Information on the most widely used ASTM standards within the materials testing industry
ISO 13061-6, ASTM D143, ASTM D1037
General introduction
A tensile fixture for wood testing is a specialized device attached to a universal testing machine (UTM) designed to hold a wood specimen and apply a tensile (pulling) force parallel to its grain. This test measures the ultimate tensile strength and modulus of elasticity of the wood, which are critical properties for structural engineering, construction, and material science.
Wood Tensile Fixture (Tension Parallel to Grain) is used to determine the maximum stress the wood can withstand before failing when pulled along the direction of its fibers. The standards ISO 13061-6 (ISO 3345), ASTM D143, and ASTM D1037 define the procedures for this test.

The standardsISO 13061-6 (ISO 3345), ASTM D143, and ASTM D1037 define the procedures for this test, each with specific requirements for the specimen and the fixture.
* ISO 13061-6 (ISO 3345): Wood — Determination of ultimate tensile stress parallel to grain. An international standard focusing on solid wood.
* ASTM D143: Standard Test Methods for Small Clear Specimens of Timber. A widely used American standard covering various mechanical tests on small, clear wood samples, including tension parallel to grain.
* ASTM D1037: Standard Test Methods for Evaluating Properties of Wood-Base Fiber and Particle Panel Materials. While primarily for composite panels, it includes tensile test methods that share principles with solid wood testing.

Main features
Symmetrical grip structure ensures the applied load is precisely parallel to the wood grain, preventing bending or torsional stresses that could distort results
Self-aligning features (e.g., spherical bearings or swivel connections) compensate for minor specimen misalignment
Guiding channels maintain specimen position during loading
This specialized fixture is used for:
Testing structural lumber strength properties
Quality control in timber production
Research and development of engineered wood products
Compliance testing for building codes and standards
Determining allowable tensile stresses for wood design
Fixture Setup
Mount fixture on universal testing machine with proper alignment
Insert specimen into lower grip, ensuring grain direction matches load axis
Apply initial clamping force (softwoods: 100-150 psi/ 690-1034 kPa; hardwoods: 175-250 psi/ 1207-1724 kPa)
Secure upper grip around specimen
(Optional) Attach extensometer to measure deformation over gauge length.
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