How to Choose the Right Tensile Strength Testing Machine for Plastic or Metal Samples

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A Tensile Strength Testing Machine is used to determine the strength, elongation, and deformation behavior of materials when subjected to a pulling force. Selecting the right machine depends on the material being tested, specimen dimensions, expected breaking force, and applicable testing standards.

1. Identify the Material You Need to Test​

The first step is to identify whether you will be testing plastics, metals, or other materials.

• Plastic samples: Plastic films, sheets, molded components, and polymer specimens generally require suitable grips and accurate measurement of elongation. Depending on the sample, a lower-capacity testing machine may be sufficient.
• Metal samples: Steel, aluminum, copper, and other metals may require higher load capacities because their tensile strength and specimen cross-sectional areas can be significantly greater.
• Rubber and flexible materials: These typically require specialized grips and sufficient extension capacity to measure elongation accurately.

2. Select the Appropriate Load Capacity​

The required load capacity depends on the material's tensile strength and the cross-sectional area of the specimen.

The approximate breaking force can be calculated using:

Breaking Force (N) = Tensile Strength (MPa) × Cross-sectional Area (mm²)

For example, if a metal specimen has a tensile strength of 400 MPa and a cross-sectional area of 10 mm², its approximate breaking force is:

400 × 10 = 4,000 N, or 4 kN.

The selected machine must safely accommodate the expected force, with an appropriate capacity margin.

Typical starting points for selecting a machine are:

• 1–5 kN: Thin plastic films, flexible polymers, and low-force specimens.
• 5–20 kN: Many plastic specimens, polymer sheets, and smaller material samples.
• 20–50 kN: Stronger plastics, composite samples, and some smaller metal samples.
• 50–100 kN or higher: Many metal specimens and applications involving higher breaking forces.

These ranges are indicative, not universal. The correct capacity must be calculated for the actual specimen and test method.

3. Check the Applicable Testing Standards​

Choose a machine that supports the relevant test method. Common examples include:

• ASTM D638: Tensile properties of plastics.
• ISO 527: Tensile properties of plastics.
• ASTM E8/E8M: Tension testing of metallic materials.
• ISO 6892-1: Tensile testing of metallic materials at room temperature.

The machine's force measurement accuracy, testing speed, extensometer, and gripping arrangements should meet the applicable requirements.

4. Consider Grips, Extensometers, and Software​

The machine should have grips suited to the sample geometry and material. Pneumatic or suitable mechanical grips may be useful for plastics, while wedge grips are commonly used for metal specimens.

An extensometer can measure strain accurately, particularly when determining elastic properties. Software should provide relevant results such as maximum force, tensile strength, elongation at break, and stress-strain curves.

5. Choose a Reliable Testing Machine​

When selecting a Tensile Strength Testing Machine, consider load capacity, force accuracy, test speed, specimen dimensions, calibration requirements, and after-sales support. A machine with an unnecessarily high capacity may reduce measurement resolution for low-force samples if the appropriate load cell is not selected.

Presto Stantest Pvt. Ltd. provides material testing solutions for industrial quality control. Before selecting a machine, share your sample material, dimensions, expected tensile strength, and applicable testing standard with the manufacturer to identify a suitable configuration.

Surgery​

The right tensile testing machine should match the expected breaking force, specimen geometry, and required testing standard. For many plastic applications, capacities in the 1–20 kN range may be a useful starting point, while metal testing often requires higher capacities. Always calculate the expected force before finalizing the machine capacity.