Torsional pendulum system for measuring the shear modulus and internal friction of magnetoelastic amorphous wires

An inverted torsional pendulum system for measuring the shear modulus and internal friction of amorphous wires as functions of applied magnetic field and axial stress is described. The axial stress can be reduced to less than 0.5 MPa (6 Mn load). A capacitive rotation sensor achieves angular position sensitivity of 0.5 degrees , and permits measurements at strain levels as low as 2.5*10 -6 . The oscillations are digitized and curve fitted in the time domain to obtain modulus values with a typical resolution of 1 in 10 4 . Examples are given of data obtained with Fe-based amorphous wires.