Overview
ISO 11531:2022 - Metallic materials - Sheet and strip - Earing test specifies a standardized method to determine ear height in metal sheet and strip (nominal thickness 0.1 mm to 3 mm) after deep drawing. The earing test evaluates the tendency of drawn cylindrical cups to develop uneven rim heights ("ears") that reflect anisotropy and material properties. The standard defines test principle, equipment, test pieces, procedure, result interpretation and reporting requirements for reproducible measurement of ear formation.
Key topics and technical requirements
- Scope and specimen: Circular blanks drawn into cylindrical cups; nominal sheet thickness range 0.1–3.0 mm. A drawing ratio of about 1.8 is recommended for comparative tests.
- Test principle: Form cups by deep drawing and measure heights of ear peaks and valleys relative to cup bottom to calculate mean ear height and percentage ear height (Z).
- Equipment and tooling:
- Punch and die combinations selected based on sheet thickness (examples in the standard include punch diameters of 33 mm and 50 mm).
- Working surfaces of die, blankholder and punch must be rigid, polished and have Vickers hardness ≥ 750 HV 30.
- Blankholder force and drawing speed must be controllable to avoid ironing of ears; guidance forces are provided (e.g., for 33 mm punch: aluminium ≈ 1 000 N, steel ≈ 2 000 N).
- Procedure and conditions:
- Ambient test range 10 °C to 35 °C; controlled tests at 23 °C ± 5 °C.
- Lubrication on both faces as agreed or per product standard.
- Measurement accuracy for ear heights: ±0.05 mm.
- Results and reporting: Calculates mean peak/valley heights, mean ear height, maximum ear height and ear height percentage (Z) with rounding to 0.1 % unless otherwise specified. Test report must reference ISO 11531:2022 and include specimen ID, thickness, blank diameter, punch/die diameters, punch speed, ear count and orientation, and results.
Applications and users
ISO 11531:2022 is used to quantify earing caused by anisotropy after deep drawing. Typical users include:
- Quality and materials engineers in metal forming and deep drawing operations
- Test laboratories performing mechanical and formability testing
- Product and process engineers in automotive, packaging and appliance manufacturing evaluating sheet anisotropy and process parameters
- Standards writers and product specification authors who need objective earing criteria
Related standards
- Prepared by ISO/TC 164 (Mechanical testing of metals), Subcommittee SC 2 (Ductility testing). Related product or material standards may specify variations to tooling, lubricant or reporting - consult applicable product standards or agreements when applying ISO 11531:2022.
Keywords: ISO 11531:2022, earing test, ear height, metallic materials, sheet and strip, deep drawing, blankholder force, punch and die, formability testing.