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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A series of piezoelectric sensors which measure the strain rate of a structyre directly arc dcvclopcd hy recognizing the fact that'due to the high output irnpedancc nature oS piczoclectric scnsors the measured signal i.; strongly influenced by the impctlancc matching circuit. tlxperimentnl data which verifies thc performance of a local strain ratc sensor is presented. A uniaxial strain ratc sensor which cornplctely eliminates the cross-axis sensitivity is developed, as well as a pure shcar strain rate scnsor which measurcs the in-planc shcar rate. T o achieve rnorc clTcctivc distributed control, a singlc-input singlc-output multi-modc scnsor/actuator dcsign approach is prcscntcd for controlling

Low flying air-bearings, "sliders," with contact sensors are used to "glide" test magnetic recording disks to be free of asperities above a predetermined height. A technical overview of the considerations necessary for accurate glide testing is illustrated by the example of an experimental flat plate PZT sensor, with electrodes divided into quadrants, to detect asperity contact. The flat plate PZT sensor detects the slider dynamic pitch, roll, and vertical vibrations of the air bearing by contact with asperities of sufficient mechanical stiffness. The sensor also detects contact by the extremely sensitive response of the resonant vibrations of the PZT/slider structure. Different linear combinations of the signal from the quadrants show mode selection based on mode symmetry. The signal response for increasing asperity interference is characterized for specific modes and a mode can be chosen by the appropriate linear combination of the signals from the quadrants. Calibration of the glide slider trailing edge flying height and roll using contact with artificial bumps of different heights is necessary for accurate glide testing. One can map the entire disk surface using the contact signal from both the air-bearing response and the bending mode response simultaneously to identify mechanically "stiff" asperities. Visualization of the mode shapes and characterization the PZT/slider structure using a laser heterodyne interferometer aid in the consistent fabrication of this class of PZT contact sensors. The considerations of sensor response, characterization of the contact signal, techniques to allow consistent PZT/slider fabrication, and calibration methods that allow the signal to be related to the test tolerances represent a technical overview of the requirements for any glide sensor technology.

A large‐deformation stress analysis of a ring‐on‐ring bending fracture test, using the finite‐element method, was used to derive the strength of chemically strengthened and nonstrengthened glass disks from experimental test data. Agreement between measured and predicted disk deflections was very good. The predicted strength data were analyzed using Weibull statistics.