Sensing mechanical properties of solid materials with bimorph piezo transducers

Mechanical properties of materials, such as Young's modulus, shear modulus and linear vis-coelastic damping, are experimentally measured with a thin-film cantilever shaker. The experimental apparatus consists of a bimorph piezoelectric transducer acting as an actuator to generate base excitation to the cantilever, which is analogous to earthquake causing building vibration. The motion of the cantilever is monitored by a pair of fiber optics to measure the displacements of the fixed end and the sample. Linear viscoelastic properties of the material are measured from the resonant frequencies of the vibrating cantilever. Young's modulus and shear modulus are measured from bending and torsion resonant peaks, respectively. For high loss materials, loss tangent of the materials is obtained from the Lorenzian curve fit around the resonant peak. Material properties at various frequencies are measured by changing the length of the specimens. Furthermore, by introducing crack-like defects, the measured resonances, which may be viewed as a measure of effective moduli, are able to be adopted to locate the crack via the method of system identification.