New mechanical stress transducers based on amorphous alloys

Novel stress transducers of simple construction are described, which can easily be formed into arrays with a great reduction in interconnections relative to discrete strain gauges. Their frequency response extends to DC, and the arrays lend themselves to measuring distribution of pressure or shear at interfaces between contacting surfaces. The principle of operation is based mainly on the properties of acoustic delay lines made of high magnetostriction materials, in particular amorphous alloys. A sensor site is defined by the crossing of a conductor close to a delay line. A pulsed current in the conductor creates an acoustic pulse in the delay line. Mechanical input to the sensor modulates this excitation. This occurs either by displacement of a passive core or by change in its permeability due to stress. Sensors at different sites along the line can be excited simultaneously, producing pulses which are detected serially. Experimental work showing the response of prototype transducers in which Metglas 2605SC alloy is used both as the delay line and as the stress converter is reported. Aspects of performance including the spatial resolution achievable and design factors relating to applications are discussed