Standards Related to G39 – G G Standard ASTM Standards Related to Corrosion Testing of Metals · Annual Book of ASTM Standards Online: Hello everyone, I am looking for ASTM G39 – 99() Standard Practice for Preparation and Use of Bent-Beam Stress- Corrosion Test Specimens. Please. ASTM G39 – 99() – 弯曲梁应力腐蚀试验试样制备和使用标准规程.
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For plate material the bent-beam specimen is more difficult to use because more rugged specimen holders must be built to accommodate the specimens. To obtain more accurate stress values, use a prototype specimen, astmm with strain gages, for calibration. The equations must not be used above the yield strength of the material.
Note 1-It is the nature of these methods that only the applied stress can be calculated. In both sustained and alternate immersion, the solution volume should be large enough to prevent depletion asym corrosive agents.
Thus, the use of the elastically stressed bent-beam specimens for materials evaluation is of limited value. By proper choice of holder and insulator materials, however, many plastics can be used, especially in short-time tests. A description of such a specimen is given by Wilson and Spier 5. A convenient stressing jig is shown in Fig. For testing in the plastic range, U-bend specimens should be employed see Practice G Support the specimen at the ends and bend the specimen by forcing a screw equipped with a ball or knife-edge tip against it at the point halfway between the end supports in a fashion shown in Fig.
If specimen holders or insulators are made of such materials, the applied stress on the specimen may change appreciably with time. This relationship can be used as a simple check to ensure that the maximum stress does not exceed the proportional limit.
Last previous edition approved in as G39—99 Care must be taken to prevent the identi? Permission rights to photocopy the standard may also be secured from the ASTM website www. The prototype specimen should have the same dimensions as the test specimens and should be stressed in the same way.
A double-beam modification of a four-point loaded specimen to utilize heavier materials is described in Thus, the errors in the applied stress are related to those inherent in the use of measuring instruments micrometers, de?
Although it is possible to stress bent-beam specimens into the plastic range, the stress level cannot be calculated for plastically-stressed three- and four-point loaded specimens as well as the double-beam specimens. The stressed specimens then are exposed to the test environment and the time required for cracks to develop is determined. Information is available from http: From the contact with the spacer the stress decreases linearly toward zero at the ends of specimens.
Since stress-corrosion cracking is a function of the total stress, for critical applications and proper interpretation of results, the residual stress before applying external stress or the total elastic stress after applying external stress should be determined by appropriate nondestructive methods, such as X-ray diffraction 1. The stress conditions are not usually known and a wide range of stresses exist in a single stressed specimen. The bent-beam specimen is very well suited for establishing the relative merits of several alloys for the relative severity of several environments.
The advantage of the U-bend specimen is that it is simple and economical to make and use. On the other hand, magnitude and direction of residual stresses frequently are difficult to predict and also difficult to measure. Once cracking has initiated, the state of stress at the tip of the crack as well as in uncracked areas has changed, and therefore, the known or calculated stress or strain values discussed in this practice apply only to the state of stress existing before initiation of cracks.
It is desirable to remove the required amount of metal in several steps by alternately grinding opposite surfaces.
Furthermore, the pressure of the central support at the aetm of highest load introduces biaxial stresses at the area of contact and could introduce tension stresses where normally compression stresses are present. 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.
Individual reprints single or multiple aastm of this standard may be obtained by contacting ASTM at the above address or at phonefaxor service astm. It should also be noted that presence of voluminous corrosion products may obscure cracks, thus making a careful examination mandatory. These intervals are usually increased as the test progresses because the logarithms of observed cracking times are often normally distributed as described by Loginow 6 and by Booth et al 8.
Stress calculations by this practice are not applicable to plastically stressed specimens. For testing in the plastic range, U-bend specimens should be employed see Practice G NOTE 2—The double-beam specimen, more fully described in The specimen is therefore unsuitable for studying the effects of different applied stresses on stress-corrosion cracking or for studying variables which have only a minor effect on cracking.
If stenciling is used for identi?
The specimen is most easily made from strip or sheet but can be machined from plate, bar, castings, or weldments; wire specimens may be used also. Referenced Documents purchase separately The documents listed below are referenced within the subject standard but are not provided as part of the standard. Depending on the degree of restraint, residual stresses may even exceed the initial yield strength of the material.
NOTE 5—In atmospheres gas galvanic action between specimen and holder either does not exist or is con?
ASTM G30 – 97() Standard Practice for Making and Using U-Bend Stress-Corrosion Test Specimens
NOTE 8—If the test is to be conducted in an electrolyte, the spacer shall be made of the same material as the specimen or of an electrically nonconducting material such as glass, ceramic, and so forth to prevent galvanic action between specimen and spacer.
This practice applicable to specimens of any metal that are stressed to levels less than the elastic limit of the material, and therefore the applied stress can be accurately calculated or measured Note 1.
Since stress-corrosion cracking is a function of the total stress, for critical applications and proper interpretation of results, the residual stress before applying external stress or the total elastic stress after applying external stress should be determined by appropriate nondestructive methods, such as X-ray diffraction 1. Referenced Documents purchase separately The documents listed below are referenced within the subject standard but are not provided as part of the standard.
To facilitate calculations, a computer can be used to generate a table for a range of strain? Typical U-bend configurations showing several different methods of maintaining the applied stress are shown in Fig. Please contact us if you need any help.
The calculated stress applies only to the state of stress before initiation of cracks. 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. If it should exceed the proportional limit, the measured de?