A piezoelectric laminate theory that uses the piezoelectric phenomenon to effect distributed control and sensing of structural vibration of a flexible plate has been used to develop a class of distributed sensor/actuators, that of modal sensors/actuators. The one-dimensional modal sensors/actuator equations are first derived theoretically and then examined experimentally. These modal equations indicate that distributed piezoelectric sensors/actuators can be adopted to measure/excite specific modes of one-dimensional plates and beams. If constructed correctly, actuator/observer spillover will not be present in systems adopting these types of sensors/actuators. A mode 1 and a mode 2 sensor for a one-dimensional cantilever plate were constructed and tested to examine the applicability of the modal sensors/actuators. A modal coordinate analyzer which allows us to measure any specific modal coordinate on-line real-time is proposed. Finally, a way to create a special two-dimensional modal sensor is presented.

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A micro-impact tester has been designed and built by using a piezoelectric impact hammer as an impactor driver. During the course of an impact process, force interactions between the impactor and target surfaces were monitored continuously by a miniaturized piezoelectric loadcell embedded in the flying head assembly. After having fully characterized an impact system, the trajectory of the impactor can be calculated by using the corresponding pre-recorded impact force interaction in the simulation program. The contact and returning velocities, kinetic energy loss of the impactor and the impact penetration curve are the key information obtained from the simulation. Furthermore, the impact morphology can reveal failure mechanisms of materials by providing details such as indent shapes, coating fragments, chipping, crack type and size, and other such information which are useful in assessing the fracture toughness of testing materials. The micro-impact testing was carried out in the contact velocity ranging from 0.3 to 2.0 m/sec. Three types of materials such as metal, glass and amorphous carbon were used in studying their distinct mechanical behavior under high rate indentations. The correlations between the impact conditions, energy losses, impact morphologies and material responses are illustrated and discussed.

A micro-impact tester has been designed and built by using a piezoelectric impact hammer as an impactor driver. During the course of an impact process, force interactions between the impactor and target surfaces were monitored continuously by a miniaturized piezoelectric loadcell embedded in the flying head assembly. A 3-sided pyramidal diamond indenter (Berkovich indenter) was used as an impactor. After having fully characterized such an impact system, the trajectory of the impactor can be calculated by using the corresponding prerecorded impact force interaction in a simulation program. The contact and returning velocities, kinetic energy loss of the impactor, and the impact penetration curve are the key pieces of information obtained from the simulation. Furthermore, the impact morphology can reveal failure mechanisms of materials by providing details such as indent shapes, coating fragment, chipping, crack type and size, and other information which are useful in assessing the fracture toughness of testing materials. The micro-impact testing was carried out in the contact velocity ranging from 0.3 to 2.0 m/s. Three types of materials such as metal, glass, and amorphous carbon were used in studying their distinct mechanical behavior under high rate indentations. The correlations among the impact conditions, energy losses, impact morphologies, and material responses are illustrated and discussed.

A micro-wear testing technique has been developed by incorporating a piezoelectric pusher into an existing microindenter system. The pusher and its associated servo-control circuitry were designed to generate a precise reciprocating horizontal motion at the indenter tip for implementing a microscaled wear test. The information acquired from the test includes the wear loading curve, i.e., the normal applied load versus wear penetration depth, the friction force, and in turn, the apparent wear friction coefficient. Measuring the electrical resistance across the coating thickness is also possible if an electrical conducting indenter is utilized. Furthermore, in conjunction with the surface characterization tools, the wear morphology revealed useful information regarding the coating failure mechanism(s) and shed some light toward understanding coating tribology. The tester design concepts, operating procedure, data acquisition, and analysis will be examined. Experimental results on ultrathin carbon coatings with various thicknesses will be employed to illustrate the capabilities of the micro-wear tester.