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Vol. 1 No. 2 February 2007 |
Technovations in Transportation
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It is no secret that airbags save lives: Over
15,000 lives, in fact, airbags were first installed
in the Oldsmobile Toronado in 1972. Airbags, also
known as Supplemental Restraint Systems, are
flexible, rapidly-inflating envelopes that are used
for cushioning when the vehicle in which they are
installed is involved in a collision. Deployment
occurs when crash sensors on the front and sides of
a vehicle are activated, sending a signal to the
airbag’s inflator--the device which generates the
gas required to inflate the airbag cushion.
The inflator contains a small electro-explosive
device sealed within a glass and metal enclosure. This pyrotechnic
initiator is responsible for starting the
gas-generating chemical reactions within the
inflator. During a collision, an electric current
within the inflator heats the bridgewire (often
made from a platinum alloy), which in turn, ignites
pyrotechnic (combustible) material. This
electro-explosion heats stored gases, or actuates
flow control mechanisms, which cause the airbag to
inflate.
Successful airbag deployment depends on these
pyrotechnic initiators, which are roughly the size
of a thumbnail. If the initiator and airbag are
functioning properly, gas begins to flow into the
airbag about 1 millisecond after the collision is
detected. Depending on the type of airbag, the
cushion is fully deployed between 10 and 40
milliseconds later.
Automobile owners expect that airbags, unless
deployed, will remain fully-operational for the life
of their vehicles. However, defects, such as cracks
in the insulating glass could potentially allow
moisture to penetrate the device, possibly corroding
the critically important internal electrical
components or leading to degradation the pyrotechnic
material, thereby resulting in improper operation of
the device. Cracks and other flaws have been
detected in some units (see photograph to right), and it is suspected that the
source of some of these flaws may be thermal
stresses incurred during manufacturing.
Dr. Karl Rink, associate professor of Mechanical
Engineering at the University of Idaho, along with
graduate students Dan Gunter, Andrew DuBuisson, Mike
Klein, Luke Thompson, Chris Fischer, and Mike
Maughan, set out to determine when cracks occur
during the manufacturing process and to compare
these results to cracks observed in pyrotechnic
initiators currently in use. They have also used
advanced test methodologies and analysis to predict
how quickly debilitating moisture may penetrate into
an initiator. In addition, they have developed a
unique laboratory where they can measure the
degradation in performance caused by the presence of
moisture within initiators.
Analysis of Thermal Stresses
Dr. Rink, along with colleagues Dr. Don
Blackketter and Dr. Robert Stephens, analyzed two
methods that can be used to manufacture
initiators. In one method, components are
assembled at room temperature. The initiator is then
heated in a furnace until the glass melts to produce
a seal and cooled back to room temperature. In the second method, not directly applicable to
current production methods, molten glass is used to
form the seal.
Using computer analytical programs to
solve mathematical models, the research team
evaluated the affect of a wide range of temperatures
on the initiator during its manufacture, studying
how thermal stress affects glass strength. They
determined that if the initiator is uniformly cooled
(both on the surface and in the interior), tensile
stresses, but not cracks, may occur. These findings
agreed with photographic evidence obtained through
study of actual initiators.
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[Accurate leak testing]
is important for the industry to ensure
the reliability of [airbag initiators].
Karl Rink is one of the few people who
have studied these effects and have
published their results. [Because of
Rink’s work] there is now movement to
change the relevant military standards
to a more reliable method of performing
the measurements.
Barry T Neyer, Ph.D.
US Military Aerospace Engineering Leader
PerkinElmer Optoelectronics |
Evaluating the Propensity for Leaks in
Pyrotechnic Initiators
To ensure moisture won’t penetrate these devices,
manufacturers use tracer gas leak detection methods
in an attempt to verify their hermetic integrity. A
complication with these methods is that there is
essentially no internal volume available for the
introduction and accumulation of tracer gases within
an initiator. Dr. Rink and his research team sought
to expand knowledge of this under-appreciated effect
using a krypton-85 radioisotope containing gas as a
tracer. Using a special machine called a Radiflo®
leak detection apparatus, they recorded the rate of
flow
of krypton-85 from specially-prepared, small
cavity devices with volumes similar in size to those
found in pyrotechnic initiators. Their experimental
results compared favorably with well-established
fluid flow models and provided further confirmation
as to why cracks in the glass seals of initiators
are occasionally found to escape detection by
conventional methods.
Continuing Research
Dr. Rink’s work with pyrotechnic initiators is of
interest to more than those in the automotive
industry. The United States military and aerospace
manufacturers also use these devices for ejection
seats and pin-pullers, for example.
Because of their importance, Dr. Rink and research
team are seeking to further characterize where and
why the insulating glass cracks; to determine how
quickly moisture may enter these devices and how
long it takes before the moisture causes the devices
to fail; and, ultimately, to develop an engineering
basis for leak rate specifications for pyrotechnic
initiators. |
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Dr. Karl Rink received his BS in Aerospace Engineering and Mechanics
from the University of Minnesota in 1983 and his MS from
Purdue University in 1986. Rink
was named an Outstanding Mechanical Engineer by Purdue
University in the year 2000. After several years working as a senior design engineer at Solar Turbines
Incorporated, Rink returned to academia and earned his PhD in Mechanical
Engineering in 1994 from the University of Utah,
specializing in the thermal remediation of hazardous
materials.
Subsequently, Rink worked for Autoliv, where he was responsible for the
development of innovative gaseous, liquid and hybrid
airbag inflation technologies. His work in airbag technology led to 50 U.S.
patents, one of which earned his employer the
internationally-recognized 2000 PACE award.
Rink remains active in a number of technical
societies including the Combustion Institute, the
American Society of Mechanical Engineers (ASME), and the
American Institute of Aeronautics and Astronautics (AIAA),
for which he serves as Vice-Chair of the Technical
Committee on Energetic Systems and Components.
In his spare time, Karl
enjoys playing and coaching hockey (some of his original
teeth remain intact) and riding horses with his wife
Linda. |
Chris Fischer (right) received his BS in
mechanical
engineering at the University of Idaho in 2002.
Following graduation, he worked at Autoliv ASP, the
worlds leading manufacturer of automotive airbags.
Chris returned to UI in the fall of 2005 to work
towards his MS under the guidance of Dr. Karl Rink.
Chris comes from Twin Falls, ID.Dan Gunter (MSME '02) lives in Redondo Beach,
California and works for The Aerospace Corporation
where he performs
analytical work on launch vehicle ordnance systems.
Dan grew up in Park
City, Utah, and likes to spend his free time skiing,
snowboarding, running, biking, cooking, traveling,
or reading.
Andrew DuBuisson (MSME '02) currently works
for Freeman Marine Equipment in Gold Beach, Oregon,
as a contract design engineer. Andrew grew up in Coeur
d’Alene, Idaho, and enjoys playing ultimate Frisbee.
Michael Klein (MSME
'02) works as a design and stress analyst on
Boeing's 787 airplane’s landing gear. Between
graduation and accepting his job at Boeing, Mike
spent 7 months in New Zealand on a work-abroad
program and in Boise, Idaho, where he helped the UI
Boise campus outfit their engineering machine shop.
Since moving to Seattle, he has taken up
mountaineering and has had great opportunities to
experience the inclement weather of the Cascades as
well as some grand vistas of their summits.
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Publications
Rink, K. K.,
"Fundamental Considerations Concerning the Detection
of Gross Leaks in Bridge-Wire Initiators,"
International Journal of Vehicle Safety Vol. 1,
No. 4, pp. 253-266, 2006.
Rink, K. K., "Failure Mode Investigations Related
to Non-Hermetic Behavior in Bridge Wire Initiators,"
proceedings of the 5th Cartridge-Propellant Actuated
Device Technical Exchange Workshop, Naval Surface
Warfare Center, Indian Head, Maryland, 2004.
Thompson, L. M., Thermal Stresses in Airbag
Initiators, MS Thesis, University of Idaho, 2005.
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This research is essential to establish more
stringent quality control for potentially
life-saving applications. By identifying
leak paths and quantifying leak rates, we
can more consistently be able to remove
ineffective initiators from the market and
more effectively determine the life of an
initiator ensuring reliable deployment of
airbags. Michael
K. Klein, MS '02 |
Rink, K., Failure Mode Investigation and Ballistic
Performance Characterization of Pyrotechnic Initiators
Used in Automotive Supplemental Restraint Inflation
Systems, NIATT Report
N06-04.
Rink, K., Thermal Stresses in Pyrotechnic Initiators
Used in Automotive Supplemental Restrain Systems, NIATT
Report
N06-05.
Funding
Funding for this project came from the US Department
of Transportation Research and Innovative Technology
Administration Grant No. DTRS98-G-0027. |
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Engineering students won top honors at the
Traffic Bowl last month, beating out teams from
Washington, Portland and Oregon State Universities
and the University of Oregon. The annual Traffic
Bowl is a Jeopardy-style competition organized by
the Northwest section of the Institute of
Transportation Engineers (ITE).
The students, members of the ITE student chapter
and undergraduate civil engineers, took home a
trophy and cash prize. Competing were Dennis Ownbey,
Kimberly Baird, and Nicholas Taylor, chapter
president (shown in photo, left to right, with Chris
Teisler of Kittelson & Associates, a sponsor of the
competition).
All three UI contestants contributed to the win.
UI took the lead first when Nick Taylor, president
of the chapter, correctly answered several questions
about the “Green Book,” the AASHTO highway design
manual. Dennis Ownbey has worked with Dr. Michael
Dixon, chapter advisor, on roundabouts, so he was
able to help the team keep the lead by correctly
answering most of the questions in the round that
focused on roundabouts. Freshman Baird answered a
question about colors of highway striping. The team
held their lead with strategic betting in the final
round in which no team had the correct question to
the answer, “The 13 states through which I-90
passes, east to west or west to east.”
The student chapter meets regularly and will
begin planning their annual field trip, where they
meet with transportation professionals and take
several tours. Past trips have been to Washington,
DC, Las Vegas, and Portland.
“University of Idaho engineering students’
performance in the traffic bowl is a great example
of how our transportation engineering students stack
up against students from other universities
throughout the Northwest,” said Dean Aicha Elshabini.
ITE is a professional society of transportation
engineers, planners and other professionals in more
than 70 countries. The goal of the Idaho student
chapter is to introduce students to the
transportation profession and supplement their
classroom and laboratory experiences. |
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The traffic signal is one of the most important
devices in the nation's transportation system. In
January 2004, FHWA proposed a multiyear roadmap for
a new traffic signal timing program that is designed
to reduce congestion and improve flow and safety by
providing dramatic and sustained improvements in
traffic signal operations throughout the US.
NIATT's Traffic Signal Summer Workshop offers
hands-on-training for future transportation
engineers in the operations of traffic signal
systems. This training has already been experienced
by 72 participants from 33 universities, DOTs and
FHWA. You, too, can prepare yourself to gain the
skills and competencies needed to prepare yourself
for a career in transportation engineering.
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The workshop was extremely useful in
learning the concepts of traffic signal
design, timing, controller operation,
and detection. The hands-on environment
is truly unique and provides an
excellent method of teaching all aspects
of traffic signals. I would recommend
this course to any student with an
interest in traffic signals. Gene McHale, FHWA |
Spend one week on the University of Idaho campus
(August 5-10, 2007) working with industry
professionals, using the latest traffic signal
systems equipment and software. Applications are
being accepted until June 4, 2007.
Apply now for one of the 12 spots open. |
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Given the increased complexity of surface transportation
systems--and increasing physical and electronic threats
against those systems--it is imperative that an
Intelligent Transportation System be designed not only
for safety and efficiency, but also for survivability. A
team of researchers at NIATT led by Drs. Paul Oman,
Ahmed-Abdel-Rahim, and Brian Johnson, successfully
modeled the criticality of traffic system components in
a small urban ITS system (Moscow, ID), and a large
metropolitan area (Boise, ID). This work followed an
initial study that used a Security/Survivability Systems
(S/SSA) to formalize "softspot" analysis of
traffic/transportation control networks, including
identifying essential services and intrusion scenarios.
Abdel-Rahim will present a paper resulting from this
work, "Survivability Analysis of Large-Scale Intelligent
Transportation System Network," at the 86th Annual
Transportation Research Board Meeting in Washington, DC.
This research was funded in part by the US Department of
Transportation Research and Innovative Technology
Administration Grant No. DTRS98-G-0027.
The research team's
current project involves defining and developing a
computational framework to identify and prioritize
critical components in surface transportation networks
to allow engineers, management and emergency planners to
allocate funds to improve the survivability of a system.
Use the
research database on NIATT's website to read our
most recent research reports. Among them is the final
report for the University Transportation Centers
Grant-supported project, "Applying
Safety-Critical Fault Tolerant Principles to Survivable
Transportation Control Networks," authored by Paul
Oman and Axel Krings. |
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 A
select number of students who wish to pursue MS
degrees in transportation engineering at the
University of Idaho will receive fellowships for the
2007-2008 academic year.
Recipients will receive a stipend of $27,500 for
the year (with all student fees also paid) to work
on challenging transportation problems with top
researchers. Earn your MS degree in a field
offering ever-increasing job opportunities in both
the private and public sector. Applications,
available
online, are due no later than May 1, 2007. |
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Between Dr. Oman, Dr. Abdel-Rahim, Dr. Johnson
and the many great students with whom I had the
privilege of working at NIATT, I couldn't have
hand-picked a better group. The professors are not
only experts in their chosen fields, but were the
perfect fit for me personally. Someone had to keep
me focused and out of trouble, and provide some
wisdom from personal experience that every graduate
student needs . . .To this end they provided more
than I ever could have asked.
 The
professors represent three disciplines--computer
science, civil engineering, and electrical
engineering--at the highest level. They contributed
a variety of perspectives to our research, and it
was this interaction among various backgrounds that
led to our most significant achievement in
transportation survivability research: multilayered
analysis that considers interaction among components
in multiple infrastructures--communications, power,
and transportation--on common ground in simple terms
based on service to users. Thankfully, their diverse
backgrounds rubbed off a little on me. I was happy
to contribute to NIATT with my computer security
knowledge, and pick up some pointers in power and
transportation along the way!
When you think about it, though, this is a
microcosm of the future of transportation.
Transportation systems, while traditionally a matter
for civil engineers, continue to incorporate
knowledge from a wide variety of disciplines, from
recognized backgrounds like mechanical and materials
engineering, to the aforementioned computer science
and electrical engineering, to even more exotic
disciplines like economics, psychology, and law.
Mechanical and materials engineers will continue to
play a prominent role by developing vehicle designs
that become increasingly less reliant on gasoline
and incorporate renewable resources.
Computer scientists will contribute to the secure
communications networks that will become ever more
prolific in future transportation systems as it
evolves into a system based on user- and
vehicle-infrastructure integration, and to the
secure embedded systems design that is necessary for
vehicles to safely incorporate more advanced, even
automated, technologies. Electrical engineers will
continue to improve electric and hybrid vehicle
design and provide improved energy service to the
transportation infrastructure. Economists will
contribute ideas for how the vehicular
communications infrastructure can be utilized in
electronic tolling systems and commercial endeavors,
and even in the development of a
vehicle-infrastructure information economy.
Psychologists will continue to improve human-vehicle
interaction and research the role of trust as more
automated transportation technologies are
introduced, taking much of the control away from
drivers. (Notice I'm not justifying law...this is
already taking too long.) And civil engineers will
play as crucial a role as ever, as they develop safe
roads and structures that can not only sustain
increased traffic, but the infrastructural
mechanisms alongside (and perhaps even embedded in)
the roads to support communications among that
traffic.
When Dr. Abdel-Rahim told me eight months after I
graduated that I had been named NIATT
Student-of-the-year, I thought it necessary to
remind him that not only was I no longer a NIATT
student, but I was not even a NIATT student at any
point during 2006! When he explained that overall
multidisciplinary contributions over the last two
years were considered for the award, I finally
understood. I am humbled to even be considered among
those students that continue to make amazing
contributions to transportation safety, sustainable
transportation, smart pedestrian signals,
human-vehicle interaction . . . the list goes on.
But advanced transportation is a truly
multidisciplinary endeavor, and its continued
success relies on the enormous diversity of its
contributors. In accepting the award on behalf of
all the other students in these various disciplines
with whom I worked, I'm proud to represent the
potential that computer science brings to the
transportation industry, and hope people of all
backgrounds see copious opportunities to contribute
their own unique ideas.
Matt received his MS in computer science in 2005.
Read more about Matt and past students-of-the-year |
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