Overview
ISO 13061-4:2014 specifies a standardized test method for determining the modulus of elasticity (E) of wood in static bending using small clear specimens. The method measures mid-span deflection of a simply supported beam under a gradually increasing transverse load within the linear portion of the load–deflection curve. It defines specimen geometry, conditioning, apparatus accuracy, test procedure, calculation and reporting requirements to ensure reproducible results for comparative testing and material characterization.
Key topics and requirements
- Scope: Determination of modulus of elasticity in static bending for small, clear wood specimens.
- Specimen geometry: Rectangular prisms with a square cross-section not less than 20 mm × 20 mm; span equal to 14 × specimen height; one face parallel to radial grain.
- Moisture conditioning: Test pieces may be tested green (≥ fibre saturation point) or air-dry. Air-dry conditioning: 65 ±5 % RH at 20 ±2 °C until constant mass (two weighings 8 h apart differing by ≤ 0.2 %).
- Apparatus and accuracy:
- Testing machine with rigid frame, calibrated force measurement (accuracy 1 %).
- Deflection measuring device accurate to at least 0.02 mm.
- Dimensional measurement accuracy 0.1 mm.
- Load-bearing block radius ≥ 30 mm to avoid indentation.
- Procedure:
- Apply transverse load at mid-span to radial or tangential face.
- Load continuously at constant rate (rate must be reported).
- Select upper and lower load limits within the linear region (typically between 0.1 and 0.4 of estimated breaking load).
- Measure deflection between these limits and calculate E.
- Calculation and adjustment:
- The standard gives the formula for E from load, span, cross-section and measured deflection and requires results to 0.1 N/mm (MPa) precision.
- When required, E can be adjusted to a reference moisture content (12 %) using a recognized national/international method; an approximate correction factor (α = 0.02) and guidance for near-12 % moisture are provided.
- Reporting: Test configuration, specimen sizes, conditioning, moisture content, density, speed of testing, loading direction (radial/tangential), results and statistics, date and testing organization.
Applications and users
- Practical uses:
- Material characterization for timber design and quality control.
- Comparative testing of species, grades, or processing effects.
- Input data for structural engineering, finite-element models and product development.
- Typical users:
- Timber testing laboratories, standards bodies and certification agencies
- Wood products manufacturers and quality engineers
- Structural and materials engineers, researchers in wood science
Related standards
Keywords: ISO 13061-4:2014, modulus of elasticity, static bending, wood testing, small clear wood specimens, deflection measurement, moisture conditioning, span-to-depth ratio.
Open preview (PDF)Physical and mechanical properties of wood — Test methods for small clear wood specimens — Part 4: Determination of modulus of elasticity in static bending
