Testing Information
ZHONGXI Testing provides tensile strength test services for metallic materials, polymers, textiles, composites, wires and cables, fasteners, rubber products, and construction materials, covering the determination of tensile strength, yield strength, elongation at break, and related mechanical parameters. Tensile strength testing is applied across aerospace components, automotive structural parts, steel structures, pipeline manufacturing, plastic injection molding, packaging films, geotextiles, medical sutures, and welded joints, wherever a product's load-bearing capacity under axial tension must be verified before it enters service.
The purpose of tensile strength testing is to quantify the maximum engineering stress a material or component can withstand before fracture, to confirm compliance with product specifications and contractual requirements, and to reveal processing defects such as under-curing in adhesives, inadequate heat treatment in steels, poor fiber-matrix bonding in composites, or weak seam construction in geosynthetics. The core technique is uniaxial loading on a universal testing machine equipped with calibrated load cells and extensometers, in which a specimen of defined geometry is gripped at both ends and pulled at a controlled strain rate or stress rate until rupture. During loading, the force-displacement curve is recorded continuously and converted into a stress-strain curve, from which the upper and lower yield points, 0.2% proof strength, tensile strength, uniform elongation, total elongation at break, and reduction of area are derived. For elastomers, additional indices such as tensile stress at a given elongation (for example, 300%) and tear propagation behavior may be measured in the same setup.
A typical tensile strength test workflow at ZHONGXI Testing proceeds as follows., the sample is conditioned in a temperature- and humidity-controlled laboratory, typically 23 ± 2 °C and 50 ± 10% relative humidity for plastics, rubbers, and textiles, so that viscoelastic materials reach a stable moisture and thermal state. Second, the specimen is prepared according to the applicable geometry — flat dog-bone coupons for sheet metals and plastics, machined round bars with threaded or shouldered ends for castings and forgings, dumbbell specimens stamped or die-cut from rubber sheets, yarn grips with capstan or pneumatic clamps for fibers, and full-section samples for wire, rope, and strand products. Third, the gauge length, width, and thickness are measured at multiple positions with micrometers or optical gauges, because the cross-sectional area enters directly into the stress calculation and a 1% area error produces a 1% strength bias. Fourth, suitable grips are selected — wedge grips for rigid metals, pneumatic side-action grips for polymers that clamp at constant pressure, hydraulic grips for high-force specimens above 300 kN, and bollard grips for ropes — together with a contact extensometer, video extensometer, or averaged crosshead displacement, depending on the modulus and elongation range. Fifth, the test is run at the standard-specified speed, for instance 1–10 mm/min for metals in the elastic region, 50–500 mm/min for rubbers, and strain-rate-controlled loading for rate-sensitive steels, until specimen fracture. Sixth, fracture location, break type, and anomalies such as slip at grips or failure outside the gauge length are recorded, invalid tests are repeated, and the results are statistically summarized with mean, standard deviation, and coefficient of variation.
Core parameters reported in a tensile strength test include tensile strength (Rm or σb, in MPa), yield strength (ReH, ReL, or Rp0.2), fracture elongation (A or εb, in %), reduction of area (Z, for ductile metals), tensile modulus (Young's modulus E in the elastic segment), stress at specified elongation for elastomers, breaking force in N or kN for textiles and ropes, and knot-breaking strength for fishing lines and surgical sutures. Interpretation considers not only whether the mean value meets the specification limit but also the scatter, the fracture morphology examined under stereo microscopy, and whether the failure mode (ductile cup-cone, brittle cleavage, delamination, adhesive failure at a joint) matches the expected behavior of the material class.
Testing Scope
- Carbon structural steel plates and sections, including Q235B, Q345B (S355), Q390, Q420, and Q460 grades, for building and bridge fabrication acceptance.
- Low-alloy high-strength steels such as Q690, WH60, and B610CF boiler and pressure vessel steels, tested in delivery and simulated post-weld heat treatment conditions.
- Stainless steel sheets, bars, and tubes covering AISI 304, 304L, 316, 316L, 321, 347, duplex 2205, and 2507 super duplex for chemical and marine equipment.
- Spring steels including 65Mn, 60Si2Mn, 55CrSi, and SUP series wires, evaluated for high-yield and fatigue-adjacent tensile behavior.
- Cold-rolled and hot-rolled low-carbon steel sheets for automotive panels, including interstitial-free, bake-hardening, dual-phase DP590/DP980, and TRIP steels.
- Aluminum alloys in plate, extrusion, and forged forms, such as 1060, 3003, 5052, 5083, 6061-T6, 6063-T5, 7075-T6, and 2024-T351 for aerospace and rail transit.
- Copper and copper alloys including T2 pure copper, H62 and H65 brass, QSn6.5-0.1 phosphor bronze, and B10/B30 cupronickel tubes for heat exchangers.
- Titanium alloys such as TA1, TA2, TC4 (Ti-6Al-4V), and TC11 in bar, plate, and additive-manufactured forms for medical implants and aero-engine parts.
- Nickel-based alloys including Inconel 625, Inconel 718, Monel 400, and Hastelloy C-276 for high-temperature and corrosive-service components.
- Gray and ductile cast irons, including HT200, HT250, QT400-18, QT500-7, and QT700-2, with separately cast test bars or attached test blocks.
- Steel wires and wire ropes, including galvanized bridge strand, prestressing concrete steel wire and strand (1770 MPa and 1860 MPa classes), and tire-cord wire.
- Welded joints and weld metal cross-sections, butt joints, fillet welds, and dissimilar-metal joints from arc, laser, friction stir, and electron beam welding processes.
- Fasteners including hex bolts of property classes 4.8, 8.8, 10.9, and 12.9, nuts, studs, washers, and high-strength structural bolt assemblies subject to axial tension testing.
- Engineering plastics including PA6, PA66, POM, PTFE, PEEK, PC, POM-C, PE-UHMW, and glass-fiber-reinforced grades in injection-molded and machined forms.
- Plastic films and sheets, including PE, PP, PET, BOPP, CPP, PVDC-coated laminates, and multilayer barrier films for food and pharmaceutical packaging.
- Pipe materials including PE80 and PE100 polyethylene pipes, PVC-U and PVC-M pressure pipes, PP-R hot-water pipes, and butt-fusion and electrofusion joints.
- Geosynthetics including woven and nonwoven geotextiles, geogrids of PET, PP, and steel-polymer composite types, and geomembranes for landfill and hydraulic works.
- Rubber and elastomeric products including NR, SBR, NBR, EPDM, CR, silicone VMQ, and FKM compounds in vulcanized sheets, O-rings, conveyor belts, and hoses.
- Textile materials including cotton, polyester, and blended yarns, industrial filament yarns such as high-tenacity PET and nylon 6,6, webbings, and safety-belt components.
- High-performance fibers and their composites, including aramid (para-aramid Kevlar-type and meta-aramid), UHMWPE, carbon fiber tows and impregnated strand, and basalt fiber.
- Adhesives and sealants in bulk, lap-shear (single-lap and double-lap), and butt-joint tensile configurations for structural bonding evaluation.
- Coated fabrics and tarpaulins, including PVC-coated polyester architectural membranes, PTFE glass-fiber membranes, and polyurethane-coated textiles.
- Medical devices with tensile-sensitive functions, including absorbable sutures, non-absorbable sutures, surgical meshes, catheter bond points, and balloon catheters.
- Electrical conductors including bare aluminum stranded conductor (AAC), aluminum conductor steel-reinforced (ACSR) cables, and copper busbar strips.
- Rebar and prestressing materials for concrete, including HRB400, HRB500, HRB400E seismic-grade rebar, and cold-rolled ribbed bars.
Testing Items
- tensile strength (Rm) — the maximum engineering stress sustained before fracture, the primary acceptance criterion for most metallic and polymeric products.
- Upper yield strength (ReH) — the stress at the onset of plastic yielding, used to confirm that low-carbon steels meet the specified minimum yield for structural design.
- Lower yield strength (ReL) — the lowest stress in the yield plateau, relevant for materials showing discontinuous yielding such as rimmed and killed carbon steels.
- 0.2% proof strength (Rp0.2) — the offset yield used for materials without a distinct yield point, including most aluminum alloys, austenitic stainless steels, and titanium.
- Fracture elongation (A) — the percentage plastic extension at break, indicating ductility reserve and formability; low values flag embrittlement from improper heat treatment or contamination.
- Reduction of area (Z) — the decrease in cross-sectional area at the fracture plane, a sensitive ductility index for forged and cast steels with internal defect populations.
- Young's modulus (E) — the elastic stiffness derived from the initial linear segment using a bonded or video extensometer, essential input for deflection and buckling calculations.
- Tensile stress at specified elongation (for example stress at, 200%, 300%) — a control index for vulcanized rubber compounds indicating stiffness development in the compound.
- Breaking force and breaking tenacity — reported in N and cN/tex for yarns and industrial fibers, tenacity allowing comparison across different linear densities.
- Elongation at specified force — the extension reached at a defined preload or working load, used for ropes, webbings, and geotextiles in service-simulation contexts.
- Knot-breaking strength — the retained strength of yarns and fishing lines after knotting, exposing brittleness and friction-related strength loss.
- Seam strength and joint efficiency — the tensile strength of sewn, welded, or bonded seams expressed as a percentage of the parent fabric strength for geotextiles and filter fabrics.
- Lap-shear strength of adhesives — the average shear stress at failure of a single-lap joint, the standard comparative index for structural adhesive selection and process control.
- Bond strength of coatings — tensile adhesion measured with dollies for thermal spray coatings, paints, and waterproof membranes, revealing interfacial weakness.
- Poisson's ratio — measured with biaxial or transverse extensometry, needed for finite-element material models of plastics and metals.
- Strain-hardening exponent (n-value) and plastic strain ratio (r-value) — formability indices for sheet metals determined in tensile tests at multiple orientations to the rolling direction.
- Breaking strength retention after aging — tensile strength measured after thermal, UV, or chemical exposure and compared with unaged values to quantify degradation.
- Weld joint strength and fracture location — the transverse tensile strength of butt welds plus classification of failure in parent metal, weld metal, or heat-affected zone.
- Tear strength — trouser, angle, and crescent tear methods for rubber and coated fabrics that measure resistance to propagation of an initiated cut.
- Creep-adjacent tensile indices — sustained-load tensile behavior of PE pipes and geosynthetics evaluated with elevated-temperature tensile testing to project long-term hydrostatic strength.
- Full-section breaking load — the actual force to break a wire rope, strand, chain, or webbing sling as an assembled product rather than a material coupon.
- Anisotropy mapping — tensile strength measured at 0°, 45°, and 90° to machine direction for rolled sheet, extruded profiles, and unidirectional composites, quantifying directional dependence.
FAQ
What is the turnaround for a tensile strength test?
The standard turnaround is 7 to 15 working days from sample receipt, depending on the number of test items, specimen type, and whether conditioning or aging pre-treatment is required. Straightforward room-temperature tensile tests on machined metal coupons or die-cut polymer dumbbells are typically completed in 7 to 8 working days; tests requiring special fixture manufacture, elongated conditioning at 23 °C/50% RH, weld cross-sectioning, or post-aging comparisons can extend toward 12 to 15 working days. Expedited schedules can be discussed with the project engineer when the sample arrives.
How much does tensile strength testing cost?
Cost is determined mainly by the number of testing items selected — for example, tensile strength alone versus a full package of Rm, ReL, A, Z, and modulus — and secondarily by specimen preparation needs such as machining, die-cutting, or grip fabrication. Additional factors include specimen count per condition, environmental chamber time, and whether aged-versus-unaged comparison sets are needed. A specific quotation based on the submitted product type and applicable standard is available from the testing engineers after reviewing the sample and requirement list.
Which items does a tensile strength test include, and how much sample should be prepared?
The included items depend on the product type and applicable standard: metals typically cover Rm, ReH/ReL or Rp0.2, elongation A, and reduction of area Z; plastics add tensile modulus and strain at break; rubbers report stress at /300% elongation and elongation at break; yarns and geosynthetics report breaking force and tenacity with elongation at that force. As a general guide, 100–500 g of material is sufficient for polymer, rubber, and textile testing, while metal testing usually requires enough stock to machine at least 3 to 5 coupons — for flat specimens roughly a 300 mm × 50 mm strip at full thickness, or a 300 mm length of bar stock. Test engineers confirm the exact sampling plan before the order begins.
Why can tensile results differ between laboratories even for the same material?
Differences usually originate from four controllable sources: specimen geometry and gauge length (shorter gauge lengths concentrate necking strain and inflate elongation values), testing speed or strain rate (polymers and rate-sensitive steels show measurably higher strength at higher rates), grip type and clamping pressure (slip or premature fracture at the jaws lowers measured strength and forces retests), and cross-section measurement uncertainty. ZHONGXI Testing controls these variables by using standardized specimen geometries, rate-controlled loading per the applicable method, matched grip selection, and multi-point dimensional measurement, and it repeats any test in which fracture occurs within the grip region or at a marked anomaly so the reported value reflects true gauge-length behavior.
Summary
Tensile strength testing at ZHONGXI Testing covers tensile strength, yield and proof strength, elongation, reduction of area, modulus, breaking force, tear strength, joint and seam strength, and retention after aging, for metals, plastics, rubbers, textiles, composites, adhesives, fasteners, wires, and geosynthetics. Testing is performed with universal testing machines from millinewton to 2000 kN capacity, contact and video extensometry, and environmental chambers from −70 °C to +350 °C, with typical turnaround of 7 to 15 working days depending on the item list and sample condition.