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1
Ma, Lukuan, Min Li, Jinsong Pang, and Chongwei Huang. "Evaluation of Transverse Cracks for Semi-Rigid Asphalt Pavements using Deflection Basin Parameters." Transportation Research Record: Journal of the Transportation Research Board 2673, no. 2 (January 30, 2019): 358–67. http://dx.doi.org/10.1177/0361198119826075.
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To evaluate transverse cracks on a semi-rigid asphalt pavement by falling weight deflectometer (FWD), a three-dimensional (3D) dynamic finite-element (FE) model to calculate the deflections of transverse-cracked semi-rigid asphalt pavements under FWD loading was developed and validated by in-situ FWD tests. Then, the effect of crack types and crack width on the deflection basin was investigated for semi-rigid asphalt pavements under different interlayer contact conditions. The relationship between transverse cracks and deflection basin parameters (DBPs) was also analyzed. Finally, the slope ratio to evaluate transverse cracks was proposed and validated by field application. Results show that cracks on pavements will make the deflection basin steeper and the crack width slightly affects the deflections for the same type of crack without interaction between adjacent cracking surfaces. Results also indicate that deflection values increase obviously when the surface-base interaction changes from “Full bonded” to “Full slip.” In addition, results indicate that the slope index ( S1), the shape index ( F2), and the area index (AREA) correlate well with transverse cracks, and the surface cracking, “Reflective cracking 1” (surface and base cracking simultaneously), “Reflective cracking 2” (surface, base, and subbase cracking simultaneously) and the hidden cracking (base cracking, or base and subbase cracking simultaneously) can be identified by the slope ratio. Field application also indicates that the slope ratio can be applied to evaluate the types of transverse cracks on semi-rigid asphalt pavements.
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Feng, Di, Jiakun Gong, Xiaodong Ni, and Jie Ren. "Experimental and Numerical Analysis of Soil Cracking Characteristics under Evaporation." Mathematical Problems in Engineering 2021 (November 13, 2021): 1–10. http://dx.doi.org/10.1155/2021/3790345.
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There are numerous cracks on soil surface in nature. These cracks are mainly formed by the continuous water loss and shrinkage of soil under evaporation. Cracks have an important effect on the properties of soil. The analysis of soil moisture movement and cracking characteristics under evaporation is of great significance to the engineering construction in the cracked soil area. In this work, an experimental study was conducted to investigate the development of soil cracks. Crack geometrical parameters were acquired at various developmental stages. According to this, the crack evolution characteristic was described qualitatively. The law of soil water movement was analyzed through the numerical simulation of evaporation effect on cracked soil. The relationship between soil moisture content and crack width was revealed, and the dynamic prediction of crack development under evaporation was realized. The results show that the development and evaporation process of soil cracks can be divided into three distinct stages, and the longer the stable evaporation time, the greater the development of cracks.
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Lu, Yang, Ning Sheng Chen, Li Qun Lv, and Ming Feng Deng. "Quantitative Study for the Impact of Fines Content on Soil Surface Cracking." Advanced Materials Research 594-597 (November 2012): 140–47. http://dx.doi.org/10.4028/www.scientific.net/amr.594-597.140.
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Cracking development in soils is of significance for their physical and mechanical properties. The fines content in soils is one of the most important factors in cracking development, leading to it being of great importance to quantitatively study how the cracking development is influenced by the fines content. In this paper, experimental simulations on soil surface cracking were first conducted in the lab with soil from Jiangjia Valley. Digital image processing technology was then applied to investigate cracking in soil with different fines content by describing the surface cracks with crack area density Ac (ratio of all cracks’ area to total surface area of the cracked soil) and crack line density Lc (ratio of all cracks’ perimeters to total surface area of the cracked soil). The conclusions are drawn as follows: 1) Surface cracks increase with fines content going up; specifically, when the soil mass with fines content ranging from 20% to 30%, there is a significant increase in cracks; There is no crack developed in the soil with no fines, comparing to the gradual increase in soils with other fines content. 2) With the loss of water content, Ac and Lc will increase until a constant value is reached. However, small cracks will be closed and big ones will evolve into smaller ones if enough water is added. 3) Soil mass with fines content less than 20% is inclined to have small cracks when it is drying and cracks will be closed if enough water is added; on the other hand, soil mass with fines content more than 20% is inclined to have bigger cracks and they will become smaller when submerged into water. 4) After times of wetting and drying cycles, soil mass shrinks and soil dry density increases, which leads to the decrease of Dc and Lc, which suggests soil with larger dry density will probably have fewer cracks.
4
Li, Peng Fei, Jing Hui Liu, Hao Peng Huang, and Hao Du. "Application of Pre-Cracking in Semi-Rigid Base to Mitigate Reflective Cracking." Advanced Materials Research 1030-1032 (September 2014): 709–13. http://dx.doi.org/10.4028/www.scientific.net/amr.1030-1032.709.
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Because of the high strength and sound stability, the cement stabilized base has been widely used in high grade pavement in China. But shrinkage cracking are easy to occur in the cement stabilized base. Under the repeating action of traffic loads and temperature loads, this kind of cracks are easy to propagate towards the asphalt surface, being called “reflective crack”. Shrinkage cracks are not normally avertable in the cement stabilized base, in contrast with a few wide cracks of broad spacing, numerous thin cracks of narrow spacing contribute little to the severe reflection cracking. On the basis of this thinking, the pre-cracking technique as a promising approach is brought forward. Several vibratory roller passes to the cement-treated base at a short curing stage, typically 1 to 3 days after placement, to create a fine network of cracks, which avoids the wide and/or long cracks and creates the ideal crack model. Comparing to wide cracking, the degree of the stress concentration resulting from thin cracking is by far mitigated. The Finite Element Method is used to predict the ideal crack model, and then the mechanical responses of the semi-rigid pavement of single wide cracking and net hairline cracking under vehicle loading are numerically simulated, simultaneously compared and analyzed. The simulation analyses indicate that the pre-cracking technique is a very useful tool to mitigate the reflective cracks.
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Spaeth, Stephen C. "Imbibitional Stress and Transverse Cracking of Bean, Pea, and Chickpea Cotyledons." HortScience 21, no. 1 (February 1986): 110–11. http://dx.doi.org/10.21273/hortsci.21.1.110.
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Abstract Transverse cracking was examined in cotyledon tissue of snap bean (Phaseolus vulgaris L. ‘Apollo’), pea (Pisum sativum L. ‘Garfield 81’), and chickpea (Cicer arietinum L. ‘Surutato 77’). The hypothesis that imbibitional cracks develop along lines of least resistance or along preexisting cracks was evaluated. Columns of tissue were cut from cotyledons. Time from the start of imbibition to detection of the first crack was compared between whole bean cotyledons and columns. Bean columns cracked transversely with respect to the long axes of the columns. They did not crack longitudinally, even if the long axis of a column was originally perpendicular to the long axis of the cotyledon. These results do not support the hypothesis that imbibitional cracks form along preexisting cracks or along lines of weakness. Imbibitional stresses induced new cracks to form. The mean time to first crack and SE associated with its measurement were both significantly reduced in columns relative to the corresponding values for whole cotyledons (40 ± 2.6 and 100 ± 8.0 min, respectively) at an imbibition temperature of 19.3°C. Pea and chickpea cotyledon tissues also cracked transversely when they were cut into long, narrow columns.
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Petráš, Roman, Viktor Škorík, and Jaroslav Polák. "Crack Initiation in Austenitic Stainless Steel Sanicro 25 Subjected to Thermomechanical Fatigue." Solid State Phenomena 258 (December 2016): 273–76. http://dx.doi.org/10.4028/www.scientific.net/ssp.258.273.
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Thermomechanical fatigue experiments were performed with austenitic stainless Sanicro 25 steel. Several amplitudes of mechanical strain in a wide temperature interval (250-700 °C) were applied to the specimens. Mechanical response was recorded and fatigue lives were obtained. Scanning electron microscopy combined with FIB technique was used to study the mechanism of crack initiation in in-phase and in out-of-phase thermomechanical cycling. Different mechanisms of the crack initiation were found in these two types of loading. During in-phase loading fatigue cracks start in grain boundaries by cracking of the oxide. Cracks grew preferentially along grain boundaries which resulted in rapid crack initiation and low fatigue life. In out-of-phase loading multiple cracks perpendicular to the stress axis developed only after sufficiently thick oxide layer was formed and cracked in low temperature loading half-cycle. The cracks in oxide allowed localized repeated oxidation and finally also cracking. The cracks grow transgranularly and result in longer fatigue life.
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Pais, Jorge. "The Reflective Cracking in Flexible Pavements." Romanian Journal of Transport Infrastructure 2, no. 1 (July 1, 2013): 63–87. http://dx.doi.org/10.1515/rjti-2015-0012.
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Abstract Reflective cracking is a major concern for engineers facing the problem of road maintenance and rehabilitation. The problem appears due to the presence of cracks in the old pavement layers that propagate into the pavement overlay layer when traffic load passes over the cracks and due to the temperature variation. The stress concentration in the overlay just above the existing cracks is responsible for the appearance and crack propagation throughout the overlay. The analysis of the reflective cracking phenomenon is usually made by numerical modeling simulating the presence of cracks in the existing pavement and the stress concentration in the crack tip is assessed to predict either the cracking propagation rate or the expected fatigue life of the overlay. Numerical modeling to study reflective cracking is made by simulating one crack in the existing pavement and the loading is usually applied considering the shear mode of crack opening. Sometimes the simulation considers the mode I of crack opening, mainly when temperature effects are predominant.
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Zhang, Yong Shen, and Yan Ying Li. "Research on the Rigidity of Continuous Beam with Equal Span under the Temperature Load." Advanced Materials Research 255-260 (May 2011): 846–50. http://dx.doi.org/10.4028/www.scientific.net/amr.255-260.846.
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Cracks appeared in concrete structure is always concerned in construction engineering. As the cracks appear, the rigidity of structure will descend. So only the combination of slip theory and the non-slip theory could reflect the development of cracks in the course of analysis of cracks development. For axial tension and bending components, stiffness changes before and after cracking. The continuous beam with equal span is analyzed under the temperature load by the finite element method. As the cracks with different space appear, there is an abrupt bending moment with every crack. Different crack spacing, crack steep drop differently. So the wider the crack’s space is, the higher the abrupt bending moment is.
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Lee, Hosin (David), and Jungyong (Joe) Kim. "Development of a Crack Type Index." Transportation Research Record: Journal of the Transportation Research Board 1940, no. 1 (January 2005): 99–109. http://dx.doi.org/10.1177/0361198105194000112.
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Many automated systems for crack analysis have been developed to measure the extent and severity of pavement cracking objectively. However, the accuracy of such an automated crack analysis system has not been satisfactory. This paper presents a crack type index (CTI) that can be easily adopted to determine the crack type objectively as longitudinal, transverse, and alligator cracking. The CTI is based on the spatial distribution of the image tiles rather than image pixels, where a tile is defined as a subimage of a whole digital image. The spatial distribution of image tiles is analyzed vertically and horizontally, with a resulting single index, which can be used to identify a spatial orientation of cracking. To determine the accurate CTI threshold values for longitudinal, transverse, and alligator cracks, 150 pavement images were captured with a digital video camera mounted on a sport-utility vehicle: 50 images for each of three types of cracking. These 150 images were analyzed automatically to compute the CTI values that correlate with crack types. To validate the CTI system, another 150 pavement images were captured. The CTI system identified 150 images as proper crack types with an 86% accuracy for alligator cracking, 92% accuracy for transverse cracking, and 94% accuracy for longitudinal cracking. The CTI system is further validated against images of block cracking and multiple cracks. The validation result against block cracking and multiple cracks indicates that the proposed CTI system in conjunction with UCI is robust and can be extended to identify block cracking and multiple cracks. The CTI method can be used to determine crack types from the digital images automatically without any human intervention.
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Zamora, M., and J. P. Poirier. "Experimental study of acoustic anisotropy and birefringence in dry and saturated Fontainebleau sandstone." GEOPHYSICS 55, no. 11 (November 1990): 1455–65. http://dx.doi.org/10.1190/1.1442793.
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The velocities of ultrasonic P, SH, and SV waves have been measured in two perpendicular directions, in samples of Fontainebleau sandstone as received or thermally cracked, dry, or saturated, under uniaxial stress. We have investigated the effect of cracking, saturation, and uniaxial stress on the velocity of P and S waves in two orthogonal directions (anisotropy) and the velocity of S waves with two orthogonal polarizations in each direction of propagation (birefringence). The effect of cracking, saturation, and uniaxial stress on Poisson’s ratio has also been investigated. The velocity anisotropy is larger for S waves than for P waves and practically disappears in saturated samples. Birefringence is attenuated in saturated samples. Inversion of the results using Crampin’s model gives values of the crack densities in three directions, in qualitative agreement with the state of cracking observed by scanning electron microscopy. In particular, the crack density is found to be near zero in sandstones with rounded pores only. After thermally induced cracking the crack density is found to be ≈20 percent; uniaxial stress closes the cracks in the plane normal to the stress. Also, in naturally cracked samples the crack density is found to be quite high. Uniaxial stress causes the density of cracks to decrease, mostly in the plane normal to the stress.
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Ao, Bo, Ding Hua Zhang, Xin Bo Zhao, and Xia Gang Xu. "Subvoxel Level Short Crack Simulation and Visualization." Materials Science Forum 532-533 (December 2006): 556–59. http://dx.doi.org/10.4028/www.scientific.net/msf.532-533.556.
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In order to obtain the projections with short cracks, a novel subvoxel model is proposed for short crack simulation. Short cracks are modeled in subvoxel space. Giving an initial subvoxel as an initial cracking point, a short crack is simulated according to the random growing mode. If there are multiple initial cracking points, multi-cracks can be simulated easily, and short cracks are visualized using CT. Limited by the resolution of real CT system, it is not possible to detect individual short crack but a group of them. By pre-processing the reconstructed images, new images are obtained, which are very close to actual conditions. The differences between the reconstructed images without short cracks and the images with short cracks are analyzed. Experiment results proved that it is feasible to detect short crack behavior by analyzing the grey level variance of the images.
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Chen, Aijun, Chaohua Li, Shanshan Zhao, Bai Yang, and Chuanyang Ding. "Study on the Dynamic Mechanism of the Desiccation Crack Initiation and Propagation in Red Clay." Sustainability 15, no. 14 (July 18, 2023): 11156. http://dx.doi.org/10.3390/su151411156.
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Red clay is susceptible to cracking in desiccating environments, with resulting crisscrossing cracks that compromise the soil structure and increase the likelihood of geological hazards. To investigate the dynamic mechanism of the initiation and propagation of soil desiccation cracks under natural hygrothermal conditions, a desiccation test was conducted on a red clay slurry using three-dimensional digital image correlation (3D DIC) technology. The evolution behaviour of desiccation cracks was analysed, and the dynamic relationships between moisture content, displacement field, strain field, and soil desiccation cracking were explored. The test results showed that the Atterberg limits of red clay are correlated with desiccation cracking. Cracks tend to initiate in areas where tensile strain is concentrated or significant displacement differences exist. Following crack initiation, the surrounding strain and displacement fields redistribute, influencing the propagation direction, development rate, and morphology of subsequent cracks nearby. Additionally, the relative displacement and strain at the edges of cracks are related to the crack propagation direction. Earlier crack initiation usually corresponds to a larger relative displacement and strain at the crack edges, while the displacement and strain at the soil clod centre are typically smaller than those at the crack edges. DIC technology can quickly and accurately obtain dynamic information about displacement and strain fields, providing feasible technical support for analysing the dynamic mechanism behind soil desiccation cracking. It has potential value in engineering hazard prevention and sustainable development.
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Plumtree, Alan, and Steve B. Lambert. "Stress Corrosion Cracking in Pipeline Steels." Key Engineering Materials 577-578 (September 2013): 5–8. http://dx.doi.org/10.4028/www.scientific.net/kem.577-578.5.
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Clusters of fine stress corrosion cracks on the external surface of buried steel natural gas pipelines in contact with groundwater have been examined and studied. The growth rates of transgranular stress corrosion cracks have been modeled and determined by conducting laboratory tests under similar conditions to those recorded in practice. The steel samples were immersed in an anaerobic dilute, near neutral solution with an open circuit potential for various times under stress. Metallographic examination of the resulting stress corrosion cracks was then conducted. Transgranular fracture, similar to that observed in the field, was observed following tests carried out under low frequency cycling in combination with a high stress ratio (R= minimum load/maximum load). A quantitative relationship between the frequency and stress ratio was developed giving crack growth rates similar to those observed in practice. Also, a superposition model was developed and applied to the experimental data which gave very good agreement between the actual and predicted crack growth rates. Applying the superposition model to the operating natural gas pipeline data showed that realistic predictions of crack growth result when taking interaction of the cracks into account.
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Zhang, Li Wei. "Analysis and Prevention of Early Commercial Concrete Crack with Material Properties." Applied Mechanics and Materials 540 (April 2014): 209–12. http://dx.doi.org/10.4028/www.scientific.net/amm.540.209.
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Concrete in constant access to technology development, intensification of its early shrinkage cracks caused by problems in the early works become an urgent problem. Early modern concrete easily explained reason for cracking of early age cracking depth analysis of the formation mechanism. And on this basis, the proposed early modern concrete cracks crack control philosophy to early shrinkage of concrete cracking on the goods to instruct the control, service and engineering.
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Salys, Donatas, Gintaris Kaklauskas, Edgaras Timinskas, Viktor Gribniak, Darius Ulbinas, and Eugenijus Gudonis. "THE ANALYSIS OF THE DISCRETE CRACKING MODEL OF REINFORCED CONCRETE TENSILE MEMBERS." Engineering Structures and Technologies 2, no. 4 (December 31, 2010): 146–56. http://dx.doi.org/10.3846/skt.2010.19.
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Adequate modelling of reinforced concrete (RC) cracking, particularly post-cracking behaviour (tension stiffening), as one of the major sources of nonlinearity, is the most important and difficult task for deformation analysis. Deformationbehaviour of the cracked RC members is a complex process, including a wide range of effects such as differentstrength and deformation properties of steel and concrete, concrete cracking, tension-softening and tension-stiffening,bond slip between reinforcement and concrete etc. Even under low load, behaviour can be non-linear, which presents a challenge for calculating the deformations of RC members.When stress in concrete first reaches tensile strength at the weakest section,cracking occurs. After the formation of the first primary crack up to the final one, concrete contribution steadily decreases. At the final cracking point, the stable crack pattern has been reached. Increase in load will result in a further decrease of concrete contribution due to bond-slip causing cover-controlled cracks to develop between the primary cracks and a gradual breaking down of the bond. This process can be imagined as the formation of internal secondary cracks along the deformed bar due to bond stress transfer to sound concrete in between primary cracks. Total stresses in the cracked tensile reinforcement consisted of genuine stresses corresponding to the average strain of steel and additional stresses due to tension-stiffening. The internal forces that represent the latter stresses are called the residual and can be used for assessing the average bond behavior of RC members. This paper investigates tension-stiffening effect in RC members. The discrete cracking model of RC member is described in the paper. The discussed approach is based on bond-slip relationship that models the bond-action between concrete and reinforcement. This approach is realistically capable of modelling cracking and determining crack widths and deformations. However, the accuracy of calculation results depends on the assumed bond stress-slip relationship. A number of recent investigations aimed at developing and modifying such models were performed intending that discrete cracking modelling technique could become a powerful tool for the analysis of reinforced concrete members. The present study is dedicated to deformation analysis of reinforced members that are subjected to pure tension and is based on the results of the experimental program reported in literature. The average deformations of such members were calculated applying the discrete cracking method using different bond stress-slip relationships and compared with test results reported in literature. It was concluded that relationship recommended by CEB-FIP MC90 was unacceptable for the analysis performed.
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Kuo, C. H., L. M. Keer, and M. P. Bujold. "Effects of Multiple Cracking on Crack Growth and Coalescence in Contact Fatigue." Journal of Tribology 119, no. 3 (July 1, 1997): 385–90. http://dx.doi.org/10.1115/1.2833499.
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A three-dimensional fracture analysis is applied to investigate the interaction effects of multiple cracking on the crack growth in contact fatigue and to simulate the process of crack coalescence that leads to pitting failure. The rolling contact fatigue is simulated by a cyclic Hertzian contact loading moving across the surface of an elastic half-space containing several planar cracks. The body force method is applied to determine the three modes of stress intensity factors around the three-dimensional crack fronts. The fatigue crack propagation under contact loading is estimated based on the modified Paris law for mixed mode crack growth. For coplanar cracks, the growth rate increases significantly as the adjacent cracks are very close while parallel cracks appear to constrain the cracks from coalescing. A numerical simulation for the propagation of crack fronts versus contact cycles is shown to agree with the pitting cracks observed in gears.
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Ju, Yizhong, and Xu Wu. "Acoustic Emission Characteristics and Failure Prediction of the Granite with Orthogonal Cracks under Compressive Loading." Advances in Civil Engineering 2020 (October 20, 2020): 1–10. http://dx.doi.org/10.1155/2020/8846290.
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Natural joints existing in rock significantly affect the stability of long-term served subsurface engineering. In this paper, granite specimens with two orthogonal cracks were made for uniaxial compressive tests. The acoustic emission monitoring (AE) and digital image correlation techniques were employed to record the acoustic events and cracking of rock. The stress, ring-down count, and cumulative ring-down count of AE during the tests were obtained. The b-value of AE was calculated based on the magnitude and number of AE events. The relationship between the b-value and rock cracking for the specimens with orthogonal cracks was discussed. Further, the effects of orthogonal cracks distribution on the b-value and rock cracking were investigated. Experimental results show that the specimens with orthogonal cracks would undergo multiple cycles of energy accumulation-release-reaccumulation-rerelease under the uniaxial compression. For the specimens with orthogonal cracks, the b-value of AE was volatile but generally decreased until complete failure. Every cracking event during the loading made the b-value drop and then the reaccumulation of energy made the b-value increase or stable. The specimen with orthogonal cracks was more prone to initial cracking than the intact rock. The orientation of cracks had effects on the b-value evolution and crack patterns. The b-value reaching about 1.5 can be used as the failure precursor of specimens with orthogonal cracks.
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Morris, Peter H., J. Graham, and David J. Williams. "Cracking in drying soils." Canadian Geotechnical Journal 29, no. 2 (April 1, 1992): 263–77. http://dx.doi.org/10.1139/t92-030.
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Cracking in soils that are undergoing drying is controlled by soil suctions and by soil properties such as compression modulus, Poisson's ratio, shear strength, tensile strength, and specific surface energy. The paper reviews the occurrence and morphology of cracks in dry-climate regions of Australia and Canada. After reviewing the behaviour of unsaturated soils and the mechanics of cracking, solutions are developed based on (i) elasticity theory, (ii) the transition between tensile and shear failure, and (iii) linear elastic fracture mechanics. The solutions are compared and related to crack depths observed in the field. Key words : clay, cracks, crust, shear strength, soil suction, tensile strength, unsaturated soil, weathering.
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Liu, Jiawei, Yingzhi Xia, Hui Li, Guoping Hu, and Mingming Hu. "Evaporative Cracking Characteristics of the Embankment Soil Affected by the Saline Concentration." Advances in Civil Engineering 2022 (January 11, 2022): 1–9. http://dx.doi.org/10.1155/2022/2269654.
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Embankment soil affected by saline can not only cause roadbed settlement, frosting, and road cracks but also cause corrosion and cracking of roadbed pipelines, which seriously affects the stability of the road. Water evaporation and dry cracking of the saline soil mainly cause soil swelling, poor water stability, and corrosive characteristics of the embankment soil. In this study, the evaporative cracking characteristics of soil with different saline concentrations were investigated. The results showed that the moisture content decreased linearly with the drying time in the early evaporation process, subsequently decreased slow down in the mid-term evaporation, and finally become got and remain a residual moisture content, which are 46.39%, 44.05%, 42.70%, and 40.27% with the increase of the saline concentration. The evaporation process with different saline concentrations in the soil can be divided into three stages: uniform evaporation stage, slow down evaporation stage, and equilibrium evaporation stage, which was consistent with the moisture content change. With the development of the drying time, the cracks gradually appeared on the soil surface, gradually deepened in the soil, and expanded the crack network. The development of cracks can be divided into three stages: the cracking preparation stage, the crack development stage, and the crack stable stage. The cracking began at high evaporation rate under high saline concentration, and the fractal dimension remained stable under similar saline concentration. The fractal dimension was gradually increased with the decrease of the moisture content and the increase of the saline concentration, respectively. The soil began to crack with larger moisture under high saline concentration. The drying cracks in the nature were consistent with the configuration of the cracks formed in the experimental results.
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Ji, Haodong, Haoyu Jiang, Ruoyi Zhao, Ye Tian, Xianyu Jin, Nanguo Jin, and Jing Tong. "Fractal Characteristics of Corrosion-Induced Cracks in Reinforced Concrete." Materials 13, no. 17 (August 22, 2020): 3715. http://dx.doi.org/10.3390/ma13173715.
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Based on the fractal geometry, a quantitative index describing the development degree of the internal corrosion expansion of reinforced concrete was proposed. This approach could describe the similarity and complexity of the development of corrosion-induced cracks in concrete simultaneously. Based on this approach, the influence of cracking pattern and coarse aggregate distribution on crack distribution was investigated. This study obtained the crack distribution of reinforced concrete by using the half-soaking galvanic accelerated corrosion method. The results showed that the cracking pattern was the main factor affecting the complexity of crack distribution. For cracks with the simplest cracking pattern, the presence of coarse aggregate and its surface irregularity greatly affected their development trend.
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Zhang, Wei, Beibing Dai, Zhen Liu, and Cuiying Zhou. "Numerical algorithm of reinforced concrete lining cracking process for pressure tunnels." Engineering Computations 35, no. 1 (March 5, 2018): 91–107. http://dx.doi.org/10.1108/ec-11-2016-0394.
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Purpose The cracking of a reinforced concrete lining has a significant influence on the safety and leakage of pressure tunnels. This study aims to develop, validate and apply a numerical algorithm to simulate the lining cracking process during the water-filling period of pressure tunnels. Design/methodology/approach Cracks are preset in all lining elements, and the Mohr−Coulomb criterion with a tension cutoff is used in determining whether a preset crack becomes a real crack. The effects of several important factors such as the water pressure on crack surfaces (WPCS) and the heterogeneity of the lining tensile strength are also considered simultaneously. Findings The crack number and width increase gradually with the increase in internal water pressure. However, when the pressure reaches a threshold value, the increase in crack width becomes ambiguous. After the lining cracks, the lining displacement distribution is discontinuous and steel bar stress is not uniform. The measured stress of the steel bar is greatly determined by the position of the stress gauge. The WPCS has a significant influence on the lining cracking mechanism and should not be neglected. Originality/value A reliable algorithm for simulating the lining cracking process is presented by which the crack number and width can be determined directly. The numerical results provide an insight into the development law of lining cracks and show that the WPCS significantly affects the cracking mechanism.
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Ajayi, Oluwatoyin, Oladipo Dare-Abel, Lanre Ogunbowale, and Obianuju Chukwuka. "Evaluation and repair of cracks in post occupancy situations." Caleb International Journal of Development Studies 3, no. 2 (November 30, 2020): 194–207. http://dx.doi.org/10.26772/cijds-2020-03-02-011.
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Cracks in concrete have many causes. They may affect appearance only, or may indicate significant structural distress or a lack of durability. Cracks may represent the total extent of the damage, or may point to problems of greater magnitude. Their significance depends on the type of structure and nature of the cracking. This is a review paper that proposes guidelines for crack evaluation and repair of concrete structures. The causes of cracks in concrete are examined along with the principal procedures used for crack control considering both plastic and hardened concrete. The paper presents the importance of design, detailing, construction procedures, concrete proportioning, and material properties. Relevant techniques and methodology for crack evaluation were identified and the need to determine the causes of cracks as a necessary prerequisite to repair is emphasized. The selection of successful repair techniques should consider the causes of cracking, while identifying active or dormant status, and the need for repair. Keywords: Cracks, Prevention, Remedies, Structure, Types of Cracks.
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Dhakal, Nirmal, Mohammad Bashar, and Mostafa Elseifi. "Guidelines for Identification of Top-down Cracks (TDC) in In-Service Flexible Pavements." MATEC Web of Conferences 271 (2019): 08004. http://dx.doi.org/10.1051/matecconf/201927108004.
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The objective of this study was to establish guidelines to identify top-down cracking (TDC) in flexible pavements using digital image analysis and the characteristics of these cracks. Past studies indicated that the time after construction of the pavement and location of the cracks are key parameters to identify top-down cracking. The cracks were reported to appear on the wheel path or at the outer edge of the wheel path typically within 3 to 8 years of construction. In-service pavement sections were selected for analysis based on the parameters identified from the literature and computer-vision techniques were employed to investigate the geometric characteristics of these cracks. Based on the results of the analysis, the average crack width was observed to be 3 to 7 mm. With respect to the orientation of the crack, the cracks segments were mostly longitudinal with typical deviation of 20 degrees. The orientation and intensity characteristics of top-down cracks were found as useful features in crack identification.
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Kim, Cheol Woong, Dong Joon Oh, Ki Weon Kang, and Young Ho Ko. "Evaluation of Un-Cracking Delamination by Pseudo Crack Model (PCM) in FRMLs." Key Engineering Materials 345-346 (August 2007): 689–92. http://dx.doi.org/10.4028/www.scientific.net/kem.345-346.689.
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If Fiber Reinforced Metal Laminates (FRMLs) were delaminated, the decrease of stiffness and fiber bridging effect would result in the sudden aggravation of fatigue characteristics. It was reported that the delamination of FRMLs resulted from the crack of Al alloy layers and that it depended on the crack growth. When FRMLs with circular holes was un-cracked but was delaminated, it was impossible to analyze them by conventional fracture parameters expressed as the function of cracks. Therefore, a new analytical model called Pseudo Crack Model (PCM) was suggested to compare the delaminations whether cracks were made or not. The relationship between the crack consumption rate (Ccrack) and the delamination consumption rate (Cdel) was discussed and it was also known that the effect of the Ccrack was larger than that of the Cdel.
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S.Y., Wee, R. A. @. R. B. Chan, and Teo H.W. "Potential Modeling Of Pavement Deterioration Rate Due To Cracking." Journal of Civil Engineering, Science and Technology 1, no. 1 (August 1, 2009): 1–6. http://dx.doi.org/10.33736/jcest.62.2009.
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Bitumen pavements tend to crack at some point of their life under the combined action of traffic and the environment. These cracks are defects in the pavement surfacing which weakens the pavement and allows water to penetrate and cause further weakening. Once initiated, cracking usually increases in extent, severity and intensity, leading eventually to pavement failure. Cracking has therefore been an important indicator for road pavement maintenance. In view of the extensive road network in Malaysia covering more than 80,000 kilometers in total, the government has to spend huge sums of money on the repair of cracks under its annual road maintenance program. However, the resurfacing works have not always been successful and cracks tend to reappear after some time. The accurate prediction of crack occurrence and the effectiveness of resurfacing works to control cracks are key factors in predicting the timing and costs of road maintenance. In view of this, it is imperative that a suitable model for the prediction of crack development be derived. This model will then be able to predict the deterioration rate of pavement cracking in the future. It in turn will enable effective road rehabilitation programs be implemented in time before cracking deteriorates and leads to eventual pavement failure.
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Zhang, Guo Jun, Yong Bin Jia, and Xi Lin Lu. "Cracking Simulative Analysis of Reinforced Concrete Columns with ANSYS Software." Applied Mechanics and Materials 578-579 (July 2014): 946–49. http://dx.doi.org/10.4028/www.scientific.net/amm.578-579.946.
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The principle and processof finite element model of ANSYS software for RC frame column was introduced firstly,and then the cracking and development rules of RC columns under monotonic load were analyzed with ANSYSsoftware. The results show that: with the stirrup ratios increasing, the short columnwith rectangle hoop, rectangle cross brace hoop and tic tac toe stirrups appearsuccessively few inclined cracks and more vertical cracks; with the axialcompression ratio increasing, more length of horizontal cracks extend to naturalaxis, more vertical cracks appear and appeared cracks are higher along thecolumn height direction for middle length HSC frame columns; the length of OSCframe columns is not so long than that of HSC frame columns, and the crack distributionis dense and crack forms mesh, which show better ductility.
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Behnamghader, Aliasghar, Reyhaneh Neghabat Shirazi, Alain Iost, and Denis Najjar. "Surface Cracking and Degradation of Dense Hydroxyapatite through Vickers Microindentation Testing." Applied Mechanics and Materials 66-68 (July 2011): 614–19. http://dx.doi.org/10.4028/www.scientific.net/amm.66-68.614.
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Surface degradation and cracking of dense hydroxyapatite were evaluated through Vickers micro indentation using indentation loads ranged from 25 gf to 2000 gf. Crack lengths, imprint diameters and the number of lateral cracks and chips were measured using SEM. The crack length-indentation load data were analyzed with regard to the specific relations of Palmqvist and fully developed radial cracks. Crack type transition load from Palmqvist to median crack was experimentally assessed through serial sectioning technique. The analytical estimated transition load, based on the theoretical relation of the indentation load and crack lengths showed a good agreement with one obtained from experimental itinerary. Palmqvist and median cracks were identified in low and medium indentation loads, respectively. High indentation load could also lead to the formation of lateral cracks and chips. The tendency for lateral cracking was evaluated taking into account the number of lateral cracks and chips. The chips were found to be appeared just after test in higher indentation load, whereas in medium loads they could be detectable only after several weeks.
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Ma, FJ, and AKH Kwan. "Finite element analysis of concrete shrinkage cracks." Advances in Structural Engineering 21, no. 10 (December 7, 2017): 1454–68. http://dx.doi.org/10.1177/1369433217746346.
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Shrinkage cracking of concrete has been causing serviceability and durability problems and therefore needs to be carefully analyzed. However, the existing methods of shrinkage crack analysis tend to be rather empirical and often do not agree with each other. For accurate prediction of shrinkage cracks in reinforced concrete structures, a finite element method should be more suitable. Herein, a newly developed finite element method, incorporating a crack queuing algorithm of allowing only one concrete element to crack at a time so as to cater for immediate tension relief upon cracking and enable formation of discrete cracks, is extended for application to shrinkage crack analysis. It is applied to analyze the shrinkage cracks of concrete specimens reported in the literature to assess its applicability and accuracy. Overall, the finite element analysis, which also allowed for the creep effect, produced discrete crack patterns and analytical crack widths in good agreement with the observed cracks patterns and the measured crack widths.
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Peng, Zhang. "The Cracking Mechanism and Anti-Cracking Measures for Hydraulic Mass Concrete." Advanced Materials Research 1025-1026 (September 2014): 68–73. http://dx.doi.org/10.4028/www.scientific.net/amr.1025-1026.68.
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The article describes and analyzes the process of mass concrete casting and crack problems during the period of construction. The article illustrates the necessity of crack control for mass concrete structures and introduces the present application situation of commercial software used to analyse the temperature field and stress field. Combining the engineering practice, the article sums up the measures to deal with hydraulic mass concrete structure cracks and the application situation of various methods. Then the article puts forward the future research direction to solve the problem of hydraulic mass concrete crack.
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Tohgo, Keiichiro, and Nobuhiro Ogai. "Monte Carlo Simulation of Stress Corrosion Cracking in Structural Metal Materials." Key Engineering Materials 306-308 (March 2006): 447–52. http://dx.doi.org/10.4028/www.scientific.net/kem.306-308.447.
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According to laboratory accelerated test data, stress corrosion cracking (SCC) in structural metal materials occurs by initiation and coalescence of micro cracks, subcritical crack growth, multiple large crack formation and final failure under the combination of materials, stress and corrosive environment. In this paper, a computer simulation model for the process of SCC has been proposed. The procedure is as follows: The possible number of crack initiations is set for a given space and the initiation times for all cracks are assigned by random numbers based on exponential distribution. The sites and length of the cracks are assigned by uniform random numbers and normal random numbers, respectively. The coalescence of cracks and the subcritical crack growth are determined based on the fracture mechanics. The simulation is terminated when the maximum crack length reaches a critical value or all of the possible number of cracks is initiated. The results obtained in this paper indicate the applicability of the present model to predict the SCC behavior in real structures based on the laboratory accelerated test data.
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Wahlmann, Benjamin, Dominik Leidel, Matthias Markl, and Carolin Körner. "Numerical Alloy Development for Additive Manufacturing towards Reduced Cracking Susceptibility." Crystals 11, no. 8 (July 31, 2021): 902. http://dx.doi.org/10.3390/cryst11080902.
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In this work, we investigated the viability of established hot cracking models for numerically based development of crack-resistant nickel-base superalloys with a high γ′ volume fraction for additive manufacturing. Four cracking models were implemented, and one alloy designed for reduced cracking susceptibility was deduced based on each cracking criterion. The criteria were modeled using CALPHAD-based Scheil calculations. The alloys were designed using a previously developed multi-criteria optimization tool. The commercial superalloy Mar-M247 was chosen as the reference material. The alloys were fabricated by arc melting, then remelted with laser and electron beam, and the cracking was assessed. After electron beam melting, solidification cracks were more prevalent than cold cracks, and vice versa. The alloys exhibited vastly different crack densities ranging from 0 to nearly 12 mm−1. DSC measurements showed good qualitative agreement with the calculated transition temperatures. It was found that the cracking mechanisms differed strongly depending on the process temperature. A correlation analysis of the measured crack densities and the modeled cracking susceptibilities showed no clear positive correlation for any crack model, indicating that none of these models alone is sufficient to describe the cracking behavior of the alloys. One experimental alloy showed an improved cracking resistance during electron beam melting, suggesting that further development of the optimization-based alloy design approach could lead to the discovery of new crack-resistant superalloys.
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Zhang, Yuan, and Yang Sheng Zhao. "Thermal Cracking Meso-Characteristic of LuHui Granite." Applied Mechanics and Materials 34-35 (October 2010): 355–59. http://dx.doi.org/10.4028/www.scientific.net/amm.34-35.355.
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Rock macro mechanic character is decided by rock composite and meso configuration. LuHui granite minerals composite, micro configuration and the rock thermal cracking in differ temperature are observed by micro-photometer in meso. LuHui granite is composited by kinds of minerals, and its minerals’ inhomogeneity is visible, the change of cementation among rock crystal grains, dislocation and micro cracking in crystal is produced in crystal grains under temperature. By means of experiment, the development of granite micro cracks and interior configuration, and change laws of micro cracks were observed. The quantitative analysis of the micro mechanism and laws of granite thermal crack was made, granite cracks number increases acutely in 240-260 degree C after a narrow range fluctuation in 80 degree C. Finally, the thermal cracks threshold of granite was determined primarily.
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Chotkan, Shaniel, Raymond van der Meij, Wouter Jan Klerk, Phil J. Vardon, and Juan Pablo Aguilar-López. "A Data-Driven Method for Identifying Drought-Induced Crack-Prone Levees Based on Decision Trees." Sustainability 14, no. 11 (June 2, 2022): 6820. http://dx.doi.org/10.3390/su14116820.
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In this paper, we aim to identify factors affecting susceptibility to drought-induced cracking in levees and use them to build a machine learning model that can identify crack-prone levees on a regional scale. By considering the key relationship between the size of cracks and the moisture content, we observed that low moisture contents act as an important driver in the cracking mechanism. In addition, factors which control the deformation at low moisture content were seen to be important. Factors that affect susceptibility to cracking were proposed. These factors are precipitation, evapotranspiration, soil subsidence, grass color, soil type, peat layer thickness, soil stiffness and levee orientation. Statistics show that the cumulative precipitation deficit is best associated with the occurrence of the cracks (cracks are characterized by higher precipitation deficits). Model tree classification algorithms were used to predict whether a given input of the factors can lead to cracking. The performance of a model predicting long cracks was evaluated with a Matthews correlation coefficient (MCC) of 0.31, while a model predicting cracks in general was evaluated with an MCC of 0.51. Evaluation of the model trees indicated that the peat thickness, the soil stiffness and the orientation of the levee can be used to determine crack-proneness of the levees. To maintain validity and usefulness of the data-driven models, it is important that asset managers of levees also register locations on which no cracks are observed.
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Raza, Hurtig, Asala, Andersson, Svensson, and Ojo. "Influence of Heat Treatments on Heat Affected Zone Cracking of Gas Tungsten Arc Welded Additive Manufactured Alloy 718." Metals 9, no. 8 (August 10, 2019): 881. http://dx.doi.org/10.3390/met9080881.
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The weldability of additive manufactured Alloy 718 was investigated in various heat-treated conditions. The microstructure of the base metal was examined in detail in order to understand the effect of different pre-weld heat treatments; i.e., solution, solution and aging, and hot isostatic pressing. After welding, the variation in total crack lengths, maximum crack length and the total number of cracks in the heat affected zone (HAZ) were used as criteria for the cracking susceptibility of each material condition where wrought Alloy 718 was used as the reference material. Selective laser melting (SLM) manufactured Alloy 718 was susceptible to HAZ cracking in all material conditions. Total crack lengths in HAZ were highest in the SLM as-built condition and lowest in the SLM hot isostatic pressed condition. The cracks that were found in the HAZ of the welded materials consisted of liquation cracks, with eutectic product surrounding the cracks, as well as cracks from which liquation products were absent.
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Bogas, Jose Alexandre, Hawreen Hasan Ahmed, and Tomás Diniz. "Influence of Cracking on the Durability of Reinforced Concrete with Carbon Nanotubes." Applied Sciences 11, no. 4 (February 12, 2021): 1672. http://dx.doi.org/10.3390/app11041672.
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This study focuses on the influence of natural and artificially induced cracks on the durability of concrete reinforced with carbon nanotubes (CNT). Pre-cracked concrete mixes, unreinforced or reinforced with 0.1% CNT, are characterized in terms of capillary absorption, carbonation, and chloride penetration resistance, and compared to the uncracked reference concrete. The mechanical strength and durability properties were improved in uncracked CNT-reinforced concrete, without significantly affecting its density and workability. The efficiency of CNT was higher when the concrete was previously subjected to drying conditions. For all tested properties, the incorporation of CNT was effective in reducing the influence of artificial and natural cracks on concrete durability. The main contribution of CNT occurred in the crack surrounding region. Depending on the analyzed property and cracking conditions, the significant reduction of durability in cracked concrete may be 10–30% attenuated when CNT is incorporated. The effect was more pronounced in mechanically induced natural cracks, where CNT may better participate in their vicinity.
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Izzo, Michael Z., and Marta Miletić. "Desiccation Cracking Behavior of Sustainable and Environmentally Friendly Reinforced Cohesive Soils." Polymers 14, no. 7 (March 24, 2022): 1318. http://dx.doi.org/10.3390/polym14071318.
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Desiccation cracking of cohesive soils is the development of cracks on the soil surface as a result of a reduction in water content. The formation of desiccation cracks on the cohesive soil surface has an undesirable impact on the mechanical, hydrological, and physicochemical soil properties. Therefore, the main aim of this study is to experimentally and numerically investigate eco-friendly soil improvement additives and their effect on the desiccation cracking behavior of soils. Improvement of soil crack resistance was experimentally studied by conducting desiccation cracking tests on kaolin clay. Biopolymer xanthan gum and recycled carpet fibers were studied as potential sustainable soil improvement additives. In addition, image processing was conducted to describe the effect of an additive on the geometrical characteristics of crack patterns. The results show that the soil improvement additives generally enhanced the soil strength and reduced cracking. Furthermore, a hydro-mechanical model was developed to predict the moisture transfer and onset of desiccation cracks in plain and amended kaolin clays. Data obtained show that the inception of the desiccation cracking and radial displacements were delayed in the improved soil specimens, which is in agreement with the experimental data.
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Layang, Samuel. "CRACKS IN REINFORCED CONCRETE BEAM." BALANGA: Jurnal Pendidikan Teknologi dan Kejuruan 10, no. 1 (June 30, 2022): 6–12. http://dx.doi.org/10.37304/balanga.v10i1.3277.
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Cracks in concrete cannot be prevented but the size of the cracks can be controlled. Cracks that occur in concrete are strongly influenced by the nature and characteristics of the concrete constituent materials, especially cement and water. Cracks can occur in the fresh and hard concrete phases. Cracks that occur in concrete can be grouped into two, non-structural cracks and structural cracks. There are several types of non-structural cracks such as crazing, map cracking, plastic cracking due to shrinkage, plastic cracking due to settlement, cracking due to drying shrinkage, cracking due to temperature changes, cracking due to chemical reactions. Structural cracks can be caused by the effects of vibration, earthquake and loads that work beyond capacity. Cracks in concrete beams can be in the form of flexural cracks, web shear cracks, flexure-shear cracks, torsion cracks, bond cracks. The failure that occurs in the beam has a close relationship with the pattern of cracks formed. Cracks that occur in the beam must be repaired so that the damage does not get worse and efforts to strengthen the structure to ensure it remains safe
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Lewis, N., D. J. Perry, and M. L. Bunch. "AEM analysis of stress corrosion cracks." Proceedings, annual meeting, Electron Microscopy Society of America 53 (August 13, 1995): 550–51. http://dx.doi.org/10.1017/s0424820100139123.
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Cross-sectional analytical electron microscopy (AEM) was used to study stress corrosion cracking (SCC) cracks in pressurized water in an attempt to understand the mechanism of cracking. AEM is particularly well suited to study the crack tip, the crack sides and the corrosion product inside the crack. These analyses provide clues about the stress (i.e., plasticity), the environment (corrosion product) and material (precipitates/grain boundary composition) which are the key factors controlling SCC. In mis investigation SCC cracks were filled with epoxy, dimpled and ion-milled in argon until electron transparent. A cross-section of an SCC crack in Alloy 600 generated in deaerated water is shown in Figure 1. The crack is intergranular and generally propagates down grain boundaries without carbides as shown in Figure 1. The crack seen in Figure 2 is an exception and propagated down a grain boundary containing Cr7C3 carbides. Although dislocations are clearly observed in bom figures, no deformation is observed uniquely associated with the cracks and no voids have been observed ahead of the cracks.
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Zhang, Qinghua, and Ziming Xiong. "Crack Detection of Reinforced Concrete Structures Based on BOFDA and FBG Sensors." Shock and Vibration 2018 (September 3, 2018): 1–10. http://dx.doi.org/10.1155/2018/6563537.
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Reinforced concrete structural elements, as an important component of buildings and structures, require inspection for the purposes of crack detection which is an important part of structural health monitoring. Now existing crack detection methods usually use a single technology and can only detect internal or external cracks. In this paper, the authors propose a new sensing system combining BOFDA (Brillouin optical frequency-domain analysis) and FBG (fiber Bragg grating) technology, which are used to detect internal and surface cracks and their development in reinforced concrete structures, and an attempt is made to estimate the width of surface cracks. In these experiments, a special reinforced concrete beam structure was designed by the author for crack detection under load. Four continuous distributed optical fibers are fixed on the steel skeleton, which is located within the reinforced concrete beam. Three FBG sensors are fixed on the lower surface of the beam, near its centre. By analysing the sensor data, it can be found that the BOFDA-distributed fiber can be used to detect internal cracking before surface cracking, and the difference between scans can be used to judge the time of onset of internal cracking, but the relative error in position is about 5%, while the FBG sensor can detect the cracking time of microcracks on the lower surface in near-real-time and can be used to calculate the crack width. Through the experiment, it is found that if the combination of BOFDA and FBG technology is adopted, we can initially use the strain data obtained by multiple groups of BOFDA monitoring to predict the general location of the internal cracks, then to monitor the exact location of the surface cracks by FBG in the medium term, and to estimate the width of the final expansion of the cracks finally.
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Kamei, Khangamlung, and Muhammad A. Khan. "Investigating the Structural Dynamics and Crack Propagation Behavior under Uniform and Non-Uniform Temperature Conditions." Materials 14, no. 22 (November 21, 2021): 7071. http://dx.doi.org/10.3390/ma14227071.
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The robustness and stability of the system depend on structural integrity. This stability is, however, compromised by aging, wear and tear, overloads, and environmental factors. A study of vibration and fatigue cracking for structural health monitoring is one of the core research areas in recent times. In this paper, the structural dynamics and fatigue crack propagation behavior when subjected to thermal and mechanical loads were studied. It investigates the modal parameters of uncracked and various cracked specimens under uniform and non-uniform temperature conditions. The analytical model was validated by experimental and numerical approaches. The analysis was evaluated by considering different heating rates to attain the required temperatures. The heating rates were controlled by a proportional-integral-derivative (PID) temperature controller. It showed that a slow heating rate required an ample amount of time but more accurate results than quick heating. This suggested that the heating rate can cause variation in the structural response, especially at elevated temperatures. A small variation in modal parameters was also observed when the applied uniform temperatures were changed to non-uniform temperatures. This study substantiates the fatigue crack propagation behavior of pre-seeded cracks. The results show that propagated cracking depends on applied temperatures and associated mass. The appearance of double crack fronts and multiple cracks were observed. The appearance of multiple cracks seems to be due to the selection of the pre-seeded crack shape. Hence, the real cracks and pre-seeded cracks are distinct and need careful consideration in fatigue crack propagation analysis.
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Chen, Song Zhou. "The Application of Fracture Mechanics in Highway Tunnel Lining Cracking." Applied Mechanics and Materials 580-583 (July 2014): 1377–81. http://dx.doi.org/10.4028/www.scientific.net/amm.580-583.1377.
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Lining cracks of highway tunnel has a very important effect on the healthy operation of the tunnel. Establishing the model for concrete fracture mechanics evaluation, we could identify the tunnel lining cracking situation. By using Linear elastic fracture mechanics method we could calculate the stress field of crack in the lining. Separately by different depth we have calculated crack stress intensity factor. We get that growing rates of variation of stress intensity factor as the crack depths increase. So lining tunnel health operations severely cracked.
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Tang, Chao-Sheng, Bin Shi, Yu-Jun Cui, Chun Liu, and Kai Gu. "Desiccation cracking behavior of polypropylene fiber–reinforced clayey soil." Canadian Geotechnical Journal 49, no. 9 (September 2012): 1088–101. http://dx.doi.org/10.1139/t2012-067.
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Improvement of the crack resistance of clayey soils by fiber reinforcement was investigated using initially saturated and fiber-reinforced soil specimens subjected to desiccation. An image-processing technique was used to quantitatively describe the effect of fiber addition on the geometrical and morphological characteristics of crack patterns. The results show that the soil desiccation cracking behavior was significantly influenced by fiber inclusion: the crack resistance was significantly improved and the amount of desiccation cracks was significantly reduced by fiber addition. Generally, the surface crack ratio (surface of cracks to total surface), number of clods, average length and width of cracks, and crack network connectivity decreased with increasing fiber content, while the average area of clods, number of nodes per unit area, number of crack segments per unit area, crack density, and specimen integrity increased. During crack propagation, the surface crack ratio increased with decreasing water content and finally reached stabilization. Comparison between the surface crack ratio of the natural soil specimen and that of the fiber-reinforced soil specimen showed that the former was always higher than the latter. The fiber length was found to have an insignificant effect on the soil desiccation cracking behavior.
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Yuan, Junhong, Jingbo Cui, Jianmei Chang, Guanhong Zhang, and Mingxi Liu. "Effect of Alkali Pollutant in Influencing Crack Propagation in Soils." Advances in Civil Engineering 2021 (March 11, 2021): 1–8. http://dx.doi.org/10.1155/2021/6690938.
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Shrinkage, deformation, and cracking will occur under extreme climate conditions such as drought, due to the accumulation of salt inside the soil during the evaporation of water on the surface of the soil. In this study, the image processing method was used to quantitatively analyze the dehydration cracking process of clay polluted by alkaline pollutant sodium carbonate on the basis of experiments. The mechanism of the effect of sodium carbonate concentration on the shrinkage cracks of clay was discussed through the analysis and comparison of different concentrations of sodium carbonate samples. The results showed that the water loss and shrinkage cracks of alkaline contaminant clay were developed in different stages. Firstly, first-level cracks developed diagonally or parallel to the edge of the container, and then second-level cracks developed along the main cracks with an angle of close to 90°. Most of the third-level or higher-level cracks were approximately perpendicular to the second-level cracks or the edge of the container and developed in parallel. In the cracking stage, the water loss ratio of the sample had a good positive correlation with the surface crack ratio. The slope of the fitted curve increased with the increase of the sodium carbonate concentration. With the increase of sodium carbonate concentration, the water loss ratio and the width of first-level cracks of clayey soil decreased, and the total length and the number of cracks increased, while the surface cracking ratio increased first and then decreased.
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Cong, Shen, Bin Wang, Enpeng Song, Ke Cai, and Tingting Qu. "Analysis of Longitudinal Cracks of Casing in Heavy Oil Thermal Recovery Well." Journal of Physics: Conference Series 2519, no. 1 (June 1, 2023): 012037. http://dx.doi.org/10.1088/1742-6596/2519/1/012037.
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Abstract This paper investigates cracking failure of the casing tube. There were longitudinal cracks in the heavy oil thermal recovery well occurred in an oil field. The fracture cause of casing was analyzed by macrographic observation, chemical composition analysis, mechanical property test, metallographic analysis, scanning electron microscope (SEM) and residual stress calculation. The results showed that the crack of the failed casing originates from the external surface of the pipe and has the characteristic of intergranular propagation. The fracture characteristics are brittle fracture. The conclusion showed that stress corrosion cracking(SCC) is the main cause of longitudinal crack of casing in the heavy oil thermal recovery well. Under the combined action of external corrosive media and internal stress, SCC cracks are generated on the surface of casing, and the cracks propagate along grain boundaries and finally lead to cracking and failure of casing. Some recommendations were proposed to avoid similar failures.
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Wang, Zhen Hong, Guo Xin Zhang, and Shu Ping Yu. "Crack Mechanism, Temperature Control, and Anti-Cracking Measures of Sluice." Applied Mechanics and Materials 405-408 (September 2013): 1217–20. http://dx.doi.org/10.4028/www.scientific.net/amm.405-408.1217.
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To address the problem of sluice concrete easily cracking during construction, this study introduces the crack mechanism of concrete structures. Temperature differences and constraints are the main causes of cracks. Anti-cracking measures should focus on optimizing concrete mixing ratio and improving construction technology. Using simulation calculation to model the actual construction process and temperature control measures, this study analyzes the causes of crack and selects timely and reasonable temperature control measures, which are necessary links in engineering construction. A three-dimensional finite element analysis was conducted for a huge concrete sluice structure. The causes of cracks are discussed, and timely and feasible anti-cracking measures are proposed to provide technical support for project construction.
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Sonnenschein, Robert, Juraj Bilčík, and Katarína Gajdošová. "Parameter Analysis of the Reinforcement for the Width and Spacing Control of the Early-Age Cracks in Concrete." Key Engineering Materials 691 (May 2016): 14–27. http://dx.doi.org/10.4028/www.scientific.net/kem.691.14.
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Early-age volume changes in concrete induced by temperature change, hydration, autogenous and drying shrinkage can lead to concrete cracking and this can have lasting effects on serviceability, durability or aesthetics of the structure. The restraint to thermal movement is the product of the coefficient of the temperature fall from a peak level during cement hydration and a restraint factor. In most cases it is not necessary and also not economical to avoid cracks. In these cases, crack widths are limited due to water tightness, durability or aesthetic reasons. If early-age thermal cracking cannot be prevented, crack width can be controlled with reinforcement. The reinforcement distributes cracks and consequently reduces their widths and spacing. As a result, there forms a large number of smaller cracks instead of a few through-cracks. This means, that due to the formation of fine cracks, the strain capacity of a reinforced concrete element before the occurrence of through cracks can be increased with the help of skin reinforcement. This paper discusses the parameters of reinforcement affecting the width and spacing of early-age cracks in concrete. The effect of reinforcement on early-age cracking in concrete was investigated on numerical simulation and in full-scale experiments. The test variables were the reinforcement ratio and the cover thickness of the longitudinal reinforcing bars.
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Xu, Yaxing, Xin Yao, Yan Zhuang, Wei Duan, Xidong Zhang, Shunlei Hu, and Xiaoqiang Dong. "The Effects of Fiber Inclusion on the Evolution of Desiccation Cracking in Soil-Cement." Materials 14, no. 17 (August 31, 2021): 4974. http://dx.doi.org/10.3390/ma14174974.
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Desiccation cracking frequently occurs in mud, clay, and pavement. Understanding the evolution of desiccation cracking may facilitate the development of techniques to mitigate cracking and even prevent it from developing altogether. In this study, experimental investigations were performed focusing on the effects of fibers on the evolution of desiccation cracking in soil-cement. Varied types of fibers (i.e., jute fiber and polyvinyl alcohol fiber (PVA)) and fiber contents (i.e., 0%, 0.25%, 0.5%, and 1%) were involved. The digital image correlation (DIC) method was employed to capture the evolution and propagation of cracks in the soil-cement specimens when subjected to desiccation. The results show that the presence of fibers imposes significant effects on the crack propagation pattern as well as the area and length of the cracks in the soil-cement during shrinkage. The addition of fibers, however, insignificantly affects the evaporation rate of the specimens. The crack area and crack length of the specimens decreased significantly when more fibers were included. There were no macroscopic cracks observed in the specimens where the fiber content was 1%. The DIC method effectively helped to determine the evolution of displacement and strain field on the specimens’ surface during the drying process. The DIC method is therefore useful for crack monitoring.
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Underwood, John H., Gregory N. Vigilante, Christopher P. Mulligan, and Mark E. Todaro. "Thermomechanically Controlled Erosion in Army Cannons: A Review." Journal of Pressure Vessel Technology 128, no. 2 (January 11, 2006): 168–72. http://dx.doi.org/10.1115/1.2175022.
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Metallographic characterization is presented of thermal damage of Cr-coated steel in a fired cannon; Cr and Ta coated steel in a vented-erosion-simulator; and bulk Si3N4 in laser heating. Common features of rapid crack-induced erosion are noted. (i) Cracks form normal to the surface, often permanently open, indicating tensile stress was present at some point during thermal damage. (ii) Softening of Cr and Ta coatings and Si3N4 occurs near the heated surface, verified by metallography and hot hardness. The transformation of steel beneath the coatings is used as an in-situ verification of temperatures that cause thermal damage. (iii) Crack-induced under-cutting of thermal-damage islands is observed for coatings and bulk Si3N4. A thermomechanical analysis of rapid crack-induced erosion observed in severe cannon firing and firing simulation suggests the following key failure mechanisms common to metals and Si3N4. (i) High near-bore transient temperatures increase thermal expansion compression and concurrently decrease the elevated temperature strength. For metals, the thermal compression stress greatly exceeds strength, to depths of about 0.5mm. (ii) Thermal stress exceeding strength produces compressive yielding, which, upon cooling, causes tensile residual stress and cracking. The near-bore residual tension is high enough to cause one-cycle cracking of both Cr and Ta coatings; hydrogen from combustion enters via the cracks and causes cracking in the steel below the coating. For Si3N4, cracks are encouraged by the low fracture toughness of Si3N4. (iii) Repeated thermal cycles deepen and widen cracks to form islands that can be undercut, leading to island removal and rapid erosion failure of the cannon. For Cr and Ta coatings, undercutting is by hydrogen cracking in the steel and degradation of the coating interface by combustion products that enter via the cracks. For Si3N4, undercutting is by direct thermomechanical cracking.
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Huang, Y., N. Y. Li, H. W. Zhang, and K. C. Hwang. "Interactive Growth of Multiple Fiber-Bridged Matrix Cracks in Unidirectional Composites." Journal of Engineering Materials and Technology 118, no. 3 (July 1, 1996): 295–301. http://dx.doi.org/10.1115/1.2806809.
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A model is developed for monotonic and cyclic fiber sliding in a fiber-reinforced composite containing multiple cracks. The model is used to study the fatigue growth of multiple cracks in a matrix reinforced with aligned, continuous fibers, where cracks are bridged by frictionally constrained fibers. It is established that the crack tip stress intensity factor is significantly reduced in multiple cracking due to interactions among cracks and among slip zones. The fatigue crack does not grow as fast as that for a single bridged crack or for multiple nonbridged cracks, thus the approach to steady-state crack growth is significantly delayed.
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De Francisco, Unai, Felix Beckmann, Julian Moosmann, Nicolas O. Larrosa, and Matthew J. Peel. "3D characterisation of hydrogen environmentally assisted cracking during static loading of AA7449-T7651." International Journal of Fracture 232, no. 1 (October 28, 2021): 93–116. http://dx.doi.org/10.1007/s10704-021-00595-y.
Full textAbstract:
AbstractIn this investigation, synchrotron X-ray microtomography was used to perform 3D in situ observations of crack initiation and growth during hydrogen environmentally assisted cracking (HEAC) in tensile samples of AA7449-T7651. Two smooth tensile samples with a 1 mm diameter gauge section were held at a fixed displacement ($$\approx 30$$ ≈ 30 % of yield stress) in warm, moist air ($$\approx 76\,^\circ $$ ≈ 76 ∘ C, 73% relative humidity). The samples were then imaged repeatedly using X-ray tomography until they fractured completely. The tomograms showing the nucleation and evolution of intergranular cracks were correlated with electron microscopy fractographs. This enabled the identification of crack initiation sites and the characterisation of the crack growth behaviour relative to the microstructure. The samples were found to fracture within an environmental exposure time of 240 min. Some cracks in both samples nucleated within an exposure time of 80 min (33–40% of the total lifetime). Many cracks were found to nucleate both internally and at the sample surface. However, only superficial cracks contributed to the final fracture surface as they grew faster owing to the direct environmental exposure and the larger crack opening. HEAC occurred prominently via brittle intergranular cracking, and cracks were found to slow down when approaching grain boundary triple junctions. Additionally, crack shielding from nearby cracks and the presence of coarse Al–Cu–Fe particles at the grain boundaries were also found to temporarily reduce the crack growth rates. After prolonged crack growth, the HEAC cracks displayed ductile striations and transgranular fracture, revealing a change in the crack growth mechanism at higher stress intensity factors.