Breaking Force Analysis Project: Testing Scope, Standards, Methods and Applications

Breaking force analysis is a core mechanical testing project that measures the maximum tensile load a material can withstand before fracture, providing critical data for product design, quality control and compliance certification. This article explains the scope of breaking force analysis projects, the applicable ISO, IEC, ASTM, EN, GB and JIS standards, the sample types and test items covered, laboratory test methods, and typical industrial applications. Whether you manufacture wires and cables, textiles, wire ropes, fasteners or polymer products, understanding breaking force testing helps ensure structural reliability and regulatory compliance.

Technical Overview

Breaking force, also referred to as ultimate tensile force or maximum force (Fm), is the highest tensile load sustained by a test specimen before it ruptures, typically expressed in newtons (N) or kilonewtons (kN). Breaking force analysis is a destructive mechanical test performed on a universal testing machine (UTM), in which a prepared specimen is gripped at both ends and stretched at a controlled rate until failure. The recorded force-extension curve yields not only the breaking force itself but also derived parameters such as tensile strength (Rm), elongation at break, and breaking tenacity, depending on the material class.

Breaking force analysis is distinguished from general tensile testing by its focus on the absolute load at rupture rather than stress alone. This makes it especially relevant for products whose fitness for purpose is defined by load capacity, such as stranded conductors, steel wire ropes, yarns, sewing threads, strapping, and fasteners. Testing is conducted in accordance with international and national standards, including ISO 6892-1 and ASTM E8/E8M for metallic materials, IEC 60228 and GB/T 4909.3 for conductor wires, ISO 2062, ASTM D2256 and GB/T 3916 for yarns, ISO 3108 and ASTM A931 for steel wire ropes, ISO 527 and ASTM D638 for plastics, and ISO 898-1 for fasteners. Accredited third-party laboratories routinely perform these tests for product certification, supplier qualification and failure investigation.

Testing Samples

Metal Wires and Stranded Conductors

Round and shaped wires of copper, copper alloys, aluminum, aluminum alloys, and galvanized steel are tested to verify drawing, annealing and stranding quality. Conductor wires for insulated power cables are evaluated against the requirements of IEC 60228 and its national equivalents, while overhead conductor wires such as hard-drawn aluminum and zinc-coated steel core wires are verified against ASTM B200-series and related material specifications.

Yarns, Threads and Textile Materials

Spun and filament yarns, sewing threads, industrial yarns and monofilaments are tested using single-end methods per ISO 2062, ASTM D2256 and GB/T 3916. Fabric strip and grab breaking force tests may also be performed under ISO 13934-1 and ASTM D5034/D5035 when the sample is a woven or nonwoven textile.

Steel Wire Ropes and Prestressing Strands

Wire ropes, elevator ropes, bridge cables and seven-wire prestressing strands are tested for actual breaking force per ISO 3108, ASTM A931, ASTM A416 and ISO 6934. For large-diameter ropes where full-scale testing is impractical, the sum of calculated breaking forces of individual wires is used as a reference value.

Plastic Films, Tapes and Strapping

Packaging strapping (steel and plastic), adhesive tapes, plastic films and geomembranes are tested for breaking force and elongation using methods such as ASTM D3950 for nonmetallic strapping, ASTM D882 for thin films, and ISO 527 for plastic specimens in general.

Rubber and Elastomeric Products

Vulcanized and thermoplastic rubber products, including seals, hoses and elastic cords, are evaluated for tensile strength and elongation at break under ISO 37 and ASTM D412 using dumbbell or ring specimens.

Fasteners and Hardware

Bolts, screws, studs, rivets and similar hardware are subjected to tensile and proof-load testing per ISO 898-1, ASTM F606 and related fastener standards to verify property classes such as 8.8 and 10.9.

Testing Items

Depending on the material and the applicable standard, a breaking force analysis project typically covers the following measurable items:

• Maximum breaking force (Fm), reported in N or kN
• Tensile strength (Rm), the breaking force divided by the original cross-sectional area, in MPa
• Elongation at break (A) and elongation at maximum force (Agt)
• Knot breaking force and knot strength ratio for fine wires and filaments
• Breaking tenacity in cN/tex for textile yarns
• Force at specified elongation and initial modulus (Young's modulus)
• 0.1% proof force and total extension at maximum force for prestressing strands
• Proof load and ultimate tensile load for fasteners
• Statistical evaluation of results, including mean value, standard deviation and coefficient of variation

Testing Methods

All breaking force tests are performed on calibrated universal testing machines equipped with precision load cells verified in accordance with ISO 7500-1 or ASTM E4. Extensometers, where used, are verified per ISO 9513 or ASTM E83. Specimen preparation follows the governing standard: metallic wire specimens are tested at a strain rate or crosshead speed defined by ISO 6892-1, ASTM E8/E8M, GB/T 228.1 or JIS Z 2241, while yarns are tested with a gauge length of 250 mm or 500 mm at a speed selected so that rupture occurs within the time window specified by ISO 2062 or ASTM D2256.

Gripping is adapted to the specimen type to avoid premature failure at the jaws. Wedge and pneumatic grips are used for metals and plastics, capstan or wrap-type grips for yarns and cords, and spool/mandrel fixtures for wire ropes. Non-contact video extensometry is often preferred for fine wires and filaments, since attached clip-on extensometers can damage delicate specimens. Textile samples are conditioned under ISO 139 or ASTM D1776 (typically 20 ± 2 °C and 65 ± 4% relative humidity) before testing, while plastics are conditioned under ISO 291. A minimum of five to ten valid specimens is normally tested per sample lot, and failure outside the gauge length may require the result to be discarded and the test repeated. Where required by the specification, tests can also be conducted at elevated or sub-zero temperatures in environmental chambers, for example per ISO 6892-2 for metallic materials at elevated temperature.

Applications

Breaking force analysis projects support quality control, certification and engineering decisions across a broad range of industries:

• Wire and cable manufacturing: verification of conductor tensile properties and elongation for compliance with IEC 60228, product type testing, and investigation of conductor breakage during installation
• Textile and apparel production: yarn tenacity grading, spin-process optimization, and incoming inspection of industrial and sewing threads
• Construction and infrastructure: acceptance testing of prestressing strand, bridge cable and stay-cable wire ropes against ASTM A416 and ISO 6934 requirements
• Lifting and rigging equipment: verification of wire rope breaking force for cranes, hoists and elevators
• Packaging and logistics: validation of steel and plastic strapping load capacity for unitized cargo
• Fastener and automotive supply chains: proof-load and tensile verification of bolts and threaded components per ISO 898-1 for property-class conformity
• Medical and specialty applications: tensile verification of surgical sutures, monofilaments and functional fibers

Test reports issued by ISO/IEC 17025-accredited third-party laboratories are widely accepted for supplier qualification, tender documentation, product certification schemes and regulatory submission in both domestic and export markets.

FAQ

What is the difference between breaking force and tensile strength?

Breaking force is the absolute maximum load at rupture, expressed in N or kN, and is independent of specimen dimensions in reporting. Tensile strength (Rm) is the breaking force normalized by the original cross-sectional area, expressed in MPa. Standards for load-defined products, such as wire ropes and yarns, emphasize breaking force, while material standards for metals and plastics emphasize tensile strength.

Which standard applies to breaking force testing of cable conductors?

Conductor wires in insulated cables are typically evaluated against IEC 60228 together with the tensile test method of GB/T 4909.3 or ISO 6892-1, depending on the market and specification invoked. Overhead conductors and their component wires are tested to the relevant ASTM material specifications.

How many specimens are needed for a breaking force test?

Most metallic and plastic standards require at least five valid specimens, while yarn testing under ISO 2062 and ASTM D2256 commonly uses ten specimens to improve statistical confidence. Results are reported as individual values together with the mean and coefficient of variation.

Can breaking force tests be performed at non-ambient temperatures?

Yes. Environmental chambers allow testing at elevated or sub-zero temperatures using methods such as ISO 6892-2 (elevated temperature) and ISO 6892-3 (low temperature). This is frequently required for materials used in outdoor, arctic or high-temperature service environments.

What should be considered when selecting a testing provider?

Choose an accredited third-party laboratory holding ISO/IEC 17025 accreditation covering the specific test methods and materials involved, with calibrated force verification traceable to national metrology institutes and documented experience in the relevant product standards.