Force-deflection behavior of piezoelectric C-block actuator arrays

C-blocks are unique piezoelectric building blocks which can be combined in series or parallel to generate tailorable performance and exploit the advantages of bender and stack architectures. This paper presents a complete theoretical model that predicts the force-deflection behavior for any generic C-block actuator array configuration. An experimental investigation with five case studies is described that validates the model over a broad range of actuator prototypes and performance. This study characterizes the sensitivity of this class of actuator array with respect to material, geometric, and configuration parameters. The paper concludes with a comparison of the generic C-block architecture to the current state of art on a basis of absolute measures such as maximum force, deflection, and work and normalized measures such as effective stress, strain, and work per actuator volume. From this, it is concluded that C-blocks are a highly efficient, mid-range actuation technology.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49008/2/sm9502.pd

Bench-top characterization of an active rotor blade flap system incorporating C-block actuators

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76706/1/AIAA-1998-2108-892.pd

Parametric Investigation of the Deflection Performance of Serial Piezoelectric C-Block Actuators

This paper presents an investigation of the deflection performance of serial configurations of C-block piezoelectric actuators. To conduct the investigation both a theoretical and an experimental approach were used. A theoretical model was derived and experimentally verified with six different case studies. These experimental case studies were used to explore the effect on the deflection performance by modifying the geometric, material, and configuration parameters. The results demonstrate the wide versatility possible with serial C-block actuation architectures.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68931/2/10.1177_1045389X9800900308.pd

Quasi-Static Behavior of Individual C-Block Piezoelectric Actuators

Most piezoelectric actuators used in smart structure applications are either stiff stacks which produce high forces and small deflections, or compliant benders which produce large deflections and small forces. This leaves a mid-range gap in actuator performance in which many applications operate. A new class of solid state actuators, known as C-blocks, has been developed as a mid-range actuator. A C-block is a semicircular composite bender actuated with piezoelectric layers. It can be combined in series and/or parallel to increase actuator deflection and/or force. A simple, linear analytical model for the quasi-static force-deflection behavior of a generic individual C-block is presented in this paper. This model can be used to determine the relationship between force and deflection, as well as the free deflection, blocking force, actuator stiffness, and maximum energy transferable to the actuated system. This model was experimentally verified with three case studies: PZT-8 and PZT-5H ceramic unimorphs; PVdF polymeric bimorphs; and four-layer PVdF polymeric multimorphs. The results from these case studies confirm that C-blocks are over six times stiffer, and generate over two-and-a-half times more force than a comparable straight bender.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68550/2/10.1177_1045389X9700800702.pd

Microsoft Word - Jason_Moore_2008-01-0308.doc

ABSTRACT The attractiveness of the hydraulic hybrid concept stems from the high power density and efficiency of the pump/motors and the accumulator. This is particularly advantageous in applications to heavy vehicles, as high mass translates into high rates of energy flows through the system. Using dry case hydraulic pumps further improves the energy conversion in the system, as they have 1-4% better efficiency than traditional wet-case pumps. However, evacuation of fluid from the case introduces air bubbles and it becomes imperative to address the deaeration problems. This research develops a bubble elimination efficiency testing apparatus (BEETA) to establish quantitative results characterizing bubble removal from hydraulic fluid in a cyclone deaeration device. The BEETA system mixes the oil and air according to predetermined ratio, passes the mixture through a cyclone deaeration device, and then measures the concentration of air in the exiting fluid. Test results indicate the ability of the cyclone deaeration device to remove large bubbles with near 100% efficiency, while elimination of small (less than 1 mm diameter) bubbles proved to be a challenge. The explanation is provided through application of Stokes Law that shows a strong relationship between bubble size and bubble rise velocity. The theoretical analysis provides clear guidance regarding pathways towards improving the effectiveness of removing small bubbles

Longitudinal molecular trajectories of diffuse glioma in adults.

The evolutionary processes that drive universal therapeutic resistance in adult patients with diffuse glioma remain unclear1,2. Here we analysed temporally separated DNA-sequencing data and matched clinical annotation from 222 adult patients with glioma. By analysing mutations and copy numbers across the three major subtypes of diffuse glioma, we found that driver genes detected at the initial stage of disease were retained at recurrence, whereas there was little evidence of recurrence-specific gene alterations. Treatment with alkylating agents resulted in a hypermutator phenotype at different rates across the glioma subtypes, and hypermutation was not associated with differences in overall survival. Acquired aneuploidy was frequently detected in recurrent gliomas and was characterized by IDH mutation but without co-deletion of chromosome arms 1p/19q, and further converged with acquired alterations in the cell cycle and poor outcomes. The clonal architecture of each tumour remained similar over time, but the presence of subclonal selection was associated with decreased survival. Finally, there were no differences in the levels of immunoediting between initial and recurrent gliomas. Collectively, our results suggest that the strongest selective pressures occur during early glioma development and that current therapies shape this evolution in a largely stochastic manner