The Experts below are selected from a list of 8955 Experts worldwide ranked by ideXlab platform

Nobuhisa Suzuki - One of the best experts on this subject based on the ideXlab platform.

  • crack geometry effect on stress strain fields for crack under Biaxial Loading
    Journal of Pressure Vessel Technology-transactions of The Asme, 2010
    Co-Authors: Fumiyoshi Minami, Daisuke Watanabe, Takahiro Kubo, Mitsuru Ohata, Nobuhisa Suzuki
    Abstract:

    With increasing demand of high-strength and high-pressure pipelines in gas transmission industries, the fracture control design of pipelines has been a driving factor to ensure the integrity of the pipeline. This paper addresses the stress and strain fields for a crack in a wide plate component under Biaxial Loading, which simulates a large-diameter pipe subjected to inner pressure coupled with axial Loading. Attention is focused on the initiation of brittle fracture (stress controlled type) as well as ductile fracture (strain controlled type). Three-dimensional finite element-analyses are conducted. It was found that Biaxial Loading has a significant effect on the stress fields of through-thickness crack; the near-crack-tip stress is elevated to a large extent by Biaxial Loading. By contrast, the stress field for a surface crack is not sensitive to Biaxial Loading, while the near-crack-tip stress at the crack corner is increased locally by Biaxial Loading. The Weibull stress criterion was applied to discuss the Biaxial Loading effect on the brittle fracture strength of the wide plate. Ductile crack initiation properties are also discussed with two-parameter (plastic strain and stress triaxiality) diagram. The ductile damage is increased by Biaxial Loading for a through-thickness crack, whereas a surface crack has little effect of Biaxial Loading on the ductile damage.

  • crack geometry effect on stress strain fields for crack under Biaxial Loading
    2008 7th International Pipeline Conference Volume 3, 2008
    Co-Authors: Fumiyoshi Minami, Daisuke Watanabe, Takahiro Kubo, Mitsuru Ohata, Nobuhisa Suzuki
    Abstract:

    With increasing demand of high strength and high pressure pipelines in gas transmission industries, the fracture control design of pipelines has been driven primarily. This paper addresses the stress and strain fields for a crack in a wide plate component under Biaxial Loading, which simulates a large diameter pipe subjected to inner pressure coupled with axial Loading. Three-dimensional FE-analyses are conducted. It was found that Biaxial Loading has a significant effect on the stress fields of through-thickness crack; the near crack-tip stress is elevated to a large extent by Biaxial Loading. By contrast, the stress field for a surface crack is not sensitive to Biaxial Loading, while the near crack-tip stress at the crack corner is increased locally by Biaxial Loading. The Weibull stress criterion was applied to discuss the Biaxial Loading effect on the brittle fracture strength of the wide plate. Ductile crack initiation properties are also discussed with two-parameter (plastic strain and stress triaxiality) diagram. The ductile damage is increased by Biaxial Loading for a through-thickness crack, whereas a surface crack has little effect of Biaxial Loading on the ductile damage.Copyright © 2008 by ASME

  • crack geometry effect on stress strain fields for crack under Biaxial Loading
    2008 7th International Pipeline Conference Volume 3, 2008
    Co-Authors: Fumiyoshi Minami, Daisuke Watanabe, Takahiro Kubo, Mitsuru Ohata, Nobuhisa Suzuki
    Abstract:

    With increasing demand of high strength and high pressure pipelines in gas transmission industries, the fracture control design of pipelines has been driven primarily. This paper addresses the stress and strain fields for a crack in a wide plate component under Biaxial Loading, which simulates a large diameter pipe subjected to inner pressure coupled with axial Loading. Three-dimensional FE-analyses are conducted. It was found that Biaxial Loading has a significant effect on the stress fields of through-thickness crack; the near crack-tip stress is elevated to a large extent by Biaxial Loading. By contrast, the stress field for a surface crack is not sensitive to Biaxial Loading, while the near crack-tip stress at the crack corner is increased locally by Biaxial Loading. The Weibull stress criterion was applied to discuss the Biaxial Loading effect on the brittle fracture strength of the wide plate. Ductile crack initiation properties are also discussed with two-parameter (plastic strain and stress triaxiality) diagram. The ductile damage is increased by Biaxial Loading for a through-thickness crack, whereas a surface crack has little effect of Biaxial Loading on the ductile damage.Copyright © 2008 by ASME

Fumiyoshi Minami - One of the best experts on this subject based on the ideXlab platform.

  • crack geometry effect on stress strain fields for crack under Biaxial Loading
    Journal of Pressure Vessel Technology-transactions of The Asme, 2010
    Co-Authors: Fumiyoshi Minami, Daisuke Watanabe, Takahiro Kubo, Mitsuru Ohata, Nobuhisa Suzuki
    Abstract:

    With increasing demand of high-strength and high-pressure pipelines in gas transmission industries, the fracture control design of pipelines has been a driving factor to ensure the integrity of the pipeline. This paper addresses the stress and strain fields for a crack in a wide plate component under Biaxial Loading, which simulates a large-diameter pipe subjected to inner pressure coupled with axial Loading. Attention is focused on the initiation of brittle fracture (stress controlled type) as well as ductile fracture (strain controlled type). Three-dimensional finite element-analyses are conducted. It was found that Biaxial Loading has a significant effect on the stress fields of through-thickness crack; the near-crack-tip stress is elevated to a large extent by Biaxial Loading. By contrast, the stress field for a surface crack is not sensitive to Biaxial Loading, while the near-crack-tip stress at the crack corner is increased locally by Biaxial Loading. The Weibull stress criterion was applied to discuss the Biaxial Loading effect on the brittle fracture strength of the wide plate. Ductile crack initiation properties are also discussed with two-parameter (plastic strain and stress triaxiality) diagram. The ductile damage is increased by Biaxial Loading for a through-thickness crack, whereas a surface crack has little effect of Biaxial Loading on the ductile damage.

  • crack geometry effect on stress strain fields for crack under Biaxial Loading
    2008 7th International Pipeline Conference Volume 3, 2008
    Co-Authors: Fumiyoshi Minami, Daisuke Watanabe, Takahiro Kubo, Mitsuru Ohata, Nobuhisa Suzuki
    Abstract:

    With increasing demand of high strength and high pressure pipelines in gas transmission industries, the fracture control design of pipelines has been driven primarily. This paper addresses the stress and strain fields for a crack in a wide plate component under Biaxial Loading, which simulates a large diameter pipe subjected to inner pressure coupled with axial Loading. Three-dimensional FE-analyses are conducted. It was found that Biaxial Loading has a significant effect on the stress fields of through-thickness crack; the near crack-tip stress is elevated to a large extent by Biaxial Loading. By contrast, the stress field for a surface crack is not sensitive to Biaxial Loading, while the near crack-tip stress at the crack corner is increased locally by Biaxial Loading. The Weibull stress criterion was applied to discuss the Biaxial Loading effect on the brittle fracture strength of the wide plate. Ductile crack initiation properties are also discussed with two-parameter (plastic strain and stress triaxiality) diagram. The ductile damage is increased by Biaxial Loading for a through-thickness crack, whereas a surface crack has little effect of Biaxial Loading on the ductile damage.Copyright © 2008 by ASME

  • crack geometry effect on stress strain fields for crack under Biaxial Loading
    2008 7th International Pipeline Conference Volume 3, 2008
    Co-Authors: Fumiyoshi Minami, Daisuke Watanabe, Takahiro Kubo, Mitsuru Ohata, Nobuhisa Suzuki
    Abstract:

    With increasing demand of high strength and high pressure pipelines in gas transmission industries, the fracture control design of pipelines has been driven primarily. This paper addresses the stress and strain fields for a crack in a wide plate component under Biaxial Loading, which simulates a large diameter pipe subjected to inner pressure coupled with axial Loading. Three-dimensional FE-analyses are conducted. It was found that Biaxial Loading has a significant effect on the stress fields of through-thickness crack; the near crack-tip stress is elevated to a large extent by Biaxial Loading. By contrast, the stress field for a surface crack is not sensitive to Biaxial Loading, while the near crack-tip stress at the crack corner is increased locally by Biaxial Loading. The Weibull stress criterion was applied to discuss the Biaxial Loading effect on the brittle fracture strength of the wide plate. Ductile crack initiation properties are also discussed with two-parameter (plastic strain and stress triaxiality) diagram. The ductile damage is increased by Biaxial Loading for a through-thickness crack, whereas a surface crack has little effect of Biaxial Loading on the ductile damage.Copyright © 2008 by ASME

  • Fracture Assessment of Wide Plate Component Subjected to Biaxial Loading
    Materials Science Forum, 2007
    Co-Authors: Hiroshi Shimanuki, Fumiyoshi Minami, Mitsuru Ohata
    Abstract:

    This study investigated the effect of Biaxial Loading on the fracture performance of a center through cracked panel and a center surface cracked panel of a structural steel of 25mm thick. The experiment revealed that the critical CTOD of the Biaxially loaded specimen was smaller than that of the uniaxially loaded specimen, due to the constraint effect of the Biaxial Loading. This constraint effect was remarkable in the case of the through thickness notched specimen. The stress distributions near the cracks and crack tip deformation behaviors were simulated by FE-analyses, in order to discuss brittle fracture initiation conditions of the cracked wide plate specimens. All fracture initiation points were located in the large CTOD part of the crack front, as well as in the widely extended high opening stress region. However, the initiation points did not always correspond to the highest opening stress point along the crack front. These results indicated that the existence of a extensive high stress region accompanied by a large CTOD, is significant in the brittle fracture initiation condition. These results also suggested that fracture assessment based on the Weibull stress criterion is reasonable, because the Weibull stress takes the volume effect of the high stress area into account.

W. J. Mcafee - One of the best experts on this subject based on the ideXlab platform.

  • shallow flaws under Biaxial Loading conditions part ii application of a weibull stress analysis of the cruciform bend specimen using a hydrostatic stress criterion
    Journal of Pressure Vessel Technology-transactions of The Asme, 2001
    Co-Authors: Paul T Williams, Richard B Bass, W. J. Mcafee
    Abstract:

    Cruciform beam fracture mechanics specimensl have been developed in the Heavy Section Steel Technology (HSST) Program at Oak Ridge National Laboratory (ORNL) to introduce a prototypic, far- field, out-of-plane biaxird bending stress component in the test section that approximates the nonlinear Biaxial stresses resulting from pressurized-thernxd-shock or pressure-temperature Loading of a nuclear reactor pressure vessel (RPV). Matrices of cruciform beam tests were developed to investigate and quantify the effects of temperature, Biaxial Loading, and specimen size on fracture initiation toughness of two-dimensional (constant depth), shtdlow, surface flaws. Tests were conducted under Biaxial load ratios ranging from uniaxial to equiBiaxial. These tests demonstrated that Biaxial Loading can have a pronounced effect on shallow-flaw fracture toughness in the lower transition temperature region for RPV materials. Two and three- parameter Weibull models have been calibrated using a new scheme (developed at the University of Illinois) that maps toughness data from test specimens with distinctly different levels of crack-tip constraint to a small scale yielding (SSY) Weibull stress space. These models, using the new hydrostatic stress criterion in place of the more commonly used maximum principal stress in the kernel of the OW integral definition, have been shown to correlate the experimentally observed biaxiaImore » effect in cruciform specimens, thereby providing a scaling mechanism between uniaxial and Biaxial Loading states.« less

  • application of the weibull methodology to a shallow flaw cruciform bend specimen tested under Biaxial Loading conditions
    ASTM special technical publications, 2000
    Co-Authors: Paul T Williams, B.r. Bass, W. J. Mcafee
    Abstract:

    This paper describes the application of the Weibull methodology to the analysis of a shallow-flaw cruciform bend specimen tested under Biaxial Loading conditions. The cruciform bend fracture mechanics specimen was developed at Oak Ridge National Laboratory (ORNL) to introduce a far-field, out-of-plane Biaxial bending stress component in the test section that approximates the nonlinear stresses resulting from pressurized-thermal-shock or pressure-temperature Loading of a nuclear reactor pressure vessel (RPV). Tests with the cruciform specimen demonstrated that Biaxial Loading can have a pronounced effect on shallow-flaw fracture toughness in the lower transition temperature region for an RPV material. High-constraint deep-flaw compact tension C(T) and low-constraint shallow-flaw cruciform fracture toughness data were used to assess the ability of the Weibull methodology to predict the observed effects of Biaxial Loading on shallow-flaw fracture toughness. A new hydrostatic stress criterion along with five equivalent-stress criteria from the literature were selected to serve as candidate kernels in the integral formulation of the Weibull stress. Among these candidates, the hydrostatic stress criterion, derived from the first invariant of the Cauchy stress tensor, was determined to have the required sensitivity to multiaxial-Loading states. In addition, a new calibration technique developed by researchers at the University of Illinois for determining the necessary Weibull parameters is applied to the C(T) and cruciform data. A three-parameter Weibull model based on the hydrostatic stress criterion is shown to predict the experimentally observed Biaxial effect on cleavage fracture toughness by providing a scaling mechanism between uniaxial and Biaxial Loading states. In summary, the conclusions that can be drawn from this study are as follows: (1) With respect to its effect on fracture toughness, the Biaxial effect is a constraint effect. (2) A Weibull statistical fracture model has been successfully calibrated with uniaxial toughness data obtained from a conventional high-constraint C(T) specimen and a uniaxially loaded shallow-flaw cruciform that is effectively equivalent to a conventional shallow-flaw SE(B) specimen. (3) The calibrated fracture model was able to successfully predict the intermediate constraint-loss effects associated with two levels of Biaxial Loading. (4) These preliminary results at a single test temperature offer encouragement that complex multiaxial Loading effects on transition region fracture toughness can be predicted with statistical fracture models developed using data obtained from conventional specimens. (5) Future work is required to investigate these effects at other temperatures within the transition region.

  • shallow flaws under Biaxial Loading conditions part ii application of a weibull stress analysis of the cruciform bend specimen using a hydrostatic stress criterion
    ASME Pressure Vessels and Piping Conference Boston MA August 1-5 1999, 1999
    Co-Authors: B.r. Bass, W. J. Mcafee, Paul T Williams
    Abstract:

    Cruciform beam fracture mechanics specimensl have been developed in the Heavy Section Steel Technology (HSST) Program at Oak Ridge National Laboratory (ORNL) to introduce a prototypic, far- field, out-of-plane biaxird bending stress component in the test section that approximates the nonlinear Biaxial stresses resulting from pressurized-thernxd-shock or pressure-temperature Loading of a nuclear reactor pressure vessel (RPV). Matrices of cruciform beam tests were developed to investigate and quantify the effects of temperature, Biaxial Loading, and specimen size on fracture initiation toughness of two-dimensional (constant depth), shtdlow, surface flaws. Tests were conducted under Biaxial load ratios ranging from uniaxial to equiBiaxial. These tests demonstrated that Biaxial Loading can have a pronounced effect on shallow-flaw fracture toughness in the lower transition temperature region for RPV materials. Two and three- parameter Weibull models have been calibrated using a new scheme (developed at the University of Illinois) that maps toughness data from test specimens with distinctly different levels of crack-tip constraint to a small scale yielding (SSY) Weibull stress space. These models, using the new hydrostatic stress criterion in place of the more commonly used maximum principal stress in the kernel of the OW integral definition, have been shown to correlate the experimentally observed biaxiaI effect in cruciform specimens, thereby providing a scaling mechanism between uniaxial and Biaxial Loading states.

  • Fracture assessment of shallow-flaw cruciform beams tested under uniaxial and Biaxial Loading conditions
    Nuclear Engineering and Design, 1999
    Co-Authors: B.r. Bass, W. J. Mcafee, Paul T Williams, W.e. Pennell
    Abstract:

    A technology to determine shallow-flaw fracture toughness of reactor pressure vessel (RPV) steels is being developed for application to the safety assessment of RPVs containing postulated shallow surface flaws. Matrices of cruciform beam tests were developed to investigate and quantify the effects of temperature, Biaxial Loading, and specimen size on fracture initiation toughness of two-dimensional (constant depth), shallow, surface flaws. The cruciform beam specimens were developed at Oak Ridge National Laboratory (ORNL) to introduce a far-field, out-of-plane Biaxial stress component in the test section that approximates the nonlinear stresses resulting from pressurized-thermal-shock or pressure–temperature Loading of an RPV. Tests were conducted under Biaxial load ratios ranging from uniaxial to equiBiaxial. These tests demonstrated that Biaxial Loading can have a pronounced effect on shallow-flaw fracture toughness in the lower transition temperature region for an RPV material. The cruciform fracture toughness data were used to evaluate fracture methodologies for predicting the observed effects of Biaxial Loading on shallow-flaw fracture toughness. Initial emphasis was placed on assessment of stress-based methodologies, namely, the J–Q formulation, the Dodds–Anderson toughness scaling model, and the Weibull approach. Applications of these methodologies based on the hydrostatic stress fracture criterion indicated an effect of Loading-Biaxiality on fracture toughness; the conventional maximum principal stress criterion indicated no effect. A three-parameter Weibull model based on the hydrostatic stress criterion is shown to correlate with the experimentally observed Biaxial effect on cleavage fracture toughness by providing a scaling mechanism between uniaxial and Biaxial Loading states.

  • evaluation of constraint methodologies applied to a shallow flaw cruciform bend specimen tested under Biaxial Loading conditions
    1998 ASME JSME joint pressure vessel and piping (PVP) conference San Diego CA (United States) 26-30 Jul 1998, 1998
    Co-Authors: B.r. Bass, W. J. Mcafee, Paul T Williams, W.e. Pennell
    Abstract:

    A technology to determine shallow-flaw fracture toughness of reactor pressure vessel (RPV) steels is being developed for application to the safety assessment of RPVs containing postulated shallow surface flaws. Matrices of cruciform beam tests were developed to investigate and quantify the effects of temperature, Biaxial Loading, and specimen size on fracture initiation toughness of two-dimensional (constant depth), shallow surface flaws. The cruciform beam specimens were developed at Oak Ridge National Laboratory (ORNL) to introduce a prototypic, far-field. out-of-plane Biaxial stress component in the test section that approximates the nonlinear stresses resulting from pressurized-thermal-shock or pressure-temperature Loading of an RPV. Tests were conducted under Biaxial load ratios ranging from uniaxial to equiBiaxial. These tests demonstrated that Biaxial Loading can have a pronounced effect on shallow-flaw fracture toughness in the lower transition temperature region for RPV materials. The cruciform fracture toughness data were used to evaluate fracture methodologies for predicting the observed effects of Biaxial Loading on shallow-flaw fracture toughness. Initial emphasis was placed on assessment of stress-based methodologies. namely, the J-Q formulation, the Dodds-Anderson toughness scaling model, and the Weibull approach. Applications of these methodologies based on the hydrostatic stress fracture criterion indicated an effect of Loading-Biaxiality on fracture toughness, the conventional maximum principal stress criterion indicated no effect.

Mitsuru Ohata - One of the best experts on this subject based on the ideXlab platform.

  • crack geometry effect on stress strain fields for crack under Biaxial Loading
    Journal of Pressure Vessel Technology-transactions of The Asme, 2010
    Co-Authors: Fumiyoshi Minami, Daisuke Watanabe, Takahiro Kubo, Mitsuru Ohata, Nobuhisa Suzuki
    Abstract:

    With increasing demand of high-strength and high-pressure pipelines in gas transmission industries, the fracture control design of pipelines has been a driving factor to ensure the integrity of the pipeline. This paper addresses the stress and strain fields for a crack in a wide plate component under Biaxial Loading, which simulates a large-diameter pipe subjected to inner pressure coupled with axial Loading. Attention is focused on the initiation of brittle fracture (stress controlled type) as well as ductile fracture (strain controlled type). Three-dimensional finite element-analyses are conducted. It was found that Biaxial Loading has a significant effect on the stress fields of through-thickness crack; the near-crack-tip stress is elevated to a large extent by Biaxial Loading. By contrast, the stress field for a surface crack is not sensitive to Biaxial Loading, while the near-crack-tip stress at the crack corner is increased locally by Biaxial Loading. The Weibull stress criterion was applied to discuss the Biaxial Loading effect on the brittle fracture strength of the wide plate. Ductile crack initiation properties are also discussed with two-parameter (plastic strain and stress triaxiality) diagram. The ductile damage is increased by Biaxial Loading for a through-thickness crack, whereas a surface crack has little effect of Biaxial Loading on the ductile damage.

  • crack geometry effect on stress strain fields for crack under Biaxial Loading
    2008 7th International Pipeline Conference Volume 3, 2008
    Co-Authors: Fumiyoshi Minami, Daisuke Watanabe, Takahiro Kubo, Mitsuru Ohata, Nobuhisa Suzuki
    Abstract:

    With increasing demand of high strength and high pressure pipelines in gas transmission industries, the fracture control design of pipelines has been driven primarily. This paper addresses the stress and strain fields for a crack in a wide plate component under Biaxial Loading, which simulates a large diameter pipe subjected to inner pressure coupled with axial Loading. Three-dimensional FE-analyses are conducted. It was found that Biaxial Loading has a significant effect on the stress fields of through-thickness crack; the near crack-tip stress is elevated to a large extent by Biaxial Loading. By contrast, the stress field for a surface crack is not sensitive to Biaxial Loading, while the near crack-tip stress at the crack corner is increased locally by Biaxial Loading. The Weibull stress criterion was applied to discuss the Biaxial Loading effect on the brittle fracture strength of the wide plate. Ductile crack initiation properties are also discussed with two-parameter (plastic strain and stress triaxiality) diagram. The ductile damage is increased by Biaxial Loading for a through-thickness crack, whereas a surface crack has little effect of Biaxial Loading on the ductile damage.Copyright © 2008 by ASME

  • crack geometry effect on stress strain fields for crack under Biaxial Loading
    2008 7th International Pipeline Conference Volume 3, 2008
    Co-Authors: Fumiyoshi Minami, Daisuke Watanabe, Takahiro Kubo, Mitsuru Ohata, Nobuhisa Suzuki
    Abstract:

    With increasing demand of high strength and high pressure pipelines in gas transmission industries, the fracture control design of pipelines has been driven primarily. This paper addresses the stress and strain fields for a crack in a wide plate component under Biaxial Loading, which simulates a large diameter pipe subjected to inner pressure coupled with axial Loading. Three-dimensional FE-analyses are conducted. It was found that Biaxial Loading has a significant effect on the stress fields of through-thickness crack; the near crack-tip stress is elevated to a large extent by Biaxial Loading. By contrast, the stress field for a surface crack is not sensitive to Biaxial Loading, while the near crack-tip stress at the crack corner is increased locally by Biaxial Loading. The Weibull stress criterion was applied to discuss the Biaxial Loading effect on the brittle fracture strength of the wide plate. Ductile crack initiation properties are also discussed with two-parameter (plastic strain and stress triaxiality) diagram. The ductile damage is increased by Biaxial Loading for a through-thickness crack, whereas a surface crack has little effect of Biaxial Loading on the ductile damage.Copyright © 2008 by ASME

  • Fracture Assessment of Wide Plate Component Subjected to Biaxial Loading
    Materials Science Forum, 2007
    Co-Authors: Hiroshi Shimanuki, Fumiyoshi Minami, Mitsuru Ohata
    Abstract:

    This study investigated the effect of Biaxial Loading on the fracture performance of a center through cracked panel and a center surface cracked panel of a structural steel of 25mm thick. The experiment revealed that the critical CTOD of the Biaxially loaded specimen was smaller than that of the uniaxially loaded specimen, due to the constraint effect of the Biaxial Loading. This constraint effect was remarkable in the case of the through thickness notched specimen. The stress distributions near the cracks and crack tip deformation behaviors were simulated by FE-analyses, in order to discuss brittle fracture initiation conditions of the cracked wide plate specimens. All fracture initiation points were located in the large CTOD part of the crack front, as well as in the widely extended high opening stress region. However, the initiation points did not always correspond to the highest opening stress point along the crack front. These results indicated that the existence of a extensive high stress region accompanied by a large CTOD, is significant in the brittle fracture initiation condition. These results also suggested that fracture assessment based on the Weibull stress criterion is reasonable, because the Weibull stress takes the volume effect of the high stress area into account.

B.r. Bass - One of the best experts on this subject based on the ideXlab platform.

  • application of the weibull methodology to a shallow flaw cruciform bend specimen tested under Biaxial Loading conditions
    ASTM special technical publications, 2000
    Co-Authors: Paul T Williams, B.r. Bass, W. J. Mcafee
    Abstract:

    This paper describes the application of the Weibull methodology to the analysis of a shallow-flaw cruciform bend specimen tested under Biaxial Loading conditions. The cruciform bend fracture mechanics specimen was developed at Oak Ridge National Laboratory (ORNL) to introduce a far-field, out-of-plane Biaxial bending stress component in the test section that approximates the nonlinear stresses resulting from pressurized-thermal-shock or pressure-temperature Loading of a nuclear reactor pressure vessel (RPV). Tests with the cruciform specimen demonstrated that Biaxial Loading can have a pronounced effect on shallow-flaw fracture toughness in the lower transition temperature region for an RPV material. High-constraint deep-flaw compact tension C(T) and low-constraint shallow-flaw cruciform fracture toughness data were used to assess the ability of the Weibull methodology to predict the observed effects of Biaxial Loading on shallow-flaw fracture toughness. A new hydrostatic stress criterion along with five equivalent-stress criteria from the literature were selected to serve as candidate kernels in the integral formulation of the Weibull stress. Among these candidates, the hydrostatic stress criterion, derived from the first invariant of the Cauchy stress tensor, was determined to have the required sensitivity to multiaxial-Loading states. In addition, a new calibration technique developed by researchers at the University of Illinois for determining the necessary Weibull parameters is applied to the C(T) and cruciform data. A three-parameter Weibull model based on the hydrostatic stress criterion is shown to predict the experimentally observed Biaxial effect on cleavage fracture toughness by providing a scaling mechanism between uniaxial and Biaxial Loading states. In summary, the conclusions that can be drawn from this study are as follows: (1) With respect to its effect on fracture toughness, the Biaxial effect is a constraint effect. (2) A Weibull statistical fracture model has been successfully calibrated with uniaxial toughness data obtained from a conventional high-constraint C(T) specimen and a uniaxially loaded shallow-flaw cruciform that is effectively equivalent to a conventional shallow-flaw SE(B) specimen. (3) The calibrated fracture model was able to successfully predict the intermediate constraint-loss effects associated with two levels of Biaxial Loading. (4) These preliminary results at a single test temperature offer encouragement that complex multiaxial Loading effects on transition region fracture toughness can be predicted with statistical fracture models developed using data obtained from conventional specimens. (5) Future work is required to investigate these effects at other temperatures within the transition region.

  • shallow flaws under Biaxial Loading conditions part ii application of a weibull stress analysis of the cruciform bend specimen using a hydrostatic stress criterion
    ASME Pressure Vessels and Piping Conference Boston MA August 1-5 1999, 1999
    Co-Authors: B.r. Bass, W. J. Mcafee, Paul T Williams
    Abstract:

    Cruciform beam fracture mechanics specimensl have been developed in the Heavy Section Steel Technology (HSST) Program at Oak Ridge National Laboratory (ORNL) to introduce a prototypic, far- field, out-of-plane biaxird bending stress component in the test section that approximates the nonlinear Biaxial stresses resulting from pressurized-thernxd-shock or pressure-temperature Loading of a nuclear reactor pressure vessel (RPV). Matrices of cruciform beam tests were developed to investigate and quantify the effects of temperature, Biaxial Loading, and specimen size on fracture initiation toughness of two-dimensional (constant depth), shtdlow, surface flaws. Tests were conducted under Biaxial load ratios ranging from uniaxial to equiBiaxial. These tests demonstrated that Biaxial Loading can have a pronounced effect on shallow-flaw fracture toughness in the lower transition temperature region for RPV materials. Two and three- parameter Weibull models have been calibrated using a new scheme (developed at the University of Illinois) that maps toughness data from test specimens with distinctly different levels of crack-tip constraint to a small scale yielding (SSY) Weibull stress space. These models, using the new hydrostatic stress criterion in place of the more commonly used maximum principal stress in the kernel of the OW integral definition, have been shown to correlate the experimentally observed biaxiaI effect in cruciform specimens, thereby providing a scaling mechanism between uniaxial and Biaxial Loading states.

  • Fracture assessment of shallow-flaw cruciform beams tested under uniaxial and Biaxial Loading conditions
    Nuclear Engineering and Design, 1999
    Co-Authors: B.r. Bass, W. J. Mcafee, Paul T Williams, W.e. Pennell
    Abstract:

    A technology to determine shallow-flaw fracture toughness of reactor pressure vessel (RPV) steels is being developed for application to the safety assessment of RPVs containing postulated shallow surface flaws. Matrices of cruciform beam tests were developed to investigate and quantify the effects of temperature, Biaxial Loading, and specimen size on fracture initiation toughness of two-dimensional (constant depth), shallow, surface flaws. The cruciform beam specimens were developed at Oak Ridge National Laboratory (ORNL) to introduce a far-field, out-of-plane Biaxial stress component in the test section that approximates the nonlinear stresses resulting from pressurized-thermal-shock or pressure–temperature Loading of an RPV. Tests were conducted under Biaxial load ratios ranging from uniaxial to equiBiaxial. These tests demonstrated that Biaxial Loading can have a pronounced effect on shallow-flaw fracture toughness in the lower transition temperature region for an RPV material. The cruciform fracture toughness data were used to evaluate fracture methodologies for predicting the observed effects of Biaxial Loading on shallow-flaw fracture toughness. Initial emphasis was placed on assessment of stress-based methodologies, namely, the J–Q formulation, the Dodds–Anderson toughness scaling model, and the Weibull approach. Applications of these methodologies based on the hydrostatic stress fracture criterion indicated an effect of Loading-Biaxiality on fracture toughness; the conventional maximum principal stress criterion indicated no effect. A three-parameter Weibull model based on the hydrostatic stress criterion is shown to correlate with the experimentally observed Biaxial effect on cleavage fracture toughness by providing a scaling mechanism between uniaxial and Biaxial Loading states.

  • evaluation of constraint methodologies applied to a shallow flaw cruciform bend specimen tested under Biaxial Loading conditions
    1998 ASME JSME joint pressure vessel and piping (PVP) conference San Diego CA (United States) 26-30 Jul 1998, 1998
    Co-Authors: B.r. Bass, W. J. Mcafee, Paul T Williams, W.e. Pennell
    Abstract:

    A technology to determine shallow-flaw fracture toughness of reactor pressure vessel (RPV) steels is being developed for application to the safety assessment of RPVs containing postulated shallow surface flaws. Matrices of cruciform beam tests were developed to investigate and quantify the effects of temperature, Biaxial Loading, and specimen size on fracture initiation toughness of two-dimensional (constant depth), shallow surface flaws. The cruciform beam specimens were developed at Oak Ridge National Laboratory (ORNL) to introduce a prototypic, far-field. out-of-plane Biaxial stress component in the test section that approximates the nonlinear stresses resulting from pressurized-thermal-shock or pressure-temperature Loading of an RPV. Tests were conducted under Biaxial load ratios ranging from uniaxial to equiBiaxial. These tests demonstrated that Biaxial Loading can have a pronounced effect on shallow-flaw fracture toughness in the lower transition temperature region for RPV materials. The cruciform fracture toughness data were used to evaluate fracture methodologies for predicting the observed effects of Biaxial Loading on shallow-flaw fracture toughness. Initial emphasis was placed on assessment of stress-based methodologies. namely, the J-Q formulation, the Dodds-Anderson toughness scaling model, and the Weibull approach. Applications of these methodologies based on the hydrostatic stress fracture criterion indicated an effect of Loading-Biaxiality on fracture toughness, the conventional maximum principal stress criterion indicated no effect.

  • Preliminary assessment of the effects of Biaxial Loading on reactor pressure vessel structural-integrity-assessment technology
    1996
    Co-Authors: W.e. Pennell, B.r. Bass, W. J. Mcafee, J.w. Bryson, T.l. Dickson, J.g. Merkle
    Abstract:

    Effects of Biaxial Loading on shallow-flaw fracture toughness were studied to determine potential impact on structural integrity assessment of a reactor pressure vessel (RPV) under pressurized thermal shock (PTS) transient Loading and pressure-temperature (PT) Loading produced by reactor heatup and cooldown transients. Biaxial shallow-flaw fracture-toughness tests results were also used to determine the parameter controlling fracture in the transition temperature range, and to develop a related dual-parameter fracture-toughness correlation. Shallow-flaw and Biaxial Loading effects were found to reduce the conditional probability of crack initiation by a factor of nine when the shallow-flaw fracture-toughness K{sub Jc} data set, with Biaxial-Loading effects adjustments, was substituted in place of ASME Code K{sub Ic} data set in PTS analyses. Biaxial Loading was found to reduce the shallow-flaw fracture toughness of RPV steel such that the lower-bound curve was located between ASME K{sub Ic} and K{sub IR} curves. This is relevant to future development of P-T curve analysis procedures. Fracture in shallow-flaw Biaxial samples tested in the lower transition temperature range was shown to be strain controlled. A strain-based dual-parameter fracture-toughness correlation was developed and shown to be capable of predicting the effect of crack-tip constraint on fracture toughness for strain-controlled fracture.