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Academic literature on the topic 'Cracks and Cracking'
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Journal articles on the topic "Cracks and Cracking"
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 (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.
Full textAbstract:
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.
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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.
Full textAbstract:
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.
5
Spaeth, Stephen C. "Imbibitional Stress and Transverse Cracking of Bean, Pea, and Chickpea Cotyledons." HortScience 21, no. 1 (1986): 110–11. http://dx.doi.org/10.21273/hortsci.21.1.110.
Full textAbstract:
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.
Full textAbstract:
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.
7
Pais, Jorge. "The Reflective Cracking in Flexible Pavements." Romanian Journal of Transport Infrastructure 2, no. 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.
9
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 (2005): 99–109. http://dx.doi.org/10.1177/0361198105194000112.
Full textAbstract:
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.
10
Zamora, M., and J. P. Poirier. "Experimental study of acoustic anisotropy and birefringence in dry and saturated Fontainebleau sandstone." GEOPHYSICS 55, no. 11 (1990): 1455–65. http://dx.doi.org/10.1190/1.1442793.
Full textAbstract:
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.