Surfaces and Their Measurement |
by David Whitehouse
395 pages (paperback)
Available from the Abrasives Mall. Order online
Like David Whitehouse's 1994 Handbook of Surface Metrology, this book is clear discussion of a complicated subject. Half the size of the previous work and benefitting from a decade in which ideas further develop, this book is the work of expert whose credentials include 20 years as the Chief Research Engineer at Taylor Hobson and 20 years in academia, currently as Chair of Engineering Science at Warwick University School of Engineering. Though he is capable of handling detailed mathemateics, Whitehouse avoids mathematical digressions to produce this very readable book that describes a current technology with it's clutter of measurement parameters and standards. According to Whitehouse that clutter is derived from the evolution of surface metrology and the inclusion of arbitary materials that relate more to the influence of special interest groups and historical materials than facility.|
One of Whitehouse’s purposes is to clarify the meaning surface metrology. Are surface parameters a variable or attibutue? What is the purpose of surface measurement: control of manfacturing processes or a specification that determines part function? Besides comments in introductory chapters, Whitehouse dedicates a chapter to discuss functional purposes of surfaces, which he says is important to extending the useful life of components.
For Whitehouse, many parameters are redudant; the integrated or average parameters are best for general use. All parameters are useful, however; most for special purposes such as machine tool diagnostics where small but significant changes in tool path are detectable with surface metrology. Throughout the book he emphacizes the importance of areal measurement, a three dimensional measure contrasting with profile measures and essential to describing part functions such as fluid flow properties.
Proper selection of parameters can be a difficult problem. For example, Whitehouse describes a typical ground cylindrical workpiece an inch in diameter and four inches long, which under normal grinding pratices, has over a million small cuts, each about 10 micron long. Amplitude parameters are best to show contact characterisitics of the workpiece. Spacing parameters show structure of grain boundries, metallurgical and material science measurements. Three dimensional areal parameters are necessary for flow behavior.
Whitehouse discusses a future for metrology with many challenges. While it is easy to reduce the size of parts - a trend in modern industry-- its is far more difficult to proportionally reduce the surface texture. The inertial and elastic effects common in everyday marco scale manufacturing become a problem when working at the micron level. The expanding range of surface measurements has a ratio of greatest to smallest units to be 50,000 to 1! Such a range demands a variety of new methods using a stylus, optical instruments, X-ray analysis, and ultrasonics. Appropriately Whitehouse devotes separate chapters to detail stylus instruments, optical methods and scanning electon microscopes.
With a focus on special application problems, other of the book's fifteen chapters cover form errors, roundness, cylindricity and sphericity. Whithouse says that his discussion of directionality shows exactly what is wrong with surface metrology today.
This book provides insight into technology behind issues that inhibit growth of the international marketplace. For example, standards vary from country to another as metrology standards in the UK and USA differs significantly from those issued in Germany and the USSR. N systems, which classify metrology parameters by size, appear as high N values to mean rough in one country but smooth in another.
Is this book useful for abrasives technology? You bet. References to grinding, honing, lapping, polishing appear throughout the book.
From either an academic or practical perspective, this book is a readable, conherent and logical treatment on issues surrounding the use of metrology --a mine field of contentious issues for industry. Like Milton Shaw's book on the materials science of abrasive processes should be “must read” for any serious student of machining abrasives technology.