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.
Open preview (PDF)Liquid crystal display devices - Part 40-4: Mechanical testing of display cover glass for mobile devices - Biaxial flexural strength (ring-on-ring)
