ISO 20482:2013

Overview

ISO 20482:2013 specifies the Erichsen cupping test method for assessing the ability of metallic sheet and strip to undergo plastic deformation in stretch forming. The standard covers test pieces with thickness from 0.1 mm to 2 mm and width ≥ 90 mm (with specified alternative tool dimensions for thicker or narrower strips). The measured outcome is the Erichsen cupping index (IE) - the depth (h) in millimetres at which a through crack appears during a spherical-punch indentation.

Key topics and requirements

• Scope: Sheet/strip metallic materials for stretch forming; alternative tool dimensions provided for 2–3 mm thickness and narrower widths.
• Test principle: Press a polished spherical punch into a clamped test piece between a die and blank holder until a through crack appears; record punch displacement as h.
• Equipment:
  • Spherical punch (standard d = 20 ±0.05 mm) or hardened steel balls as alternatives.
  • Die/blank holder/punch hardness: ≥ 750 HV30; punch surface roughness Ra ≤ 0.4 µm (per ISO 4287).
  • Measurement gauge resolution 0.1 mm; punch misalignment tolerance < 0.1 mm.
• Operating conditions:
  • Test temperature generally 10 °C to 35 °C (controlled tests at 23 ± 5 °C).
  • Blank-holder force approx. 10 kN.
  • Punch speed 5–20 mm/min (standard); 5–10 mm/min for narrow strips.
• Procedure & reporting:
  • Minimum three tests; IE is the average of individual h readings.
  • Report shall include reference to ISO 20482, test-piece identity and orientation, thickness, lubricant type, appearance after rupture, and IE values.
• Lubrication: Graphite grease recommended (Annex A) - characteristic values include graphite content 23–28%, water content 0.5–1.2%, and worked penetration 250–280.

Applications and users

ISO 20482:2013 is used to:

• Evaluate formability of metallic sheets and strips for stretch forming operations.
• Provide quality control criteria for incoming materials and production batches.
• Support material selection and process design in metalworking and fabrication.

Typical users:

• Materials testing laboratories and quality control engineers
• Metal forming and stamping engineers
• Suppliers of sheet metal for automotive, appliance, and general fabrication industries
• Standards writers and product specification teams

Related standards

• ISO 4287 - surface texture (Ra) referenced for punch roughness.
• ISO 1302 - related surface texture notation (bibliography).

Keywords: ISO 20482:2013, Erichsen cupping test, metallic materials, sheet and strip, Erichsen cupping index, stretch forming, formability test, graphite grease.