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Why Things Break: Understanding the World By the Way It Comes Apart (Anglais) Broché – 28 septembre 2004


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ATOMS, MARBLES, and FRACTURE


What incredible luck. The waitress had just unknowingly placed the most amazing water glass on our table. Halfway up the glass was a crack about two centimeters long. This was one of those fantastic cracks where neither end intersected a surface. These are stable and, if left alone, will simply hibernate. Water does not leak from these cracks, their presence is known only by the reflection of light from their surfaces. If disturbed, however, they wake up, sometimes violently, growing with incredible speed, often branching as they go, reducing whatever contained them in their quiescent state to a pile of razor-sharp shards.

Though the crack in this water glass was a rare find, it was even more remarkable in that it was oriented nearly parallel to the bottom of the glass. If gently awakened, the ends of this crack could be made to grow around the glass and meet at the same point, dividing the glass into two parts. Quickly downing the water, I used the handle of a butter knife to tap on the glass, ever so gently, near the tips of the crack. Too sharp a blow and the crack would become uncontrollable. With each tap, the crack grew slightly and stopped. Slowly the ends of the crack worked their way around the glass and, with no apparent sound, they joined. As if by magic, aided only by the butter knife "wand," the glass had been separated.

I was delighted with my carefully divided glass. My lunch companions, however, were less than pleased. I was, after all, with my impressionable young nieces and their parents. The looks on their faces suggested that I had just committed the most ill-conceived of social faux pas. Though this incident occurred nearly ten years ago, the breaking of the water glass is still a subject that causes my nieces and their parents to reflect on my integrity. My "crime" was a minor one. Indeed, the glass would not have survived even one more washing. The thermal strains caused by heating and cooling would have marked the end of the glass's useful life, and such a marvelous crack deserved a more significant death.

My interest in cracks and fracture began in early childhood, when I became fascinated by the idea that it might be possible to prevent things from breaking. I imagined what the world would be like if things never broke. In my child's mind, I pictured both the great and ordinary creations of humankind surviving the ages untouched and pristine. Little did I realize that this simple fantasy would direct my life and open doors I never thought existed.

Perhaps my interest was a by-product of growing up in the 1950s and 1960s. Every child lived with the fear that "the bomb" could be dropped at any minute. In school, it was common for a teacher to open the door of a classroom and yell, "Duck and cover!" In response to this warning, we students were expected to fling ourselves to the floor in a modified fetal position, with hands clasped across the back of the neck. In the absence of the requisite warning, the duck-and-cover position was to be assumed when we saw the blinding flash of an atomic-bomb explosion. I firmly believed that the duck-and-cover position would protect me from an atomic blast, but I knew the inanimate part of the world would surely be destroyed. After all, the purpose of duck-and-cover was to protect us from the flying pieces of objects broken by the blast. This seemed to be such an incredible waste. How could people work so hard to build things, only to see them destroyed? To me, making things that didn't break was one way around the destruction that nuclear war would bring.

The fear of pending nuclear annihilation may have seeded my interest in combating fracture, but the same fear also directed me down a path that would ultimately provide the tools necessary to achieve that goal. An axiom of the time was that "the power of the atomic bomb was unleashed by splitting the atom." This concerned me. If splitting a single atom were to cause an atomic explosion, was it possible that someone might inadvertently slice through one while using a knife or a pair of scissors? I pictured little mushroom clouds over thousands of dinner tables, each the result of an accident with a butter knife, but this never happened. Fortunately, the expected news story--"Today the John and Betty Smith family, their home, and the surrounding neighborhoods were demolished as John attempted to butter his bread"--never made the six-o'clock news. The only explanation for the absence of unintended nuclear blasts was that a butter knife was incapable of slicing through an atom. As a six-year-old, I began to construct a model that would explain this observation.

I envisioned the atoms of the butter as marbles spread out on the floor so that they just touched. Because everything was made from atoms, the edge of a knife could also be pictured as marbles, perhaps marbles of different sizes, peewees or boulders, but still marbles. The act of cutting the butter was like dragging the "knife" marbles through the other marbles on the floor. In my mind's eye, I picture holding a marble and pulling it through the marbles representing the butter. The knife would separate the marbles into two groups, but never would another marble be cut in half.

Though I slept easier knowing that making breakfast was unlikely to trigger Armageddon, a new question began to preoccupy me. There had to be something that held atoms together. If atoms were like marbles, they would just puddle out when taken out of their container. The knife was cutting not the marbles themselves, but whatever it was that held the atoms together.

I can't remember actually performing the marble experiment, and I doubt that I ever did; I valued my marbles too much to actually use them. Those of my friends who actually played the game had the most pitted and ugly marbles you could imagine. With only a few exceptions, my marbles remained as perfect as the day they were purchased. To me, a chipped one was worthless, having lost its value with its beauty. The exceptions were those marbles that were intentionally fractured to make them even more beautiful. The procedure is simple. Place a marble (a "cleary" is best; that's a marble made from a single piece of colored class, devoid of internal decoration) on a cookie sheet and heat in an oven to 250¡ F. Remove the marble when heated, and immediately drop it into cold water. Under these conditions, most marbles will respond by producing an array of internal fractures. The reflection of light from these internal surfaces produces an esthetically pleasing effect.

The problem with such marbles is that almost any blow will cause the cracks to run, leaving you with a pile of broken glass. They are useless from a utilitarian viewpoint; they can't even be carried in a marble bag for fear of shattering them. So, though I had come up with a method to preserve, and even extend, the beauty of my marbles, it was not a practical solution, since it required that they not be used. There had to be another way. Was it possible to make a glass marble that would not pit when used?

Having already developed an idea about what happens when something is cut, it took only a tiny step to picture what happened when something broke. Once again, I pictured the atoms of the glass as marbles packed together on the floor. This time a marble was shot at the pile, just as in the real game, dislodging other marbles from the central group. These dislodged marbles I thought of as the atoms of the broken chips of glass. If one wanted to make glass that would not chip, then whatever held the atoms of the glass together must be made stronger.

I still had no idea what held those atoms together. I had several small magnets, however, and I imagined the force holding the magnets together had to be similar to that holding atoms together. The problem with magnets, however, is their shape. Mine were horseshoe magnets and didn't look much like spherical atoms. Despite all my efforts, I could not seem to locate magnetic marbles. It appeared that my very first scientific investigation had come to a grinding halt at the ripe old age of six. Three years would pass before it could be revived.

In third-grade science class, we were observing magnetic fields by placing a sheet of paper over a magnet and then sprinkling iron filings on the paper. The purpose of the experiment was to observe how the filings lined up in the magnetic field. It was neat that something invisible could be made visible so easily. Even neater, however, was the fact that the iron filings became magnetic and attracted each other. Would little iron marbles behave the same way?

At the hardware store, they told me little iron marbles were called ball bearings and they came in many sizes. With my birthday money, I bought about a hundred BB-sized ball bearings and two bar magnets. At home, I set the bar magnets on end underneath a piece of cardboard and then poured the ball bearings on top. It worked exactly as it was supposed to; the ball bearings became magnetic and attracted each other. By gently tapping the cardboard, the bearings would arrange themselves in a periodic array. If the two magnets were set sufficiently far apart, two arrays could be made. Then, by dragging the magnets underneath the cardboard, the groups of bearings came together to form a single island. Depending on how the magnets were arranged (the north end up on one and the south end up on the other, or both magnets with the same end up), different results were obtained. Sometimes the groups of bearings would form a single array in which it was impossible to distinguish to which group a ball bearing originally belonged, and sometimes they would coalesce into a single group of bearings with an odd line that marked the boundary between the two. If the cardboard was gently vibrated, the boundary would disappear. By reversing the process, the island could be made to fall apart in two pieces. The boundary between the two islands of bearings looked different depending on how fast the magnets were pulled apart.

I played with my magnets and ball bearings for hours and discovered that by changing the strength of the magnet, the forces holding the ball bearings together could also be changed. This was accomplished by simply moving the magnet farther away from the cardboard. I made little spacers that fit between the magnet and the cardboard for this purpose. The larger the spacer, the weaker the bond. Using a strong magnet with no spacer, I would shape little wedges of ball bearings and ram them into the flat surfaces of oblong shapes, held together with a magnet separated from the cardboard by a large spacer. The oblong shape would deform and remain deformed when the wedge was withdrawn. On occasion, some of the bearings of the oblong were pulled away by the wedge.

After all the play, I was convinced that the different behaviors of ball-bearing atoms resulted from the strength of the forces that held them together. But I still did not know what held real atoms together. I was determined to find out.

Seven years later, in a high school chemistry class, I finally had my answer. They were chemical bonds. It turned out that the science of chemistry was concerned almost entirely with the study of these bonds--moving them, strengthening them, and so on. If you wanted to do something to a bond, you had to be a chemist, and that is exactly what I intended to become.

Though I now knew the things holding atoms together were called chemical bonds, actually understanding how those bonds worked would require considerable effort. Unlike baseballs, cars, and magnets, which respond to force according to the laws discovered by Newton, bonds respond in a very different way. So different and strange is their response that it was not until 1926 that the laws governing their behavior were discovered. Things that behave according to the laws of Newton are said to behave classically and obey the laws of classical mechanics. Bonds, however, obey the laws of quantum mechanics.

From the perspective of a high school student, the laws of quantum mechanics appear to make no sense. For example, those laws allow something to be in two places at the same time. Though this violates common sense, common sense is based on experience, and our experience is consistent with the laws of classical mechanics. Understanding quantum mechanics requires everyday experience to be set aside, and in its place one substitutes the mathematical expressions describing the new laws discovered in 1926 by Erwin Schrsdinger. Unfortunately, as a high school student I did not have the mathematical maturity necessary to understand quantum mechanics.

The desire to have my marbles and use them too had made the agenda clear. Study chemistry and learn how to manipulate bonds, study mathematics to understand quantum mechanics, and study quantum mechanics and learn how bonds worked. I elected to pursue this agenda at the University of Colorado in Boulder.

A student living in Boulder is faced with a number of distractions. Boulder is located at the base of the Rocky Mountains. Some of the most spectacular rock climbing in the world can be found just a few minutes from campus. A little longer drive away is world-class skiing. Of course, the ski season begins in December and generally ends in April, requiring skiers to find some other activity for the summer months. Whitewater kayaking was my summer activity. Chemistry and mathematics classes, skiing in the winter and spring, kayaking in the summer and fall, left little time to do much else, like get a job. Little did I suspect that my life as an unemployed student ski-and-kayak bum would transform me into a real expert on why things break.

As I studied chemistry, I constantly anticipated that the answer to why things broke was just around the corner. With the beginning of each semester came the same ritual. I would search through my newly purchased textbooks looking for some reference to fracture, some explanation. There were literally full chapters discussing the techniques for manipulating chemical bonds and transforming one molecule into another, but nothing about why those bonds unsurprisingly broke. The study of quantum mechanics was more involved with the interaction of molecules and solids with light than with mechanical forces. Though I never found a complete answer to my question, a good deal of what I learned seemed relevant to the problem of fracture. I filed this basic information away while I waited for the whole puzzle to come together.


From the Hardcover edition.

Présentation de l'éditeur

Did you know—

• It took more than an iceberg to sink the Titanic.
• The Challenger disaster was predicted.
• Unbreakable glass dinnerware had its origin in railroad lanterns.
• A football team cannot lose momentum.
• Mercury thermometers are prohibited on airplanes for a crucial reason.
• Kryptonite bicycle locks are easily broken.

“Things fall apart” is more than a poetic insight—it is a fundamental property of the physical world. Why Things Break explores the fascinating question of what holds things together (for a while), what breaks them apart, and why the answers have a direct bearing on our everyday lives.

When Mark Eberhart was growing up in the 1960s, he learned that splitting an atom leads to a terrible explosion—which prompted him to worry that when he cut into a stick of butter, he would inadvertently unleash a nuclear cataclysm. Years later, as a chemistry professor, he remembered this childhood fear when he began to ponder the fact that we know more about how to split an atom than we do about how a pane of glass breaks.

In Why Things Break, Eberhart leads us on a remarkable and entertaining exploration of all the cracks, clefts, fissures, and faults examined in the field of materials science and the many astonishing discoveries that have been made about everything from the explosion of the space shuttle Challenger to the crashing of your hard drive. Understanding why things break is crucial to modern life on every level, from personal safety to macroeconomics, but as Eberhart reveals here, it is also an area of cutting-edge science that is as provocative as it is illuminating.

“An engaging personal account not just of the physics and chemistry of materials but of the ethics, economics, and politics of innovation, with delightful bonuses on topics from the origins of ‘ghostly’ noises in old houses to the amazing coevolution of armor and armor-piercing projectiles. If it ain’t broke, Mark Eberhart can tell you why—and explain equally well why a shatterproof world remains beyond our reach.”
—Edward Tenner, author of Our Own Devices and Why Things Bite Back

“I don’t remember a book that has taught me so much, nor previously encountering a teacher like the marvelous Mark Eberhart, who in Why Things Break provides enlightening and thoroughly captivating scientific explanations of subjects ranging from the structural failures leading to the sinking of the Titanic to everyday, no-less-fascinating topics such as the reason why, even at the same temperature, winter days always seem so much colder in Boston than in Denver.”—Richard Restak, M.D., author of Mozart’s Brain and The Fighter Pilot

“Eberhart brings his insights to the reader by weaving personal anecdotes—from his childhood fear that cutting a stick of butter would release the energy of the atoms within to his arrival in Boston for an interview with MIT without a suitable winter coat—into a fascinating discussion of the forces that hold atoms and molecules together. A lively, unvarnished look at chemistry on the cutting edge.”
—Kirkus Reviews


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What incredible luck. Lire la première page
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Couverture | Copyright | Table des matières | Extrait | Index
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21 internautes sur 22 ont trouvé ce commentaire utile 
A fascinating compendia 21 avril 2004
Par Marissa Carter - Publié sur Amazon.com
Format: Relié
Why Things Break is one scientist's account of how he came to came to investigate the science of fracture mechanics at a molecular level--not really the how, but the why. Although the narrative is sometimes rambling, and Dr. Eberhart digresses considerably at tangents to make his points, the stories are well worth reading. It is also illustrative of the career of a scientist tackling a field that is new: full of obstacles to be overcome.
Particularly interesting--at least I found them so--are the stories of creating ever tougher and harder materials, from metal to ceramics, starting with ancient techniques thousands of years ago. If you've ever wondered how the Samurai made their swords, or how steel ultimately replaced bronze in the case of weapons, Eberhart's vignettes will delight you. The case study of Corning's Corelle line is especially instructive in demonstrating the pitfalls of trying to make commercially viable materials that don't break easily, and often one gets the impression this was a solution looking for a problem. Other fascinating examples include the sinking of the Titanic, the armor aboard the USAF's C141, and litigation involving the fracturing of a cast-iron pump.
Most of the science presented will be understandable to an arts major, although on occasion the chemistry might prove hard going--sometimes explanations in science can be tough! On pages 142-143, the author makes some errors: the WWII aircraft he cites--the Supermarine Spitfire and the Mitsubishi Zero--were not mostly made of wood; rather new aluminum alloys were used. Perhaps Erhard was thinking of the twin-engine DeHavilland Mosquito fighter-bomber.
My only criticism is that the real why of things breaking is really relegated to a couple of chapters at the end of the book, but possibly this is because still so little is known about the subject.
13 internautes sur 13 ont trouvé ce commentaire utile 
Excellent Read 11 janvier 2004
Par Un client - Publié sur Amazon.com
Format: Relié
I bought this book because it appeared to be aimed at showcasing the field of Fracture Mechanics to the lay person - certainly a daunting task in view of the depth of knowledge normally required to understand 'why things break". I wanted to see how the author would approach such a difficult subject (and without any pictures!). To my pleasant surprise this book was much more than an attempt to do "technology transfer". Eberhart has written a semi-autobiographical text that immerses the reader in the author's metamorphosis from a young child wondering about breaking atoms in butter with his knife to a full-fledged academic professor and researcher who asks and answers "why", not "how" or "when", but "why" something broke or failed. The examples given range from understanding how glass shatters, how Correlle ware is not really unbreakable, to the tragedy of the Challenger accident and the need to listen to engineers when they become wary about a material or system entering an unknown environment. Eberhart does lament the "pecking order" of science and the politically correct way that research funding in North America is meted out, but this, in my view, is an accurate reflection of how the approach our government agencies and industries are taking to funding fundamental research is leading our society towards mediocrity, inhibiting development of revolutionary ideas that can transform society into better ways to do things much quicker. While a conservative approach can provide a safer and lower risk result, it also can significantly slow the rate at which new ideas bubble to the surface. Research must be risk-taking by its very nature. We require a better understanding of "why" things happen if we really want to develop the new innovations that improve our lives and those of others around the world in need of appropriate technological support. Furthermore, the established "pecking-order" in research prevents certain problems from being viewed in contexts that differ from the "norm". Cross disciplinary teams are needed if we wish to find innovation in the conventional. There is much food for thought in this well-written and enjoyable book.
11 internautes sur 12 ont trouvé ce commentaire utile 
Starts strong ends just as strong 15 novembre 2003
Par "al_nest" - Publié sur Amazon.com
Format: Relié
I was attracted to this book after hearing the author on a radio interview and then reading the reviews on Amazon. I am not much of a science enthusiast, a little goes a long way, but I do like books about scientists. Both reader reviews seemed to indicate that "Why things break" is just that kind of book and it is. I so enjoyed following Dr. Eberhart's scientific development from a small child, concerned that cutting an atom would cause a nuclear explosion, to his eventual theories about bonds. Though some of this was over my head, I did feel as if I was participating in Dr. Eberhart's journey of discovery and learning a lot about materials on the way.
After reading the book, I felt as if I knew the Author and would enjoy having dinner with him.
6 internautes sur 6 ont trouvé ce commentaire utile 
A fun book to read 5 janvier 2006
Par Duwayne Anderson - Publié sur Amazon.com
Format: Broché
This book is the author's personal story of how he uncovered a (conceptually) simple explanation for the fracturing and shearing of materials, and metals in particular. As Eberhart puts it:

"When these angles [characteristic of the charge density around atoms in a material] vanished, the bonds resisting shear would break. So it also seemed reasonable that the smaller this angle, the more closely the charge density of the native metal resembled that of the deforming substance...[similarly] the competition between ductile and brittle behavior would boil down to comparing different angles. A ductile material would be one in which the angle that changed during shear was small compared to the changing angle during elongation." [Page 236]

Eberhart tells his story of discovery through the experience of his life, beginning with experiments he conducted with toys when only 6 years old. Along the way he illustrates the importance of material design by dissecting the cause of failure in some notorious historical examples, such as:

1) Aloha flight 243

2) The Titanic

3) Space shuttle Challenger

Aloha flight 243 was doomed by metal fatigue and crack propagation. The Titanic was doomed by, among other things, a captain who was sailing too fast in iceberg-infested waters, and because the steel used in Titanic had too much sulfur, causing the steel to be brittle in the cold Atlantic. Challenger was doomed by managers who overrode the technical advice of engineers who advised against launch, and by rubber O-rings that hadn't enough plasticity at the cold temperatures present at launch.

Eberhart does a nice job of placing material properties in a very broad historical context. He begins tens of thousands of years ago, describing how early hunters made stone tools by fracturing rocks. The story progresses through the development of metals, including bronze, iron, and steel. Along the way he gives interesting insight into how the characteristics of metals can be changed - sometimes dramatically - by the introduction of other atoms, and by how the material is worked.

Hardened steel, for example, is created by adding small amounts of carbon to iron (a soft metal in its pure state). Similarly, copper (also soft) is turned into bronze (harder) by alloying it with tin.

But why should the addition of atoms like carbon and tin make metals like iron and copper harder? Eberhart explains that the characteristics of materials (hardness, toughness, etc) result from the nature of the chemical bonds between atoms and the crystalline structure of the material. Metals are crystal conglomerates, with the various crystal grains oriented at different angles. Bending happens when planes of atoms slide past each other. When this happens dislocations in the crystals migrate. But these migrating dislocations are blocked at crystal boundaries because the planes of atoms are not aligned. Instead, the dislocations pile up at the boundaries, and when this happens the metal is no longer pliable (it's hard), and with increased force it doesn't bend, it breaks.

Material properties can be modified by treating in a way that limits the movement of dislocations. For example, cold-hammering bronze causes dislocations to pile up at grain boundaries, where they can no longer move easily. Steel consists of two types of crystals, Iron and carbide. Dislocations that can move easily in steel are blocked by carbide, so they pile up at the iron/carbide grain boundaries, making steel harder.

It's not always desirable to have hard materials; sometimes we want materials to bend without breaking. Here, too, dislocations play a part. Eberhart explains:

"When such a flaw [crack] is subjected to a load, sliding forces act on the atomic planes inclined to the crack, while tensile forces act on the parallel planes. To avoid fracture, dislocations must be able to move along the planes inclined to the crack. On the other hand, if dislocation motion is blocked, the planes parallel to the crack will come apart and the crack will run." [page 52]

The final chapter is an appeal to the government to do a better job of managing technology and science. Eberhart tells a particularly interesting story of how he went to Washington and tried to look up the Presidential Science Advisor. He looked and looked, but the Presidential Science Advisor wasn't in the phone book (this was in the early 1990s). Eberhart finds this symptomatic, especially since the grounds keeper of the White House was easily found.

I really enjoyed this book. It's interesting, informative, and easy to read. I managed to read it in less than a week, mostly while working out on my elliptical trainer. My only complaint is that the book has no figures. Having a few well-place figures would have been really welcome, particularly when reading the last few chapters dealing with the angles in chemical bonds.
16 internautes sur 20 ont trouvé ce commentaire utile 
A Well-Written Book on Materials Science 17 novembre 2003
Par Un client - Publié sur Amazon.com
Format: Relié
When I first browsed through this book, I hesitated buying it because, despite the fact that it's a science book, it contains no figures, no tables and no diagrams whatsoever. But since I had heard good comments about it, I bought it anyway. I'm very glad that I did! I learned a lot from it. The lack of figures is compensated for by the author's excellent ability to clearly describe what a figure would have illustrated. The analogies used are well selected and are most helpful; the reader gets a good idea of how materials behave under various conditions at the atomic/molecular level. On the negative side, however, there are a couple of problems. On page 130, it is pointed out that a moon loses angular velocity over time due to its collisions with particles in space such that a collision between the moon and the surface of the planet that it's orbiting will ultimately result. This is misleading because our moon is actually receding from the earth. The reason for this is well described in the book "The Big Splat" (by D. Mackenzie). Another problem is that on page 131, it is stated that the Newton (N) is a unit of momentum. This is incorrect. The Newton is a unit of force in the MKS system. Since momentum is mass multiplied by velocity, its units in the MKS system are kg-m/s. Since the Newton is a unit of force, its subunits are kg-m/s2. Thus momentum can be expressed in kg-m/s or in N-s. Anyway, despite these minor shortcomings, the book is excellent and, I believe, well worth the five stars that I have given it. I heartily recommend it.
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