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1.
《Journal of the European Ceramic Society》2023,43(5):2039-2044
Measuring the thermal shock crack growth process is crucial for revealing ceramic materials and structures’ thermal shock failure mechanisms and evaluating their reliability. We used a self-made water quenching system to conduct thermal shock tests on alumina and zirconia ceramics. The thermal shock process was recorded by high-speed digital image correlation (DIC) during the test. The process of thermal shock crack initiation and propagation in two kinds of ceramics was determined by analyzing the speckle image change on the sample’s surface. It is found that the crack growth rate of alumina is faster than that of zirconia, which is caused by different material parameters. This paper presents an in-situ measurement method for the initiation and propagation of thermal shock cracking in ceramic materials. It can provide a measurement method to identify and predict the thermal shock damage of ceramic components. 相似文献
2.
Xinxin Jin Xinghong Zhang Jiecai Han Ping Hu Lingling Wang 《Journal of the American Ceramic Society》2014,97(3):691-694
A method of introducing a single sharp crack with controllable length and position in brittle materials by thermal shock is proposed. This method is simple to conduct and suitable for the precise testing of critical fracture parameters, with accurate values of fracture toughness of brittle ceramics, such as ZrB2–SiC–graphite (ZSG), able to be obtained. Moreover, this provides an experiment foundation for the study of the relationship between mechanical properties and cracks: The effects of crack length and specimen thickness on the residual strength of ZSG were investigated here. Further comparison between the experimental data and the results of the extended finite‐element calculation was made. Through proper control over the thermal shock, a desired number of uniformly distributed and roughly parallel cracks can be obtained. 相似文献
3.
《Ceramics International》2021,47(22):31433-31441
Zirconia-coated Cr2O3 aggregates synthesized by mixing ZrO2 powders and Cr2O3 aggregates with a phenolic resin binder followed by thermosetting treatment were employed as modified Cr2O3 aggregates to obtain Cr2O3–Al2O3–ZrO2 bricks (high-chromia bricks). The elastic modulus (E) and cold modulus of rupture (CMOR) of these high-chromia bricks before and after thermal shock cycles were systematically investigated, and the residual ratios of CMOR and E were calculated. The thermal shock resistance of the high-chromia bricks was significantly improved by the factor of modification of Cr2O3 aggregates. The mechanism of the improved thermal shock resistance of these high-chromia bricks was studied via microstructure analysis, and the crack propagation behavior was analyzed by scanning electron microscopy (SEM). The fracture work (γWOF), thermal shock damage factor (R′′′′), and thermal stress crack stability parameter (Rst) were measured and calculated using the wedge splitting test (WST). The results indicate that the porous ZrO2 coating layer wrapped the Cr2O3 aggregates, forming modified Cr2O3 aggregates that can increase crack deflection, free path of crack propagation, and fracture work, thus improving the thermal shock resistance of high-chromia bricks. The thermal shock resistance of the fabricated high-chromia bricks was highly correlated with the thickness of the ZrO2 coating layer surrounding the Cr2O3 aggregates. The variation trend of Rst is well consistent with the experimental results, which is suitable to evaluate the thermal shock resistance of high-chromia bricks. 相似文献
4.
Xuan He Peng Song Xiao Yu Chao Li Taihong Huang Ying Zhou Qiaolei Li Kaiyue Lü Jianguo Lü Jiansheng Lu 《Ceramics International》2018,44(17):20798-20807
In this paper, an Al2O3–40?wt%TiO2/NiCoCrAl gradient coating is deposited by atmospheric plasma spraying (APS). The microstructure and element distribution of the coating are studied by scanning electron microscopy (SEM) and electron probe X-ray microanalysis (EPMA). The crack propagation behaviour in the coating under applied and thermal stress is analysed through a three-point bending test and a thermal shock test, respectively. Two rapid propagation processes of the cracks can be found during the three-point bending test, which lead to two peaks in the load-displacement curves of the gradient coating. The gradual change in the composition also has an effect on the crack propagation process within the coating. Non-directional propagation paths of cracks and the formation of oxides can be observed in the gradient region under the effect of thermal stress, which lead to the spallation failure of the coating. 相似文献
5.
In this work, a non-local failure model was proposed and implemented into a finite element code. It was then used to simulate the crack evolution in ceramic materials subjected to thermal shock. By using this numerical model, the initiation and propagation of cracks in water quenched ceramic specimens were simulated. The numerical simulations reproduced faithfully the crack patterns in ceramic specimens underwent quenching tests. The periodical and hierarchical characteristics of the crack patterns were accurately predicted. The numerical simulations allow a direct observation on whole the process of crack initiation and growth, which is quite a difficult task in experimental studies. The failure mechanisms and the fracture procedure are discussed according to the numerical results obtained from the simulations. It is shown that the numerical model is simple, robust, accurate and efficient in simulating crack evolution in real structures under thermal shock. 相似文献
6.
《Ceramics International》2022,48(20):30086-30092
Thermal shock resistance is critical to ensure the service safety of ceramic hot-end components. The thermal shock performance of stereolithographic additive-manufactured ceramics has not yet been studied. In this study, a series of thermal shock experiments with various temperature differences was conducted on stereolithographic additive-manufactured Al2O3 ceramics. The surface cracks were analysed based on photographs captured before and after the thermal shock experiments. Three-point bending tests with in situ X-ray digital radiography were conducted to determine the thermal shock resistance. Crack initiation, propagation, and coalescence were observed under flexural loads. The critical temperature difference of the stereolithographic additive-manufactured Al2O3 ceramics was determined to be 267.22 °C. The crack length increased and residual strength decreased with increasing temperature differences. The layered structure of the stereolithographic additive-manufactured ceramics slowed crack propagation. We expect that this study will serve as a reference for the performance of stereolithographic additive-manufactured Al2O3 ceramics in extreme environments. 相似文献
7.
Renaud Grasset-Bourdel Arnaud Alzina Marc Huger Thierry Chotard Robert Emler Dietmar Gruber Harald Harmuth 《Journal of the European Ceramic Society》2013,33(5):913-923
In some industrial applications, the need to improve the thermal shock resistance of refractories by optimisation of their microstructural design is of major importance. Refractories with enhanced thermal shock resistance usually present a rather low resistance to crack initiation but high resistance to crack propagation (rising R-curves), as well as a mechanical behaviour deviating from pure linear elastic fracture mechanics (LEFM), often qualified as nonlinear. The present work aimed at studying the influence of thermal micro-damage within the microstructure released during the cooling process on the nonlinearity of the mechanical behaviour in tension. The two-phase composites considered were magnesia-spinel refractories with different spinel inclusions content allowing to modulate the micro-damage level. Two different destructive mechanical tests, namely tensile and wedge splitting tests, were performed and their results were compared. The influence of thermal damage on different relevant mechanical parameters was investigated, and a quantitative correlation analysis between these parameters was proposed. 相似文献
8.
《Ceramics International》2016,42(12):13525-13534
Cordierite-mullite-corundum composite ceramics for solar heat transmission pipeline were fabricated via pressureless sintering at a low sintering temperature with added Sm2O3. The effects of Sm2O3 on sintering behaviors, mechanical property, phase transformation, microstructure, thermal shock resistance and thermal conductivity of the composite ceramics were investigated. TEM analysis results demonstrated that Sm3+ located in glass and grain boundaries to facilitate the densification via the liquid-phase sintering mechanism and improve bending strength by grain refinement, respectively. Proper addition (3 wt%) of Sm2O3 could promote the crystallization of cordierite, and improve thermal shock resistance of the composite ceramics with an increasing rate of 16.70% for bending strength after 30 thermal shock cycles (air cooling from 1100 °C to RT). The composite ceramics possessed a superior thermal shock resistance, where a large amount of particles were formed to suppress crack initiation and propagation during thermal shock. Cordierite-mullite-corundum composite ceramics with proper Sm2O3 addition (3 wt%) had a lower thermal conductivity than that of composite ceramics without Sm2O3 addition by strengthening the scattering of phonon, which could reduce the heat loss during solar heat transmission process. 相似文献
9.
D.N. Boccaccini M. Cannio T.D. Volkov-Husovi I. Dlouhy M. Romagnoli P. Veronesi C. Leonelli 《Journal of the European Ceramic Society》2008,28(10):1941-1951
Viscoelastic bridges can be formed in refractory ceramics while cooling from high temperatures. Such bridges can shield crack tips, thus reducing the effective crack tip stress intensity factors leading to higher resistance to creep and thermal shock. The extent to which the crack tip stress intensity is reduced can be estimated from fracture mechanics models that include experimental measurement of crack bridging and microstructural parameters. In this paper a novel approach is proposed for the assessment of the effective crack bridging toughening from combining destructive and non-destructive test methods. Fracture toughness values were determined applying chevron notched specimen technique and surface damage of the specimen was monitored by image analysis. Different cordierite–mullite compositions characterized by different microstructure morphologies and crack propagation behaviour were investigated. A brief discussion about the correlation between thermo-mechanical properties, microstructure, crack propagation behaviour and thermal shock resistance is presented. Moreover, an empirical model able to determine the presence and effectiveness of the viscoelastic crack bridging ligaments acting in the microstructure under thermal shock conditions and their degradation with increasing thermal shock cycles from parameters measured at room temperature is presented. 相似文献
10.
Wenjiu Duan Dechang Jia Delong Cai Bo Niu Hualong Yang Zhihua Yang Yu Zhou 《Ceramics International》2021,47(14):19737-19742
The high-temperature service performance of nearly fully dense 20 wt% BNW/SiO2 ceramic was systematically investigated. The oxidation damage and strength degradation of the whiskers combined with the surface microstructures of the samples predominantly influence the flexural strength from RT to 1000 °C. In previous work, the temperature dependence of the material properties is invariably ignored when evaluating thermal stress crack initiation and propagation behaviour. In this work, modified thermal shock models that include temperature-dependent material properties were established based on thermal-shock fracture (TSF) theory and thermal-shock damage (TSD) theory. Then, the thermal shock resistance (TSR) of the BNW/SiO2 ceramic was evaluated by preforming a water quenching test. The modified models could better explain the TSR behaviour of the ceramic, indicating that considering the temperature-dependent material properties will reveal the thermal shock damage mechanism more precisely. 相似文献
11.
Fei Qi Songhe Meng Fan Song Hao Guo Xianghong Xu Yingfeng Shao Yao Chen 《Journal of the American Ceramic Society》2019,102(6):3641-3652
This work utilized a combination of experimental evidence and fractal geometric method to assess the effect of crack extension concerning the thermal shock on residual strength of ceramics. Sintered alumina (Al2O3) ceramic slabs were bundled and quenched in water under different thermal shock temperatures. The fractal dimension of thermal shock crack patterns on the interior surface and the cooled surface was calculated by the Box-counting method. Fracture energy of a fractal pattern of microcracks in quasi-brittle solids was employed to explain the relationship between crack length and fractal dimensions. The results show that if the crack propagation has the same crack length but a larger fractal dimension, it will absorb more fracture energy. The thermal shock crack patterns of Al2O3 ceramics with different grain sizes were analyzed, and the smaller grain size ceramic had a higher fractal dimension of crack patterns than the larger one. 相似文献
12.
Hao Cheng Fen Ye Jun Chang Sizhan Wu 《International Journal of Applied Ceramic Technology》2019,16(2):772-780
Cordierite-mullite composite ceramic was synthesized in situ by semidry pressing and pressureless sintering from andalusite, kaolin, γ-Al2O3, talc, potassium feldspar, and albite in air. The effects of composition and sintering temperature on the density, bending strength, thermal shock stability, crystal phases, and microstructure of the specimens were studied. The results show that specimen B2 (the theoretical content of cordierite was 20 wt%) has excellent performance, that is, a bending strength of 104.59 MPa, 30 cycles of thermal shock resistance without cracking, and a loss rate of 13.12%. X-ray diffractometer (XRD) analysis and scanning electron microscope (SEM) micrographs showed that spherical cordierite crystals were grown on the surface of the mullite, therefore, the specimen possessed a superior bending strength and thermal shock resistance, where a great number of granules combined to restrain crack initiation as well as propagation over time during the thermal shock test. The thermal conductivity of specimen B2 was determined to be 3.83 W/(m·K) (36°C), and the sensible heat storage density was 1136 kJ/kg, with the temperature difference (ΔT) ranging from 0 to 800°C. Consequently, the cordierite-mullite composite is a potentially applicable material for solar thermal storage. 相似文献
13.
Thermal shock resistance of tri‐layer Yb2SiO5/Yb2Si2O7/Si coating for SiC and SiC‐matrix composites
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Xin Zhong Yaran Niu Hong Li Haijun Zhou Shaoming Dong Xuebin Zheng Chuanxian Ding Jinliang Sun 《Journal of the American Ceramic Society》2018,101(10):4743-4752
A new tri‐layer Yb2SiO5/Yb2Si2O7/Si coating was fabricated on SiC, C/SiC, and SiC/SiC substrates, respectively, using atmospheric plasma spray (APS) technique. All coated samples were subjected to thermal shock test at 1350°C. The evolution of phase composition and microstructure and thermo‐mechanical properties of those samples before and after thermal shock test were characterized. Results showed that adhesion between all the 3 layers and substrates appeared good. After thermal shock tests, through microcracks which penetrated the Yb2SiO5 top layer were mostly halted at the Yb2SiO5‐Yb2Si2O7 interface and no thermal growth oxide (TGO) was formed after 40‐50 quenching cycles, implying the excellent crack propagation resistance of the environmental barrier coating (EBC) system. Transmission electron microscopy analysis confirmed that twinnings and dislocations were the main mechanisms of plastic deformation of the Yb2Si2O7 coating, which might have positive effects on crack propagation resistance. The thermal shock behaviors were clarified based on thermal stresses combined with thermal expansion behaviors and elastic modulus analysis. This study provides a strategy for designing EBC systems with excellent crack propagation resistance. 相似文献
14.
Yingfeng Shao Boyang Liu Xiaohuan Wang Long Li Jiachen Wei Fan Song 《Journal of the European Ceramic Society》2018,38(7):2879-2885
The effects of water quenching temperature and specimen size on the propagation speed of thermal shock crack are investigated in real time by water quenching of translucent ceramic and high-speed imaging. The results show that the crack growth rate increases with the increase of quenching temperature difference or specimen size. Within 100?ms, average crack speed is 20.3?mm/s at a temperature difference of 400?°C in 20?mm wide ceramic and is 11.9?mm/s at a temperature difference of 220?°C in 5?mm wide ceramic, respectively. Compare with specimen size, the influence of quenching temperature difference on the crack propagation speed is larger. The calculations based on meso-damage mechanics have similar results to those of experiments. This paper quantitatively studies the thermal-shock crack growth of ceramic in real time and expands the scientific understanding of thermal shock cracking phenomenon of ceramic. 相似文献
15.
Bruno A. Latella 《Carbon》2006,44(14):3043-3048
Thermal shock resistance of a commercial grade of graphite was studied using an arc-discharge test. The thermal shock fracture initiation and crack propagation behaviour of the graphite disks at different input power levels were determined and analysed using fracture mechanics. The temperature gradient was measured experimentally and the profiles were force fitted with an even fourth-order polynomial. The thermal stresses were calculated from the force fits. A radial notch was introduced to the disk specimens to enable calculation of the thermal stress intensity factors. The crack mouth opening displacement was monitored using a special displacement transducer. The thermal stress and stress intensity factors were found to increase with increasing input current (and hence increasing thermal gradient). The thermal shock fracture toughness determined using the arc-discharge technique was found to increase from 0.8 to 1.4 MPa m1/2 at temperatures from 220 to 420 °C. The longer the notch length, the shorter the time to crack, the smaller the crack mouth opening displacement jump and the shorter the unstable crack growth. 相似文献
16.
《Ceramics International》2017,43(9):7177-7183
The mechanical and thermo-mechanical properties of MgO-C refractories are of major importance in the industrial applications, and highly depend on the optimization of their microstructural design. In the present work, the influence of flaky graphite content on mechanical behavior and thermal shock resistance of such refractories was investigated with the aid of the wedge splitting test, fractal and microscopic fractographic analysis. The results showed that the increase of graphite content in the specimens led to an enhanced non-linear fracture behavior, a reduced nominal notch tensile strength (σNT), and a higher specific fracture energy (Gf), characteristic length (lch) and thermal shock resistance parameter (Rst). The fractal analysis of the crack propagation path of the specimens after the wedge splitting test indicated that increasing graphite content in the refractories can enhance their irregularity of the crack propagation path during fracture. Also, it was suggested from microscopic fractographic analysis that the improvement of thermal shock resistance of MgO-C refractories was positively correlated with the increase of interface crack propagation. 相似文献
17.
Aluminum oxynitride (AlON) has been considered as a potential ceramic material for high-performance structural and advanced refractory applications owing to its excellent stability and mechanical properties such as high rigidity and good chemical stability. Thermal shock resistance is a major concern and an important performance index of refractories and high-temperature ceramics. While zirconium nitride (ZrN) particles have been proven to improve mechanical properties of AlON ceramic, the thermal shock behavior has not been evaluated yet. The aim of this investigation was to identify the thermal shock resistance and underlying mechanisms of hot-pressed 2.7% ZrN–AlON composites by a water-quenching technique over a temperature range between 225 °C and 275 °C. The residual strength and Young's modulus after thermal shock decreased with increasing temperature range and thermal shock times due to large temperature gradients and thermal stresses caused by abrupt water-quenching. The presence of nano-sized ZrN particles exhibited a positive effect on the improvement of both residual strength and critical temperature difference of AlON ceramic due to the toughening effects, the higher thermal conductivity of ZrN, the refined grain size and the reduction of porosity. Different toughening mechanisms including crack deflection, crack bridging and crack branching were observed during thermal shock experiments, thus effectively enhancing the crack initiation and propagation resistance and leading to a considerable improvement in thermal shock resistance in the ZrN–AlON composites. 相似文献
18.
《Journal of the European Ceramic Society》2023,43(8):3172-3181
Ceramic matrix composites (CMCs) are commonly used for high temperature components in aircrafts. However, thermal shock, as a typical loading case, will cause high thermal stresses in CMCs resulting in brittle fracture failure, and material cracking caused by thermal shock can further reduce the effectiveness of thermal protection function. In the present paper, we propose a bionic hierarchical fiber preform design method to improve the thermal shock resistance of ceramics. The effect of architectures of fiber preforms of continuous carbon fiber-reinforced CMCs on the thermal shock resistance was investigated to understand its importance and the related mechanical mechanisms. Thermal shock (cycling) tests were performed with continuous carbon fibers reinforced SiCN ceramic matrix composites (Cf/SiCN) prepared by PIP. 3D micro-CT scan and three-point bending tests were also conducted to evaluated the resultant damage. The results showed that smaller internal damage and higher thermal shock resistance can be obtained in comparison to pure SiCN ceramics, and the underlying mechanism can be explained by the fact that smaller pitch angle can resist the through-thickness crack propagation via promoting diffused in-plane damage. The present study offers a possibility in developing biomimetic Cf/SiCN ceramics with excellent thermal shock behavior. 相似文献
19.
《Ceramics International》2020,46(6):7178-7186
The scalelike coatings with MoSi2 as emittance agent, flake fused quartz as coarse fillers, silica sol as dispersive medium of coating slurry, were prepared on rigid mullite fibrous ceramics to avoid fatal radial cracks and improve thermal shock resistance via combining slurry method with sol-gel method. And the particle size distribution of fused silica was changed to get different crack structure in scalelike coatings. Microstructure and phase composition of the coatings with different crack structure were investigated comprehensively. Contact damage resistance, thermal shock resistance and infrared radiating property were also studied. The results showed that only the coatings with mixing large and small particles of fused silica as coarse fillers could form crack network. The scalelike coatings with crack network went through 25 thermal cycles between 1500 °C and room temperature without peeling and spalling, and the bonding strength did not decrease after test. The scalelike structure with crack network also avoided radial cracks and exhibited some softness and less stiffness in Hertzian indentation test. The emissivity of coatings with different crack structure were all higher than 0.85; and the coatings with lower proportion of crack areas had higher emissivity. 相似文献
20.
Peng Zhou Zhi Wang Youhua Fan Ping Hu Xinghong Zhang Wenbo Han 《Journal of the American Ceramic Society》2015,98(9):2866-2872
In this work, the thermal shock behavior of laminated ZrB2–SiC ceramic has been evaluated using indentation‐quench method based on propagation of Vickers cracks and compared with the monolithic ZrB2–SiC ceramic. The results showed that the laminated ZrB2–SiC ceramic exhibited better resistance to crack propagation and thermal shock under water quenching condition, and the critical temperature difference (ΔTc) of laminated ZrB2–SiC ceramic (ΔTc ≈ 590°C) was much higher than that of monolithic ceramic (ΔTc ≈ 290°C). The significant improvement in thermal shock resistance was attributed to residual stresses enhancing the resistance to crack growth during thermal shock loading. 相似文献