Thursday, 9 April 2009

The New Science of Strong Materials

"The New Science of Strong Materials" by J.E. Gordon: A Review
This book looks at the science of materials. As Professor Gordon explains in his introduction this science is concerned with problems such as "Why do things break? Why do materials have any strength at all? Why are some solids stronger than others? Why is steel tough and why is glass brittle? Why does wood split? What do we really mean by 'strength' and ' toughness ' and ' brittleness ' ."
These problems, so stated, may appear simple, easily solved by common sense; the task of material science, however is to look for universal theories to explain the behaviour of materials, not to rely upon 'rule of thumb' methods, and to criticise and improve upon what may appear, at first sight, to be intuitively obvious. For instance, if you have a hole in a material, such as a hole in a sheet of metal, then this causes a local stress which weakens the metal around that point. Intuition may suggest that the stress is related to the size of the hole, but intuition would be wrong. In fact, as Professor Gordon points out, "the increase in local stress, which can be calculated, depends solely upon the shape of the hole and has nothing at all to do with its size.. The root cause of the Comet aircraft disasters was a rivet hole perhaps an eighth of an inch in diameter."
It is interesting how many things come under the purview of materials science. Professor Gordon takes the reader on a guided tour which looks at architecture, submarines, aeroplanes, timber, glue, metals and plastics. As well as considering the aspect of materials science involved, his narrative is enlivened by historical sketches of the construction methods, explaining why some constructs succeeded, and other failed, often with catastrophic consequences.
Professor Gordon is not without a sense of humour, and this book contains many apposite anecdotes. My personal favourite is the comment made on Pliny the Elder. "Pliny the Elder", he writes, "gives directions for distinguishing a genuine diamond. It should be put, he says, on a blacksmith's anvil and smitten with a heavy hammer as hard as possible. If it breaks it is not a true diamond. It is likely that a good many valuable stones were destroyed in this way because Pliny was muddling up hardness and toughness." This is not only an amusing story, it also illustrates, with great clarity, the difference between hardness and toughness; such clarity is a characteristic of Professor Gordon's approach.
After reading this book, the reader will understand how a good engineer must consider both forces and materials. As an example, consider the building of a dam. The engineer must not only consider forces on the dam wall, and forces exerted by the dam wall (a problem in statics), but also the structure of the material involved, and how well it can stand up to stress. One dam wall may have the same size and weight as another, but it is a fallacy to assume that it must, therefore, be as reliable. Only precise measurements on a sample of the materials used can enable the engineer to calculate this, which is why specifications given are so important.
This is an interesting and informative book. It contains a very small amount of elementary algebra, but nothing that is beyond the reach of anyone of moderate intelligence, and that can be skipped by those not mathematically inclined.


st-ouennais said...

Yep its a very good book. But then my first degree is in materials science.

TonyTheProf said...

What was your other degree / doctorate in?

st-ouennais said...

Er ahem um, yes well 'computer modelling the mechanical properties of perforated and porous materials' That involved lots of time shuttling between the materials science, mechanical engineering and computer departments.