Overview
ISO 20120:2025 specifies a standardized laboratory method to measure the coefficient of friction and its evolution for synchronizers lubricated by manual transmission fluids (MTF) using a high‑frequency, linear‑oscillation (SRV) test machine. The method uses a flat areal contact (flat‑on‑flat) geometry and a translatory oscillation apparatus to reproduce the tribological interactions typical of manual‑gear synchronizer interfaces. ISO 20120 is intended as a rapid, high‑precision evaluation tool to screen lubricant formulations and materials prior to full bench or vehicle testing.
Key topics and technical requirements
- Test principle: Oscillating upper and lower flat specimens with lubricant between them; lateral friction force is vibration‑compensated and used to compute the coefficient of friction (peak‑to‑peak per cycle).
- Typical test parameters (documented defaults):
- Normal force: 260 N (≈ 3.1 MPa contact pressure)
- Oscillation frequency: 50 Hz
- Stroke length: 1.0 mm
- Test temperature: 60 °C (optionally 80 °C)
- Test duration: 2 h
- Equipment: SRV translatory oscillation apparatus (SRV models 4 and 5, horizontal configuration). Load capability and optional cooling/heating and environmental monitoring are addressed.
- Specimen geometry and preparation: Flat ring disk and lower disk specimens with defined surface parameters; cleaning using non‑chlorinated, non‑film‑forming solvents per DIN 51631.
- Data acquisition & reporting: Sample rates and channels for friction/time/temperature are specified; calibration, inspection, cut‑off criteria for friction and required test report details are included.
- Precision: Repeatability and reproducibility clauses are provided; users are advised to validate correlation with real‑world performance.
- Safety and materials: Warnings on solvents and machine noise; adherence to machine operator training.
Practical applications and intended users
- Lubricant formulators screening MTF candidates for synchronizer friction behavior.
- Automotive OEMs and tier‑1 suppliers evaluating material/coating combinations for synchronizer rings.
- Independent test laboratories performing comparative friction testing and quality control.
- Tribologists and R&D teams using SRV tribometry to accelerate development cycles and reduce reliance on longer bench tests (e.g., ASTM D5579, CEC L‑66‑99).
- The method is particularly useful for rapid filtration of formulations to identify promising MTFs before committing to full component or vehicle homologation tests.
Related standards and references
- IEC 60751 (platinum resistance thermometers)
- DIN 51631 (special‑boiling‑point spirits - cleaning solvents)
- ASTM D5579, CEC L‑66‑99 (synchronizer bench tests)
- ASTM D8227‑20 (source material referenced)
Keywords: ISO 20120, synchronizer lubricants, manual transmission fluids (MTF), coefficient of friction, SRV test, high‑frequency linear oscillation, tribology, transmission lubricant testing.