ASTM-E21:2020 pdf free download – Standard Test Methods for Elevated Temperature Tension Tests of Metallic Materials.
6.1.1 Samples of the material to provide test specimens shall be taken from such locations as to be representative of the lot from
which it was taken.
6.1.2 Samples shall be taken from material in the final condition (temper). One test shall be made on each lot.
6. 1 .3 A lot shall consist of all material from the same heat, nominal size, and condition (temper).
7. Test Specimens and Sample
7.1 The size and shape of the test specimens should be based primarily on the requiremcnts necessary to obtain representative samples of the material being investigated.
7.2 Unless otherwise specified, test specimens shall be oriented such that the axis of the specimen is parallel to the direction of
fabrication, and located as follows:
7.2.1 At the center for products -1-1.5Vi in. (38 mm) or less in thickness, diameter, or distance between flats.
7.2.2 Midway from the center to the surface for products over -1-1.5J4 in. (38 mm) in thickness, diameter, or distance between flats.
7.3 Specimen configurations described in Test Methods E8/E8M, are generally suitable for tests at elevated temperatures; however, tighter dimensional tolerances are recommended in 7.6. The particular specimen used should he mainly governed by the requirements specified in 7. I. When the dimensions of the material permit, except for sheet and strip, the gauge length of the specimens should have a circular cross section. The largest diameter specimen consistent with that described in 7.1 should he used, except that the diameter need not be greater than 0.500 in. (12.7 mm). The ratio of gauge length to diameter should be 4, as for the standard specimens described in Test Methods E8/E8M. If different ratios are used, the specifics should be reixwted in the results. (Sec 11.1.4)
Nom 5—Specimen size in itself has little effect on tensile properties provided the material is not subject to appreciable surface corrosion, lack of soundness, or orientation effects. A small number of grains in the specimen cross section. or preferred orientation of grains due to fabrication conditions. can have a pronounced effect on the test results. When corrosion is a factor in testing. the results do become a function of specimen size. Likewise, surface preparation of specimens, if affecting results, becomes more important as the specimen size is reduced.
7.4 Specimens of circular cross section should have threaded, shouldered, or other suitable ends for gripping which will meet the requirements of 5.1.2.
Nom 6—Satisfactory axial alignment may he obtained with precisely machined threaded ends. But at temperatures where oxidation and creep are readily apparent, precisely fitted threads are difficult to maintain and to separate after test. Practical considerations require the use of relatively kxse-Iitting threads. Other gripping rnethxls have been successfully used.6
7.5 For rectangular specimens some modifications of’ the standard specimens described in Test Methods E8/E8M are usually necessary to permit application of the force to the specimen in the furnace with the axiality specified in 5.1 .2. If the material available is sufficient, the use of elongated shoulder ends to permit gripping outside the furnace is the easiest method. When the length of the specimen is necessarily restricted, several methods of gripping may be used as follows:
7.5.1 A device that applies the force through a cylindrical pin in each of the enlarged ends of the specimen. The pin holes should be accurately centered on extensions of the centerline of the gauge section. Grips of this type can provide good axiality of loading.5
7.5.2 High-temperature sheet grips similar to those illustrated in Test Methods E8/E8M and described as self-adjusting grips. These have proven satisfactory for testing sheet materials that cannot be tested satisfactorily in the usual type of wedge grips.