Dynamics of Miniature and High-Compliance Structures: Experimental Characterization and Modeling

Background The dynamic behavior of miniature and high-compliance structures is critical for their performance. However, their low stiffness and inertia bring significant challenges to the experimental characterization and modeling of their dynamics. Traditional modal testing techniques cannot produce the required low noise, high-bandwidth dynamic models with sufficiently low forces to prevent damage to the fragile structures. Objective This objective of this work is to develop a new iterative approach that enables effective dynamic characterization of miniature and high-compliance structures. Methods The iterative approach consists of a combination of model-based simulations and experimentation. An impact excitation system I(IES) with a flexure-jointed cantilever controls the motions of an instrumented impact tip to enable specifying the bandwidth and force magnitude of the impact excitations. Successful application of the IES requires determination of the IES-parameters that produce the desired (broad) bandwidth and (limited) force magnitudes. However, for high-compliance and miniature structures, this requires the knowledge of the dynamics of the sample (the structure), which is not known a priori. To address this, the simulations use both the dynamic model of the IES and an approximate model of the sample dynamics obtained from the previous iteration in order to identify a set of favorable IES parameters for the current iteration. Results Two case studies involving a miniature blade of a jet engine turbine and a high-compliance load cell are presented to demonstrate the approach. Only a few iterations were sufficient for converging to a favorable set of parameters that produce high-bandwidth (e.g., 31 kHz) and reproducible dynamic models in the form of frequency response functions (FRFs). As compared to manual impact testing, the use of the new approach expands the bandwidth by as much as 50 times while reducing the test repetitions by more than ten times. Conclusions The presented iterative framework based on the impact excitation system addresses the shortcomings of traditional modal testing techniques and enables effective dynamic characterization and modeling of miniature and high-compliance structures.

Automated summary

This study aimed to develop an iterative approach for effective dynamic characterization of miniature and high-compliance structures, which successfully achieved high-bandwidth and reproducible dynamic models through a combination of model-based simulations and experimentation.