Strain gauge experience

[SKJ25POL]

Does anybody know for an element in tension only or say pure tension how many strain gages do I need on the element?
One, two, four???

Thank you

 

[SKJ25POL]

Also, I would like to know how many strain gauges we need for an element under pure TORSION?

 

[SWComposites]

What are going to use the strain data for?

 

[SKJ25POL]

SWComposites
Thanks for your question but does it matter where we are going to use the strain data???

 

[rb1957]

'cause it'll inform on what data to collect, and how.

another day in paradise, or is paradise one day closer ?

 

[chicopee]

Are you trying to compare the strain gauges results from the analytical results?

 

[FACS]

You only need one per element

 

[rb1957]

"You only need one per element" ... if you are Certain, absolutely Certain, that there are only pure loads (tension or torsion). But you need different gauges for the different loads ... a rosette (3 channels) will work for both loads, single channel axial will work for tension, shear can be detected with a shear gauge or a rosette.

another day in paradise, or is paradise one day closer ?

 

[BrianE22]

SWComposites
Thanks for your question but does it matter where we are going to use the strain data???

If it is strain you want you can get it with one gauge. If it is load you want you are better off with multiple gauges.

 

[EdStainless]

A single strain gage is likely to leave you needing more information.
There is no physical system that has pure tension, unless you are pulling on a rope.
I have worked on measuring the twist and bend on samples in a tensile test machine.
And it is far easier to collect more data the first time than to have to re-do the testing.


= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[IRstuff]

Too much data just costs you about 2.1 cents per GB:

https://www.costco.com/seagate-back...data-recovery-services.product.100458004.html

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[zeusfaber]

It's also easier to temperature-compensate one strain gauge with another one. When measuring what ought to be (but might not be) pure tension in a bar, I've tended to put two gauges on longitudinally - one on top top and one on the bottom of the bar, wired on opposite corners of the bridge, then make the rest of the bridge from another pair of gauges bonded across the bar (perpendicular to the expected strain).

A.

 

[rb1957]

yes that way you have the average load. temp compensation is usually (in my experience) on an unstrained scrap of similar metal.

but if you want to measure tension and/or torsion (like maybe different load cases) then ...
1) rosette if thin sheet metal (and torque is shear flow in the skin),
2) scatter gauges around the section if torsion is carried by differential cap loads.

we don't know what you're doing, why, or on what ... so suggestions needlessly general ...

another day in paradise, or is paradise one day closer ?

 

[Strong]

Plenty of information and strain gage products here:

https://micro-measurements.com/

Always something to learn!
Walt

 

[Andrew ONeill]

As above, technically only need 1, and I have done this in field works... but you making a big assumption that the load is in one direction only. Also I've only ever used 1 single guage when I have issues with equipment.

I'd definitely suggest a full rosette be used for each measurement location, and depending on what you're doing, it's a lot easier to go the load cell option, rather glue on strain gauges.



Andrew O'Neill
Specialist Mechanical Engineer
Rio Tinto
Australia