Local Reinforcement Effect of a Strain Gauge Installation on Low Modulus Materials

The reinforcement effect of electrical resistance strain gauges is well documented in the technical literature. In this paper the local reinforcement effect in tension is studied by using a simple theoretical model by considering a strain gauge mounted on a semi-infinite plate having the same width of the strain gauge and subjected to a uniaxial tension load. Neglecting the effect of the adhesive layer and considering the interface shear stress as an exponential distribution, the proposed model gives a closed-form solution. In detail, this model permits a simple formula to be obtained which allows the user to correct the local reinforcement effect provided that a proper calibration is performed by installing a strain gauge, of the same type as that used on the structure, on a low modulus material. Experimental evidence of the proposed method is shown. Experimental proof of the positive effect of large grid lengths on the local reinforcement effect is also reported.