Types of Tensile Testing: Methods and Material Applications
Representative Infinita Engineering Visual showing tensile specimen preparation, axial loading, and property evaluation for Tensile Testing Types.Why Tensile Testing Standards Differ by Material
Tensile testing follows the same basic principle across all material classes — pull a standardised specimen until it fails and record the resulting stress-strain behaviour — but the specimen geometry, grips, strain rates, and even the properties reported differ significantly depending on what’s being tested. Using the wrong standard specimen geometry or speed for a given material class produces data that isn’t comparable to the rest of the industry.
Tensile Testing Procedures
In general, the following instruments are required for tension testing:
- Normative test apparatus chassis
- Indicator and/or controller for a load cell
- Fixturing and grips to secure your sample
The universal testing machine’s chassis is sturdy and stiff enough to facilitate the required rate of sample separation. There is a large selection of capacities and types of frames, including electromechanical and servo-hydraulic styles. Selecting a frame that can take the required amount of force throughout the test is crucial.
The force exerted on a sample can be determined with the help of a load cell. These, like frames, can hold a wide range of contents. If the breaking strength of the sample is lower than the capacity of the load cell, the load cell will fail before the sample. However, if the capacity of the load cell is too high, the test results may not be as precise as required since the normal resolution of load cells is only 1%. A load cell with a capacity of 1,000 pounds would be completely overkill for a sample that cracks under just one pound of force.
The necessity for a controller and/or an indication arises from the specifics of the system configuration. During testing, the controller regulates variables such as the test frame’s velocity and movement. An indicator may be sufficient in some cases. Indicators record and show test results but do not operate the apparatus.
Tension grips using hand vices. Tensile testing can be performed with a wide variety of grips and fixtures. Fixtures designed for one material may not work for another. Different types of grips are needed for various samples because of their dissimilar responses to tensile pressures. The key to getting reliable outcomes from your application is picking the right grips.
Also Read – Tension, Shear & Bending Joints: Key Differences & Testing Methods
Metals: ASTM E8/E8M
Covers tension testing of metallic materials using round or flat “dog-bone” specimens with a 4D gauge length convention (four times the specimen diameter) for round bars. Reports yield strength (typically via 0.2% offset), ultimate tensile strength, elongation, and reduction of area. Testing machines commonly range from 50 kN to 600 kN depending on material strength.
Plastics: ASTM D638
Covers unreinforced and reinforced plastics up to 14 mm thick, using dumbbell-shaped specimens in five defined types (I through V) selected by material thickness. Crosshead speed is chosen from five defined rates (1, 2, 5, 10, or 50 mm/min) based on whether modulus/yield (slower speed) or elongation at break (faster speed) is the target property. Thin film under 1.0 mm uses ASTM D882 instead.
Rubber and Elastomers: ASTM D412
Covers vulcanised and thermoplastic elastomers using dumbbell or ring-shaped specimens, typically pulled at much higher crosshead speeds and elongations than rigid materials, since elastomers can commonly stretch several hundred per cent before failure.
Thin Film: ASTM D882
Designed specifically for plastic sheeting and film under 1.0 mm thick, where standard D638 dumbbell geometry isn’t practical. Uses simple rectangular strip specimens rather than a dumbbell shape.
Composites: ASTM D3039
Covers continuous fibre-reinforced polymer matrix composites — unidirectional, cross-ply, angle-ply, and woven layups. Requires balanced, symmetric layups to prevent twisting under load, and commonly uses bonded tabs to protect the gripping area. Load capacity requirements are higher than for plastics, often 30-300 kN depending on fibre type.
Comparing Across Standards
- Metals (E8): highest load capacity requirement, precise 0.2% offset yield determination
- Plastics (D638): moderate load, variable crosshead speed by specimen type and target property
- Rubber (D412): high elongation capability, minimal load requirement
- Film (D882): thin-specimen-specific grips and low load capacity
- Composites (D3039): highest load requirement for carbon fibre, tabbing essential, layup-dependent results
Industry Specifications Referencing Tensile Testing Types
- ASTM E8/E8M, D638, D412, D882, D3039: the core material-specific tensile standards
- ISO 6892, ISO 527, ISO 37: international equivalents for metals, plastics, and rubber respectively
Also Read – Thermoplastic Polymers: Applications, Testing & Key Standards Guide
Conclusion
Selecting the correct tensile standard for the material class isn’t a formality — it determines the specimen geometry, grip type, load capacity, and test speed needed to generate a valid, industry-comparable result, and mismatching a standard to a material produces numbers that look plausible but aren’t meaningful.
What is uniaxial tensile testing? Uniaxial tensile testing applies force along one direction until the specimen deforms or fractures. It is the most common method for measuring tensile strength, yield strength, modulus, and elongation.
How is tensile testing performed on metals? Metal specimens are typically machined into round or flat shapes and tested using a universal testing machine. ASTM E8/E8M and ISO 6892-1 are commonly used for room-temperature tensile testing.
How are plastics tested in tension? Plastic specimens are usually molded or machined into dumbbell-shaped samples. Testing measures tensile strength, modulus, elongation, and behavior at break, commonly following ASTM D638 or ISO 527.
How is tensile testing performed on composites? Composite specimens are tested in specific fiber orientations because their properties vary with direction. ASTM D3039 is commonly used for polymer-matrix composites, with tabs often added to prevent grip damage.
What is tensile testing of films and thin sheets? Thin films, foils, and flexible sheets require specialized grips to prevent slipping or tearing. ASTM D882 is commonly used to evaluate the tensile properties of thin plastic sheeting.
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