Journal articles on the topic 'Crack propagation'
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1
Peng, Yanyan, Xiao Cheng, Nan Song, Qi Qin, Xiaoyun Zhang, and Manchao He. "Study on Crack Propagation and Coalescence in Fractured Limestone Based on 3D-DIC Technology." Energies 15, no. 6 (March 9, 2022): 2007. http://dx.doi.org/10.3390/en15062007.
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To deeply understand the influence of crack inclination angle on crack propagation and coalescence in fractured limestone, uniaxial compression tests were carried out on limestone specimens with prefabricated cracks. The strain field evolution diagram of the failure process of the specimens was obtained using 3D digital image correlation technology (3D-DIC technology). This, in combination with the crack propagation diagram, was used to analyze the entire failure process of the limestone specimens. The test results show that the evolution process of the principal strain field agrees well with the process of crack initiation, propagation, and coalescence. The crack development process is the process of the high strain zones consistently propagating and also the process of micro-cracks appearing, developing, and nucleating to form macro-cracks. With the increase in the parallel crack inclination angle, the stress concentration zone of the intermediate crack transfers from both ends of the crack to the middle. Meanwhile, the coalescing crack type between the parallel crack and the intermediate crack changes from a coexisting tensile crack and tensile-shear crack to a single tensile crack. With the increase in the parallel crack inclination angle, the failure of the fractured limestone specimens changes from simple splitting or tensile failure to the coexistence of tensile-shear fracture and splitting. 3D-DIC technology provides an effective method to study crack propagation and coalescence during rock failure.
2
Liu, Bang, Zheming Zhu, Ruifeng Liu, Lei Zhou, and Duanying Wan. "Study on the Fracture Behavior of Cracks Emanating from Tunnel Spandrel under Blasting Loads by Using TMCSC Specimens." Shock and Vibration 2019 (May 20, 2019): 1–13. http://dx.doi.org/10.1155/2019/2308218.
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Radial cracks may exist around tunnel edge, and these cracks may propagate and weaken tunnel stability under nearby blasting operations. In order to study the blast-induced fracture behavior of radial cracks emanating from a tunnel spandrel, a tunnel model containing a spandrel crack (TMCSC) with different inclination angles was proposed in this paper. Crack propagation gauges (CPGs) and strain gauges were used in the experiments to measure crack initiation moment and propagation time. Finite difference models were established by using AUTODYN code to simulate crack propagation behavior and propagation path. ABAQUS code was used to calculate dynamic stress intensity factors (SIFs). The results show that (1) crack inclination angles affect crack initiation angles and crack propagation lengths significantly; (2) critical SIFs of both mode I and mode II decrease gradually with the increase of the crack propagation speed; (3) the dynamic energy release rates vary during crack propagation; and (4) there are “crack arrest points” on the crack propagation paths in which the crack propagation speed is very small.
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Xu, Xiaoqing, Bohan Liu, and Yibing Li. "Investigation on Dynamic Propagation Characteristics of In-Plane Cracks in PVB Laminated Glass Plates." Advances in Materials Science and Engineering 2016 (2016): 1–13. http://dx.doi.org/10.1155/2016/1468390.
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Polyvinyl butyral (PVB) laminated glass has been widely used as an important component of mechanical and construction materials. Cracks on PVB laminated glass are rich in impact information, which contribute to its impact resistance design. In this paper, a three-dimensional (3D) numerical simulation model describing PVB laminated glass under impact loading is firstly established and validated qualitatively and quantitatively compared with the corresponding experimental results recorded by the high-speed photography system. In the meantime, the extended finite element method (XFEM) is introduced to analyze the crack propagation mechanism of laminated glass based on dynamic stress intensity factors (DSIFs) and propagations of stress waves. Parametric studies are then carried out to investigate the influence of five critical parameters, that is, plate dimension, crack length, impact energy, glass properties, and PVB properties, on crack propagation characteristics of laminated glass. Results show that the interaction between crack tip and stress waves as well as the propagations of stress waves corresponds to the fluctuations of DSIFs at crack tip. Both the structure and material variables are proven to play a very important role in glass cracking DSIFs and thus govern the crack propagation behavior. Results may provide fundamental explanation to the basic crack propagation mechanism on radial cracks in PVB laminated glass under impact loading conditions, thus to instruct its impact design improvement.
4
Wang, Siyao, and Shaowei Hu. "Experimental Study of Crack Propagation in Cracked Concrete." Energies 12, no. 20 (October 12, 2019): 3854. http://dx.doi.org/10.3390/en12203854.
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The intersection of cracks has an important role in the key technology of hydraulic fracturing for enhancing the recovery of tight hydrocarbon reservoirs. On the basis of digital image correlation technology, three-point bending tests of concrete beams with an edge crack and a central preset crack were conducted to investigate the propagation of cracks after intersection in concretes. Concrete beams with cracks of different positions, lengths, and approach angles were tested, and results were analyzed. In conclusion, the crack positions, crack lengths, and approach angles significantly influence the crack propagation in naturally cracked concrete. A large distance between the crack tip and central point at the preset transverse crack and crack length indicate a high possibility of the edge crack vertically crossing the preset crack. In particular, the crack restarts from the preset crack tip after intersection when the distance between two cracks is smaller than 30 mm and when the preset crack length is smaller than 40 mm. A large approach angle corresponds to a large carrying capacity of the beam and a high possibility of the crack propagating perpendicularly. An improved criterion of restart cracking after interaction is proposed, and the restart points of all tested beams are predicted and compared with the experimental results. A good agreement is observed, which proves that this criterion is reliable.
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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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Sun, Yazhen, Ting Yan, Changyu Wu, Xiaofang Sun, Jinchang Wang, and Xuezhong Yuan. "Analysis of the Fatigue Crack Propagation Process of the Stress-Absorption Layer of Composite Pavement Based on Reliability." Applied Sciences 8, no. 11 (October 30, 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.
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Wang, Xi Shu, Jing Hong Fan, Bi Sheng Wu, and Ying Li. "Effects of Distance and Alignment Holes on Fatigue Crack Behaviors of Cast Magnesium Alloys." Advanced Materials Research 33-37 (March 2008): 13–18. http://dx.doi.org/10.4028/www.scientific.net/amr.33-37.13.
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To study the fatigue microcrack initiation and propagation behaviors of cast magnesium alloys, the small fatigue crack propagation tests were carried out using the in-situ observation with scanning electron microscope (SEM). All initiations and propagations of fatigue small cracks focused on effects of the interaction of artificial two small holes, which there are the different distances and alignments of two small holes. The results indicate that the fatigue small cracks of cast magnesium alloys occurred mainly at the defects or root of notch but the early stage crack propagations were influenced on the distance and alignment between two small holes. For cast AM50 and AM60B alloys, the fatigue small cracking prior to occurred at the weak dendrite boundary and had some concomitances such as the plastic deformation on surface of α-Mg phase. For AZ91 alloy, the fatigue cracking characterization depended mainly on the brittle properties of β-Mg17Al12 phase, which the multi cracks occurred at the boundaries of β-Mg17Al12 phase. The effect of notch on the fatigue cracking behavior becomes weaker when the radius of notch is over 3-4 times than that of average α-Mg grain size. The fatigue crack propagation behaviors varied with the different arrangements of two small holes. The effects of distance and alignment of two small holes on the fatigue crack propagation behaviors are also obvious.
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Tong, Fengzhuang, Liang Gao, Xiaopei Cai, Yanglong Zhong, Wenqiang Zhao, and 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, no. 21 (October 29, 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.
9
Yang, Hang, Weiqing Zhang, Ning Wang, and Rulong Tan. "Analysis of crack propagation and life estimation of spiral bevel gears with root cracks." Journal of Physics: Conference Series 2787, no. 1 (June 1, 2024): 012032. http://dx.doi.org/10.1088/1742-6596/2787/1/012032.
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Abstract In order to study the effect of tooth root cracks on the fatigue life of spiral bevel gears, a certain spiral bevel gear was taken as the research object, and the mechanism of tooth root fatigue cracks was analyzed based on crack propagation theory; By combining the extended finite element method and the level set method, an initial crack propagation finite element model is established. The crack location of the gear teeth is determined through static analysis of the gear pair, and the influence of alternating loads on the initiation and propagation life of tooth surface cracks is studied. The analysis results indicate that the number of load cycles required for each crack propagation after its first occurrence gradually decreases; The crack propagation path of gear cracks under fatigue load is consistent with the actual tooth surface fracture surface; Realize life estimation from crack propagation to fracture failure.
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Buck, Otto. "Crack Formation and Propagation." MRS Bulletin 14, no. 8 (August 1989): 16–17. http://dx.doi.org/10.1557/s0883769400061911.
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After Griffith's explanation of the decrease in the strength of a loaded material containing a disbonded area (a crack), it took about another quarter century before “Fracture Mechanics” as an engineering discipline became established. At that time it was the catastrophic failure of the Liberty ships and the basic contributions by Irwin2 that created a high interest in the quantification of the process by which a crack will grow. A series of accidents involving bridges, pressure vessels, generator rotors, aircraft, etc., contributed greatly — not only to further research but also to the opinion that cracks are basically “bad” and should be avoided under all circumstances.I started to become acquainted with cracks in the early 1970s. The U.S. Air. Force had recently lost a few F-lll aircraft in southeast Asia due to wing-box cracking. In reaction, the Air Force decided that the new bomber, the B1, should be designed according to fatigue and fracture criteria. Since the materials were specified mostly by metallurgical engineers, they had to become concerned with the effects, for example, of the materials' microstructures on fatigue and crack propagation. At the same time, the interest in crack formation began to evolve.Furthermore, the capabilities for quantitative nondestructive evaluation of a structure in service increased sharply since it was realized that we have to live with cracks and that not all cracks are necessarily “bad.”
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Yu, Shengjie, Di Gai, Lei Zhang, Zheng Zhao, Zhipeng Yao, and Shiyu Yang. "Simulation of tensile fatigue crack propagation in carbon fiber unidirectional laminates under progressive fatigue damage model." Journal of Physics: Conference Series 2783, no. 1 (June 1, 2024): 012052. http://dx.doi.org/10.1088/1742-6596/2783/1/012052.
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Abstract This paper predicts and analyzes the tensile fatigue crack propagation of carbon fiber reinforced unidirectional laminates at high-stress levels using the carbon fiber stiffness strength degradation formula. The results show that different paving modes significantly affect crack propagation and stress distribution. Under the 45° layup, two cracks appeared. The upper crack expanded along the fiber direction, and the lower crack first appeared as a horizontal crack at the constrained end and then along the fiber direction. Under 0° layering, vertical cracks appear at the prefabricated crack tip, and the crack direction is the same as the loading direction. At a -45° layup, two cracks appeared at the prefabricated crack tip, and then the lower crack extended to the integral separation of the test piece. In addition, the strain characteristic analysis shows that the strain increases and decreases rapidly during crack propagation. This study has a certain reference value for further understanding of fatigue crack propagation characteristics of carbon fiber-reinforced composites.
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Shao, Peng, Yong Zhang, Wen Ming Gao, and Yong Qiang Liu. "Dynamic Response of Intermittent Jointed Rock Mass Subjected to Blast Waves." Key Engineering Materials 306-308 (March 2006): 1415–20. http://dx.doi.org/10.4028/www.scientific.net/kem.306-308.1415.
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The propagation of blast waves in intermittent jointed rock masses will result in a complex interaction between propagating waves and rock joints. Such being the case, the analysis of dynamic response of rock masses is important to rock engineering design and stability prediction. In this paper, the fracture process of intermittent jointed rock mass subjected to blast waves and initial static field, including wing crack initiation, propagation and arrest, is analyzed using linear superposition principle and sliding crack model. Crack initiation conditions and propagation lengths under incident P-waves is put forward, and the kinking effect of propagating wing cracks subjected to S-wave is also discussed. Additional, it is demonstrated that crack arrest is controlled by static field. In order to validate the correctness of dynamic response analysis, experimental investigations were performed using lucite specimens, and the experimental results show good agreement with the analytical results.
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Gao, Ruipeng, Mengmeng Liu, Bing Wang, Yiran Wang, and Wei Shao. "Influence of Stress Intensity Factor on Rail Fatigue Crack Propagation by Finite Element Method." Materials 14, no. 19 (September 30, 2021): 5720. http://dx.doi.org/10.3390/ma14195720.
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Wheel rail rolling contact fatigue is a very common form of damage, which can lead to uneven rail treads, railhead nuclear damage, etc. Therefore, ANSYS software was used to establish a three-dimensional wheel–rail contact model and analyze the effects of several main characteristics, such as the rail crack length and crack propagation angle, on the fatigue crack intensity factor during crack propagation. The main findings were as follows: (1) With the rail crack length increasing, the position where the crack propagated by mode I moved from the inner edge of the wheel–rail contact spot to the outer edge. When the crack propagated to 0.3–0.5 mm, it propagated to the rail surface, causing the rail material to peel or fall off and other damage. (2) When the crack propagation angle was less than 30°, the cracks were mainly mode II cracks. When the angle was between 30 and 70°, the cracks were mode I–II cracks. When the angle was more than 70°, the cracks were mainly mode I cracks. When the crack propagation angle was 60°, the equivalent stress intensity factor reached the maximum, and the rail cracks propagated the fastest.
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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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Wan, Duanying, Zheming Zhu, Changlin Zhou, Jianfei Li, Peng Ying, and Meng Wang. "Effect of Pre-Existing Symmetrical Cracks on Propagation Behaviors of a Blast-Induced Crack." Shock and Vibration 2020 (August 7, 2020): 1–16. http://dx.doi.org/10.1155/2020/5892324.
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Defects such as voids, pores, and joints will transform into big scale cracks in the rock of tunnel surrounding under dynamic load like blasting and earthquake. In this paper, three kinds of symmetrical cracks were chosen as an example, and experiments and numerical simulations were conducted to study the effect of symmetric cracks on a blast-induced crack. The relationship of main crack propagation characteristic and distribution of symmetrical cracks was investigated. Some circular specimens using two kinds of material, PMMA and sandstone, including a center hole charged with a detonator and pre-existing cracks were used in the experiments. The test system consisted of an oscilloscope and an ultradynamic strain amplifier and crack propagation gauges (CPGs) were employed in monitoring propagation velocity. AUTODYN code was applied in numerical simulation to investigate the propagation behavior of main crack between symmetrical cracks. Linear equation of state and a modified major principal stress failure criterion was utilized to describe the status of rock material. Based on experimental and numerical results, it can be concluded that (1) the pre-existing symmetrical cracks have arrest effect on main crack propagation, (2) compressive stress in y-direction plays very important roles in crack arrest, and (3) the spacing of parallel cracks has a great influence on crack propagation length and velocity.
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Sakane, Masao, Kazuhiro Itoh, Yutaka Tsukada, and Kenji Terada. "Crack Propagation Behavior at Sn37Pb-Copper Interface in Low Cycle Fatigue." Key Engineering Materials 353-358 (September 2007): 2962–65. http://dx.doi.org/10.4028/www.scientific.net/kem.353-358.2962.
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This paper studies the crack propagation at Sn37Pb-copper interface in push-pull low cycle fatigue. Bonded specimens of Sn37Pb and copper having notch holes with different distances from the interface were fatigued at 313K and the crack propagation paths were observed. Cracks propagated at the interface when the notch hole was near the interface but propagated in the solder when the notch hole was away from the interface. The propagation rate of the interfacial crack was faster than that of non-interface crack. The crack path and crack propagation rate of the two types of cracks were discussed in relation to J integral range calculated by finite element method.
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Zouhar, Michal, Pavel Hutař, Luboš Náhlík, and Zdeněk Knésl. "Basic Modes of Crack Propagation through the Interface in a Polymer Layered Structure." Key Engineering Materials 488-489 (September 2011): 162–65. http://dx.doi.org/10.4028/www.scientific.net/kem.488-489.162.
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The multi-layered structure components of dissimilar materials are used in many engineering applications to protect the base structure from outer damage. Typical examples of coated structures are pipes with the dimensional addition of protective layers (multi-layer pipes). The purpose of this development is to protect the main (functional) part of the pipes from damages (e.g. surface scratches, internal crack propagation). In the contribution the attention is paid to cracks existing and propagating in inner protective layer. In many cases the cracks are stopped at the interface between protective and functional layers. The important task is to decide if they penetrate further through the interface in the bulk material and thus cause the failure of the system. The critical stress for the crack propagation through the interface depends on the relation between bulk and coating materials as well as on the crack geometry. All these important topics are taken into account and their effect on crack propagation is broadly discussed.
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Aoki, Y., T. Matsuyama, Yasuji Oda, Kenji Higashida, and Hiroshi Noguchi. "Effects of Hydrogen Gas Environment on Non-Propagation Phenomena of a Type 304 Austenitic Stainless Steel." Key Engineering Materials 297-300 (November 2005): 927–32. http://dx.doi.org/10.4028/www.scientific.net/kem.297-300.927.
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In order to investigate the hydrogen gas effect on non-propagation phenomena of a type 304 austenitic stainless steel, fatigue tests with in-situ observation using a Scanning Laser Microscope were performed in air, in 0.18MPa hydrogen gas and in 0.18MPa nitrogen gas. A nonpropagating crack was observed during the fatigue test in air. At almost the same stress level of non-propagating in air, non-propagating cracks were also observed in fatigue tests in hydrogen and in nitrogen. Stress level of the non-propagation is not sufficiently different in the three environments. However, the process up to non-propagation differs from each other, for example, the crack path and debris.
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Ballarini, R., and S. Muju. "Stability Analysis of Bridged Cracks in Brittle Matrix Composites." Journal of Engineering for Gas Turbines and Power 115, no. 1 (January 1, 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.
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Kim, Hyo Jin, Sang Ho Lee, and Moon Kyum Kim. "Prediction of Crack Propagation under Dynamic Loading Conditions by Using the Enhanced Point Collocation Meshfree Method." Key Engineering Materials 324-325 (November 2006): 1059–62. http://dx.doi.org/10.4028/www.scientific.net/kem.324-325.1059.
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An efficient and accurate numerical program with enhanced point collocation meshfree method is developed to simulate crack propagation under dynamic loading conditions. The enhanced meshfree method with point collocation formulation and derivative approximation in solids is presented. This study also presents the crack propagation criterion and computation of propagating direction, and the total structure of the numerical program named PCMDYC(Point Collocation Meshfree method for DYnamic Crack propagation). Several examples of crack propagation under dynamic loads are analyzed to simulate the arbitrary crack propagation under dynamic loads. The results show that PCMDYC predicts the propagating path of crack under dynamic loading conditions accurately and robustly.
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Wang, Wei, Yanfang Yang, Mengzhen Li, Weikai Liu, and Zhiping Liu. "Prediction of fatigue crack propagation based on dynamic Bayesian network." Advances in Mechanical Engineering 14, no. 11 (November 2022): 168781322211364. http://dx.doi.org/10.1177/16878132221136413.
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To address the problem of low prediction accuracy in the current research on fatigue crack propagation prediction, a prediction method of fatigue crack propagation based on a dynamic Bayesian network is proposed in this paper. The Paris Law of crack propagation and the extended finite element method (XFEM) are combined to establish the state equation of crack propagation. The uncertain factors of crack propagation are analyzed, and the prediction model of fatigue crack propagation based on the dynamic Bayesian network is constructed. A Bayesian inference algorithm based on the combination of Gaussian particle filter and firefly algorithm is proposed. The fatigue experiment of the specimen with the pre-cracks is carried out to test the correlation between the fatigue load cycles and the crack propagation depth. The experimental results show that the crack propagation prediction method proposed in this paper can effectively improve the prediction accuracy of crack propagation depth.
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Wang, Chaolin, Yu Zhao, Yanlin Zhao, and Wen Wan. "Study on the Interaction of Collinear Cracks and Wing Cracks and Cracking Behavior of Rock under Uniaxial Compression." Advances in Civil Engineering 2018 (2018): 1–10. http://dx.doi.org/10.1155/2018/5459307.
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This paper investigates the crack interaction, initiation, and propagation rules of rock-like materials containing two collinear cracks. Based on the Kachanov method, the formulations for stress intensity factors (SIFs) of two collinear cracks and two winged cracks are derived, respectively. The influences of bridge ligament and crack length on the crack interaction are analyzed theoretically. The results show that the propagation of a long crack is independent of crack interaction when d≥a2 and the same rule applies for a short crack when d≥a1. With the growth of wing cracks, the SIF of wings first remarkably decreases and then it tends toward a steady value. Subsequently, the propagation of collinear cracks and cracking processes under uniaxial compression are analyzed experimentally and numerically. Both the experimental results and simulation results demonstrate that shear cracks tend to initiate and propagate at higher inclination angle. The crack coalescence is affected by the inclination angle of bridge ligament. For increasing the inclination angle, the crack coalescence varies from wing crack failure to shear crack coalescence. As bridge ligament increases, the crack coalescence varies from shear crack coalescence to shear-wing crack coalescence and then to wing crack failure.
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Chao, Xu, and Shang Lei Yang. "Analysis on Fatigue Crack Propagation and Fractography of A7075 Aluminum Alloy." Applied Mechanics and Materials 217-219 (November 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.
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Zhu, Yong, Ray K. L. Su, and Qi Cai Yu. "Initial Crack Propagation Directions of Branched Crack under Tension with Finite Element Analysis." Advanced Materials Research 168-170 (December 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.
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Lukács, János, and Marcell Gaspar. "Fatigue Crack Propagation Limit Curves for High Strength Steels and their Application for Engineering Critical Assessment Calculations." Advanced Materials Research 891-892 (March 2014): 563–68. http://dx.doi.org/10.4028/www.scientific.net/amr.891-892.563.
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There are different prescriptions containing fatigue crack propagation limit curves and rules for the prediction of the crack growth. The research work aimed (i) to determine fatigue crack propagation limit curves for high strength steels and their welded joints, based on the Paris-Erdogan law; (ii) to use the determined limit curves for engineering critical assessment (ECA) calculations. Experiments were performed on different high strength steels and their welded joints; and the propagating cracks in the specimens represent the different possible locations of the real cracks in the structural elements. Fatigue crack growth tests were executed byΔK-decreasing and constant load amplitude methods. The evaluation process consists of six steps, and by means of the selected values a statistical method can be proposed for determination of the limit curves. Engineering critical assessment calculations were performed on a welded structural element having crack like defects.
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Salehizadeh, H., and N. Saka. "Crack Propagation in Rolling Line Contacts." Journal of Tribology 114, no. 4 (October 1, 1992): 690–97. http://dx.doi.org/10.1115/1.2920937.
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The stress intensity factors for short straight and branched subsurface cracks subjected to a Hertzian loading are calculated by the finite element method. The effect of crack face friction on stress intensity factors is considered for both straight and branched cracks. The calculations show that the straight crack is subjected to pure mode II loading, whereas the branched crack is subjected to both mode I and mode II, with ΔKI/ΔKII < 0.25. Although KI is small, it strongly influences KII by keeping the branched crack faces apart. Based on the ΔKII values and Paris’s crack growth model, the number of stress reversals required to grow a crack in a rolling component from an initial threshold length to the final spalling length was estimated. It was found that the crack propagation period is small compared with the expected bearing fatigue life. Therefore, crack propagation is not the rate controlling factor in the fatigue failure of bearings operating under normal loading levels.
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Shen, Qingqing, Qiuhua Rao, Quan Zhang, Zhuo Li, Dongliang Sun, and Wei Yi. "A New Method for Predicting Double-Crack Propagation Trajectories of Brittle Rock." International Journal of Applied Mechanics 13, no. 02 (March 2021): 2150026. http://dx.doi.org/10.1142/s1758825121500265.
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Multi-crack propagation is investigated mainly by experimental measurement and little by theoretical prediction. The classical fracture criteria can better predict tensile fracture under arbitrary loading conditions (pure tensile, pure shear and mixed-mode), but have difficulty in predicting shear fracture. In this paper, Mode I and Mode II SIFs of branch-cracks initiated by the original cracks were calculated by the complex function and superposition method, and a new theory of multi-crack propagation was established based on the criterion of maximum tensile-shear SIF ratio. Theoretical results of two collinear cracks under uniaxial compression show that the cracks initiate more easily at [Formula: see text] (the crack inclination angle) than other angles. Coalescence of branch-crack only occurs at [Formula: see text] with the maximum crack propagation length. Peak stress [Formula: see text] reaches minimum when [Formula: see text] (inner friction angle of rock), and the larger the [Formula: see text], the closer to the compressive strength of rock the [Formula: see text]. Mechanism of the crack initiation and propagation are all Mode I under uniaxial compression. Uniaxial compressive test results of red sandstone (the rock material is assumed to be homogeneous) pre-cracked specimens agree well with predicted results of the crack initiation, stable and unstable propagation, which can prove the validity of the new multi-crack propagation prediction method.
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Chang, Yan Jun, Shuang Feng Zeng, Ke Shi Zhang, and Zhuo Li. "Study of Q345 Steel under Tensile Failure with Bilateral Parallelcracks." Applied Mechanics and Materials 574 (July 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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Messé, Olivier M. D. M., Joel Lachambre, Andrew King, Jean Yves Buffière, and Cathie M. F. Rae. "Investigation of Fatigue Crack Propagation in Nickel Superalloy Using Diffraction Contrast Tomography and Phase Contrast Tomography." Advanced Materials Research 891-892 (March 2014): 923–28. http://dx.doi.org/10.4028/www.scientific.net/amr.891-892.923.
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Evaluation of superalloy component life in turbine engines requires a detailed understanding of how fatigue crack initiation and short crack propagation contribute to fatigue life. However most investigations have been carried out post-mortem and in two dimensions. New techniques are able to fully resolve cracks propagating in four dimensions (space and time), enabling characterisation of their local environments and allowing a much deeper understanding of fatigue mechanics. Nickel-based superalloys experiencing high cycle fatigue have shown a high sensitivity to microstructure during initiation and short crack propagation. Using high energy X-rays and the combination of Diffraction Contrast Tomography (DCT) and Phase Contrast Tomography (PCT), we followed a fatigue crack initiated from a Focused Ion Beam (FIB) milled notch at room temperature. Analyses have been carried out to fully characterise the crack and its environment. We tracked the evolution of the crack and interactions with the microstructure. Subsequently, post-mortem investigations have been carried out to corroborate results obtained from the tomographs and to provide more local information of fatigue crack propagation.
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Tilbrook, Matthew, Lyndal Rutgers, Robert J. Moon, and Mark Hoffman. "Fracture and Fatigue Crack Propagation in Graded Composites." Materials Science Forum 492-493 (August 2005): 573–80. http://dx.doi.org/10.4028/www.scientific.net/msf.492-493.573.
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The propagation of cracks in graded materials under monotonic and cyclic loading was investigated via experiment and simulation. Graded alumina/epoxy composite specimens exhibiting a variation in composition from 5% to 65% epoxy, representing a twenty-fold variation in Young’s modulus, across a region of width between 6 and 20 mm, were produced by a multistep infiltration technique. Crack initiation and propagation under monotonic and cyclic four-point bend loading was monitored and crack trajectories and growth rates were measured. Initial crack deflection was observed, in agreement with theoretical and computational predictions in the literature. Cracks exhibited further deviation as they traversed the graded region. Higher deflection angles were observed for specimens with steeper gradients, and for those with cracks initially located closer to the compliant side of the gradient. Homogeneous specimens in the composition range 5% to 55% epoxy were also produced to investigate the composition dependence of mechanical, fracture and fatigue properties for aluminaepoxy composites. Crack propagation resistance appeared to differ between monotonic and cyclic loading, though an increase with crack extension was observed in both cases. The significant variation in measured crack-propagation resistance, for cracks in graded specimens, was accordingly interpreted as a combination of crack-extension effect and spatial variation of both intrinsic and extrinsic crack-growth resistance. A finite element model has been developed to simulate the propagation process, with particular attention paid to crack propagation and deflection criteria. Results from homogeneous specimens were utilised for estimating spatial property distribution and crack-extension effects in the graded specimens. Experimental results for crack path and crack-growth resistance profile show good agreement with modeling predictions.
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Maimaitiyusupu, Semaierjiang, Zhende Zhu, Xuhua Ren, Hui Zhang, and Shu Zhu. "Analysis of Micro-Evolution Mechanism of 3D Crack Initiation in Brittle Materials with Hole under Uniaxial Compression." Materials 17, no. 4 (February 16, 2024): 920. http://dx.doi.org/10.3390/ma17040920.
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This article investigates the microscopic mechanism of crack initiation and propagation in three-dimensional embedded cracks in brittle materials containing circular holes. First, a method for the development of transparent, brittle materials is proposed. Second, UCS tests were conducted on transparent, brittle materials containing circular holes and internally embedded three-dimensional cracks. Finally, a numerical model was established in PFC3D to analyze the crack initiation and propagation mechanism. The results show that when α = 0° (α refers to the pre-existing crack inclination), the upper tip of the pre-existing crack appears as a tensile wing crack, and the lower tip of the pre-existing crack appears as a tensile–shear mixed crack. When α = 30°, no wing crack appears, and the tensile crack on the fracture surface only appears after the hole cracks. When α = 60 and 90°, a tensile wing crack and an anti-wing tensile–shear mixed crack appear at the upper tip of the pre-existing crack. A tensile wing crack appears at the lower tip of the pre-existing crack and appears “self-limiting”. During the propagation of wing cracks to the surface of the specimen, the transition sequence of the crack propagation mechanism is tensile through failure—tension-shear mixed failure—tensile failure. It can be seen that the interaction between the crack and hole has an important influence on the evolution mechanism of the crack and the failure mode of the specimen.
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Sevcik, Martin, Pavel Hutar, Lubos Nahlik, Ralf Lach, Zdenek Knesl, and Wolfgang Grellmann. "Crack propagation in a welded polyolefin pipe." International Journal of Structural Integrity 3, no. 2 (May 25, 2012): 148–57. http://dx.doi.org/10.1108/17579861211235174.
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PurposeThe purpose of this paper is to study the effect of the material inhomogeneity on crack behavior initiated both axially and circumferentially in or near the butt weld and to discuss consequences on residual lifetime of the welded structure.Design/methodology/approachA three‐dimensional numerical model of pipe weld with smooth and continuous change of material properties has been used to study the fracture behavior of the cracked pipe structure. The stress intensity factor was considered as a parameter controlling the fracture behavior. The semi‐elliptical shape of the crack front was estimated under assumption of constant stress intensity factor along the crack front.FindingsAccording to the results obtained in the paper the following conclusions were deduced. First, the most critical location of the crack is in the middle of the inhomogeneous region (weld center) regardless of the crack orientation. The stress intensity factor is substantially higher than in the case of a crack located in the homogenous pipe. Second, with regard to crack shapes, the circumferentially oriented cracks are practically identical regardless to the crack location if compared with the axial cracks. Third, the stress intensity factors of axially‐oriented cracks are approximately twice higher than in the case of circumferential cracks. This implies that the cracks are more likely to grow in an axial direction.Originality/valueThe results described in the paper can be used for estimation of critical crack length or for estimation of the critical applied inner pressure of medium transported in the pipe and are of paramount importance for service life estimations of polymer welded pipes in actual use.
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Chekunaev, Nikolay I. "Steady-State Crack Propagation in Stressed Elastic Solid." Key Engineering Materials 462-463 (January 2011): 495–500. http://dx.doi.org/10.4028/www.scientific.net/kem.462-463.495.
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A crack, symmetrically propagating in elastic material, was considered as superposition of surface Rayleigh waves. The self-similar growth of face loaded crack was considered in detail. Exact expressions of deformation and stress fields in the crack’s surrounding were found and asymptotic behavior of stress near cracks’ tips was also obtained. A condition that determines the crack’s velocity of self-similar propagation was found.
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Changfang, Zhao, Ren Rui, Wei Yi, Yang Guang, He Bin, Zhang Kebin, and Zhong Jianlin. "Crack Propagation for Glass Fiber Reinforced Laminates Containing Flame Retardant: Based on Single-Edge Tensile Loading." Materiale Plastice 59, no. 2 (July 1, 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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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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Yu, Jia, Yi Zhuo Liu, and Rong Rong Shi. "Studies on Crack Propagation of Carbon Fiber Reinforced Epoxy Resin Composite." Advanced Materials Research 79-82 (August 2009): 1029–33. http://dx.doi.org/10.4028/www.scientific.net/amr.79-82.1029.
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Unidirectional carbon fibre reinforced resin matrix composite (CFRP) with different fibre volume fraction are stretched dynamically under static load in SEM, initiation and propagation mechanism of crack is in-situ observed, and tensile fracture of specimens is also observed. The results show that: Microscopic cracks are mainly originated from fracture of fibre, numerous fibre cracks transfixion each other in form of matrix or interface cracking, and cause failure of CFRP. Microscopic crack propagation path is related to the thickness of matrix layer between fibres. Propagation of single fibre crack at interface accord with description of microscopic crack deflection criterion for fibre reinforced composite, but the crack deflection criterion cannot descript microscopic crack propagation mechanism of unidirectional CFRP effectively, because distribution discreteness of fibre and its strength are not considered.
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Someno, Ryota, Kentaro Imai, Yuichiro Matsumoto, Souta Matsusaka, Sho Itoh, Hirofumi Hidai, Akira Chiba, and Noboru Morita. "Effects of Temperature and Relative Humidity on Crack Propagation Behavior During Wheel Scribing of Alkali-Free Glass Sheet." International Journal of Automation Technology 17, no. 5 (September 5, 2023): 521–28. http://dx.doi.org/10.20965/ijat.2023.p0521.
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The effects of the ambient temperature and relative humidity on crack propagation behavior during wheel scribing were investigated. A chamber was built to allow dynamic observation of crack propagation behavior in a controlled atmosphere. A developed miniature scriber was installed in the chamber, and the crack propagation behavior was observed from lateral and back sides during wheel scribing under various atmospheric conditions. As a result, the median crack propagation rate increased with relative humidity. We speculated that this was caused by the stress corrosion of glass. Although stress corrosion is considered to be more reactive at higher temperatures, the results of scribing at different temperatures showed that higher temperatures did not necessarily increase median crack propagation. This is due to the formation of lateral cracks before the median cracks have fully propagated. These results suggest that the interaction between multiple cracks should be considered when discussing the effects of temperature and humidity in wheel scribing.
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Yang, Xiaolin, Chang Wang, Huaibao Chu, Shaoyang Yan, Haixia Wei, and Mengfei Yu. "Study on the Stress Field and Crack Propagation of Coal Mass Induced by High-Pressure Air Blasting." Minerals 12, no. 3 (February 27, 2022): 300. http://dx.doi.org/10.3390/min12030300.
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High-pressure air blasting (HPAB) is one type of physical blasting technique that enhances the extraction rate of coalbed methane by impacting the coal mass with high-pressure gas to create cracks within it. First, based on the physical and mechanical parameters of the simulated coal rock mass, the RHT constitutive model of the coal rock mass was established, and its parameters were determined. Then, the laws of crack propagation and stress wave decay in coal induced by high-pressure air blasting were revealed by comparing the effect with that of equivalent explosive blasting. Next, the HPAB experiment was simulated to explore the coal crack propagation law under in-situ stress conditions. Finally, the HPAB experiment was carried out and the results of this experiment were compared with the numerical simulation results. The results indicate that the crack propagation induced by high-pressure air blasting is considered as two major stages, i.e., the crack initiation and crack propagation stage induced by the stress wave and the crack stable propagation stage induced by the duration high-pressure gas. In the case of equal energy, the peak stress wave of high-pressure gas is smaller, decays more slowly and has a longer action time, compared to explosive blasting. Therefore, the number of initial random cracks in coal mass induced by high-pressure air blasting is less, and the range of crack propagation induced by high-pressure air blasting is larger. When λ = 0 (λ is the ratio of the horizontal in-situ stress to the vertical in-situ stress), the in-situ stress in the coal seam can promote the propagation of vertical cracks but inhibit the propagation of horizontal cracks. When λ = 0.5 and 1, the in-situ stress inhibits the propagation of both horizontal and vertical cracks.
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Han, Jeong Woo, and Seung Ho Han. "Fatigue Crack Propagation Life of Welded Joints Related to the Statistical Characteristics of Multiple Surface Cracks." Key Engineering Materials 321-323 (October 2006): 615–19. http://dx.doi.org/10.4028/www.scientific.net/kem.321-323.615.
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Multiple collinear surface cracks distributed that are randomly along a weld toe have a strong influence on the fatigue crack propagation life of welded joints. This issue is investigated using statistical approaches based on series of systematic experiments, in which initial crack numbers, their locations and crack sizes, i.e. depth and length, are taken into account. The number of initial cracks follow a normal distribution, and the probability of initial crack depths and lengths can be accurately described by the Weibull distribution. These characteristics are used to calculate the fatigue crack propagation life, in which the mechanisms of the mutual interaction and the coalescence of multiple cracks are considered as well as the Mk-factors. The automatic calculation of fatigue crack propagation life is achieved by the application of NESUSS, where parameters such as the number, location and size of cracks are all treated as random variables. The random variables are dealt through a Monte-Carlo simulation with sampling random numbers of 2,000. The results of the simulation provide the statistical characteristics of the fatigue crack propagation life for welded joints as a function of the number of initial cracks. The sum of the simulation results and the fatigue crack initiation life referred from a previous paper is in good agreement with the experimental results.
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Zhang, Zhen Ya, Zhong Duan, and Feng Hua Zhou. "Velocity-Toughening and Crack Speed Oscillations in the Dynamic Fracture of PMMA Plates." Applied Mechanics and Materials 566 (June 2014): 298–304. http://dx.doi.org/10.4028/www.scientific.net/amm.566.298.
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To study the propagating behavior of a dynamic crack in brittle materials, an experimental technique was developed that measures the propagation speed of a fast crack in a preloaded brittle strip. The specimen is a rectangular PMMA plate clamped by two heavy steel fixtures that are attached to a MTS test machine. After the specimen was tensile loaded to a prescribed load level, a sharp crack was initiated at the middle point on one side of the specimen. Due to the brittleness of the material, the crack propagates quickly across the specimen. The propagation velocity of the crack was measured by using the equally spaced conductive lines that were painted on the specimen surface before the tests. High speed video camera was also used for monitoring the propagation behavior of the cracks. The experimental results show that for each preloaded plate, the crack arrives at a steady velocity v0 after a short acceleration stage. In the steady stage crack propagation is in self-similar state. The steady velocity of the crack was found to be an increasing function of the energy Gc stored in the preloaded strip, which means that the material has a "velocity-toughening" property. When the crack speed exceeds a threshold, the crack exhibits apparent speed oscillations. This speed oscillation corresponds to the occurrence of the periodic grooves on the fractured surface. Further increase of the preload results in the bending, micro branching, and full bifurcations of the crack paths.
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Hosseini-Toudeshky, Hossein, Bijan Mohammadi, and Pooya Saniei. "Fatigue Multi-Cracks Growths in Plates Using J-Integral Approach with a Developed Home FEM Software." Key Engineering Materials 560 (July 2013): 61–70. http://dx.doi.org/10.4028/www.scientific.net/kem.560.61.
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In this paper multiple fatigue cracks propagation are simulated in two-dimensional plates. Since re-meshing the cracked bodies in each increment of crack extension is a time-consuming and complicated procedure, numerical simulation of mixed-mode crack propagation with FEM is a difficulty. For this purpose, a FEM software is programmed and mesh refinement in each increment of crack is performed by Delaunay Refinement Algorithm. Using different refinement methods, complex boundaries such as multiple cracks and discontinuities which are closed together are easily refined by this algorithm. Crack propagation path is predicted using domain form of J-integral. Modified tensile stress (MTS) criterion is used to predict the crack propagation path in each increment. Different numerical examples illustrate the validation and reliability of present software.
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Sorbello, Fabio, Peter E. J. Flewitt, A. G. Crocker, and Gillian E. Smith. "A Consideration of Cleavage Crack Propagation in Fe2Si Steel." Key Engineering Materials 385-387 (July 2008): 1–4. http://dx.doi.org/10.4028/www.scientific.net/kem.385-387.1.
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It is well established that within the lower-shelf temperature range of Fe2-3Si polycrystalline steels, the brittle fracture occurs predominately by transgranular cleavage, unless subject to embrittling heat-treatments. The cleavage fracture develops on the well established {001} planes of the bcc structure. In this paper we revisit the growth, of these cleavage cracks by considering crack propagation in single crystals of Fe2Si steel. Three point bend specimens manufactured from oriented crystals have been tested by impact loading at a temperature of -196°C. High spatial resolution focused ion beam imaging combined with ion milling is used to examine in detail the crack propagation path and has provided a new insight into the mechanisms involved. In particular it has been established that within the process zone of the propagating cracks local strain is accommodated by the formation of {112} twins. The results are discussed with respect to the overall crack propagation mechanism.
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Guo, Hao, Guang Fu Li, Xun Cai, Jiasheng Bai, and Wu Yang. "Effect of Cyclic Loading on Crack Propagation of X-70 Pipeline Steel in Near-Neutral pH Solution." Key Engineering Materials 297-300 (November 2005): 2501–7. http://dx.doi.org/10.4028/www.scientific.net/kem.297-300.2501.
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Crack propagation of X-70 pipeline steel in near-neutral pH solution was studied under different modes of cyclic loading. A revised equation of crack growth rate vs. Δ K was obtained. Average crack growth rate increased with cycles under conditions of different R values. Linear shape notch specimen made cracks much easier to initiate and propagate than V-shaped notch specimen did. For different R values, the curves of crack growth rate with cycles were similar, but the platform propagation period and quick propagation period were different obviously. Crack growth rate at both periods increased and thus failure time decreased markedly with decrease of R value. The propagation directions of cracks were different under different cyclic loading conditions. Under mode I (single tensile stress) cyclic loading, cracks were straight and perpendicular to the tensile stress axis, while under mixed-mode I/III (tensile/shear stress) cyclic loading, cracks were sinuous and did not propagate in the direction perpendicular to the main tensile stress axis.
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Zhang, Yunbo, Yunrong Luo, Xin Wu, and Yanbing Guan. "The Review of Research on Fatigue Crack Propagation in Metallic Materials." International Journal of Materials Science and Technology Studies 1, no. 1 (March 25, 2024): 52–63. http://dx.doi.org/10.62051//ijmsts.v1n1.05.
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In recent years, with the development of industry and scientific technology, the demand for materials has been increasing. Fatigue crack propagation is an important issue in the field of materials, and developing relevant theories and methods, understanding the mechanisms of fatigue cracks, and making scientific predictions on fatigue crack propagation are hot topics both domestically and internationally. Fracture mechanics, as a discipline studying the strength and propagation of cracks in materials, has developed a relatively complete theoretical system and engineering application methods over more than 100 years of continuous development. This article focuses on the effects of factors such as temperature, stress ratio, and load frequency on the fatigue crack propagation characteristics of metallic materials, and summarizes the common theories and methods of fatigue crack propagation.
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Namazu, Takahiro, Kohei Ohtani, Keisuke Yoshiki, and Shozo Inoue. "Crack-Less Wafer-Level Packaging Using Flash Heating Technique for Micro Devices." Materials Science Forum 706-709 (January 2012): 1979–83. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.1979.
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In this article, a new technique for controlling crack position and its propagation direction in solder-bonding using Al/Ni exothermic reaction is described. Sputtered Al/Ni multilayer film is able to produce heat instantly by its self-propagating exothermic reaction, and the reactive film can be used as heat source for solder-bonding. During the reaction, however, volume reduction by approximately 12% occurs due to crystal structural change from fcc to bcc and lattice-spacing reduction. Consequently, cracks are produced in the reacted NiAl structure. The cracks negatively affect the strength of the bonded system. We have found a new technique for controlling crack position and its propagation direction. Multiple ignitions for reaction demonstrated that cracks in reacted NiAl film can be controlled. When applying the flash heating technique to wafer-level bonding, cracks are probably produced. If cracks can be fabricated on dicing cut lines by using the simultaneous multiple reactions technique, crack-less solder-bonded Si hermetic packages would be realized.
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Kotoul, Michal, Oldřich Ševeček, and Tomáš Profant. "Modelling of Crack Bifurcation in Laminar Ceramics with Large Compressive Stress." Key Engineering Materials 488-489 (September 2011): 130–33. http://dx.doi.org/10.4028/www.scientific.net/kem.488-489.130.
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Ceramic laminates designed with strong interfaces have shown crack growth resistance (R-curve) behaviour through microstructural design (e.g. grain size, layer composition) and/or due to the presence of compressive residual stresses, acting as a barrier to crack propagation. The goal of the contribution is to model the mechanism of crack bifurcation in laminar ceramics with large compressive stress which still have not been satisfactory explained. Experimental observations of the crack path in the multilayered ceramics tested under several kinds of loading showed crack penetration (i.e. crack propagating normal to the layers followed by crack bifurcation when the crack propagated from the tensile to the compressive layer. Numerical results [1] show that the initiation of crack bifurcation can be explained by the near-tip J-integral, provided that micro-cracks exist near the crack tip. We revisit the problem using the concept of Finite fracture mechanics and the matched asymptotic expansion method in order to evaluate the energy release rate criteria describing the competition of the crack bifurcation and straight crack propagation near behind the bimaterial interface.
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Wang, Zai, Shi Yi Zhang, and Qiang Shen. "Coupled Thermo-Mechanical Phase-Field Modeling to Simulate the Crack Evolution of Defective Ceramic Materials under Flame Thermal Shock." Applied Sciences 13, no. 23 (November 23, 2023): 12633. http://dx.doi.org/10.3390/app132312633.
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Crack propagation in ceramics is a highly quick, complex, and nonlinear process that occurs under thermal shock. It is challenging to directly observe the evolution process of cracks in experiments due to the high speed and unpredictability of crack propagation. Based on the phase-field fracture method, a phase-field numerical model combined with thermal and mechanical damage is established to analyze the crack propagation path, velocity, and morphology of pre-cracked ceramic plates under flame thermal shock loading. This research primarily focuses on the impact of prefabricated crack angle and length on crack propagation. According to the findings of the numerical simulation, ceramic plates with varied prefabricated crack angles are loaded via flame thermal shock, and thermal stress is caused by the rapid rise in the temperature difference between the top edge and the inside of the ceramic plate. Hence, the crack propagation rate seems to be quick at first, and then, slows down when the wing-like cracks at the crack tips spread to both ends. The crack tip on the side closer to the flame thermal loading is more likely to generate wing-shaped cracks as the length of the pre-existing crack increases. However, the crack tip on the side further away from the flame thermal loading exhibits the reverse tendency. The complex evolution process of crack initiation, propagation, and coalescence in ceramic materials brought on by flame thermal shock can be predicted by the thermo-mechanical coupled phase-field model, which is a valuable reference for designing and optimizing the thermal shock resistance and mechanical failure prediction of ceramic materials.
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Liu, Jiangwei, Changyou Liu, and Qiangling Yao. "Mechanisms of Crack Initiation and Propagation in Dense Linear Multihole Directional Hydraulic Fracturing." Shock and Vibration 2019 (December 7, 2019): 1–15. http://dx.doi.org/10.1155/2019/7953813.
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Artificially fracturing coal-rock mass serves to form break lines therein, which is related to the distribution of cracked boreholes. For this reason, we use physical experiments and numerical simulations to study the crack initiation and propagation characteristics of dense linear multihole drilling of fractured coal-rock mass. The results indicate that only in the area between the first and last boreholes can hydraulic fracturing be controlled by dense linear multihole expansion along the direction of the borehole line; in addition, no directional fracturing occurs outside the drilling section. Upon increasing parameters such as the included angle θ between the drilling arrangement line and the maximum principal stress σ1 direction, the drilling spacing D, the difference Δσ in principal stress, etc., the effect of directional fracture is gradually weakened, and the hydraulic fractures reveal three typical cracking modes: cracking along the borehole line, bidirectional cracking (along the borehole line and perpendicular to the minimum principal stress σ3), and cracking perpendicular to σ3. Five propagation modes also appear in sequence: propagating along borehole line, step-like propagation, S-shaped propagation, bidirectional propagation (along the borehole line and perpendicular to σ3), and propagation perpendicular to σ3. Based on these results, we report the typical characteristics of three-dimensional crack propagation and discuss the influence of the gradient of pore water pressure. The results show clearly that crack initiation and propagation are affected by both the geostress field and the pore water pressure. The pore water pressure will exhibit a circular-local contact-to-integral process during crack initiation and expansion. When multiple cracks approach, the superposition of pore water pressure at the tip of the two cracks increases the damage to the coal rock, which causes crack reorientation and intersection.
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Li, Zi Qiang, Jin Gui Yu, and Qiao Xin Zhang. "Effects of Temperature on Crack Propagation of Nanocrystalline Nickel: A Molecular Dynamics Approach." Advanced Materials Research 926-930 (May 2014): 98–102. http://dx.doi.org/10.4028/www.scientific.net/amr.926-930.98.
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The primary purpose of this paper is to study the effects of temperature on crack propagation of nanocrystalline nickel by Molecular Dynamics (MD) simulations. Cracks are loaded in tension mode I. Results show that dislocation emission from a crack tip in nanocrystalline nickel due to the recombination of atomic lattice, then distortion of the crack tip promote crack propagation. The studies we have performed showed that temperature takes a great influence on the crack propagation and the crack shape, and we also found that the crack blunt obviously at high temperature.
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Xu, Nan, Zhiwei Fu, Yuan Wang, and Xuehui Shen. "Study on the short fatigue crack initiation and propagation behavior of 42CrMo." Advances in Mechanical Engineering 14, no. 9 (September 2022): 168781322211199. http://dx.doi.org/10.1177/16878132221119928.
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A micro-tensile fatigue test of 42CrMo alloy steel was carried out. The result shows that the crack initiation and propagation of the material could be characterized with randomness and localization. There existed two sorts of short fatigue crack propagation behaviors for the tested material, that is, self-propagation and joint propagation with other short cracks. A short fatigue crack growth rate function was built considering the propagation characteristics. Moreover, a simulation model of short fatigue crack evolution was built. Total three samples were tested and simulated. The experimental result was in good consistent with that from simulation, both showing that the crack growth rate accelerated first and then decelerated during propagation.