ASTM International - ASTM E1681-03(2008)
Standard Test Method for Determining a Threshold Stress Intensity Factor for Environment-Assisted Cracking of Metallic Materials
|Publication Date:||1 November 2008|
|ICS Code (Metal structures):||91.080.10|
significance And Use:
The parameters KEAC or KIEAC determined by this test method characterize the resistance to crack growth of a material with a sharp crack in specific environments under... View More
The parameters KEAC or KIEAC determined by this test method characterize the resistance to crack growth of a material with a sharp crack in specific environments under loading conditions in which the crack-tip plastic region is small compared with the crack depth and the uncracked ligament. The less restrictive thickness requirements of KEAC are intended for those conditions in which the results are a strong function of the thickness of the specimen and the application requires the testing of specimens with thickness representative of the application. Since the chemical and mechanical influences cannot be separated, in some material/environment
The apparent KEAC or KIEAC of a material under a given set of chemical and electrochemical environmental conditions is a function of the test duration. It is difficult to furnish a rigorous and scientific proof for the existence of a threshold (4, 5). Therefore, application of KEAC or KIEAC data in the design of service components should be made with awareness of the uncertainty inherent in the concept of a true threshold for environment-assisted
The degree to which force deviations from static tensile stress will influence the apparent KEAC or KIEAC of a material is largely unknown. Small-amplitude cyclic loading, well below that needed to produce fatigue crack growth, superimposed on sustained tensile loading was observed to significantly lower the apparent threshold for stress corrosion cracking in certain instances (7, 8). Therefore, caution should be used in applying KEAC or KIEAC data to service situations involving cyclic loading. In addition, since this standard is for static loading, small-amplitude cyclic loading should be avoided during testing.
In some material/environment
The user may optionally determine and report a KEAC value or a KIEAC value. The specimen size validity requirements for a KEAC value meet the size requirements developed for Test Method E 647 to achieve predominately elastic behavior in the specimen. Test Method E 647 size requirements for compact specimens should be applied to both the compact specimen and the beam specimen. The specimen size validity requirements for a KIEAC value meet the size requirements developed for plane strain conditions for Test Method E 399.
Evidence of environment-assisted
Not all combinations of material and environment will result in environment-assisted
In research and development, valid KEAC or KIEAC data can quantitatively establish the effects of metallurgical and environmental variables on the environment-assisted
In service evaluation, valid KEAC or KIEAC data can be utilized to establish the suitability of a material for an application with specific stress, flaw size, and environmental conditions.
In acceptance and quality control specifications, valid KEAC or KIEAC data can be used to establish criteria for material processing and component inspection.
Test results will be affected by force relaxation in constant displacement bolt-loaded compact specimens for some material/environment
Residual stresses can have an influence on environment-assisted
For bolt loaded specimens, the user should realize that material being tested at an non-ambient temperature may have a different displacement-to-forc
1.1 This test method covers the determination of the environment-assisted
1.2 This test method is applicable to environment-assisted
1.3 Materials that can be tested by this test method are not limited by thickness or by strength as long as specimens are of sufficient thickness and planar size to meet the size requirements of this test method.
1.4 A range of specimen sizes with proportional planar dimensions is provided, but size may be variable and adjusted for yield strength and applied force. Specimen thickness is a variable independent of planar size.
1.5 Specimen configurations other than those contained in this test method may be used, provided that well-established stress intensity calibrations are available and that specimen dimensions are of sufficient size to meet the size requirements of this test method during testing.
1.6 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 and health practices and determine the applicability of regulatory limitations prior to use.