ASTM D6611-16 Standard Test Method for Wet and Dry Yarn-on-Yarn Abrasion Resistance

The standard “ASTM D6611-16 Standard test method for wet and dry yarn-on-yarn abrasion resistance” developed by the American Society for Testing and Materials (ASTM) describes a procedure for measuring the abrasion resistance properties of manufactured fiber yarns under dry and wet conditions. This test method is applicable to manufactured yarns used in rope making.

In testing, a piece of yarn is wound in contact with itself between three pulleys positioned in a defined geometry to create a specific angle of intersection. A weight is attached to one end of the yarn to apply a prescribed tension. The other end is pulled back and forth with a defined stroke at a defined speed until the yarn breaks due to abrasion on itself within the wound area. The yarn abrasion test can be performed in the dry or wet state.

This test method is designed to test the dry and wet abrasion resistance of manufactured fiber yarns. This test method is particularly useful for ropes designed for use in marine environments. The test method has been used with yarns having linear densities ranging from 70 to 300 tex, but can also be used with yarns outside these ranges.

It is known that the friction between the yarn and the yarn has a significant effect on the wear resistance. The test method described in the D3412 standard is used to determine the coefficient of friction.

This test method is intended to provide additional data for specific applications such as those mentioned above and is not intended for quality control or test reports.

If there are differences of practical importance between the test results reported for two or more laboratories, comparative tests should be performed using competent statistical assistance to determine whether there is a statistical bias between them. At a minimum, the test samples used should be as homogeneous as possible, taken from material from which different test results were obtained, and randomly assigned in equal numbers to each laboratory for testing. Other materials with established test values ​​may be used for this purpose. Test results from two or more laboratories should be compared using a statistical test for unpaired data at a probability level chosen before testing.

If a bias is found, the cause must be found and corrected, or future test results must be adjusted to account for the known bias.

This test method is performed at one or more applied tensions, which may depend on the yarn material and size. The number and magnitudes of applied tensions and the number of eight sample sets are usually agreed upon in a material specification or contract order. Guidance for determining the appropriate number and magnitudes of applied tensions is included in the standard annex (Annex A2).

The yarn-on-yarn abrasion tester is schematically shown in the standard and consists of:

• Yarn guide pulleys: Three pulleys are arranged on a vertical frame with specified centerline spacing. All pulleys have the same diameter. The pulleys have low friction bearings.
• Arrangement of guide pulleys: Upper pulley centerlines are separated by 140 plus/minus 2 mm. The lower pulley centerline is 254 plus/minus 2 mm below the line joining the upper pulley centerlines. This arrangement produces a 34 degree apex angle.
• Wet test arrangement: For wet testing, the lower pulley is placed on a rod extending down from a support frame so that a water cup can be placed around it to immerse the intertwined portion of the yarn. The lower pulley has a bushing-type bearing suitable for long-term service immersed in water.
• Drive motor: An eccentric crank driven by a gear motor is arranged to be aligned with one of the upper pulleys. The crank is positioned 50 plus/minus 4 mm from the drive motor shaft to produce a thread stroke of 25 plus/minus 2 mm. The gear motor drives the crank at 60 to 70 revolutions per minute.
• Multi-station tester: Several test stations can be placed on a support frame and driven by the same motor.
• Cycle counter arrangement: A means is provided for counting the number of thread wear strokes to failure. This may be a counter directly connected to the drive motor or a counter indexed with each revolution of the crank or directly with each stroke of the thread. This counter stops counting when the thread breaks and is arranged to hold the number of strokes until reset.
• Yarn twist control: If the yarn has significant twist or the yarn tends to twist or untwist during testing, a means should be provided to control the yarn twist, such as an extension arm that follows a guide over the applied weight.

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