ASTM A370 – Quiz 9 TENSION TEST

9. Test Specimen Parameters

9.1 Selection—Test coupons shall be selected in accordance with the applicable product specifications.

9.1.1 Wrought Steels—Wrought steel products are usually tested in the longitudinal direction, but in some cases, where size permits and the service justifies it, testing is in the transverse, radial, or tangential directions (see Figs. 1 and 2).

9.1.2 Forged Steels—For open die forgings, the metal for tension testing is usually provided by allowing extensions or prolongations on one or both ends of the forgings, either on all or a representative number as provided by the applicable product specifications. Test specimens are normally taken at mid-radius. Certain product specifications permit the use of a representative bar or the destruction of a production part for test purposes. For ring or disk-like forgings test metal is provided by increasing the diameter, thickness, or length of the forging. Upset disk or ring forgings, which are worked or extended by forging in a direction perpendicular to the axis of the forging, usually have their principal extension along concentric circles and for such forgings tangential tension specimens are obtained from extra metal on the periphery or end of the forging. For some forgings, such as rotors, radial tension tests are required. In such cases the specimens are cut or trepanned from specified locations.

9.2 Size and Tolerances—Test specimens shall be (1) the full cross section of material, or (2) machined to the form and dimensions shown in Figs. 3-6. The selection of size and type of specimen is prescribed by the applicable product specification. Full cross section specimens shall be tested in 8-in. (200 mm) gauge length unless otherwise specified in the product specification.

9.3 Procurement of Test Specimens—Specimens shall be extracted by any convenient method taking care to remove all distorted, cold-worked, or heat-affected areas from the edges of the section used in evaluating the material. Specimens usually have a reduced cross section at mid-length to ensure uniform distribution of the stress over the cross section and localize the zone of fracture.

9.4 Aging of Test Specimens—Unless otherwise specified, it shall be permissible to age tension test specimens. The time temperature cycle employed must be such that the effects of previous processing will not be materially changed. It may be accomplished by aging at room temperature 24 h to 48 h, or in shorter time at moderately elevated temperatures by boiling in water, heating in oil or in an oven.

9.5 Measurement of Dimensions of Test Specimens:

9.5.1 Standard Rectangular Tension Test Specimens—Thee forms of specimens are shown in Fig. 3. To determine the cross-sectional area, the center width dimension shall be measured to the nearest 0.005 in. (0.13 mm) for the 8-in. (200 mm) gauge length specimen and 0.001 in. (0.025 mm) for the 2-in. (50 mm) gauge length specimen in Fig. 3. The center thickness dimension shall be measured to the nearest 0.001 in. for both specimens.

9.5.2 Standard Round Tension Test Specimens—These forms of specimens are shown in Fig. 4 and Fig. 5. To determine the cross-sectional area, the diameter shall be measured at the center of the gauge length to the nearest 0.001 in. (0.025 mm) (see Table 1).

9.6 General—Test specimens shall be either substantially full size or machined, as prescribed in the product specifications for the material being tested.

9.6.1 It is desirable to have the cross-sectional area of the specimen smallest at the center of the gauge length to ensure fracture within the gauge length. This is provided for by the taper in the gauge length permitted for each of the specimens described in the following sections.

9.6.2 For brittle materials it is desirable to have fillets of large radius at the ends of the gauge length.