The quasi-static sliding contact stress field due to a spherical indenter on an elastic half-space with a single layer is studied. The contact problem is solved using a least-squares iterative approach and the stress field in the layer and substrate is determined using the Papkovich-Neuber potentials. The resulting stresses are discussed for different values of the layer stiffness relative to the substrate and also for different values of the friction coefficient.

Incorporating the piezoelectric effect into classical laminate plate theory, distributed sensors and actuators capable of sensing and controlling the modal vibration of a one-dimensional cantilever plate are derived theoretically and verified experimentally. It is shown that critical damping of a particular mode can be achieved using such a modal sensor/actuator combination as long as the vibrational amplitude of the controlled structure does not saturate the modal actuator. Since the sensor signal is proportional to the modal coordinate time derivative, velocity feedback control can be employed without using any element tuned to the resonant frequency in the feedback controller. Therefore, the sensitivity of the closed-loop performance and stability to resonant frequency variations is minimized. By eliminating electromagnetic interference and ground loop noise, critical damping is experimentally demonstrated for the first mode of a one-dimensional cantilever plate using PVF2 as the sensor/actuator material.

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Piezoelectric strain rate gages have been designed using linear piezoelectric theory and relatively simple circuitry that can be used to measure an average strain rate at a point of a structure. By combining the effective surface electrode, appropriate skew angle and the correct polarization profile, a uniaxial strain rate gage that measures only the strain rate along a specified direction and a pure shear strain rate gage that measures the in-plane shear strain rate are developed. Experimental as well as theoretical results are presented. Various types of generalized piezoelectric strain rate gages are also introduced and discussed.

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