Ring gauge for biaxial strain analysis

The ring gauge performs the same function as a strain gauge rosette by providing three independent signals from which may be deduced the three unknowns in a biaxial strain system, viz. the magnitudes of the principal strains and the directions of the principal axes relative to a datum direction. It is analogous to a delta rosette but possesses advantages over the usual method of cementing three gauges to the surface of the material.