Resistance Change of Strain Gages Bonded to Curved Surfaces
The strain ε occurring on the resistive element of a strain gage bonded to a curved surface may be expressed by the following equation:
For example, if a uniaxial KFGS gage, of which the gage base including the adhesive layer is 0.015 mm thick, is bonded to a curved surface of r = 1.5 mm, the strain gage already receives strain of approximately 5000 μm/m.
If the gage factor Ks is 2.00, and the gage resistance is 120 Ω,
Since R/R = ε・Ks
ΔR = 5000 × 10-6 × 2 × 120
Resistance increases by approximately 1.2 Ω.
If the gage is bonded inside the curve, the resistance decreases.