ISO 4666-1:2010

Overview

ISO 4666-1:2010 - "Rubber, vulcanized - Determination of temperature rise and resistance to fatigue in flexometer testing - Part 1: Basic principles" sets out the general principles, definitions and test conditions for flexometer testing of vulcanized rubber. It explains how to measure temperature rise and determine fatigue life under cyclic flexing, and it defines key terms used across the ISO 4666 series. The standard is intended to support accelerated durability evaluations for rubber components subject to dynamic flexing (for example tyres, bearings, supports, V‑belts and cable‑pulley insert rings) while noting that simple correlations to in‑service performance cannot be assumed.

Key topics and requirements

• Definitions and concepts: Terms such as loading, pre‑stress/pre‑strain, cyclic stress/strain amplitude, heat generation, temperature rise, fatigue life, limiting fatigue deformability/stress are defined.
• Test conditions: Type and magnitude of loading (constant stress, constant strain, etc.) must be chosen to reflect intended use and to discriminate between materials.
• Test pieces: Cylindrical specimens prepared and conditioned per ISO 23529. Minimum 16 hours between vulcanization and testing; non‑product tests generally within 4 weeks (product tests preferably within 3 months). Conditioning for at least 3 hours at standard lab temperatures.
• Sample count: Two specimens for single temperature‑rise or fatigue tests; for plotting fatigue life curves use at least five, preferably ten specimens.
• Apparatus: Flexometers must be sturdy and precise; specific machine types are detailed in ISO 4666‑2/3/4. Elevated‑temperature tests require a thermostated enclosure per ISO 23529.
• Temperature measurement: Two accepted approaches - interior measurement (fine needle probe or embedded sensor) or surface measurement. Permissible measurement error: ±1 °C. Insulation is recommended to minimize conductive heat loss.
• Procedures: Basic procedures for temperature of test, measurement of temperature rise, determination of fatigue life and limiting fatigue parameters are covered; full machine‑specific procedures are in Parts 2–4.

Practical applications and who uses it

ISO 4666-1:2010 is used by:

• R&D and materials engineers developing rubber compounds and formulations to evaluate dynamic heat generation and fatigue resistance.
• Design and testing laboratories conducting accelerated durability assessments on tyres, belts, seals, bearings and other flexing rubber parts.
• Quality control and certification bodies establishing comparative performance data for production batches.
• OEMs and suppliers validating component suitability for dynamic service conditions.

Practical benefits include early detection of formulations prone to heat‑induced degradation, comparative ranking of compounds under controlled cyclic loading, and determination of limiting fatigue stress/strain for design guidance.

Related standards

• ISO 4666‑2: Rotary flexometer (machine specifics)
• ISO 4666‑3: Compression flexometer (constant‑strain type)
• ISO 4666‑4: Constant‑stress flexometer
• ISO 23529: Preparation and conditioning of rubber test pieces
• Referenced fatigue/flex‑cracking guidance: ISO 132, ISO 6943

Keywords: ISO 4666-1:2010, flexometer testing, temperature rise, fatigue life, rubber vulcanized, limiting fatigue deformability, rubber testing standards.