I have performed some high strain rate split hopkinson
compression tests. The oscilloscope reads the incident and reflected
displacments (in input pressure bar) and transmitted displacment (in output
pressure bar) in volt. To convert displacement in volt (output voltage) to
mechanical strain (m/m), I have a difficalty. What is the relationship between
the output voltage (volt) (the reading from oscilloscope), excitation voltage (volt)
and strain gauge Gauge Factor (GF)?
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if you know the brand of
if you know the brand of gages (perhaps vishay) and the type of gages used, the manufacturer can provide you the relationship/ manual that will help you calculate strain from the voltages
Calibration Factor
Hi,
To get strain from osciloscope output voltage you need to find the Calibration Factor for your strain gages mounted on the both incident and transmitted bars. Using that, you will be able to convert the incident, transmitted and reflected waves to their corresponding strains. And from there and using conventional Split-Hopkinson equations you can calculate stress-strain response under dynamic loading.
Finding the calibration factor, it needs you to know your gages resistance and their G.F. and as it is mentinoed in the previous comment these two quantities are given by the S.G. manufacturer. Also more importantly, you should consider the number and the circuit type used for your strain gages mounted on each bar (if they are in quarter, half or full bridge circuit).
If you have more question feel free to contact me at farhoud1 [at] umbc.edu. We run dynamic compresison experiment on daily basis.
Thanks