A simple estimate for the effect of cross sensitivity on evaluated strain-gage measurement
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The cross-sensitivity factor of a short-wire strain gage can sometimes be estimated by comparison of its gage factor with that of a long gage of similar construction and material.
A plot of the error introduced by the usual neglect of cross sensitivity against the known or estimatedtrue ratio of transverse to longitudinal stress or strain yields a quick estimate for any given cross-sensitivity factorn of the gage, any Poisson's ratio ν of the test piece and any stress or strain ratio. It shows whether in any particular test the influence of cross sensitivity warrants further special attention.
If the longitudinal strain exceeds the transverse strain, the error is seen to be always less than 1.3n, but if the transverse strain is larger, the error may be so high as to vitiate the result. In computations from rosette measurements, the diagram shows that the larger principal stress can be determined with an error below 1.3n, as can Tresca's and von Mises's criteria of yield, while the error in the smaller principal stress tends to be large for principal strain ratios above +10 or below −1.5.
KeywordsPrincipal Stress Strain Gage Longitudinal Strain Test Piece Principal Strain
resistance of strain gage
apparent value (assumingn=0)
true value (for knownn)
- x, y
mutually perpendicular directions
- 1, 2
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