Wear Test Method for Developing Plastic Materials for Applications Wherein a Plastic Part is Rotating or Reciprocating Against a Metal Surface 2005-01-0876
The wear test introduced in this paper can be used to determine and rank PV (pressure time velocity) capability of plastic materials for applications where a plastic part is rotating or reciprocating against a metal surface. It provides an accelerated test method to evaluate the wear performance of plastic materials. A single test can provide tribological information at multiple PV conditions. The tribological information obtained from this method includes coefficient of friction, PV (pressure times velocity) limits, and interface temperature profile. This test is currently used by General Motors Corporation to develop plastic materials for transmission thrust washer and dynamic seal applications.
The test is running in two sequences (A & B), capable of a PV range from 50,000 psi-ft/min 500,000 psi-ft/min, under dry conditions. The PV steps in sequence A are combinations of high pressure and low velocity - for applications where high loads are expected, such as thrust washers. Those in sequence B are combinations of low pressure and high velocity - for applications where high speeds are expected such as dynamic seals.
The plastic specimen (rotating unit) is composed of three 6.36 × 6.36 × 3.30 mm square pins located 120° apart on a 23.83 mm mean diameter steel disc. The total contact area is 121.29 mm2. The standard mating surface (stationary unit) is AISI C-1018 carbon steel washer with dimensions of 31.75 mm (O.D.) × 16.00 mm (I.D.) × 9.65 mm that is finished to 0.40 ± 0.05 μm per ASTM D3702. The stationary units can also be made from other types of materials (such as aluminum) with the required surface finish to simulate specific applications.
* Metric units are used in this paper except the units for Tribology. English units are acceptable for Tribology in U.S.A. Wear test conditions are usually defined with English units, such as 50,000 psi-ft/min for PV and 200 rpm for rotating speed, which are used in this paper.