Wednesday, 13 October 2004 - 3:55 PM

This presentation is part of : Micro- and Nano-scale Materials Characterization II

Contrasting load- and depth-controlled nanoindentation responses of materials

Oden L. Warren, Seth A. Downs, and Thomas J. Wyrobek. Hysitron, Inc., 10025 Valley View Rd., Minneapolis, MN 55344

Nearly all nanoindentation load-depth curves found in the literature correspond to measurement under load control. Our development of a high-performance adaptive feedforward/feedback control algorithm now makes it possible to acquire curves under depth control as well. We have utilized this algorithm to contrast load- and depth-controlled responses of a wide variety of monolithic and thin-film materials. In general, we find that depth-controlled curves exhibit higher sensitivity to transient deformation events and reveal more about underlying deformation mechanisms. Depth control is effective for passive monitoring of state-to-state transitions occurring on the time scale of transient events whereas load control involves pumping in additional energy to meet the prescribed load-time function. This extra pumped-in energy associated with load control sometimes initiates an unintended avalanche of relaxation processes that obscures the true nature of the event onset, leading to at least two published but erroneous aspects of data interpretation. Also, certain experiments unattainable under load control can be easily achieved under depth control.

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