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A. T. Samaei - One of the best experts on this subject based on the ideXlab platform.
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a finite element study on the Fracture Initiation at the zirconia veneer interface an application in dental materials
Engineering Solid Mechanics, 2015Co-Authors: Mirmilad Mirsayar, A. T. SamaeiAbstract:Article history: Received 6 April, 2015 Accepted 20 July 2015 Available online 23 July 2015 Zirconia/ veneer bi-layered components are extensively used in dental restoration technology to improve resistance of tooth’s surface from decay. The direction of the Fracture propagation at the interface of zirconia and veneer is investigated in this paper. Finite element analysis is performed on a bi-material four point bend specimen in different geometries, and the Fracture Initiation angle is obtained using maximum tangential stress (MTS) criterion. The effect of specimen geometry on the Fracture Initiation angle is discussed. Because an interface crack may propagate through interface or kink into one of the materials, some comments are given to determine under which condition “interface de-bounding” will be happened. © 2015 Growing Science Ltd. All rights reserved.
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on Fracture Initiation angle near bi material notches effects of first non singular stress term
Engineering Fracture Mechanics, 2014Co-Authors: Mirmilad Mirsayar, M.r.m. Aliha, A. T. SamaeiAbstract:Abstract The effect of first non-singular stress term of elastic stress field near bi-material notches (I-stress) on the Fracture Initiation angle is investigated. A modified maximum tangential stress (MMTS) criterion is suggested for predicting the Fracture Initiation angles which takes into account the effect of I-stress as well as the singular terms. It is shown that the I-stress can play an important role in Fracture Initiation behavior adjacent the interface corners and neglecting this term may introduce significant errors in predicting the Fracture Initiation angle. Then, to evaluate the proposed criterion, a finite element (FE) simulation is done on a typical test specimen and the presented criterion is applied for predicting the Fracture Initiation direction. It was observed that the MMTS predictions are very close to the results obtained from the FE analysis (which takes into account all stress terms) showing the reasonable accuracy of the MMTS criterion for bi-material notch problems.
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Application of maximum tangential stress criterion in determination of Fracture Initiation angles of silicon/ glass anodic bonds
Engineering Solid Mechanics, 2014Co-Authors: Mirmilad Mirsayar, A. T. SamaeiAbstract:Article history: Received January 25, 2014 Received in Revised form May, 10, 2014 Accepted 7 June 2014 Available online 9 June 2014 Silicon/glass bi-materials are used in micro-assembly and packaging of microelectromechanical systems (MEMS) and micro-electronics devices. In this paper, maximum tangential stress (MTS) concept is used for determination of the Fracture Initiation angles of silicon/ glass bi-material notches. First, the MTS criterion is analytically formulated for a bimaterial notch problem. Then, the criterion used for prediction of Fracture Initiation angles of some experimental data given in literature for silicon/ glass bi-material notches. In addition, the modified MTS (MMTS) criterion, which considers the effect of I-stress, was compared with the MTS criterion and the experimental data. It was shown that MMTS criterion provides more accurate results than the MTS criterion for estimation of the Fracture Initiation angle. © 2014 Growing Science Ltd. All rights reserved.
Michihiko Nagumo - One of the best experts on this subject based on the ideXlab platform.
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brittle Fracture Initiation associated with the strain localization in a heat affected zone of a low carbon steel
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 1998Co-Authors: Ken Ichi Yokoyama, Michihiko NagumoAbstract:Brittle Fracture Initiation in the ductile-brittle Fracture transition region in the heat-affected zone (HAZ) of weldments of a low carbon steel has been investigated. Consistent with the previous results from blunt notch Charpy tests, brittle Fracture Initiation was observed in the case of J-integral tests to take place at the intersection of small bainitic ferrite grains of different orientations within a mixed area of bainitic ferrite and quasipolygonal ferrite in proximity to the boundary between a coarse bainitic ferrite. Partial load drop during loading, pop-in phenomena, in Fracture mechanics tests in the low-temperature region is caused by essentially the same mechanism as for unstable brittle Fracture Initiation. Inhomogeneous microstructure in the HAZ gives rise to intense strain localizations in the mixed area of bainitic ferrite and quasipolygonal ferrite due to the constraint of plastic deformation therein and may produce accumulated defects that form an incipient crack for the brittle Fracture. Partial load drop proceeds in association with repetitive Initiations of brittle facets and their ductile linking. The strong temperature dependence of the magnitude of partial load drop is likely to show that the temperature dependence of the brittle Fracture Initiation is controlled by the first Initiation of a brittle facet and the ductile linking with the following induced facets. Existence of coarse bainitic ferrite grains is a prerequisite for the extension of an incipient crack.
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brittle Fracture Initiation in low carbon steels at the ductile brittle transition temperature region
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 1994Co-Authors: M Koide, A Kikuchi, T Yagi, Michihiko NagumoAbstract:Abstract The Fracture process that determines the temperature dependence of toughness at the ductile-brittle transition was investigated for low carbon steels. It was revealed that the resistance against the stretch zone at the crack tip and the stable crack extensions is temperature independent while it depends on the carbon content. Applicability of elastic-plastic analyses of the crack tip fields was examined in terms of the relationship between J integral value normalized by the flow stress and crack opening displacement. Temperature dependence of toughness is determined primarily by the brittle Fracture Initiation. Locations of the Initiation sites were revealed to coincide with the maximum stress triaxiality rather than the maximum tensile stress. It was suggested that the brittle Fracture is caused by the deformation-induced Initiation and triaxial stress assisted growth of an incipient crack.
Douglas A. Scarth - One of the best experts on this subject based on the ideXlab platform.
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Effects of curvature on ductile Fracture Initiation in curved compact tension specimens of hydrided irradiated Zr-2.5Nb materials with split circumferential hydrides
Engineering Fracture Mechanics, 2019Co-Authors: Shin Jang Sung, Jwo Pan, Sterling St Lawrence, Douglas A. ScarthAbstract:Abstract The effects of curvature on K, J, plastic zone, near-tip stress and Fracture Initiation in curved compact tension (CCT) specimens of unhydrided and hydrided irradiated Zr-2.5Nb materials are determined by three-dimensional finite element analyses. Based on a strain-based failure criterion, the Fracture Initiation load for unhydrided CCT specimens is slightly lower than those for unhydrided compact tension (CT) and pressure tube (PT) specimens. For hydrided specimens, the reductions of Fracture Initiation loads for CT, CCT and PT specimens are similar. The fractions of Fracture Initiation loads for hydrided specimens are about 60–70% of those for unhydrided specimens.
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ductile Fracture Initiation near axial crack fronts in pressure tubes of hydrided irradiated zr 2 5nb materials with split circumferential hydrides
Engineering Fracture Mechanics, 2017Co-Authors: Shin Jang Sung, Jwo Pan, Poh Sang Lam, Douglas A. ScarthAbstract:Abstract Ductile Fracture Initiation with consideration of strain concentration and stress triaxiality near axial crack fronts in pressure tube (PT) specimens of hydrided irradiated Zr-2.5Nb materials with split circumferential hydrides is examined by three-dimensional finite element analyses with submodeling. For a PT specimen with split circumferential hydrides, strain concentration occurs in the middle of the ligaments ahead of the crack front. The computational results suggest that only 60–70% of the internal pressure for Fracture Initiation of an unhydrided irradiated PT specimen is needed to Fracture a hydrided irradiated PT specimen with many split circumferential hydrides along the crack front.
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Ductile Fracture Initiation with consideration of strain concentration and stress triaxiality near crack fronts in compact tension specimens of hydrided irradiated Zr-2.5Nb materials with split circumferential hydrides
Engineering Fracture Mechanics, 2017Co-Authors: Shin Jang Sung, Jwo Pan, Poh Sang Lam, Douglas A. ScarthAbstract:Abstract Ductile Fracture Initiation with consideration of strain concentration and stress triaxiality near crack fronts in compact tension specimens of hydrided irradiated Zr-2.5Nb materials with split circumferential hydrides is investigated by three-dimensional finite element analyses. The results indicate that plastic strain concentration is observed in the middle of the ligaments ahead of the crack front. A strain-based failure criterion with consideration of stress triaxiality is developed from the Gurson yield model. With the failure criterion, the necessary fraction of the load for crack Initiation is about 0.60–0.70 to Fracture the ligaments when compared to that for a CT specimen without split circumferential hydrides.
M.r.m. Aliha - One of the best experts on this subject based on the ideXlab platform.
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on Fracture Initiation angle near bi material notches effects of first non singular stress term
Engineering Fracture Mechanics, 2014Co-Authors: Mirmilad Mirsayar, M.r.m. Aliha, A. T. SamaeiAbstract:Abstract The effect of first non-singular stress term of elastic stress field near bi-material notches (I-stress) on the Fracture Initiation angle is investigated. A modified maximum tangential stress (MMTS) criterion is suggested for predicting the Fracture Initiation angles which takes into account the effect of I-stress as well as the singular terms. It is shown that the I-stress can play an important role in Fracture Initiation behavior adjacent the interface corners and neglecting this term may introduce significant errors in predicting the Fracture Initiation angle. Then, to evaluate the proposed criterion, a finite element (FE) simulation is done on a typical test specimen and the presented criterion is applied for predicting the Fracture Initiation direction. It was observed that the MMTS predictions are very close to the results obtained from the FE analysis (which takes into account all stress terms) showing the reasonable accuracy of the MMTS criterion for bi-material notch problems.
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Analysis of Fracture Initiation angle in some cracked ceramics using the generalized maximum tangential stress criterion
International Journal of Solids and Structures, 2012Co-Authors: M.r.m. Aliha, Majid R. AyatollahiAbstract:Abstract Brittle Fracture in ceramics sometimes occurs under combined opening-sliding (or mixed mode I/II) crack deformation. In this paper, a generalized maximum tangential stress criterion is employed for predicting the Fracture Initiation angle under mixed mode I/II loading in some brittle ceramics including alumina, zirconia, soda lime glass and three silicon based ceramics. The experimental results reported for the Fracture angles in these ceramics have been obtained from Fracture tests on the centrally cracked circular disc (often called the Brazilian disc). Very good agreement is shown to exist between the experimental results and the theoretical predictions. According to the Fracture model, the mixed mode Fracture angle is strongly dependent on the elastic T-stress in the tested ceramics. The negative T-stress that exists in the Brazilian disc specimen can be the main influencing parameter for decreasing the Fracture Initiation angle in the investigated ceramics.
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geometry and size effects on Fracture trajectory in a limestone rock under mixed mode loading
Engineering Fracture Mechanics, 2010Co-Authors: M.r.m. Aliha, M R Ayatollahi, D J Smith, Martyn J PavierAbstract:The mixed mode I/II Fracture Initiation angle and the crack growth trajectory of a soft rock (Guiting limestone) were investigated experimentally and theoretically for two different shaped test specimens with various sizes. It was observed that for similar mode mixities in the two specimens, the Fracture paths grew in two different trajectories. It is shown that the observed crack path and the Fracture Initiation angle can be predicted theoretically by using a generalized form of the maximum tangential stress criterion. The main difference in the Fracture Initiation angles was found to be related to the magnitude and sign of the T-stress.
Mirmilad Mirsayar - One of the best experts on this subject based on the ideXlab platform.
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a finite element study on the Fracture Initiation at the zirconia veneer interface an application in dental materials
Engineering Solid Mechanics, 2015Co-Authors: Mirmilad Mirsayar, A. T. SamaeiAbstract:Article history: Received 6 April, 2015 Accepted 20 July 2015 Available online 23 July 2015 Zirconia/ veneer bi-layered components are extensively used in dental restoration technology to improve resistance of tooth’s surface from decay. The direction of the Fracture propagation at the interface of zirconia and veneer is investigated in this paper. Finite element analysis is performed on a bi-material four point bend specimen in different geometries, and the Fracture Initiation angle is obtained using maximum tangential stress (MTS) criterion. The effect of specimen geometry on the Fracture Initiation angle is discussed. Because an interface crack may propagate through interface or kink into one of the materials, some comments are given to determine under which condition “interface de-bounding” will be happened. © 2015 Growing Science Ltd. All rights reserved.
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on Fracture Initiation angle near bi material notches effects of first non singular stress term
Engineering Fracture Mechanics, 2014Co-Authors: Mirmilad Mirsayar, M.r.m. Aliha, A. T. SamaeiAbstract:Abstract The effect of first non-singular stress term of elastic stress field near bi-material notches (I-stress) on the Fracture Initiation angle is investigated. A modified maximum tangential stress (MMTS) criterion is suggested for predicting the Fracture Initiation angles which takes into account the effect of I-stress as well as the singular terms. It is shown that the I-stress can play an important role in Fracture Initiation behavior adjacent the interface corners and neglecting this term may introduce significant errors in predicting the Fracture Initiation angle. Then, to evaluate the proposed criterion, a finite element (FE) simulation is done on a typical test specimen and the presented criterion is applied for predicting the Fracture Initiation direction. It was observed that the MMTS predictions are very close to the results obtained from the FE analysis (which takes into account all stress terms) showing the reasonable accuracy of the MMTS criterion for bi-material notch problems.
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Application of maximum tangential stress criterion in determination of Fracture Initiation angles of silicon/ glass anodic bonds
Engineering Solid Mechanics, 2014Co-Authors: Mirmilad Mirsayar, A. T. SamaeiAbstract:Article history: Received January 25, 2014 Received in Revised form May, 10, 2014 Accepted 7 June 2014 Available online 9 June 2014 Silicon/glass bi-materials are used in micro-assembly and packaging of microelectromechanical systems (MEMS) and micro-electronics devices. In this paper, maximum tangential stress (MTS) concept is used for determination of the Fracture Initiation angles of silicon/ glass bi-material notches. First, the MTS criterion is analytically formulated for a bimaterial notch problem. Then, the criterion used for prediction of Fracture Initiation angles of some experimental data given in literature for silicon/ glass bi-material notches. In addition, the modified MTS (MMTS) criterion, which considers the effect of I-stress, was compared with the MTS criterion and the experimental data. It was shown that MMTS criterion provides more accurate results than the MTS criterion for estimation of the Fracture Initiation angle. © 2014 Growing Science Ltd. All rights reserved.
