How is a tension test conducted according to ASTM E8?

2023/11/17

ASTM E8 is a commonly used standard for the specification of tensile testing of metallic materials. This test standard describes the requirements for sample preparation, test apparatus, test procedures and data analysis for tensile testing.

The following are the general steps for performing tensile tests in accordance with the ASTM E8 standard:

1. Sample Preparation:

- Tensile specimens are prepared from metallic materials in accordance with the requirements of the standard. Typically, the samples are of circular or rectangular cross-section.

- The dimensions of the sample and the length required by the standard shall be as specified in the standard. If it is not possible to comply with the requirements, it should be noted in the test report.

2. Clamping and clamping of samples:

- Select fixtures in accordance with the requirements of the standard and ensure that they are capable of applying uniform clamping force and holding the specimen in place.

- Use suitable fixtures to place the specimen on the tensile testing machine and ensure that the specimen is in the correct position on the fixture.

- It should be avoided that the edge of the specimen is too close to the fixture so that the influence of the fixture does not interfere with the evaluation of the specimen's performance.

3. Load calibration and displacement measurement:

- Calibrate the load and displacement transducers in the tensile testing machine according to the standard requirements and record the relevant calibration data.

- Ensure the accuracy and reliability of the load cell and displacement transducer.

4. Test Setting:

- Set the operating parameters of the testing machine, such as test speed and strain rate. These parameters should meet the requirements of the standard and be recorded in standard units.

- Provide an auto-stop function on the testing machine to ensure that the test is automatically stopped after the sample breaks.

5. Initial stress and initial strain:

- At a low strain rate, a certain initial load is applied which causes the specimen to enter a linear elastic phase. The load at this stage is called initial stress.

- Based on the dimensions of the specimen and the initial load, the initial strain is calculated.

6. Apply tensile force:

- After starting the test, the load is gradually increased until the specimen breaks.

- The test speed is controlled to apply the load at a constant rate to ensure a uniform increase in strain throughout the test.

7. Data Acquisition:

- Continuously record load-displacement curve data through load and displacement transducers on the testing machine.

- According to the standard requirements, select the appropriate sampling frequency to capture the key data points.

8. End of Test:

- Stop the test when the specimen breaks.

- Record the fracture location and evaluate the morphologic characteristics of the specimen fracture.

9. Data Analysis:

- Use the collected load-displacement data to calculate and evaluate the mechanical property parameters of the metallic material. These parameters may include yield strength, tensile strength, breaking strength, elongation, and so on.

Keep in mind that the above steps are a general description of the ASTM E8 standard tensile test. To ensure accurate and reliable test results, it is recommended that you refer to the ASTM E8 standard document and strictly follow the procedures and requirements therein.

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