Sensing Dynamic Forces by Fe–Ga in Compression

This paper concerns the sensing of dynamic force/stress by means of a measuring system based on the use of an Fe-Ga sample (Galfenol) coupled to a magnetic circuit. The study is focused on the measurement of the effective magnetic field, detected at the rod specimen surface, and its variation AH
_eff
under time-dependent applied sinusoidal stress Δσ, oscillating at frequencies between 5 and 20 Hz at different values of applied bias field Hbias (2.5 kA/m ≤ H
_bias
≤ 27 kA/m). For the considered frequency and Hbias range, the measured AHeff tends to linearly depend on Δσ, in contrast with the corresponding induction variation behavior (ΔB - Δσ), where hysteresis effects appear. With Δσ in the range of ±15 MPa, we obtain 0.06 MPa resolution in the determination of the alternating stress Δσ, a result pointing to the effectiveness and sensitivity of this Galfenol-based method for detection and measurement of time-dependent stresses.