Journal articles: 'Fracture mechanics of ceramics'

1

Suo, Z., C. M. Kuo, D. M. Barnett, and J. R. Willis. "Fracture mechanics for piezoelectric ceramics." Journal of the Mechanics and Physics of Solids 40, no. 4 (May 1992): 739–65. http://dx.doi.org/10.1016/0022-5096(92)90002-j.

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Fan, Cheng. "Fracture Mechanics Analysis of GI All-Ceramic Crowns." Advanced Materials Research 750-752 (August 2013): 529–32. http://dx.doi.org/10.4028/www.scientific.net/amr.750-752.529.

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Dental ceramic materials have approximate color and translucency with natural tooth, which is unmatched by other restorative materials. Because of its beautiful appearance, good physical and chemical properties, all-ceramic crown restorations are more widely used., However, due to the brittleness of ceramics and the stress mismatch between different materials, dropping or fracture phenomenon of porcelain veneer is often occurred in clinical application during the service period of all-ceramic crowns. The porcelain veneer failure mechanism is still not very clear, in this paper, the force performance of all-ceramic crowns is analyzed using the RFPA (realistic failure process analysis) system. The crack initiation, propagation and failure process of all-ceramic crown can be clearly observed and the research results provide guidance for clinical application

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Kobayashi, Albert S. "Dynamic fracture of ceramics and ceramic composites." Materials Science and Engineering: A 143, no. 1-2 (September 1991): 111–17. http://dx.doi.org/10.1016/0921-5093(91)90730-b.

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Duffy, J., S. Suresh, K. Cho, and E. R. Bopp. "A Method for Dynamic Fracture Initiation Testing of Ceramics." Journal of Engineering Materials and Technology 110, no. 4 (October 1, 1988): 325–31. http://dx.doi.org/10.1115/1.3226057.

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An experimental method is described whereby the dynamic fracture initiation toughness of ceramics and ceramic composites can be measured in pure tension or pure torsion at stress intensity factor rates of 105 to 106 MPam/s. In this procedure, circumferentially notched cylindrical rods are subjected to uniaxial cyclic compression at room temperature to introduce a self-arresting, concentric Mode I fatigue pre-crack, following the technique presented by Suresh et al. (1987) and Suresh and Tschegg (1987). Subsequently, dynamic fracture initiation is effected by stress wave loading with a sharp-fronted pulse which subjects the specimen to a dynamic load inducing either Mode I or Mode III fracture. Instrumentation appropriate to the loading mode provides a record of average stress at the fracture site as a function of time. The capability of this method to yield highly reproducible dynamic fracture initiation toughness values for ceramics is demonstrated with the aid of experiments conducted on a polycrystalline aluminum oxide. The dynamic fracture toughness values are compared with the results obtained for quasi-static Mode I and Mode III fracture in the ceramic material at stress intensity factor rates of 10−1 to 1 MPam/s. Guidelines for the dynamic fracture initiation testing of ceramics and ceramic composites are discussed.

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Zhang, Chunguo, and Shuangge Yang. "Probabilistic Prediction of Strength and Fracture Toughness Scatters for Ceramics Using Normal Distribution." Materials 12, no. 5 (March 2, 2019): 727. http://dx.doi.org/10.3390/ma12050727.

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Tensile strength ft and fracture toughness KIC of ceramic are not deterministic properties or fixed values, but fluctuate within certain ranges. A nonlinear elastic fracture mechanics model was developed in this study and combined with the common normal distribution to predict ceramic’s ft and KIC with consideration of their scatters in a statistical sense. In the model, the relative characteristic crack size a*ch/G (characteristic crack size a*ch, average grain size G) was determined based on the fracture measurements on five types of ceramics with different G from 2 to 20 μm in the reference (Usami S, et al., Eng. Fract Mech. 1986, 23, 745). The combined application of the model and normal distribution has two functions: (i) probabilistic ft and KIC can be derived from seemingly randomly varied fracture tests on small ceramic specimens containing different initial defects/cracks, and (ii) with ft or KIC values (corresponding mean and standard deviation), fracture strength of heterogeneous samples with and without cracks can be predicted by considering scatter described by specified reliability. For the fine ceramics, the predicted results containing the mean and the upper and lower bounds with 96% reliability gained with the model, match very well with the experimental results (a, σN).

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Bermejo, Raúl, Luca Ceseracciu, Luis Llanes, and Marc Anglada. "Fracture of Layered Ceramics." Key Engineering Materials 409 (March 2009): 94–106. http://dx.doi.org/10.4028/www.scientific.net/kem.409.94.

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Layered ceramics are foreseen as possible substitutes for monolithic ceramics due to their attractive mechanical properties in terms of strength reliability and toughness. The different loading conditions to which ceramic materials may be subjected in service encourage the design of tailored layered structures as function of their application. The use of residual stresses generated during cooling due to the different thermal strain of adjacent layers has been the keystone for the improvement of the fracture response of many layered ceramic systems, e.g. alumina-zirconia, alumina-mullite, silicon nitride-titanium nitride, etc. In this work, the fracture features of layered ceramics are addressed analysing two multilayered structures, based on the alumina-zirconia system, designed with tailored compressive residual stresses either in the external or internal layers. Contact strength and indentation strength tests have been performed to investigate the response of both designs to crack propagation. The experimental findings show a different response in terms of strength and crack growth resistance of both designs. While layered structures with compressive stresses at the surface provide a better response against contact damage compared to monoliths, a flaw tolerant design in terms of strength and an improved toughness through energy release mechanisms is achieved with internal compressive stresses. The use of layered architectures for automotive or biomedical applications as substitutes for alumina-based ceramics should be regarded in the near future, where reliable ceramic designs are needed.

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Bona, A. Della, K. J. Anusavice, and J. J. Mecholsky. "Apparent Interfacial Fracture Toughness of Resin/Ceramic Systems." Journal of Dental Research 85, no. 11 (November 2006): 1037–41. http://dx.doi.org/10.1177/154405910608501112.

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We suggest that the apparent interfacial fracture toughness (KA) may be estimated by fracture mechanics and fractography. This study tested the hypothesis that the KA of the adhesion zone of resin/ceramic systems is affected by the ceramic microstructure. Lithia disilicate-based (Empress2-E2) and leucite-based (Empress-E1) ceramics were surface-treated with hydrofluoric acid (HF) and/or silane (S), followed by an adhesive resin. Microtensile test specimens (n = 30; area of 1 ± 0.01 mm2) were indented (9.8 N) at the interface and loaded to failure in tension. We used tensile strength (σ) and the critical crack size (c) to calculate KA (KA = Yσc1/2) (Y = 1.65). ANOVA and Weibull analyses were used for statistical analyses. Mean KA (MPa·m1/2) values were: (E1HF) 0.26 ± 0.06; (E1S) 0.23 ± 0.06; (E1HFS) 0.30 ± 0.06; (E2HF) 0.31 ± 0.06; (E2S) 0.13 ± 0.05; and (E2HFS) 0.41 ± 0.07. All fractures originated from indentation sites. Estimation of interfacial toughness was feasible by fracture mechanics and fractography. The KA for the systems tested was affected by the ceramic microstructure and surface treatment.

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Nasrin, S., N. Katsube, R. R. Seghi, and S. I. Rokhlin. "Survival Predictions of Ceramic Crowns Using Statistical Fracture Mechanics." Journal of Dental Research 96, no. 5 (January 20, 2017): 509–15. http://dx.doi.org/10.1177/0022034516688444.

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This work establishes a survival probability methodology for interface-initiated fatigue failures of monolithic ceramic crowns under simulated masticatory loading. A complete 3-dimensional (3D) finite element analysis model of a minimally reduced molar crown was developed using commercially available hardware and software. Estimates of material surface flaw distributions and fatigue parameters for 3 reinforced glass-ceramics (fluormica [FM], leucite [LR], and lithium disilicate [LD]) and a dense sintered yttrium-stabilized zirconia (YZ) were obtained from the literature and incorporated into the model. Utilizing the proposed fracture mechanics–based model, crown survival probability as a function of loading cycles was obtained from simulations performed on the 4 ceramic materials utilizing identical crown geometries and loading conditions. The weaker ceramic materials (FM and LR) resulted in lower survival rates than the more recently developed higher-strength ceramic materials (LD and YZ). The simulated 10-y survival rate of crowns fabricated from YZ was only slightly better than those fabricated from LD. In addition, 2 of the model crown systems (FM and LD) were expanded to determine regional-dependent failure probabilities. This analysis predicted that the LD-based crowns were more likely to fail from fractures initiating from margin areas, whereas the FM-based crowns showed a slightly higher probability of failure from fractures initiating from the occlusal table below the contact areas. These 2 predicted fracture initiation locations have some agreement with reported fractographic analyses of failed crowns. In this model, we considered the maximum tensile stress tangential to the interfacial surface, as opposed to the more universally reported maximum principal stress, because it more directly impacts crack propagation. While the accuracy of these predictions needs to be experimentally verified, the model can provide a fundamental understanding of the importance that pre-existing flaws at the intaglio surface have on fatigue failures.

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Gogotsi, G. A., V. I. Galenko, B. I. Ozerskii, and T. A. Khristevich. "Fracture Resistance of Ceramics: Edge Fracture Method." Strength of Materials 37, no. 5 (September 2005): 499–505. http://dx.doi.org/10.1007/s11223-005-0060-8.

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Danzer, Robert. "Fracture Mechanics of Ceramics - A Short Introduction." Key Engineering Materials 333 (March 2007): 77–86. http://dx.doi.org/10.4028/www.scientific.net/kem.333.77.

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Zhang, Tao, Hai Yun Jin, Yong Ian Wang, and Zhi Hao Jin. "The Mechanical Properties of AlN/BN Laminated Ceramic Composites." Materials Science Forum 569 (January 2008): 97–100. http://dx.doi.org/10.4028/www.scientific.net/msf.569.97.

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AlN/BN laminated ceramic composites were fabricated using tape-casting and hot-pressing by optimizing the designs of the structure and geometry of AlN/BN laminated ceramic composites. The results showed that the fracture toughness and bending strength for AlN/BN laminated ceramics reached 9.1MPa.m1/2 and 378MPa respectively. The fracture toughness is two times higher than that of AlN monolithic ceramics. The excellent fracture toughness of AlN/BN laminated ceramics could be mainly attributed to crack deflection, delaminating, branching, parallel propagation and crack laminate pilling out at the AlN/BN weak interface.

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12

Jun, Liu, Liu Su, Chen Zhigang, Zhou Fei, and Chang Min Suh. "Effect of Y-TZP on Mechanical Properties of Al2O3-TiB2 Ceramics." International Journal of Modern Physics B 17, no. 08n09 (April 10, 2003): 1279–84. http://dx.doi.org/10.1142/s0217979203018879.

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The effect of Y-TZP additive on the mechanical properties of Al2O3-TiB2 ceramics was investigated. The results indicate that Y-TZP additive can enhance the flexure strength and fracture toughness of Al2O3-TiB2 ceramics, but has little effect on their hardness. The maximum bending strength of Al2O3-TiB2 and Al2O3-TiB2-Y-TZP ceramics are at 20vol% TiB2 content. The maximum fracture toughness for two kinds of ceramics all are at 30vol% TiB2 content. The bending strength and fracture toughness as well as impact resistance of Al2O3-TiB2-Y-TZP ceramics are higher than those of Al2O3-TiB2 ceramics. The cutting behaviors of two kinds of ceramics are satisfactory. When the ceramic cutting tools are applied to continuous cutting, the wear resistance of cutting tools increases as an increase in TiB2 content. But when they are applied to intermittent cutting, the serving life of ceramic cutting tools is mainly governed by their fracture toughness, The mainly failure mechanism of intermittent cutting is micro-chipping.

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13

Shetty, D. K. "Mixed-Mode Fracture Criteria for Reliability Analysis and Design With Structural Ceramics." Journal of Engineering for Gas Turbines and Power 109, no. 3 (July 1, 1987): 282–89. http://dx.doi.org/10.1115/1.3240037.

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Increasing use of ceramics in structural applications has led to the development of a probabilistic design methodology that combines three elements: linear elastic fracture mechanics theory that relates strengths of ceramics to size, shape, and orientation of critical flaws, a characteristic flaw size distribution function that accounts for the size effect on strength via the weakest-link concept, and a time-dependent strength caused by subcritical crack growth or other mechanisms. This paper reviews recent research that has been focused on the first of the above three elements, the investigation of fracture criteria for arbitrarily oriented flaws in ceramics, i.e., the mixed-mode fracture problem in linear elastic fracture mechanics theory. Experimental results obtained with two-dimensional through cracks and three-dimensional surface (indentation) cracks are summarized and compared to mixed-mode fracture criteria. The effects of material microstructure and the stress state on mixed-mode fractures are discussed. The application of mixed-mode fracture criteria in reliability analysis is illustrated for several simple stress states in the absence of time-dependent strength degradation.

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Zhao, Bo, X. H. Zhang, C. S. Liu, Feng Jiao, and Xun Sheng Zhu. "Study on Ultrasonic Vibration Grinding Character of Nano ZrO₂ Ceramics." Key Engineering Materials 291-292 (August 2005): 45–50. http://dx.doi.org/10.4028/www.scientific.net/kem.291-292.45.

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Nano ceramics possessed ascendant mechanical property and physical characteristics contrast with engineering ceramics, so it has extensive application prospect in various industries. On the basis of applying the indentation fracture mechanics to analyze the removal mechanics of ceramic material, this paper analyzed the critical ductile grinding depth of the nano ZrO2 ceramics. Adopting ultrasonic composite processing we describe the influence of different processing parameters and grain size of diamond wheel on the grinding forces and surface roughness. Based on the grinding forces and surface roughness the grinding process with and without vibration is analyzed. By means of SEM and AFM the surface character and critical ductile grinding depth of nano ZrO2 ceramics are also discussed. The paper supplied the theoretical and experimental basis for the grinding of the large-sized ultraprecision plate structure of nano ZrO2 ceramics (nm).

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Hang, Xiao Cong, and Yun Kai Li. "Influence of Confinement on Ceramic’s Mechanical Properties." Materials Science Forum 848 (March 2016): 249–55. http://dx.doi.org/10.4028/www.scientific.net/msf.848.249.

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The wide use of ceramic material in engineering is restricted by its brittleness, so the strengthening and toughening of ceramics is always a hot spot of research in material area. And in general, the modification of ceramics is achieved by changing its internal microstructure. In this paper the influence of confinement on the mechanical properties of ceramics and the specific use of this method were investigated. Firstly, the influence of confinement on ceramic’s fracture process was analyzed in theory. Then the three-point bending test was conducted using two types of ceramics, viz. Zirconia and Alumina. The experimental results showed that the fracturing load of zirconia increased from 4.3298 to 5.4639KN as the confinement was increased from 0 to 150MPa, 26.19% increase was found in the confined specimen. The same trend was observed in alumina, whose fracturing load increased from 3.0446 to 5.0259KN as the confinement was increased from 0 to 150MPa, 65.07% increase was found. After that, a series of ballistic experiments were performed. The target in this experiment was boron carbide ceramic, and it was confined by 45 steel. The results showed that with the constraint force was bigger, the ballistic efficiency factor was better and the depth of penetration was smaller. In other words, the confinement can increase the defensible performance of the target. In summary, the ceramic’s fracture toughness, defensible performance and ballistic efficiency factor can be increased by adding confinement to it.

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Mishima, Tadao, Yukio Nanayama, Yukio Hirose, and Keisuke Tanaka. "X-Ray Fractography of Fracture Surface of Alumina Ceramics." Advances in X-ray Analysis 30 (1986): 545–52. http://dx.doi.org/10.1154/s0376030800021716.

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X-ray diffraction observation of fracture surface yields useful information to analyze the cause of failure accidents of engineering structures. This experimental technique, named X-ray fractography, has been developed especially in Japan. The relationship between X-ray parameters and fracture mechanics parameters plays a key role in determinating the mechanical condition of fracture.

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Porojan, Liliana, Sorin Porojan, Lucian Rusu, Adrian Boloș, Cristina Savencu, Aurora Antoniac, and Sebastian Gradinaru. "Experimental Evaluation of Fracture Pattern in Bilayered All-Ceramic Molar Crowns." Defect and Diffusion Forum 376 (July 2017): 101–10. http://dx.doi.org/10.4028/www.scientific.net/ddf.376.101.

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Due to the lower opacity and translucency of many core materials, bilayered ceramic crowns were introduced to obtain sufficient veneer support and to improve aesthetics. Interfaces can have significant influence on the mechanical performance of layered structures. Veneer chipping and zirconia frameworks fractures are critical issues in all-ceramic restorations. The objective of this study was to assess failure analysis of bilayered all-ceramic molar crowns, evidenced by different type of fractures. Experiments were conducted on a right first maxillary molar. Bilayered all-ceramic crowns were obtained with a 0.5 mm thick zirconia milled framework and veneered with hot-pressed ceramics. The specimens were tested at compressive load until failure. The typical macroscopic crack pattern of all samples showed that crack propagation resulted in more broken pieces with sharp edges. Ceramic materials show considerable variation in strength due to their extreme sensitivity to cracks. Understanding the fracture behavior of dental ceramics and its relation to different materials and restorations is important from a clinical point of view.

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Singh, R. K., K. Jagannadham, and J. Narayan. "Laser surface modification of metal-coated ceramics." Journal of Materials Research 3, no. 6 (December 1988): 1119–26. http://dx.doi.org/10.1557/jmr.1988.1119.

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Pulsed excimer laser radiation has been successfully employed in the improvement (> 50%) of fracture strength of metal-coated ceramics. Thin metallic layers (∼500 Å) of nickel were deposited on silicon nitride and silicon carbide substrates and further irradiated with pulsed excimer (xenon chloride, krypton fluoride) laser pulses. The laser energy density was varied from 0.4 to 2.0 J cm −2 to optimize the formation of mixed interfacial layers. The formation of interfacial layers was studied by transmission electron microscopy and Rutherford backscattering spectrometry techniques. Detailed heat flow calculations using implicit finite difference methods were performed to simulate the effects of intense laser irradiation on metal-coated ceramic structures. Three different mechanisms were found to play an important role in the improvement in the fracture strength of these ceramics. Theoretical calculations showed that the displacement of the crack tip away from the free surface by laser surface modification can lead to a 100% improvement in the fracture strength of the ceramic.

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Clarke, D. R., and B. Schwartz. "Transformation toughening of glass ceramics." Journal of Materials Research 2, no. 6 (December 1987): 801–4. http://dx.doi.org/10.1557/jmr.1987.0801.

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The utilization of transformation toughening has hitherto been restricted to increasing the fracture resistance of polycrystalline ceramic materials. Although a number of investigators have attempted to extend the concept to toughening glasses and glass ceramics with tetragonal zirconia, no successful reports have been published. It is argued that the approaches employed are inevitably limited primarily because they do not take into account the necessity of nucleating the tetragonal-to-monoclinic transformation away from the crack tip itself. By concentrating on the nucleation event and using standard ceramic processing techniques, it has been demonstated that transformation toughening can be used to increase the toughness of glass-ceramic materials, and this approach is illustrated by increasing the fracture toughness of a cordierite glass ceramic.

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Malkin, S., and J. E. Ritter. "Grinding Mechanisms and Strength Degradation for Ceramics." Journal of Engineering for Industry 111, no. 2 (May 1, 1989): 167–74. http://dx.doi.org/10.1115/1.3188746.

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This paper presents a critical review and evaluation of our fundamental knowledge of the grinding mechanisms for ceramic materials and their influence on the finished surface and mechanical properties. Two main research approaches are identified: a “machining” approach and an “indentation fracture mechanics” approach. The machining approach has typically involved measurement of the grinding forces and specific energy coupled with microscopic observations of the surface morphology and grinding detritus. Any proposed mechanisms of abrasive-workpiece interaction must be consistent with the magnitude of the specific energy and its dependence on the grinding conditions. The “indentation fracture mechanics” approach assumes that the damage produced by grinding can be modeled by the idealized flaw system produced by a sharp indentor. Indentation of a ceramic body is considered to involve elastic/plastic deformation with two principal crack systems propagating from the indentation site: lateral cracks which lead to material removal and radial/median cracks which cause strength degradation. Each of these approaches provides important insight into grinding behavior and strength degradation, but each has its shortcomings. Further efforts to develop a fundamental model for grinding of ceramics would benefit from the integration of both of these approaches.

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Zhou, You, Kiyoshi Hirao, Motohiro Toriyama, and Hidehiko Tanaka. "Silicon carbide ceramics prepared by pulse electric current sintering of β–SiC and α–SiC powders with oxide and nonoxide additives." Journal of Materials Research 14, no. 8 (August 1999): 3363–69. http://dx.doi.org/10.1557/jmr.1999.0455.

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Using a pulse electric current sintering (PECS) method, β–SiC and α–SiC powders doped with a few weight percent of Al2O3–Y2O3oxide or Al4C3–B4C–C nonoxide additives were rapidly densified to high densities (95.2–99.7%) within less than 30 min of total processing time. When Al2O3–Y2O3additive was used, both ceramics resulting from β–SiC and α–SiC had fine, equiaxed microstructures. In contrast, when Al4C3–B4C–C additive was used, the ceramic resulting from α–SiC had a coarse, equiaxed microstructure, whereas the ceramic resulting from β–SiC was composed of large elongated grains whose formation was accompanied by the β →?α phase transformation of SiC. Compared with the Al2O3–Y2O3-doped SiC ceramics, the Al4C3–B4C–C-doped SiC ceramics had higher densities, lower fracture toughness, and higher hardness. The fracture mode of the oxide-doped SiC was mainly intergranular, whereas the nonoxide-doped SiC exhibited almost complete intragranular fracture that was attributed to the higher interfacial bonding strength.

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Frei, H., and G. Grathwohl. "Fracture of ceramics in the SEM." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 4 (August 1990): 892–93. http://dx.doi.org/10.1017/s0424820100177593.

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The progress in the development of advanced structural ceramics is characterized by a remarkable increase in their strength and fracture toughness. Further improvement of these essential mechanical properties is still desirable and requires a fundamental understanding of the crack propagation process. In the new types of ceramic microstructures, e. g. in whisker-, particle-, or platelet-reinforced ceramics the relevant crack growth processes are not adequately understood. These processes are responsible, for example, for the R-curve behaviour which may be due to the formation of a process zone around the crack tip, or by a wake effect of interacting forces between the crack surfaces. Furthermore, fatigue in ceramics is a problem in toughened ceramics in particular and relies directly on the various mechanisms of increased crack resistance.In order to understand the formation and extension of the relevant micro- and macrocracks, SEM is a powerful tool because of its ample range of magnification and large depth of focus.A complete description of the bending device used is given elsewhere, so that only the main features will be mentioned here.Using a very stiff frame and a position controlled piezo translator it was possible to obtain controlled fracture of brittle ceramic materials. This means that a crack is not spontaneously propagated through the specimen, but slowly advances micrometer for micrometer. The fracture experiments are recorded by a video recorder directly connected to the SEM.

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Aronov, V., and T. Mesyef. "Wear in Ceramic/Ceramic and Ceramic/Metal Reciprocating Sliding Contact. Part 1." Journal of Tribology 108, no. 1 (January 1, 1986): 16–21. http://dx.doi.org/10.1115/1.3261136.

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This paper is the first of a series of two devoted to an investigation of wear mechanisms in ceramic/ceramic and ceramic/metal sliding contact tribological systems at high temperatures and exhaust gas environment. The first part presents results of the experiments carried out at room temperature and air environment. Scanning electron microscope, optical microscope and X-ray dispersion analysis were used for an identification of wear mechanisms. Surface geometry and morphology, friction coefficients and wear were determined as functions of sliding distance, nominal contact pressure, sliding velocity and mechanical properties of specimens (hardness and fracture toughness). The wear mechanism of ceramics rubbed against ceramics may be attributed to intensive plastic deformation of surfaces resulting in low cycle fatigue. The wear mechanism of ceramics rubbed against metals was polishing and surface fracture, while that of metals was adhesive transfer of material on to ceramic surfaces. Wear rates and friction coefficients were independent of mechanical properties of metallic samples.

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Pastor, J. Y., J. LLorca, J. Planas, and M. Elices. "Stable Crack Growth in Ceramics at Ambient and Elevated Temperatures." Journal of Engineering Materials and Technology 115, no. 3 (July 1, 1993): 281–85. http://dx.doi.org/10.1115/1.2904219.

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Quasi-static, stable crack propagation tests in ceramics are presented. The tests are performed using a recently developed technique in which the crack mouth opening displacement (CMOD) is continuously monitored during the test by means of a laser extensometer, and this signal is employed to control a servo-hydraulic testing machine. The advantages of such tests to characterize the fracture behavior of ceramics at high temperature are described, and the technique is used to study the fracture behavior of an ytria-partially stabilized zirconia ceramic at ambient and elevated temperatures.

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Yan, Xingheng, Xingui Zhou, and Honglei Wang. "Effect of Additive Ti3SiC2 Content on the Mechanical Properties of B4C–TiB2 Composites Ceramics Sintered by Spark Plasma Sintering." Materials 13, no. 20 (October 16, 2020): 4616. http://dx.doi.org/10.3390/ma13204616.

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B4C–TiB2 composite ceramics with ultra-high fracture toughness were successfully prepared via spark plasma sintering (SPS) at 1900 °C using B4C and Ti3SiC2 as raw materials. The results showed that compared with pure B4C ceramics sintered by SPS, the hardness of B4C–TiB2 composite ceramics was decreased, but the flexural strength and fracture toughness were significantly improved; the fracture toughness especially was greatly improved. When the content of Ti3SiC2 was 30 vol.%, the B4C–TiB2 composite ceramic had the best comprehensive mechanical properties: hardness, bending strength and fracture toughness were 27.28 GPa, 405.11 MPa and 18.94 MPa·m1/2, respectively. The fracture mode of the B4C–TiB2 composite ceramics was a mixture of transgranular fracture and intergranular fracture. Two main reasons for the ultra-high fracture toughness were the existence of lamellar graphite at the grain boundary, and the formation of a three-dimensional interpenetrating network covering the whole composite.

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Kishi, T. "Dynamic fracture toughness in ceramics and ceramics matrix composites." Engineering Fracture Mechanics 40, no. 4-5 (January 1991): 785–90. http://dx.doi.org/10.1016/0013-7944(91)90235-s.

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Kaygorodov, Anton Sergeevich, Vasily Ivanovich Krutikov, and Sergey Nikolaevich Paranin. "Influence of the Dopants on the Mechanical Properties of Alumina-Based Ceramics." Journal of Ceramics 2013 (December 25, 2013): 1–6. http://dx.doi.org/10.1155/2013/430408.

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In the present study the mechanical properties of dense alumina-based ceramics obtained by two processing routes are investigated. The application of magnetic-pulsed compaction or hot pressing of the powder leads to a comparable combination of microhardness, elastic modulus, and fracture toughness. The insertion of Al into Al2O3 powder increases the microdistortions of the crystalline lattice, resulting in the sufficient decrease of indentation wear-resistance. The usage of ZrO2 or TiCN as dopants to alumina matrix improves slightly the mechanics of the composites with a noticeable decrease of the material lost by 30% compared to pure alumina at closely spaced arrays of indents. Regardless of the synthesis method, the ceramic grains were formed completely with the fracture travelling along the grain boundaries.

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Fulton, Chandler C., and Huajian Gao. "Electrical Nonlinearity in Fracture of Piezoelectric Ceramics." Applied Mechanics Reviews 50, no. 11S (November 1, 1997): S56—S63. http://dx.doi.org/10.1115/1.3101851.

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The structural reliability of piezoelectric ceramics in smart sensors and actuators is hindered by the lack of an appropriate fracture mechanics model. Recent experimental observations of their cracking behavior under combined electrical and mechanical loads contradict predictions made by the linear theory. Evidently, a fracture criterion suitable for piezoelectrics must account for material nonlinearity. Because these materials are typically mechanically brittle, we expect electrical ductility to be the dominant effect. By adopting a multiscale viewpoint, we identify a region of electrical nonlinearity near the crack tip in which the mechanical response of the material remains linear. The equilibrium equations for a fully anisotropic solid have closed-form solutions if the material’s behavior is assumed to be entirely linear outside of the plane of the crack. This approximation is equivalent to Dugdale’s model of the plastic zone in cracked metal sheets. The energy release rate derived using this load for specimens with cracks perpendicular to the poling direction. A remarkable feature of our model is that the energy release rate is strictly independent of the form of the nonlinear electrical constitutive relation. In fact, the material may even experience domain switching in the Dugdale zone without affecting the fracture criterion determined by our formulation.

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Gogotsi, George. "Fracture Resistance of Ceramics: Direct Measurements." Advances in Science and Technology 45 (October 2006): 95–100. http://dx.doi.org/10.4028/www.scientific.net/ast.45.95.

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Fracture resistance of ceramics is evaluated by flaking off the specimen edge and chip scar surfaces are examined. The fracture resistance characteristic was calculated from the results of direct measurements that did not make use of linear fracture mechanics concepts, which is typical of conventional fracture toughness test methods. A fracture resistance test method termed the edge fracture (EF) method is discussed. This method is built upon measuring the flaking resistance FR on indentation of the specimen. The FR values for homogeneous elastic ceramics are proportional to the KIc ones determined by the SEVNB method. Flaking resistance vs chip size relationships (R-lines) are derived. Data analysis was built upon statistically reliable measurements on advanced alumina, zirconia, scandia, and silicon nitride ceramics.

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Motola, Yael, Leslie Banks-Sills, and Victor Fourman. "On fracture testing of piezoelectric ceramics." International Journal of Fracture 159, no. 2 (August 30, 2009): 167–90. http://dx.doi.org/10.1007/s10704-009-9392-x.

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Chen, Chun Hong, and Hideo Awaji. "Mechanical Properties of Al₂TiO₅ Ceramics." Key Engineering Materials 336-338 (April 2007): 1417–19. http://dx.doi.org/10.4028/www.scientific.net/kem.336-338.1417.

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Aluminum titanate ceramics (Al2TiO5) is a synthetic ceramic material of potential interest for many structural applications. A critical feature, which greatly limits the mechanical properties of polycrystalline Al2TiO5, is considerable intergranular microcracking, which occurs due to the high thermal anisotropy of individual grains. In this study, the temperature dependencies of mechanical properties were discussed along with the microstructure observation. Both of fracture strength and fracture toughness increased considerably with increasing the temperature. These phenomena were explained on the basis of the stress redistribution and unique microscopic feature on the fracture surface of aluminum titanate ceramics. The experimental results also revealed that the repeated heat treatments resulted in the change of fracture strength and fracture toughness due to the stress redistribution in the Al2TiO5 matrix.

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Markandan, Kalaimani, Jit Kai Chin, and Michelle T. T. Tan. "Study on Mechanical Properties of Zirconia-Alumina Based Ceramics." Applied Mechanics and Materials 625 (September 2014): 81–84. http://dx.doi.org/10.4028/www.scientific.net/amm.625.81.

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This paper describes the characterisations of ceramic composites consisting of different compositions of alumina and zirconia. The material characterisations were performed from the aspects of densification, hardness and fracture toughness. The surface morphology and elemental composition of the composite were studied using SEM and EDX respectively. As for physical properties, the highest attainable hardness and fracture toughness were 11.35 GPa and 3.41 MPa m0.5respectively for ceramic composite consisted of 80 wt % Zr and 20 wt% Al. Sintering at 1150oC assisted in the densification of ceramics.

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Jauffrès, David, Xiaoxing Liu, and Christophe L. Martin. "Fracture mechanics of porous ceramics using discrete element simulations." Procedia Engineering 10 (2011): 2719–24. http://dx.doi.org/10.1016/j.proeng.2011.04.453.

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Kobayashi, H., Yoshikazu Arai, H. Nakamura, and M. Nakamura. "Mechanics Approach to Fracture Strength of Ceramics/Metal Joints." Key Engineering Materials 51-52 (January 1991): 179–84. http://dx.doi.org/10.4028/www.scientific.net/kem.51-52.179.

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KOBAYASHI, Hideo, Yoshio ARAI, Haruo NAKAMURA, and Minoru NAKAMURA. "Mechanics approach to fracture strength of ceramics/metal joints." Transactions of the Japan Society of Mechanical Engineers Series A 55, no. 512 (1989): 750–55. http://dx.doi.org/10.1299/kikaia.55.750.

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Tian, Xin Li, Jian Quan Wang, Bao Guo Zhang, and Peng Xiao Wang. "Experimental Research on the Relationship between Surface Polishing and Fracture Strength for Ground Ceramics." Materials Science Forum 770 (October 2013): 433–36. http://dx.doi.org/10.4028/www.scientific.net/msf.770.433.

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Fracture strength is one of the key mechanics performances for engineering ceramics products, greatly influenced by the microscopic topography and residual stress field of ground surface. In this work, several testing equipments, such as the metallurgical microscope, surface profiler and X ray residual stress tester were introduced to investigate the relationships between microscopic topography, surface roughness, residual stress and fracture strength of ground ceramics, after the surface grinding and mechanical polishing. The experimental results show that a smoother machined surface with low roughness and residual stress is obtained through polishing with absolute alcohol for 20 minutes; the fracture strength of Si3N4SiC and Al2O3 are increased by 6.64%8.18% and 6.58% respectively, comparing to the ceramics without polishing; the surface stress concentration and residual tensile stress of polished ceramics are both reduced after an appropriate time of polishing process, which causes a certain improvement of ground fracture strength.

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Tsutsumi, Mitsuyoshi, and Nagatoshi Okabe. "OS08W0290 The fracture model of porous ceramics subjected to mechanical load." Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics 2003.2 (2003): _OS08W0290. http://dx.doi.org/10.1299/jsmeatem.2003.2._os08w0290.

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Yu, Jinfeng, Xinhua Ni, Xiequan Liu, Yunwei Fu, and Zhihong Du. "Damage and fracture model for eutectic composite ceramics." Acta Mechanica Sinica 35, no. 1 (October 8, 2018): 190–200. http://dx.doi.org/10.1007/s10409-018-0801-0.

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Almeida Junior, A. A. de, G. L. Adabo, B. R. Galvão, D. Longhini, B. G. Simba, and C. dos Santos. "Bending strength and reliability of porcelains used in all-ceramic dental restorations." Cerâmica 64, no. 372 (December 2018): 491–97. http://dx.doi.org/10.1590/0366-69132018643722382.

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Abstract Four dental porcelains for covering zirconia were sintered (fired) at 910-960 °C and characterized, focusing in analyzing reliability, physical and mechanical properties. Samples with relative density close to 99% presented leucite crystallization apart from residual amorphous phase. Hardness between 491±23 and 575±32 HV was different among all ceramics. Fracture toughness between 1.13±0.11 and 1.42±0.25 MPa.m1/2 was statistically different. Bending strength results were not different for three porcelain groups (73±9 to 75±12 MPa), with the exception of one specific group (62±4 MPa). Weibull analysis indicated bending strength between 73 and 75 MPa, Weibull modulus (m) between 5.7 and 7.1, while the ceramic with strength of 60 MPa presented m=13.6. The use of classical theory of fracture mechanics associated to the results of properties obtained in this work indicated the critical failure size in these ceramics lays between 65 and 90 μm and the theoretical fracture energy of porcelains is approximately from 10.5 to 16.3 J/m. It was concluded that the porcelains had different behavior, and it seems that there is no clear relationship among the studied properties.

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Wei, Lanhua, and Brian R. Lawn. "Thermal wave analysis of contact damage in ceramics: Case study on alumina." Journal of Materials Research 11, no. 4 (April 1996): 939–47. http://dx.doi.org/10.1557/jmr.1996.0118.

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Thermal waves are used to image damage accumulation digitally beneath Hertzian contacts in ceramics. Alumina ceramics over a range of grain size 3–48 μm are used in a case study. The nature of the images changes with increasing alumina grain size, reflecting a transition in damage mode from well-defined cone fracture in the finer-grain materials to distributed subsurface microfracture in the coarser-grain materials. Quantitative determinations of microcrack densities are evaluated in the latter case by deconvoluting thermal diffusivities from the image data. These determinations confirm the grain-size dependence of degree of damage predicted by fracture mechanics models. Potential advantages and disadvantages of thermal waves as a route to damage characterization in ceramic systems are discussed.

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Han, Fei, Yu Hong Chen, Sheng Wei Guo, and Jian Jun Ma. "The Influence of Different Particle Size of Carbon Powders on the Preparation of Porous Silicon Carbide Ceramic." Advanced Materials Research 284-286 (July 2011): 1370–74. http://dx.doi.org/10.4028/www.scientific.net/amr.284-286.1370.

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On the preparation of porous ceramics with composite sintering auxiliaries Y2O3-Al2O3 , the main ingredient of SIC , and CMC as the porous agent . Having studied the C content of composite structure and mechanical properties , And analysised the composite fracture morphology with SEM . The results show that, when using different particle size of carbon powders mixed the porous silicon carbide ceramic sample size powdered carbon than a single sample of micro skeleton intact, the shapes of holes, and more rules are uniformly distributed, comprehensive mechanics performance is better.

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Bermejo, Raúl, Lucie Šestáková, Hannes Grünbichler, Tanja Lube, Peter Supancic, and Robert Danzer. "Fracture Mechanisms of Structural and Functional Multilayer Ceramic Structures." Key Engineering Materials 465 (January 2011): 41–46. http://dx.doi.org/10.4028/www.scientific.net/kem.465.41.

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The fracture of mechanically loaded ceramics is a consequence of material critical defects located either within the bulk or at the surface, resulting from the processing and/or machining and handling procedures. The size and type of these defects determine the mechanical strength of the specimens, yielding a statistically variable strength and brittle fracture which limits their use for load-bearing applications. In recent years the attempt to design bio-inspired multilayer ceramics has been proposed as an alternative choice for the design of structural components with improved fracture toughness (e.g. through energy release mechanisms such as crack branching or crack deflection) and mechanical reliability (i.e. flaw tolerant materials). This approach could be extended to complex multilayer engineering components such as piezoelectric actuators or LTCCs (consisting of an interdigitated layered structure of ceramic layers and thin metal electrodes) in order to enhance their performance functionality as well as ensuring mechanical reliability. In this work the fracture mechanisms in several structural and functional multilayer components are investigated in order to understand the role of the microstructure and layered architecture (e.g. metal-ceramic or ceramic-ceramic) on their mechanical behaviour. Design guidelines based on experiments and theoretical approaches are given aiming to enhance the reliability of multilayer components.

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McCool, J. I. "Predicting Microfracture in Ceramics Via a Microcontact Model." Journal of Tribology 108, no. 3 (July 1, 1986): 380–85. http://dx.doi.org/10.1115/1.3261209.

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The point of view is taken that for ceramics, cone cracking on the microscale assumes the same role as plastic asperity deformation in metal materials, namely, as the agent causing stress raising micropits which precipitate surface fatigue. Empirical fracture data are interpreted in the context of published fracture mechanics analyses of cone cracking in static and sliding contact and used within the Greenwood-Williamson stochastic microcontact model to predict the relative likelihood of cone cracking when a rough flat ceramic contacts a smooth ceramic flat of the same material. The Greenwood-Williamson model is reviewed and its predictions are shown, for the steel and ceramic surfaces considered, to compare favorably to the more general anisotropic microcontact model ASPERSIM. A microfracture index analogous to the Greenwood-Williamson plasticity index, is shown to be a determinant of the ability of a surface to resist cone cracking.

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Muktepavela, F., A. Zolotarjovs, R. Zabels, K. Kundzins, E. Gorokhova, and E. Tamanis. "Comparative Study on Micromechanical Properties of ZnO:Ga and ZnO:In Luminiscent Ceramics." Latvian Journal of Physics and Technical Sciences 58, no. 1 (January 29, 2021): 23–32. http://dx.doi.org/10.2478/lpts-2021-0003.

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Abstract Indium (0.038 at.%) and gallium (0.042 at.%) doped ZnO ceramics were prepared by hot pressing. Ceramics were investigated to determine their structural and mechanical characteristics for the prospective use in scintillators. Based on results of nanoindentation, atom force and scanning electron microscopy as well as energy dispersive X-ray spectra measurements, locations of gallium within grain, indium at grain boundaries (GBs) and their different effect on the mechanical properties of ZnO ceramics were detected. Doping of gallium led to the increased modulus of elasticity in grain, decreased hardness near GBs, stabilization of micropores and brittle intercrystalline fracture mode. ZnO:In ceramic has modulus of elasticity and hardness values close to ZnO characteristics, the increased fracture toughness and some plasticity near GBs. Differences in the micromechanical properties of the ceramics correlate with the location of dopants. Results demonstrate that the ZnO:In ceramic has a greater stress relaxation potential than the ZnO:Ga.

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Sachidhananda, T. G., and V. Adake Chandrashekhar. "Electric Discharge Machining of Conducting Ceramics - A Review." Materials Science Forum 1019 (January 2021): 121–28. http://dx.doi.org/10.4028/www.scientific.net/msf.1019.121.

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Electrical Discharge machining (EDM) is a nonconventional machining technique, which has been widely used to produce dies and mold. Harder Materials can be machined into complex shapes as long as they conduct electricity. Recent advances in the technologies brought the development of new engineering materials, which are hard to machine with traditional machining processes. Being one of these materials, ceramics possess some unique properties like piezoelectricity and tribological properties which are not found in metal and polymers. EDM is capable of machining these ceramics, given these materials have an adequately high electrical conductivity. Preparing conducting ceramics is pre-requisite for incorporating ceramics in EDM. Different techniques such as compaction, tape casting, extrusion, injection molding and slip casting are used form green ceramic body. These green bodies are subsequently sintered to obtain ceramic parts. Adding conducting elements in the ceramics while processing results in conducting ceramics. These additions increase hardness but fracture toughness of body is compromised. Ceramic parts can also be machined by using assisting electrode and pyrolytic carbon technique. This paper discusses the various methods of shaping conducting ceramics and its machining characteristics for EDM application

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Himoto, Iori, Airi Nakashima, Seiji Yamashita, and Hideki Kita. "OS8-38 Statistical Fracture Analysis of Si-SiC Porous Ceramics with Skeletal Structure(Advanced materials,OS8 Fatigue and fracture mechanics,STRENGTH OF MATERIALS)." Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics 2015.14 (2015): 148. http://dx.doi.org/10.1299/jsmeatem.2015.14.148.

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Min, Xin, Ming Hao Fang, Yan Gai Liu, Zhao Hui Huang, Feng Jiao Liu, and Chao Tang. "Mechanical Properties of ZrO₂–LaMgAl₁₁O₁₉ Ceramics." Key Engineering Materials 512-515 (June 2012): 455–58. http://dx.doi.org/10.4028/www.scientific.net/kem.512-515.455.

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ZrO2 ceramics have been widely used to many fields with its excellent physical and chemical properties, but the mechanical properties of YSZ ceramics, especially the fracture toughness, decline caused by the failure of the phase transformation toughening at high temperature. In this investigation, plate-like LaMgAl11O19 toughened ZrO2 ceramics were prepared by pressureless sintering at 1550 °C for 3h in air . The bulk density of the sintered samples are between 5.5 to 6.0 g/cm3, and the relative density are above 93%. The mechanical properties of the ZrO2-LaMgAl11O19 ceramics were studied systematically at room temperature. The flexure strength and fracture toughness of ZrO2-LaMgAl11O19 ceramic are 811.8 MPa and 13.9 MPa•m½ with the LMA addition of 2wt%.

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Xue, J. X., H. B. Wu, and Q. P. Sun. "Finite Element Simulation of Ceramics Machining." Key Engineering Materials 693 (May 2016): 775–79. http://dx.doi.org/10.4028/www.scientific.net/kem.693.775.

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The evolution of crack models based on fracture mechanics is reviewed. The brittle cracking model in Abaqucs is used to simulate the machining process of Al2O3. The result shows that it’s appropriate to simulate the machining process of ceramics with fracture energy cracking criterion and post-failure constitutive relation in a smeared cracking representation. Although more works are needed in the future to resolve the mesh sensitivity. The material removal mechanism of ceramics is confirmed to be the brittle fracture regime.

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Burns, S. J., and K. Y. Chia. "Nonlinear Hertzian Indentation Fracture Mechanics." Journal of the American Ceramic Society 78, no. 9 (September 1995): 2321–27. http://dx.doi.org/10.1111/j.1151-2916.1995.tb08664.x.

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García-Prieto, A., J. Hernández, M. López, and C. Baudín. "Controlled Fracture Test for Brittle Ceramics." Journal of Strain Analysis for Engineering Design 46, no. 1 (September 10, 2010): 27–32. http://dx.doi.org/10.1243/03093247jsa685.

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Journal articles on the topic 'Fracture mechanics of ceramics'

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