Abstract
We are pleased to introduce this special issue of MST consisting of twenty-two papers on the theme of hardness from both theoretical/modelling and experimental viewpoints. Coverage has been designed specifically to address a wide range of length scales, from macro to nano, and loading rates from highly instrumented nano-indentation to those characteristic of ballistic impact.
The issue has had a long gestation, beginning when Ron Armstrong communicated with John Knott in late 2009 about doing an MST special issue on the topic. John checked around: the indication was that several efforts were under way, but mostly outside of the metals community. The suggestion was that it might be useful to propose a symposium on the topic in order to test focused interest in the subject in the materials community. Stephen Walley expressed interest in participating, in continuation of the long-standing activity initiated by David Tabor on hardness at the Cavendish Laboratory. David Bahr and Naresh Thadhani then put forward a proposal to TMS, on behalf of the four of us, to hold such a symposium at MS&T 2011 with the intention of publishing offered papers after normal review in an MST focus issue. Emphasis was given to the effort being a joint US (TMS) and UK (IOM3) activity.
The proposal was approved and a special effort was made to invite researchers worldwide known to be active in the subject area to participate. The result can be said to be successful, in that the symposium attracted more than 60 papers over the four days of MS&T 2011 in Columbus, OH (17–20 October), forming a major strand of the meeting. We were also pleased to obtain the positive response demonstrated by this special issue, comprising twenty-plus articles from researchers representing a dozen countries. Also included in the issue are a ‘pre-editorial’ by John Knott, written at the inception of the issue in early 2010, raising a number of questions raised by the theme, and a response by Steve Bull assessing the extent to which contributions at the meeting addressed and answered these questions.
We would like to thank the authors and referees who have contributed to the publication of this issue. Thanks are also due to Maney Publishing and Hysitron Inc. for their sponsorship of the symposium and this special issue.