Academic literature on the topic 'Spalling damage'
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Journal articles on the topic "Spalling damage"
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Zhao, Jie, Jian Jun Zheng, and Gai Fei Peng. "Fire Spalling Modeling of High Performance Concrete." Applied Mechanics and Materials 52-54 (March 2011): 378–83. http://dx.doi.org/10.4028/www.scientific.net/amm.52-54.378.
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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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Erzar, B., and E. Buzaud. "Shockless spalling damage of alumina ceramic." European Physical Journal Special Topics 206, no. 1 (May 2012): 71–77. http://dx.doi.org/10.1140/epjst/e2012-01588-0.
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Ozawa, Mitsuo, Zhou Bo, Yuichi Uchida, and Hiroaki Morimoto. "Preventive Effects of Fibers on Spalling of UFC at High Temperatures." Journal of Structural Fire Engineering 5, no. 3 (August 19, 2014): 229–38. http://dx.doi.org/10.1260/2040-2317.5.3.229.
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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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Potisuk, Tanarat, Christopher C. Higgins, Thomas H. Miller, and Solomon C. Yim. "Finite Element Analysis of Reinforced Concrete Beams with Corrosion Subjected to Shear." Advances in Civil Engineering 2011 (2011): 1–14. http://dx.doi.org/10.1155/2011/706803.
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Finite element (FE) modeling techniques were developed to isolate the different contributions of corrosion damage to structural response of experimental reinforced concrete beams with shear-dominated behavior. Corrosion-damage parameters included concrete cover spalling due to the expansion of corrosion products; uniform stirrup cross-sectional loss from corrosion; localized stirrup cross-sectional loss due to pitting; debonding of corrosion-damaged stirrups from the concrete. FE analyses were performed including both individual and combined damages. The FE results matched experimental results well and quantitatively estimated capacity reduction of the experimental specimens.
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Diederichs, Mark S. "The 2003 Canadian Geotechnical Colloquium: Mechanistic interpretation and practical application of damage and spalling prediction criteria for deep tunnelling." Canadian Geotechnical Journal 44, no. 9 (September 2007): 1082–116. http://dx.doi.org/10.1139/t07-033.
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Spalling and strain bursting has long been recognized as a mechanism of failure in deep underground mines in hard rock and in deep infrastructure tunnels. The latter is a significant growth industry, particularly in Europe where subalpine base tunnels in excess of 10 m wide and dozens of kilometres long are being driven by tunnel boring machine (TBM) through alpine terrain at depths greater than 2 km. In more massive granitoid or gneissic ground, these tunnels have experienced significant spalling damage. En route to a practical predictive technique for this condition, the author utilizes a number of analytical and micromechanical tools to validate a simple empirical predictive model for tunnel spall initiation. The true nature of damage and of yield, as the result of extensile damage accumulation, in hard rocks is examined using these tools. Based on the resultant conceptual model, the author expands on the empirical damage threshold, using a spalling limit to differentiate stress paths that lead to crack propagation and spalling from those that incur stable microdamage prior to conventional shear failure at higher relative confinements. Finally, the composite and robust in situ yield model is applied to nonlinear modelling for support design.
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Eratodi, I. Gusti Lanang Bagus, Ali Awaludin, Ay Lie Han, and Andreas Triwiyono. "Evaluation and Study of Prestressed Slab Structure Precast Modular Concrete." MEDIA KOMUNIKASI TEKNIK SIPIL 26, no. 1 (July 30, 2020): 44–51. http://dx.doi.org/10.14710/mkts.v26i1.27765.
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Prestressed precast modular concrete slabs function rigid pavement, supporting vehicle loads above it on subgrade with relatively low bearing capacity. This slab measures 2000 x 850 x 150 mm3 of regular reinforced concrete (old production) or prestressed concrete (new production) quality K-500. After several times of use, damage occurs mainly at the end of the slab in the form of spalling. The objectives of the study and evaluation were: (1) observing damage; (2) material quality data; (3) numerical modeling by taking into account material properties, loading and soil conditions; and (4) providing slab design recommendations including materials and geometrics. The method of study and evaluation of slab damage was done by observing the damage, taking concrete core-case and testing it in the laboratory, and modeling the slab structure with various parameters (soil data, concrete quality and slab geometry). Field observations and analysis results show that concrete slab spalling occurs initially at the edge (850 mm wide) which in turn causes the effectiveness of the pre-tension force to be suboptimal and finally the concrete spalling volume increases. Apart from the frequency of collisions during installation and slab deformation when supporting vehicle loads. Concrete spalling problems also due to inappropriate concrete quality.
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Chu, Hong Yan, Jin Yang Jiang, Wei Sun, and Ming Zhong Zhang. "Mechanical Properties and Damage Evolution of Siliceous Concrete Subjected to Elevated Temperatures." Key Engineering Materials 711 (September 2016): 488–95. http://dx.doi.org/10.4028/www.scientific.net/kem.711.488.
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Siliceous concrete (SC) is applied in European Pressurized Water Reactor that is a key component of the third generation nuclear power plant. This paper investigates the mechanical properties and damage evolution of SC (with and without polypropylene fibers) exposed to high temperatures. The mass loss, compressive strength, splitting tensile strength and spalling sensitivity of SC before and after being heated to 200, 400, 600, 800, and 1000 °C are investigated. The ultrasonic testing technique was used to assess the thermal damage, by evaluating the variations of the ultrasonic wave velocity (UWV) for different temperature levels. According to the available literature, a new relationship between damage and UWV was proposed to establish a damage evolution model of SC. The results indicated that: (a) specimens without polypropylene (PP) fibers suffered severe spalling in the range 380-400°C and 470-510°C, while no spalling took place in the specimens with PP fibers in the whole range 25-1000°C; (b) the damage evolution with and without polypropylene fibers was similar, and could adequately be described by means of a Weibull distribution model.
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Celeste Blasone, Maria, Dominique Saletti, Edward Andò, Julien Baroth, and Pascal Forquin. "Investigation of Spalling Damage in Ultra-High Performance Concrete Through X-ray Computed Tomography." EPJ Web of Conferences 183 (2018): 03024. http://dx.doi.org/10.1051/epjconf/201818303024.
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Ultra-high performance concretes (UHPC) are increasingly used to build protective structures such as headquarters, nuclear power plants or critical civil engineering structures. However, under impact or contact detonation, concrete is exposed to high-rate tensile loadings that can lead to intense damage modes. Such complex damage modes need to be correctly characterised. When a UHPC sample is subjected to a dynamic tensile loading by means of the spalling technique the post-mortem pattern shows a large number of fractures that cannot be seen with a classical observation of the external face (inner crack network). In the framework of the Brittle’s CODEX chair project, the fracturing process in spalled samples of UHPC is investigated with X-ray computed tomography. The tensile loading is applied thanks to a spalling technique that is based on the reflection of a compressive wave on a free boundary. The concrete samples are entirely scanned using X-ray tomography prior spalling test to identify the initial microstructure, and post spalling test to analyse the damage pattern. Image analysis tools are used in both steps. The main fracturing properties are related to the microstructure of the tested concrete.
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Wang, Shimin, Chuankun Liu, Gaoyu Ma, Songyu Cao, Junbo Zhang, Daiyue Lu, and Chuan He. "Experimental Investigation on the Influence of Regional Concrete Spalling on Shield Tunnel Segments." Advances in Civil Engineering 2019 (June 27, 2019): 1–15. http://dx.doi.org/10.1155/2019/1829124.
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Based on the field investigation and analysis, the mechanical characteristics of segment structure in shield tunnels are compared and analyzed under the circumstances of different concrete spalling region by the method of similarity model experiment. Through data analysis of acoustic emission, the results for displacement and internal force of shield tunnel segments are clarified on the segment lining, the influential rule of load bearing capacity is also determined, and the deformation and stress for the different concrete spalling region are described as well. The corresponding research results indicate that range for elastic bearing stage is enlarged while it is narrowed for plastic bearing stage, the convergence and deformation and the accumulated event numbers for acoustic emission on critical instability point are obviously increasing, and the process of damage and failure tends to be sudden for segment lining structure. The ultimate bearing capacity of the damaged segment lining obviously decreases due to regional concrete spalling; to be more specific, the reduction rate for ultimate bearing capacity becomes 6%, 6%, and 13%, respectively, when the range of concrete spalling reaches 45°, 60°, and 75°.
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Park, Gang-Kyu, Gi-Joon Park, Jung-Jun Park, Namkon Lee, and Sung-Wook Kim. "Residual Tensile Properties and Explosive Spalling of High-Performance Fiber-Reinforced Cementitious Composites Exposed to Thermal Damage." Materials 14, no. 7 (March 25, 2021): 1608. http://dx.doi.org/10.3390/ma14071608.
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This study examined the effect of adding synthetic fibers, that is, polypropylene (PP) and nylon (Ny), on explosive spalling and residual tensile mechanical properties of high-performance fiber-reinforced cementitious composites (HPFRCCs). Three different matrix strengths (100 MPa, 140 MPa, and 180 MPa), four different volume contents of the synthetic fibers (0%, 0.2%, 0.4%, and 0.6%), and three different exposure time (1 h, 2 h, and 3 h) based on the Internatinoal Organization for Standardization (ISO) fire curve were adopted as variables for this experiment. The experimental results revealed that the addition of synthetic fibers improved the resistance to explosive spalling induced by high-temperature, especially when PP and Ny were mixed together. For a higher matrix strength, greater volume content of the synthetic fibers was required to prevent explosive spalling, and higher residual strengths were obtained after the fire tests. An increase in the volume fraction of the synthetic fibers clearly prevented explosive spalling but did not affect the residual tensile strength. In the case of a higher matrix strength, a reduction in the strength ratio was observed with increased exposure time.
Dissertations / Theses on the topic "Spalling damage"
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Wang, Xiaofeng. "Simulation models for rolling bearing vibration generation and fault detection via neural networks." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362159.
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Jerabek, Jakub, Allessandra Keil, Jens Schoene, Rostislav Chudoba, Josef Hegger, and Michael Raupach. "Experimental and Numerical Analysis of Spalling Effect in TRC Specimens." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1244046893347-05461.
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The paper presents the study of spalling effect occurring under tensile loading in thin-walled TRC specimens. The experimentally observed failure patterns are first classified and the performed experiment design is explained and discussed. A parameter study of spalling effect with varied thickness of concrete cover and reinforcement configurations including both the textile fabrics and the yarns provided the basis for numerical analysis of the effect. The applied numerical model was designed in order to capture the initiation and propagation of longitudinal cracks leading to the separation of concrete blocks from the textile fabrics. A meso-scopic material resolution in a single crack bridge is used for the simulation exploiting the periodic structure of the crack bridges both in the lateral and in the longitudinal direction of the TRC specimens. The matrix was modeled using an anisotropic damage model falling in the microplane-category of material models. The bond between yarn and matrix follows a non-linear bond-law calibrated using pull-out tests. The epoxy-impregnated reinforcement is considered as a homogeneous bar.
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Zinszner, Jean-Luc. "Identification des paramètres matériau gouvernant les performances de céramiques à blindage." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0337/document.
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Les céramiques sont couramment utilisées depuis les années 1960 comme matériaux constitutifs de blindages. En effet, grâce à leurs très bonnes propriétés physiques et mécaniques, elles permettent, pour un même niveau de protection, un gain de masse important par rapport aux blindages métalliques. Cependant, la microstructure d’une céramique peut avoir une forte influence sur sa résistance à l’impact. Le but de cette thèse est, à partir d’essais de caractérisation et en se basant sur l’utilisation de quatre nuances de carbure de silicium présentant des microstructures différentes, d’éclaircir les liens entre microstructure et performance à l’impact. Les campagnes expérimentales de compression dynamique et d’écaillage sont basées sur une utilisation innovante du moyen GEPI installé au CEA Gramat. Pour l’étude du comportement en compression dynamique des céramiques, il a permis d’utiliser la technique d’analyse lagrangienne et ainsi de remonter à l’évolution de la résistance des matériaux au cours du chargement. Pour les essais d’écaillage, il a permis, entre autres, une étude de la sensibilité à la vitesse de déformation de la résistance en traction dynamique. La caractérisation de la fragmentation dynamique est quant à elle basée sur des essais d’impact sur la tranche. Un essai innovant d’impact sur céramique préalablement fragmentée a également été dimensionné et réalisé. Ces différents essais expérimentaux ont permis de mettre en évidence et de comprendre l’influence de la microstructure du matériau sur son comportement face aux différents types de sollicitations. L’ensemble des résultats expérimentaux a été comparé à des simulations numériques permettant de valider les lois de comportement utilisées. Le modèle de fragmentation des matériaux fragiles DFH (Denoual-Forquin-Hild) a ainsi montré de très bonnes capacités à simuler le comportement des céramiques sous chargement de traction dynamique (écaillage et fragmentation)Since the sixties, ceramics are commonly used as armour materials. Indeed, thanks to their interesting physical and mechanical properties, they allow a significant weight benefit in comparison to monolithic steel plate armours. However, the microstructure of the ceramic may have a strong influence on its penetration resistance. Based on characterisation tests and on the use of four silicon carbide grades, this work aims to highlight the links between the microstructure and the ballistic efficiency. Experimental compressive and spalling tests are based on the use of the GEPI device. For studying the compressive dynamic behaviour, it allows using the lagrangian analysis method and characterising the yield strength of the material. For studying the tensile dynamic behaviour, it allows assessing the strain-rate sensitivity of the spall strength. An analysis of the fragmentation process is performed based on Edge-On Impact tests. Moreover, an innovating impact test on fragmented ceramics has been designed and performed. The different experimental results allow a better understanding of the influence of the ceramic microstructure on its behaviour under the different loadings. All the experimental data have been compared to numerical results allowing validating the constitutive models. The DFH (Denoual-Forquin-Hild) damage model of brittle materials showed very good capacities to simulate the tensile dynamic behaviour of ceramics (spalling and fragmentation)
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Onyegam, Emmanuel U. "Remote plasma chemical vapor deposition for high efficiency heterojunction solar cells on low cost, ultra-thin, semiconductor-on-metal substrates." Thesis, 2014. http://hdl.handle.net/2152/30500.
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In the crystalline Si solar cell industry, there is a push to reduce module cost through a combination of thinner substrates and increased cell efficiency. Achieving solar cells with sub-100 µm substrates cost-effectively is a formidable task because such thin substrates impose stringent handling requirements and thermal budget due to their flexibility, ease of breakage, and low yield. Moreover, as the substrate thickness decreases the surface passivation quality dictates the performance of the cells. Crystalline Si heterojunction (HJ) solar cells based on hydrogenated amorphous silicon (a-Si:H) have attracted significant interest in recent years due to their excellent surface passivation properties, potential for high efficiency, low thermal budget and low cost. HJ cells with ultra-passivated surfaces showing > 700 mV open-circuit voltages (Voc) and > 20% conversion efficiency have been demonstrated. In these cells, it has been identified that high-quality a-Si:H films deposited by a low-damage plasma process is key to achieving such high cell performance. However, the options for low-damage plasma deposition process are limited.
The main objectives of this work are to develop a low-plasma damage a-Si:H thin film deposition process based on remote plasma chemical vapor deposition (RPCVD) and to demonstrate high efficiency HJ solar cells on bulk substrates as well as on ultra-thin silicon and germanium substrates obtained by a novel, low-cost semiconductor-on-metal (SOM) technology.
This manuscript presents a detailed description of the RPCVD system and the process leading to the realization of high quality a-Si:H thin films and high efficiency HJ solar cells. First, p-type a-Si:H thin films are developed and optimized, then HJ solar cells are subsequently fabricated on bulk and ultra-thin Si and Ge SOM substrates without intrinsic a-Si:H passivation. Single HJ cells on ~ 500 µm bulk Si and ~25 µm ultra-thin substrates exhibited conversion efficiencies of η = 16% (Voc = 615 mV, Jsc = 34 mA/cm2, and FF = 77%) and η = 11.2% (Voc = 605 mV, Jsc = 29.6 mA/cm2, and FF = 62.8%), respectively. The performance of the ~25 µm cell was further improved to η = 13.4% (Voc = 645 mV, Jsc = 31.4 mA/cm2, and FF = 66.2%) by implementing the dual HJ architecture without front side i-layer passivation. For single HJ cells based on Ge substrates, the results were η = 1.78 % (Voc = 148 mV, Jsc = 35.1 mA/cm2, and FF = 1.78%) on ~500 µm bulk Ge, compared to η =5.3% (Voc = 203 mV, Jsc = 44.7 mA/cm2, and FF = 5.28%) on ~ 50 µm Ge SOM substrates. Respectively, the results obtained on ultra-thin SOM substrates are among the highest reported in literature for based on comparable architecture and substrate thickness.
In order to achieve improved cell performance, dual HJ cells with i-layer passivation of both surfaces were fabricated. First, optimized RPCVD-based i-layer films were developed by varying the deposition temperature and H2 dilution ratio (R). It was found that excellent surface passivation on planar substrates with as-deposited minority carrier lifetimes > 1 ms is achievable by using deposition temperature of 200 ºC and moderate dilution ratio 0.5 ≤ R ≤ 1, even without the more rigorous RCA pre-cleaning process typically used in literature for achieving comparable results. Subsequently, dual HJ solar cells with i-layer films were demonstrated on planar and textured bulk Si substrates showing improved conversion efficiencies of η = 17.3% (Voc = 664 mV, Jsc = 34.34 mA/cm2 and FF = 76%) and η = 19.4% (Voc = 643 mV, Jsc = 38.99 mA/cm2, and FF = 77.5%), respectively.text
Books on the topic "Spalling damage"
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Kelkar, Ajit Dhundiraj. Analyses of quasi-isotropic composite plates under quasi-static point loads simulating low-velocity impact phenomena. Norfolk, Va: Old Dominion University, 1985.
Find full textBook chapters on the topic "Spalling damage"
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Yoo, S. H., S. W. Shin, and I. K. Kim. "Optimum Dosage of PP Fiber for the Spalling Control of High Strength Reinforced Concrete Columns." In Advances in Fracture and Damage Mechanics VI, 621–24. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-448-0.621.
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Davie, C., and H. Zhang. "Numerical investigation of damage and spalling in concrete exposed to fire." In Computational Modelling of Concrete Structures, 775–84. CRC Press, 2010. http://dx.doi.org/10.1201/b10546-93.
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Guangquan, ZHOU, Z. P. TANG, and LI Xinzen. "EXPERIMENTAL STUDY OF SPALLING STRENGTH AND THE HYDRO-ELASTIC-VISCOPLASTIC CONSTITUTIVE EQUATIONS WITH DAMAGE." In Shock Compression of Condensed Matter–1991, 399–402. Elsevier, 1992. http://dx.doi.org/10.1016/b978-0-444-89732-9.50090-x.
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Xu*, Y., W. D. Qiao, Y. Q. Bao, H. Li, and Y. F. Zhang. "Pixel-level damage detection for concrete spalling and rebar corrosion based on U-net semantic segmentation." In Bridge Maintenance, Safety, Management, Life-Cycle Sustainability and Innovations, 3319–26. CRC Press, 2021. http://dx.doi.org/10.1201/9780429279119-451.
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Apostolopoulos, Charis, and Konstantinos Koulouris. "Corrosion Effect on Bond Loss between Steel and Concrete." In Structural Integrity and Failure [Working Title]. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.94166.
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This chapter is devoted to the effects of steel corrosion on bond relationship between steel and concrete. One of the basic assumptions in design of reinforced concrete members is the perfect steel - concrete bond mechanism, so that strain of reinforcing bar is the same as that of the surrounding concrete and these two different materials act as one. However, corrosion of steel reinforcement consists one of the main durability problems in reinforced concrete members, downgrade the bond behavior and therefore their structural integrity. Corrosion degrades the reinforcement itself, reducing the initial cross-section of the steel bar and its mechanical properties. Furthermore, tensile stresses in surrounding concrete caused due to oxides on the corroded reinforcement, lead to the gradual development of tensile field to the surrounding concrete, with spalling of the cover concrete and loss of bond mechanism as a consequence. In this chapter, an overview of damage of reinforced concrete due to steel corrosion is given, focused on the bond mechanism; factors that play key role in the degree of bonding and, also, proposed models of bond strength loss in correlation with the surface concrete cracking due to corrosion are indicated. To conclude, the ongoing research in this area of interest is presented, based on recent scientific studies.
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Mukherjee, Shaswata, and Saroj Mondal. "Self-Healing Properties of Conventional and Fly Ash Cementitious Mortar, Exposed to High Temperature." In Emerging Design Solutions in Structural Health Monitoring Systems, 1–11. IGI Global, 2015. http://dx.doi.org/10.4018/978-1-4666-8490-4.ch001.
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Direct stress and sub-stress caused by fire, temperature variation and external loading in a structure are most important for the development of cracks. The chemical reactions of natural healing in the matrix was not been established conclusively. The most significant factor that influences the self-healing is the precipitation of calcium carbonate crystals on the crack surface. The mechanism which contribute autogenic healing are: (a) Continued hydration of cement at cracked surface as well as continued hydration of already formed gel and also inter-crystallization of fractured crystals; (b) blocking of flow path by water impurities and concrete particles broken from the crack surface due to cracking; (c) expansion of concrete in the crack flank (swelling) and closing of cracks by spalling of loose concrete particle are also reported as the sealing mechanism by researchers. The recovery of mechanical as well as physical property was discussed by different researchers. An experimental investigation was carried out to study the autogenic healing of fire damaged fly ash and conventional cementitious mortar samples subjected to steam followed by water curing at normal atmospheric pressure. The micro cracks are generated artificially by heating the 28 days aged mortar samples at 800 Deg. C. The effect of fly-ash replacing ordinary Portland cement by 0 and 20% was studied. Recovery of compressive strength and physical properties i.e. apparent porosity, water absorption, ultrasonic pulse velocity and rapid chloride ion penetration test confirm the self-healing of micro cracks. Such healing is more prominent for fly ash mortar mix. Optical as well as scanning electron microscopy With EDAX analysis and X-ray diffraction study of the white crystalline material formed in the crack, confirms formation of calcium carbonate.
Conference papers on the topic "Spalling damage"
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Zhang, Xuhui, Bowen Liu, Wei Zhang, Qiuchi Chen, and Caiqian Yang. "Shear Behavior of Corroded RC Beams Considering Concrete Spalling Damage." In IABSE Congress, New York, New York 2019: The Evolving Metropolis. Zurich, Switzerland: International Association for Bridge and Structural Engineering (IABSE), 2019. http://dx.doi.org/10.2749/newyork.2019.1485.
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<p>Corrosion-induced concrete spalling damage and its effects on shear behavior of RC beams are investigated in the present study. An experimental test is proposed firstly to investigate the cracking and spalling of concrete covers induced by corrosion. Then, the effects of concrete spalling damage on shear capacity are clarified. Following, a simple model is proposed to quantify the section damage of concrete. And, a FE method is proposed to predict the shear behavior by considering the concrete spalling damage and bond degradation. Results show that steel corrosion induces firstly the cracking of concrete and then the spalling of concrete as the corrosion loss exceeds about 20%. The spalling angles is found to vary from 17° to 22° in present test. The slight corrosion loss less than 10% in stirrups and inclined bars has little effect on the degradation of shear capacity. The further corroded stirrups and inclined bars, and the accompanied concrete spalling damage decreases the shear capacity significantly. The proposed FE model by considering corrosion-induced steel area loss, concrete spalling damage and bond degradation has reasonable accuracy for shear behavior prediction of beams.</p>
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McDonald, Andrew, and Stephen McKinnon. "Suppression of tunnel spalling by engineered rock mass damage." In Ninth International Symposium on Ground Support in Mining and Underground Construction. Australian Centre for Geomechanics, Perth, 2019. http://dx.doi.org/10.36487/acg_rep/1925_33_mcdonald.
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Cummings, Scott M., and Cameron P. Lonsdale. "Wheel Spalling Literature Review." In ASME 2008 Rail Transportation Division Fall Technical Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/rtdf2008-74010.
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As a means of determining the conditions under which a patch of martensite (and eventually a spall) is formed on a wheel tread, the Wheel Defect Prevention Research Consortium (WDPRC) has conducted a review of wheel slide test reports and analytical models for the prediction of contact patch temperature due to wheel slide. The relative merits of the analytical models are discussed and applied to the known/assumed conditions, i.e., speed, axle load, and wheel/rail coefficients of friction (COF) for each of the wheel slide tests. The accuracy of the analytical models is evaluated with respect to test data under a variety of conditions from multiple sources. After selecting the most appropriate analytical model, wheel slide temperature predictions are given for empty cars at a variety of speeds and wheel/rail COF levels. It is concluded that the potential exists to create martensite on sliding wheels with almost any realistic combination of axle load, wheel slide duration, train speed, and wheel/rail adhesion level. Additionally, sources of wheel spalling are discussed with a focus on misapplied hand brakes and malfunctioning air brake systems. Multiple authors noted the presence of tread damage on one wheel of a wheelset with no damage at the corresponding circumferential location of the mate wheel. The accompanying theories to explain this seemingly counterintuitive finding are restated in this literature review. At the end of the paper, the actions of the WDPRC to reduce wheel spalling are briefly outlined.
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Cummings, Scott M., and Don Lauro. "Inspections of Tread Damaged Wheelsets." In ASME 2008 Rail Transportation Division Fall Technical Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/rtdf2008-74009.
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Inspections of 163 wheelsets conducted by the Wheel Defect Prevention Research Consortium (WDPRC) have produced critical information in identifying the high-level root causes of tread damage. While the overall wheel tread damage problem appears to be split fairly evenly between shelling and spalling, the type of tread damage on a wheelset is strongly linked to the type of car from which it was removed. Coal car wheels, which generally run in heavy axle load, high-mileage service with minimal yard handling, are almost exclusively subject to shelling damage with little spalling damage. On the other hand, mixed freight cars, such as tank cars and covered hopper cars, tend to run in lower mileage service with more yard handling, resulting in fewer loading cycles under lighter stress and more frequent use of hand brakes. Not surprisingly then, wheels from these types of cars were observed to have a mix of spalling and shelling damage, with spalling being the predominant damage mechanism. Nearly every high impact wheel (HIW) inspected showed either spalling, shelling, or some combination of the two. As expected, wheel impact load detector (WILD) readings and radial tread run out data were found to be related. Rim thickness deviations and rim lateral face deviations were not found to be important contributors to shelling. The lateral tread location of radial run-out deviations and crack bands could be an important clue in discovering the root cause of shelling. Radial run-out data and crack band location data shows that shelling damage is most prevalent outboard of the tapeline. This is the expected wheel/rail contact position of a wheel in the lead wheelset position of a truck, while riding on the low (inside) rail of a curve. Many of the wheels that were removed for wear causes were found to have noncondemnable shelling and spalling, indicating that tread damage is more prevalent than repair records would indicate.
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Talamini, Brandon, Jeff Gordon, and A. Benjamin Perlman. "Investigation of the Effects of Sliding on Wheel Tread Damage." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-82826.
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Wheel tread spalling is the main source of damage to wheel treads and a primary cause for wheel removals from service. Severe frictional heating of the wheel-rail contact patch during sliding causes the formation of martensite, a hard, brittle microstructure. The martensite patches break away from the more resilient bulk of the wheel tread when subjected to contact loads, resulting in spall formation. Prolonged sliding allows a greater volume of wheel tread material to reach extremely high temperatures, which will lead to material ablation and the formation of a slid flat. Such flats are the cause of wheel impact loads, which are extremely damaging to truck components and rail. This paper outlines an approach developed to estimate the effects of sliding on wheel flat formation and the potential severity of spalling. The methodology is described and preliminary results are presented using an intentionally simplified idealization of the wheel-rail contact geometry. Material characterization (temperature-dependent properties and failure criteria) and management of model size are of equal importance to geometric fidelity and are the focus in the early stages of the development of the qualitative model present here.
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Voltz, Christophe. "Iron Damage and Spalling Behavior below and above Shock Induced α ⇔ ε Phase Transition." In SHOCK COMPRESSION OF CONDENSED MATTER - 2005: Proceedings of the Conference of the American Physical Society Topical Group on Shock Compression of Condensed Matter. AIP, 2006. http://dx.doi.org/10.1063/1.2263413.
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Harris, Tedric A., and Michael N. Kotzalas. "Predicting Micro-Pitting Occurrence in Wind Turbine Gearbox Roller Bearings." In STLE/ASME 2010 International Joint Tribology Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ijtc2010-41136.
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The standard rolling contact fatigue life calculations currently in use by the rolling bearing industry is based on the first occurrence of subsurface-initiated spalling of a raceway or roller surface. However, wind turbine gearbox roller bearings have been suffering from another damage mode, which manifests itself as micro-pitting. The micro-pitting, which is spalling on a micro scale, by itself can be tolerated in its early stages; i.e. the roller bearing will still function properly. As the damaged bearing continues to operate, the micro-pitting propagates and at the later stages, often termed peeling, the pitting becomes deep enough to reach the appearance of traditional subsurface-initiated spalling. To better understand the phenomenon micro-pitting and its causes, this study was conducted to review published literature on the topic as it relates to bearing operation. The key findings were the need for a low specific lubricant film thickness parameter, and some component of sliding velocity in the contacting surface. With this knowledge, a proposed test scheme including these variables could be created from which a method to predict the risk of micro-pitting may be determined.
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French, S. M. "Failure Analysis of a Ruptured Final Reheat Tube." In ASME 2007 Pressure Vessels and Piping Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/pvp2007-26360.
Full textAbstract:
Two damaged final reheat tubes from a 30 year old supercritical unit were submitted to the laboratory for evaluation following the discovering of a failure of one of the tubes after deslagging operations; a third, dented tube was left in service. The 304H stainless steel tubes were installed in 1990 when the reheater was replaced. The bulk microstructure of both tubes shows evidence of sensitization, which is not unusual given this application (reheater). The failed tube appears to be an intergranular separation that started either subsurface or at the ID, propagating to the OD surface. The sensitization of the steel apparently made the material susceptible to corrosion as well as significantly reduced the impact strength of the material to 10–15% of its estimated original level (verified by Charpy impact test). Examination of the dented tube (#101A) showed a subsurface plane of damage some 30 mils from the ID surface, running parallel to the surface. The damage consisted of intergranular separation, caused by the impact loading event, and referred to in the literature as an “attached spalling failure”. Spalling failures occur when the shock wave is reflected from the back surface (the ID surface of the tube), interacting with the incident shock wave as a stress wave. When the magnitude of this tensile stress exceeds the inherent strength of the material, failure occurs. The overall area of the attached spalling failure is being investigated; the concern there is if it is exceptionally large, it may provide a thermal barrier to heat transfer from the OD to the ID and result in a local overheating failure. Within the metallographic sample, however, the damage area was quite small and therefore did not appear to be an immediate issue. The long-term suitability of tube 105A, which remains in service with a dent induced by the same deslagging process that damaged tubes 101A and 103A, is doubtful and should be addressed during the Fall 2006 boiler overhaul. For the shortterm, the assumption was made that cracking due to the deslagging impact would be oriented similar to non-failed tube and extension of these fissures to failure between Spring 2006 and the Fall outage is not expected.
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Cakdi, Sabri, Scott Cummings, and John Punwani. "Heavy Haul Coal Car Wheel Load Environment: Rolling Contact Fatigue Investigation." In 2015 Joint Rail Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/jrc2015-5640.
Full textAbstract:
Railway wheels and rails do not achieve full wear life expectancy due to the combination of wear, plastic deformation, and surface, subsurface, and deep subsurface cracks. Sixty-seven percent of wheel replacement and maintenance in North America is associated with tread damage [1]. Spalling and shelling are the two major types of wheel tread damage observed in railroad operations. Spalling and slid flat defects occur due to skidded or sliding wheels caused by, in general, unreleased brakes. Tread shelling (surface or shallow subsurface fatigue) occurs due to cyclic normal and traction loads that can generate rolling contact fatigue (RCF). Shelling comprises about half of tread damage related wheel replacement and maintenance. The annual problem size associated with wheel tread RCF is estimated to be in the tens of millions of dollars. The total cost includes maintenance, replacement, train delays and fuel consumption. To study the conditions under which RCF damage accumulates, a 36-ton axle load aluminum body coal car was instrumented with a high accuracy instrumented wheelset (IWS), an unmanned data acquisition (UDAC) system, and a GPS receiver. This railcar was sent to coal service between a coal mine and power plant, and traveled approximately 1,300 miles in the fully loaded condition on each trip. Longitudinal, lateral, and vertical wheel-rail forces were recorded continuously during four loaded trips over the same route using the same railcar and instrumentation. The first two trips were conducted with non-steering 3-piece trucks and the last two trips were conducted with passive steering M-976 compliant trucks to allow comparison of the wheel load environment and RCF accumulation between the truck types. RCF initiation predictions were made using “Shakedown Theory” [2]. Conducting two trips with each set of trucks allowed for analysis of the effects of imbalance speed conditions (cant deficiency or excess cant) at some curves on which the operating speeds varied significantly between trips.
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Zhang, Junjing, D. Zhu, and A. D. Hill. "Water-Induced Fracture Conductivity Damage in Shale Formations." In SPE Hydraulic Fracturing Technology Conference. SPE, 2015. http://dx.doi.org/10.2118/spe-173346-ms.
Full textAbstract:
Abstract Shale fracture conductivity can be reduced significantly due to shale-water interactions. Factors that may influence shale fracture conductivity include shale mineralogy, proppant embedment, shale fines migration, proppant fines migration, brine concentration, longer term rock creep, and residual water in the fracture. The study of excessive proppant embedment has been reported in our previous work (Zhang et al. 2014a). This paper presents the studies of the rest of these factors. Laboratory experiments were run to understand each of these factors. To study the effect of rock mineralogy, recovered fracture conductivities after water damage for the Barnett Shale, the Eagle Ford Shale, and Berea Sandstone were measured. During conductivity measurements, water flow directions were switched to study the effect of shale fines migration. The size of shale fines was measured by microscopic imaging techniques, and scanning electron microscopic observations are also presented. Proppant fines migration was examined by placing two colors of sand on each half of the fracture surface and a microscope was used to identify the migrated crushed sands of one color mixed in the other color sand. Fresh water and 2% KCl were injected to study the effect of brine concentration. After water injection, the proppant pack was either fully dried or kept wet to investigate the damage by residual water. Results showed that clay content determines the fracture conductivity damage by water. Fines generated from the shale fracture due to fracture face spalling, slope instability, and clay dispersion can migrate inside the fracture and are responsible for approximately 20% of the conductivity reduction. There is no evidence of crushed proppant particle migration in this study. Longer term rock creep accounts for a 20% reduction of the fracture conductivity. Fresh water does not further damage the fracture conductivity when initial conductivities are above 65 md-ft. Removal of the residual water from the fracture by evaporation helps recover the fracture conductivity to a small extent. A theoretical model of propped fracture conductivity was extended to include the effects of water damage on fracture conductivity. An empirical correlation for the damage effects in the Barnett shale was implemented in this model.
Reports on the topic "Spalling damage"
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Varma, Amit H., Jan Olek, Christopher S. Williams, Tzu-Chun Tseng, Dan Huang, and Tom Bradt. Post-Fire Assessment of Prestressed Concrete Bridges in Indiana. Purdue University, 2021. http://dx.doi.org/10.5703/1288284317290.
Full textAbstract:
This project focused on evaluating the effects of fire-induced damage on concrete bridge elements, including prestressed concrete bridge girders. A series of controlled heating experiments, pool fire tests, material tests, and structural loading tests were conducted. Experimental results indicate that the portion of concrete subjected to temperatures higher than 400°C loses significant amounts of calcium hydroxide (CH). Decomposition of CH increases porosity and causes significant cracking. The portion of concrete exposed to temperatures higher than 400°C should be repaired or replaced. When subjected to ISO-834 standard fire heating, approximately 0.25 in. and 0.75 in. of concrete from the exposed surface are damaged after 40 minutes and 80 minutes of heating, respectively. Prestressed concrete girders exposed to about 50 minutes of hydrocarbon fire undergo superficial concrete material damage with loss of CH and extensive cracking and spalling extending to the depth of 0.75–1.0 in. from the exposed surface. These girders do not undergo significant reduction in flexural strength or shear strength. The reduction in the initial stiffness may be notable due to concrete cracking and spalling. Bridge inspectors can use these findings to infer the extent of material and structural damage to prestressed concrete bridge girders in the event of a fire and develop a post-fire assessment plan.