Overview
EN ISO 10275:2020 - Metallic materials - Sheet and strip - Determination of tensile strain hardening exponent specifies a standardized method to determine the tensile strain hardening exponent (n) for flat products (sheet and strip) made from metallic materials. The standard defines the test principle, equipment and specimen requirements, data evaluation (including the σ = C·ε^n relationship and its logarithmic form), and reporting rules. It applies only to the portion of the stress–strain curve in the plastic range that is continuous and monotonic; for serrated curves (Portevin–Le Chatelier effect) the standard prescribes automatic linear regression of log(true stress) vs log(true plastic strain) to ensure reproducible n-values.
Key topics and requirements
- Scope: Determination of tensile strain hardening exponent for sheet and strip metallic products.
- Definition: n is the exponent in σ = C·ε^n (true stress vs true plastic strain); in log form n is the slope of ln(σ) vs ln(εp).
- Test equipment:
- Tensile testing machine verified to ISO 7500‑1, class 1 or better.
- Extensometer per ISO 9513, class 2 or better (class 1 when measuring plastic strain ratio r).
- Accurate dimensional measurement tools for thickness/width.
- Specimen and sampling: Specimen thickness equals full sheet thickness unless agreed otherwise; machining and dimensions per ISO 6892‑1.
- Procedure constraints:
- Ambient test temperature 10 °C to 35 °C (controlled tests at 23 ± 5 °C where required).
- Plastic strain rate of parallel length not to exceed 0.008 s‑1 (kept constant while determining n).
- When determining over the whole uniform plastic range, upper limit is immediately before maximum force.
- Data evaluation: Single-point method or linear regression over a specified plastic strain range; automatic regression recommended for materials showing serrated work hardening.
- Edition updates: This 2020 edition requires subtraction of elastic strain to compute true plastic strain (change from previous editions).
Applications
- Material characterization for sheet metal forming, drawing and stamping processes.
- Input data for constitutive models and finite element simulations (work hardening behavior).
- Supplier qualification, quality control and R&D for aluminium, steel and other metallic sheet/strip products.
- Process engineers, metallurgists, test laboratories and standards/quality managers use this standard to obtain reproducible, comparable n-values.
Related standards
- ISO 6892‑1 - Tensile testing at room temperature
- ISO 7500‑1 - Calibration of testing machines (force measurement)
- ISO 9513 - Calibration of extensometer systems
- ISO 10113 - Determination of plastic strain ratio (r)
Keywords: EN ISO 10275:2020, tensile strain hardening exponent, sheet and strip, metallic materials, tensile test, true stress, true plastic strain, Portevin–Le Chatelier, linear regression.
