Overview
ISO 10113:2020 - "Metallic materials - Sheet and strip - Determination of plastic strain ratio" specifies a standardized method to determine the plastic strain ratio (r-value) of flat metallic products (sheet and strip). The third edition (2020, corrected 2020-11) defines test principles, equipment, test-piece orientations and three test procedures (manual, semi‑automatic and automatic) so results are comparable for material qualification, product standards and forming simulations.
Key topics and technical requirements
- Definition of r-value: r = ε_p_b / ε_p_a (ratio of true plastic width strain to true plastic thickness strain). In practice r is often calculated from measured length and width changes using the law of constancy of volume: ε_p_a + ε_p_b + ε_p_l = 0 (valid up to the percentage plastic extension at maximum force, A_g).
- Three test methods:
- Manual method (no extensometer) - measure gauge length and widths before and after unloading.
- Semi‑automatic method (length extensometer only) - measures instantaneous length change and evaluates width/thickness via post‑test data.
- Automatic method (length and width extensometers) - simultaneous recording of instantaneous width and length reductions for automatic evaluation.
- Test equipment and calibration: Tensile machines shall comply with ISO 6892-1; extensometer calibration per ISO 9513. Guidance on width–extensometer arrangements (multi-point measurement to reduce necking bias) and minimum parallel length (normally ≥ 6 × original gauge width) is included.
- Derived parameters:
- Weighted average r for multiple orientations (e.g., 0°, 45°, 90°).
- Degree of planar anisotropy (Δr) to quantify directional forming behaviour.
- Error analysis and symbols: Annex A provides methods to investigate sources of error in r determination; Annex B compares international symbols.
Practical applications
- Material characterization for sheet metal forming (stamping, deep drawing).
- Input data for finite element forming simulations and process design.
- Quality control and acceptance testing in automotive, aerospace and appliance industries.
- Specification and verification in product standards for metallic sheets and strips.
Who should use ISO 10113:2020
- Materials and mechanical engineers performing tensile and forming tests.
- Metallurgical and testing laboratories seeking accredited, comparable r‑value data.
- Stampers, process engineers and CAE specialists who need reliable anisotropy input for forming simulations.
- Standards developers and product certifiers referencing consistent test procedures.
Related standards (normative references)
- ISO 6892-1 - Tensile testing of metallic materials at room temperature.
- ISO 9513 - Calibration of extensometer systems.
- ISO 80000-1 - Quantities and units (general).
Keywords: ISO 10113:2020, plastic strain ratio, r-value, metallic sheet, sheet and strip testing, tensile testing, anisotropy, forming simulation, extensometer.
