Hi Jayaprakash Polamarasetty,

Tensile test specimens and fatigue test specimens serve different purposes in materials testing:

1. Sample Size: Tensile test specimens are usually larger than fatigue test specimens, as they need to withstand a single, gradual application of force until failure. Fatigue test specimens are smaller because they are subjected to cyclic loading that induces fatigue failure over time.

2. Sample Radius: Tensile specimens often have a larger cross-section with a constant radius, while fatigue specimens have a smaller radius to create a stress concentration that promotes fatigue failure.

3. Gage Length: Tensile specimens have a defined gage length where measurements are taken, whereas fatigue specimens have a shorter gage length due to the cyclic nature of the loading.

4. Parallel Length: The parallel length of a tensile specimen is longer than that of a fatigue specimen, allowing for more uniform stress distribution during testing.

5. Surface Finish: Tensile specimens have a smoother surface finish to minimize surface defects that could lead to premature failure. Fatigue specimens may have a rougher finish to enhance stress concentration effects.

6. Axis of Faces: In tensile specimens, the axis of the faces is perpendicular to the loading direction, whereas in fatigue specimens, the axis of the faces can be slightly tilted to induce a bending effect that enhances fatigue failure.

Keep in mind that these differences may vary based on the specific testing standards and materials. Always refer to relevant standards when preparing specimens for testing.

Kind regards

fatigue testing is a cyclic loading process, for long timing, unlike tensile. The size of specimen varies with the type of fatigue you have to do and which point is fatigue test to be done, of course the dimension could be different from tensile test.

Tensile Test Specimen:

• Sample Size: Tensile test specimens are generally longer and narrower compared to fatigue test specimens.
• Sample Radius: Tensile test specimens typically have a uniform cross-section along their length and do not have a specific radius.
• Gage Length: The gage length of a tensile test specimen is the length of the region over which strain measurements are made during the test. It is typically longer compared to fatigue test specimens.
• Parallel Length: The parallel length is the length of the specimen where the cross-section remains constant. In tensile test specimens, the parallel length is generally longer than in fatigue test specimens.
• Surface Finish: Tensile test specimens usually have a smoother surface finish to minimize the effects of surface roughness on the test results.
• Axis of Faces: The faces of a tensile test specimen are generally parallel to each other.

Fatigue Test Specimen:

• Sample Size: Fatigue test specimens are usually shorter and wider compared to tensile test specimens.
• Sample Radius: Fatigue test specimens may have a specific radius or notch to promote the initiation of fatigue cracks at a desired location.
• Gage Length: The gage length in fatigue test specimens is generally shorter compared to tensile test specimens.
• Parallel Length: The parallel length in fatigue test specimens is generally shorter compared to tensile test specimens.
• Surface Finish: Fatigue test specimens may have a rougher surface finish to promote crack initiation and propagation during the test.
• Axis of Faces: The faces of a fatigue test specimen may not be perfectly parallel to each other due to the presence of notches or radii, which are used to induce stress concentrations.

It's important to note that the specific dimensions and characteristics of test specimens can vary depending on the testing standards, materials, and specific experimental requirements. It's advisable to refer to the relevant testing standards or guidelines to obtain accurate and detailed specifications for each type of test specimen.

The tensile test is a 1/4 cycle Low cyclic (high strain) fatigue test. See Bela Sandor's Book "Fundamentals of cyclic stress and Fatigue" University Wisconsin Press 1972, and learn.

I agree with Ameer K Ibraheem and add that in most cases fatigue test is carried out at bending.