Overview
EN ISO 10545-20:2022 - "Ceramic tiles - Part 20: Determination of deflection of ceramic tiles for calculating their radius of curvature" - specifies a standardized laboratory method to measure the deflection of ceramic tiles under a central load (three-point test) and to calculate the tile’s radius of curvature. The method is intended for use in quality control, product characterization and conformity assessment within the tile industry and testing laboratories.
Key topics and requirements
- Test principle: Measure central deflection at breaking (Z) during a three-point bending test and compute the curvature radius using a circle-approximation formula:
r = (l² + 4·Z²) / (8·Z)
where r = curvature radius, l = span between supports, Z = deflection at breaking.
- Specimens: Random selection from the production lot; recommended specimen sizes vary with thickness (examples in the standard). Minimum of seven specimens; cut specimens allowed when agreed.
- Preconditioning: Dry specimens in an oven at (105 ± 5) °C for at least 24 h, cool to room temperature and test within 3 h.
- Apparatus requirements:
- Recording pressure gauge (accuracy 2.0%).
- Support and central cylindrical rods with rubber coverings (rubber hardness 50 ± 5 IRHD, ISO 48‑2). Typical rod diameter 20 mm, rubber thickness 5 mm, overlap 10 mm.
- Deflection measurement device able to resolve ≤ 0.03 mm and register center deflection (accuracy including self-weight ≤ 0.1 mm). If equipment introduces systematic deformation, measured Z must be corrected.
- Procedure: Place specimen with long side perpendicular to support rods, apply load per ISO 10545-4 procedures, record breaking load (F) and deflection at breaking (Z).
- Reporting: Include reference to EN ISO 10545-20:2022, tile description, specimen dimensions, d/t/l values, individual and mean Z and F values, and calculated curvature radii.
Applications and users
- Tile manufacturers: product development, process control and specification of tile flatness/curvature.
- Independent testing laboratories: standardized test reports for certification and compliance.
- Architects and specifiers: assessing suitability of tiles for curved installations or large-format applications.
- Quality managers and regulatory bodies: ensuring consistent measurement of tile deformation characteristics.
Related standards
- ISO 10545 series (tests for ceramic tiles) - this part complements other mechanical tests (e.g., ISO 10545‑4 for breaking strength).
- ISO 13006 - provides property requirements and additional information for tiles and may be referenced for classification and conformity.
Keywords: EN ISO 10545-20:2022, ceramic tiles, deflection measurement, radius of curvature, three-point test, tile testing, tile quality control.
