Dr. Christopher L. Davis Profile

Dr. Christopher L. Davis

at Boeing Co

SPIE Involvement:

Author

Publications (7)

Proceedings Article | 14 August 2003 Paper

High-frequency jet nozzle actuators for noise reduction

Christopher Davis, Frederick Calkins, George Butler

Proceedings Volume 5054, (2003) https://doi.org/10.1117/12.483872

KEYWORDS: Actuators, Semiconducting wafers, Finite element methods, Chemical elements, Performance modeling, Acoustics, Denoising, Beam analyzers, Near field, Visualization

Read Abstract +

Proceedings Article | 11 July 2001 Paper

Characterization of fine-grain piezoceramic stack actuators

Christopher Davis, Donald Morris, Frederick Calkins

Proceedings Volume 4333, (2001) https://doi.org/10.1117/12.432785

KEYWORDS: Actuators, Ceramics, Semiconducting wafers, Composites, Smart structures, Amplifiers, Electrodes, Transducers, Capacitance, Data acquisition

Read Abstract +

Proceedings Article | 9 July 1999 Paper

Predicting actuation efficiency of structurally integrated active materials

Christopher Davis, Frederick Calkins, Tamara Leeks, Donald Morris

Proceedings Volume 3674, (1999) https://doi.org/10.1117/12.351586

KEYWORDS: Energy efficiency, Actuators, Mechanical efficiency, Wind energy, Amplifiers, Resistance, Magnetostrictive materials, Magnetism, Acoustics, Smart structures

Read Abstract +

A method for estimating the actuation efficiency of a structurally integrated active material is presented. A background literature search revealed many different expressions for efficiency depending upon the application and discipline of interest. Following the review of the literature, an efficiency expression was developed for a piezoelectric actuator in the frequency domain. The actuation efficiency of the piezoceramic actuator was define as the ratio of total mechanical energy imparted to the structure to total electrical energy drawn by the piezoceramic from an electrical power source. The efficiency expression is a function of the piezo electromechanical coupling coefficient, the mechanical impedance ratio of the structural to the piezoceramic material, and the frequency of operation. The developed expression was then used to analytically predict the efficiency of a single degree-of- freedom system actuated by a piezoceramic actuator. Static and quasi-static efficiency results agree with analytical results found in the literature. Dynamic analysis of the efficiency expression, however, produced unexpected and interesting results. For the given definition of efficiency, there exists a combination of material parameters and drive frequency that yield efficiencies greater than one.Further analysis provided evidence that frequency domain formulation provides that while there are instances when relatively large quantities of mechanical energy in the system exist relative to the quantity of electrical energy being drawn by the actuator, total energy is always conserved. The important result of this work was the knowledge gained in the fundamental understanding of power, energy, and efficiency as it relates to dynamic actuation of an electromechanical system. The results shown here support the concept of actuation at or near a system resonance to increase efficiency. This work is on-going; the ultimate goal of which is to develop a tool for aiding active material actuation feasibility studies by using actuation efficiency as a performance metric.

Proceedings Article | 16 June 1998 Paper

Actively tuned solid state piezoelectric vibration absorber

Christopher Davis, George Lesieutre

Proceedings Volume 3327, (1998) https://doi.org/10.1117/12.310681

KEYWORDS: Capacitance, Actuators, Capacitors, Control systems, Relays, Sensors, Signal attenuation, Switches, Prototyping, Solid state physics

Read Abstract +

A tunable solid state piezoelectric vibration absorber and an active tuning method were developed and demonstrated. A passive vibration absorber generally acts to minimize structural vibration at a specific frequency associated with either a tonal disturbance or the response of a lightly damped structural vibratos mode. Because this frequency is rarely stationary in real applications, damping is usually added to ensure some level of effectiveness over a range of frequencies. Maximum response reductions, however, are achieved only if the absorber is lightly damped and accurately tuned to the frequency of concern. Thus, an actively-tuned vibration absorber should perform better than a passive one and, furthermore, could be made lighter. In its simplest form, a vibration absorber consists of a spring-mass combination. A key feature of the tunable vibration absorber described herein is the use of piezoelectric ceramic elements as part of the device stiffness. The effective stiffnesses of these elements was adjusted electrically, using a passive capacitive shunt circuit, to tune the resonance frequency of the device. The tuning range of the absorber is thus bounded by its short- circuit and open-circuit resonance frequencies. An alternative tuning approach might employ resistive shunting, but this would introduce undesirable damping. Another feature of the device is the ability to use the piezoelectric elements as sensors. A control scheme was developed to estimate the desired tuning frequency from the sensor signals, to determine the appropriate shunt capacitance, and then to provide it. The shunt circuit itself was implemented in ten discrete steps over the tuning range, using a relay-driven parallel capacitor ladder circuit. Experimental results showed a maximum 20 dB, and a 10 dB average improvement in vibration reduction across the tuning range, as compared to a pure passive absorber tuned to the center frequency, with additional benefit extending beyond the tuning range.

Proceedings Article | 6 June 1997 Paper

Can a coupling coefficient of a piezoelectric device be higher than those of its active material?

George Lesieutre, Christopher Davis

Proceedings Volume 3041, (1997) https://doi.org/10.1117/12.275653

KEYWORDS: Aluminum, Ferroelectric materials, Capacitance, Transducers, Actuators, Ceramics, Resistors, Sensors, Dielectrics, Lead

Read Abstract +

Proceedings Article | 9 May 1997 Paper

Tunable electrically shunted piezoceramic vibration absorber

Christopher Davis, George Lesieutre, Jeffrey Dosch

Proceedings Volume 3045, (1997) https://doi.org/10.1117/12.274188

KEYWORDS: Actuators, Capacitance, Acoustics, Capacitors, Resistance, Aircraft structures, Active vibration control, Signal attenuation, Resistors, Aluminum

Read Abstract +

Proceedings Article | 12 May 1995 Paper

Inertial piezoceramic actuators for smart structures

Craig Asckler, George Lesieutre, Gary Koopmann, Christopher Davis

Proceedings Volume 2447, (1995) https://doi.org/10.1117/12.209333

KEYWORDS: Actuators, Instrument modeling, Smart structures, Electromechanical design, Performance modeling, Transducers, Solids, Reliability, Vibration control, Manufacturing

Read Abstract +

Showing 5 of 7 publications

View contact details

UPDATE YOUR PROFILE

Is this your profile? Update it now.

Sign into your SPIE.org account

Don’t have a profile and want one?

Create an account on SPIE.org

Keywords/Phrases

Search In:

Publication Years