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Sliding contact mechanics is used to account for the net increase of the bearing capacity of high wearresistant CVD diamond coatings when an outer layer of a DLC lubricant film is deposited on their top surface. Experimental results, namely the critical failure load, taken from reciprocating ball-on-plate tribological testing of such DLC/diamond bilayers, are on the basis of this statement. DC magnetron sputtering was used to grow thin DLC lubricant coatings (non-hydrogenated and hydrogenated varieties) on the top of CVD diamond films (microcrystalline and nanocrystalline types). The application of the von Mises maximum yield parameter (ffiffiffiffi J 2 p) criterion demonstrates to be an adequate method for designing low-friction and high-bearing capacity systems for high-demanding tribological applications. Calculation of ffiffiffiffi J 2 p supports that the most significant increase observed on the coatings' bearing capacity (from 20 N to 60 N) takes place when microcrystalline diamond is coated by hydrogenated DLC that decreases the initial friction coefficient peak (from 0.76 to 0.41).

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All rights reserved. No part of this publication may be reproduced in any form or by any means, without the prior written permission of the Prestressed Concrete Institute. N ineteen seventy-nine was the 25-year Silver Jubilee of the founding of the Prestressed Concrete Institute. CONTENTS Part 6-Early History of Prestressed 163 Concrete in Colorado 'Ed Thwaits is now 85 years old and fives quietly in Denver, Colorado.