What Is Compression Set Test?
The compression test is a test in which a compressive load is applied to the specimen while the compression stress–deformation relationship and the permanent deformation after the load is removed are measured.
Purpose of Compression Set Test
The purpose is to determine the behaviour under load and the recovery capacity of cushioning, insulation and sealing elements.
Which Products Is Compression Set Test Applied To?
- Foam and sponge materials
- Rubber gaskets and blocks
- Insulation boards
- Packaging filler materials
In Which Sectors Is Compression Set Test Used?
Standards Related to Compression Set Test
- ISO 604
- ISO 844
- ISO 3386-1
- ISO 815-1
Compression Set Test Conditions
- Deformation ratio
- Percentage compression determined per the standard (e.g. 25%, 50%)
- Loading speed
- Constant speed defined in the standard
- Environment
- 23 °C ± 2 °C and 50% ± 5 relative humidity
- Permanent deformation
- Holding at the temperature and duration defined for compression set
Equipment for Compression Set Test
- Universal testing machine
- pressure plates
- Compression-set fixture and oven
- Thickness gauge
Sample Requirements for Compression Set Test
- Specimen size is cut per the relevant standard
- Cut surfaces must be smooth and parallel
- Generally three specimens per set
- Thickness must be measured before the test
Duration of Compression Set Test
Measuring the compression curve is short. Measuring permanent deformation (compression set) requires holding for 22 or 72 hours per the standard.
Compression Set Test Procedure
- 1Specimen thickness is measured.
- 2Conditioning is completed.
- 3The specimen is placed between platens and compressed to the defined ratio.
- 4Stress–deformation data is recorded.
- 5If permanent deformation is required, the specimen is held compressed at the defined temperature and duration, then released and its thickness is remeasured.
Compression Set Test Acceptance Criteria
The acceptance criterion is given in the specification as a stress value at a specified deformation, or as the maximum permitted percentage of permanent deformation.
Evaluation of Results
The stress–deformation curve and the percentage of permanent deformation are evaluated together. High permanent deformation indicates a loss of sealing capability.
Compression Set Test Report
- Standard applied
- Specimen size and thickness
- Deformation ratio and rate
- Stress values and percentage of permanent deformation
- Holding temperature and duration
Accreditation
EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.
Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.
Scope and authorisationsRelated Regulations
- Gasket and insulation product specifications
Mekanik Testler — What Does This Testing Field Cover?
The section below describes the field that the Compression Set Test test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.
Mechanical testing measures how a material or a part behaves under force. The family ranges from static loading (tension, compression, bending) to time-dependent behaviour (fatigue, creep), and from hardness and wear to fracture toughness.
What these tests have in common is that the result is reported as a MATERIAL PROPERTY. Yield strength or hardness is not a conformity decision; it is numerical data against which the design and the product standard will compare. Mechanical test reports are therefore usually an input to an engineering decision rather than to a product approval — material selection, safety factor, life prediction.
The distinction between static and dynamic behaviour is the key to understanding the field. A part may appear entirely unstressed under a static load yet break under repeated loading; fatigue fracture occurs at stresses well below the yield strength and gives no warning. For rotating, vibrating or cyclically loaded parts, a tensile test alone is therefore not sufficient evidence.
Test conditions determine the result, and this is critical for the readability of the report: specimen geometry, loading rate, temperature, conditioning and the gripping arrangement. The same material gives different values under different conditions. In plastics the rate effect is very pronounced, in metals the temperature effect; in composites the specimen orientation changes the result entirely.
Hardness is the most misused measurement in the field. Because it is fast, close to non-destructive and inexpensive, it is often used in place of strength. Conversion tables from hardness to strength exist, but they are APPROXIMATE and depend on the material group; using them as the sole evidence in material acceptance is wrong.
The fracture mechanics side requires a specific competence. Fracture toughness and fatigue crack growth rate measurements make it possible to calculate how long a cracked structure will last; they are the basis of damage-tolerant design in fields such as pressure equipment, aircraft structures and pipelines.
Method groups in this field
Static tests
Tension, compression, bending, shear and torsion. Yield and tensile strength, elongation and modulus of elasticity are obtained.
Impact tests
Charpy and Izod notch impact; the brittle-to-ductile transition behaviour of the material is determined as a function of temperature.
Hardness
Brinell, Vickers, Rockwell, Shore and micro hardness. Valuable for surface treatment depth and local differences in strength.
Fatigue
Force- and strain-controlled axial fatigue, fatigue in bending; S-N curves and the endurance limit.
Creep and stress relaxation
Behaviour under long-term load at high temperature; decisive for boiler, turbine and pressure equipment materials.
Fracture mechanics
Plane-strain fracture toughness, the J integral, CTOD and fatigue crack growth rate.
Wear and friction
Taber and rotating drum abrasion, coefficient of friction measurements.
Commonly confused in this field
- Calculating strength from hardness is approximate; it cannot be used as the sole evidence in material acceptance.
- Adequate static strength does not demonstrate fatigue strength; a cyclically loaded part requires a separate test.
- If test rate and temperature are not reported, the result cannot be compared — especially for polymers and composites.
- A test specimen and the actual part may not give the same value; moulding orientation, weld lines and differences in surface treatment all have an effect.
- A strength value given for a composite without stating the specimen orientation is meaningless.
- ASTM and ISO counterparts measure the same quantity but use different specimen geometries; the results are not treated as directly equivalent.
Which decisions these results support
- Design verification and material selection
- Incoming material control and supplier approval
- Meeting the mechanical requirements of the product standard
- Failure analysis, life prediction and damage tolerance calculation
- Verifying heat treatment and surface treatment processes
Related Tests
Frequently Asked Questions About Compression Set Test
According to which standard is Compression Set Test made?
Compression Set Test is executed in scope ISO 604, ISO 844, ISO 3386-1 and ISO 815-1. The limit values and acceptance criteria to be applied are defined in the product standard; The version valid for your product is confirmed in writing at the offer stage.
Which products does Compression Set Test apply to?
Mainly applied to Foam and sponge materials, Rubber gaskets and blocks, Insulation boards and Packaging filler materials. Whether your product is included in the scope is determined by examining its technical specifications and intended use.
Under what conditions is Compression Set Test done?
The determining parameters are: Deformation ratio — Percentage compression determined per the standard (e.g. 25%, 50%), Loading speed — Constant speed defined in the standard and Environment — 23 °C ± 2 °C and 50% ± 5 relative humidity. The full terms are in the "Test Conditions" section on the page and vary depending on the product standard.
What kind of sample is needed for Compression Set Test?
Specimen size is cut per the relevant standard, Cut surfaces must be smooth and parallel and Generally three specimens per set. The number of samples is determined according to the product standard and the scope to be reported.
How long does Compression Set Test take?
Measuring the compression curve is short. Measuring permanent deformation (compression set) requires holding for 22 or 72 hours per the standard. This duration belongs to the experiment itself; sample preparation, queuing and reporting are also evaluated. A realistic schedule for your product is given in the offer.
What is the Compression Set Test result called "appropriate"?
The acceptance criterion is given in the specification as a stress value at a specified deformation, or as the maximum permitted percentage of permanent deformation.