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1
Lee, Chang Soon, In Shik Cho, Young Shik Pyoun e In Gyu Park. "Study of Inner Micro Cracks on Rolling Contact Fatigue of Bearing Steels Using Ultrasonic Nano-Crystalline Surface Modification". Key Engineering Materials 462-463 (gennaio 2011): 979–84. http://dx.doi.org/10.4028/www.scientific.net/kem.462-463.979.
Testo completoAbstract (sommario):
The purpose of this study is to analyze the effect of ultrasonic nano-crystalline surface modification (UNSM) treatment on rolling contact fatigue (RCF) characteristics of bearing steels. It was found that severe plastic deformation occurred at surface by over 100 µm after UNSM treatment. The micro surface hardness was increased by 18%, and the measured compressive residual stress was as high as -700~-900MPa. The polymet RCF-2 roller type RCF test showed over 2 times longer fatigue lifetime after UNSM treatment under Hertzian contact stress of 425.2kg/mm2 and 8,000 rpm. And SEM study showed a spalling phenomenon at the samples which went through the RCF test after UNSM treatment. Samples before UNSM treatment produced surface initiated spalls and multi shear lips by progressive spalling at the end along the rolling direction, but sub-surface initiated spalls were formed without multi shear lips after UNSM treatment. The spalling occurred at once, and the size and depth of spalls were larger than those before UNSM treatment. And micro cracks were found to form within the spallings after UNSM treatment, and stress distribution at the maximum Herzian shear stress through these micro cracks is thought to improve the fatigue lifetime of bearing materials.
2
Figueiredo, B., J. Vatcher, J. Sjöberg e D. Mas Ivars. "Effects of the initial stress and spalling strength on spalling around deposition holes and tunnels". IOP Conference Series: Earth and Environmental Science 1124, n. 1 (1 gennaio 2023): 012110. http://dx.doi.org/10.1088/1755-1315/1124/1/012110.
Testo completoAbstract (sommario):
Abstract Spalling in the deposition holes and tunnel stability are of concern for the design of deep geological repositories for spent nuclear fuel. A 3D numerical stress model, including a single deposition tunnel and multiple deposition holes to analyse the potential for spalling resulting from the excavation phase, was developed for the proposed repository location at the Forsmark site. Several potential initial stress field cases and spalling strengths of the intact rock were considered. The magnitudes of the factor of safety, the spalling depth, the minor principal stress, and the differential stress were evaluated. The results showed that no spalling in the central deposition hole is indicated for the most likely stress field, and the occurrence of spalling and the spalling depth are minimised for a maximum horizontal stress aligned approximately parallel to the tunnel axis. For spalling occurrence and depth of spalling, the magnitude of the maximum horizontal stress is more critical than its orientation, and the spalling strength is more critical than the magnitude of the maximum horizontal stress. No instability problems were indicated in the vicinity of the roof for all analysed stress cases.
3
Qiao, Rujia, Yinbo Guo, Hang Zhou e Huihui Xi. "Explosive Spalling Mechanism and Modeling of Concrete Lining Exposed to Fire". Materials 15, n. 9 (26 aprile 2022): 3131. http://dx.doi.org/10.3390/ma15093131.
Testo completoAbstract (sommario):
Traditional heat transfer analysis has been adopted to predict the damage in a tunnel under fire without considering the effect of concrete spalling, which leads to underestimation of the fire damage of concrete. However, accounting for the spalling effect of concrete under high temperature in an analytical heat transfer model is difficult because of the complexity of the spalling mechanism. This study aims to establish an analytical model to estimate the influence of concrete spalling on the fire-damage depth prediction. To overcome this challenge, first, a series of fire tests were conducted in a unidirectional heating system. The spalling phenomenon and spalling characteristics were observed. Based on the experimental test results, the moisture content of concrete is one of the key factors of spalling. Obvious layered spalling characteristics of concrete samples without drying could be observed under the unidirectional heat conduction system. The critical temperature of spalling is 600 °C, and the thickness of the spalling layer is 2 cm~2.5 cm. These two parameters are critical spalling conditions. Second, a multilayer model for the heat transfer analysis considering the spalling effect of tunnel lining under fire was proposed. By using Laplace transform and the series solving method for ordinary differential equations, the time-dependent temperature and stress fields of concrete lining during tunnel fire could be obtained, which are the basis of damage evolution. The analytical results agreed with the experimental data. The spalling depth of tunnel lining related to the temperature rise of tunnel fire could be predicted by using the proposed analytical model. The results of this research can be used to provide a better damage evaluation of tunnel lining under fire.
4
Zhao, Jie, Jian Jun Zheng e Gai Fei Peng. "Modeling of Vapor Pressure Build-Up in Heated High-Performance Concrete". Applied Mechanics and Materials 204-208 (ottobre 2012): 3691–94. http://dx.doi.org/10.4028/www.scientific.net/amm.204-208.3691.
Testo completoAbstract (sommario):
Under high temperature conditions, such as fire, high-performance concrete will undergo material degradation or even spalling. Spalling is the most detrimental to concrete structures. To prevent concrete from spalling, the mechanism should be understood. Since the build-up vapor pressure in concrete is supposed to play a dominant role in spalling, a vapor pressure prediction model is proposed in this paper to quantitatively analyze the vapor pressure, which can be used for the spalling mechanism study.
5
Tian, Kai Pei, Yang Ju, Hong Bin Liu, Jin Hui Liu, Li Wang, Peng Liu e Xi Zhao. "Effects of Silica Fume Addition on the Spalling Phenomena of Reactive Powder Concrete". Applied Mechanics and Materials 174-177 (maggio 2012): 1090–95. http://dx.doi.org/10.4028/www.scientific.net/amm.174-177.1090.
Testo completoAbstract (sommario):
The explosive spalling of high-strength concrete due to fire is a problem that has garnered increasingly widespread attention, particularly the explosive spalling of reactive powder concrete (RPC). For years, based on the vapor pressure mechanism, the addition of fibers has been demonstrated to be somewhat effective in protecting against spalling. However, relevant experiments indicate that fibers are not effective for dense concrete, which is a challenge for the simple vapor pressure mechanism in providing spalling resistance for RPC. The authors found that silica fume plays an important role in the explosive spalling of RPC. Thus, four classes of RPCs with different ratios of silica fume were prepared, and the spalling phenomena and the inner temperature distribution during heating were investigated. The results show that silica fume content has a prominent effect on the spalling process of RPC.
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PRESTON, F. W. "THEORY OF SPALLING*". Journal of the American Ceramic Society 16, n. 1-12 (17 ottobre 2006): 131. http://dx.doi.org/10.1111/j.1151-2916.1933.tb19208.x.
Testo completo
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Buravova, Svetlana. "Erosion spalling mechanism". Wear 157, n. 2 (settembre 1992): 359–70. http://dx.doi.org/10.1016/0043-1648(92)90072-g.
Testo completo
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Zhao, Jie, Jian Jun Zheng e Gai Fei Peng. "Fire Spalling Modeling of High Performance Concrete". Applied Mechanics and Materials 52-54 (marzo 2011): 378–83. http://dx.doi.org/10.4028/www.scientific.net/amm.52-54.378.
Testo completoAbstract (sommario):
Under high temperature conditions, such as fire, high performance concrete will undergo material degradation or even spalling. Spalling is the most detrimental damage to concrete structures. To prevent concrete from spalling, the mechanism should be understood. In this paper, an anisotropic damage model, in which both the thermal stress and vapor pressure are incorporated, is presented to analyze the spalling mechanism. The spalling phenomenon is studied based on two cases of different moisture contents. It is concluded that when the vapor pressure is present, concrete will behave much more brittlely.
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Wang, Kaiyun, Wanming Zhai, Kaikai Lv e Zaigang Chen. "Numerical Investigation on Wheel-Rail Dynamic Vibration Excited by Rail Spalling in High-Speed Railway". Shock and Vibration 2016 (2016): 1–11. http://dx.doi.org/10.1155/2016/9108780.
Testo completoAbstract (sommario):
Spalling in contact surface of rail is a typical form of rolling contact fatigue, which is a difficult problem to solve in railway. Once the spalling occurs in the rail, the wheel-rail dynamic interaction will become more severe. The wheel-rail dynamic interaction is investigated based on the theory of vehicle-track coupled dynamics in this paper, where the excitation modes of the rail spalling failure are taken into consideration for high-speed wheel-rail system. A modified excitation model of rail spalling failure is proposed. It can enable the investigations on two kinds of excitation modes in wheel-rail system due to the rail spalling, including the pulse and the harmonic excitation modes. The excitation mode can be determined by the ratio of the spalling length to its critical length. Thus, the characteristics of wheel-rail dynamic vibration excited by two kinds of excitation are simulated in detail. Consequently, the limited value of the spalling length is suggested for high-speed railway.
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Chen, Jun. "Effect of Transient Creep on the Structural Performance of Reinforced Concrete Walls under Fire". Buildings 14, n. 2 (2 febbraio 2024): 406. http://dx.doi.org/10.3390/buildings14020406.
Testo completoAbstract (sommario):
This paper investigates and reveals the effect of the high-temperature transient creep on the structural performance of RC walls under fire. A theoretical model is established, which explicitly includes the transient creep and accounts for the explosive spalling, the material, and geometric nonlinearities under fire. The effects of the transient creep on the structural response and fire resistance of RC walls with little spalling and with explosive spalling are investigated, respectively, with elucidation of the mechanisms. The influences of wall geometries, concrete properties, and the eccentricity of load on the effect of the transient creep are quantitatively studied. Finally, the results are validated through comparison with tests in the literature. It is revealed that the transient creep significantly reduces the fire resistance of RC walls with little spalling by up to and greater than 60%, by decreasing the deflection toward the heated side. However, it increases the fire resistance of RC walls with explosive spalling by up to about 40% by reducing the spalling extent due to the stress relaxation effect. The stress relaxation effect of the transient creep has a crucial role in determining the spalling manner. The load level, the eccentricity of load, and the wall geometries are key influencing factors which have contrary influences on the effect of the transient creep on the fire resistance of RC walls with little spalling and with explosive spalling.
11
Zhou, Mingliang, Wen Cheng, Hongwei Huang e Jiayao Chen. "A Novel Approach to Automated 3D Spalling Defects Inspection in Railway Tunnel Linings Using Laser Intensity and Depth Information". Sensors 21, n. 17 (25 agosto 2021): 5725. http://dx.doi.org/10.3390/s21175725.
Testo completoAbstract (sommario):
The detection of concrete spalling is critical for tunnel inspectors to assess structural risks and guarantee the daily operation of the railway tunnel. However, traditional spalling detection methods mostly rely on visual inspection or camera images taken manually, which are inefficient and unreliable. In this study, an integrated approach based on laser intensity and depth features is proposed for the automated detection and quantification of concrete spalling. The Railway Tunnel Spalling Defects (RTSD) database, containing intensity images and depth images of the tunnel linings, is established via mobile laser scanning (MLS), and the Spalling Intensity Depurator Network (SIDNet) model is proposed for automatic extraction of the concrete spalling features. The proposed model is trained, validated and tested on the established RSTD dataset with impressive results. Comparison with several other spalling detection models shows that the proposed model performs better in terms of various indicators such as MPA (0.985) and MIoU (0.925). The extra depth information obtained from MLS allows for the accurate evaluation of the volume of detected spalling defects, which is beyond the reach of traditional methods. In addition, a triangulation mesh method is implemented to reconstruct the 3D tunnel lining model and visualize the 3D inspection results. As a result, a 3D inspection report can be outputted automatically containing quantified spalling defect information along with relevant spatial coordinates. The proposed approach has been conducted on several railway tunnels in Yunnan province, China and the experimental results have proved its validity and feasibility.
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Lakhani, Hitesh, e Jan Hofmann. "Effect of spalling on predicted temperature gradients and flexural capacity: numerical model". Journal of Structural Fire Engineering 11, n. 2 (17 novembre 2019): 151–65. http://dx.doi.org/10.1108/jsfe-01-2019-0010.
Testo completoAbstract (sommario):
Purpose The paper aims to present an advanced 2 D transient heat transfer analysis capable of accounting for the effect of spalling in terms of amount, location and time. The model accounts for moving thermal boundary conditions to comply with the changing member cross section. The discussed numerical model provides a tool to quantify the effect of spalling on the flexural capacity of reinforced concrete beams. Design/methodology/approach The implementation of the presented numerical model in an in-house code and its validation has been discussed. The thermal subroutine has been sequentially coupled with the mechanical subroutine (sectional-analysis) to compute the variation of sectional moment carrying capacity with exposure time. Findings The temperatures predicted while considering spalling were in good agreement with experiments available in literature. The presented results also emphasise the importance of considering the time of spalling. The results also show that the fire rating of simply supported beams is also affected by spalling in the compression zone. Research limitations/implications It should be acknowledged that the model does not predict spalling, rather is developed as a tool to study the effect of spalling. The model takes the information related to spalling in terms of the location, amount and time, as user input. Originality/value The paper quantitatively presents the effect of spalling on the predicted temperature variation across the beam cross section and the moment carrying capacity.
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Cui, Feng, Tinghui Zhang e Xiaoqiang Cheng. "Research on Control of Rib Spalling Disaster in the Three-Soft Coal Seam". Shock and Vibration 2021 (16 giugno 2021): 1–15. http://dx.doi.org/10.1155/2021/2404218.
Testo completoAbstract (sommario):
Rib spalling disaster at the coal mining faces severely restricted the safe and efficient output of coal resources. In order to solve this problem, based on the analysis of the current status of rib spalling in the three-soft coal seam 1508 Working Face of Heyang Coal Mine, a mechanical model of sliding-type rib spalling was established and the main influencing factors that affect rib spalling are given. The mechanism of grouting technology to prevent and control rib spalling has been theoretically analyzed. A similarity simulation experiment is used to analyze the change law of roof stress under the condition of three-soft coal seam mining. The optimal grouting pressure is determined by a numerical simulation experiment. And, silicate-modified polymer grouting reinforcement materials (SMPGMs) are used in field experiments. After twice grouting operations in the 1508 Working Face, the coal wall was changed from the original soft and extremely easy rib spalling to a straight coal wall and the amount of rib spalling has been reduced by 57.45% and 48.43, respectively. And, the mining height has increased by 0.16 m and 0.23 m, respectively. The experimental results show that the rib spalling disaster of the three-soft coal seam has been effectively controlled.
14
Murmu, Sunny, e Gnananandh Budi. "Study on the Mechanism, Prediction, and Control of Coal Wall Spalling in Deep Longwall Panels Utilizing Advanced Numerical Simulation Methodology". Geofluids 2022 (9 luglio 2022): 1–19. http://dx.doi.org/10.1155/2022/5622228.
Testo completoAbstract (sommario):
This research looked at the occurrence of coal wall spalling, a type of longwall face failure, during the main weighing period (MWP) for panels greater than 300 m depth. FLAC3D software was exploited to simulate the ground condition of longwall panel 1 of Adriyala Longwall Project mine. The extent and severity of coal wall spalling were quantified using evaluation criteria based on the concepts of vertical stress distribution and maximum shear strain. Subsequently, a parametric analysis of thirteen factors influencing the coal wall spalling was carried out. Empirical equations for predicting coal wall spalling were suggested. Based on the parametric analysis, a coal wall spalling classification system (CWSC) chart is presented to predict spalling characteristics of coal wall that may occur at the MWP. The empirical models depicted good predictive ability with R 2 values greater than 0.9. Parametric analysis revealed that coal wall spalling is highly sensitive to seam compressive strength, mining-induced stress, extraction height, and immediate roof characteristics. The CWSC system’s applicability to the five panels was in good agreement with field observations.
15
Hager, Izabela, e Katarzyna Mróz. "Role of Polypropylene Fibres in Concrete Spalling Risk Mitigation in Fire and Test Methods of Fibres Effectiveness Evaluation". Materials 12, n. 23 (23 novembre 2019): 3869. http://dx.doi.org/10.3390/ma12233869.
Testo completoAbstract (sommario):
The explosive behaviour of concrete in fire is observed in rapidly heated concrete. The main factors controlling the occurrence of spalling are related to the material’s low porosity and high density as well as the limited ability to transport gases and liquids. Thus, for high-strength, ultrahigh-strength, and reactive powder concrete, the risk of spalling is much higher than for normal-strength concrete. The paper presents the discussion on the leading hypothesis concerning the occurrence of concrete spalling. Moreover, the methods for spalling prevention, such as polypropylene fibre application, which has been found to be an effective technological solution for preventing the occurrence of spalling, are presented. Various tests and testing protocols are used to screen concrete mixes propensity toward spalling and to evaluate the polypropylene fibres’ effectiveness in spalling risk mitigation. The most effective testing methods were selected and their advantages were presented in the paper. The review was based mainly on the authors’ experiences regarding high performance concrete, reactive powder concrete testing, and observations on the effect of polypropylene fibres on material behaviour at high temperature.
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Rickard, Ieuan, Luke Bisby e Susan Deeny. "Explosive spalling of concrete in fire: novel testing to mitigate design risk". Structural Engineer 96, n. 1 (2 gennaio 2018): 42–47. http://dx.doi.org/10.56330/uyzk7228.
Testo completoAbstract (sommario):
Heat-induced explosive spalling in fire poses a credible risk to concrete structures, and has received considerable research attention in recent decades. However, no validated guidance to enable the design of concrete mixes to prevent spalling, nor any established, widely verified, repeatable test methods are yet available to confidently quantify or demonstrate spalling resistance for a particular mix in a given application. As a result, no models yet exist that can predict spalling with sufficient confidence to be used in design. This paper summarises contemporary research on heat-induced concrete spalling, with particular emphasis on design for fire of concrete-lined tunnels. The topic is also relevant for modern concrete buildings. A novel, repeatable and economical testing method to reduce project risk by quantifying the propensity of concrete mixes for spalling under a range of different thermal and mechanical conditions is described. The intent of this paper is to present the limitations of knowledge to enable design for heat-induced spalling, and to highlight research currently under way to overcome some of the issues faced in practice.
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Li, Rong Tao. "Application of Fuzzy Pattern Recognition in Spalling Risk Evaluation of Concrete Structures at High Temperature". Advanced Materials Research 919-921 (aprile 2014): 451–54. http://dx.doi.org/10.4028/www.scientific.net/amr.919-921.451.
Testo completoAbstract (sommario):
Spalling phenomenon in concrete exposed to high temperatures, e.g. during a fire, can seriously jeopardize the integrity of a whole structure. Spalling risk analysis and evaluation has become the hot topic of research on fire-resistance behavior of concrete structures at present. Based on fuzzy pattern recognition, a model for evaluating spalling risk of concrete structures at high temperature is established according to the factors influencing explosive spalling. The influential factor set is composed of strength, water/cement ratio, fibres content, curing humidity, load level, and heating rate, whose weights are determined by their relative importance. Good agreements between the results of spalling risk prediction and the fire test show the capability of the proposed model in assessing the spalling risk of concrete structures at high temperature, which will provide important reference for the fire resistance design of concrete structures.
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Liu, Hongtao, Yang Chen, Zijun Han, Qinyu Liu, Zilong Luo, Wencong Cheng, Hongkai Zhang, Shizhu Qiu e Haozhu Wang. "Coal Wall Spalling Mechanism and Grouting Reinforcement Technology of Large Mining Height Working Face". Sensors 22, n. 22 (10 novembre 2022): 8675. http://dx.doi.org/10.3390/s22228675.
Testo completoAbstract (sommario):
To control the problem of coal wall spalling in large mining height working faces subject to mining, considering the Duanwang Mine 150505 fully mechanized working face, the mechanism of coal wall spalling in working faces was investigated by theoretical analysis, numerical simulation and field experiment. Based on analysis of coal wall spalling in the working face, a new grouting material was developed. The stress and plastic zone changes affecting the coal wall, before and after grouting in the working face, were analyzed using numerical simulation and surrounding rock grouting reinforcement technology was proposed for application around the new grouting material. The results showed that: (1) serious spalling of the 150505 working face was caused by the large mining height, fault influence and low roof strength, and (2) the new nano-composite low temperature polymer materials used have characteristics of rapid reaction, low polymerization temperature, adjustable setting time, high strength and environmental protection. Based on analysis of the working face coal wall spalling problem, grouting reinforcement technology based on new materials was proposed. Industrial tests were carried out on the working face. Field monitoring showed that the stability of the working face coal wall was significantly enhanced and that rib spalling was significantly improved after comprehensive anti-rib-spalling grouting measures were adopted. These results provide a basis for rib spalling control of working faces under similar conditions.
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Min, G., D. Fukuda, S. Oh, H. Liu e S. Cho. "Verification of Spalling Tensile Strength of Rocks using 3D GPGPU-accelerated Hybrid FEM/DEM". IOP Conference Series: Earth and Environmental Science 1124, n. 1 (1 gennaio 2023): 012117. http://dx.doi.org/10.1088/1755-1315/1124/1/012117.
Testo completoAbstract (sommario):
Abstract The spalling test is widely applied for evaluating dynamic tensile strength of rock under high strain-rate condition. The dynamic tensile strength is indirectly measured in the spalling test by theoretically assuming the tensile stress level at the failure position of a cylindrical specimen based on the 1D stress wave propagation theory. However, the theoretical estimation method for dynamic tensile strength have not been fully validated since dynamic tensile strength was determined with insufficient understanding of the fracture process, such as crack propagation and stress distribution in the rock specimen during the spalling test, owing to observational limitations in the experiment. Thus, a proper validation method is required for the proposed method, and numerical simulation can be used to validate the proposed method by reproducing the tensile fracture process of the rock specimen during the spalling test. Thus, the dynamic spalling tensile test for rock specimens was reproduced in this study using the GPGPU-based 3D hybrid FDEM that we recently developed. The dynamic tensile fracturing process was analyzed in the simulation of spalling under various strain-rate conditions. Finally, we discussed the application of various theoretical estimation methods to the 3D spalling test.
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Peng, Gai Fei, Xu Jie Duan, Xue Chao Yang e Ting Yu Hao. "Behavior of High Performance Steel-Fiber Concrete Exposed to High Temperature in Terms of Spalling and Permeability". Key Engineering Materials 629-630 (ottobre 2014): 252–58. http://dx.doi.org/10.4028/www.scientific.net/kem.629-630.252.
Testo completoAbstract (sommario):
An experimental investigation was conducted on behavior of high performance steel-fiber concrete subjected to high temperature, in terms of explosive spalling and permeability. A series of concretes incorporated steel fiber at various dosages were prepared, and further processed to have a series of moisture contents. Explosive spalling tests were conducted on control plain concrete and steel fiber concrete. After explosive spalling tests, each of the specimens that didn’t encounter spalling was sawn into two pieces. Crack observations and permeability tests were conducted on the sawn surfaces. The results prove that steel fiber is efficient to avoid spalling concrete under high temperature. The permeability increases significantly after thermal exposure, while it also exhibits an ascending trend with the increase of moisture content. Therefore it is concluded that steel fiber can play a positive effect on explosive spalling of high performance concrete under high temperature, as well as on permeability after thermal exposure.
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Lu, Fang Xia, e Mario Fontana. "Concrete Permeability and Explosive Spalling in Fire". Key Engineering Materials 711 (settembre 2016): 541–48. http://dx.doi.org/10.4028/www.scientific.net/kem.711.541.
Testo completoAbstract (sommario):
Permeability of concrete is a good indicator of the risk of explosive spalling, concrete with low permeability is more prone to explosive spalling. To study explosive spalling of concrete, experimental tests on the concrete permeability have been carried out at ETH. The influences from temperature and moisture content have been investigated. The permeability of concrete is found to increase with the temperature and to decrease with moisture content. Based on the test results, a permeability model has been proposed. The explosive spalling has been predicted and an engineering boundary permeability for the liability to spalling is recommended to be 2 × 10-17 m2 for a concrete slab heated according to ISO fire curve. The boundary permeability is influenced by moisture content, tensile strength and heating rate.
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Ye, Wan Jun, Geng She Yang, Xian Li e Ning Zhuang. "Treatment Materials for Spalling on Loess Slope". Advanced Materials Research 150-151 (ottobre 2010): 425–28. http://dx.doi.org/10.4028/www.scientific.net/amr.150-151.425.
Testo completoAbstract (sommario):
Spalling on loess slope threats the safety of highway and destroys its ecological environment. This paper proposes treatment materials for medium thickness spalling on loess slope. This materials treat the spalling in loess slope by the Reinforced function of straw, Bonding effect of silt, retain soil moisture and insulation effect of straw silt nutrition materials of silt mixed with straw, and fixation effect of T-shaped spiral steel anchor net, so that the treated slope can be protected and greened. It can effectively reinforce the loess slope, and prevent it from spalling.
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He, Fu Lian, Xiao Ming Wang, De Quan Zhang e Shang Sen He. "Study on Parameters of Support for Control of Roof Fall and Rib Spalling in Large Fully Mechanized Top Coal Caving End Face". Advanced Materials Research 616-618 (dicembre 2012): 421–25. http://dx.doi.org/10.4028/www.scientific.net/amr.616-618.421.
Testo completoAbstract (sommario):
Key factors affecting the control of roof fall and rib spalling are identified relying on the statistics for characteristics of roof fall and rib spalling distribution, and the regression analysis of the relationships of roof fall and rib spalling to support parameters by measuring actual ground pressures. The effect of support in controlling roof fall and rib spalling is analyzed by setting up a caving arch mechanical model of cataclastic coal and rock mass on fully mechanized caving face, and the key parameters of support are also determined using numerical simulation.
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Miah, Md Jihad, Francesco Lo Monte, Roberto Felicetti, Hélène Carré, Pierre Pimienta e Christian La Borderie. "Fire Spalling Behaviour of Concrete: Role of Mechanical Loading (Uniaxial and Biaxial) and Cement Type". Key Engineering Materials 711 (settembre 2016): 549–55. http://dx.doi.org/10.4028/www.scientific.net/kem.711.549.
Testo completoAbstract (sommario):
Fire poses one of the most severe environmental conditions that can act on concrete structures as an external load and can induce severe damages (cracks, spalling) or even lead to collapse. Fire spalling of concrete is a complex phenomenon, which might occur due to pressure build-up in the pores, thermal and load-induced stresses. In this context, ordinary concrete specimens (B40-II and B40-III: fc28days ≈ 40 MPa) were exposed to standard fire curve (ISO 834-1), while a constant uniaxial or biaxial compressive load was applied. Six different levels of uniaxial compressive stress on cubes and four different levels of biaxial compressive stress on slabs have been investigated. The test results showed that loaded specimens are more susceptible to spalling than unloaded specimens, with increasing amount of spalling for higher values of applied load. It has been found that biaxially loaded specimens are more prone to spalling than uniaxially loaded specimens. B40-II concrete (3% of slag) exhibited higher spalling than the B40-III concrete (43% of slag).
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Khan, Mehran, Mingfeng Kai, Muhammad Ahmad, Jiancong Lao e Jian-Guo Dai. "Fire Performance of Fiber-reinforced Ultra-High-Performance Concrete: A state-of-the-art review". Journal of Asian Concrete Federation 9, n. 1 (30 giugno 2023): 65–102. http://dx.doi.org/10.18702/acf.2023.9.1.65.
Testo completoAbstract (sommario):
Explosive spalling is a major problem for structures made of ultra-high-performance concrete (UHPC) after being exposed to fire, which hinders their practical applications. To overcome this obstacle, fibers have become an essential constituent of UHPC in past decades. This paper summarizes a state-of-the-art review related to the fire performance of UHPC using single and hybrid fibers. The spalling behavior, spalling mechanism, mechanical properties, and microstructure characteristics of fiber-reinforced UHPC are summarized, and structural performance of fiber-reinforced UHPC members at elevated temperatures is discussed. This review reveals that fire-induced spalling is a significant concern in UHPC, and it can be caused by various mechanisms. The addition of fibers can play a crucial role in preventing spalling, and different mechanisms for different types of fibers have been reported in the literature for UHPC with both single and hybrid fibers. Therefore, fiber hybridization is recommended to enhance the spalling resistance of UHPC. The future directions and challenges for UHPC at both the material and structural levels are discussed.
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Mohammed, Hussein, Hawreen Ahmed, Rawaz Kurda, Rayed Alyousef e Ahmed Farouk Deifalla. "Heat-Induced Spalling of Concrete: A Review of the Influencing Factors and Their Importance to the Phenomenon". Materials 15, n. 5 (24 febbraio 2022): 1693. http://dx.doi.org/10.3390/ma15051693.
Testo completoAbstract (sommario):
Heat-induced spalling in concrete is a problem that has been the subject of intense debate. The research community has, despite all the effort invested in this problem, few certain and definitive answers regarding the causes of and the way in which spalling happens. A major reason for this difficulty is the lack of a unified method for testing, which makes comparing data from various studies against each other a difficult task. Many studies have been performed that show the positive effects of using synthetic micro-fibres, such as polypropylene (PP). The mechanism with which PP fibres improve heat-induced spalling resistance in concrete, however, remains a subject of debate. This paper, therefore, looks at the work that has been performed in the field of spalling (particularly spalling of self-compacting concrete (SCC)). Influencing factors are identified and their links to each other (as reported) are discussed. A particular emphasis is put on discussing the role of PP fibres and how they improve the behaviour of high-performance concrete (HPC) at elevated temperatures. A brief summary of the reviewed papers are provided for each of the influencing factors to help the reader navigate with ease through the references. An introduction to heat-induced spalling and the common causes (as reported in the literature) is also included to highlight the wide range of theories trying to explain the spalling phenomenon.
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Li, Guosheng, Zhenhua Li, Feng Du e Zhengzheng Cao. "Study on the Failure Characteristics of Coal Wall Spalling in Thick Coal Seam with Gangue". Advances in Civil Engineering 2020 (14 dicembre 2020): 1–10. http://dx.doi.org/10.1155/2020/6668458.
Testo completoAbstract (sommario):
Coal wall spalling is one of the main factors restricting the safe and efficient mining of thick coal seam, and the gangue has an important impact on the coal wall spalling. To obtain the failure characteristics of coal wall spalling in thick coal seam containing gangue, numerical calculation and theoretical research were used to analyze the morphological differences of coal wall spalling with different gangue positions. Besides, the damage depth, width, and stress environment of coal wall panel caused by the position of gangue were mainly studied, and the failure mechanics model of coal seam containing gangue was established by using the stability theory of pressure bar. The results show that, compared with coal wall spalling in coal seam without gangue, coal seam with the lower and middle gangue has a significant weakening effect on the wall spalling, and coal seam with the upper gangue has little effect on the wall spalling. In the case of coal seam with gangue, the upper gangue has the highest risk area of coal wall spalling with the maximum depth and width of 2.0 m and 2.3 m. For coal seam with the upper gangue, the dangerous areas of coal wall spalling are mainly distributed in the vicinity of the gangue; for coal seam without the gangue, they are mainly distributed in the middle of the coal seam. The gangue cannot change the law of the external stress distribution of the coal seam, but it has an obvious impact on the internal stress distribution of the coal seam. With the different positions of the gangue, the stress distribution in the coal seam has a great difference, and the maximum difference is 1.8 MPa. This shows that the stress environment of the coal seam containing gangue has the following typical characteristics: “the external stress is controlled by the overburden fracture, and the internal stress environment is controlled by the gangue.” Through the mechanical analysis of the coal seam containing gangue, it is further verified that the coal seam containing gangue is more prone to spalling at the position of gangue.
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Yu, Xin Meng, Xiao Xiong Zha e Zhao Hui Huang. "The Influence of Spalling on the Fire Resistance of RC Structures". Advanced Materials Research 255-260 (maggio 2011): 519–23. http://dx.doi.org/10.4028/www.scientific.net/amr.255-260.519.
Testo completoAbstract (sommario):
A great many of experiments has shown that reinforced concrete (RC) structures suffered from spalling in fire. However, at present there are still no convincing spalling predicting models available due to the inhomogeneous nature and complicated thermo-hydro-mechanical interactions in concrete at elevated temperatures. In order to evaluate the fire resistance of RC structures which are subjected to concrete spalling, a thermal analysis procedure is developed which considers the effects of spalling on the growth of temperature in RC members. The predicted temperatures are then used to model the structural behaviour. The spalled portion of concrete is modelled as "void", which has no thermal and mechanical properties. A series of parametric studies carried out on RC structural members with different boundary conditions shows that the influence of spalling on fire resistance is very significant apart from the RC slabs subject to higher laterally restraint.
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Ding, Y., e J. A. Gear. "Spalling depth prediction model". Wear 267, n. 5-8 (giugno 2009): 1181–90. http://dx.doi.org/10.1016/j.wear.2008.12.064.
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McKinney, John, e Faris Ali. "Artificial Neural Networks for the Spalling Classification & Failure Prediction Times of High Strength Concrete Columns". Journal of Structural Fire Engineering 5, n. 3 (19 agosto 2014): 203–14. http://dx.doi.org/10.1260/2040-2317.5.3.203.
Testo completoAbstract (sommario):
This paper presents the results from two supervised Artificial Neural Networks (ANN) developed for the spalling classification and failure prediction of high strength concrete columns (HSCC) subjected to fire. The experimental test data used for the ANN are based on the HSCC tests undertaken at the Fire Research Laboratories at the University of Ulster. 80% of the chosen experimental test data was used to train the network with the remaining 20% used for testing. In the spalling classification example the key ANN input parameters were; furnace temperature, restraint, loading level, force, spalling degree, failure time and spalling type. This was also the case for the failure prediction example except for spalling type. The networks were trained using the resilient propagation algorithm. A 6-10-3 and 5-10-1 ANN architecture gave the best results for the classification and failure prediction times respectively. The results demonstrate that HSCC can be assessed using ANN.
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Khayyat, Maha M. "Crystalline Silicon Spalling as a Direct Application of Temperature Effect on Semiconductors’ Indentation". Crystals 11, n. 9 (25 agosto 2021): 1020. http://dx.doi.org/10.3390/cryst11091020.
Testo completoAbstract (sommario):
Kerf-less removal of surface layers of photovoltaic materials including silicon is an emerging technology by controlled spalling technology. The method is extremely simple, versatile, and applicable to a wide range of substrates. Controlled spalling technology requires a stressor layer, such as Ni, to be deposited on the surface of a brittle material; then, the controlled removal of a continuous surface layer can be performed at a predetermined depth by manipulating the thickness and stress of the Ni layer, introducing a crack near the edge of the substrate, and mechanically guiding the crack as a single fracture front across the surface. However, spalling Si(100) at 300 K (room temperature RT) introduced many cracks and rough regions within the spalled layer. These mechanical issues make it difficult to process these layers of Si(100) for PV, and in other advanced applications, Si does not undergo phase transformations at 77 K (Liquid Nitrogen Temperature, LNT); based on this fact, spalling of Si(100) has been carried out. Spalling of Si(100) at LNT improved material quality for further designed applications. Mechanical flexibility is achieved by employing controlled spalling technology, enabling the large-area transfer of ultrathin body silicon devices to a plastic substrate at room temperature.
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Sohn, Y. C., Jin Yu, S. K. Kang, D. Y. Shih e T. Y. Lee. "Spalling of intermetallic compounds during the reaction between lead-free solders and electroless Ni-P metallization". Journal of Materials Research 19, n. 8 (agosto 2004): 2428–36. http://dx.doi.org/10.1557/jmr.2004.0297.
Testo completoAbstract (sommario):
Intermetallic compound (IMC) spalling from electroless Ni-P film was investigated with lead-free solders in terms of solder-deposition methods (electroplating, solder paste, and thin foil), P content in the Ni-P film (4.6, 9, and 13 wt% P), and solder thickness (120 versus .200 μm). The reaction of Ni-P with Sn3.5Ag paste easily led to IMC spalling after 2-min reflow at 250 °C while IMCs adhered to the Ni-P layer after 10-min reflow with electroplated Sn or Sn3.5Ag. It has been shown that not only the solder composition but also the deposition method is important for IMC spalling from the Ni-P layer. The spalling increased with P content as well as with solder volume. Ni3Sn4 intermetallics formed as a needle-shaped morphology at an early stage and changed into a chunk-shape. Needle-shaped compounds exhibited a higher propensity for spalling than chunk-shaped compounds because many channels among the needle-shaped IMCs facilitated Sn penetration. A reaction between the penetrated Sn and the Ni3P layer formed a Ni3SnP layer and Ni3Sn4 IMCs spalled off the Ni3SnP surface. Dewetting of solder from the Ni3SnP layer, however, did not occur even after spalling of most IMCs.
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Tanjung, Ardhymanto Am. "Understanding parameters impacting the mechanism leading to spalling around underground excavations in massive rocks under high stress". IOP Conference Series: Earth and Environmental Science 1228, n. 1 (1 agosto 2023): 012008. http://dx.doi.org/10.1088/1755-1315/1228/1/012008.
Testo completoAbstract (sommario):
Abstract Underground excavation is required for mining engineering and nuclear waste repository. As the excavation progresses, the stress increases, and brittle failures frequently exist. Brittle failures are arranged into two types: spalling and rock bursting. Spalling in the shape of a V-notch may severely damage the machine and workers involved in its development. This potential hazard can be mitigated by fully representing all parameters that cause spalling in the model. Thus, optimized tunnel design can be achieved. As a result, the company can strike a balance between profit and safety. Several possible results can be proposed by conducting a series of sensitivity studies on a credible model based on a real-world case study of spalling in the Underground Research Laboratory (URL) in Canada. It includes predicting the Depth of Failure (DOF) of spalling by changing two main parameters, particularly strength (tensile and crack initiation) and stress (σ1). The result reveals that increasing tensile strength over UCS decreases DOF, increasing percentages of crack initiation (CI) over UCS decreases DOF, and increasing σmax over UCS increases DOF. Moreover, systematic errors in the generated model can lead to inaccurate DOF estimation. This problem must be approached with engineering judgment in order for the solution to correspond to the actual spalling phenomenon.
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Choi, Pangil, Lochana Poudyal, Fouzieh Rouzmehr e Moon Won. "Spalling in Continuously Reinforced Concrete Pavement in Texas". Transportation Research Record: Journal of the Transportation Research Board 2674, n. 11 (10 settembre 2020): 731–40. http://dx.doi.org/10.1177/0361198120948509.
Testo completoAbstract (sommario):
The performance of continuously reinforced concrete pavement (CRCP) in Texas has been quite satisfactory, primarily thanks to the continuous improvements in design and construction. However, severe spalling has been a major problem, and the Texas Department of Transportation (TxDOT) has sponsored several research projects since 1985 to identify solutions for this serious problem. Even though the research efforts were successful in identifying spalling mechanisms, developing a policy that TxDOT could easily implement has been a challenge. To develop a more practical solution to this problem, TxDOT initiated a research study, and the research efforts consisting of identifying CRCP projects with severe and no spalling, obtaining and conducting materials testing on concrete cores from those projects, analyzing the testing data, and performing theoretical analyses to validate the testing results. Among the material properties evaluated, the coefficient of thermal expansion (CTE) of concrete proved to have the best correlation with spalling. Detailed analyses of mechanistic behavior of concrete conducted with an object-oriented finite element program (OOF2) and commercial finite element program verified the reasonableness of the field-testing results. All concrete cores from CRCP with severe spalling had a CTE larger than 5.5 microstrains/°F, whereas no spalling was observed in concrete with a CTE less than that value. Based on this finding, TxDOT now requires the use of coarse aggregate that will produce concrete with a CTE of less than 5.5 microstrains/°F for CRCP construction. It is expected that this implementation will reduce the spalling in CRCP substantially.
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Hwang, Euichul, Gyuyong Kim, Gyeongcheol Choe, Minho Yoon, Minjae Son, Dongkyun Suh, Hamin Eu e Jeongsoo Nam. "Explosive Spalling Behavior of Single-Sided Heated Concrete According to Compressive Strength and Heating Rate". Materials 14, n. 20 (13 ottobre 2021): 6023. http://dx.doi.org/10.3390/ma14206023.
Testo completoAbstract (sommario):
In this study, the effects of heating rate and compressive strength on the spalling behavior of single-sided heated ring-restrained concrete with compressive strengths of 60 and 100 MPa were investigated. The vapor pressure and restrained stress inside the concrete were evaluated under fast- and slow-heating conditions. Regardless of the heating rate, the concrete vapor pressure and restrained stress increased as the temperature increased, and it was confirmed that spalling occurred in the 100-MPa concrete. Specifically, it was found that moisture migration and restrained stress inside the concrete varied depending on the heating rate. Under fast heating, moisture clogging and restrained stress occurred across the concrete surface, causing continuous surface spalling for the 100-MPa concrete. Under slow heating, moisture clogging occurred, and restrained stress continuously increased in the deep area of the concrete cross-section owing to the small internal temperature difference, resulting in explosive spalling for the 100-MPa concrete with a dense internal structure. Additionally, while the tensile strength of concrete is reduced by heating, stress in the heated surface direction is generated by restrained stress. The combination of stress in the heated concrete surface and the internal vapor pressure generates spalling. The experimental results confirm that heating rate has a significant influence on moisture migration and restrained stress occurrence inside concrete, which are important factors that determine the type of spalling.
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Wang, Ligang, e Dan G. Zollinger. "Mechanistic Design Framework for Spalling Distress". Transportation Research Record: Journal of the Transportation Research Board 1730, n. 1 (gennaio 2000): 18–24. http://dx.doi.org/10.3141/1730-03.
Testo completoAbstract (sommario):
Spalling is a distress form in concrete pavements that often manifests as the breakdown of the joint of a slab within 15 cm (6 in.) of the joint or crack and can occur at both longitudinal and transverse joints. Efforts have been under way at Texas A&M University to formulate mechanistic spalling models derived from data gathered in recent Texas Department of Transportation studies related to spall development. Extensive field studies have led to the establishment of a spalling mechanism consisting of a step-by-step process that can be characterized with engineering mechanics. These findings indicate that spalling is the result of damage initiated in the form of a shear delamination that is oriented parallel to and at a shallow depth below the surface of the pavement. Conditions necessary for formation of the delaminations include low interfacial strength between the aggregate and mortar and sufficient evaporation of pore water from the hydrating concrete, resulting in differential drying shrinkage near the pavement surface. Delaminations have been noted to initiate early in the life of the pavement and, once formed, extend later into spalls as a result of incompressibles, freeze-thaw cycles, traffic loading, and other such effects. A design framework for delamination formation and subsequent spalling development is presented in a practical format in which to mechanistically design concrete pavement systems relative to spalling distress.
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Liu, Hai Yuan, Hou Sheng Jia, Long Fan e Bin Han. "The Theory and Practice of Forepoling Pre-Stressed System Bolt in Preventing the Rib Spalling". Advanced Materials Research 734-737 (agosto 2013): 883–87. http://dx.doi.org/10.4028/www.scientific.net/amr.734-737.883.
Testo completoAbstract (sommario):
Based on the particularity of loose and broken of the surrounding rock of roadway, there will be rib spalling after excavating of roadway without support problem. Through analyzing for the specific reasons of the rib spalling, the theory of forepoling pre-stressed system and forepoling support project were put forward. The broken rock zone test in normal roadway support indicating that this technology can effectively prevent the rib spalling before and after digging, having good supporting effect and economic benefits.
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Hoang, Nhat-Duc, Thanh-Canh Huynh e Van-Duc Tran. "Concrete Spalling Severity Classification Using Image Texture Analysis and a Novel Jellyfish Search Optimized Machine Learning Approach". Advances in Civil Engineering 2021 (10 dicembre 2021): 1–20. http://dx.doi.org/10.1155/2021/5551555.
Testo completoAbstract (sommario):
During the phase of building survey, spalling and its severity should be detected as earlier as possible to provide timely information on structural heath to building maintenance agency. Correct detection of spall severity can significantly help decision makers develop effective maintenance schedule and prioritize their financial resources better. This study aims at developing a computer vision-based method for automatic classification of concrete spalling severity. Based on input image of concrete surface, the method is capable of distinguishing between a minor spalling in which the depth of the broken-off material is less than the concrete cover layer and a deep spalling in which the reinforcing steel bars have been revealed. To characterize concrete surface condition, image texture descriptors of statistical measurement of color channels, gray-level run length, and center-symmetric local binary pattern are used. Based on these texture-based features, the support vector machine classifier optimized by the jellyfish search metaheuristic is put forward to construct a decision boundary that partitions the input data into two classes of shallow spalling and deep spalling. A dataset consisting of 300 image samples has been collected to train and verify the proposed computer vision method. Experimental results supported by the Wilcoxon signed-rank test point out that the newly developed method is highly suitable for concrete spall severity classification with accuracy rate = 93.33%, F1 score = 0.93, and area under the receiver operating characteristic curve = 0.97.
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Cherif, Guergah, Dimia Mohamed Salah e Benmarce Abdelaziz. "Numerical Modelling of One-Way Reinforced Concrete Slab in FireTaking Into Account of Spalling". Civil Engineering Journal 7, n. 3 (3 marzo 2021): 477–87. http://dx.doi.org/10.28991/cej-2021-03091667.
Testo completoAbstract (sommario):
This paper presents a study of the behaviour of Reinforced Concrete (RC) slabs subjected to severe hydrocarbon fire exposure. In which the spalling phenomena of concrete is to be considered. The hydrocarbon curve is applicable where small petroleum fires might occur, i.e. car fuel tanks, petrol or oil tankers, certain petro-chemical facilities, tunnels, parking structures, etc. Spalling is included using a simplified approach where elements with temperatures higher than 400 °C are assumed to occur and the corresponding thermo-mechanical response of RC slabs is evaluated. The nonlinear finite element software SAFIR has been used to perform a numerical analysis of the spalling risk, by removing layers of concrete covering when a set of spalling criteria is checked. The numerical results obtained by finite element analysis of the temperature distribution within the slab and mid-span deflection were compared with published experimental data. Predictions from the numerical model show a good agreement with the experimental data throughout the entire fire exposure to the hydrocarbon fire. This shows that this approach (layering procedure) is very useful in predicting the behaviour of concrete spalling cases. Doi: 10.28991/cej-2021-03091667 Full Text: PDF
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Fernandes, Bruno, Hélène Carré, Jean-Christophe Mindeguia, Céline Perlot e Christian La Borderie. "Fire spalling sensitivity of concrete made with recycled concrete aggregates (RCA)". Acta Polytechnica CTU Proceedings 33 (3 marzo 2022): 168–74. http://dx.doi.org/10.14311/app.2022.33.0168.
Testo completoAbstract (sommario):
The fire spalling of concrete is a complex phenomenon, which can affect the integrity of the structures during a fire. This thermal instability is associated with a complex coupled chemo-thermo-hydro-mechanical mechanism and it can be influenced by many factors, related to material (e.g. per- meability, porosity and water content), geometry (e.g. shape and size) and environmental parameters (e.g. mechanical load and heating rate). Concrete made with recycled concrete aggregates presents higher porosity, higher water content and different interfaces between aggregates and mortar. All these aspects can lead to a different behaviour under fire exposure, including the spalling risk of these sustainable concretes. The main objective of this paper is to analyse the influence of the use of recycled concrete aggregates on the spalling risk of concrete. In this paper, concrete prisms with different replacement rates of recycled coarse aggregates (0 up to 100%) were exposed to a standard fire curve (ISO 834-1) with a constant uniaxial compression load. After heating, samples surfaces were evaluated by means of digital photogrammetry. Results showed that concrete with RCA is sensitive to explosive spalling. All replacement rates presented higher degree of spalling than concrete made with natural aggregates.
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Tsai, M. H., Y. W. Lin, H. Y. Chuang e C. R. Kao. "Effect of Sn concentration on massive spalling in high-Pb soldering reaction with Cu substrate". Journal of Materials Research 24, n. 11 (novembre 2009): 3407–11. http://dx.doi.org/10.1557/jmr.2009.0398.
Testo completoAbstract (sommario):
The massive spalling of Cu3Sn in the soldering reaction between high-Pb solders and Cu substrates was studied to identify the mechanism behind this rather interesting and frequently observed phenomenon. Four different alloys (99.5 Pb 0.5 Sn, 99 Pb 1S n, 97 Pb 3 Sn, and 95 Pb 5 Sn, in wt%) were soldered at 350 °C for durations ranging from 10 s to 600 min. At low Sn concentration (0.5 or 1 Sn), massive spalling occurred as early as 20 min. However, at high Sn concentration (3 or 5 Sn), massive spalling was not completed even after 600 min. To the best of our knowledge, these results are the most detailed observations ever reported on the sequence of events that occur during massive spalling. The Pb–Sn–Cu phase diagram is used to rationalize the phenomenon.
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Hajihasani, Nadia, e Norhisham Bakhary. "Detection of Concrete Spalling Using Changes in Modal Flexibility". Advanced Materials Research 163-167 (dicembre 2010): 2598–602. http://dx.doi.org/10.4028/www.scientific.net/amr.163-167.2598.
Testo completoAbstract (sommario):
This paper presents a study in the effect of spalling to dynamic parameters such as natural frequencies and mode shapes. Numerical example of a slab is used as an example in this study. The slab will be modelled using ANSYS 11.0 and various types of spalling are imposed. The changes of vibration parameters are monitored and compared. To compare the sensitivity of modal parameters to spalling is determined using the flexibility method. Based on the results it is found that by incorporating mode shapes using flexibility method, damage location and severity can be obtained.
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Ozawa, Mitsuo, Zhou Bo, Yuichi Uchida e Hiroaki Morimoto. "Preventive Effects of Fibers on Spalling of UFC at High Temperatures". Journal of Structural Fire Engineering 5, n. 3 (19 agosto 2014): 229–38. http://dx.doi.org/10.1260/2040-2317.5.3.229.
Testo completoAbstract (sommario):
This paper investigates the relationship between spalling behavior and weight loss for ultra-high-strength fiber-reinforced concrete (UFC) containing different types short fibers (jute, PP, WSPVA) in high-temperature environments at 400, 600 and 800 °C. The explosive spalling that occurred under these conditions caused severe damage to the control specimen but only slight damage to the specimen with jute fiber. It was therefore inferred that adding 0.19% by volume of natural jute fibers (length: 12 mm) to UFC is effective in the prevention of spalling-related damage.
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Williams, R. E., R. M. Potter e S. Miska. "Experiments in Thermal Spallation of Various Rocks". Journal of Energy Resources Technology 118, n. 1 (1 marzo 1996): 2–8. http://dx.doi.org/10.1115/1.2792690.
Testo completoAbstract (sommario):
The greatest limitation of the spallation process is its inability to spall (or to consistently spall) many rocks encountered in petroleum drilling and mining operations. The New Mexico Institute of Mining and Technology has conducted a series of experiments to investigate the possibility of expanding the use of the spallation process to the penetration of rocks generally considered not to be spallable. The methods used during this work were 1) spalling at temperatures below that produced by the stoichiometric burning of fuel oil and air, and 2) spalling by alternately heating and quenching the rock surfaces. No success was experienced in spalling at the lower temperatures, but initial tests showed the alternate heating and chilling system to be successful, particularly in penetrating travertine limestone. However, continued testing indicated that, unless the rocks are extremely uniform in composition, spalling will result in highly irregular holes or holes that cannot be directionally controlled.
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Shi, Cheng-Hua, Ang Wang, Xiao-He Sun e Wei-Chao Yang. "Aerodynamic Behavior and Impact on Driving Safety of Spalling Blocks Comprising High-Speed-Railway Tunnel Lining". Applied Sciences 12, n. 5 (2 marzo 2022): 2593. http://dx.doi.org/10.3390/app12052593.
Testo completoAbstract (sommario):
The lining of operating high-speed-railway tunnels suffers from cracks, the peeling of material, and other deteriorations and defects, all of which seriously affect driving safety. However, the trajectory of a falling block from the tunnel lining in a tunnel train wind environment and its impact on driving safety are unknown. To study the movement of falling blocks under a coupling effect of tunnel train wind and the local flow field of the falling blocks, a three-dimensional gas–solid-coupling numerical calculation model of spalling blocks–train–tunnel–air was established using FLUENT software The aerodynamic evolution mechanism governing the spalling blocks of the lining was analyzed, and we found that the falling process of a spalling block is affected by the coupling of its own characteristics and transient train wind. Train wind directly induced the horizontal motion of falling blocks, generated curves and eddy currents, and changed the motion state of spalled blocks. Furthermore, by comprehensively considering the motion trajectories of flaky and blocky blocks at different positions, the impact of spalling blocks on driving safety was obtained. The dangerous area of spalling blocks was approximately 5.5 m above the ground, which must be paid attention to. Our results provide guidance for the operation and maintenance of high-speed-railway tunnels.
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Wu, Hangbin, Xingran Ao, Zhuo Chen, Chun Liu, Zeran Xu e Pengfei Yu. "Concrete Spalling Detection for Metro Tunnel from Point Cloud Based on Roughness Descriptor". Journal of Sensors 2019 (2 maggio 2019): 1–12. http://dx.doi.org/10.1155/2019/8574750.
Testo completoAbstract (sommario):
Automatic concrete spalling detection has become an important issue for metro tunnel examinations and maintenance. This paper focuses on concrete spalling detection research with surface roughness analysis based on point clouds produced by 3D mobile laser scanning (MLS) system. In the proposed method, at first, the points on ancillary facilities attached to tunnel surface are considered as outliers and removed via circular scan-line fitting and large residual error filtering. Then, a roughness descriptor for the metro tunnel surface is designed based on the triangulated grid derived from point clouds. The roughness descriptor is generally defined as the ratio of surface area to the projected area for a unit, which works well in identifying high rough areas on the tunnel surface, such as bolt holes, segment seams, and spalling patches. Finally, rough area classification based on Hough transformation and similarity analysis is performed on the identified areas to accurately label patches belonging to segment seams and bolt holes. After removing the patches of bolt holes and segment seams, the remaining patches are considered as belonging to concrete spalling. The experiment was conducted on a real tunnel interval in Shanghai. The result of concrete spalling detection revealed the validity and feasibility of the proposed method.
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Yang, Juan, e Gai Fei Peng. "The Mechanism of Explosive Spalling and Measures to Resistant Spalling of Concrete Exposed to High Temperature by Incorporating Fibers: A Review". Advanced Materials Research 168-170 (dicembre 2010): 773–77. http://dx.doi.org/10.4028/www.scientific.net/amr.168-170.773.
Testo completoAbstract (sommario):
Many experimental researches have been conducted on explosive spalling performance of concrete of high-strength / high performance concrete (HSC/HPC). This paper summarizes two main explosive spalling mechanisms (Vapor pressure build-up mechanism and Thermal stress mechanism) of concrete at elevated temperature, and also presents the measures to resistant the explosive spalling, i.e. by incorporating fibers (polypropylene fiber(PPF), steel fiber(SF) and hybrid fiber of the first two). Finally, the further studies of both the mechanism and the measures are proposed. Also, the preliminary study of ultra high-strength concrete (UHSC) on fire-resistance are mentioned.
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Savenkov, G. G. "Fractal cluster model of spalling". Technical Physics 47, n. 12 (dicembre 2002): 1529–32. http://dx.doi.org/10.1134/1.1529942.
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Bedell, Stephen W., Keith Fogel, Paul Lauro, Davood Shahrjerdi, John A. Ott e Devendra Sadana. "Layer transfer by controlled spalling". Journal of Physics D: Applied Physics 46, n. 15 (21 marzo 2013): 152002. http://dx.doi.org/10.1088/0022-3727/46/15/152002.
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Norton, F. H. "DISCUSSION ON “THEORY OF SPALLING”*". Journal of the American Ceramic Society 16, n. 1-12 (17 ottobre 2006): 423–24. http://dx.doi.org/10.1111/j.1151-2916.1933.tb19257.x.
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