Laboratory experiences in a mechanical and aerospace engineering department

Edward White, Aerospace Engineering, Texas A&M University, Instruction in Experimental Methods Session, AIAA ASM 2007

Laboratory experiences in a mechanical and aerospace engineering departmentEdward White - [email protected]

Aerospace Engineering, Texas A&M University

Until recently - Mechanical and Aerospace Eng.,

Case Western Reserve University


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

Edward White - [email protected]

Aerospace Engineering, Texas A&M University

Until recently - Mechanical and Aerospace Eng.,

Case Western Reserve University


Undergraduate lab instruction should produce competent producers and consumers of experimental results.


We who hire new grads need them to to start work or grad. school ready to make meaningful contributions.


How should we structure laboratory instruction to achieve this?

Maximum exposure?Stressing fundamentals?Something in between?(What about demos for other courses?)

There’s limited time, credit hours and attention. We can’t do it all.


The right balance prepares students to make meaningful contributions in the widest range of applications and roles over the span of their careers


To achieve this, we shouldstress thoughtful application ofkey principles, not maximum exposure to state-of-the-art instruments or rapid-fire labs


Why emphasize key principles over introduction state of the art?


Key principles have enduring value; the state of the art is ever changing.

So, use limited time and resources where they’ll have the best and broadest long-term impact.


Students’ capability to absorb and competently apply new concepts is limited.

Capture Efficiency Delivery Rate -(1+)


There’s limited time in lectures, lab sessions

Students have limited time(typically enrolled in 4-5 other courses)

I have limited time.


There’s limited time in lectures, lab sessions

Students have limited time(typically enrolled in 4-5 other courses)

I have limited time


The state of the art is expensive!


Why emphasize key principles over introduction state of the art?


Mastery of key principles is what’s required for creativity, design and technical leadership


What are the key principles?


(1) Every measurement is uncertain and the uncertainty must be understood and quantified


There’s subtlety and difficulty in making even simple measurements


There’s not a “right” answer on which to fall back (although one should have a pretty good guess before starting)


There’s almost always a variety of means of making a measurement


Instruments and techniques must be calibrated against known, reliable standards


(2) Instruments and techniques consist of “knowable” components that can be understood, critiqued, and improved upon by undergraduates.

There should be no black boxes.


Instruments consist of multiple simpler components


Computers do repetitive things quickly.

They don’t do things correctly (necessarily) they do things quickly.


(3) There’s nothing useful about knowing something if you can communicate it in a clear and convincing way


Ultimately, mastery of these key principles of experimental work comes through practice and application.

What do we actually do?


Perform a few “simple” labs that teach the key principles by requiring clear thinking about a tractable problems


Along the way we teach about data analysis and simple instrumentation as well as demonstrate physical principles to enhance other courses


Often

Solid Strain Basic UncertaintyMech. Gages Prop. Of Errors

Computerized DAQ

Heat TC’s Linear RegressionTrans.

Fluid Hot Fourier AnalysisMech. Wires


Example Lab

Measure the pressure in an unopened pop can.


Mayhem ensues.

Functional groups’ p’sRange from 15 to 100 psi.

All groups have different p’s 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.

What’s the result?


This is a simple experiment:Simply put some gages on a can and open it.

But, it’s actually a rich, complex (but tractable) problem that uncovers a huge range of real experimental issues.


This is the sort of foundation from which we should build.

Don’t underestimate the rigor that’s needed even for simple things

Understand and dissect the process

Understand uncertainty


Use this and a few other practice examples of similar scope, then move on to the more complex, more modern work.

Laboratory experiences in a mechanical and aerospace engineering department

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