Tension Testing

Tension testing, also called tensile testing, is a core mechanical test used to determine how a material behaves when subjected to a uniaxial tensile force. It measures properties such as strength, ductility and elasticity under controlled conditions. A steadily increasing pulling force is applied until the specimen fails, generating data including yield strength, ultimate tensile strength, elongation at break and modulus of elasticity.

During testing, the specimen is securely held in grips or fixtures and loaded along its longitudinal axis. Accurate alignment and firm clamping are essential to avoid slippage or uneven loading, which could compromise results. The choice of grip depends on the material type and behaviour, whether brittle, ductile, rigid or flexible.

Tension testing supports quality assurance, product development and regulatory compliance in many industries. In materials research, it provides precise characterisation of performance under stress, helping engineers to select or refine materials for specific applications.

For product designers, it confirms that components meet mechanical performance targets before production. In manufacturing quality control, it verifies that parts meet specification. In safety-critical industries such as aerospace, automotive and medical devices, documented tensile performance is often required for compliance. Repeatable, traceable results are essential for product validation and for meeting audit requirements.

Tensile strength testing

Tensile strength testing follows established international standards such as ISO 527 and ASTM D638 for plastics, ASTM D882 for thin films, ISO 37 for rubber and elastomers, and ISO 7500-1 for verifying machine accuracy.

Specimens are prepared in standard shapes, for example dog bone profiles for plastics, flat strips for metals or lengths of wire or cable. Once mounted in the grips, the specimen is aligned to prevent bending stresses. The test machine applies a controlled tensile load at a constant crosshead speed until fracture. Load and elongation are recorded throughout, enabling calculation of tensile strength, yield point, Young’s modulus and percentage elongation. Stress-strain curves provide a detailed view of performance.

Materials tested include plastics, metals, rubber, composites and thin films, with test parameters adapted for each. Typical forces range from a few newtons for delicate films to tens of kilonewtons for structural metals.

Adhesion and peel testing

Adhesion tests measure the bond strength between materials such as laminates, adhesives, films and tapes. Common methods include 90 degree and 180 degree peel tests, defined by standards such as ASTM D3330 and ISO 8510. In the 180 degree peel, the bonded material is peeled back fully against itself. In the 90 degree method, the peel angle is maintained at a right angle.

These tests are widely used in packaging, electronics and composites to confirm consistent bond performance. For example, in medical packaging they help ensure sterile seals remain intact until intended opening.

Test fixtures and grips

The reliability of results depends on correct grip and fixture selection. Pneumatic grips provide fast, consistent clamping pressure for high-throughput testing. Wedge or vice grips give secure holding for high-strength materials. Self-tightening grips adapt to changes in specimen thickness during testing, reducing slippage risk.

Selecting the correct load cell is equally important for accuracy. Crosshead speed must be set according to the relevant standard to ensure comparable results.

Key standards

• ISO 527 - Tensile testing of plastics, covering tensile strength, modulus and elongation
• ASTM D638 - Tensile testing of plastics for the US market
• ASTM D882 - Tensile properties of thin plastic sheeting and films
• ISO 37 - Tensile stress-strain properties of rubber and elastomers
• ISO 7500-1 - Verification of tensile testing machines for force measurement accuracy
• ASTM D3330 and ISO 8510 - Peel adhesion testing for bonded films and tapes

Sector-specific standards also exist for applications such as packaging seal strength or aerospace fastener pull testing.

Staying current with specifications

Standards are updated periodically to reflect new research, improved methods and industry requirements. Maintaining compliance is essential for credibility and audit readiness. Mecmesin systems can be supplied with up-to-date test methods pre-programmed, ensuring traceability, repeatability and consistent adherence to standards.

Precision and flexibility

Mecmesin offers a wide range of systems for tension testing, from the manually operated MultiTest-dV for low-volume or field testing to the fully automated OmniTest for high-precision laboratory work. Systems cover forces from 2 N for delicate films up to 50 kN for high-strength metals. VectorPro software enables real-time data capture, analysis and automatic reporting to standardised formats.

Custom fixtures and adaptability

Some applications require bespoke grips or fixtures to suit unique shapes or fragile materials. Mecmesin can design and manufacture custom solutions to enable accurate, repeatable testing for irregular specimens or complex geometries.

Standards integration and automation

Systems can be pre-configured with test methods aligned to ASTM, ISO or BS EN standards, ensuring operators run tests with the correct parameters every time. Batch testing sequences and automation options help improve throughput and minimise operator error.

Technical support and global reach

Mecmesin provides calibration, training and installation services to keep systems compliant and in peak condition. A global network of service centres and application engineers supports customers in diverse industries.

Manufacturing and product development

In engineering and manufacturing, tension testing verifies the performance of raw materials, components and finished products. Examples include tensile strength of fine copper wire in electronics, pull-out strength of fasteners in automotive assemblies and load capacity of aerospace-grade aluminium components.

Packaging and adhesives

Tension and peel testing confirm that seals, closures and bonded layers in packaging meet strength requirements. In the food and pharmaceutical sectors, this helps ensure packaging integrity for safety and shelf life.

Medical and pharmaceutical devices

Medical devices often require verification of bond strength and durability. Examples include tensile testing of catheter tubing, peel testing of adhesive wound dressings and strength measurement of implant components.

Tension testing is essential for verifying product quality, safety and compliance. Selecting the right method, following recognised standards and using precision equipment ensures reliable results. For advice on the most suitable system or to develop a custom test method, speak to a Mecmesin applications engineer.