HIGH-TEMPERATURE THIN-FILM STRAIN-GAUGES

To respond to the industrial interest of aeroengine manufacturers in carrying out instrumentation techniques for blade vibration measurements, ONERA is developing thin-film resistance strain gauges suitable for dynamic stress measurements up to 900-degrees-C. The strain gauge, deposited by r.f. sputtering onto nickel-based superalloys, is described. It consists of a NiCoCrAlY coating, insulating layer (Al2O3), sensing layer (NiCr, PdCr), intermediate splicing layer (Pt) and a protective film (Al2O3 or SiO2). The masking of the layers, the splicing of the thin films to wires and the deposition technique on complex three-dimensional structures are presented. The first electrical and mechanical properties of the sensing layers are described, as well as preliminary results concerning the thermal stability of the gauges.