定价： 590元 / 折扣价： 502 元 加购物车

定价： 590元 / 折扣价： 502 元 加购物车

定价： 515元 / 折扣价： 438 元 加购物车

定价： 590元 / 折扣价： 502 元 加购物车

5.1 Surface cracks are among the most common defects found in structural components. An accurate characterization and understanding of crack-front behavior is necessary to ensure successful operation of a structure containing surface cracks. The testing of laboratory specimens with surface cracks provides a means to understand and quantify surface crack behavior, but the test results must be interpreted correctly to ensure transferability between the laboratory specimen and the structure.5.2 Transferability refers to the capacity of a fracture mechanics methodology to correlate the crack-tip stress and strain fields of different cracked bodies. Traditionally, the correlation has been based on the presence at fracture of a dominant, asymptotically singular, crack-tip field with amplitude set by the value of a single parameter, such as the stress intensity factor, KI, or the J-integral. For components and specimens with high crack-tip constraint, the singular crack-tip field dominates over microstructurally significant size scales for loads ranging from globally linear-elastic conditions to moderately large-scale plasticity. For specimens with low crack-tip constraint, a dominant single-parameter crack-tip field exists only at low levels of plasticity. At higher levels of plasticity, the opening mode stress of the low constraint specimen is lower than predicted by the single-parameter, asymptotically singular fields. Therefore, low constraint specimens often exhibit larger fracture toughness than do high constraint specimens. If feasible, users are strongly encouraged to generate high constraint fracture toughness data using methods such as Test Methods E399 or E1820 prior to testing the surface crack geometry.5.2.1 To address this phenomenon, two-parameter fracture criteria are used to include the influence of crack-tip constraint. Crack-tip constraint has been quantified using various scalar parameters including the T-stress (10, 11, 12), Q (13, 14), stress triaxiality (15, 16), and αh (17, 18). Fracture toughness in a two-parameter methodology is not a single value, but rather is a curve that defines a critical locus of fracture toughness and constraint values (2). Fig. 2 illustrates a toughness-constraint locus for application of two-parameter fracture mechanics to structures. A structural analysis provides the driving force curve for the configuration of interest, and is plotted with the toughness-constraint locus obtained from specimen test data. Crack extension is predicted when the driving force curve passes through the toughness-constraint locus.5.3 Tests conducted with this method provide data to assist in the prediction of structural capability in the presence of a surface crack by including a measure of crack-tip constraint in the interpretation of fracture toughness values. This improves the correlation of test specimen and structural conditions. To achieve the most accurate comparison, the conditions tested in accordance with this test method should match the structure as closely as possible. For conservative structural assessment, the user should ensure that conditions in the test specimen produce higher levels of constraint relative to the structure in application of the data. Factors that influence test specimen conditions include, but are not limited to, specimen geometry, a/c, a/B, loading conditions, as well as the amount and type of crack extension that occurred during the test.NOTE 3: The use of a constraint-based framework for the analysis of surface cracks permits a more realistic assessment of structural capability. This approach generally leads to a less conservative assessment than would be achieved, for example, by using a measure of high-constraint fracture toughness obtained from testing standard C(T) and SE(B) specimens of the material following Test Method E1820. It is essential that constraint effects measured in surface crack tests with this method be applied to any structural assessment with the requisite understanding to maintain appropriate levels of conservatism.5.4 This test method does not address environmental effects or loading rate effects that may be significant in assessing service integrity.1.1 This test method describes the method for testing fatigue-sharpened, semi-elliptically shaped surface cracks in rectangular flat panels subjected to monotonically increasing tension or bending. Tests quantify the crack-tip conditions at initiation of stable crack extension or immediate unstable crack extension.1.2 This test method applies to the testing of metallic materials not limited by strength, thickness, or toughness. Materials are assumed to be essentially homogeneous and free of residual stress. Tests may be conducted at any appropriate temperature. The effects of environmental factors and sustained or cyclic loads are not addressed in this test method.1.3 This test method describes all necessary details for the user to test for the initiation of crack extension in surface crack test specimens. Specific requirements and recommendations are provided for test equipment, instrumentation, test specimen design, and test procedures.1.4 Tests of surface cracked, laboratory-scale specimens as described in this test method may provide a more accurate understanding of full-scale structural performance in the presence of surface cracks. The provided recommendations help to assure test methods and data are applicable to the intended purpose.1.5 This test method prescribes a consistent methodology for test and analysis of surface cracks for research purposes and to assist in structural assessments. The methods described here utilize a constraint-based framework (1, 2)2 to evaluate the fracture behavior of surface cracks.NOTE 1: Constraint-based framework. In the context of this test method, constraint is used as a descriptor of the three-dimensional stress and strain fields in the near vicinity of the crack tip, where material contractions due to the Poisson effect may be suppressed and therefore produce an elevated, tensile stress state (3, 4). (See further discussions in Terminology and .) When a parameter describing this stress state, or constraint, is used with the standard measure of crack-tip stress amplitude (K or J), the resulting two-parameter characterization broadens the ability of fracture mechanics to accurately predict the response of a crack under a wider range of loading. The two-parameter methodology produces a more complete description of the crack-tip conditions at the initiation of crack extension. The effects of constraint on measured fracture toughness are material dependent and are governed by the effects of the crack-tip stress-strain state on the micromechanical failure processes specific to the material. Surface crack tests conducted with this test method can help to quantify the material sensitivity to constraint effects and to establish the degree to which the material toughness correlates with a constraint-based fracture characterization.1.6 This test method provides a quantitative framework to categorize test specimen conditions into one of three regimes: (I) a linear-elastic regime, (II) an elastic-plastic regime, or (III) a field-collapse regime. Based on this categorization, analysis techniques and guidelines are provided to determine an applicable crack-tip parameter for the linear-elastic regime (K or J) or the elastic-plastic regime (J), and an associated constraint parameter. Recommendations are provided to assess the test data in the context of a toughness-constraint locus (2). For tension loading, a computer program referred to as TASC V1.0.2 (Tool for Analysis of Surface Cracks) may be used to perform the analytical assessments in Section 9, Analysis of Results. The user is directed to other resources for evaluation of the test specimen in the field-collapse regime when extensive plastic deformation in the specimen eliminates the identifiable crack-front fields of fracture mechanics.NOTE 2: TASC. The computer program TASC is available at no charge either at https://software.nasa.gov/software/MFS-33082-1 or at https://sourceforge.net/projects/tascnasa/. The use of TASC relieves the user of the burden of performing unique elastic-plastic finite element analyses for each test performed in the elastic-plastic regime. For the purposes of this standard, TASC calculations are equivalent to finite element analysis results. Users of TASC should follow the methodologies in Annex A6 for establishing analysis material property inputs. Documentation on the development, verification and validation of TASC is provided in references (5, 6, 7, 8).1.7 The specimen design and test procedures described in this test method may be applied to evaluation of surface cracks in welds; however, the methods described in this test method to analyze test measurements may not be applicable. Weld fracture tests generally have complicating features beyond the scope of data analysis in this test method, including the effects of residual stress, microstructural variability, and non-uniform strength. These effects will influence test results and must be considered in the interpretation of measured quantities.1.8 This test method is not intended for testing surface cracks in steel in the cleavage regime. Such tests are outside the scope of this test method. A methodology for evaluation of cleavage fracture toughness in ferritic steels over the ductile-to-brittle region using C(T) and SE(B) specimens can be found in Test Method E1921.1.9 Units—The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.1.10 This practice may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.11 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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3.1 This guide can be used to obtain force versus deflection or midspan bending moment versus midspan curvature curves for stents and stent systems subjected to three-point bending conditions. Bending flexibility of a stent system may be a factor in its ability to track through the vascular anatomy, and may be a factor in vascular trauma along the delivery pathway distal to the guide catheter. Bending flexibility of a deployed stent may be one measure of its ability to flex with a vessel, or to conform to the natural curvature of a vessel. Bending flexibility of a delivery system may also be of interest if it is desired to assess the separate contributions of the delivery system and the mounted stent to the overall flexibility of the stent system.3.2 This guide is not intended to determine material properties, stent system trackability (ability of a stent system to follow a guide wire and/or guide catheter through vascular tortuosity), or stent system deliverability (ability of a stent system to deliver a stent to the implantation site(s) or through particular level(s) of vascular tortuosity). While this guide does not determine stent system trackability or deliverability, it can provide quantitative insight into how stent system bending flexibility affects trackability and deliverability. Similarly, while this guide does not determine conformability of a deployed stent, it can provide quantitative insight into how stent and/or stent system bending flexibility affects deployed stent conformability. Since this guide quantifies bending flexibility, it may be useful in determining the magnitude of bending flexibility effects on bending-related performance differences between the test article and control devices.3.3 The three-point bending procedures provided in this guide are intended to be used to characterize balloon-expandable stent and stent system flexibility during product development. They may not necessarily satisfy any particular requirements of national or international regulatory bodies.1.1 This guide provides guidelines for quantitatively characterizing balloon-expandable stent and stent system flexibility using three-point bending procedures. Guidelines are provided for characterizing deployed stent flexibility, and for characterizing pre-deployment stent system flexibility in the region of the stent and balloon.1.2 This guide is not recommended for test articles that cannot be appropriately evaluated using a span length to stent outer diameter (as tested) ratio of at least 4:1. Test articles that do not meet this requirement are likely to exhibit appreciable deformation by modes other than bending.1.3 This guide does not provide procedures for characterizing the bending flexibility of self-expanding stents, self-expanding stent systems, endoprostheses (stent-grafts), or endoprostheses systems. However, some aspects of this guide may be useful for developing appropriate three-point bending characterization procedures for these devices. While this guide was developed with vascular stents and stent systems in mind, it may be useful for characterizing the bending flexibility of balloon-expandable stents and stent systems used in non-vascular applications.1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are mathematical conversions to inch-pound units that are provided for information only and are not considered standard.1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

定价： 590元 / 折扣价： 502 元 加购物车

定价： 515元 / 折扣价： 438 元 加购物车

定价： 590元 / 折扣价： 502 元 加购物车

定价： 515元 / 折扣价： 438 元 加购物车

5.1 This practice establishes the procedure to determine adjustment factors that account for the isolated effects of fire-retardant treatment on plywood roof sheathing. These effects are established relative to performance of untreated plywood. This practice uses data from reference thermal-load cycles designed to simulate temperatures in sloped roofs of common design to evaluate products for 50 iterations.5.2 This practice applies to material installed using construction practices recommended by the fire retardant chemical manufacturers that include avoiding exposure to precipitation, direct wetting, or regular condensation. This practice is not meant to apply to buildings with significantly different designs than those described in 1.3.5.3 Test Method D5516 caused thermally induced strength losses in laboratory simulations within a reasonably short period. The environmental conditions used in the laboratory-activated chemical reactions that are considered to be similar to those occurring in the field. This assumption is the fundamental basis of this practice.1.1 This practice covers procedures for calculating adjustment factors that account for the effects of fire-retardant treatment on bending strength of plywood roof sheathing. The adjustment factors calculated in accordance with this practice are to be applied to design values for untreated plywood in order to determine design values for fire-retardant-treated plywood used as sheathing in roof systems. The methods establish the effect of treatment based upon matched bending strength testing of materials with and without treatment after exposure at elevated temperatures.NOTE 1: This analysis focuses on the relative performance of treated and untreated materials tested after equilibrating to ambient conditions following a controlled exposure to specified conditions of high temperature and humidity. Elevated temperature, moisture, load duration, and other factors typically accounted for in the design of untreated plywood must also be considered in the design of fire-retardant-treated plywood roof sheathing, but are outside the scope of the treatment adjustments developed under this practice.1.2 It is assumed that the procedures will be used for fire-retardant-treated plywood installed using appropriate construction practices recommended by the fire retardant chemical manufacturers, which include avoiding exposure to precipitation, direct wetting, or regular condensation.1.3 This practice uses thermal load profiles reflective of exposures encountered in normal service conditions in a wide variety of continental United States climates. The heat gains, solar loads, roof slopes, ventilation rates, and other parameters used in this practice were chosen to reflect common sloped roof designs. This practice is applicable to roofs of 3 in 12 or steeper slopes, to roofs designed with vent areas and vent locations conforming to national standards of practice, and to designs in which the bottom side of the sheathing is exposed to ventilation air. These conditions may not apply to significantly different designs and therefore this practice may not apply to such designs.1.4 Information and a brief discussion supporting the provisions of this practice are in the Commentary in the appendix. A large, more detailed, separate Commentary is also available from ASTM.21.5 The methodology in this practice is not meant to account for all reported instances of fire-retardant plywood undergoing premature heat degradation.1.6 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

定价： 590元 / 折扣价： 502 元 加购物车

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5.1 It is important to consider the durability of stent designs in deformation modes that are intended to model in vivo conditions. The appropriate amplitude and number of cycles in each of the modes have to be determined independently for the particular clinical use proposed for the stent. These tests do not replicate all varieties and aspects of the deployment process nor the in vivo mechanical environment in its entirety, and as such they cannot be proofs of durability. Instead, the tests provide evidence of durability. The durability tests can also provide a means of assessing design, material or processing changes.5.1.1 This guide might be useful for development testing, specification acceptance testing, and regulatory submission testing and filings as it provides a basic assurance that the tests are designed, executed, and reported in a suitable fashion.5.1.2 If the tests are conducted using a well defined FTF methodology, they can be useful in:5.1.2.1 Potential design improvement through identification of better and worse geometries, materials, and manufacturing processes;5.1.2.2 Understanding product durability by estimating the effects of changes in geometry, materials, or manufacturing processes;5.1.2.3 Estimating the safety factor relative to the amplitudes and other factors in use conditions; and5.1.2.4 Validating finite element analysis (FEA) and fatigue life models.5.1.3 As stated in the scope, this guide is not intended to provide the in vivo physiologic deformation conditions to which a vascular stent can be subjected. Reliable clinical data characterizing cyclic vascular deformation may be lacking for some indications. The user should develop and justify the boundary conditions (e.g., by literature review, in vivo studies, cadaver studies, or modeling of stent vessel interaction) for the chosen durability bench tests. Additional conditions that may be considered include vessel calcification, vessel taper, eccentric lesions, deformation excursions (e.g., exercise), and vessel remodeling.5.1.4 Test methods other than those provided in the annexes of this document might be appropriate, depending upon stent design. However, these methods are beyond the scope of this guide.1.1 This guide includes three separate cyclic deformation durability guides related to vascular stents: bending, axial, and torsional.1.2 This guide does not address flat plate, local crush durability, or multi-mode testing. Although this guide does not address multi-mode testing, the information included herein could be applicable to developing this type of test.1.3 This guide applies to balloon-expandable and self-expanding stents fabricated from metals and metal alloys. It does not specifically address any attributes unique to coated stents (i.e., stents with a surface layer of an additional material(s)), monolithically polymeric stents, or absorbable stents, although the application of this standard to those products is not precluded.1.4 This guide applies to endovascular grafts (“stent-grafts”) and other conduit products commonly used to treat aneurismal disease, peripheral vessel trauma, or to provide vascular access. The information provided herein does not address all issues related to testing of these devices.1.5 This guide is applicable to testing of stent(s) (or a representative portion of a stent). While durability testing of coupon samples (e.g., a scaled-up portion of the stent structure) can provide useful information, it is not within the scope of this guide.1.6 This guide applies to in vitro modeling of stent durability from non-radial arterial motions. Such motions may arise from musculoskeletal activities, including walking and breathing, and cardiac motion. Test Methods F2477 addresses pulsatile (i.e., radial) durability of vascular stents.1.7 This guide does not provide the in vivo physiologic deformation conditions for a vascular stent. It is incumbent upon the user of the standard to develop and justify these boundary conditions (e.g., by literature review, in vivo studies, cadaver studies, or modeling of stent vessel interaction) in these durability bench tests. Additional conditions that may be considered include vessel calcification, vessel taper, eccentric lesions, loading excursions (e.g., exercise), and vessel remodeling.1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.9 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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5.1 This test method provides a simple means of characterizing the thermomechanical behavior of plastic compositions using very small amounts of material. The data obtained is used for quality control, research and development as well as the establishment of optimum processing conditions.5.2 Dynamic mechanical testing provides a sensitive means for determining thermomechanical characteristics by measuring the elastic and loss moduli as a function of frequency, temperature, or time. Plots of moduli and tan delta of a material versus these variables can be used to provide a graphical representation indicative of functional properties, effectiveness of cure (thermosetting resin system), and damping behavior under specified conditions.5.2.1 Observed data are specific to experimental conditions. Reporting in full (as described in this test method) the conditions under which the data was obtained is essential to assist users with interpreting the data an reconciling apparent or perceived discrepancies.5.3 This test method can be used to assess:5.3.1 Modulus as a function of temperature,5.3.2 Modulus as a function of frequency,5.3.3 The effects of processing treatment,5.3.4 Relative resin behavioral properties, including cure and damping.5.3.5 The effects of substrate types and orientation (fabrication) on modulus,5.3.6 The effects of formulation additives which might affect processability or performance,5.3.7 The effects of annealing on modulus and glass transition temperature,5.3.8 The effect of aspect ratio on the modulus of fiber reinforcements, and5.3.9 The effect of fillers, additives on modulus and glass transition temperature.5.4 Before proceeding with this test method, refer to the specification of the material being tested. Any test specimen preparation, conditioning, dimensions, or testing parameters, or combination thereof, covered in the relevant ASTM materials specification shall take precedence over those mentioned in this test method. If there are no relevant ASTM material specifications, then the default conditions apply.1.1 This test method outlines the use of dynamic mechanical instrumentation for determining and reporting the visco-elastic properties of thermoplastic and thermosetting resins and composite systems in the form of rectangular bars molded directly or cut from sheets, plates, or molded shapes. The data generated, using three-point bending techniques, is used to identify the thermomechanical properties of a plastic material or compositions using a variety of dynamic mechanical instruments.1.2 This test method is intended to provide means for determining the viscoelastic properties of a wide variety of plastics materials using nonresonant, forced-vibration techniques in accordance with Practice D4065. Plots of the elastic (storage) modulus; loss (viscous) modulus; complex modulus and tan delta as a function of frequency, time, or temperature are indicative of significant transitions in the thermomechanical performance of polymeric material systems.1.3 This test method is valid for a wide range of frequencies, typically from 0.01 Hz to 100 Hz.1.4 Due to possible instrumentation compliance, the data generated are intended to indicate relative and not necessarily absolute property values.1.5 Test data obtained by this test method are relevant and appropriate for use in engineering design.1.6 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.NOTE 1: This test method is equivalent to ISO 6721, Part 5.1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

定价： 515元 / 折扣价： 438 元 加购物车

定价： 843元 / 折扣价： 717 元 加购物车