Determination of Tensile Hysteresis Loss in Rubber: Principles, Standards, and Testing Methods

Tensile hysteresis loss determination quantifies the energy that a rubber material dissipates as heat when it is stretched and retracted in a controlled loading cycle, offering direct insight into damping capacity, heat build-up, and long-term fatigue behavior. This test is widely applied to vulcanized rubber and thermoplastic elastomer compounds used in tires, anti-vibration mounts, seals, belts, and dampers. This article explains the measurement principle, applicable standards such as ISO 37, ASTM D412, and GB/T 528, specimen requirements, calculation methods, and typical industrial applications.

Technical Overview

Rubber is a viscoelastic material, which means its mechanical response combines elastic energy storage with viscous energy dissipation. When a rubber specimen is stretched to a given elongation and then allowed to retract, the retraction curve does not retrace the extension curve. The enclosed area between the two curves is known as the hysteresis loop, and the energy it represents is the tensile hysteresis loss — the portion of input mechanical energy that is converted into heat rather than being elastically recovered.

Tensile hysteresis loss is typically expressed either as absolute energy (joules or millijoules per cycle, sometimes normalized to specimen volume in MJ/m³) or as a percentage of the total input energy. A higher percentage indicates a more highly damping compound with greater heat generation, while a lower percentage indicates better elastic recovery and lower heat build-up. Neither direction is universally "better": high hysteresis is desirable in damping and shock-absorbing applications, whereas low hysteresis is preferred in rolling tires and dynamic springs where heat accumulation must be minimized.

During the first loading cycle, rubber also exhibits stress softening, commonly known as the Mullins effect, which causes an unusually large first-cycle hysteresis loop. For this reason, test protocols clearly define whether the first cycle or a subsequently stabilized cycle is used for reporting. Accurate determination of tensile hysteresis loss is essential for compound development, quality control, and failure analysis, and it should be performed by accredited third-party laboratories using calibrated universal testing machines.

Testing Samples

Vulcanized Rubber Dumbbell Specimens

The most common test pieces are dumbbell-shaped specimens cut from vulcanized rubber sheets using standard cutting dies, such as Type 1 and Type 2 dumbbells defined in ISO 37 and GB/T 528, or Die C specimens in ASTM D412. Specimen thickness is typically 2 mm, and the narrow parallel section defines the gauge length over which strain is measured.

Thermoplastic Elastomers (TPE, TPV, TPU)

Injection-molded or compression-molded thermoplastic elastomer plaques can be tested using the same dumbbell geometry. Because thermoplastic elastomers show stronger rate and temperature sensitivity, hysteresis comparisons between TPE grades must always state the strain level and cycle speed used.

Ring Specimens

Small ring test pieces, standardized in ISO 37 and ASTM D412, are suitable for materials with low elongation capacity or when flat sheet cutting is impractical, such as O-ring stock or cable insulation compounds.

Cut Specimens from Finished Products

Dumbbells or strips can frequently be harvested from finished goods — tire treads and sidewalls, conveyor belt covers, hose tubes, sealing profiles, footwear midsoles, and rubber fabrics — to evaluate the hysteresis behavior of the actual manufactured article rather than a laboratory compound.

Fabric-Reinforced and Coated Fabrics

Strip specimens of rubberized or coated textiles may be evaluated in cyclic tension to characterize energy loss and heat generation in products such as diaphragms, inflatable structures, and flexible membranes.

Testing Items

A typical tensile hysteresis loss determination report includes the following measured and calculated quantities:

• Tensile input energy — the area under the extension (loading) curve up to the specified elongation
• Recovered energy — the area under the retraction (unloading) curve
• Tensile hysteresis loss — the difference between input energy and recovered energy per cycle
• Percentage hysteresis loss — hysteresis loss divided by input energy, multiplied by 100
• Hysteresis loop shape and area at multiple strain levels (for example 50%, 100%, 200%, and 300% elongation)
• Cycle-to-cycle softening (Mullins effect) and energy loss stabilization over repeated cycles
• Supporting tensile properties: tensile strength, elongation at break, stress at 100%/200%/300% elongation, and tension set after cycling
• Specimen temperature rise observations where instrumented, as an indicator of heat build-up tendency

Testing Methods

Determination of tensile hysteresis loss is performed on a calibrated universal testing machine (tensile tester) equipped with a cyclic loading capability, an appropriate load cell matched to the expected forces, and either a non-contact video extensometer or a compliant contact extensometer for accurate strain measurement. The general procedure is as follows:

• Specimen preparation: dumbbells are cut with a sharp die, marked with benchmark lines, and their width and thickness are measured at several points to determine the cross-sectional area.
• Conditioning: specimens are conditioned in the standard laboratory atmosphere of 23 °C ± 2 °C and 50% ± 5% relative humidity in accordance with ISO 23529 (GB/T 2941) for the specified period, and vulcanized articles are allowed the full maturation interval after curing.
• Gripping and pre-load: the specimen is clamped in pneumatic or mechanical grips with a small pre-load applied to remove slack without inducing strain.
• Cyclic loading: the specimen is extended at a constant crosshead speed — commonly 500 mm/min as used in ISO 37 / GB/T 528 tension testing — to the specified elongation, held momentarily or retracted immediately, and returned to the initial gauge length at the same rate.
• Data acquisition: force–extension data are recorded continuously throughout extension and retraction, tracing the hysteresis loop.
• Calculation: input energy W1 is obtained by integrating the extension curve, recovered energy W2 by integrating the retraction curve, and hysteresis loss = W1 − W2, with percentage hysteresis = (W1 − W2)/W1 × 100.
• Multi-cycle protocols: where stabilization matters, the specimen is cycled repeatedly (for example 3 to 10 cycles, or more) and the hysteresis loss of the final stabilized cycle, or the decay curve across all cycles, is reported.

Primary reference methods and standards include ASTM D412 (Standard Test Methods for Vulcanized Rubber and Thermoplastic Elastomers—Tension), ISO 37 and GB/T 528 (tensile stress–strain properties), which govern specimen geometry and tension testing practice, and ASTM D5992 together with ISO 4664, which provide guidance on the dynamic and hysteretic characterization of rubber materials. Results must always be reported together with the strain amplitude, strain rate, cycle count, temperature, and whether the first or a stabilized cycle was evaluated, because all of these parameters strongly influence hysteresis loss. Dynamic mechanical analysis (DMA) in tension mode can supplement the method by resolving the storage and loss components of the same dissipated energy as a function of frequency and temperature.

Applications

Tensile hysteresis loss data directly support engineering decisions across many rubber product sectors:

• Tire engineering: balancing rolling resistance, wet grip, and wear — trade-offs fundamentally governed by compound hysteresis at different strain amplitudes and temperatures
• Anti-vibration components: engine mounts, suspension bushings, and cab mounts, where controlled hysteresis provides vibration damping and isolates structure-borne noise
• Seals and gaskets: predicting heat generation in cyclic service and residual sealing force after repeated deformation
• Conveyor belts and power transmission belts: assessing heat build-up and flex fatigue resistance of cover and skim compounds
• Footwear midsoles and sports surfaces: tuning energy return versus shock absorption for performance and comfort
• Dampers, couplings, and seismic isolation bearings: validating energy dissipation capacity required by structural design codes
• Compound development and quality control: comparing filler systems, plasticizer levels, cure states, and recycled content on a quantitative energy basis
• Failure analysis: identifying over-heating, aging, or insufficient crosslink density as root causes of service failure

FAQ

What is tensile hysteresis loss in rubber?

It is the mechanical energy dissipated as heat when a rubber specimen is stretched and then retracted. Graphically, it equals the area enclosed between the extension and retraction curves of the force–extension diagram, and it is reported either in energy units or as a percentage of the input energy.

How is percentage hysteresis loss calculated?

Percentage hysteresis loss = (W1 − W2) / W1 × 100, where W1 is the input energy represented by the area under the extension curve and W2 is the recovered energy represented by the area under the retraction curve.

Which standards apply to this test?

Specimen geometry and tension test practice are governed by ASTM D412, ISO 37, and GB/T 528; conditioning requirements come from ISO 23529 (GB/T 2941); and dynamic/hysteretic characterization guidance is provided by ASTM D5992 and ISO 4664. Accredited third-party laboratories combine these frameworks into a documented hysteresis test protocol.

Why is the first loading cycle usually not used for reporting?

The first cycle includes stress softening (the Mullins effect), which produces an artificially large hysteresis loop that is not representative of steady-state service. Most protocols either report the first cycle explicitly for scientific purposes or precondition the specimen and report a stabilized cycle.

What test variables most influence the result?

Strain amplitude, strain rate (crosshead speed), temperature, cycle count, compound formulation (filler type and loading, plasticizer content), and cure state all significantly affect hysteresis loss, so they must be fixed and clearly stated in any comparison.

Is high hysteresis loss good or bad?

It depends on the application. High hysteresis is beneficial where vibration damping and impact energy absorption are required, such as mounts and dampers. Low hysteresis is preferred where heat build-up must be minimized, such as low-rolling-resistance tire treads and dynamic springs.