Prueba de tension

Designation: E 8/E 8M – 08

American Association State Highway and Transportation Officials Standard AASHTO No.: T68 An American National Standard

Standard Test Methods for

Tension Testing of Metallic Materials1
This standard is issued under the fixed designation E 8/E 8M; the number immediately following the designation indicates the year of original adoption or, in the case of revision,the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon (e) indicates an editorial change since the last revision or reapproval. This standard has been approved for use by agencies of the Department of Defense.

1. Scope* 1.1 These test methods cover the tension testing of metallic materials in any form at room temperature, specifically,the methods of determination of yield strength, yield point elongation, tensile strength, elongation, and reduction of area. 1.2 The gage lengths for most round specimens are required to be 4D for E 8 and 5D for E 8M. The gage length is the most significant difference between E 8 and E 8M Test Specimens Test specimens made from powder metallurgy (P/M) materials are exempt from this requirement byindustry-wide agreement to keep the pressing of the material to a specific projected area and density. 1.3 Exceptions to the provisions of these test methods may need to be made in individual specifications or test methods for a particular material. For examples, see Test Methods and Definitions A 370 and Test Methods B 557, B 557M. 1.4 Room temperature shall be considered to be 10 to 38°C [50 to 100°F]unless otherwise specified. 1.5 The values stated in SI units are to be regarded as separate from inch/pound units. The values stated in each system are not exact equivalents; therefore each system must be used independently of the other. Combining values from the two systems may result in non-conformance with the standard. 1.6 This standard does not purport to address all of the safety concerns,if any, associated with its use. 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. 2. Referenced Documents 2.1 ASTM Standards: 2

A 356/A 356M Specification for Steel Castings, Carbon, Low Alloy, and Stainless Steel, Heavy-Walled for Steam Turbines A 370 Test Methodsand Definitions for Mechanical Testing of Steel Products B 557 Test Methods for Tension Testing Wrought and Cast Aluminum- and Magnesium-Alloy Products B 557M Test Methods for Tension Testing Wrought and Cast Aluminum- and Magnesium-Alloy Products [Metric] E 4 Practices for Force Verification of Testing Machines E 6 Terminology Relating to Methods of Mechanical Testing E 29 Practice for UsingSignificant Digits in Test Data to Determine Conformance with Specifications E 83 Practice for Verification and Classification of Extensometer Systems E 345 Test Methods of Tension Testing of Metallic Foil E 691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method E 1012 Practice for Verification of Test Frame and Specimen Alignment Under Tensile and Compressive AxialForce Application E 1856 Guide for Evaluating Computerized Data Acquisition Systems Used to Acquire Data from Universal Testing Machines 3. Terminology 3.1 Definitions—The definitions of terms relating to tension testing appearing in Terminology E 6 shall be considered as applying to the terms used in these test methods of tension testing. Additional terms being defined are as follows: 3.1.1discontinuous yielding—in a uniaxial test, a hesitation or fluctuation of force observed at the onset of plastic deformation, due to localized yielding. (The stress-strain curve need not appear to be discontinuous.) 3.1.2 elongation at fracture—the elongation measured just prior to the sudden decrease in force associated with fracture. For many materials not exhibiting a sudden decrease in force, the...