ISO 4666-3:2022

Overview

ISO 4666-3:2022 describes a standardized compression flexometer (constant‑strain type) test method for vulcanized rubber. The standard defines procedures to determine temperature rise and resistance to fatigue when rubber specimens are subject to dynamic compressive flexing (the test apparatus is commonly known as the Goodrich flexometer or an equivalent device). ISO 4666-3:2022 supports accelerated laboratory assessment of materials used in items exposed to repetitive compression and flexing, such as tyres, bearings, supports, V‑belts and cable‑pulley insert rings.

Key topics and technical requirements

• Test principle: apply a fixed static pre‑stress (compression) and a superimposed cyclic compression of constant maximum amplitude while measuring temperature at the specimen base and tracking height change until fatigue failure.
• Apparatus: balance beam (lever) system with added inertial masses, upper and lower thermal‑insulating anvils, eccentric drive operating at 30 Hz ± 0.2 Hz, micrometre adjustment for specimen height, and a thermocouple contacting the specimen.
• Apparatus specifics (from standard):
  • Inertial masses of 24 kg at beam ends (or equivalent inertial system)
  • Pre‑stress weights: 11 kg (≈1.0 MPa) or 22 kg (≈2.0 MPa)
  • Eccentric stroke range: 4.45 mm to 6.35 mm
  • Test chamber temperature typically 40 °C to 100 °C (±1 °C control)
  • Thermocouple sensitivity ±0.5 °C; height measurement accuracy 0.1 mm
  • Anvil thermal conductivity ≤ 0.28 W/(m·K)
• Measurements and results: temperature rise, creep, compression set after testing, and fatigue life (number of cycles to failure).
• Calibration and precision: calibration schedule and precision data are provided; normative references include ISO 4666‑1, ISO 48‑2, ISO 18899 and ISO 23529.
• Limitations: not recommended for rubber harder than 85 IRHD; results provide predictive indications but cannot be simply correlated to in‑service performance due to wide service condition variability.

Applications and users

ISO 4666-3:2022 is intended for:

• Material and product R&D teams evaluating dynamic heat generation and fatigue resistance of vulcanized rubber
• Quality control and testing laboratories performing standardized flexometer testing
• Manufacturers of tyres, seals, bearings, V‑belts, and cable inserts assessing component durability
• Standards organizations and compliance bodies comparing test data across suppliers

Practical uses include screening compound formulations for heat build‑up, comparing fatigue life under controlled compressive flexing, and generating data to support design choices for dynamically stressed rubber components.

Related standards

• ISO 4666‑1 - Basic principles for flexometer testing
• ISO 48‑2 - Rubber hardness (IRHD)
• ISO 18899 - Guide to calibration of test equipment
• ISO 23529 - Preparation and conditioning of test pieces

Keywords: ISO 4666-3:2022, compression flexometer, Goodrich flexometer, flexometer testing, vulcanized rubber, temperature rise, fatigue resistance, constant‑strain, rubber testing.