Overview
ISO 26203-2:2011 - "Metallic materials - Tensile testing at high strain rates - Part 2: Servo-hydraulic and other test systems" specifies requirements for determining stress‑strain behavior of metallic materials under high strain‑rate tensile loading. The standard covers tests (examples given for flat geometries) over a strain‑rate range from 10‑2 s‑1 to 103 s‑1, performed between 10 °C and 35 °C and, unless otherwise specified, using servo‑hydraulic-type test systems. It complements ISO 26203‑1 (elastic‑bar systems) and references ISO 6892‑1 for quasi‑static test practice.
Key topics and technical requirements
- Scope & purpose: Obtain reliable high‑rate engineering and true stress‑strain curves for dynamic material characterization (important for crash and impact simulation).
- Apparatus: Preferred use of servo‑hydraulic machines (often with slack adapters); other systems (flywheel impactors, drop towers) are acceptable if they meet the standard’s requirements. Load‑train compactness and high natural frequency are emphasized.
- Test piece geometry & preparation: Examples for flat test pieces are provided (Annex B). A transition radius of at least 10 mm is recommended. Careful cutting (spark erosion, water jet, high‑speed machining) is advised to avoid strain‑hardened edges; dynamometer zones must remain elastic.
- Measurement & instrumentation:
- Force and extension measurement requirements to ensure force equilibrium during plastic deformation at high strain rates.
- Piezoelectric load cells are suitable at lower high rates; for rates above ~50 s‑1 force measurement by strain gauges (dynamometer zone or local dynamometer) is recommended to reduce oscillation artifacts.
- Extensometry, data acquisition frequency limits, and methods for determining nominal and mean engineering strain rates are specified.
- Procedure & evaluation: Velocity selection to target strain rate in the parallel length, control for a near‑constant strain rate during the test, and guidance on deriving stress‑strain curves, key values and flow curves. Validation against quasi‑static tests (ISO 6892‑1) is recommended.
Applications and users
ISO 26203‑2 is used to produce reproducible high‑rate tensile data for:
- Crashworthiness and impact simulations in automotive and aerospace design
- Material qualification, R&D and constitutive model calibration for finite‑element analysis
- Defence, energy and manufacturing sectors where dynamic loading is critical
Primary users: materials and test engineers, mechanical designers, R&D labs, certification bodies and OEMs requiring validated high‑strain‑rate material data.
Related standards
- ISO 26203‑1 (Elastic‑bar type systems)
- ISO 6892‑1 (Quasi‑static tensile testing)
- ESIS P7 and FAT Guideline (alternative test piece geometries)
- ASTM E1012 (alignment of load train elements)
Keywords: ISO 26203-2, tensile testing, high strain rates, servo-hydraulic, metallic materials, dynamic testing, strain rate, force measurement, extensometry, crashworthiness.
