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A tensile test pulls a specimen of known shape apart at a controlled rate while recording force and elongation, so that strength and ductility can be calculated from the result. This guide is for materials-science and quality-control lab staff who need to pick the right standard, understand the machine and specimen, and read the resulting stress-strain curve. The right standard depends on the material: ASTM E8/E8M for metals, ASTM D638 for plastics, ASTM D412 for rubber.
What is a tensile test?
A tensile test (also called a tension test or tensile strength test) is a standardized, quasistatic, destructive method. The specimen is clamped between two crossheads, one of which moves at constant velocity until the specimen fails. Force and elongation are recorded throughout, and stress and strain are computed from the specimen’s original dimensions (ZEISS, read 2026-11-07).
ASTM E8/E8M states that tension tests provide information on the strength and ductility of materials under uniaxial tensile stress, and that the results are useful for comparison of materials, alloy development, quality control and design (ASTM E8/E8M-25, section 4.1). The standard lists the properties it determines for metals: yield strength, yield point elongation, tensile strength, elongation and reduction of area.
How a tensile test machine works
A tensile tester (universal testing machine in tension mode) has a fixed crosshead and a movable crosshead, driven hydraulically or electrically, with grips that hold the specimen. Table-top machines start at about 3 kN and the range extends up to 2,000 kN (ZEISS). Strain is measured with an extensometer, either a contact clip-on type or a non-contact optical type.
The force measurement of the machine is itself checked against a standard: ISO 7500-1 covers verification of the force measuring system of tension/compression testing machines, and ISO 5893 covers testing machines for plastics and rubber (both named by ZEISS).
Tensile test specimens, including the dog bone shape
ZEISS names two basic specimen forms: round specimens for solid material and flat specimens for sheet metal. The enlarged ends are gripped; the narrower central section is where deformation and failure are intended to happen. Specimens with wide gripped ends and a narrow middle are informally called dog bone specimens. Exact dimensions come from the governing standard, not from this page.
For round metal specimens, ASTM E8/E8M states: “The gauge lengths for most round specimens are required to be 4D for E8 and 5D for E8M” (D is the specimen diameter; powder-metallurgy materials are treated separately in the standard). Reading E8 and E8M as the same gauge length is a common mix-up, so confirm which of the two you are working to.
ASTM and ISO tensile test standards by material
| Standard | Material it covers | What it governs |
|---|---|---|
| ASTM E8/E8M-25 (active, updated 2025-08-26) | Metallic materials, any form, room temperature | Tension testing; yield strength, yield point elongation, tensile strength, elongation, reduction of area |
| ISO 6892-1 (DIN EN ISO 6892-1) | Metals | Tensile test method for metals (named by ZEISS) |
| ISO 7500-1 | Testing machine | Verification of machine force measurement (named by ZEISS) |
| ISO 5893 | Testing machine for plastics and rubber | Machine requirements (named by ZEISS) |
| ASTM D638 | Plastics | See ASTM D638 |
| ASTM D412 | Vulcanized rubber and thermoplastic elastomers | See ASTM D412 |
To locate and cite a standard, see the guides to ASTM Compass and citing ASTM standards.
Reading the stress-strain curve
ZEISS describes these features of the curve, and each corresponds to a reported property:
| Curve feature | Reported property |
|---|---|
| Slope of the initial straight (Hooke) line | Young’s modulus |
| Upper and lower points where the material yields | Upper and lower yield strength |
| Maximum stress reached | Ultimate tensile strength; necking begins after the maximum force |
| Strain at maximum force | Uniform strain |
| Strain at fracture | Failure strain |
Common mistakes
- Treating E8 and E8M as interchangeable when the round-specimen gauge length differs (4D versus 5D).
- Using a metals standard for plastic or rubber specimens, or the reverse; pick the standard by material first.
- Reading dimensions from a summary page rather than the current edition of the standard; ASTM E8/E8M-25 is the active edition as checked on 2026-11-07.
- Skipping verification of the machine’s force system (ISO 7500-1 for the metals side).
Frequently asked questions
What is a tensile test?
A destructive test in which a specimen is stretched at a controlled rate until it fails, while force and elongation are recorded to calculate stress and strain (ZEISS).
What does a tensile test measure?
For metals under ASTM E8/E8M: yield strength, yield point elongation, tensile strength, elongation and reduction of area.
Which standard applies to a tensile test?
It depends on the material. See the table above: ASTM E8/E8M and ISO 6892-1 for metals, ASTM D638 for plastics, ASTM D412 for rubber.
What is the difference between a tensile tester and a tensile test machine?
The terms are used interchangeably for the same instrument: a frame with fixed and movable crossheads, grips, a force measuring system and an extensometer.
Sources
- ASTM International, E8/E8M-25 Standard Test Methods for Tension Testing of Metallic Materials, Active, last updated 2025-08-26; read 2026-11-07.
- ZEISS, Tensile test (manufacturer explainer); read 2026-11-07.
