Dynamic stress measurement with strain gauges, without stop the machin
Dynamic stress measurement with strain gauges, without stop the machin
(OP)
Hi,
I want to measure dynamic stress using strain gauges in a heat exchanger (60ºC), but we can't stop the process to glue the gauges correctly. Has anyone ever glue a gauge in a working machine?, how were the results?.
I want to measure dynamic stress using strain gauges in a heat exchanger (60ºC), but we can't stop the process to glue the gauges correctly. Has anyone ever glue a gauge in a working machine?, how were the results?.





RE: Dynamic stress measurement with strain gauges, without stop the machin
TTFN
RE: Dynamic stress measurement with strain gauges, without stop the machin
Perhaps we could be more helpful if you told us what problem you are actually trying to solve.
Mike Halloran
Pembroke Pines, FL, USA
RE: Dynamic stress measurement with strain gauges, without stop the machin
When I have had dynamics issues I have installed strain guages on running equipment and it worked fine.
-The future's so bright I gotta wear shades!
RE: Dynamic stress measurement with strain gauges, without stop the machin
Our intention is to make a detailed ODS, make FEM model with the new data to calculate static stress component, and using the vibration data and the adjusted FEM model consider the dynamic stress component, and check this result using strain gauges.
In my opinion the gauge will not be glued correctly due to the different curing time from the outside to the center. The gauge will have parts in tension and others in compression as a result of the vibration, and the results may not be accurate.
Thanks for your answer.
RE: Dynamic stress measurement with strain gauges, without stop the machin
I think I understand your concern about the CA curing progressively and locking in different amounts of strain along the gage's length because of the vibration. I've read a fair amount of stuff about strain gages, and I can't recall that being mentioned.
You may get better results with a slow curing epoxy adhesive. Put a film of Saran over the gage, then a silicone pad, then a rigid pad, and clamp the whole mess on the shell while the epoxy cures. With any luck, the clamped gage will dampen the vibration locally.
OR, much better, ask the strain gage manufacturer for help.
Given the level of fuss that's required to produce a good strain gage installation on a static object at normal temperatures, don't get your hopes up about accuracy or repeatability. You might do better with an accelerometer.
Mike Halloran
Pembroke Pines, FL, USA
RE: Dynamic stress measurement with strain gauges, without stop the machin
Using Google or Dogpile, I came up with the site http://www.stressoptics.com. I am sure there are others. The most important thing is to have a clear shot of the surface and since your situation is dynamic, you must consider a high intensity strobe. I believe this is a research project and not an off-the-shelf item! Establishing a surface displacement contour is a considerable distance away from establishing a stress contour.
RE: Dynamic stress measurement with strain gauges, without stop the machin