ISO 20056-1:2017

Overview

ISO 20056-1:2017 - "Rolling bearings - Load ratings for hybrid bearings with rolling elements made of ceramic - Part 1: Dynamic load ratings" - specifies methods to calculate dynamic load ratings for hybrid rolling bearings that combine hardened bearing steel raceways with silicon nitride rolling elements. The standard provides formulae, rating factors and guidance (including tabulated guide values in Annex B) so designers and engineers can determine basic dynamic radial and axial load ratings and fatigue load limits for hybrid bearings.

Key topics and technical requirements

• Scope: Methods apply to hybrid bearings with contemporary, high-quality hardened steel rings and silicon nitride rolling elements made to commonly used material and manufacturing quality and surface finish.
• Dynamic load rating calculations: The document gives explicit formula families for:
  • Ball bearings (basic dynamic radial and axial load ratings)
  • Roller bearings (radial and thrust roller bearings)
  • Distinct formula sets for small and large element diameters (D ≤ 25.4 mm and D > 25.4 mm where applicable)
• Rating and reduction factors: Values for the key factors b, f, λ, η, and combinations (e.g., λ×ν for rollers) are tabulated for different bearing types (see Tables 1 and 2). Annex B provides tabulated guide values for the geometry-dependent factor f.
• Fatigue load limit (Cu): Annex A describes the calculation of the fatigue load limit of a single contact, taking into account the different elastic properties of silicon nitride and rolling bearing steel. Typical material parameters cited:
  • Silicon nitride: E = 300 000 MPa, Poisson’s ratio ν = 0.26
  • Bearing steel: E = 207 000 MPa, ν = 0.30
  • For hybrid ball bearings with silicon nitride balls, the fatigue load limit is about 73% of the equivalent steel-element bearing.
• Notation and symbols: The standard defines symbols (D, Z, α, γ, χ, E(χ), etc.) consistent with ISO practice to ensure reproducible calculations.

Practical applications and who uses this standard

ISO 20056-1:2017 is intended for:

• Bearing designers and manufacturers for hybrid (ceramic-steel) product development
• Mechanical and reliability engineers performing bearing selection and life assessment
• Tribology specialists and test engineers validating rolling-element performance
• Procurement and standards compliance teams specifying load ratings for hybrid bearings

The standard helps ensure consistent, comparable dynamic load rating calculations for hybrid bearings in industrial applications where silicon nitride rolling elements are used.

Related standards

• ISO 281 - Rolling bearings - Dynamic load ratings and rating life (normative reference)
• ISO 5593 - Rolling bearings - Vocabulary (terms and definitions)
• Additional referenced documents for element dimensions and tolerances: ISO 26602, ISO 3290‑2, ISO 12297‑2

Keywords: ISO 20056-1:2017, hybrid bearings, dynamic load ratings, silicon nitride, rolling bearings, fatigue load limit, ISO 281.