Session D3: Materials Physics in the Fast Lane

The Art and Materials Physics of the Motorcycle

In 1871 Louis Guillaume Perreaux installed a compact steam engine in a commercial bicycle, and thus produced the world's first motorcycle. A steam engine was a logical choice, having steadily developed from the work of Savery and Newcomen in the 17th century to the point where Perreaux was able to make one small enough to use for this purpose. Unfortunately, it was a technological dead-end the moment it was created, since nine years earlier Alphonse Beau de Rochas had published the description of the four-cycle internal-combustion process. Significantly, the Michaux-Perreaux engine produced 1-2 hp in an overall machine that weighed 88 kg, whereas modern motorcycles produce 100 times more horsepower while weighing only twice as much. Examples I will show illustrate that developments in materials science over the past century are almost entirely responsible for making this possible. After a period of extraordinarily-rapid technological advance, by 1903 essentially all the components of a modern motorcycle were in place, and changes since then have been largely the result of evolutionary refinement in step with advances in materials science, rather than further revolutionary invention. Also, like many other objects of industrial design, motorcycles have played a variety of roles in society over the 137 years since the Michaux-Perreaux. I will discuss the interrelationship of the relevant technological, cultural, and aesthetic factors over the past century that have, amongst other things, resulted in standard production motorcycles -- incorporating such materials as carbon-fiber composites, maraging steels, and ``exotic'' alloys of magnesium, titanium and aluminum -- that can exceed 190 mph straight from the show room floor. For more information see http://www.optics.arizona.edu/ssd/aotm.html. Acknowledgment: I am grateful for the contributions of Ultan Guilfoyle to our joint work on the Solomon R. Guggenheim's ``The Art of the Motorcycle.''   

Materials at 200 mph: Making NASCAR Faster and Safer

You cannot win a NASCAR race without understanding science.\footnote{Diandra Leslie-Pelecky, \textit{The Physics of NASCAR} (Dutton, New York City, 2008).} Materials play important roles in improving performance, as well as ensuring safety. On the performance side, NASCAR limits the materials race car scientists and engineers can use to limit ownership costs. `Exotic metals' are not allowed, so controlling microstructure and nanostructure are important tools. Compacted Graphite Iron, a cast iron in which magnesium additions produce interlocking microscale graphite reinforcements, makes engine blocks stronger and lighter. NASCAR's new car design employs a composite called Tegris$^{TM}$ that has 70 percent of the strength of carbon fiber composites at about 10 percent of the cost. The most important role of materials in racing is safety. Drivers wear firesuits made of polymers that carbonize (providing thermal protection) and expand (reducing oxygen access) when heated. Catalytic materials originally developed for space-based CO$_{2}$ lasers filter air for drivers during races. Although materials help cars go fast, they also help cars slow down safely---important because the kinetic energy of a race car going 180 mph is nine times greater than that of a passenger car going 60 mph. Energy-absorbing foams in the cars and on the tracks control energy dissipation during accidents. To say that most NASCAR fans (and there are estimated to be 75 million of them) are passionate about their sport is an understatement. NASCAR fans understand that science and engineering are integral to keeping their drivers safe and helping their teams win. Their passion for racing gives us a great opportunity to share our passion for science with them. NASCAR$^{\mbox{{\textregistered}}}$ is a registered trademark of the National Association for Stock Car Auto Racing, Inc. Tegris$^{TM}$ is a trademark of Milliken {\&} Company.   

Sox and Drugs: Baseball, Steroids and Physics

The sports world is in an uproar over performance-enhancing drugs. In the United States steroids in baseball have received the most attention, in part because the purported effects are much more dramatic than in any other sport. From 1995-2003 a few players hit home runs at rates 20-50{\%} higher than the best sluggers of the preceding century. Could steroids really increase home-run performance that much? I will describe a model that combines estimates of the physiological effects of steroids, known baseball physics, and reasonable models of batting effectiveness for highly skilled hitters. A 10{\%} increase in muscle mass, which can reasonably be expected from steroid use, increases the speed of a batted ball by 3{\%}. Because home runs are relatively rare events on the tail of a batter's range distribution, even this modest change in ball speed can increase the proportion of batted balls that result in home runs by 30 -- 70{\%}, enough to account for the record-shattering performances of the recent past. I will also describe some of the attention -- both welcome and not -- that comes to the unsuspecting physicist who wades into such emotionally troubled waters.   

Zero CTE Glass in the Hubble Space Telescope

Orbiting high above the turbulence of the earth's atmosphere, the Hubble Space Telescope (HST) has provided breathtaking views of astronomical objects never before seen in such detail. The steady diffraction-limited images allow this medium-size telescope to reach faint galaxies fainter than 30th stellar magnitude. Some of these galaxies are seen as early as 2 billion years after the Big Bang in a 13.7 billion year old universe. Up until recently, astronomers assumed that all of the laws of physics and astronomy applied back then as they do today. Now, using the discovery that certain supernovae are ``standard candles,'' astronomers have found that the universe is expanding faster today than it was back then: the universe is accelerating in its expansion. The Hubble Space Telescope is a two-mirror Ritchey-Chr\'etien telescope of 2.4m aperture in low earth orbit. The mirrors are made of Ultra Low Expansion (ULE) glass by Corning Glass Works. This material allows rapid figuring and outstanding performance in space astronomy applications. The paper describes how the primary mirror was mis-figured in manufacturing and later corrected in orbit. Outstanding astronomical images taken over the last 17 years show how the application of this new technology has advanced our knowledge of the universe. Not only has the acceleration of the expansion been discovered, the excellent imaging capability of HST has allowed gravitational lensing to become a tool to study the distribution of dark matter and dark energy in distant clusters of galaxies. The HST has touched practically every field of astronomy enabling astronomers to solve many long-standing puzzles. It will be a long time until the end of the universe when the density is near zero and all of the stars have long since evaporated. It is remarkable that humankind has found the technology and developed the ability to interpret the measurements in order to understand this dramatic age we live in.   

The Materials Science of Superheroes

While materials scientists don't typically consult comic books when selecting research topics, innovations first introduced in superhero adventures as fiction can sometimes find their way off the comic book page and into reality. As amazing as the Fantastic Four's powers is the fact that their costumes are undamaged when the Human Torch flames on or Mr. Fantastic stretches his elastic body. In shape memory materials, an external force or torque induces a structural change that is reversed upon warming. Smart fabrics used in hiking clothing expand at low temperatures, while other materials increase their porosity at higher temperatures, allowing body heat and water vapor to escape. Some polymers can be stretched to over twice their normal dimensions and return to their original state when annealed, a feature appreciated by Mr. Fantastic. In order to keep track of the Invisible Woman, the Fantastic Four's arch nemesis Dr. Doom employed sensors in the eye-slits of his armored face-plate, using the same physics underlying night vision goggles. Certain forms of blindness may be treated using an artificial retina consisting of silicon microelectrode arrays, surgically attached to the back of the eye, that transmit a voltage to the optic nerve proportional to the incident visible light intensity (one of the few positive applications of Dr. Doom's scheming). Spider-Man's wall crawling ability has been ascribed to the same van der Waals attractive force that gecko lizards employ through the millions of microscopic hairs on their toes. Scientists have recently developed ``gecko tape,'' consisting of arrays of fibers that provide a strong enough attraction to support a modest weight. Before this tape is able to support a person, however, major materials constraints must be overcome (if this product ever becomes commercially available, I for one will never wait for the elevator again!) All this, and the chemical composition of Captain America's shield, will be discussed.