Crack monitoring strain gauge for fatigue
Crack monitoring strain gauge for fatigue
(OP)
Hi all, hope I am posting in the right place.
I will be conducting some load control fatigue test on my compact tension sample. I have done these test before and successfully monitored the crack with a CMOD clip gauge. But this time I am running at low load and a paper that I found said that the force of the clip gauge will affect the crack growth and suggested to use back face strain gauge to measure the crack length. I am very new to this back face strain gauge thing and I have no idea how to select the right gauge. I have been looking through micro-measurement website (http://www.vishaypg.com/micro-measurements/), and there seems to be two main types of strain gauges, stress analysis strain gauge and transducer gauge. I wonder what is the different between these two types and for my purpose, which type do I need? (Sorry if this is a stupid question, but I had searched online but can't seems to find the answer)
I will be conducting some load control fatigue test on my compact tension sample. I have done these test before and successfully monitored the crack with a CMOD clip gauge. But this time I am running at low load and a paper that I found said that the force of the clip gauge will affect the crack growth and suggested to use back face strain gauge to measure the crack length. I am very new to this back face strain gauge thing and I have no idea how to select the right gauge. I have been looking through micro-measurement website (http://www.vishaypg.com/micro-measurements/), and there seems to be two main types of strain gauges, stress analysis strain gauge and transducer gauge. I wonder what is the different between these two types and for my purpose, which type do I need? (Sorry if this is a stupid question, but I had searched online but can't seems to find the answer)





RE: Crack monitoring strain gauge for fatigue
rp
RE: Crack monitoring strain gauge for fatigue
RE: Crack monitoring strain gauge for fatigue
RE: Crack monitoring strain gauge for fatigue
I would think, like BrianE22 mentions, you would want displacment control and just read the loads and then just add the additional load from the clip gauge to the recorded loads. The load produced by the transduces is directly related to the displacement, so I would think that would be easy to compensate for. Then, again, it has been decades since I have been directly involved, so maybe there are more problems with this approach.
Good Luck,
rp
RE: Crack monitoring strain gauge for fatigue
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"designed specifically for transducer applications with the main objective being optimum performance at lower cost for high-volume usage."
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In case the message was not clear, they offer the following disclaimer on the data sheet for the "transducer" gages.
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"They are not suitable for strain measurement in stress analysis applications. Request our Precision Strain Gages databook, or contact our Applications Engineering Department, for a complete listing of gages for precision strain measurement applications."
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Since it sounds like you only need a few (or even a few gross at most) and you are concerned enough about precision to be worried about the clip gage force, then I would definitely suggest the gages that are intended for stress analysis (i.e. -- not the "Transducer Class").
RE: Crack monitoring strain gauge for fatigue