ISO 11749:2023

Overview - ISO 11749:2023 (V-ribbed belts fatigue test)

ISO 11749:2023 specifies a dynamic fatigue test method for quality control of V-ribbed belts (PK profile) used mainly in automotive accessory drives. The standard defines test machine layouts (two-, three- and four-pulley configurations), test conditions, measurement requirements and reporting details to determine belt life under specified load, speed and tensioning conditions. Dimensional characteristics of belts and pulleys are covered separately by ISO 9981.

Key topics and technical requirements

• Test principle: Dynamic endurance testing on robust test machines to determine when a belt fails to meet agreed performance criteria (power transmission, slip, retensioning cycles).
• Machine layouts: Acceptable configurations for two-, three- and four-pulley test rigs, with alignment tolerances and guidance on which belt lengths fit each layout.
• Tensioning methods: Procedures for tests with fixed belt tensioning force and with constant belt tensioning force (newly clarified in the 2023 edition).
• Pulley specifications:
  • Test pulleys made of steel with surface hardness ~55 HRC.
  • Pulley groove surface roughness R < 3.2 µm.
  • Groove geometry examples: groove pitch 3.56 mm and groove angle 40° (Table 2 provides detailed dimensions and tolerances).
• Measurement accuracy: Means to determine belt slip to ±0.1% and limits for radial/axial runout (≤ 0.25 mm TIR).
• Environmental control: Specified test-room temperature range and requirement to record mean temperature during testing.
• Documentation: Required test report items (test conditions, tensioning, slip, retensioning, life in hours, etc.).

Practical applications and users

Who uses ISO 11749:2023:

• Automotive belt manufacturers - to validate product durability and maintain quality control for accessory drive belts.
• OEMs and Tier‑1 suppliers - to specify belt acceptance criteria and ensure compatibility with vehicle accessory systems.
• Test laboratories and R&D centers - to conduct standardized fatigue tests, compare designs and certify belts to customer requirements.
• Component designers and quality engineers - to evaluate belt/pulley interactions and inform maintenance/service-life expectations.

Practical benefits:

• Consistent, repeatable method to assess V-ribbed belt fatigue life.
• Basis for supplier agreements on minimum acceptable life, retensioning cycles and transmitted power.
• Facilitates comparability between belt designs and material/process changes.

Related standards

• ISO 9981 - Dimensional characteristics of V-ribbed belts and corresponding pulleys (referenced for groove profiles and dimensional design).
• ISO 254 - Surface roughness definitions and measurement methods (used for pulley surface roughness guidance).

Keywords: ISO 11749:2023, V-ribbed belts, fatigue test, PK profile, belt drives, automotive accessory drive, pulley dimensions, ISO 9981.