EN 1071-12-2010 pdf download.Advanced technical ceramics – Methods of test for ceramic coatings – Part 12: Reciprocating wear test.
Reciprocating wear testing can be used to simulate the operating conditions in different sliding contacts of technological significance. In the last few years there has been an increasing interest in the use of wear and friction reducing ceramic coatings for such contacts. This draft standard has been developed to provide guidance on the use and interpretation of the test method for evaluating the potential performance of ceramic coatings in these types of contacts and to provide complementary data to that obtained from other wear test methods, e.g. micro-scale abrasion wear testing [2) and pin-on-disk wear testing [3).
It should be noted that there are many parameters in sliding contacts that affect the magnitude of friction and wear. The aim of performing any wear test Is to simulate, as closely as possible, the conditions that occur in the real application. As the deviation between the test conditions and the application conditions becomes larger, the test results will become less relevant. To add confidence to the test results, the appearance of the worn surfaces of the test samples should be compared with those of the worn surfaces of actual components to ensure that similar wear mechanisms have taken place in both cases.
NOTE Although it is relatively easy in a reciprocating wear test to reproduce the contact stress experienced in a specific tflbological contact, it might be necessary to use additional heating to ensure that the contact temperature approximates to that of the contact being simulated
5 Principle
The test consists In reciprocating a loaded pin against a flat plate and determining the wear of one or both components. Depending on the wearing system being simulated, either the pin or plate or both may be coated with the ceramic coating under test, and the test may be camed out either with or without lubrication. The pin contact face may have either a flat or rounded geometry. If the former is chosen, great care is necessary in order to ensure that the contact faces of pin and plate both lie in the same plane, as any vanation from this will produce substantially different contact conditions from those expected for a plane contacL The high contact stress generated by misalignment can be particularly damaging to brittle ceramic materials and can lead to spurious and un-reproducible results. If a rounded geometry is chosen, then the contact conditions will vary throughout the test and affect the analysis of the results.
6 Apparatus and materials
6.1 Apparatus construction
6.1.1 General
The apparatus shalt be rigid such that, during use under the maximum recommended load and reciprocating speed, the axis of the pin remains orthogonal to the plane of the test surface of the plate at all times.
NOTE I Whilst it might be more common for the pin and plate to be held rigidly during the test, additional rotary motion of the pin has been used, e.g. to simulate the conditions encountered in an artifloal hip (7J. Where such an approach is adopted. care is necessary to ensure that the axis of the pin remains rigidly orthogonal to the plane of motion.
Depending on the equipment selected, the test face of the plate may be oriented in either a horizontal or vertical plane and, for the former, the pin may be positioned either above or below the plate. Report the onentation of the test plate.
NOTE 2 It should be appreciated that different test orientations might produce different results for apparently identical test conditions as a consequence o( retention of, or loss of wear debris from the contact.
Loading between the pin and the plate may be achieved using dead loading with weights, and may be increased by use of a lever arrangement if necessary: with a calibrated spring, again using a lever arrangement if necessary; or using other suitable means. Whatever loading arrangement is used in the equipment selected It shall be such as to ensure that the load remains nominally constant throughout the duration of the test. The magnitude of the load applied can be determined by the use of suitably calibrated weights, by means of a suitably calibrated load cell, or by other suitable means. However, in all cases the load determined shall be the contact load between pin and plate.
NOTE 3 Dead weight loading systems produce more severe conditions than low mass loading systems (for example spring or pneumatic actuation). This is because. with dynamic conditions, inertia gives rise to shock loading Dead weight loading systems should be avoided at anything other than very modest reciprocation frequencies, the magnitude of which will depend upon the precise test conditions.
Where flat-ended pins are to be used, suitable means shall be provided to ensure conformance between the pin and the plate in order that the contact conditions are reproducible and so that the contact stress can be calculated, If required.
NOTE 4 One technique that has been used to ensure conformance between a fiat ended pin and the surface of the plate has been to grind a flat onto a sphencal ball and to mount the ball Into a spherical cavity, of the same diameter as the ball, which has been machined Into the end of the pin — see Figure 2. Contacting the flat on the ball with the surface of the plate will ensure that conformity is obtained. The use of a pin with a spherical cavity will also enable a ball of the same radius of curvature to be accommodated and to act as a b&l-ended pin.
In all cases where the geometry referred to in Note 4 is used, the centre of curvature of the cavity shall lie on the, extended, axis of the pin.
Equipment shall be provided with a suitable means to deliver appropriate lubricant to the contact zone and, where appropnate, means to collect used lubricant so as to enable, where required, the isolation and analysis of wear debris.
NOTE 5 Some investigators have immersed the contact zone of the plate and pin in a bath of fluid. This approach is appropriate for some situations. e.g. for simulating the wear of artificial joints [7].EN 1071-12-2010 pdf download.