A2LA Accredited ISO/IEC 17025:2017 Nadcap Accredited - Materials Testing Laboratories, Non Metallic Materials Testing

Stress Relaxation Testing Lab

For stress relaxation characterization supporting specification, material qualification, product development, and force-retention evaluation.
Start with a short consult to align the method, specimen requirements, and deliverables to your objectives.
Elastomers RubbersTPEsViscoelastic PolymersSealing Force-Retention Materials
Short-Term Tensile/Compressive: ASTM D6048DPL M-624DPL M-625
Long-Term Instrumented Compression: ASTM D6147
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Options
  • Short-term tensile, compressive, and stepwise relaxation programs
  • Long-term instrumented compressive relaxation programs
  • Method-appropriate specimen geometry, fixtures, strain levels, and load measurement
  • Temperature-conditioned or comparative force-retention programs
Deliverables
  • Engineering test report (PDF) with digital data delivery
  • Method-appropriate outputs such as stress-relaxation curves, residual stress, stress-retention values, relaxation rate, and long-term force decay
  • Raw data exports available on request, where applicable
  • Exact deliverables depend on the selected stress-relaxation mode, duration, and specimen configuration
A2LA Accredited ISO/IEC 17025:2017 Nadcap Accredited - Materials Testing Laboratories, Non Metallic Materials Testing
1
Share your requirements

Tell us about the material, application, environment, and any method, standard, specimen, or conditioning constraints.

2
Confirm the approach

We’ll align the appropriate method, specimen requirements, and deliverables to your objectives, then provide a quote and test plan.

3
Submit your PO and materials

Send the purchase order and arrange delivery of materials or specimens so the program can move into scheduling and execution.

4
Receive your results

You’ll receive an engineering test report with digital data delivery, along with any agreed raw data or method-appropriate outputs.

Typical turnaround for most testing is five business days. Longer-duration programs may require more time.

Ready to proceed? Contact us

FAQs

It depends on the stress relaxation method, material form, and program design. Share what you have and we’ll confirm specimen geometry, minimum specimen count, and whether tensile or compressive fixtures are more appropriate.

Measurement approach depends on method. Short-term stepwise or tensile/compressive programs may use load-cell force tracking, while longer instrumented programs monitor force decay over extended hold times.

We support common ASTM and DatapointLabs stress relaxation methods across short-term and long-term elastomer-focused programs and can confirm the right path during the initial consult.

Yes—where applicable, we support short-duration tensile or compressive relaxation work and longer-term instrumented force-retention programs depending on material and objective.

You receive an engineering test report (PDF) and digital data deliverables. Raw data exports are available on request where applicable. Exact outputs depend on the specific stress relaxation test ordered.

Reported outputs depend on the test and measurement approach. Common outputs include stress-relaxation curves, residual stress, stress-retention values, relaxation rate, and longer-term force-decay behavior.

Typical turnaround for most testing is five business days, but timing can vary based on run duration, conditioning, fixture setup, and test volume—share constraints and we’ll propose a viable plan.

Tell us what you need back—force-decay data, retention values, curves, raw data, and any required method/standard. We’ll align the program and deliverables before testing begins.

Technical Guide

The sections below provide the technical context, standards, specimen considerations, test procedures, and measurement details for this testing service.

Significance & Purpose

Stress Relaxation Testing evaluates how a material’s internal stress decreases over time under constant strain. This is particularly important for elastomers used in seals, gaskets, and other applications where long-term force retention is crucial. Unlike creep testing (where strain increases under constant stress), stress relaxation testing measures the loss of stress at a fixed deformation. The results help in predicting the long-term sealing performance, viscoelastic behavior, and material stability under mechanical loads.

Short-Term Stress Relaxation

  • Tensile Stress Relaxation:
    • DPL M-624: Stepwise tensile stress relaxation for elastomers (internal DatapointLabs standard)
    • ASTM D6048: Standard test for tensile stress relaxation over short durations (≤4 hours)
  • Compressive Stress Relaxation:
    • DPL M-625: Stepwise compressive stress relaxation for elastomers (internal DatapointLabs standard)

Long-Term Stress Relaxation (Extended Duration, Instrumented Testing)

  • Compressive Stress Relaxation (Long-Term, Instrumented Test):
    • ASTM D6147: Standard test method for evaluating long-term stress relaxation of elastomeric materials using instrumented setups

DatapointLabs Tests for Stress Relaxation Testing

Tests in the DatapointLabs test catalog that reference stress relaxation testing are as follows:

Stress Relaxation Testing Specific to Elastomers

Test ID Test Description Standards
M-624 Stepwise Tensile Stress Relaxation DPL M-624*
M-625 Stepwise Compressive Stress Relaxation DPL M-625*
M-626 Tensile Stress Relaxation (up to 4 hours hold time) ASTM D6048
M-266 Long Term Instrumented Stress Relaxation ASTM D6147

* Internal DatapointLabs Standard

Principle of Operation

Stress relaxation testing involves:

  1. Applying a constant or stepwise strain: Either tensile or compressive, to a test specimen.
  2. Measuring the decrease in stress over time: As molecular rearrangements within the material lead to force decay.
  3. Recording data for a set duration: Whether short-term or long-term, depending on the test standard.

In elastomers, stress relaxation occurs due to viscoelastic behavior, molecular disentanglement, and potential environmental effects (e.g., temperature, humidity).

Typical Procedure

  1. Sample Preparation
    • Test specimens are machined or molded according to standard dimensions.
    • Conditioning is done per test requirements (e.g., temperature stabilization).
  2. Test Setup
    • The specimen is placed in a tensile or compression fixture.
    • Strain is applied to a predefined level (e.g., 10%, 20%, or 50% elongation in tensile tests).
  3. Relaxation Phase
    • The applied strain is held constant or in a stepwise manner.
    • The decrease in force (stress) is recorded over time using load cells or other sensors.
  4. Data Recording and Analysis
    • Short-term tests (ASTM D6048, DPL M-624/M-625) may last minutes to hours.
    • Long-term tests (ASTM D6147) can last for up to 1000 hours under controlled conditions.

Specimen Types

Specimens used by DatapointLabs in various types of stress relaxation testing are as follows:

Specimen Type DatapointLabs Test IDs
Tensile Bars [Details] M-626
Prisms [Details] M-266
Contact Us [Details] M-624, M-625

Extensometry Techniques

Extensometry techniques typically employed by DatapointLabs in stress relaxation testing are as follows:

Extensometry Technique DatapointLabs Test IDs
Crosshead Displacement (Axial) M-624, M-625, M-626, M-266

Characterization Measurements

Stress Relaxation Curve

  • A stress relaxation curve plots stress vs. time at a constant strain.
  • The curve typically exhibits a rapid initial stress drop, followed by a gradual decline as the material stabilizes.
  • Key parameters that may be extracted from the curve include:
    • Initial stress (σ0) at the start of relaxation.
    • Residual stress (σt) after a defined time.
    • Stress retention percentage (σt/σ0×100%) after a given duration.
    • Relaxation rate (slope of stress decay over time).

Typical Data Reported (see test descriptions for exact details)

  • Stress Relaxation Curve: Plot of stress vs. time at constant strain.
  • Percentage of Stress Relaxation Over a Given Duration: Derived from stress relaxation curve.
  • Stress Retention at Various Time Points: Derived from stress relaxation curve.
  • Effect of Temperature on Stress Relaxation: Probing temperature dependency of stress vs. time at non-ambient temperatures.

 Suitable Material Types

  • Elastomers (Rubber Materials): Natural rubber, silicone rubber, EPDM, nitrile rubber, polyurethane elastomers.
  • Thermoplastic Elastomers (TPEs): TPU, TPO, SEBS-based elastomers.

Suitable Applications

  • Seals & Gaskets: Predicting long-term sealing effectiveness in automotive, aerospace, and industrial applications.
  • O-Rings & Rubber Components: Evaluating stress decay in dynamic or static sealing environments.
  • Medical Devices: Assessing force retention in soft elastomeric components such as tubing and stoppers.
  • Vibration Dampers & Shock Absorbers: Understanding viscoelastic stress relaxation properties for performance over time.
  • Electrical Insulation Components: Evaluating force decay in elastomeric parts used in cable and electronic housings.

Conclusion

Stress relaxation testing is essential for assessing the time-dependent mechanical stability of elastomers and other viscoelastic materials. Standards such as ASTM D6048, ASTM D6147, and DPL M-624/M-625 provide structured methodologies for evaluating stress decay under tensile and compressive conditions. The results guide material selection, performance prediction, and long-term design optimization in sealing, vibration damping, and soft polymer applications.

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