A magnetic domain strain gage and method of digitally measuring strain or fatigue within a ferromagnetic material by measuring the time required for an increasing magnetizing force to cause magnetic domains to flip orientation in a ferromagnetic material as a function of strain or stress within the material. The magnetic domain's maximum rate of flip is measured as a time differential by a high frequency digital oscillator which provides a digital signal indicative of the strain thereby providing increased compatibility with digital data acquisition systems and having a superior signal to noise ratio in comparison with present low signal level analog resistance strain gages.
A strain gauge comprised of a magnetic multilayer assembly exhibiting spialve effect with individual ferromagnetic layers possessing magnetostrictive properties. A magnetic field source is used to bias the magnetic moments of the ferromagnetic layers in a given direction whereby stress applied causes previously antiferromagnetically coupled moments to be angularly realigned toward a ferromagnetic arrangement. Such realignment causes a corresponding resistance change of unexpectedly high magnitude thereby providing a highly sensitive strain gauge.
