ISO 4385:2024

Overview

ISO 4385:2024 - "Plain bearings - Compression testing of bearing materials" specifies a standardized method to evaluate the behavior of bearing materials (both bulk materials and coatings) under uniaxial compression. The procedure uses cylindrical specimens (single or paired) loaded at a constant crosshead speed while recording compressive stress and compressive strain. The standard is intended to produce reproducible stress–strain data for material selection, quality control and research on plain bearing materials.

Key topics and technical requirements

• Scope: Applicable to bulk bearing materials and coatings; determines behavior under uniformly distributed uniaxial compression.
• Specimens: Cylindrical specimens with machined parallel end faces and specified surface finish. For coated specimens, the base material must show at least 120% of the compressive stress at 0.2% plastic strain compared with the coating.
• Equipment:
  • Use a class 1 compression testing machine as per ISO 7500-1.
  • Compression plates: hardened, polished, flat, surface roughness Rz ≤ 1.6 µm (contact faces); lateral surface roughness Rz ≤ 3.2 µm.
  • Plate parallelism: deviation ≤ 0.02 mm or 0.0005 mm per mm of specimen diameter.
  • Extensometers per ISO 9513: class 1 for strain limits ≤ 2%, class 2 acceptable for larger plastic strains.
  • Temperature control: specimen and plates held constant within ±1 K when tests are not at room temperature.
• Measurement options: Extensometer can be attached directly to the specimen (gauge length ≥ 50% of specimen height) or to compression plates (gauge length = specimen height).
• Test outputs / evaluation:
  • Upper and lower compressive yield stresses
  • Compressive strain limits and strain at fracture
  • Compressive strength (stress at fracture)
  • Compressive stress at specified maximum or plastic strain (e.g., Rcm10, Rcp0.2)
  • Bulging (relative change in cross-sectional area after unloading)
• Documentation: Test report requirements defined for reproducibility and traceability.

Applications and who uses it

ISO 4385:2024 is essential for:

• Bearing manufacturers and component designers selecting materials/coatings for plain bearings
• Materials and surface-coating engineers evaluating compressive performance
• Quality control laboratories and third‑party testing services ensuring compliance and consistency
• R&D teams comparing new alloys, composites or tribological coatings under compressive loads

Practical benefits include consistent material ranking, specification of acceptance criteria, and reliable inputs for bearing design and lifetime assessments.

Related standards

Normative references within ISO 4385:2024 include:

• ISO 7500-1 (calibration of testing machines)
• ISO 9513 (extensometer calibration)
• ISO 1101 (geometrical tolerancing)
• ISO 21920-1 and ISO 21920-2 (surface texture/profile)

Keywords: ISO 4385, compression testing, plain bearings, bearing materials, coatings, compressive stress, compressive strain, extensometer, test procedure, material evaluation.