{"id":856,"date":"2013-01-15T09:25:42","date_gmt":"2013-01-15T14:25:42","guid":{"rendered":"https:\/\/engineering.jhu.edu\/magazine-archive\/?p=856"},"modified":"2017-07-28T10:04:22","modified_gmt":"2017-07-28T14:04:22","slug":"digital-defense","status":"publish","type":"post","link":"https:\/\/engineering.jhu.edu\/magazine-archive\/2013\/01\/digital-defense\/","title":{"rendered":"Digital Defense"},"content":{"rendered":"
\"digital-defense-01\"<\/a>
Illustration by John Weber<\/figcaption><\/figure>\n

Few modern structures are as ugly, ominous, or as seemingly vital as blast walls\u2014the steel-reinforced concrete barriers erected around buildings to protect them from things that go bang in our age of uncertainty.<\/p>\n

If you need a blast wall, how big should it be? How thick? The bigger and thicker the better, if your sole concern is stopping an explosion. But it turns out there is a price to be paid for what seems like perfect safety.<\/p>\n

\u201cIf you make them too big and too thick, you can\u2019t move them around, so you end up locking yourself in one place,\u201d says K.T. Ramesh<\/a>, director of the new Johns Hopkins Extreme Materials Institute (HEMI<\/a>) at the Whiting School of Engineering and the Alonzo G. Decker Jr. Professor of Science and Engineering. \u201cYou develop a bunker mentality because you built a bunker.\u201d<\/p>\n

Large, heavy blast walls don\u2019t just limit mobility. The bulkier they are, the more expensive they are to make, to move, and to tear down when they\u2019re no longer needed. The Iraqi government claims that the blast walls the U.S. built in Baghdad helped cause $1 billion in damage to the city\u2019s roads, sewers, and other infrastructure.<\/p>\n

[Should] a barrier break up into small pieces, large pieces, or not break up at all? If it should break up, how can it do it in a way that limits damage and injuries?<\/span><\/p><\/blockquote>\n

Neither are these monoliths necessarily the best defense against an attack because they can make it more difficult for those behind them to see trouble coming and stop it.<\/p>\n

Ramesh\u2019s institute is using an array of sophisticated new analytical and digital tools to study how materials behave in what are called \u201cextreme dynamic environments.\u201d He is just one of a number of Whiting School engineers who have worked with the Department of Defense searching for ways to make tougher, lighter metals, polymers, ceramics, and other materials.<\/p>\n

This basic research could lead not just to better blast walls but to more blast-resistant vehicles, buildings, and body armor.<\/p>\n

Throughout the history of warfare new weapons have always demanded better armor\u2014the stuff that absorbs and disperses the energy from an impact. Creating the stuff that other stuff is made of can be a slow process. The White House\u2019s 2011 Material Genome Initiative found that it typically took decades for new materials to go from the laboratory to the market.<\/p>\n

A major reason, the report said, was the traditional reliance on \u201cscientific intuition and trial-and-error experimentation\u201d in materials research. Instead, the report found, materials development and testing should move faster into computer simulations, where testing can be done in virtual space with faster, more powerful computers running sophisticated new software.<\/p>\n

The goal: to double the speed and cut the costs of discovering, developing, and deploying new high-tech materials needed to strengthen national security, energy security, human welfare, and industry. A number of Whiting School researchers are working toward that mark, with an emphasis on national security, under military grants for unclassified research.<\/p>\n

<\/p>\n\"digital-defense-02\"<\/a>\n

Concrete Security<\/h2>\n

Ramesh and his collaborators at other universities are looking at some of the basic issues raised by protective materials, including the concrete in blast walls. What\u2019s the best way to design these materials for the greatest safety and efficiency?<\/p>\n

Specifically they\u2019ve asked if a barrier, say, should break up into small pieces, large pieces, or not break up at all? If it should break up, how can it do it in a way that limits damage and injuries? \u201cThat\u2019s the fragmentation problem,\u201d Ramesh says.<\/p>\n

Engineers studying blast effects previously could study the behavior of only a few dozen of the largest pieces of a material hit by a bomb; the accompanying blizzard of rubble and dust, they assumed, could be treated like a cloud of debris rather than fragments. There were just too many things happening in a blast\u2014too fast at every scale, large and small, to identify and track.<\/p>\n

\u201cIn the past, we could never understand the little pieces,\u201d Ramesh says. \u201cWe couldn\u2019t track them. We couldn\u2019t see them. We couldn\u2019t calculate them. They were too small. So we had to ignore them.\u201d<\/p>\n

But now, advanced cameras can track something being blown to bits microsecond by microsecond, from the first instant of the explosion until the dust has settled. Microscopes can show the impact of a blast on a material at the scale of several atoms. And fast computers can model the physical forces of the blast and simulate its effects on different materials.<\/p>\n

The working assumption that the small pieces didn\u2019t matter was wrong. \u201cIt turns out the little pieces matter a great deal,\u201d Ramesh says. \u201cThe little things are where a lot of the action is.\u201d<\/p>\n

These fragments soak up a lot of the blast\u2019s energy, so they play a major role in limiting its reach. On the other hand, they account for many of the injuries in bombings, so blast walls can\u2019t be designed just to shatter into rubble. Ramesh\u2019s institute is working with labs at CalTech, Rutgers, and the University of Delaware to develop new computer models as part of a 10-year $90 million grant from the U.S. Army Research Laboratory.<\/p>\n

The aim is to subject new materials, which at first may exist only in cyberspace, to these environments and predict how they act. The result, they hope, will be some tough new stuff. Something as seemingly simple as a lighter, more efficient blast wall, Ramesh says, could make \u201ca huge difference.\u201d<\/p>\n

\u201cIn practical terms, it\u2019s the difference between saying you need a big concrete wall in front of your building and saying you need a smaller wall and a certain kind of glass in the windows,\u201d he says.<\/p>\n

While you may not be able to eliminate blast walls entirely, he says, you may be able to make them easier to live with.<\/p>\n

Visionary Defense<\/h2>\n

An improvised explosive device (IED) triggers a blast wave that travels at 1,600 feet per second\u2014 faster than the speed of sound\u2014and can shatter glass, splinter wood, and mangle steel. But its most precious and vulnerable target is the human body.<\/p>\n

An explosion can do terrible damage to all the body\u2019s tissues, including the eyes\u2014which are difficult to protect because we need to be able to see. A blast can pick up debris that will cut or puncture the eye. Soldiers hit by an IED can also suffer internal bleeding in their eyes, as well as damaged lenses and detached retinas.<\/p>\n

A blast can pick up debris that will cut or puncture the eye. Soldiers hit by an IED can also suffer internal bleeding in their eyes as well, as well as damaged lenses, and detached retinas.<\/span><\/p><\/blockquote>\n

\u201cWhat is not really known is what damage is caused just by that blast wave itself, not by fragments or being thrown by the blast,\u201d says Thao Nguyen<\/a>, assistant professor of mechanical engineering<\/a> at the Whiting School.<\/p>\n

So Nguyen, a member of Ramesh\u2019s HEMI team, is building a digital model of an eye inside a typical male head, and has started to test it using computer programs that simulate the pressure of an explosion hitting the skull from various angles.<\/p>\n

She\u2019s begun by measuring the effect of the blast on the eyeball. That\u2019s the tough external shell that protects the very delicate internal structures including the retina, lens, and choroid, the vascular layer of the eye.<\/p>\n

One of the first things she\u2019s looked at is how the anatomy of the face handles the pressure wave from a blast. \u201cHow does the blast wave scatter about the orbital features\u2014 your brow, and your nose ridge, your cheekbones? How do those facial features serve to either deflect or focus the blast wave onto the eye?\u201d asks Nguyen, who is working with a grant from the U.S. Army Medical Research and Materiel Command in Fort Detrick, Md.<\/p>\n

Some of her initial findings could help explain why 10 percent of injured soldiers have eye injuries, a much higher proportion than would be expected given the eyes\u2019 size relative to the body.<\/p>\n

It turns out that the design of the human face, which is good at deflecting blows from rocks and sticks, is lousy at protecting the eyes from a head-on blast wave. In fact, it can make things worse. \u201cWhat we find is that if the blast is directly in front of you, your brow and nasal ridge together act as a reflector, as a focuser, so it takes the incident pressure wave and it focuses onto the eye,\u201d she says. \u201cAnd the eye becomes the largest region of pressure on the face.\u201d<\/p>\n

But when a blast comes from below, facial features can offer partial protection.<\/p>\n

So far, Nguyen\u2019s computer model of the eye includes only the fluid-filled shell and external tissues\u2014the protective transparent cornea and the sclera, or white part of the eye. Her model does not include the delicate internal parts, including the retina, lens, and blood vessels.<\/p>\n

But her research suggests a blast wave fluid inside it, potentially causing injuries.<\/p>\n

Eventually, Nguyen and her team hope to test the military\u2019s protective eyewear to determine if it really protects the eyes or if, as has been suggested, the blast wave may bypass the lenses through a process called \u201cunderwash.\u201d<\/p>\n

They also plan to build a physical model of the head and subject it to real-life explosions, to double-check the reliability of their digital soldier.<\/p>\n

\u201cComputational models are great,\u201d she says. \u201cYou can make anything happen in a computer. But whether or not it reflects reality has to be validated.\u201d<\/p>\n

A higher proportion of gravely wounded in Iraq and Afghanistan are surviving than in previous wars, thanks to advanced armor and trauma medicine. Nguyen says she hopes her work will one day help develop better protective equipment, as well as new methods of diagnosis and treatment for those already injured.<\/p>\n

\u201cIf I can help surgeons understand, or help the designer of armor understand, how these mechanical loadings [from the blast wave] can effect injury, then that can go into directly helping the soldier,\u201d she says.<\/p>\n

<\/p>\n

The Search for Tougher Materials<\/h2>\n

Advances in the science of computational modeling of materials and structures have made it possible not just to redesign materials traditionally used in armor and other defense applications, but to develop new ones.<\/p>\n

That\u2019s one of the goals of Somnath Ghosh, director of the Whiting School\u2019s Computational Mechanics Research Laboratory and a leading member of the HEMI team. He develops state-of-the-art computer models to study the three-dimensional, multiscale effects of blast waves, including atom-by-atom responses of deformation, wear and tear, and impacts on structures made of crystalline and composite materials.<\/p>\n

Ghosh, the Michael G. Callas Professor of Civil Engineering, leads the new Hopkins Center of Excellence on Integrated Material Modeling, a $3 million U.S. Air Force program to develop lightweight, durable alloys for aircraft parts and turbine engines\u2014for use in everything from fighter aircraft to surveillance drones.<\/p>\n

His contribution to efforts to make new armor and other defense-oriented structures includes work on tantalum, a hard, blue-gray metal, as well as epoxy-glass composites.<\/p>\n

The goal is to systematically re-engineer materials that can provide protection against high impacts, such as a blast wave, with maximum efficiency. \u201cYou have to locally absorb the energy and disperse it as soon as possiblso you don\u2019t have massive damage,\u201d he says.<\/p>\n

The research could have broad applications. Ghosh, for example, is working with Los Alamos National Laboratories and Army Research Laboratory on developing models for armor capable of shielding vehicles and buildings against high-impact situations, such as blast effects in a nuclear explosion.<\/p>\n

\u201cWe want to know, what is the effect of an impact? How can we mitigate that? Is it even possible to do so?\u201d<\/p>\n

One key question, Ghosh says, is how candidate materials like tantalum fail when they reach the breaking point. The aim is to make sure that any new armor would respond in ways that would still protect whatever is behind it.<\/p>\n

Ghosh points to modern automobiles as other candidate applications of his research. Today\u2019s cars are designed to absorb and disperse the energy of a crash so the passenger compartment and people inside it are isolated from the shock. In a similar way, metal alloys can be designed to absorb and quickly disperse the energy from a projectile or a blast. \u201cThis energy absorption is a very important thing,\u201d he says.<\/p>\n

Another critical factor is weight. Heavy armor can slow people and vehicles down, making them more vulnerable to attack. One way to reduce the weight of armor is to use lighter materials.<\/p>\n

\"digital-defense-sidebar\"<\/a>

Tracking Submarines: Clues from Currents
Professor of Electrical and Computer Engineering Alex Kaplan’s research on ocean waves could lead to new forms of underwater sensing technology. more \u00bb<\/a><\/figcaption><\/figure>\n

Another way to lighten the load is to use multiple functionality in future materials. Take the next generation of defense aircraft. A desirable way to reduce the weight and profile of a warplane, Ghosh says, would be to blend communications antennae and sensors into other structural aircraft components.<\/p>\n

\u201cLet\u2019s say you have fuselage that behaves as an antenna, you don\u2019t have to carry additional equipment,\u201d he says.<\/p>\n

The next generation of tougher, lighter, more durable materials will have an impact far beyond military applications, Ghosh says. \u201cThese new generations of computational tools, together with high-resolution imaging tools, give us an opportunity to look far deeper than people could do before,\u201d he says. \u201cEngineering is being coupled with fundamental sciences through the use of high performance computing and computational science and that is causing a revolution.\u201d<\/p>\n

Controlling the Cracks<\/h2>\n

Modern aircraft\u2014both civilian and military\u2014 are made largely of aluminum alloys, which are prone to develop cracks that inexorably grow with repeated stress. And cracking can lead to catastrophic failures, like the one that hit Aloha Airlines Flight 243 in 1988, when the Boeing 737 lost part of its fuselage in flight.<\/p>\n

James Spicer, PhD \u201991<\/a>, a professor of materials science<\/a>, has conducted experimental studies for the Air Force on the internal structure of aluminum alloys. While he is not currently working with HEMI, Spicer\u2019s research has generated the kind of data computer scientists need to build their models.<\/p>\n

Specifically, he uses pulsed laser beams to set these parts vibrating like tuning forks, producing a kind of sonogram of their internal structure. The aim is to find hidden weaknesses.<\/p>\n

If cracked aircraft parts undergo repeated stress and aren’t repaired in time, they can rip apart in midflight\u2014a potentially disatrous turn of events.<\/span><\/p><\/blockquote>\n

Currently, he says, commercial airlines take aircraft out of service periodically to inspect them for cracks and metal fatigue. If they find rips or tears of sufficient size in the wrong places, they repair them. The military, with its specialized mission, takes a different tack. It simply swaps out old parts for new ones after a specified number of hours of service.<\/p>\n

Spicer says neither approach is very efficient. The military\u2019s practice of periodic replacement \u201cis very costly, because you could be throwing away a perfectly good part,\u201d he says.<\/p>\n

The commercial airlines\u2019 practice is not necessarily better, from the perspective of efficiency. \u201cTaking an aircraft out of service at regularly scheduled intervals might not make sense either because the aircraft could be in perfectly good shape,\u201d Spicer says.<\/p>\n

Spicer\u2019s work aimed at helping the Air Force develop ways to monitor the material \u201chealth\u201d of aircraft parts, including the fan blades on jet engines, and based on that finding, predict when they are likely to fail.<\/p>\n

Every time Spicer boards a commercial airliner, he says, he looks for cracks. All aircraft have some cracks, he says, though typically they aren\u2019t a problem.<\/p>\n

\u201cThe process of fatigue\u2014where you have, let\u2019s say, a crack in a material and you\u2019re loading it and the crack grows very slowly\u2014has been a problem that\u2019s been around for a long time,\u201d Spicer says.<\/p>\n

But if cracked aircraft parts undergo repeated stress and aren\u2019t repaired in time, they can rip apart in midflight\u2014a potentially disastrous turn of events.<\/p>\n

Spicer says one goal is to develop computer programs that, when fed data from a particular plane, can help spot cracked parts and predict how long they can safely be used.<\/p>\n

Such a computerized safety test might help repair crews decide if further tests are needed, or just when the plane should be brought in again for a checkup. This could make maintenance cheaper and flying safer.<\/p>\n

\u201cA lot of people have worked on it to try to understand this better,\u201d Spicer says. \u201cAnd with the advent of the computational side of things in materials science and engineering, that\u2019s provided new opportunities for doing a better job.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"

Using an array of sophisticated new analytical tools, Whiting School engineers are pushing to build better blast walls, buildings, and body armor.<\/p>\n","protected":false},"author":4,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[28],"tags":[],"class_list":["post-856","post","type-post","status-publish","format-standard","hentry","category-features","issue-winter-2013"],"acf":[],"yoast_head":"\nDigital Defense - JHU Engineering Magazine<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/engineering.jhu.edu\/magazine-archive\/2013\/01\/digital-defense\/\" \/>\n<link rel=\"next\" href=\"https:\/\/engineering.jhu.edu\/magazine-archive\/2013\/01\/digital-defense\/2\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Digital Defense - 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