Tensile Testing

What Is Tensile Testing?

Tensile testing, also known as mechanical testing or pull testing, is where a specimen is gripped at both ends and pulled at a controlled rate until it either yields or breaks. The machine records the force applied and the extension of the sample, producing a stress-strain curve that quantifies the material’s mechanical response.

Tensile testing is foundational to materials science and engineering, supporting quality control, product validation, research and development, and regulatory compliance across diverse industries.

Why Use Tensile Testing?

Tensile testing provides a standardized method to evaluate a material’s mechanical integrity, making it a key test for qualifying polymers, metals, composites, adhesives, and films. It measures tensile strength, elongation, and Young’s modulus, characterizes adhesives and composite laminates, assesses environmental or heat-aging effects, and verifies supplier material claims. This testing is widely applied across industries, including aerospace, automotive, semiconductor, electronics, medical devices, packaging, construction, and consumer products.

How Tensile Testing Works

A tensile test begins by mounting the sample in two grips of a universal testing machine (UTM), such as an Instron. The machine pulls the sample at a controlled rate until it fractures. During this process, force and displacement are recorded and converted into engineering stress and strain.

Depending on the material and the standard, extensometers or video strain measurement systems may be used to capture precise strain data. The resulting stress-strain curve provides key mechanical properties, including ultimate tensile strength (UTS), yield point, elongation at break, and modulus. For precise strain measurements, we use a non-contact Advanced Video Extensometer (Instron AVE 3).

Test conditions such as speed, grip type, gauge length, and temperature are carefully controlled and standardized (e.g., ASTM D638 for plastics, ASTM E8 for metals).

Key Differentiators

• Analytical Output: Stress-strain curves; ultimate tensile strength (UTS), yield strength, modulus of elasticity, elongation at break, energy to fracture, and flexural/compressive load response, tenacity.
• Detection Limits: Load resolution down to 1/1000th of load cell capacity (±0.5% of reading); Covalent carries 50 N, 500 N, and 5 kN load cells.
• Material Compatibility: Rigid and semi-rigid plastics, films, elastomers, adhesives, foams, composites, fibers, and low-strength metals.
• Force Range: Up to 5 kN (1,125 lbf); load cells with built-in overload protection.
• Strain Measurement: AVE 3 Video extensometer.
• Temperature Range: Ambient only (no integrated heating or cooling chamber).
• Grip Options:
  • Screw-action grips (general-purpose).
  • Pneumatic grips (250 N rated) for delicate films and thin substrates.
  • Precision specimen loader for accurate mounting of soft materials and fibers.
• Flexural and Compression Fixtures:
  • 150 mm compression platen for foam, rubber, or soft materials.
  • 3-point and 4-point bend fixtures for standardized flexural testing.
• Travel Range: 868 mm.
• Test Speed: 0.001 mm/min to 2540 mm/min.

Covalent Capabilities: Standard and custom tensile workflows with integrated report generation; multi-sample throughput; support for ASTM D638, D882, E8, D790, and ISO equivalents. Extensometer compliant with ASTM E83/ISO 9513 and ready to test ASTM/ISO standards.

Sample Requirements

• Physical Form: Dogbone-shaped specimens (plastics/metals), rectangular strips (films), discs, or other standardized shapes.
• Geometry: Prepared according to relevant standard (e.g., ASTM D638 Type I).
• Sample Size: Tensile specimens are generally 5 mm thick and ≤25 mm wide.
• Special Requirements: Fibers or delicate specimens should be provided in sufficient length (≥100 mm) for alignment and secure mounting.