Tension spring testing service

Tension Spring Testing Service for Global Mechanical Component Compliance

As an ISO/IEC 17025 accredited laboratory, we deliver a specialized tension spring testing service that verifies the load-deflection characteristics, initial tension, fatigue life, material integrity, dimensional accuracy, and corrosion resistance of extension springs used in automotive, aerospace, industrial machinery, and consumer products. Our tension spring testing service supports manufacturers and exporters who must demonstrate conformity to ASTM A125, DIN 2097, ISO 10243, and regional spring standards across the European Union, North America, the Middle East, and Asia. Every test is performed under our CNAS-accredited quality system, producing reports accepted by notified bodies, spring OEMs, and procurement teams worldwide.

Product Samples We Regularly Test in Our Tension Spring Testing Service

Helical extension springs with plain ends — for general mechanical assemblies, linkages, and return mechanisms
Tension springs with hooks, loops, and threaded inserts — for automotive, appliance, and industrial connection points
Constant-force and variable-rate extension springs — for counterbalance, tension compensation, and precision force applications
Stainless steel and corrosion-resistant tension springs — for marine, food processing, and chemical environments
High-temperature and alloy tension springs — for engine, exhaust, and aerospace applications requiring thermal stability
Miniature and micro tension springs — for medical devices, electronics, and precision instruments
Custom-wound and OEM-specific tension spring assemblies — with special end configurations, coatings, and packaging requirements

Mechanical and Load-Deflection Testing for Tension Springs

Spring rate and load-deflection characteristic per ASTM A125 and DIN 2097 — the tension spring is stretched between calibrated grips and the force at specified extensions is recorded to generate the load-deflection curve, verifying the spring rate and working loads meet the design specification.
Initial tension measurement per ASTM A125 — the force required to initiate extension of the tension spring is measured, confirming the coils are wound with the specified pre-load and that the spring does not extend under zero load.
Free length and working length verification per customer drawings — the unloaded length of the tension spring is measured, and the spring is stretched to the specified working lengths to verify the corresponding loads match the tolerance band.
Solid height and maximum safe extension testing per ISO 10243 — the tension spring is extended to its maximum safe deflection and the resulting stress and permanent set are measured to ensure the spring does not take a permanent deformation under the rated load.
Permanent set and load loss after extension cycling per ASTM A125 — the spring is repeatedly extended to a defined maximum and the residual elongation and change in spring rate are recorded to predict relaxation and performance drift over time.
Hysteresis and energy absorption measurement per internal protocols — the spring is loaded and unloaded and the area between the curves is calculated to quantify internal friction and the damping contribution of the tension spring.

Fatigue and Long-Term Durability Testing for Tension Springs

Cyclic fatigue testing per ASTM A125 and ISO 10243 — the tension spring is subjected to repeated extension-return cycles at defined amplitudes and frequencies, and the number of cycles to failure or the loss of spring force beyond a specified limit is recorded to generate the fatigue life data for the application.
Resonance and high-frequency fatigue testing per internal protocols — for tension springs used in high-speed machinery and automotive valve trains, the spring is tested at its natural frequency to predict service life under dynamic loading.
Relaxation and stress loss at elevated temperature per ISO 10243 and ASTM E328 — the spring is held at a defined extension and temperature and the decay of the spring force is monitored over time to quantify the long-term stress relaxation behavior.
Creep and permanent set under sustained tension per ASTM D2990 — the tension spring is held at a constant extension for an extended period and the residual elongation after unloading is measured to predict long-term dimensional stability.
Corrosion fatigue testing per customer and internal protocols — the spring is subjected to cyclic loading while exposed to a corrosive environment to evaluate the combined effect of corrosion and fatigue on the service life of the tension spring.

Material Verification and Metallurgical Testing for Tension Springs

Optical emission spectrometry for alloy grade confirmation per ASTM E415 and ISO 14284 — the chemical composition of the spring wire is analyzed to verify conformance to specified grades such as music wire, oil-tempered wire, 302, 304, 316 stainless steel, or alloy steels, preventing material substitution.
Vickers and Rockwell hardness testing per ISO 6507-1 and ASTM E18 — the hardness of the spring wire surface and core is measured to verify the correct temper and heat treatment condition for the specified spring performance.
Metallographic examination and grain size analysis per ASTM E112 — polished and etched cross-sections are examined to evaluate the wire microstructure, inclusion content, and surface condition that affect fatigue life and corrosion resistance.
Hydrogen embrittlement testing per ASTM F519 — for high-strength and electroplated tension springs, the susceptibility to hydrogen-induced delayed fracture is evaluated to guarantee structural reliability after plating and in corrosive service.
Positive material identification using handheld XRF — non-destructive verification directly on the spring wire confirms alloy type and prevents material mix-ups during production and shipping.

Dimensional and Geometrical Inspection for Tension Springs

Wire diameter, coil diameter, and free length measurement per ISO 2768 and customer drawings — laser micrometers and coordinate measuring machines verify the spring dimensions and tolerance class, ensuring correct fit in the mating assembly.
Coil spacing, body length, and end hook geometry inspection — the pitch and uniformity of the coils and the shape and position of the end hooks are checked against the design specification to ensure proper engagement and load application.
Straightness and concentricity verification per ISO 1101 — the tension spring is checked for bow, lateral curvature, and concentricity of the coils to prevent binding and uneven stress distribution.
Visual defect inspection under D65 illumination — systematic examination for surface defects, nicks, tool marks, and coating defects against agreed acceptance criteria and master reference samples.
Coating thickness and uniformity measurement per ISO 2178 and ASTM B487 — the thickness of zinc, nickel, or other protective coatings on the tension spring is measured to verify the specified corrosion protection.

Corrosion Resistance and Surface Protection Testing for Tension Springs

Neutral salt spray and cyclic corrosion testing per ISO 9227 and ASTM B117 — the tension spring with its protective coating is exposed to salt fog for defined durations to evaluate red rust, white corrosion, and coating degradation in marine and industrial environments.
Passivation verification for stainless steel springs per ASTM A967 — copper sulfate and ferroxyl spot tests confirm the passive layer is intact on the spring surface after manufacturing and cleaning.
Resistance to cleaning agents, fuels, and industrial chemicals per ISO 175 and ASTM D543 — the spring surface is exposed to representative fluids to verify no staining, softening, or loss of protective coating occurs during service and maintenance.
UV and xenon-arc accelerated weathering of coated springs per ASTM G155 — for springs used in exposed applications, the coating is tested for color fading, chalking, and adhesion loss after simulated outdoor exposure.
Low-temperature flexibility and cold impact resistance per ASTM D2137 — the tension spring is conditioned at sub-zero temperatures and tested to verify it remains ductile and does not crack in cold climates.

Report Recognition and ISO/IEC 17025 Compliance

All test methods described in this tension spring testing service are covered by our ISO/IEC 17025 scope of accreditation. Our technical reports and certificates of analysis are accepted by European notified bodies for mechanical components, by North American automotive and industrial OEMs referencing ASTM and ISO standards, and by customs and procurement authorities across the Middle East, Australia, and Asia. Whether you require a complete qualification dossier for a new tension spring design, a batch release inspection for an export shipment, or a root cause failure analysis of a spring failure, our laboratory provides the measurement accuracy and spring engineering expertise that the global mechanical components industry demands.