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D3028-95 – Standard Test Method Technical Guide
ASTM D3028-95 defines a standard test method for determining the sliding (kinetic) coefficient of friction of plastic solids. Using a variable-speed, variable normal-force frictionometer, this method allows precise measurement across a velocity range of 0.10 to 3.00 m/s. The standard provides a robust framework for engineering design data by offering two distinct testing procedures tailored to different investigative goals.
📐 Specimen Geometry and Types
This test method is designed exclusively for rigid or self-supporting solids that can be machined to specified dimensions. A critical caveat in the standard (Note 1) specifically warns against mounting thin sheeting, film, or foil as fixed specimens due to the inherent difficulty in meeting the required weight and concentricity tolerances. Furthermore, sheeting exceeding 1.00 mm (0.040 in.) in thickness should generally not be tested on a standard diameter mounting wheel.
⚠️ Geometric Accuracy Alert: An error accumulation of 1 % per 0.50 mm (0.020 in.) of sheeting thickness results from increased standard diameter. If this error exceeds your tolerance, the use of undersize mounting wheels is permitted to maintain the fidelity of the friction measurement.
⚙️ Test Procedure and Speed Selection
The selection of a procedure is determined by the specific interests of the investigator. The standard recognizes that many variables affect frictional behavior, and these methods allow for optimized correlation between laboratory results and actual service conditions.
| 🟦 Procedure | ⚡ Focus Area | 🎯 Detailed Description |
|---|---|---|
| Procedure A | Variable-Velocity Coefficient | Provides data across many different velocities. Wear and temperature effects are kept to a minimum. Hysteresis (differences between ascending and descending velocity scales) can indicate their influence on the material. |
| Procedure B | Constant-Velocity Coefficient | Provides data specifically with respect to wear and temperature over an extended period. The velocity is held constant, eliminating its effects and isolating the tribological degradation of the material. |
💡 Engineering Design Relevance: As stated in the scope, test data obtained by this method is directly relevant for use in engineering design. By testing under both variable and constant velocity conditions, engineers can fully characterize a material’s potential performance in diverse slip applications.
📊 Key Measured Properties and Technical Data
The kinetic coefficient of friction serves as the primary index. Because frictional properties depend heavily on surface conditions, perfectly identical results between like specimens should not necessarily be expected. The values stated in SI units are regarded as the standard.
| 🟦 Parameter | 📏 Specification / Standard Value |
|---|---|
| Speed Range | 0.10 to 3.00 m/s |
| Instrument Type | Variable Speed, Variable Normal-Force Frictionometer |
| Max Sheeting Thickness (Standard Wheel) | 1.00 mm (0.040 in.) |
| Thickness Error Rate | 1 % error per 0.50 mm (0.020 in.) |
| Specimen Physical Form | Rigid or Self-Supporting Solids |
The standard does not address all safety concerns, if any, associated with its use. It remains the responsibility of the user to establish appropriate safety and health practices.
❓ Frequently Asked Questions
🔍 What is the specified speed range for the frictionometer in ASTM D3028-95?
The instrument is designed to operate through a speed range of approximately 0.10 to 3.00 m/s.
💡 What is the critical thickness limit for plastic sheeting on a standard wheel?
Sheeting exceeding 1.00 mm (0.040 in.) in thickness should generally not be tested on a standard diameter mounting wheel to avoid significant geometric error.
⚡ What is the key difference between Procedure A and Procedure B?
Procedure A varies the