ISO 4378-2:2024

Overview

ISO 4378-2:2024 - Plain bearings - Terms, definitions, classification and symbols - Part 2: Friction and wear is a terminology standard that establishes consistent definitions, classifications and symbols for friction and wear phenomena specific to plain bearings. This fourth edition updates and consolidates commonly used terms (with selected short forms), illustrative figures, a bibliography and an index to reduce ambiguity in design, testing and technical communication in bearing and tribology work.

Key topics

The standard focuses on terminology and classification rather than prescriptive test methods or design limits. Major technical topics covered include:

• Fundamental friction terms: friction, friction force, coefficient of friction, friction angle, static vs dynamic friction.
• Classification by motion: sliding motion and sliding friction; rolling motion and rolling friction; combined rolling/sliding; traction and coefficient of traction.
• Classification by lubricant condition: unlubricated (dry) friction, lubricated friction, boundary friction, mixed friction, fluid friction.
• Wear processes and types: mechanical wear (abrasive, adhesive, hydro‑abrasive, fatigue, cavitation, fretting), mechano‑chemical wear (tribo‑chemical, oxidative wear, fretting corrosion), and other processes (electroerosive, thermal wear).
• Wear metrics and quantities: wear, wear rate, specific wear rate (wear intensity), mild vs severe wear.
• Phenomena and failure modes: adhesion, transfer of material, seizure, stick‑slip motion, vibration‑related terms for rotating shafts supported by plain bearings.
• Figures, symbols and an alphabetical index to support clear cross‑reference and unambiguous use of terms.

Applications and users

ISO 4378-2:2024 is practical for professionals who need a common language about bearing friction and wear:

• Bearing design and mechanical engineers specifying plain bearings and tribological interfaces.
• Tribologists and failure‑analysis teams diagnosing wear modes (abrasion, adhesion, fatigue, fretting, cavitation).
• Test laboratories and QA teams reporting wear rates, coefficients of friction and test outcomes.
• Maintenance, reliability and asset management staff preparing inspection criteria and lubrication strategies.
• Standards writers, educators and technical authors who require authoritative terminology for documentation and training materials.

Practical uses include creating unambiguous specifications, interpreting test reports, choosing lubricants and materials, and improving cross‑discipline communication in bearing selection and root‑cause analysis.

Related standards

• ISO 4378 is a multi‑part series; a complete list of parts is available on the ISO website.
• ISO/TC 123 (Plain bearings) is the responsible technical committee.
• For standardized term look‑up, consult the ISO Online Browsing Platform (OBP) and IEC Electropedia.

Keywords: ISO 4378-2:2024, plain bearings, friction and wear, coefficient of friction, wear rate, adhesive wear, abrasive wear, boundary lubrication, tribology.