need a diy strain gage 1

[qmechanics]

Hi,

Recently had an issue with a wear mark on the airframe on a helicopter. Thanks for all the help with that issue. It under control now. I'd like to put a strain gage on the airframe at the point of the wear mark just to make sure the applied forces are what I calculated them to be. I've done some searching on the web and found quite a bit on strain gages but am still a bit unsure how to proceed. Anyone know of an easy (not real expensive) way I can do this? thanks.

 

[swearingen]

Talk to a reputable vendor. The gages themselves are quite inexpensive, but collecting quality data can run up the cost quickly if you don't know what to do with the signal and have to resort to the fancy data interpretation that the vendor would like to sell you. Also, be careful when it is installed - they are very sensitive to initial conditions.



If you "heard" it on the internet, it's guilty until proven innocent. - DCS

 

[IRstuff]

The other big cost is the calibration thereof. Measuring "something" with a sensor is easy. Figuring out what the measurement is, isn't.

TTFN

FAQ731-376

 

[prost]

Don't know much about it myself, but last time I talked to a helicopter engineer (2006), he said there are many challenges to strain gaging a helicopter, that there is great difficulty in correlating strain gage measurements to structural calculations (like finite element analysis). I would guess that's because of the vibrations. Any thoughts from someone who has direct experience?

 

[Compositepro]

You can get strain gages, prices, and application info at

http://www.omega.com/prodinfo/StrainGages.html

Any piece of wire can be a strain gage but, mounting, calibration, and measurement of the value is the difficult/expensive part.

 

[qmechanics]

Thank you all for the info!

 

[rb1957]

the s/gauge is the easy part, next you have to worry about the data collection. We've used SoMat in the past, tho' there are many systems out there that are no doubt just as good.

 

[GregLocock]

What does a wear mark have to do with strain?



Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[rb1957]

i think he's just trying to measure the in-service stresses near (on?) the mark to see if there is a fatigue issue.

also, with a bunch of work you can calibrate the local stress to known inputs and develop a better sense as to what would happen at ultimate.