Shear moduli of metal specimens using resonant column tests

The shear moduli of cylindrical metal specimens were determined by performing resonant column tests in a torsional mode of vibration. The tests were performed on four different metals, namely (i) aluminum, (ii) brass, (iii) copper, and (iv) mild steel. Keeping the length (L) of the specimens the same, different diameters (d) were chosen to vary the torsional stiffness and, thereby, the resonant frequency. Additional circular plates were attached to the top of the drive mechanism to have different resonant frequencies with the same torsional stiffness (K T ). The shear moduli (G) were established by two different methods, namely (i) from the evaluation of K T and (ii) by first determining the mass moment of inertia (J d ) of the drive mechanism and then finding G from the measured circular resonant frequency (� n ). Both the methods provide exactly the same answer(s). For aluminum and brass, the measurement of the shear modulus was found to be much more accurate; the maximum variation of the shear modulus with diameter (8-12 mm/15 mm) for the same driving input voltage (torque) was around 3.3 for aluminum and 1.2 for brass. On the other hand, in the case of mild steel and copper, the variation of shear modulus was around 9.2 and 7.2 , respectively. The measured values of the shear moduli were found to compare well with the data reported from literature for the different chosen metals. Copyright © 2019 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-295