WHY DO THINGS BREAK.
Since my childhood I�ve always wondered why things break, and I always tried to mend them in the best possible way I can, but in vein, some how they broke again, I�ve been handling metallic objects since the age of 16 to date, during my mechanical apprenticeship at a local Auto Garage back home, I had too many questions to ask my tutor Mr. Vishnu V. Chari specially concerning defective parts etc, and he always made me understand that all things which are man made are meant to be broken since it has wear and tear, same as human being comes to life and dies as per God�s will� But later, after completing apprenticeship when I joined to do Automobile Engineering that�s when I learnt that Chemistry is responsible for wether solid shatters or bends.
For most people, it�s a tragedy when something breaks or bends, but for me this often is a highlight of my day. My interest in the way things break is not rooted in a preoccupation with destruction but rather in a knowledge that all technology is founded on wether materials fail in a brittle manner, like glass or in a ductile way, like iron.
In fact the history of technology is linked in a large part to the ability to exploit these 2 forms of failure. Manipulating brittle failure in minerals like flint launched human beings into our first technological era � The Stone Age, about 2.5 million years ago, the discovery of substances such as gold and copper, which resist brittle failure, led the way into the early metal age. Ancient artisans found these ductile metals good for making Jewelery and other Ornament�s because they are soft and can be easily stretched or pounded with a mallet. But although they are tough and absorb huge amount of energy they deform too, these materials have short lived, when fashioned for cutting and scraping. For building so many things from swords to skyscrapers, the optimum compound is both hard enough to hold its shape and not shatter, that is why metals have become ubiquitous in our culture. They are the only group of elements that display both brittle and ductile behaviour. Stone tools and weapons became obsolete, for example, as people learned that mixing copper with elements such as tin created a metal both harder and tougher: Bronze.
Even harder than bronze are alloys of Carbon and Iron, which eluded wide spread use until about 1000 B.C. When early metallurgists invented furnaces that burnt hot enough to extract the iron from its ore. Although they are hard, iron-carbon alloys can absorb little energy before fracturing. Early on metallurgists learned that blowing air through this compound reduced its Carbon contents, which made it more ductile and resulted in the worlds first steel. Ever since, technology has progressed hand in hand with the ability to design materials with varing degrees � of ductile and brittle behaviour.
Despite the ancient connection between technological progress and the way things break, it is only in this century that a scientific basis for understanding exactly why things break has surfaced. Even now, however, many of the details remain shrouded in microscopic complexities. For example, its not understood why three atoms of hydrogen per one million atoms of iron can make normally ductile steel dangerously brittle. A Scientific understanding of materials failure developed concurrently with the realization early this century that a solid is a collection of atoms held together by chemical bonds.
A problem confronted the new science of materials failure when researchers noted that even the highest strength materials fail at stress levels as little as one tenth those required to break chemical bonds. In the early 1920s A. A. Griffith showed that the strength of a material is not a direct consequence of the strength of its bonds but of weaknesses created by defects with its structure. These defects, or cracks, can be microscopic or visible to the naked eye, depending on how the material has been processed. Griffith realized that when stretching material perpendicularly above and below a crack, the bonds at the crack tip endure more elongation than the bonds elsewhere along the defect. When one bond is stretched beyond its breaking point, stress concentrates on the remaining bonds, which in turn break, and the crack tears open like a zipper, the result is brittle fracture.
Researchers such as Gregory B. Olson and his colleagues at Northwestern University�s Steel Research Groups. Olson organized the group in 1985 to engineer the tools needed to design ultra high strength steels by Computer. With computer programs designed by Arthur J. Freeman, also at Northwestern University, Olson and his Co-workers developed a way to determine the differences in charge density among similar materials. They calculated the charge density of a �virtual� alloy as two planes of atoms pull apart or slide past each other. Using that charge density, they determined how much energy is required to cause the fracture or slip. There are many other researchers, scientists, chemists and engineers who are yet trying to solve this equation specially in the field of aviation which causes major disaster.
In modern scientific and engineering techniques although to actually influence the alloy development of nickel aluminide, celebration is still in order. A theory for creating materials that behave just as they are intended could revolutionize the conventional trial and error searches that eat up billions of dollars and years of researcher�s time. A search has already begun for new alloys that are even lighter and stronger-and more capable of retaining these properties at even higher temperatures. These improved alloys will probably find uses in supersonic and hypersonic aircraft sometime after the year 2010. But the development program for these materials will proceed differently than all others in human history.
In the near future, rather than searching blindly for a base alloy with the ideal set of intrinsic properties, material designers will use computers to calculate the charge density of candidate base alloy. From this information they will determine how the charge density must be changed to produce desired properties and then make predictions as to which alloying elements will produce these changes. For the first time, a new alloy will be designed beginning with its electronic structure� I just wonder if they will christen the first airplane made from this alloy and give a safe travel to the world for the rest of our lives, lets all hope best for the future.
Sanny Vaz. Kuwait.
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