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D2524-22 – Standard Test Method Technical Guide
📐 Specimen Geometry and Bundle Preparation
The D2524-22 standard specifies a flat bundle method for determining breaking tenacity of wool fibers using a ⅛ in. (3.2 mm) gage length. The specimen is prepared by hand-combing a small bundle of fibers until they are parallelized. Uniform tension is applied to remove crimp without stretching the fibers, and the fibers are cut to the exact clamp separation length. Special clamps are used to secure the bundle, maintaining the precise gage length throughout the test.
⚙️ Test Procedure and Speed Selection
The test method is designed for use with specific fiber bundle clamps and strength testing instruments, including constant-rate-of-extension (CRE), constant-rate-of-loading (CRL), and constant-rate-of-traverse (CRT) type machines. The prepared bundle is broken in the tensile testing machine after conditioning in a standard atmosphere per Practice D1776. The breaking force is recorded, and the bundle is removed for weighing. Other tensile testers may be used with appropriate adapters to accommodate the prescribed clamps. The gage length of ⅛ in. (3.2 mm) is critical for consistent results.
📊 Key Measured Properties and Calculations
Breaking tenacity is calculated from the ratio of breaking force to bundle linear density. The linear density is derived from the bundle mass and the length measured under applied tension. This test method is particularly adapted for wool in forms that can be hand-combed, such as raw wool, sliver, or top. The tenacity result is expressed in force per unit linear density, with inch-pound units considered standard. This method is suitable for acceptance testing when participating laboratories have shown acceptable between-laboratory precision using a reference wool.
| 🟦 Parameter | 📏 Specification | 📐 Details |
|---|---|---|
| Gage Length | ⅛ in. (3.2 mm) | Clamp separation |
| Specimen Type | Flat fiber bundle | Hand-combed parallel fibers |
| Tension Application | Uniform tension | Sufficient to remove crimp |
| Testing Machine | CRE, CRL, CRT | With specified clamps and adapters |
| Measured Properties | Breaking force, bundle mass | After conditioning |
| Calculated Property | Breaking tenacity | Force divided by linear density |
| Standard Units | Inch-pound | SI units in parentheses for information |
| Applicable Wool Forms | Hand-combable forms | Raw wool, sliver, top, etc. |
💡 Tip: To ensure reliable results, condition specimens in a standard atmosphere (70 ± 2°F, 65 ± 2% RH) for at least 24 hours before testing, as per Practice D1776.
⚠️ Caution: