Lube-Tech PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
The only way to combine the need for long term tests and the need for enough repeats for an acceptable economic cost and duration, is to design experiments with a multistation approach: i.e. perform many wear experiments simultaneously. This methodology is common place in the validation of biomaterials and we extend it to various cases in industry.
Example of parallel testing: To study the wear resistance of materials under tribocorrosive conditions, in a repeatable way and with high confidence levels, the use of multistation testers is essential. Falex Tribology NV uses a 50-station wear tester (Figure 9). This tester can be set to reciprocating or unidirectional motion, use different countermaterials, geometries and/or corrosive or lubricating enviroments. Wear damage on test samples is subsequently evaluated by weight loss or 3D wear volume measurements.
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Tribocorrosion of biomaterials: In the biomedical industry there is continuous need to develop new and advanced materials, with improved wear resistance and biocompatibility. However most of the existing testing procedures are either too expensive, require long-term testing and are very. Multiple tests need to be performed to get confident data on wear. In this industrial example, the wear behaviour of the system nanostructured titanium cermet coatings vs. UHMWPE is shown in Figure 8. Both the average wear trends on the softer material, and the statistical distribution of individual measurements is shown, indicating the need for repeat testing. The main result of this test is to confirm the strong influence of surface roughness on the wear of the system. The roughness of the hard cermet is critical to functionality of the whole system. Most biomaterial prescreening protocols require testing of only the hard coating and not of the whole system, so this approach takes into account both system and environment. Thanks to the parallel testing, any variations in wear loss can be clearly mapped and safe conclusions can be drawn.
Figure 10. (a) evolution of wear loss on polyethylene pins against different biomaterials and (b) statistical analysis of obtained wear data.
Can we lubricate with water? Figure 9. (left) 50-station tester and (right) tribocorrosion cups. 36 LUBE MAGAZINE NO.136 DECEMBER 2016
Understanding the interactions between surface corrosion and mechanical processes, and having ways to measure them, may lead to the development of systems that can actually function with a water lubrication. A typical example of potential
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