Engineering Mechanics, UNL
The research interests in our group fall under the general topics of wave propagation and vibration. The wave propagation research has been primarily with complex media for which deterministic analysis techniques are either unsuitable or too difficult. Statistical approaches are used for obtaining important microstructural information about these complex materials which include polycrystalline metals, composites, concrete, and geophysical materials. This work has both theoretical/numerical and experimental aspects for materials characterization and nondestructive testing purposes. The ultrasonic experimental work includes studies of concrete, sintered materials, polycrystalline metals and piezoelectric materials with a new topic on measurements of third-order elastic constants.
We are also studying the mechanics of nanoscale materials characterization using the atomic force microscope (AFM) and nanoindentation. AFMs allow the surface of materials to be imaged with nanoscale resolution. More recent developments of AFM include materials characterization efforts. Some of these techniques are dynamic in nature, coupling ultrasonics with AFM. The forces which act between the AFM cantilever tip and the specimen surface are nonlinear. Obtaining useful information about the material properties of the specimen is complicated by the fact that the vibration of these cantilevers may also be nonlinear. This research follows both theoretical, numerical, and experimental topics. Both the linear and nonlinear vibrations of AFM cantilevers are being exploited for materials characterization purposes. Portions of the AFM work are done in collaboration with the Fraunhofer Institute for Nondestructive Testing (IZFP) in Saarbruecken, Germany and with the National Institute of Standards and Technology (NIST) in Boulder, Colorado.
For photographs of some of our laboratory facilities and brief descriptions of some of our work, please click on the 'laboratory' button. Or, click here.