ASME SA370:2015 pdf free download – TEST METHODS AND DEFINITIONS FOR MECHANICAL TESTING OF STEEL PRODUCTS
7.2 The tension testing machine shall be maintained in good operating condition, used only in the proper loading range, and calibrated periodically in accordance with the latest revision of Practices E 4. NOTE 1 — Many machines are equipped with stress-strain recorders for autographic plotting of stress-strain curves. It should be noted that some recorders have a load measuring component entirely separate from the load indicator of the testing machine. Such recorders are calibrated separately.
7.3 Loading — It is the function of the gripping or holding device of the testing machine to transmit the load from the heads of the machine to the specimen under test. The essential requirement is that the load shall be transmitted axially. This implies that the centers of the action ofthe grips shall be in alignment, insofaras practica- ble, with the axis of the specimen at the beginning and during the test and that bending or twisting be held to a minimum. For specimens with a reduced section, gripping of the specimen shall be restricted to the grip section. In the case of certain sections tested in full size, nonaxial loading is unavoidable and in such cases shall be permis- sible.
7.4 Speed ofTesting — The speed of testing shall not be greater than that at which load and strain readings can be made accurately. In production testing, speed of testing is commonly expressed: (1) in terms offree running cross- head speed (rate of movement of the crosshead of the testing machine when not under load), (2) in terms of rate ofseparation ofthe two heads ofthe testing machine under load, (3) in terms of rate of stressing the specimen, or (4) in terms of rate of straining the specimen. The following limitations on the speed of testing are recommended as adequate for most steel products: NOTE 2 — Tension tests using closed-loop machines (with feedback control of rate) should not be performed using load control
8.1.1 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 Fig. 1 and Fig. 2).
8.1.2 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 pro- vided by the applicable product specifications. Test speci- mens 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 forg- ing, 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 ten- sion tests are required. In such cases the specimens are cut or trepanned from specified locations.