ASTM E8M Tension Testing of Metallic Materials

Introduction

For the purpose of conducting tension testing on metallic materials, ASTM International (previously the American Society for Testing and Materials) established ASTM E8M, a standard test procedure. The standard is fully named “Standard Test Methods for Tension Testing of Metallic Materials.”  A popular technique for figuring out crucial mechanical characteristics of metallic materials, like yield strength, ultimate tensile strength, elongation, and area reduction, is tension testing. A comprehension of the material’s behavior under tensile (pulling or stretching) pressures requires a comprehension of these properties.

ASTM E8M Tension Testing of Metallic Materials

ASTM E8 / E8M or ASTM A370 are widely used test methods for determining the tensile characteristics of metals. The oldest metal testing standard, ASTM E8-24T, was initially split into two standards, E8 for imperial units and E8M for metric ones. ASTM E8 / E8M is used to measure yield strength, tensile strength, and area reduction. The standard specifies a wide range of specimen types and sizes, including bars, tubes, sheets, pin-loaded specimens, round specimens, and powdered metallurgy products. Test procedures include Stress Rate Control, Strain Rate Control, and Crosshead Displacement Control. Grips can be grouped into proportional and non-proportional grips, depending on how they apply clamping force to the specimen. Proportional grips are directly proportional to the applied tensile load, while non-proportional grips have a constant clamping force due to a power source not directly related to the specimen’s tension loading.

Proportional grips can minimize undesired compressive forces generated during test setup, ensuring accurate results. The Instron 5900 Series features Specimen Protect, which automatically adjusts the crosshead location during setup to remove compressive force. High-precision instruments are needed for measuring modulus and yield, while lower-precision instruments measure uniform elongation and total elongation at high strain levels. Three common types of extensometers are clip-on, non-contacting, and automatic contacting extensometers for ASTM E8 testing. The 2630 Series is the most popular type, offering accurate and steady strain data. The AutoX750 is an automatic contacting device that can be programmed to remove itself before specimen failure, protecting knife edges from wear. The AVE 2 Automatic Video Extensometer eliminates potential bias caused by the extensometer’s physical contact with the specimen. Buehill Universal provides calculations for ASTM E8/E8M testing, as well as pre-built methods to ISO 6892-1, EN10002, ISO 10113, and ISO 10275. To boost throughput, grips and extensometers with lower setup time and higher repeatability can be used, and fully automated testing procedures can be conducted without human intervention.

The Following Test Techniques are Covered by the Standard:

• Method A: Yield Strength Test: This technique includes offsetting the stress-strain curve by a certain amount in order to ascertain the yield strength of a material. An essential factor in determining whether a material experiences plastic deformation is its yield strength.
• Approach B: Yield Strength Test by 0.2% Offset: This approach, like Method A, uses a 0.2% offset to determine the yield strength.
• Approach C: Test for Yield Strength by Total Elongation: Using this approach, the yield strength is ascertained by measuring the specimen’s total elongation.
• Procedure D: Yield Strength Test with Extensometer: In this procedure, strain is measured to determine yield strength using an extensometer.
• Approach E: Test for Yield Strength by Tangent Modulus: Using this approach, the tangent modulus is measured in order to calculate the yield strength.
• Method F: Yield Strength Test by Center-Load Tensile Test: This test measures the yield strength based on a given total strain and is suitable for materials that do not display a yield point.
• Materials that are too small or too thin to meet the dimensional specifications for typical tension test specimens are tested using Method G, or Bend Test.
• The purpose of Method H, the Test for Strain-Controlled Fatigue capabilities, is to ascertain the metallic materials’ strain-controlled fatigue capabilities.

Video 01: 10- ASTM E8—Tension Testing of Metallic Materials