SIST ISO 6336-6:2020 - Overview
SIST ISO 6336-6:2020 is Part 6 of the ISO 6336 series and specifies the standardized information and conditions required to calculate service life (or safety factors for a required life) of spur and helical gears under variable loading, limited to the two failure modes: pitting (surface fatigue) and tooth root bending strength (tooth breakage). This second edition (2019) updates the earlier 2006 edition and integrates Annex B on equivalent cumulative damage.
Key topics and technical requirements
- Scope limitation: Applies only to pitting and tooth-root bending strength under variable loads. If other failure modes or conditions apply, refer to ISO 6336-1:2019.
- Terminology and symbols: Uses terms, symbols and abbreviations defined in ISO 6336-1 and ISO 1122-1.
- Load and stress spectra determination: Variable loading can be derived by:
- experimental measurement of operating loads,
- estimation from similar machines and operating modes,
- calculation via known excitations and mass-elastic system simulation (preferably validated experimentally).
- General calculation of service life: Methods for converting load spectra into fatigue damage and service life estimates are provided.
- Fatigue accumulation rule: Incorporates the Palmgren–Miner linear damage rule for cumulative damage assessment.
- Service strength based on single-stage strength: Procedures to derive service strength from ISO 6336 single-stage calculations, including:
- calculation of stress spectra,
- determination of pitting and bending strength values,
- determination of safety factors for required life.
- Annexes:
- Annex A (normative): Determination of the application factor K from a given load spectrum using an equivalent torque concept.
- Annex B (informative): Equivalent cumulative damage - methods for converting complex spectra to equivalent damage cycles.
- Annex C (informative): Example calculation for safety factor from a given load spectrum.
Practical applications and users
SIST ISO 6336-6:2020 is intended for engineers and organizations involved in:
- gearbox and gear set design and verification,
- mechanical and reliability engineering for rotating equipment,
- drivetrain component manufacturers and testing laboratories,
- maintenance planners assessing remaining life under variable duty cycles,
- purchasers and specifiers requiring standardized life and safety-factor calculations.
Typical uses include predicting pitting and bending fatigue life under realistic, variable operating loads, deriving safety factors for design acceptance, and converting measured or simulated load spectra into standardized life estimates.
Related standards
Keywords: SIST ISO 6336-6:2020, gear service life, variable load, pitting, tooth root bending, gear fatigue, load spectra, Palmgren–Miner, equivalent torque, application factor.
