Sensing Mechanical Properties of Solid Materials with Bimorph Piezotransducers
Mechanical properties of materials, such as Young's modulus, shear modulus andlinear viscoelastic damping, are experimentally measured with a thin- lm cantilever shaker. Theexperimental apparatus consists of a bimorph piezoelectric transducer acting as an actuator togenerate base excitation to the cantilever, which is analogous to earthquake causing buildingvibration. The motion of the cantilever is monitored by a pair of ber optics to measure thedisplacements of the xed end and the sample. Linear viscoelastic properties of the materialare measured from the resonant frequencies of the vibrating cantilever. Young's modulus andshear modulus are measured from bending and torsion resonant peaks, respectively. For highloss materials, loss tangent of the materials is obtained from the Lorenzian curve t around theresonant peak. Material properties at various frequencies are measured by changing the lengthof the specimens. Furthermore, by introducing crack-like defects, the measured resonances,which may be viewed as a measure of e ective moduli, are able to be adopted to locate thecrack via the method of system identi cation.