QMT News: May 2011
Conference Report: Metrology & Properties of Engineering Surfaces

The 13th International Conference  on Metrology and Properties of Engineering Surfaces was held in Twickenham, London on 12-15th April. Over 120 delegates participated in the conference and workshops concerning the issues and developments in the field of surface metrology.

One of the themes highlighted by Prof. Richard Leach, conference chair, was that of the increasing complexity of measurement and the need to roll out areal standards to industry to get designers to under stand  how metrology delivers function. A point emphasised by keynote speaker, Prof. David Whitehouse, from the University of Warwick, who commented that, “Unfortunately, aspects of functionality which involve surfaces are notoriously difficult to specify, because of the lack of appreciation  of their importance in function even by engineering designers.”.

He said the importance of roughness to functional performance and to manufacture is changing rapidly. Amongst the challenges for quality control he outlined  is  where surface parameters used to predict functional behaviour  of surfaces do not adequately  represent  the actual functional behaviour of workpieces when in use. For example, they do not take into account the actual  operating conditions, such as loads and operating speeds or there may be multiple surfaces interacting.

One factor which Prof Whitehouse said causes trouble now, and more significantly, for the future is where there is a mixture of geometries of different scales of size on any one component. This, then, may require nano as well as micro measurement. He cited the case of the Webb telescope where there is  a mixture of large macro geometry, very fine surface finish, complicated shapes and extreme problems in tolerancing and assembly.  Intended to  replace the Hubble telescope in 2014, the primary mirror is huge being 6.5 metres in diameter and made up of 18 hexagonal sub-mirrors, each of which will have to fit together precisely and have the correct roughness, shape and figure.  This illustrates the challenge for future metrology where  there will be more  and more differing scales of size  of features present on any one component and that the positioning and fitting of the constituent parts of the larger system will generate the overall shape and which will have to be achieved in-situ.

Amongst other presentations was that of  prof. Jane Wang from Northwestern University, USA, who looked  at surface topography and the interaction of surfaces with a promise of better lubrication and lower friction giving better tool wear.
www.npl.co.uk

 

  
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