ASTM A370:19e1 pdf free download – Standard Test Methods and Definitions for Mechanical Testing of Steel Products.
OA, and thus locate r, the intersection of inn with the stress-strain curve corresponding to load R, which is the yield-strength load. In recording values of yield strength obtained by this method, the value of offset specified or used, or both, shall be stated in parentheses after the term yield strength, for example:
NOTE 9—For stress-strain diagrams not containing a distinct modulus,
such as for some cold-worked materials, it is recommended that the extension under load method he utilized, lithe offset method is used thr materials without a distinct modulus, a modulus value appropriate for the material being tested should he used: 30 psi (207 0(X) MPa) ftr carbon steel; 29 000 000 psi (200000 MPa) for fcrritic stainless steel;
28000 000 psi (193 0 MPa) for austenitic stainless steel. For special alloys, the producer should be contacted to discuss appropriate modulus values.
14.2.2 Extensio,z Under Load Method—For tests to determine the acceptance or rejection of material whose stress-strain characteristics are well known from previous tests of similar material in which stress-strain diagrams were plotted, the total strain corresponding to the stress at which the specified offset (see Notes 10 and 11) occurs will be known within satisfactory limits. The stress on the specimen, when this total strain is reached, is the value of the yield strength. In recording values of yield strength obtained by this method, the value of “extension” specified or used, or both, shall he stated in parentheses after the term yield strength, for example:
Yield strength (0.5% EUL) = 52000 psi (360 MPa) (2)
The total strain can be obtained satisfactorily by use of a Class B 1 extensometer (Note 5, Note 6, and Note 8).
NOTE 10—Automatic devices are available that determine offset yield strength without plotting a stress-strain curve. Such devices may be used if their accuracy has been demonstrated.
NOTE 11—The appropriate magnitude of the extension under load will obviously vary with the strength range of the particular steel under test. In general. the value of extension under load applicable to steel at any
strength level may be determined from the sum of the proportional strain and the plastic strain expected at the specified yield strength. The following equation is used:
Extension under load. in./in. of gauge length = (YSIE) + r (3)
where:
YS = specified yield strength, psi or MPa,
E = modulus of elasticity, psi or MPa, and
r = limiting plastic strain, in./in.
14.3 Tensile Strength—Calculate the tensile strength by dividing the maximum load the specimen sustains during a tension test by the original cross-sectional area of the spec imen. if the upper yield strength is the maximum stress recorded and if the stress-strain curve resembles that of Test Methods E8/E8M—15a Fig. 25, the maximum stress after discontinuous yielding shall be reported as the tensile strength unless otherwise stated by the purchaser.