Laboratory experiences in a mechanical and aerospace engineering department

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Laboratory experiences in a mechanical and
aerospace engineering department

• Edward White - ebw_at_aeromail.tamu.edu
• Aerospace Engineering, Texas AM University
• Until recently - Mechanical and Aerospace
  Eng., Case Western Reserve University

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What to do (and what canbe done) in
undergraduatelab courses

• Edward White - ebw_at_aeromail.tamu.edu
• Aerospace Engineering, Texas AM University
• Until recently - Mechanical and Aerospace
  Eng., Case Western Reserve University

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Undergraduate lab instruction should produce
competent producers and consumers of experimental
results.
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We who hire new grads need them to to start work
or grad. school ready to make meaningful
contributions.
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How should we structure laboratory instruction to
achieve this?Maximum exposure?Stressing
fundamentals?Something in between?(What about
demos for other courses?)Theres limited time,
credit hours and attention. We cant do it all.
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The right balance prepares students to make
meaningful contributions in the widest range of
applications and roles over the span of their
careers
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To achieve this, we shouldstress thoughtful
application ofkey principles, not maximum
exposure to state-of-the-art instruments or
rapid-fire labs
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Why emphasize key principles over introduction
state of the art?
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Key principles have enduring value the state of
the art is ever changing.So, use limited time
and resources where theyll have the best and
broadest long-term impact.
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Students capability to absorb and competently
apply new concepts is limited.
Capture Efficiency ? Delivery Rate -(1?)
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Theres limited time in lectures, lab
sessionsStudents have limited time(typically
enrolled in 4-5 other courses)I have limited
time.
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Theres limited time in lectures, lab
sessionsStudents have limited time(typically
enrolled in 4-5 other courses)I have limited
time.
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Theres limited time in lectures, lab
sessionsStudents have limited time(typically
enrolled in 4-5 other courses)I have limited
time
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The state of the art is expensive!
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Why emphasize key principles over introduction
state of the art?
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Mastery of key principles is whats required for
creativity, design and technical leadership
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What are the key principles?
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(1) Every measurement is uncertain and the
uncertainty must be understood and quantified
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Theres subtlety and difficulty in making even
simple measurements
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Theres not a right answer on which to fall
back (although one should have a pretty good
guess before starting)
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Theres almost always a variety of means of
making a measurement
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Instruments and techniques must be calibrated
against known, reliable standards
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What are the key principles?
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(2) Instruments and techniques consist of
knowable components that can be understood,
critiqued, and improved upon by
undergraduates.There should be no black boxes.
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Instruments consist of multiple simpler components
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Computers do repetitive things quickly.They
dont do things correctly (necessarily) they do
things quickly.
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What are the key principles?
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(3) Theres nothing useful about knowing
something if you can communicate it in a clear
and convincing way
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Ultimately, mastery of these key principles of
experimental work comes through practice and
application.What do we actually do?
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Perform a few simple labs that teach the key
principles by requiring clear thinking about a
tractable problems
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Along the way we teach about data analysis and
simple instrumentation as well as demonstrate
physical principles to enhance other courses
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OftenSolid Strain Basic UncertaintyMech. Gages
Prop. Of Errors Computerized
DAQHeat TCs Linear RegressionTrans.Fluid Ho
t Fourier AnalysisMech. Wires
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Example LabMeasure the pressure in an unopened
pop can.
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Whats the result?
Mayhem ensues. Functional groups ps Range from
15 to 100 psi. All groups have different ps for
the axial and circumferential gages. Some groups
have a gage break, need to improvise. All have
definite opinions about whether this is a good
way to measure pressure! Most groups are able to
make interesting conclusions about what went
right and what went wrong.
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This is a simple experimentSimply put some
gages on a can and open it.But, its actually a
rich, complex (but tractable) problem that
uncovers a huge range of real experimental issues.
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This is the sort of foundation from which we
should build.Dont underestimate the rigor
thats needed even for simple thingsUnderstand
and dissect the processUnderstand uncertainty
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Use this and a few other practice examples of
similar scope, then move on to the more complex,
more modern work.