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D2659-16 – Standard Test Method Technical Guide
ASTM D2659-16 (Reapproved 2023) establishes a standardized method for determining the column crush properties of blown thermoplastic containers, simulating the axial compressive stresses encountered during stacking, transport, and storage. The test is conducted at a constant rate of compressive deflection to precisely measure the load-bearing and deformation characteristics of the container for design validation and quality control.
📐 Specimen Requirements and Conditioning
This test method primarily addresses containers that are blown commercially or in the laboratory, though it is generally applicable to containers of suitable geometry produced by other processes such as thermoforming and injection molding (Note 1). Specimens are tested in their finished, unmodified form. Prior to testing, all specimens must be conditioned in accordance with Practice D618 at standard laboratory conditions of 23 ± 2°C and 50 ± 5 % relative humidity to ensure reproducibility of the mechanical properties.
⚙️ Test Procedure and Speed Selection
The container is aligned vertically between two flat, rigid compression platens. A constant rate of compressive deflection is applied using a testing machine calibrated per Practices E4 (Force Verification) and E83 (Deflection Verification). The standard suggests selecting a testing speed that produces a failure within a 30 to 60 second time frame, ensuring a quasi-static loading condition. The load and corresponding deflection are recorded continuously to generate the complete load-deformation curve.
📊 Key Measured Properties and Calculations
Four principal values are derived from the load-deformation curve as defined in the standard’s terminology section. These metrics provide a comprehensive evaluation of the container’s structural performance under columnar crush conditions.
| 🟦 Property (Section) | 📏 Definition | 📐 SI Unit | 🎯 Key Observation |
|---|---|---|---|
| Crushing Yield Load (3.2.4) | First load where deflection increases without an increase in load. | kg | Onset of structural yielding or buckling. |
| Crushing Load at Failure (3.2.3) | Load causing fracture or parting of the material. | kg | Ultimate axial load capacity of the container. |
| Apparent Crushing Stiffness (3.2.1) | Ratio of crushing load to corresponding deflection on the linear curve portion. | N/m | Structural rigidity of the container shell. |
| Deflection at Crushing Yield Load (3.2.5) | Decrease in container length along the axis of testing at the yield load. | mm | Deformation capacity at initial structural collapse. |
⚠️ Handling Multiple Yield Loads: As noted in Section 3.2.4 (Note 3), design features can result in multiple yield load observations. The first significant abrupt change where deflection increases without a load increase should be carefully identified. This phenomenon is a valid design characteristic and must be clearly described in the test report.
💡 Intended Use and Applicability: While developed specifically for blow-molded containers (Section 1.1), the general principles of this standard are applicable to a wider range of containers. The standard emphasizes using SI units (kg, N/m, mm) as the primary reporting units (Section 1.2).
❓ Frequently Asked Questions
🔍 What is the primary difference between the “crushing yield load” and the “crushing load at failure”?