Overview
SIST ISO 7148-2:2015 - Plain bearings: Testing of the tribological behaviour of bearing materials - Part 2: Testing of polymer-based bearing materials - defines standardized tribological test methods to assess the friction and wear behaviour of polymer-based plain bearing materials under specified working conditions (load, sliding velocity, temperature), both with and without lubrication. The standard produces reproducible data for comparing metal–polymer and polymer–polymer rubbing pairs and emphasizes that test results are meaningful only when test parameters match the intended application.
Key topics and technical requirements
- Scope and purpose
- Reproducible measurement of friction and wear for polymer-bearing combinations in well-defined test conditions (dry and boundary-lubricated).
- Emphasis on matching test conditions to real-world application to reduce uncertainty.
- Test methods
- Five model geometries are specified: A - Pin-on-disc, B - Block (or pin)-on-ring, C - Plain bearing-on-shaft, D - Sphere-on-prism, E - Rotation under thrust load. Choice depends on which geometry best simulates the practical contact.
- Specimen preparation and conditioning
- Requirements for specimen dimensions, surface condition (machined vs injection-moulded), fibre orientation, and conditioning (moisture, storage, cleaning).
- Environmental and operational control
- Controlled parameters include load, sliding velocity, temperature, and lubrication state (dry, grease, oil, solid lubricant). Temperature control is critical due to polymers’ low thermal conductivity and high thermal expansion.
- Analysis and reporting
- Measurement of coefficient of friction, linear and volumetric wear rates, friction moment and specimen temperature. Annex A provides a model test report structure.
- Special considerations for polymers
- Effects of glass transition temperature, thermal expansion, transfer layers, anisotropy from reinforcements, moisture absorption (e.g., polyamides), and potential poor repeatability requiring multiple repetitions.
Practical applications and users
ISO 7148-2 is used by:
- Bearing and material manufacturers for material selection and ranking of polymer bearing materials.
- Tribologists and test laboratories for standardized comparative testing of friction and wear.
- R&D and quality engineers in automotive, aerospace, industrial machinery, and consumer products for validating polymer bearing performance in design conditions.
- OEMs specifying bearing materials and acceptance testing criteria.
Benefits:
- Enables consistent comparison of materials and mating pairs.
- Supports design decisions, life‑expectancy estimates and lubrication strategy (dry vs boundary-lubricated).
Related standards
Keywords: ISO 7148-2, plain bearings, polymer-based bearing materials, tribological testing, friction and wear, pin-on-disc, block-on-ring, plain bearing-on-shaft, boundary lubrication, test methods.
