondary horizontal cracks; (3) The crack develops and forms an anti-wing crack, which continues to expand with the secondary horizontal crack, and finally the rock is destroyed. (4) Compared with the test results, the model can better reflect the law of rock crack propagation.
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Leonavičius, Mindaugas, i Stanislav Stupak. "ANALYSIS OF CYCLIC FRACTURE OF THE THREADED JOINTS/SRIEGINIŲ JUNGČIŲ CIKLINIO IRIMO SĄLYGŲ ANALIZĖ". JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 6, nr 2 (30.04.2000): 97–103. http://dx.doi.org/10.3846/13921525.2000.10531572.
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The initial production defects having been transferred into a structure and developed during its operation, it is crucial for labour safety to prevent such defects from reaching critical limits. First, the defects should be measured and then calculations of the parameters affecting the extent of their propagation are to be made. Provisions should be made to control damage during production and maintenance process. Evaluation of the structural element strength, once the defect or crack is detected, is rather a complicated procedure requiring sometimes additional theoretical solution or even an experimental research. The limit state conditions favouring stopping the crack find their way to practical application. If such conditions are maintained, it is estimated that the structural element containing a crack in a state of stoppage is able to perform fully its functions. In the paper, the resistance of threaded joints to cyclic loading is defined and based on the criteria of fracture mechanics describing non-permissible operational limit states: formation of macrocrack; transition from stable crack propagation to a dynamic one, ie fracture of the structural element; stable crack propagation exceeding the permissible crack size; transition from the defect (stable crack) to steadily propagating crack, ie continuous accumulation of damage. The regularities of the fracturing process, taking into account constructive peculiarities, production technology and loading conditions were studied in threaded joints within the range of M8 to M48. Threaded joints were tested according to the system ‘nut-stud-nut’ and ‘nut-stud-body’ made of steel 25XIMΦ and 20XIMIΦITP which are widely used to manufacture elements for fixing power equipment. The indicators of mechanical properties are as follows: σ0.2=780÷1020 MPa; σ u =830÷1120 MPa; Ψ=58÷62%. Nuts were manufactured from the same kind of steel as studs, or from another kind of steel with different mechanical properties. The characteristic stages of crack propagation and its rate along the cavity and deeper into the cross-section are presented in the works of the authors. In the experiments, the criterion of fracture mechanics K 1 was applied to describe the crack propagation rate and to investigate the conditions of brittle fracture. A special investigation was carried out to substantiate such a decision. On the basis of the refraction obtained, the S. Jarioma equation was applied to calculate the stress intensity ratio. The parameters of kinetic the fatigue diagrams (a threaded joint and cylindrical specimen 20 with a ring notch imitating the cavity of thread M20) described by means of the P. Paris equation are presented in the works of the authors. The presented experimental data of the cyclic fracture strength of models M20 are characteristic of threaded joints of other size too, not only of those with the size ranging from M8 to M48. Similar regularities were observed in natural specimens of threaded joints M 140x6. The low-cycle fatigue strength of threaded joints manufactured from steel with different mechanical properties (studs made of steel 25XIMΦ, nuts of steel 20.40X and TC) change insignificantly. A more uniform distribution of notches were observed, however, it has a minimal effect on threshold and crack propagation. To determine specific peculiarities which are characteristic of threaded joints, additional experiments were carried out. It is known that a properly constructed threaded joint ‘nut-stud- nut’ undergoes fracture in the stud bar during the construction loading (as in case of tension). Provided there is a big crack in the stud, the fracture can occur on the plane of the cavity during the construction loading. Specimens of three types were studied as follows: cylindrical specimens with a crack; studs with a crack and threaded joints ‘stud-nut’ with a crack in their studs. The results of the experiment depending on the depth of the crack are presented. Different regularities of the threshold, crack propagation and its brittle fracture can be explained as follows: a different stressed state within the cavity of the stud thread (the total result of the stud tension and turn bending) and in the ring notch of the cylindrical specimen; a different front of crack propagation; a different angle of crack propagation (perpendicular to loading in the cylindrical specimen and along the angle of the rise of a turn in the stud); the effect of the first joint turns of the stud and the nut which limits crack opening and influences the processes taking place on the top of a crack. All these factors determine a certain difference between the intensity ratios of critical stresses: materials K c ; studs K cb and studs joint to the nut K ct . Making use of earlier and additional experimental investigation of threaded joints made of steel 25XIMΦ (normalising), the part of the diagram of kinetic fatigue was drawn in which the number of loading cycles exceeds 107. This part characterises the propagation of short cracks. The marginal value ΔK th of the intensity of stresses is a threshold below which cracks do not propagate. One more peculiarity of the experiment results should be indicated—at least two specimens (stud-nut) were tested under equal conditions, but the cracks propagated differently. In the opinion of the authors, cracks propagating in the stud change the flows of the internal resultant in the system ‘stud-nut’ as a consequence of which the crack propagation rate either decreases or terminates. Making use of the experimental data and analysis of the stressed state, the study of the region close to the threshold (ΔK th ) was conducted by means of finite element method. The amplitude of the endurance limit of an even specimen is regarded as the limit state of the threshold. A satisfactory correlation of the results was observed with the stress ratio r = 0; 0.3; 0.6. The difference in the results with the stress ratio r = 0 shows the complexity of the fatigue process as well as the peculiarities of the effect of the nut upon the bolt. According to the experimental data, the length of a non-propagating crack ≈ 5 mm, and the depth exceeds 0.2 mm. Experiments carried out on studs with such cracks showed that non-propagating cracks have no effect on the static strength and fracture takes place in an even part. The determined size of non-propagating cracks is easily measured by means of non-distrusting control methods both under laboratory and operational conditions.
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Sun, Xiaoxiao, Xiaoming Guo, Li Guo, Baijian Wu i Ying Wang. "Multiscale Analysis of Concrete Damage and Crack Propagation Under High Cycle Loading". International Journal of Computational Methods 17, nr 01 (30.09.2019): 1844007. http://dx.doi.org/10.1142/s0219876218440073.
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Concrete is a typical multiphase composite material in which the initiation and propagation of cracks under fatigue load are mainly determined by its mesoscopic structure. In this paper, a concrete multiphase mesoscopic model which considers thickness of interfacial transition zone (ITZ) varying with aggregate’s size is established by the integrated scripting method. The model comprehensively contains the stochastic characteristics of concrete mesoscopic structure. According to the fatigue crack propagation characteristics in different stages, a multiscale method is proposed by establishing the interactive mesoscopic and macroscopic models to targetedly analyze the whole process of fatigue crack initiation, propagation and failure of concrete specimen. Based on the technique of cycle block, concurrent simulation of concrete damage and crack propagation under high-cycle fatigue load is realized. The analysis results show that fatigue cracks in concrete mainly born near the ITZ and gradually enter into the cement mortar matrix to formulate the cracks with finite size. These cracks influence each other until the dominant crack appears and insatiably propagates to result in the failure of specimen.
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Chang, Yan Jun, Shuang Feng Zeng, Ke Shi Zhang i Zhuo Li. "Study of Q345 Steel under Tensile Failure with Bilateral Parallelcracks". Applied Mechanics and Materials 574 (lipiec 2014): 368–72. http://dx.doi.org/10.4028/www.scientific.net/amm.574.368.
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The parallel crackswere prefabricated on both sides of theQ345 steel specimensand the tensile failure tests were performed.The effects of parallel crack spacing and crack length on the crack propagation behavior were studied and the fracture modes were investigated with electronic scanning microscope.The finite element analysis of tensile fracture process was also fulfilled based on the ductile metal damage theory, and the crack propagation and the crack stress field evolution around the crack tips were studied. The simulation was agreed with experimental results, and these analysis shows that the crack propagation related with double crack tip of horizontal distance ratio. When the longitudinal and horizontal distance ratio of the two crack tip is less than 1, the linkage between two cracks occurs, or two cracks expand independently. Simulation analysis shows that cracks deflect and connect with another one when the two high Mises plastic stress zones are met with each other; on the contrary, cracks propagate separately.
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Li, Qingbo, Nengxiong Xu, Weifeng Wan i Yazhe Li. "Modeling of Shear Crack Propagation in Rock Masses Using Mesh-Free LRPIM". Advances in Civil Engineering 2021 (25.03.2021): 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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Sun, Qing Hua, Jin Gen Deng, Zhuo Chen, Yong Meng Xu, Heng Lin Yang i Hai Long Liu. "Analysis of the Formation Mechanism of Crack Network in Shale by CT". Applied Mechanics and Materials 568-570 (czerwiec 2014): 12–18. http://dx.doi.org/10.4028/www.scientific.net/amm.568-570.12.
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During the drilling process of shale gas horizontal well, wellbore instability problem happens frequently. Especially in the horizontal interval, shale which has high levels of gamma is more likely to collapse which lead to delays, and exist certainly collapse period. The development of shale gas is restricted seriously. Research on the formation process of cracks network around the wellbore by CT chromatographic technique. The result reveals that under the condition of uniaxial compression, the cracks initiated inside the shale formation around the wellbore, with the propagation of cracks, between the orientation of cracks and the maximum stress direction will emerge a certain deviated angle. The drilling fluid filtrates into the formation and reduce the strength of rock which will prompt crack propagation and form crack network. Finally the wellbore will collapse with drilling fluid continuous invasion, because the invasion have altered the stress intensity factor at fracture tip, and changed the propagating direction of crack and the friction coefficient of fracture plane, which will reduce the strength of rock and the effective stress of the rock around the wellbore. Crack network dominates the mechanism of instability; mud weight increases do not necessarily lead to a more stable borehole and can further destabilize the wellbore.
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Li, Wen, Ri Dong Liao, Li Tao Liu i Zheng Xing Zuo. "Analysis of Fretting Crack Propagation Behavior with X-FEM Method". Applied Mechanics and Materials 157-158 (luty 2012): 1162–66. http://dx.doi.org/10.4028/www.scientific.net/amm.157-158.1162.
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Fretting fatigue cracks always initial at the tralling of contact region, because the stresses in the vicinity of the contact zone exhibit steep gradients. A fracture mechanics approach is usually used to estimate fretting fatigue propagation life. In this paper, extended finite element method combined with fracture mechanics is used to study fretting crack propagation behaviors. The computation results reveal that fretting crack nucleation is mainly decided by fretting, and the cycle bulk stress is the main reason for crack propagation. Also the X-FEM exhibits merits in fretting fatigue problem.
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Meng, Shang Yang, Jun Li Han, Chang Shun Liu i Xiao Hong Yang. "Stability Analysis of Cracks in the Stress-Release Boot of Solid Rocket Motor Grain with J-Integral". Advanced Materials Research 328-330 (wrzesień 2011): 1210–15. http://dx.doi.org/10.4028/www.scientific.net/amr.328-330.1210.
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The stress-release boot is always used in the fore and rear of SRM grain to relief stress-strain concentration under thermal loading. Since the debonded crack in the stress-release boot may be propagation unstable when the internal pressure entered the debonded crack cavity, the SRM with debonded cracks is very dangerous when it is lunched. So the stability analysis of the debonded cracks is very important to evaluate the defect grain structure integrity. In order to investigate the stability of debonded cracks in the stress-release boot of SRM grain during ignition pressurization, three-dimension (3-D) viscoelastic finite element models of the SRM grain with debonded cracks are established. The 3-D singular crack elements at the tips of cracks are developed to simulate the stress-release boot debonded crack propagation. And all the singular crack elements are included in the 3-D J-integral loop surface to improve the calculation precision. Along with the debonded crack propagation, the 3-D J-integrals of the debonded crack tips are respectively calculated to prejudge its expanding trend. The results show that the most dangerous situation will occur in the fore stress-release boot debonded cracks during the rocket being launched.
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Tong, Fengzhuang, Liang Gao, Xiaopei Cai, Yanglong Zhong, Wenqiang Zhao i Yichen Huang. "Experimental and Theoretical Determination of the Frost-Heave Cracking Law and the Crack Propagation Criterion of Slab Track with Water in the Crack". Applied Sciences 9, nr 21 (29.10.2019): 4592. http://dx.doi.org/10.3390/app9214592.
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Crack propagation produced by frost heave affects the durability of slab-track structures in high-humidity and cold regions in China. This work is intended to reveal the evolution laws of frost-heave crack propagation, establish evaluation criteria for crack propagation, and investigate factors involved in frost-heave crack propagation. Firstly, by preparing slab-track specimens with initial cracks, an experiment of frost-heave crack propagation was designed. The process of frost-heave crack propagation was carried out by means of digital image correlation (DIC) technology and acoustic emission (AE) technology, respectively. These experiments revealed the evolution laws of generalized strain and AE events’ location during crack initiation and propagation, respectively, and the key parameters of micro-crack initiation strain and unstable propagation strain were obtained. By using theoretical and experimental analysis, a double-strain criterion for frost-heave crack propagation was proposed. Finally, factors involved in frost-heave crack propagation were investigated. The results show that crack initiation can be reflected by the crack-tip strain. The average micro-crack initiation strain and unstable propagation strain were found to be 224 με and 243 με, respectively. Moreover, it was found that the frost-heave crack propagation was caused by an ice plug which formed at the crack opening. When the crack width is larger than 2.7 mm and the external temperature is lower than −6.6 °C, cracks propagate easily under the frost-heave force.
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Khan, Md T. I. Islam, A. A. Rashid, R. Hidaka, N. Hattori i Md M. Islam. "Fatigue crack analysis of ferrite material by acoustic emission technique". Journal of Mechanical Engineering and Sciences 13, nr 2 (28.06.2019): 5074–89. http://dx.doi.org/10.15282/jmes.13.2.2019.21.0418.
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Recently in various fields, numerous researches are going on for the assessment of material damage on the basis of crack initiation and propagation. Various methods are available in NDT for this purpose, among which analysis using released acoustic emission (AE) waves due to crack propagation is very effective due to its dynamic monitoring features. Various approaches are proposed for long time to make it an ideal method for accurate monitoring of crack behaviors in materials. In fragmentation theory there are some proportionality among the relations of AE event, AE energy, area and volume of cracks etc., which are calculated from the released AE waves from any dynamic crack. It has been found that the necessity of calculating the fractal dimension is important in verifying these relationships. This parameter is emphasized for determining the geometry of the irregularity in crack surface and crack volume. In this paper a novel approach based on image processing is proposed to find out the fractal dimension for analyzing the crack propagation characteristics. Finally, the proportionality relationships of AE parameters with crack propagation behavior in ferrite cast iron under fatigue loading are demonstrated experimentally.
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Karaszewski, Waldemar. "Numerical Analysis of Crack Propagation in Silicon Nitride". Key Engineering Materials 490 (wrzesień 2011): 216–25. http://dx.doi.org/10.4028/www.scientific.net/kem.490.216.
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The properties of ceramics, specifically low density, high hardness, high temperature capability and low coefficient of thermal expansion are of most interest to rolling element manufacturers. The influence of ring crack size on rolling contact fatigue failure has been studied using numerical fracture analysis. Such cracks are very often found on ceramic bearing balls and decrease fatigue life rapidly. The numerical calculation are based on a three dimensional model for the ring crack propagation. The stress intensity factors along crack front are analyzed using a three-dimensional boundary element model. The numerical analysis is verified by experimental studies.
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Ma, Chien-Ching, i Yi-Shyong Ing. "Transient Analysis of Dynamic Crack Propagation With Boundary Effect". Journal of Applied Mechanics 62, nr 4 (1.12.1995): 1029–38. http://dx.doi.org/10.1115/1.2896039.
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In this study, a dynamic antiplane crack propagation with constant velocity in a configuration with boundary is investigated in detail. The reflected cylindrical waves which are generated from the free boundary will interact with the propagating crack and make the problem extremely difficult to analyze. A useful fundamental solution is proposed in this study and the solution is determined by superposition of the fundamental solution in the Laplace transform domain. The proposed fundamental problem is the problem of applying exponentially distributed traction (in the Laplace transform domain) on the propagating crack faces. The Cagniard’s method for Laplace inversion is used to obtain the transient solution in time domain. Numerical results of dynamic stress intensity factors for the propagation crack are evaluated in detail.
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Zhou, Binpeng, Junrui Chai, Jing Wang, Heng Zhou i Lifeng Wen. "An XFEM-Based Analysis of Concrete Face Cracking in Rockfill Dams". Mathematical Problems in Engineering 2021 (29.07.2021): 1–12. http://dx.doi.org/10.1155/2021/6640668.
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The concrete face of a rockfill dam is a long and thin slab structure, which is highly susceptible to fracture when subjected to the settlement of the dam. The study of the generation and propagation of cracks in the concrete face of rockfill dams is of great significance to dam construction and face crack prevention. In this study, the initiation and propagation of cracks in the concrete face of a rockfill dam are investigated using an extended finite element method (XFEM) and ABAQUS software for the Gongboxia concrete-face rockfill dam. A numerical model for this dam is established using a finite element method, and the face stress and deformation distributions are obtained. Based on the results, a numerical model is built to find the location where cracks are initiated in the face. The displacement of the entire model is treated as the equivalent displacement for the numerical model. XFEM is utilized throughout the modeling process to obtain the stress concentration, crack initiation, and crack propagation in the concrete face, and an analysis of crack initiation and propagation is conducted. Finally, the effects of the thickness of concrete covers and reinforcement layers on the stress intensity of crack tips are also discussed using the established numerical model, and techniques for controlling the fracturing of the concrete face have been proposed in this paper.
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Dirgantara, Tatacipta, Tuppi Summa Wicaksono, Thahir Ahmad, Indra Sadikin, Djoko Suharto i Ichsan Setya Putra. "Probabilistic Fracture Mechanics Analysis of Multiple Cracks in Cylindrical Pressure Vessel". Key Engineering Materials 462-463 (styczeń 2011): 1314–18. http://dx.doi.org/10.4028/www.scientific.net/kem.462-463.1314.
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In this work, a probabilistic fracture mechanics analysis of multiple cracks in a cylindrical pressure vessel was conducted. The analysis was performed to predict service life of a pressure vessel with a certain level of reliability if the vessel has a multiple internal surface cracks that interact each other. The stress intensity factor of multiple cracks configuration was determined from the stress intensity factor of a single surface crack in a plate subjected to uni-axial load and the interaction factor between the cracks. In this work, the Swift’s crack link-up criterion was employed. These parameters together with several other stochastic parameters, i.e. initial crack size, Paris’s crack propagation constants and fracture toughness, were then used to calculate the probability of failure with a certain level of reliability. The failure probability was simulated using guided direct simulation, for cycle-by-cycle crack propagation, to find the expected service life and the mode of failure (leak or break). A case study of a high-pressure vessel having different initial crack sizes have been simulated and the service life with 99,99% reliability were determined.
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Wang, Ying, Zhen Wang i Yuqian Zheng. "Analysis of Fatigue Crack Propagation of an Orthotropic Bridge Deck Based on the Extended Finite Element Method". Advances in Civil Engineering 2019 (25.07.2019): 1–14. http://dx.doi.org/10.1155/2019/6319821.
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As one of the most fatigue-sensitive parts of an orthotropic steel bridge deck, the weld between the U-rib and the top deck is prone to fatigue cracking under the actions of the stress concentration, welding residual stress, and vehicle load. To investigate the mechanism of fatigue crack propagation and the influence of the welding residual stress on the propagation patterns of fatigue cracks, a multiscale modeling method was proposed, and the static analysis and the dynamic propagation analysis of fatigue crack were carried out in this paper. First, a multiscale finite element model was established, including whole bridge models with a scale feature of 102 m, orthotropic bridge deck models with a scale feature of 100 m, and crack models with a scale feature of 10−3 m. Then, a segmental model of the bridge deck was extracted, which is regarded as a critical location of the bridge, and the shell-solid coupling method is adopted in the segmental model in order to further analyze the crack propagation rule. Moreover, based on the extended finite element method (XFEM), the static crack and dynamic crack propagation in this critical position were analyzed. Finally, thermoelastoplastic analysis was carried out on the connection of the U-rib and deck with a length of 500 mm to obtain the residual stress, and then the results of residual stress were introduced into the segmental model to further study its influence on the evolution of fatigue crack propagation. The analysis of the welding process shows that near the weld region of the connection of the U-rib and deck, the peak value of the residual tensile stress can reach the material yield strength. The static analysis of fatigue cracks shows that under the single action of a standard fatigue vehicle load, the fatigue details at the weld toe of the deck cannot reach the tensile stress required for fatigue crack propagation, and only the fatigue details at the weld toe of the U-rib can meet the requirements of fatigue crack propagation. The dynamic analysis of fatigue cracks reveals that the crack in the weld toe of the U-rib is a mixed-mode crack with modes I, II, and III. The propagation of a fatigue crack without a residual stress field will be terminated until the crack length is extended to a certain length. Nevertheless, when the residual stress field was introduced, the growth angle and size of the fatigue crack would increase, and no crack closure occurs. For the crack in the weld toe of the deck, the crack is in the closed state under the standard fatigue vehicle load. When the residual stress field is introduced, the tensile stress of the fatigue details increases. Meanwhile, the fatigue crack will become a mixed-mode crack with modes I, II, and III that will be dominated by mode I and extend toward the weld at a slight deflection angle. The results of various initial crack sizes at the weld toes of the top deck are analyzed, which shows that the initial crack size has a certain effect on the fatigue crack growth rate, especially the initial crack depth.
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Zhang, Xiao Chun, Feng Mei Sun, Yuan Wang i Ning Zhang. "Fracture Mechanics Analysis of Hydraulic Cracks in Asphalt Pavement". Applied Mechanics and Materials 138-139 (listopad 2011): 478–83. http://dx.doi.org/10.4028/www.scientific.net/amm.138-139.478.
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Water damage in asphalt pavement is related to the interaction between cracks and hydrodynamic pressures caused by the vehicle. A 3D finite element model of the hydraulic crack in asphalt pavement was built to analyze the crack propagation character under vehicle load. The influence of asphalt pavement structure parameters, vehicle speed and crack geometric parameters of hydraulic crack were discussed. Then the differences, between aqueous cracks and cracks without water, were compared. The research results had the guiding meaning for anti-water damage design of asphalt pavement.
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Wang, Tingting, Pingfeng Li, Chun’an Tang, Bingbing Zhang i Jiang Yu. "Finite Element Analysis for the Mechanism of Stress Wave Propagation and Crack Extension Due to Blasting of a Frozen Rock Mass". Sustainability 15, nr 5 (4.03.2023): 4616. http://dx.doi.org/10.3390/su15054616.
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The propagation mechanism of explosion stress waves in frozen rock mass is the main factor affecting the blasting efficiency and safety construction of strip mines in alpine cold regions. In order to study explosion stress wave propagation and crack extension in the blasting process of frozen rock mass with ice-filled cracks, RFPA2D is adopted to simulate the influence of the geometric parameters of ice-filled cracks (ice-filled crack thickness d, normal distance R from blasting hole to the ice-filled crack, and ice-filled crack angle α), loading intensity and loading rate on the explosion stress wave propagation effect and the damage range. The results show: The attenuation trend of explosion stress waves decreases gradually with an increase of thickness (e.g., In the case of R is 0.2 m, when d is 0.02 m, 0.04 m, and 0.08 m, the calculated attenuation factor of the minimum principal stress peak value is 7.128%, 18.056%, and 30.035%, respectively), and it decreases slightly with an increase of normal distance and ice-filled crack angle. The damage elements range of the ice-filled crack decreases when the ice-filled crack thickness and normal distance increases. The loading intensity and the loading rate have a significant influence on blasting hole fracture patterns. The ice-filled crack has a guiding effect on the growth of blasting cracks at the blasting hole. Nevertheless, the existence of ice-filled cracks inhibits the propagation of explosion stress waves in frozen rock mass.
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Zhang, Yongpeng, Guangchun Xiao, Chonghai Xu, Tingting Zhou, Mingdong Yi i Zhaoqiang Chen. "Cohesive Element Model for Fracture Behavior Analysis of Al2O3/Graphene Composite Ceramic Tool Material". Crystals 9, nr 12 (11.12.2019): 669. http://dx.doi.org/10.3390/cryst9120669.
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The microstructure model of Al2O3/graphene (AG) composite ceramic tool material is established based on Voronoi tessellation. The cohesive element method was used to simulate the crack growth of AG. The effect of cohesive parameters at the grain boundary of Al2O3 and graphene on the crack propagation was investigated. The results show that the grain strength of graphene is too high, the crack propagation to graphene grains will be hindered and cannot propagate forward. Cracks tend to spread along the paths where the crack propagation drive force was high and the resistance was low. When the interface strength between Al2O3 and graphene was at the weak interface, the crack propagation path and length were relatively straight and short. The average energy release rate G C is 1.042 × 10−3 J/m2, which is 2.4% higher than that of single-phase Al2O3 ceramic tool materials. However, if the interface strength between Al2O3 and graphene was at the strong interface, the crack propagated along graphene particles for a short distance, consuming a large amount of fracture energy. Furthermore, the crack will deflect around graphene grains, which increases the crack propagation length. The average energy release rate G C is 1.039 × 10−3 J/m2, which is 2% higher than that of single-phase Al2O3 ceramic tool materials.
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Dlhý, Pavol, Jan Poduška, Michael Berer, Anja Gosch, Ondrej Slávik, Luboš Náhlík i Pavel Hutař. "Crack Propagation Analysis of Compression Loaded Rolling Elements". Materials 14, nr 10 (19.05.2021): 2656. http://dx.doi.org/10.3390/ma14102656.
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The problem of crack propagation from internal defects in thermoplastic cylindrical bearing elements is addressed in this paper. The crack propagation in these elements takes place under mixed-mode conditions—i.e., all three possible loading modes (tensile opening mode I and shear opening modes II and III) of the crack are combined together. Moreover, their mutual relation changes during the rotation of the element. The dependency of the stress intensity factors on the crack length was described by general parametric equations. The model was then modified by adding a void to simulate the presence of a manufacturing defect. It was found that the influence of the void on the stress intensity factor values is quite high, but it fades with crack propagating further from the void. The effect of the friction between the crack faces was find negligible on stress intensity factor values. The results presented in this paper can be directly used for the calculation of bearing elements lifetime without complicated finite element simulations.
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Berger, J. R., J. W. Dally, R. deWit i R. J. Fields. "A Strain Gage Analysis of Fracture in Wide Plate Tests of Reactor Grade Steel". Journal of Pressure Vessel Technology 115, nr 4 (1.11.1993): 398–405. http://dx.doi.org/10.1115/1.2929547.
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A new method of fracture analysis is described. Strains recorded by gages in the immediate vicinity of a propagating crack are analyzed. From the analysis, crack tip position, propagation toughness, and crack velocity are determined. The analysis procedure Is demonstrated using data from the dynamic fracturing of a large-scale, wide plate test. The results are then used to describe the propagation toughness-crack velocity-temperature relation for the 2.25 Cr-1 Mo steel used in the test.
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Boulenouar, A., N. Benseddiq i M. Mazari. "Two-dimensional Numerical Estimation of Stress Intensity Factors and Crack Propagation in Linear Elastic Analysis". Engineering, Technology & Applied Science Research 3, nr 5 (11.10.2013): 506–10. http://dx.doi.org/10.48084/etasr.363.
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When the loading or the geometry of a structure is not symmetrical about the crack axis, rupture occurs in mixed mode loading and the crack does not propagate in a straight line. It is then necessary to use kinking criteria to determine the new direction of crack propagation. The aim of this work is to present a numerical modeling of crack propagation under mixed mode loading conditions. This work is based on the implementation of the displacement extrapolation method in a FE code and the strain energy density theory in a finite element code. At each crack increment length, the kinking angle is evaluated as a function of stress intensity factors. In this paper, we analyzed the mechanical behavior of inclined cracks by evaluating the stress intensity factors. Then, we presented the examples of crack propagation in structures containing inclusions and cavities.
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Wen, Xin Li, Bo Jiang, Le Yu Zhou, Lie Chen, Hai Long Wang i Ya Zheng Liu. "Splitting Property Analysis of Automotive Con-Rod Steel C70S6". Materials Science Forum 817 (kwiecień 2015): 498–503. http://dx.doi.org/10.4028/www.scientific.net/msf.817.498.
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In order to analysis the splitting property of automotive con-rod steel C70S6, a type of con-rods using this material were manufactured on a domestic production line. Both the fracture and the cracks of the con-rods were observed by SEM, the relationship between the cracks and the grain orientation were analyzed by EBSD. The results show that the fracture of the steel is cleavage fracture and most cleavage planes are {001} , the crack initiation is mainly ferrite or inclusions, and the crack propagation race is along the {001} planes, most microcracks in the vicinity of the main crack induced by the notch can coalesce with it and change its propagation direction, this is the probable formation mechanism of the step-like fracture.
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Chen, Qin, Ya Qi Gong i Yong Feng Qi. "Analysis on Cracking Cause and Propagation Trend of Concrete Dam". Applied Mechanics and Materials 444-445 (październik 2013): 831–35. http://dx.doi.org/10.4028/www.scientific.net/amm.444-445.831.
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Some cracks are observed in a heightening project of a concrete gravity. In order to investigate and solve this problem, the three-dimensional finite element simulation and nonlinear cracking analysis are implemented in this paper to analyze the causes of cracks and their propagation trends. This work is helpful to design the proper crack controlling plans. The research shows that large tensile stress has accumulated during construction, especially after an early air temperature sudden drop in November, the tensile stress increases 3MPa in general on the concrete surface, which exceeds the tensile strength of concrete and causes cracking. Therefore, the crack is the result of both the accumulated temperature stress during construction and temperature sudden drop. The crack will further propagate during another temperature sudden drop, but extended range is limited. If concrete tensile strength is greater than 2.5MPa, the cracks will not penetrate throughout the dam body along the water flow direction.
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Herrmann, H. J., i J. Kertész. "Stability analysis of crack propagation". Physica A: Statistical Mechanics and its Applications 178, nr 2 (październik 1991): 227–35. http://dx.doi.org/10.1016/0378-4371(91)90018-8.
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Alshoaibi, Abdulnaser M. "Fatigue Crack Growth Analysis under Constant Amplitude Loading Using Finite Element Method". Materials 15, nr 8 (18.04.2022): 2937. http://dx.doi.org/10.3390/ma15082937.
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Damage tolerant design relies on accurately predicting the growth rate and path of fatigue cracks under constant and variable amplitude loading. ANSYS Mechanical R19.2 was used to perform a numerical analysis of fatigue crack growth assuming a linear elastic and isotropic material subjected to constant amplitude loading. A novel feature termed Separating Morphing and Adaptive Remeshing Technology (SMART) was used in conjunction with the Unstructured Mesh Method (UMM) to accomplish this goal. For the modified compact tension specimen with a varied pre-crack location, the crack propagation path, stress intensity factors, and fatigue life cycles were predicted for various stress ratio values. The influence of stress ratio on fatigue life cycles and equivalent stress intensity factor was investigated for stress ratios ranging from 0 to 0.8. It was found that fatigue life and von Mises stress distribution are substantially influenced by the stress ratio. The von Mises stress decreased as the stress ratio increased, and the number of fatigue life cycles increased rapidly with the increasing stress ratio. Depending on the pre-crack position, the hole is the primary attraction for the propagation of fatigue cracks, and the crack may either curve its direction and grow towards it, or it might bypass the hole and propagate elsewhere. Experimental and numerical crack growth studies reported in the literature have validated the findings of this simulation in terms of crack propagation paths.
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Wei, Rongbing, Renbing Wu i Kun Zhou. "Fatigue crack propagation in heterogeneous materials under remote cyclic loading". Journal of Micromechanics and Molecular Physics 01, nr 01 (kwiecień 2016): 1650003. http://dx.doi.org/10.1142/s242491301650003x.
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A fatigue model for the analysis of crack propagation in heterogeneous materials is developed. The crack propagation is driven by cyclic loading and affected by the presence of neighboring inclusions which can have initial eigenstrains such as thermal strain and misfit strain. The static Semi-analytic solution obtained by Zhou et al. [2011a] is utilized to obtain the full stress filed and the stress intensity factors. In order to simulate the crack propagation in heterogeneous materials, the maximum hoop stress criterion is applied to predict crack propagation directions and the Paris-type law is employed to analyze the crack fatigue. Meanwhile, a zigzag crack path consisting of many small vertical and horizontal cracks models an arbitrary crack propagation path. The results show that material dissimilarity between the inclusion and matrix and the magnitude of cyclic loading could greatly influence the behaviors of crack propagation.
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Wang, Wenjie, Jie Yang, Haofeng Chen i Qianyu Yang. "Capturing and Micromechanical Analysis of the Crack-Branching Behavior in Welded Joints". Metals 10, nr 10 (29.09.2020): 1308. http://dx.doi.org/10.3390/met10101308.
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During the crack propagation process, the crack-branching behavior makes fracture more unpredictable. However, compared with the crack-branching behavior that occurs in brittle materials or ductile materials under dynamic loading, the branching behavior has been rarely reported in welded joints under quasi-static loading. Understanding the branching criterion or the mechanism governing the bifurcation of a crack in welded joints is still a challenge. In this work, three kinds of crack-branching models that reflect simplified welded joints were designed, and the aim of the present paper is to find and capture the crack-branching behavior in welded joints and to shed light on its branching mechanism. The results show that as long as there is another large enough propagation trend that is different from the original crack propagation direction, then crack-branching behavior occurs. A high strength mismatch that is induced by both the mechanical properties and dimensions of different regions is the key of crack branching in welded joints. Each crack branching is accompanied by three local high stress concentrations at the crack tip. Three pulling forces that are created by the three local high stress concentrations pull the crack, which propagates along with the directions of stress concentrations. Under the combined action of the three pulling forces, crack branching occurs, and two new cracks initiate from the middle of the pulling forces.
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Lewicki, D. G., i R. Ballarini. "Effect of Rim Thickness on Gear Crack Propagation Path". Journal of Mechanical Design 119, nr 1 (1.03.1997): 88–95. http://dx.doi.org/10.1115/1.2828793.
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Analytical and experimental studies were performed to investigate the effect of rim thickness on gear tooth crack propagation. The goal was to determine whether cracks grew through gear teeth or through gear rims for various rim thicknesses. A finite element based computer program (FRANC, FRacture ANalysis Code) simulated gear tooth crack propagation. The analysis used principles of linear elastic fracture mechanics. Quarter-point, triangular elements were used at the crack tip to represent the stress singularity. The program had an automated crack propagation option in which cracks were grown numerically using an automated re-meshing scheme. Crack tip stress intensity factors were estimated to determine crack propagation direction. Gears with various backup ratios (rim thickness divided by tooth height) were tested to validate crack path predictions. Gear bending fatigue tests were performed in a spur gear fatigue rig. From both predictions and tests, gears with backup ratios of 3.3 and 1.0 produced tooth fractures while a backup ratio of 0.3 produced rim fractures. For a backup ratio of 0.5, the experiments produced rim fractures and the predictions produced both rim and tooth fractures, depending on the initial geometry of the crack.
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Pang, John Hock Lye, i You Xiang Chew. "Fatigue Crack Growth and Coalescence Algorithm Starting from Multiple Surface Cracks". Advanced Materials Research 891-892 (marzec 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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Malekan, Mohammad, i Hermes Carvalho. "Analysis of a main fatigue crack interaction with multiple micro-cracks/voids in a compact tension specimen repaired by stop-hole technique". Journal of Strain Analysis for Engineering Design 53, nr 8 (24.04.2018): 648–62. http://dx.doi.org/10.1177/0309324718771124.
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Fatigue is a process in engineering materials in which damage accumulates due to the fluctuating loading. One solution for a component under the fatigue process is to arrest the crack propagation before the final failure using different available retardation methods, such as drilling/stop-hole technique. In addition, structural components may also suffer from the existence of micro-cracks or voids due to their forming process or service lives. These micro-cracks/voids are very critical to study, since they can effectively play an important role in the behavior of the existing main crack in a component. This article aims to investigate the effect of the stop-hole retardation technique and multiple micro-cracks/voids with different characteristic lengths and geometries on the fatigue crack propagation in a compact tension specimen. A modified Forman equation, the so-called NASGRO equation is used to define the transition between crack initiation and crack growth period. Also, the extended finite element method is adapted in the crack propagation phase in order to model crack path in the geometry eliminating the need for remeshing procedure. The whole analyses are conducted in a commercial package through a user-written code that handles all fatigue crack growth analysis. The reference solutions from the literature are used to compare and to validate results obtained from current work.
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Changfang, Zhao, Ren Rui, Wei Yi, Yang Guang, He Bin, Zhang Kebin i Zhong Jianlin. "Crack Propagation for Glass Fiber Reinforced Laminates Containing Flame Retardant: Based on Single-Edge Tensile Loading". Materiale Plastice 59, nr 2 (1.07.2022): 88–99. http://dx.doi.org/10.37358/mp.22.2.5588.
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Research on crack propagation for fiber reinforced composites containing flame retardant is rare. The micro-cracks propagation is a reason for delamination and debonding failure of fiber reinforced composites. To study the crack propagation of continuous glass fiber reinforced epoxy resin laminates that contained ammonium polyphosphate flame retardant (GFRP-APP), the quasi-static single-edge tensile loading (SETL) experiments for the end-notched GFRP-APP specimens were carried out by MTS universal electronic testing machine. The crack propagation of the end-notched 90� GFRP-APP specimen includes two types, both of which belong to opening type (mode I). Namely, one type is mode I multi-cracks propagation without preexisting crack, and the other is mode I fiber bridge propagation with preexisting crack. The intralaminar fracture toughness along fiber direction of GFRP-APP is approximately 8.4 N/mm, which is calculated by area method. The opening displacement-tensile force curves can be divided into three stages for 90� GFRP-APP specimen without crack, i.e., crack gestation, crack birth and crack propagation. However, the 90� GFRP-APP specimen with crack not contains the crack birth stage. Additionally, the microscopic morphology for the fracture face of pure epoxy resin and GFRP-APP, and the phase analysis for GFRP-APP were performed by scanning electron microscope (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). As a conclusion, the pores and interfaces in materials were the guiding factors of micro-crack propagation, and the ammonium polyphosphate flame retardant particle contributed extra interfaces.
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Wang, Da, Benkun Tan, Shengtao Xiang i Xie Wang. "Fatigue Crack Propagation and Life Analysis of Stud Connectors in Steel-Concrete Composite Structures". Sustainability 14, nr 12 (14.06.2022): 7253. http://dx.doi.org/10.3390/su14127253.
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To investigate the fatigue performance of the stud connectors of steel-concrete structures, fatigue crack propagation analysis and fatigue life calculation were carried out. Firstly, the finite element model with the initial crack based on linear elastic fracture mechanics (LEFM) was established, and the parameter analysis of the stress intensity factors (SIFs) of the studs and cracks with different geometric sizes was performed. Then, the propagation with mixed-type fatigue crack and I-type fatigue crack of the stud were calculated, and the variation of effective SIFs with the fatigue crack depth was analyzed. Finally, the flow chart of stud fatigue life evaluation which considers crack initiation and stable propagation was presented, and the short stud of steel-UHPC composite structures was taken as an example and verified. The calculation results show that the fatigue crack propagation type and the initial crack have an obvious influence on the fatigue life of the stud. It has acceptable accuracy that the fatigue life of short stud in UHPC simulated by considering the crack initiation. The critical damage parameters are greatly affected by the fatigue stress amplitude, and the initiation life of fatigue crack can account for more than 90% of the total fatigue life. This paper can provide a reference for evaluating the fatigue performance of studs in steel-concrete composite structures. Accurate evaluation of the fatigue life of stud connectors conforms to the concept of sustainable development.
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Yuan, Zhe, Bohan Wang, Chao Liu, Zhan Wang, Xiaochen Zhang i Yu Zhang. "The Crack Propagation Trend Analysis in Ceramic Rolling Element Bearing considering Initial Crack Angle and Contact Load Effect". Shock and Vibration 2021 (29.07.2021): 1–12. http://dx.doi.org/10.1155/2021/5559296.
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Silicon nitride ceramic bearings are widely used for their excellent performance. However, due to their special manufacturing method, cracks will occur on ceramic ball surface, and this initial surface crack will propagate under the action of cyclic stress, which will lead to material spalling. This will greatly limit its service life in practical applications, especially under heavy load at high speed. Therefore, it is necessary to study the surface crack propagation of silicon nitride ceramic bearings. In this paper, the effect of initial crack angle and contact load on crack growth is analysed by the finite element method (FEM). A three-dimensional finite element model of a silicon nitride bearing ball containing an initial crack is created by the FEM. The cracks are initially classified based on the angle between the crack and the bearing ball surface, and the location of the most dangerous load for each type of crack is known by theoretical analysis. The stress intensity factors (SIFs) are calculated for the crack front to investigate the effect of load position on crack growth. Subsequently, the SIFs are calculated for each type of crack angle subdivided again to investigate the effect of crack angle on crack propagation.
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Ju, Xiao Chen, i Tateishi Kazuo. "Experimental Study on Fatigue Crack Propagation of through-Thickness Crack under Out-of-Plane Bending". Applied Mechanics and Materials 166-169 (maj 2012): 1277–83. http://dx.doi.org/10.4028/www.scientific.net/amm.166-169.1277.
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In Japan, fatigue through-thickness cracks have been reported in steel bridges. Some of the cracks are originated by out-of-plane bending. For performing more efficient maintenance against the fatigue damages, it is essential to identify the crack propagation behavior of the through-thickness crack under out-of-plane bending. As an important factor to assess the crack propagation behavior, generally, stress intensity factor for through-thickness crack under bending was determined by some assumptions that crack front shape is straight in thickness direction. However, the actual crack front is curved under out-of-plane bending. In this paper, in order to identify the propagation behavior of through-thickness crack under out-of-plane bending, the fatigue test on through-thickness cracked plate was carried out. Moreover, through finite element analysis on the test specimen, the stress intensity factor along curved crack front was investigated.
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Gallego, Rafael, i Jose´ Dominguez. "Dynamic Crack Propagation Analysis by Moving Singular Boundary Elements". Journal of Applied Mechanics 59, nr 2S (1.06.1992): S158—S162. http://dx.doi.org/10.1115/1.2899481.
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An efficient boundary element procedure for the dynamic analysis of crack propagation in unbounded and arbitrary shape finite bodies is presented. The procedure is based on the direct time domain formulation of the boundary element method. A moving singular element and a remeshing technique have been developed to model the asymptotic solution of the stresses near the propagating crack tip. These ideas are easily implemented for a boundary discretization as opposed to similar procedures previously developed in a finite element context. The method is applied to problems of dynamic crack propagation in finite and infinite elastic domains. The obtained numerical results are compared with infinite domain analytical solutions and with available numerical solutions for finite domains.
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Linz, Mathias, Franz Walzhofer, Stefan Krenn, Andreas Steiger-Thirsfeld, Johannes Bernardi, Horst Winkelmann i Ewald Badisch. "Surface crack propagation and morphology in cutting tools". Industrial Lubrication and Tribology 68, nr 1 (8.02.2016): 141–48. http://dx.doi.org/10.1108/ilt-10-2015-0144.
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Purpose – The purpose of this paper is to investigate the driving mechanisms for crack propagation regarding the related microstructures. Cracks in white etching layers have been found at the surface of submerged steel blades subjected to frictional sliding conditions. Design/methodology/approach – In-situ monitoring revealed a fluctuation between mixed lubrication and hydrodynamic lubrication conditions. One lamella including a crack tip was prepared for transmission electron microscopy (TEM) using focused ion beam milling. Transmission electron microscope analysis was performed with the aim to understand the characteristics of the crack propagation, especially considering the influence of the microstructural configuration (grain refinement, carbides, martensite and ferrite grains). Findings – The investigations have shown a grain-refined plastically deformed layer (friction martensite with grain sizes of < 100 nm) which influences the propagation direction of cracks introduced at the frictionally stressed surface. Thereby, the crack propagation is dominantly parallel to the margin of the grain-refined martensitic layer at the surface and the base material. Cracks were split into side cracks what mostly appears at present carbides. In this case, the crack propagation might strike through the carbide or separate it from the matrix due to the mechanical misfit. Originality/value – For obtaining the results of this paper, a very special preparation of tribologically stressed samples was performed. Accordingly, specific findings of the crack propagation behavior under such conditions were achieved and are documented in the presented work. Moreover, the described crack propagation process is a combination of several mechanisms which occur in very limited region underneath the surface and are investigated by high-resolution TEM.
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Chen, Juntao, Yi Zhang, Kai Ma, Daozeng Tang, Hao Li i Chengxiang Zhang. "Analysis of Mining Crack Evolution in Deep Floor Rock Mass with Fault". Geofluids 2021 (3.12.2021): 1–15. http://dx.doi.org/10.1155/2021/5583877.
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To further explore the crack evolution of floor rock mass, the mechanism of fault activation, and water inrush, this paper analyzes the crack initiation and propagation mechanism of floor rock mass and obtains the initiation criteria of shear cracks, layered cracks, and vertical tension cracks. With the help of simulation software, the process of fault activation and crack evolution under different fault drop and dip angles was studied. The results show that the sequence of crack presented in the mining rock mass is vertical tension cracks, shear cracks, and layered cracks. The initiation and propagation of the shear cracks at the coal wall promote the fault activation, which tends to be easily caused at a specific inclination angle between 45° and 75°. The fault drop has no obvious impact on the evolution of floor rock cracks and will not induce fault activation. However, the increase of the drop will cause the roof to collapse, reducing the possibility of water inrush disaster. Research shows that measures such as adopting improved mining technology, reducing mining disturbance, increasing coal pillar size, and grouting before mining as reinforcement and artificial forced roof can effectively prevent water inrush disasters caused by deep mining due to fault activation.
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Kumar, Pramod, i Ashish Kakyal. "Simulation of Cracks in Fiber Reinforced Composite Plate". Key Engineering Materials 471-472 (luty 2011): 892–97. http://dx.doi.org/10.4028/www.scientific.net/kem.471-472.892.
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Material flaws, pre-cracks and crack initiation due to cyclic loading often lead to undetected crack propagation in commercial structures like aircraft components, automotive parts and computer motherboard. Cyclic loading can make the crack grow large into any shape with an arbitrary orientation, depending on the structure geometry, boundary and loading conditions. Since crack propagation in many cases may lead to catastrophic failure with human and monetary loss as a result, it is important to enable crack growth prediction at all stages of development and during maintenance in order to prevent such scenarios. Micro mechanical approach is used for modelling the crack in composite materials. Crack propagation in a single edge crack plate is carried out by using FEM analysis. 2D model is analysed to determine the crack growth. The crack propagation rate, stress intensity factor and strain energy release rate are predicted by varying the crack length in fiber reinforced epoxy composite using NISA/ENDURE.
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Karaszewski, Waldemar. "Hertzian Crack Propagation in Ceramic Rolling Elements". Key Engineering Materials 598 (styczeń 2014): 92–98. http://dx.doi.org/10.4028/www.scientific.net/kem.598.92.
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The properties of ceramics, specifically low density, high hardness, high temperature capability and low coefficient of thermal expansion are of most interest to rolling element manufacturers. The influence of ring crack size on rolling contact fatigue failure has been studied using numerical fracture analysis. Such cracks are very often found on ceramic bearing balls and decrease fatigue life rapidly. The numerical calculation are based on a three dimensional model for the ring crack propagation. The stress intensity factors along crack front are analyzed using a three-dimensional boundary element model. The numerical analysis is verified by experimental studies.