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.
{"title":"Application of the Weibull Methodology to a Shallow-Flaw Cruciform Bend Specimen Tested Under Biaxial Loading Conditions","authors":"P. Williams, B. Bass, W. J. Mcafee","doi":"10.1520/STP14804S","DOIUrl":"https://doi.org/10.1520/STP14804S","url":null,"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.","PeriodicalId":8583,"journal":{"name":"ASTM special technical publications","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74506346","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Many aircraft component failures originate from small-surface flaw cracks in highly stressed locations. It is therefore desirable to measure the threshold stress intensity factor that simulates the key conditions of high-stress and small semicircular surface crack shape. Such a technique has been developed and demonstrated on multiple titanium and nickel-base alloys. This technique is effective at both room and elevated temperatures and at both low and high mean stress. The test method is described in detail, but in brief a small EDM flaw is made on the surface of a rectangular specimen. The crack length is monitored via electrical potential drop technique. The crack length and aspect ratio versus the change in electrical potential across the crack tip has been measured and is used to control the load shed during the experiment. Load sheds up to C = - 1181 m - 1 have been demonstrated to give comparable thresholds to those measured using single edge notch or compact tension geometries with lower shed rates. Typical experimental results on both Ti-6Al-4V and an advanced nickel-base superalloy (KM4) are shown at both room temperature and elevated temperatures. This technique allows a rapid determination of threshold stress intensity factor for a material in a manner simulating the types of constraint experienced in components.
许多飞机部件的故障都是由高应力位置的小表面裂纹引起的。因此，需要测量模拟高应力和小半圆形表面裂纹形状的关键条件的阈值应力强度因子。这种技术已经在多种钛基和镍基合金上得到了发展和证明。这种技术在室温和高温下以及在低和高平均应力下都有效。详细描述了测试方法，但简单地说，在矩形试样的表面上产生了一个小的电火花加工缺陷。采用电势降技术监测裂纹长度。测量了裂纹长度和纵横比与裂纹尖端电势变化的关系，并用于控制实验过程中的载荷脱落。高达C = - 1181 m - 1的荷载棚已被证明与使用单边缘缺口或具有较低脱落率的紧凑张力几何形状测量的值相当。给出了Ti-6Al-4V和一种高级镍基高温合金(KM4)在室温和高温下的典型实验结果。该技术允许以模拟组件中所经历的约束类型的方式快速确定材料的阈值应力强度因子。
{"title":"Fatigue Crack Growth Threshold Stress Intensity Determination via Surface Flaw (Kb Bar) Specimen Geometry","authors":"K. Bain, David Miller","doi":"10.1520/STP14814S","DOIUrl":"https://doi.org/10.1520/STP14814S","url":null,"abstract":"Many aircraft component failures originate from small-surface flaw cracks in highly stressed locations. It is therefore desirable to measure the threshold stress intensity factor that simulates the key conditions of high-stress and small semicircular surface crack shape. Such a technique has been developed and demonstrated on multiple titanium and nickel-base alloys. This technique is effective at both room and elevated temperatures and at both low and high mean stress. The test method is described in detail, but in brief a small EDM flaw is made on the surface of a rectangular specimen. The crack length is monitored via electrical potential drop technique. The crack length and aspect ratio versus the change in electrical potential across the crack tip has been measured and is used to control the load shed during the experiment. Load sheds up to C = - 1181 m - 1 have been demonstrated to give comparable thresholds to those measured using single edge notch or compact tension geometries with lower shed rates. Typical experimental results on both Ti-6Al-4V and an advanced nickel-base superalloy (KM4) are shown at both room temperature and elevated temperatures. This technique allows a rapid determination of threshold stress intensity factor for a material in a manner simulating the types of constraint experienced in components.","PeriodicalId":8583,"journal":{"name":"ASTM special technical publications","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80248173","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This work describes the development and verification of a 3-D model to predict stable, Mode I crack growth in thin, ductile aluminum alloys. The model extends the standard 2-D form of the crack tip opening angle (CTOA) methodology, which determines crack extension based on obtaining a critical angle at the crack tip. When the CTOA reaches the critical value, all the nodes along the current, 3-D crack front are released simultaneously, thereby growing the crack in a self-similar manner. Evaluation of the CTOA occurs at a specified distance behind the crack tip; this decouples CTOA evaluation from mesh refinement. The CTOA-based model also includes adaptive load control strategies to minimize the effects of discrete load increments on the growth response. To evaluate the effectiveness of the described approach, this work describes a validation study using load-crack extension data from 2.3-mm-thick Al 2024-T3 specimens tested at NASA-Langley. The test matrix includes C(T) and M(T) specimens, with varying widths (50 to 600 mm), a/W ratios, and levels of constraint to suppress out-of-plane bending. Comparisons of load-crack extension curves from experiments and analyses of a constrained 150-mm C(T) specimen provide a calibrated critical CTOA value of 5.1°. Analyses using the calibrated CTOA value for constrained and unconstrained specimens provide predictions of peak load in good agreement with the experimental values.
{"title":"3-D Finite Element Modeling of Ductile Crack Growth in Thin Aluminum Materials","authors":"A. Gullerud, R. H. Dodds, R. Hampton, D. Dawicke","doi":"10.1520/STP13397S","DOIUrl":"https://doi.org/10.1520/STP13397S","url":null,"abstract":"This work describes the development and verification of a 3-D model to predict stable, Mode I crack growth in thin, ductile aluminum alloys. The model extends the standard 2-D form of the crack tip opening angle (CTOA) methodology, which determines crack extension based on obtaining a critical angle at the crack tip. When the CTOA reaches the critical value, all the nodes along the current, 3-D crack front are released simultaneously, thereby growing the crack in a self-similar manner. Evaluation of the CTOA occurs at a specified distance behind the crack tip; this decouples CTOA evaluation from mesh refinement. The CTOA-based model also includes adaptive load control strategies to minimize the effects of discrete load increments on the growth response. To evaluate the effectiveness of the described approach, this work describes a validation study using load-crack extension data from 2.3-mm-thick Al 2024-T3 specimens tested at NASA-Langley. The test matrix includes C(T) and M(T) specimens, with varying widths (50 to 600 mm), a/W ratios, and levels of constraint to suppress out-of-plane bending. Comparisons of load-crack extension curves from experiments and analyses of a constrained 150-mm C(T) specimen provide a calibrated critical CTOA value of 5.1°. Analyses using the calibrated CTOA value for constrained and unconstrained specimens provide predictions of peak load in good agreement with the experimental values.","PeriodicalId":8583,"journal":{"name":"ASTM special technical publications","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81914329","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Uruchurtu-Chavarín, L. Mariaca-Rodriguez, G. Micat
{"title":"Electrochemical evaluation of the protective properties of steel corrosion products formed in Ibero-American tropical atmospheres","authors":"J. Uruchurtu-Chavarín, L. Mariaca-Rodriguez, G. Micat","doi":"10.1520/STP13556S","DOIUrl":"https://doi.org/10.1520/STP13556S","url":null,"abstract":"","PeriodicalId":8583,"journal":{"name":"ASTM special technical publications","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76661943","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Poly(ethylene-2,6-naphthalate), PEN, is a suitable candidate to replace poly (ethylene terephthalate), PET, in some applications. PEN can be produced in either the amorphous or semi-crystalline states, depending on the processing conditions. Here, we report on results from uniaxial tension experiments in creep conditions in which we probed the viscoelastic and physical aging responses for both amorphous and semi-crystalline forms of PEN. The data show the existence of overlapping β and a relaxations in the experimental creep time range studied. The β process is stronger in the amorphous than in the semi-crystalline material and, in both cases, shows different aging time and temperature dependencies. A model in which the a process is treated as a stretched exponential process and the β process as a Cole-Cole process is developed and its validity examined for both the amorphous and semi-crystalline PEN materials.
{"title":"Creep Behavior in Amorphous and Semicrystalline PEN","authors":"M. Cerrada, G. McKenna","doi":"10.1520/STP15828S","DOIUrl":"https://doi.org/10.1520/STP15828S","url":null,"abstract":"Poly(ethylene-2,6-naphthalate), PEN, is a suitable candidate to replace poly (ethylene terephthalate), PET, in some applications. PEN can be produced in either the amorphous or semi-crystalline states, depending on the processing conditions. Here, we report on results from uniaxial tension experiments in creep conditions in which we probed the viscoelastic and physical aging responses for both amorphous and semi-crystalline forms of PEN. The data show the existence of overlapping β and a relaxations in the experimental creep time range studied. The β process is stronger in the amorphous than in the semi-crystalline material and, in both cases, shows different aging time and temperature dependencies. A model in which the a process is treated as a stretched exponential process and the β process as a Cole-Cole process is developed and its validity examined for both the amorphous and semi-crystalline PEN materials.","PeriodicalId":8583,"journal":{"name":"ASTM special technical publications","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82992363","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Soboyejo, M. Foster, C. Mercer, J. Papritan, W. Soboyejo
A multiparameter model is proposed for the characterization of fatigue crack growth in structural metallic materials. The model assesses the combined effects of identifiable multiple variables that can contribute to fatigue crack growth. Mathematical expressions are presented for the determination of fatigue crack growth rates, da/dN, as functions of multiple variables, such as: stress intensity factor range, ΔK; stress ratio, R; closure stress intensity factor, K c l , and the maximum stress intensity factor, K m a x . A generalized empirical methodology is proposed for the estimation of fatigue crack growth rates as functions of these variables. The validity of the new methodology is then verified by making appropriate comparisons between predicted and measured fatigue crack growth data obtained from experiments on selected structural metallic materials. The multiparameter predictions are shown to be in close agreement with experimental data.
{"title":"A new multiparameter model for the prediction of fatigue crack growth in structural metallic materials","authors":"A. Soboyejo, M. Foster, C. Mercer, J. Papritan, W. Soboyejo","doi":"10.1520/STP13412S","DOIUrl":"https://doi.org/10.1520/STP13412S","url":null,"abstract":"A multiparameter model is proposed for the characterization of fatigue crack growth in structural metallic materials. The model assesses the combined effects of identifiable multiple variables that can contribute to fatigue crack growth. Mathematical expressions are presented for the determination of fatigue crack growth rates, da/dN, as functions of multiple variables, such as: stress intensity factor range, ΔK; stress ratio, R; closure stress intensity factor, K c l , and the maximum stress intensity factor, K m a x . A generalized empirical methodology is proposed for the estimation of fatigue crack growth rates as functions of these variables. The validity of the new methodology is then verified by making appropriate comparisons between predicted and measured fatigue crack growth data obtained from experiments on selected structural metallic materials. The multiparameter predictions are shown to be in close agreement with experimental data.","PeriodicalId":8583,"journal":{"name":"ASTM special technical publications","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73148494","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Current research on wood reinforcement has focused on the use of fiber-reinforced plastic (FRP) strips or fabrics bonded to wood members. Although significant increases in stiffness and strength have been achieved by thisreinforcing technique, there is a concern about the reliable performance of the wood-FRP interface bond, which can be susceptible to delamination. The objective of this study is to present a combined analytical/ experimental study to evaluate the effect of moisture on fracture toughness of composite/wood bonded interfaces under Mode I loading. A contoured double cantilever beam (CDCB) specimen is used to characterize the fracture toughness of both wood-wood and wood-FRP samples. The specimens are designed by the Rayleigh Ritz method to achieve a linear rate of compliance with respect to crack length and are calibrated experimentally and also analytically by the finite element method. Both wood-wood and wood-FRP samples are tested under dry and wet conditions, and bonded interface fracture toughness data under Mode I loading are obtained. The guidelines and procedures for the modeling and design of CDCB specimens for hybrid or dissimilar adherends using a Rayleigh-Ritz model are presented briefly, and a modified Rayleigh-Ritz method is further developed. The effect of moisture on fracture toughness is evaluated, and increases in interface fracture toughness are observed due to moisture absorption for wet wood-wood and wood-FRP samples; the toughening of the interface under moisture is due mainly to a much more plastic fracture failure mode of the interface.
{"title":"Effect of moisture on fracture toughness of composite/wood bonded interfaces","authors":"P. Qiao, J. Davalos, B. Trimble","doi":"10.1520/STP14819S","DOIUrl":"https://doi.org/10.1520/STP14819S","url":null,"abstract":"Current research on wood reinforcement has focused on the use of fiber-reinforced plastic (FRP) strips or fabrics bonded to wood members. Although significant increases in stiffness and strength have been achieved by thisreinforcing technique, there is a concern about the reliable performance of the wood-FRP interface bond, which can be susceptible to delamination. The objective of this study is to present a combined analytical/ experimental study to evaluate the effect of moisture on fracture toughness of composite/wood bonded interfaces under Mode I loading. A contoured double cantilever beam (CDCB) specimen is used to characterize the fracture toughness of both wood-wood and wood-FRP samples. The specimens are designed by the Rayleigh Ritz method to achieve a linear rate of compliance with respect to crack length and are calibrated experimentally and also analytically by the finite element method. Both wood-wood and wood-FRP samples are tested under dry and wet conditions, and bonded interface fracture toughness data under Mode I loading are obtained. The guidelines and procedures for the modeling and design of CDCB specimens for hybrid or dissimilar adherends using a Rayleigh-Ritz model are presented briefly, and a modified Rayleigh-Ritz method is further developed. The effect of moisture on fracture toughness is evaluated, and increases in interface fracture toughness are observed due to moisture absorption for wet wood-wood and wood-FRP samples; the toughening of the interface under moisture is due mainly to a much more plastic fracture failure mode of the interface.","PeriodicalId":8583,"journal":{"name":"ASTM special technical publications","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86682561","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A slice synthesis methodology was developed and used to construct a weight function based strip-yield model for a semi-elliptical part-through surface flaw in an elastic-perfectly plastic material under monotonic loading.The model enables rapid approximate computation of crack surface displacements and the crack front plastic zone size. A mathematical description of the model is presented. A model verification is discussed in which results from the strip-yield model were compared with results from finite element analyses. Crack surface displacements and crack mouth opening displacements from the model are shown to compare well with results from detailed three-dimensional elastic-plastic finite element analyses. Plastic zone sizes from the model were found to be significantly larger than those determined from the finite element model.
{"title":"A Strip-Yield Model for Part-Through Surface Flaws Under Monotonic Loading","authors":"S. Daniewicz, C. Aveline","doi":"10.1520/STP14803S","DOIUrl":"https://doi.org/10.1520/STP14803S","url":null,"abstract":"A slice synthesis methodology was developed and used to construct a weight function based strip-yield model for a semi-elliptical part-through surface flaw in an elastic-perfectly plastic material under monotonic loading.The model enables rapid approximate computation of crack surface displacements and the crack front plastic zone size. A mathematical description of the model is presented. A model verification is discussed in which results from the strip-yield model were compared with results from finite element analyses. Crack surface displacements and crack mouth opening displacements from the model are shown to compare well with results from detailed three-dimensional elastic-plastic finite element analyses. Plastic zone sizes from the model were found to be significantly larger than those determined from the finite element model.","PeriodicalId":8583,"journal":{"name":"ASTM special technical publications","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76560107","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A critical component of any ecological risk assessment is the specification of the assessment endpoints. However, selecting assessment endpoints for risk assessment is often a formidable task, particularly for sites with extensive and diverse ecological resources, such as those found at Los Alamos National Laboratory. The General Assessment Endpoint (GAE) process provides a comprehensive, systematic and defensible basis for reaching consensus with regulators and other stakeholders on the assessment endpoints for ecological risk assessments. This paper provides an overview of the GAE process and reports on a pilot project to implement the process for the Pajarito Plateau ecosystem, the ecosystem potentially affected by the Laboratory's legacy hazardous waste.
{"title":"General Assessment Endpoints for Ecological Risk Assessment at Los Alamos National Laboratory","authors":"D. Reagan, E. Kelly, M. Hooten, D. Michael","doi":"10.1520/STP14421S","DOIUrl":"https://doi.org/10.1520/STP14421S","url":null,"abstract":"A critical component of any ecological risk assessment is the specification of the assessment endpoints. However, selecting assessment endpoints for risk assessment is often a formidable task, particularly for sites with extensive and diverse ecological resources, such as those found at Los Alamos National Laboratory. The General Assessment Endpoint (GAE) process provides a comprehensive, systematic and defensible basis for reaching consensus with regulators and other stakeholders on the assessment endpoints for ecological risk assessments. This paper provides an overview of the GAE process and reports on a pilot project to implement the process for the Pajarito Plateau ecosystem, the ecosystem potentially affected by the Laboratory's legacy hazardous waste.","PeriodicalId":8583,"journal":{"name":"ASTM special technical publications","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75015967","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Elastic-plastic finite element analyses of surface-cracked plates are performed using the commercial finite element code ANSYS. Various crack geometries are analyzed under tension and bending loads. A constraint factor dependent on the location along the perimeter of the surface crack, similar to the global constraint factor defined by Newman, is presented. This newly defined constraint factor is the averaged normal stress to flow stress ratio acting on a line originating on and perpendicular to the crack front at a prescribed location and terminating at the perimeter of the plastic zone on the crack plane. The plastic zone shape and size around the three-dimensional crack front determined from the finite element analyses are also presented. The analyses indicate that the maximum plastic zone size occurs beneath the free surface (2° < Φ < 5°). Geometry and applied loading parameters are considered in equations relating them to constraint along the crack front.
{"title":"Variations of constraint and plastic zone size in surface-cracked plates under tension or bending loads","authors":"C. Aveline, S. Daniewicz","doi":"10.1520/STP14802S","DOIUrl":"https://doi.org/10.1520/STP14802S","url":null,"abstract":"Elastic-plastic finite element analyses of surface-cracked plates are performed using the commercial finite element code ANSYS. Various crack geometries are analyzed under tension and bending loads. A constraint factor dependent on the location along the perimeter of the surface crack, similar to the global constraint factor defined by Newman, is presented. This newly defined constraint factor is the averaged normal stress to flow stress ratio acting on a line originating on and perpendicular to the crack front at a prescribed location and terminating at the perimeter of the plastic zone on the crack plane. The plastic zone shape and size around the three-dimensional crack front determined from the finite element analyses are also presented. The analyses indicate that the maximum plastic zone size occurs beneath the free surface (2° < Φ < 5°). Geometry and applied loading parameters are considered in equations relating them to constraint along the crack front.","PeriodicalId":8583,"journal":{"name":"ASTM special technical publications","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76209180","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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