ISO 16842:2021

Overview

ISO 16842:2021 specifies a standardized biaxial tensile testing method using a cruciform test piece to measure the biaxial stress–strain behavior of sheet and strip metallic materials. The standard defines the recommended cruciform geometry, strain-measurement positions, testing-machine requirements and data reduction to determine true stress, true strain and yield-related properties under biaxial tension. Key scope limits include sheet thickness ≥ 0.1 mm and ≤ 0.08 × arm width, and test temperature between 10 °C and 35 °C.

Keywords: ISO 16842:2021, biaxial tensile testing, cruciform test piece, sheet metals, biaxial stress-strain.

Key topics and technical requirements

• Cruciform test piece geometry

  • Recommended shape and dimensions (gauge area, arms, grip length).
  • Arm width B normally ≥ 30 mm; thickness a must satisfy a ≤ 0.08 B (exceptions by agreement).
  • Seven slits per arm (central plus three on each side) with precise positioning and slit length L satisfying B ≤ L ≤ 2B.
  • Slit width w should be as small as possible (preferably < 0.3 mm).

• Measurement and instrumentation

  • Simultaneous, continuous measurement of biaxial forces and orthogonal strain components in the gauge area.
  • Strain measurement positions and force measurement methods are specified to limit stress-calculation error (estimated < 2.0 % with recommended geometry and positions).

• Testing machine requirements

  • Biaxial tensile testing machine must hold four grips in a single plane within ±0.1 mm and apply controlled orthogonal forces/strains (see Annex C for examples).

• Data reduction and limits

  • Procedures for determining original cross-sectional area, true stress, true strain and true plastic strain.
  • The maximum applicable equivalent plastic strain in the gauge area depends on force ratio, slit width, work-hardening exponent (n-value) and material anisotropy (see Annex B).
  • Methods for measuring yield surface and related analyses (Annex A).

Applications and users

ISO 16842:2021 is used by:

• Material testing laboratories and certification bodies for characterizing sheet-metal biaxial behavior.
• Metals producers and suppliers to specify and verify mechanical performance.
• Automotive, aerospace and electronics OEMs for forming-limit studies, sheet forming simulations and constitutive-model calibration.
• R&D and academic groups studying anisotropy, work hardening and yield surfaces under multiaxial loading.

Practical uses include calibrating finite-element material models, defining forming processes, and assessing material suitability for biaxially loaded components.

Related standards

• ISO 7500-1 (calibration/verification of tension/compression testing machines) - normative reference.
• ISO 80000-1 (quantities and units) - normative reference.
• ISO 10275 is cited in the bibliography in the published document.

For implementation, users should follow the detailed clauses, Annex A–C and report requirements in ISO 16842:2021 to ensure reproducible, accurate biaxial test data.