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Journal articles on the topic 'Facture toughness; Crack growth'

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Published: 4 June 2021
Last updated: 16 February 2022

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1

Kuang, Jia Cai, Hong Lei Wang, Xin Gui Zhou, and Ying Jun Deng. "Fracture Toughness of CNTs/AlN Ceramics Tested by Indentation." Advanced Materials Research 177 (December 2010): 151–53. http://dx.doi.org/10.4028/www.scientific.net/amr.177.151.

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CNTs/AlN ceramics were fabricated by hot-pressing sintering process. The fracture toughness was measured by indentation method. The morphologies of indentation cracks were analyzed by SEM. The results show that the facture toughness of AlN was slightly improved because appreciate toughening mechanisms such as CNTs pull-out, crack bridging and deflect operate in CNTs/AlN. In addition, the facture toughness of CNTs/AlN increased with increasing CNTs content up to 3wt%. Then, the fracture toughness decrease when the CNTs content is 4wt%.
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2

Blugan, Gurdial, Richard Dobedoe, I. Gee, Nina Orlovskaya, and Jakob Kübler. "Failure Behaviour of High Toughness Multi-Layer Si3N4 and Si3N4-TiN Based Laminates." Key Engineering Materials 290 (July 2005): 175–82. http://dx.doi.org/10.4028/www.scientific.net/kem.290.175.

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Multi-layer laminates were produced using alternating layers of Si3N4 and Si3N4+TiN. The differences in the coefficient of thermal expansions between the alternating layers lead to residual stresses after cooling. These are compressive in the Si3N4 layers and tensile in the Si3N4+TiN layers. The existence of these stresses in the laminates effect the crack propagation behaviour during failure. Different designs of laminates were produced with external layers under compression and tension exhibiting different failure mechanisms. Facture toughness was measured by SEVNB method. In systems with external layers under compression the measured fracture toughness was up to three times that of Si3N4, i.e. up to 17 MPa m1/2. In systems with external layers under tension during failure the energy absorbing effects of crack deflection and crack bifurcation were obtained. High temperature tests were performed to determine the onset temperature for residual stresses in these laminates. Micro-laminates with compressive layers of only 30 µm thickness with high strength and fracture toughness and were manufactured.
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3

Suresh, S., and A. K. Vasudevan. "On the relationship between crack initiation toughness and crack growth toughness." Materials Science and Engineering 79, no. 2 (May 1986): 183–90. http://dx.doi.org/10.1016/0025-5416(86)90403-9.

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4

Gu, Inhoy. "Crack-Tip-Acuity Effect on Crack Growth Initiation." Journal of Engineering Materials and Technology 109, no. 3 (July 1, 1987): 216–20. http://dx.doi.org/10.1115/1.3225966.

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For a stationary crack of an initially finite root radius in plane-strain tension, the strain fields around the smoothly blunted crack-tip are calculated for each deformation stage using the slipline field method for nonhardening plastic material. The crack growth initiation from the blunt crack-tip in small-scale yielding, with a full triaxiality ahead of the crack-line, is predicted based on the fracture criterion of the fracture strain at a characteristic distance, obtained by applying the criterion to the case of a sharp crack-tip, in which the effect of the initial root radius on the strain distribution can be neglected. The predicted toughness for mild steel is in reasonable agreement with an experiment. For other materials, the observed J-integral value at fracture initiation, consistent with the present analysis, increases linearly with the initial root radius, but its rate shows a large deviation from the model, which is discussed due to the shear band development. The analysis also predicts that the toughness of a cracked low-ductility material does not increase by making the initial crack-root profile round, and that the reduced triaxiality at the crack-tip brings about a toughness increase.
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5

Qi, Hong Yu, Xiao Guang Yang, and Rui Li. "Interfacial Fracture Toughness of APS Thermal Barrier Coating under High Temperature." Key Engineering Materials 348-349 (September 2007): 181–84. http://dx.doi.org/10.4028/www.scientific.net/kem.348-349.181.

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Thermal barrier coating (TBC) is an essential requirement of a modern gas turbine engine. The TBC failure is the delamination and spallation. The oxidation damage under high temperature results in the reduction of interfacial adhesion. The interfacial fracture toughness is an important property to analyze the TBC failure. The interfacial fracture toughness of ceramic coating - bond coating has been researched in the past. However, the facture toughness of the bond coating - substrate due to the Al depletion was very few studied. In this study, a NiCrAlY bond coating by air plasma spray (APS) was deposited. The substrate was directionally solidified superalloy (DZ40M). Isothermal oxidation was performed at 10500 for 100h. Using the HXZ-1000 micro-hardness equipment, the five different times was chosen to test the hardness and the crack length, and then the fracture toughness was obtained. While the oxidation exposure time increased at 10500, the hardness of the substrate close to the bond coating decreased with the increase of the bond coating’ hardness. Meanwhile, the interfacial fracture toughness of the bond coating - substrate decreased because of the Al depletion.
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6

Pham, Hai Vu, and Makoto Nanko. "Crack-Healing Function of Nano-Ni/(ZrO2+Al2O3) Hybrid Materials." Materials Science Forum 804 (October 2014): 179–82. http://dx.doi.org/10.4028/www.scientific.net/msf.804.179.

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Ni/(ZrO2+Al2O3) nanocomposites have excellent mechanical properties, as well as self-healing function. The powder preparation was conducted by drying slurry consisting of distilled water, Al2O3, 3 mol % Y2O3doped ZrO2and nickel nitrate. After reduction at 600°C in a stream of Ar-1% H2, the powder mixture was consolidated by pulsed electric current sintering (PECS) at 1300°C for 5 min under 50 MPa. Surface cracks were generated by Vickers indentation on the polished surface of the test samples. Ni/(YZ+Al2O3) shows 1200 MPa in bending strength and 6.1 MPa m1/2in facture toughness. Crack-healing and oxidation tests were conducted at temperature ranging from 1100 to 1300°C in air. As a result, crack-disappearance occurred slightly faster than that of Ni/Al2O3.
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7

Pavelko, Vitalijs. "On the Crack Quasi-Static Growth." Key Engineering Materials 827 (December 2019): 312–17. http://dx.doi.org/10.4028/www.scientific.net/kem.827.312.

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The theoretical model of quasi-static crack growth in the elastic-plastic material under load variation in a wide range. Small-scale yielding is principal assumption and main restriction of proposed theory. The model of crack growth provides for continues and interrelated both the crack propagation and plastic deformation development. The nonlinear first-order differential equation describes the quasi-static process of crack growth. In dimensionless form this equation invariant in respect to geometrical configuration and material. The critical size of the plastic zone is proposed as the characteristics of material resistance which is directly connected with the fracture toughness, but more convenient in practical applications of invariant equation. The demonstration of solution is performed for the double cantilever beam that widely used as the standard (DCB) sample for measurement of the mode-I interlaminar fracture toughness. he short analysis of some properties of solution of the invariant equation and its application is done.
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8

Chasiotis, I., S. W. Cho, and K. Jonnalagadda. "Fracture Toughness and Subcritical Crack Growth in Polycrystalline Silicon." Journal of Applied Mechanics 73, no. 5 (December 10, 2005): 714–22. http://dx.doi.org/10.1115/1.2172268.

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The fracture behavior of polycrystalline silicon in the presence of atomically sharp cracks is important in the determination of the mechanical reliability of microelectromechanical system (MEMS) components. The mode-I critical stress intensity factor and crack tip displacements in the vicinity of atomically sharp edge cracks in polycrystalline silicon MEMS scale specimens were measured via an in situ atomic force microscopy/digital image correlation method. The effective (macroscopic) mode-I critical stress intensity factor for specimens from different fabrication runs was 1.00±0.1MPa√m, where 0.1MPa√m is the standard deviation that was attributed to local cleavage anisotropy and grain boundary effects. The experimental near crack tip displacements were in good agreement with the linearly elastic fracture mechanics solution, which supports K dominance in polysilicon at the scale of a few microns. The mechanical characterization method implemented in this work allowed for direct experimental evidence of incremental (subcritical) crack growth in polycrystalline silicon that occurred with crack increments of 1-2μm. The variation in experimental effective critical stress intensity factors and the incremental crack growth in brittle polysilicon were attributed to local cleavage anisotropy in individual silicon grains where the crack tip resided and whose fracture characteristics controlled the overall fracture process resulting in different local and macroscopic stress intensity factors.
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9

Zhang, M.-J., F.-X. Zhi, and X.-R. Su. "Fracture toughness and crack growth mechanism for multiphase polymers." Polymer Engineering and Science 29, no. 16 (August 1989): 1142–46. http://dx.doi.org/10.1002/pen.760291612.

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10

Sevillano, J. Gil. "Toughness and Fatigue Crack Growth Rate of Textured Metals." Textures and Microstructures 12, no. 1-3 (January 1, 1990): 77–87. http://dx.doi.org/10.1155/tsm.12.77.

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The influence of anisotropy of crystallographic origin on both fracture toughness and the rate of stage-II ductile fatigue crack growth in textured metals is discussed in terms of a plane-strain small geometry change solution for plastic non-hardening materials (a Prandtl-type slip-line field solution accounting for anisotropy). Results corresponding to FCC or BCC metals sliding, respectively, on {111} 〈110〉 or {110} 〈111〉 systems are presented. Remarkable effects of both texture toughening and fatigue crack growth rate anisotropy are predicted. Stronger effects are anticipated in more anisotropic metals (HCP).
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11

Wei, Yang. "Toughness increment by crack growth in toughened structural materials." Acta Mechanica Sinica 7, no. 2 (May 1991): 131–39. http://dx.doi.org/10.1007/bf02486840.

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12

Fager, Leif-Olof, and J. L. Bassani. "Stable Crack Growth in Rate-Dependent Materials With Damage." Journal of Engineering Materials and Technology 115, no. 3 (July 1, 1993): 252–61. http://dx.doi.org/10.1115/1.2904215.

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A cohesive zone model of the Dugdale-Barenblatt type is used to investigate crack growth under small-scale-creep/damage conditions. The material inside the cohesive zone is described by a power-law viscous overstress relation modified by a one-parameter damage function of the Kachanov type. The stress and displacement profiles in the cohesive zone and the velocity dependence of the fracture toughness are investigated. It is seen that the fracture toughness increases rapidly with the velocity and asymptotically approaches the case that neglects damage.
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13

Maksimov, A. B., I. P. Shevchenko, and I. S. Erokhina. "Determination of the metal toughness components in impact-bending test." Industrial laboratory. Diagnostics of materials 84, no. 12 (December 20, 2018): 68–72. http://dx.doi.org/10.26896/1028-6861-2018-84-12-68-72.

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A method for separating the work of impact into two parts - the work of the crack nucleation and that of crack growth - which consists in testing two samples with the same stress concentrators and different cross-sectional dimensions at the notch site is developed. It is assumed that the work of crack nucleation is proportional to the width of the sample face on which the crack originates and the specific energy of crack formation, whereas the work of the crack growth is proportional to the length of crack development and the specific crack growth energy. In case of the sample fracture upon testing, the crack growth length is assumed equal to the sample width. Data on the work of fracture of two samples and their geometrical dimensions at the site of the notch are used to form a system of two linear equations in two unknowns, i.e., the specific energy of crack formation and specific energy of crack growth. The determined specific energy values are then used to calculate the work of crack nucleation and work of crack growth. The use of the analytical method improves the accuracy compared to graphical - extrapolative procedures. The novelty of the method consists in using one and the same form of the notch in test samples, thus providing the same conditions of the stress-strain state for crack nucleation and growth. Moreover, specimens with different cross-section dimensions are used to eliminate the scale effects. Since the specific energy of the crack nu-cleation and specific energy of the crack growth are independent of the scale factor, they are determined only by the properties of the metal. Introduction the specific energy of crack formation and growth makes possible to assign a specific physical meaning to the fracture energy.
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14

Donners, M. A. H., L. J. M. G. Dortmans, and G. de With. "Adsorption and Kinetic Effects on Crack Growth in MnZn Ferrites." Journal of Materials Research 15, no. 6 (June 2000): 1377–88. http://dx.doi.org/10.1557/jmr.2000.0200.

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The variation of the fracture toughness of MnZn ferrite ceramics with varying loading rate and humidity was determined with the aid of the single edge notched beam (SENB) test. A strong decrease with increasing humidity and decreasing loading rate was observed. A model for subcritical crack growth incorporating kinetic and adsorption effects was formulated to analyze the data. The value of the adsorptioncontrolled fracture toughness was determined independently by double torsion experiments and agreed favorably with the values as determined from the SENB data using the model. The strength of the material was determined, and analysis showed a strength behavior similar to the fracture toughness behavior, as predicted by the model. The analysis presented can be used to assess the subcritical crack growth behavior using a limited number of SENB specimens.
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15

Liechti, K. M., and Y. S. Chai. "Three Dimensional Effects in Interfacial Crack Growth." Applied Mechanics Reviews 43, no. 5S (May 1, 1990): S271—S273. http://dx.doi.org/10.1115/1.3120825.

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An increase of interfacial toughness, associated with increases in in-plane or antiplane shear components, has been noted for a number of bimaterial combinations. Some recent results are reviewed which suggest that the toughening effect could not be completely accounted for by plastic dissipation, bulk viscoelastic dissipation or asperity shielding. The possibility of changes in crack front shape under various loading directions is therefore considered.
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16

Stehn, Lars. "Fracture toughness and crack growth of brackish ice using chevron-notched specimens." Journal of Glaciology 40, no. 135 (1994): 415–26. http://dx.doi.org/10.1017/s0022143000007504.

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AbstractField-test equipment called FIFT (a Field Instrument for Fracture toughness Tests on ice) was used in both field and laboratory fracture-toughness tests on brackish sea ice from the Gulf of Bothnia. An experimental calibration was performed and a compliance expression was then derived for the Short Rod Chevron Notched (SRCN) specimen. Using the SRCN configuration, for which the initial crack growth is shown to be stable, and measured load-point displacements, preliminary crack-growth velocities are found. The obtained estimated crack velocity is, on average,ȧe= 20 ms−1, albeit with a large standard deviation. The results indicate that critical crack (crack-jumping) growth occurs. The apparent fracture toughness,KQ, was found to have a pronounced dependency on porosity in the form of brine volume. The results obtained are derived from a linearly elastic fracture mechanics (LEFM) theory. Consequently, the tests were designed to satisfy small-scale yielding requirements in terms of notch sensitivity and brittleness. The linearity of the load vs crack-opening displacement curves together with a size-effect study, showing that the specimen is notch-sensitive for grain-sizes ranging from 1.6 to nearly 100 mm, indicate that LEFM could be applicable.
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17

Stehn, Lars. "Fracture toughness and crack growth of brackish ice using chevron-notched specimens." Journal of Glaciology 40, no. 135 (1994): 415–26. http://dx.doi.org/10.3189/s0022143000007504.

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AbstractField-test equipment called FIFT (a Field Instrument for Fracture toughness Tests on ice) was used in both field and laboratory fracture-toughness tests on brackish sea ice from the Gulf of Bothnia. An experimental calibration was performed and a compliance expression was then derived for the Short Rod Chevron Notched (SRCN) specimen. Using the SRCN configuration, for which the initial crack growth is shown to be stable, and measured load-point displacements, preliminary crack-growth velocities are found. The obtained estimated crack velocity is, on average,ȧe= 20 ms−1, albeit with a large standard deviation. The results indicate that critical crack (crack-jumping) growth occurs. The apparent fracture toughness,KQ, was found to have a pronounced dependency on porosity in the form of brine volume. The results obtained are derived from a linearly elastic fracture mechanics (LEFM) theory. Consequently, the tests were designed to satisfy small-scale yielding requirements in terms of notch sensitivity and brittleness. The linearity of the load vs crack-opening displacement curves together with a size-effect study, showing that the specimen is notch-sensitive for grain-sizes ranging from 1.6 to nearly 100 mm, indicate that LEFM could be applicable.
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18

Oshima, Sota, Hisayoshi Ishida, Ryota Tanegashima, Takayuki Kusaka, and Tomo Takeda. "Experimental Characterization of Crack Growth Behavior in Adhesive Interface under Impact Loading." Key Engineering Materials 715 (September 2016): 116–21. http://dx.doi.org/10.4028/www.scientific.net/kem.715.116.

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A novel experimental method has been developed to evaluate the mode I crack growth behavior of adhesively bonded joints under impact loading. The split Hopkinson pressure bar (SHPB) technique and the digital image correlation (DIC) technique was employed to evaluate the crack growth behavior. To reduce the dynamic effects by controlling loading input of the SHPB apparatus, the fracture toughness was determined precisely based on static evaluation formula. To contrive the testing set-up, high loading rate was kept until the arrest of crack. The fracture toughness of titanium alloy/epoxy adhesively bonded joints during crack propagation was obtained successfully by using present method.
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19

Liu, Wen Lin, Wei Han, Zhi Tao Mu, Xiu Xia Wang, and Da Zhao Yu. "Research on Crack Growth Life and Sensibility Analysis of Influence Parameters in Crack Growth Life." Advanced Materials Research 317-319 (August 2011): 207–10. http://dx.doi.org/10.4028/www.scientific.net/amr.317-319.207.

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It requires a damage tolerance assessment for all airframes and engines to set the inspection windows for safe operation. A certain rotorcraft main rotor yoke were analyzed with NASGRO model. The sensibility analysis of influence parameters in crack growth life has been done. In order to calculate the sensibility index of influence factors to crack growth life, the factors were divided into input parameters and crack growth model parameters. The results show that the input parameters have the following precedence ordering: fatigue crack growth threshold, fracture spectrum, initial crack, fracture toughness, the sensibility values are 11.25, 8.5417, 0.8333, 0.1125, respectively. The NASGRO model parameters have the following precedence ordering: n, p, C, q. the sensibility values are 6.0417, -3.9583, 1.25, 0.1812, respectively.
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20

Watt, D. F., Pamela Nadin, and S. B. Biner. "The Fracture Toughness of Hardened Tool Steels." Journal of Engineering Materials and Technology 109, no. 4 (October 1, 1987): 314–18. http://dx.doi.org/10.1115/1.3225983.

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This report details the development of a three-stage fracture toughness testing procedure used to study the effect of tempering temperature on toughness in 01 tool steel. Modified compact tension specimens were used in which the fatigue precracking stage in the ASTM E-399 Procedure was replaced by stable precracking, followed by a slow crack growth. The specimen geometry has been designed to provide a region where slow crack growth can be achieved in brittle materials. Three parameters, load, crack opening displacement, and time have been monitored during the testing procedure and a combination of heat tinting and a compliance equation have been used to identify the position of the crack front. Significant KIC results have been obtained using a modified ASTM fracture toughness equation. An inverse relationship between KIC and hardness has been measured.
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21

Konosu, Shinji, Shinya Takagi, and Hidenori Shimazu. "110 Estimation of Stable Crack Growth in Fracture Toughness Testing." Proceedings of Ibaraki District Conference 2011.19 (2011): 19–20. http://dx.doi.org/10.1299/jsmeibaraki.2011.19.19.

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22

Singh, A., L. Tang, M. Dao, L. Lu, and S. Suresh. "Fracture toughness and fatigue crack growth characteristics of nanotwinned copper." Acta Materialia 59, no. 6 (April 2011): 2437–46. http://dx.doi.org/10.1016/j.actamat.2010.12.043.

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23

Hornbogen, Erhard. "Fracture toughness and fatigue crack growth of grey cast irons." Journal of Materials Science 20, no. 11 (November 1985): 3897–905. http://dx.doi.org/10.1007/bf00552378.

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24

Yang, Guoliang, Xuguang Li, Jingjiu Bi, and Shuaijie Cheng. "Dynamic Crack Initiation Toughness of Shale under Impact Loading." Energies 12, no. 9 (April 30, 2019): 1636. http://dx.doi.org/10.3390/en12091636.

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The impact loading of a notched semi-circular bend (NSCB) specimen of outcrop shale in Changning Sichuan was carried out using a split Hopkinson pressure bar (SHPB) to study the effect of shale bedding on the dynamic crack initiation toughness. Three loading configurations were tested: Crack-divider, Crack-splitter and Crack-arrester loading. Bedding plane has a significant effect on the crack initiation of shale. Under the Crack-divider and Crack-splitter modes, shale had lower dynamic crack initiation toughness. The dynamic crack initiation toughness of the shale was affected by the loading rate for all three loading configurations. The correlation between loading rate and dynamic crack initiation toughness was most significant for the Crack-arrester mode, while the Crack-splitter mode was the weakest. When loading was carried out on Crack-arrester, the bedding plane could change the direction of crack growth. In the Crack-splitter mode, only a small impact energy was needed to achieve effective expansion of a crack. The research results provide a theoretical basis for shale cracking.
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25

Fitzgerald, A. M., R. S. Iyer, R. H. Dauskardt, and T. W. Kenny. "Subcritical Crack Growth in Single-crystal Silicon Using Micromachined Specimens." Journal of Materials Research 17, no. 3 (March 2002): 683–92. http://dx.doi.org/10.1557/jmr.2002.0097.

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A micromachined specimen with a test section only 150-μm thick was developed for investigating subcritical crack growth in silicon. Crack growth rates in the range 10−4–10−10 m/s were measured as a function of applied stress intensity (v–K curves) during tests in humid air and dry nitrogen lasting up to 24 h. The fracture toughness, KIc of {110} silicon was also measured at 1.15 ± 0.08 MPa m1/2. While some evidence MPa-m1/2 of subcritical crack growth appeared to occur in the region 0.9 KIc < K > 0.98 KIc, the extremely high crack growth exponent (n 100) and the high ratio of the apparent stress corrosion threshold, KIscc, to the fracture toughness, KIscc/KIc > 0.9, suggests that no clear evidence exists for a stress corrosion process in silicon exposed to humid air.
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26

Zhu, Li Wei, Zhi Shou Zhu, Xin Nan Wang, and Chun Xiao Cao. "The Effect of Microstructure on Mechanical Properties and Fatigue Crack Growth Behavior of TC4-DT Alloy." Advanced Materials Research 490-495 (March 2012): 3767–72. http://dx.doi.org/10.4028/www.scientific.net/amr.490-495.3767.

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This paper examines the influence of different microstructure on the mechanical properties and fatigue crack growth behavior of TC4-DT alloy at room temperature. Different heat treatments were carried out in order to produce the microstructure of bimodal and lamellar conditions. Results show that, the tensile properties and fracture toughness of bimodal and lamellar microstructure was varied by different heat-treatment. In contrast on bimodal microstructure, the lamellar microstructure presents high fracture toughness and low fatigue crack growth rate, but the yield stress and ductility declines. The analysis results indicted that the lamellar microstructure obtained by air cooling from the  phase field showed the integrated condition of tensile properties and fracture toughness duo to the fine secondary  lamella, and the better fatigue crack growth behavior.
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27

Shenoy, Vijay B., and R. Krishna Kumar. "Dynamic Crack Growth in a Power Hardening Viscoplastic Material." Journal of Engineering Materials and Technology 116, no. 4 (October 1, 1994): 465–70. http://dx.doi.org/10.1115/1.2904314.

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In this paper a finite element analysis of steady-state dynamic crack growth under mode I plane strain small scale yielding conditions has been performed in a power law hardening rate dependent plastic material, characterized by the Perzyna over stress model. A modified version of the rate tangent modulus method has been used to update the stress. The main objective of the work is to obtain a quantitative relationship between dynamic fracture toughness ratio (K/Kss) and crack speed. A plastic strain criteria proposed by McClintock (1968) has been applied to obtain this relationship. It is found that dynamic stress intensity factor increases with velocity for all values of βˆ (a normalized viscosity parameter). At a low value of βˆ, which corresponds to high rate sensitivity, the fracture toughness ratio (K/Kss) increases with hardening. On the other hand, at a higher βˆ, the ratio increases initially and falls subsequently, with increasing hardening.
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28

Čamagić, Ivica, Nemanja Vasić, Predrag Živković, Aleksandar Radović, Tamara Sedmak, Meri Burzić, and Zijah Burzić. "Compatibility of Endurance Limit and Fatigue Crack Growth Parameters in Evaluation of Low Alloyed Steel Welded Joint Behaviour." Advanced Materials Research 1111 (July 2015): 121–26. http://dx.doi.org/10.4028/www.scientific.net/amr.1111.121.

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Analysis of fracture toughness of high-strength low alloyed steel, Nionikral-70, welded joint constituencies, subjected to variable load is given in this paper, using two parameters. Crack initiation resistance is determined by testing of endurance limit and by designing of Wöhler curves. Crack propagation resistance is determined by testing of crack growth rate, and accordingly determination of Paris equation parameters. Analysis of fracture toughness is given based on testing results, comparing obtained values for base metal, weld metal and heat affected zone.
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29

Ma, Gang, Jiangteng Li, and Huiwen Wang. "Related Rule Study of Subcritical Crack Growth and Threshold Values in Transversely Isotropic Slates." Geofluids 2020 (October 29, 2020): 1–15. http://dx.doi.org/10.1155/2020/8843381.

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Elastic parameters and the subcritical crack growth of different bedding angle slate specimens were studied using uniaxial compression testing and the double torsion constant displacement load relaxation method using SANS and MTS Insight machines. To study the relations of the mode-I stress intensity factor K I versus the subcritical crack growth velocity V , the fracture toughness K I C , the stagnation speed, and the threshold values, the double torsion constant displacement load relaxation method was carried out. The related rules between the bedding angles (β) and the uniaxial compressive strength, fracture toughness, and threshold values were investigated. Experimental results show that the uniaxial compression, the fracture toughness, and the threshold value curves move to the bottom then increase with the increase of the β angle. In addition, its fracture toughness is minimal when the β angle of the slates is 45°, and crack initiation and crack propagation are generated under load, which can lead to the failure of the slate. lg K I - lg V relations of transversely isotropic slates measured by this method are in accordance with linear rules, which is in good agreement with the Charles theory. The range of K 0 / K I C for these different bedding angle slates is from 0.511 to 0.789. The test results would provide the basis for studying seepage and time-dependency of rock engineering stability.
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30

Qiu, L. P., En Chun Zhu, Hua Zhang Zhou, and L. Y. Liu. "Fracture Toughness of Northeast China Larch." Key Engineering Materials 517 (June 2012): 661–68. http://dx.doi.org/10.4028/www.scientific.net/kem.517.661.

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Wood, as a green and environment-friendly building material, is widely used in building engineering. Naturally grown, wood has various defects like knots, cracks and inclined grain. Fracture Mechanics is thus an efficient tool to investigate the mechanical behavior of wood and wood-based composite products. According to Linear-elastic Fracture Mechanics (LEFM), fracture toughness can be introduced to measure the resistance to crack propagation. Crack was assumed to occur when the stress intensity factorKreached a critical valueKC.Fracture in wood usually involves not only the Mode I type (open) fracture, but also the Mode II type (shear) fracture. For getting a better understanding of the crack growth phenomenon of Northeast China Larch, it is, therefore, essential to assess theKICandKIIC, which are the critical stress intensity factors for Mode I and Mode II type fracture, respectively. In the current study,KICandKIIC, of Northeast China Larch were determined through tests with compact tension specimens and tests with compact symmetric shear specimens, respectively. In addition, the material properties tests were also performed. All of the specimens were cut from the same batch of Glulam beams. Based on the obtained data from experiments, LEFM was employed to explain the fracture failure in the form of crack propagation. Using Extended Finite Element Method (XFEM), simulation of the crack propagation in Mode I and Mode II was performed incorporating ABAQUS. The crack propagation and the load-displacement curves of numerical simulation were in good agreement with experiments, which validated that the proposed numerical approach is suitable for analysis of crack growth in the specimens. As part of a larger program to investigate the fracture behavior of Glulam beams made of Northeast China Larch, this study provides the material properties and validation of the numerical simulation approach. A series of experiments of full-size curved Glulam beams subject to bending and the corresponding simulations extending the numerical approach of this study to the cases of full-size wood composite members are under development.
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31

Park, Sang Dae, Mitsugu Todo, and Kazuo Arakawa. "Effect of Annealing on Fracture Mechanism of Biodegradable Poly(lactic acid)." Key Engineering Materials 261-263 (April 2004): 105–10. http://dx.doi.org/10.4028/www.scientific.net/kem.261-263.105.

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Effect of annealing on the fracture behavior of poly(lactic acid) (PLA) was investigated. Fracture toughness of PLA samples prepared under different annealing conditions was measured under static and dynamic loadings. Microstructure and crack growth behavior were characterized by polarizing microscopy (POM). Crystallinity was determined by DSC analysis. Fracture surface morphology was also studied by scanning electron microscopy. It was shown that the static fracture toughness increased with increase of crystallinity, while the dynamic toughness increased as crystallinity increased. POM exhibited that craze formation played an important role in the fracture mechanism of amorphous samples. Macroscopic fracture toughness and microscopic crack growth mechanism were correlated on the basis of these experimental results, and effect of annealing on the toughness and mechanism were discussed.
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32

OGASAWARA, Toshio, Naoto HIROSAKI, Yoshio AKIMUNE, and Eiichi YASUDA. "Fracture Toughness and Subcritical Crack Growth of Small Crack in Silicon Nitride at Room Temperature." Journal of the Ceramic Society of Japan 103, no. 1202 (1995): 1063–68. http://dx.doi.org/10.2109/jcersj.103.1063.

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33

Ritchie, R. O., and A. W. Thompson. "On macroscopic and microscopic analyses for crack initiation and crack growth toughness in ductile alloys." Metallurgical Transactions A 16, no. 1 (January 1985): 233–48. http://dx.doi.org/10.1007/bf02815305.

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34

Ritchie, R. O., and A. W. Thompson. "On macroscopic and microscopic analyses for crack initiation and crack growth toughness in ductile alloys." Metallurgical Transactions A 16, no. 2 (February 1985): 233–48. http://dx.doi.org/10.1007/bf02816050.

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35

Zhao, Yong Xiang. "Fatigue Crack Growth Law Covering Threshold and Fracture Toughness for Railway LZ50 Axle Steel." Advanced Materials Research 544 (June 2012): 280–85. http://dx.doi.org/10.4028/www.scientific.net/amr.544.280.

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Long fatigue crack growth rate (FCGR) model covering the range from threshold to fracture toughness is investigated through a series of experiments on the fatigue crack growth behaviour during nearby the threshold district of stage I, steady growth stage II, and the toughness of railway LZ50 axle steel. It reveals that test data in stage II can be reasonably described by employing a statistical distribution for the FCGR data at a given stress intensity factor range level. While the test data nearby the threshold district can be appropriately characterized using a statistical distribution for the factor range data at a given FCGR level and the case is similarly for the test toughness data. Therefore, the model is constructed using the test data in stage II under a control of the statistical parameters of threshold and toughness data on a principle of concurrent probabilities. Availability is indicated by the modeled result for the present material.
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36

Zehnder, Alan T., and Ares J. Rosakis. "Experimental Measurement of the Temperature Rise Generated During Dynamic Crack Growth in Metals." Applied Mechanics Reviews 43, no. 5S (May 1, 1990): S260—S265. http://dx.doi.org/10.1115/1.3120822.

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During the high speed propagation of cracks, large temperature increases occur at the crack tip due to the intense dissipation of plastic work there. This increased temperature may have a significant effect of the material’s dynamic fracture toughness. An experimental investigation of the temperature fields at the tip of dynamically propagating cracks in 4340 steel was performed using a focused array of high speed, infrared detectors. Temperature fields were measured for cracks growing at speeds from 700m/s to 1900m/s. Maximum temperature increases were as high as 465°C. The temperature fields were differentiated to determine the plastic work rate distribution at the crack tip and to estimate the plastic strain rate. Effects of crack tip heating on dynamic fracture toughness are discussed.
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37

Perez Velasquez, C., D. Avendano Rodriguez, C. Narvaez Tovar, L. Mujica Roncery, and R. Rodríguez Baracaldo. "Fatigue Crack Growth and Fracture Toughness in a Dual Phase Steel: Effect of Increasing Martensite Volume Fraction." International Journal of Automotive and Mechanical Engineering 17, no. 3 (October 6, 2020): 8086–95. http://dx.doi.org/10.15282/ijame.17.3.2020.02.0606.

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Crack growth resistance in dual-phase steel was studied. The dual phase steel microstructure was modified through heat treatments to increase the martensite volume fraction from 10% to 40%. The as-received and heat-treated samples were evaluated using a uniaxial tensile test, fatigue crack growth test, and fracture toughness test. Extended Finite Element Method (XFEM) was used to simulate the crack growth in compact tension test specimens. The results showed that an increase in martensite volume fraction is an effective way to increase the fracture resistance under different load conditions, quasistatics and dynamic, increasing the fracture toughness, tensile strength and fatigue resistance of the heat-treated material. Presence of a highest content of martensite results in formation of an important number of secondary cracks during the fatigue crack growth, which slow down the crack propagation. Moreover, martensite generates a crack closure over the crack tip, making the propagation difficult due to the irregularities caused by the crack growth on the martensite. Finally, the computational load-displacement curves are in good agreement with the experimental data.
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38

Wojteczko, Agnieszka, Radosław Lach, Kamil Wojteczko, Paweł Rutkowski, Dariusz Zientara, and Zbigniew Pędzich. "Subcritical crack growth in oxide and non-oxide ceramics using the constant stress rate test." Processing and Application of Ceramics 9, no. 4 (2015): 187–91. http://dx.doi.org/10.2298/pac1504187w.

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Fracture toughness is one of the most important parameters for ceramics description. In some cases, material failure occurs at lower stresses than described by KIc parameter. In these terms, determination of fracture toughness only, proves to be insufficient. This may be due to environmental factors, such as humidity, which might cause subcritical crack propagation in a material. Therefore, it is very important to estimate crack growth velocities to predict lifetime of ceramics used under specific conditions. Constant Stress Rate Test is an indirect method of subcritical crack growth parameters estimation. Calculations are made by using strength data, thus avoiding crack measurement. The expansion of flaws causes reduction of material strength. If subcritical crack growth phenomenon occurs, critical value of crack lengths increases with decreasing stress rate due to longer time for flaw to grow before the critical crack propagation at KIc takes place. Subcritical crack growth phenomenon is particularly dangerous for oxide ceramics due to chemical interactions occurring as a result of exposure to humidity. This paper presents results of Constant Stress Rate Test performed for alumina, zirconia, silicon carbide and silicon nitride in order to demonstrate the differences in subcritical crack propagation phenomenon course.
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39

KAWAGUCHI, Yoshiaki, Yoshiaki YAMADE, and Teruo KISHI. "Fracture toughness evaluation of mullite with respect to slow crack growth." Journal of the Society of Materials Science, Japan 40, no. 451 (1991): 477–82. http://dx.doi.org/10.2472/jsms.40.477.

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40

Sajuri, Z., N. A. Alang, Nur Azhani Abd Razak, and M. A. Aziman. "Fracture Toughness and Fatigue Crack Growth Behavior of Rail Track Material." Key Engineering Materials 462-463 (January 2011): 1109–14. http://dx.doi.org/10.4028/www.scientific.net/kem.462-463.1109.

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Fracture toughness KC and fatigue crack growth behavior of commuter train’s rail track material used in Klang Valley, Malaysia was investigated. Two different tests were performed in accordance to ASTM E399 and E647 testing procedures using single edge notch bend (SENB) and compact tension (CT) specimens, respectively. The results showed that the average KC value of the rail track material was 51.7 MPa√m. On the other hand, from the fatigue crack growth test, both longitudinal (LD) and short-transverse (TD) direction specimens demonstrated identical Paris’ Law constants C and m of 1.3 x 10-12 m/cycle and 3.54, respectively. Prediction of bending fatigue life of rail track material using the above obtained parameters showed a good agreement with the experimental results.
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41

Hwu, K. L., and B. Derby. "Fracture of metal/ceramic laminates—II. Crack growth resistance and toughness." Acta Materialia 47, no. 2 (January 1999): 545–63. http://dx.doi.org/10.1016/s1359-6454(98)00358-9.

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42

Maugis, D. "Subcritical crack growth, surface energy, fracture toughness, stick-slip and embrittlement." Journal of Materials Science 20, no. 9 (September 1985): 3041–73. http://dx.doi.org/10.1007/bf00545170.

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43

Manoharan, M., and J. J. Lewandowski. "Crack initiation and growth toughness of an aluminum metal-matrix composite." Acta Metallurgica et Materialia 38, no. 3 (March 1990): 489–96. http://dx.doi.org/10.1016/0956-7151(90)90155-a.

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44

Cady, Carl M., and Cheng Liu. "Determination of fracture toughness using the compression fracture technique." EPJ Web of Conferences 250 (2021): 01026. http://dx.doi.org/10.1051/epjconf/202125001026.

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Many engineering materials of importance can be mechanically characterized as brittle or quasi-brittle solids. Examples include many hard polymers, ceramic composites, and low ductility metals. Fracture toughness is the measure of crack extension as a function of applied load and the resistance of the deforming material to the advance of cracking. In this investigation we use digital image correlation (DIC) for observing and studying the process of macroscopic crack initiation and propagation, and applied linear elastic fracture mechanics (LEFM) to determine the fracture toughness of these materials. We will address issues such as loading configuration for stable crack growth, diagnostics for identifying crack initiation and quantifying the extent of crack growth, and scheme for extracting the stress intensity factor at the moving crack tip. The technique described in this report has been applied to many different materials, but for the purpose of illustrating the application of the technique and data processing scheme, we choose the following materials: graphite and beryllium as materials described in this paper. This technique can be used at any rate with the only limitation being the resolution and rate at which images can be captured.
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45

Rasel, Sheikh Md, Foisal Ahmed Mirza, Ali Md Afsar, and Jung I. Song. "Evaluation of Fracture Toughness of Ceramic-Metal Functionally Graded Materials." Advanced Materials Research 123-125 (August 2010): 971–74. http://dx.doi.org/10.4028/www.scientific.net/amr.123-125.971.

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The main objective of this study is to examine the two dimensional surface crack problems in a system with an interface between two elastic-plastic solids of different yield strength subjected to mode I mechanical loading. The surface cracks growth is considered to occure along the interface direction of bimaterials which is perfectly bonded to each others. A two dimensional finite elementmethod is used to solve the structural problem. Solid 183-node elements are utilized to simulate the strain singularity around the crack front. The crack surface is subjected to a compressive load by three point bending. The stress intesity factors are computed by using the displacement correlation technique. The primary goal is to develop a model crack tip stresses and strains in a manner that is useful for crack growth initiation and propagation in a FGM.
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46

Morrison, J., and C. H. Laforce. "Fatigue Crack Growth Rate Testing of Gun Steels." Journal of Pressure Vessel Technology 108, no. 4 (November 1, 1986): 507–13. http://dx.doi.org/10.1115/1.3264821.

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The experimental measurement of fatigue crack growth rates is an integral part of the fracture mechanics approach to safe life estimation in structures subjected to cyclical loading. To assess the variation in crack growth properties, data has been collected from five different gun steels from various sources. The experimental, analytical and statistical techniques are described, and an assessment is made of the applicability of a single growth rate expression. There are significant differences in strength, toughness and extent of autofrettage between these gun steels, and a correspondingly wide range of fatigue crack growth rates has been encountered.
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47

Ager, J. W., G. Balooch, and R. O. Ritchie. "Fracture, aging, and disease in bone." Journal of Materials Research 21, no. 8 (August 1, 2006): 1878–92. http://dx.doi.org/10.1557/jmr.2006.0242.

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From a public health perspective, developing a detailed mechanistic understanding of the well-known increase with age in fracture risk of human bone is essential. This also represents a challenge from materials science and fracture mechanics viewpoints. Bone has a complex, hierarchical structure with characteristic features ranging from nanometer to macroscopic dimensions; it is therefore significantly more complex than most engineering materials. Nevertheless, by examining the micro-/nanostructural changes accompanying the process of aging using appropriate multiscale experimental methods and relating them to fracture mechanics data, it is possible to obtain a quantitative picture of how bone resists fracture. As human cortical bone exhibits rising ex vivo crack-growth resistance with crack extension, its fracture toughness must be evaluated in terms of resistance-curve (R-curve) behavior. While the crack initiation toughness declines with age, the more striking finding is that the crack-growth toughness declines even more significantly and is essentially absent in bone from donors exceeding 85 years in age. To explain such an age-induced deterioration in the toughness of bone, we evaluate its fracture properties at multiple length scales, specifically at the molecular and nano dimensions using vibrational spectroscopies, at the microscale using electron microscopy and hard/soft x-ray computed tomography, and at the macroscale using R-curve measurements. We show that the reduction in crack-growth toughness is associated primarily with a degradation in the degree of extrinsic toughening, in particular involving crack bridging, and that this occurs at relatively coarse size scales in the range of tens to hundreds of micrometers. Finally, we briefly describe how specific clinical treatments, e.g., with steroid hormones to treat various inflammatory conditions, can prematurely damage bone, thereby reducing its fracture resistance, whereas regulating the level of the cytokine Transforming Growth Factor-β can offer significant improvements in the stiffness, strength, and toughness of bone and as such may be considered a therapeutic target to treat increased bone fragility induced by aging, drugs, and disease.
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48

Miyazaki, Hiroyuki, Hideki Hyuga, Yuichi Yoshizawa, Kiyoshi Hirao, and Tatsuki Ohji. "Measurement of Indentation Fracture Toughness of Silicon Nitride Ceramics: II, Effect of the Experimental Conditions." Key Engineering Materials 352 (August 2007): 45–48. http://dx.doi.org/10.4028/www.scientific.net/kem.352.45.

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The influence of two measuring conditions, the elapsed time after indentation and the condition of edge of an indenter, on the indentation fracture toughness of silicon nitrides was assessed. No slow crack-growth after unloading was confirmed by optical microscopic observation of a crack tip induced by the indentation, which led to the negligible difference in fracture toughness measured at 1 and 30 min after the indentation. Measurements with relatively new and used indenters gave almost the same fracture toughness data, indicating that the crack lengths were hardly affected by the slight damage of the corner of the indenter. It was suggested that the large scattering of the indentation fracture toughness reported by the round-robin tests such as VAMAS was not originated from these factors.
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49

Chao, L. Y., D. Singh, and D. K. Shetty. "Effects of Subcritical Crack Growth on Fracture Toughness of Ceramics Assessed in Chevron-Notched Three-Point Bend Tests." Journal of Engineering for Gas Turbines and Power 111, no. 1 (January 1, 1989): 168–73. http://dx.doi.org/10.1115/1.3240219.

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Chevron-notched bend specimens in three-point loading are increasingly used for evaluation of fracture toughness of structural ceramics. Its advantages include stable precracking of the specimen during loading, a simple specimen geometry, and a compressive mode of loading that is convenient for testing ceramics at elevated temperatures. Subcritical crack growth caused by environmental interactions or mass transport phenomena at elevated temperatures, however, can affect the apparent fracture toughness measured. A numerical computational study was carried out to assess the effects of subcritical crack growth on crack stability in the chevron-notched three-point bend specimens. A power-law relationship between the sub-critical crack velocity (v) and the applied stress intensity (KI) was used along with compliance and stress-intensity relationships for the chevron-notched bend specimen to calculate the load response under fixed deflection rate and a machine compliance. The results indicate that the maximum load during the test occurs at the same crack length for all the deflection rates; the maximum load, however, is dependent on the deflection rate for rates below a critical rate. The resulting dependence of the apparent fracture toughness on the deflection rate is compared to experimental results on soda-lime glass and polycrystalline alumina.
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50

Xu, Jie, Wei Song, Wenfeng Cheng, Lingyu Chu, Hanlin Gao, Pengpeng Li, and Filippo Berto. "Modelling of Fracture Toughness of X80 Pipeline Steels in DTB Transition Region Involving the Effect of Temperature and Crack Growth." Metals 10, no. 1 (December 23, 2019): 28. http://dx.doi.org/10.3390/met10010028.

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This work presents an investigation of the effects of temperature and crack growth on cleavage fracture toughness for weld thermal simulated X80 pipeline steels in the ductile-to-brittle transition (DBT) regime. A great bulk of fracture toughness (crack tip opening displacement—CTOD) tests and numerical simulations are carried out by deep-cracked single-edge-notched bending (SENB) and shallow-cracked single-edge-notched tension (SENT) specimens at various temperatures (−90 °C, −60 °C, −30 °C, and 0 °C). Three-dimensional (3D) finite element (FE) models of tested specimens have been employed to obtain computational data. The results show that temperature exerts only a slight effect on the material hardening behavior, which indicates the crack tip constraint (as denoted by Q-parameter) is less dependent on the temperature. The measured CTOD-values give considerable scatter but confirm well-established trends of increasing toughness with increasing temperature and reducing constraint. Crack growth and 3D effect exhibited significant influences on CTOD-CMOD relations at higher temperatures, −30 °C and 0 °C for the SENT specimen.
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