EnginerdNate
Aerospace
- Feb 4, 2019
- 84
Hi All,
I've been tasked with setting up the instrumentation for on of my company's structural tests. I interned as a test engineer back in undergrad but since then have been firmly on the manufacturing and design side of the house so I'm a bit rusty.
I am installing strain rosettes in various places around my structure. I have all the correct math to take the strain readings and real-time do the strain transformation to get principle strains and max shear strain in the structure at each gauge location, and I've also programmed in the transverse sensitivity correction equations. I have found several references helpful in doing so, but the following two were most helpful:
I am currently using the equations from the second link. I have verified that the equations for principle strains in both are equivalent though they are presented in different forms.
Where I run into a bit of a question in on transverse sensitivity. To put it bluntly, is this truly worth the computation, or, is it worth it in some situations and not others and how would that determination be made? The strain gauges I have purchased for this test(HBM stacked rosettes) have transverse correction factors of less than .5% for each gauge. I am wondering if corrections of this magnitude are likely to be washed out by other errors in the measurement system or noise in the readings. It seems like a lot of math to dedicate to such a small correction. This question was brought on by the many simplifying assumptions Vishay makes in several places in their paper, such as simplifying. (1-nu*k) ~= 1.
That said, it only took a few minutes to add the correction factors to the calculation and now that I've done it once I have a template to use for future tests, so maybe there's just not a good reason *not* to do it. I am mostly curious what would be considered a standard approach in industry.
Thanks!
Nathan
I've been tasked with setting up the instrumentation for on of my company's structural tests. I interned as a test engineer back in undergrad but since then have been firmly on the manufacturing and design side of the house so I'm a bit rusty.
I am installing strain rosettes in various places around my structure. I have all the correct math to take the strain readings and real-time do the strain transformation to get principle strains and max shear strain in the structure at each gauge location, and I've also programmed in the transverse sensitivity correction equations. I have found several references helpful in doing so, but the following two were most helpful:
I am currently using the equations from the second link. I have verified that the equations for principle strains in both are equivalent though they are presented in different forms.
Where I run into a bit of a question in on transverse sensitivity. To put it bluntly, is this truly worth the computation, or, is it worth it in some situations and not others and how would that determination be made? The strain gauges I have purchased for this test(HBM stacked rosettes) have transverse correction factors of less than .5% for each gauge. I am wondering if corrections of this magnitude are likely to be washed out by other errors in the measurement system or noise in the readings. It seems like a lot of math to dedicate to such a small correction. This question was brought on by the many simplifying assumptions Vishay makes in several places in their paper, such as simplifying. (1-nu*k) ~= 1.
That said, it only took a few minutes to add the correction factors to the calculation and now that I've done it once I have a template to use for future tests, so maybe there's just not a good reason *not* to do it. I am mostly curious what would be considered a standard approach in industry.
Thanks!
Nathan