IEC 61747-40-4:2015

Overview - IEC 61747-40-4:2015 (Biaxial flexural strength, ring-on-ring)

IEC 61747-40-4:2015 defines a mechanical performance test procedure for display cover glass used in mobile devices, specifically measuring as-received surface fracture load by a biaxial flexure (ring-on-ring) method. The test quantifies how cover glass behaves under a concentrated, centrally applied load while supported by a concentric support ring - a common way to assess glass used for touchscreens and mobile displays.

Key technical topics and requirements

• Scope and objective: Measurement of surface fracture load for electronic flat panel display cover glass using ring-on-ring biaxial flexure.
• Specimen dimensions: Typical specimens are 50–60 mm wide, 50–110 mm long, and 0.55–2.0 mm thick.
• Apparatus & setup:
  • Concentric load ring (top) and support ring (bottom); rings must be parallel and concentric.
  • Support ring covered with PTFE film and the specimen’s loaded surface covered with polymeric adhesive tape to protect fracture surfaces and reduce debris scatter.
  • Testing frame constructed from steel; maximum forces typically less than 10 kN.
• Control and measurement:
  • Crosshead traverse rates range from 0.001 mm/min to 1000 mm/min.
  • Controller must record fracture load and allow rate setting; sampling at ≥10 kHz for load and displacement.
• Test method notes:
  • Loads at fracture are reported as measured (not converted to classical strength values) because non-linear behaviors can invalidate simple normalization formulas.
  • Statistical analysis of a sample of specimens is required; Weibull analysis is referenced for failure statistics (see IEC 61649).
• Safety: Hazards addressed include broken glass, crush risks during frame operation, flying debris; emergency stop and single-operator safeguards are mandated.

Practical applications and who uses this standard

• Product engineers and materials scientists validating cover glass mechanical performance for smartphones, tablets and wearable displays.
• Quality assurance and manufacturing teams performing acceptance testing or process control on strengthened (e.g., ion-exchanged) glass.
• R&D and failure analysis groups comparing biaxial flexural strength across formulations, treatments or suppliers.
• Test labs offering third‑party mechanical testing and certification services for mobile display components.

Related standards

• IEC 61747-40-1 - Guidelines for mechanical testing of display cover glass for mobile devices.
• IEC 61649:2008 - Weibull analysis for statistical evaluation of fracture data.

Keywords: IEC 61747-40-4:2015, biaxial flexural strength, ring-on-ring, display cover glass, mobile devices, mechanical testing, Weibull analysis, testing apparatus, surface fracture load.