This paper studies the vibration mitigation of a sandwich beam with tip mass using piezoelectric active control. The core of the sandwich beam is made of foam and the face sheets are made of steel with a bonded piezoelectric actuator and sensor. The three-layer sandwich beam is clamped at one end and carries a payload at the other end. The tip mass is such that its center of mass is offset from the point of attachment. The extended higher-order sandwich panel (HSAPT) theory is employed in conjunction with the Hamilton’s principle to derive the governing equations of motion and boundary conditions. The obtained partial differential equations are solved using the generalized differential quadrature (GDQ) method. Free and forced vibration analyses are carried out and the results are compared with those obtained from the use of the commercial finite element software ANSYS. Derivative feedback control algorithm is employed to control the vibration of the system. Parametric studies are conducted to examine the arrangement impact of the piezoelectric sensors and actuators on the system vibrational behavior.

Bistable structures have several applications in different areas, such as aircraft morphing wings, morphing wind turbine blades, and vibration energy harvesting, due to their unique properties. Bistable structures can be used in morphing wings and wind turbine blades since they are able to alleviate large loads by snapping from one stable position to the other one. A piezoelectric actuator can be used to bring the bistable structure back to its original position after the load is alleviated. In this paper, the transient response of a piezoelectrically actuated bistable beam is investigated experimentally for different force inputs. The goal of these experiments is to explore the ability of a commercial piezoelectric actuator to induce snap-through motion in a bistable structure. The feasibility of performing snap-through motion, and the required energy are found for different excitation force amplitudes and frequencies.

Twenty-two years ago, adaptive munitions using piezoelectric actuators were conceived. The Barrel-Launched Adaptive Munition (BLAM) program used piezoelectric elements to articulate a 10 deg. half-angle conical section on the nose of a 73 mm caliber supersonic wind tunnel model. The test article was designed to pivot the forward portion of the round about the aerodynamic center (which was collocated with the forward section center of gravity). While effective in trim articulation, the majority of actuator power was expended resisting nose inertia rather than manipulating air loads. Adaptive actuators for guided munitions have progressed greatly since that time. In 2001, major advances canard articulation for guided bullets were achieved. These were followed by the Shipborne Countermeasure Range-Extended Adaptive Munition (SCREAM) program. While the piezoelectric effectors designed for these historic programs would allow for respectable deflections, the invention of post-buckled piezoelectric (PBP) actuation would dramatically boost total deflection levels while maintaining full blocked force capabilities. These PBP actuators would be used in a variety of flight control mechanisms for different classes of UAVs. In addition to these applications, the high bandwidth of piezoelectric actuators are particularly well suited to guided munitions. This paper describes the structural mechanics and dynamics of the PBP-class actuator as integrated in guided munitions. As a critical element in ultra-high bandwidth flight control actuation, PBP actuators have been shown to possess pseudo-corner frequencies in excess of 1 kHz. Additionally, PBP actuators have been integrated into tight packing volumes in guided cannon shells while demonstrating setback acceleration tolerances of tens of thousands of g’s. Previous work illustrates several different actuation configurations as well as integration methods with canards and fins. This study links the structural mechanics of previous authors with aeromechanics to arrive at performance predictions in aerial combat. The paper lays out a guided aerial round based on the PBP concept, then uses circular error probable (CEP) predictions in a standard atmosphere quantify the required deflections for engagement of a variety of targets. The results show one order of magnitude fewer rounds being expended per kill in direct air-to-air engagements with peer aircraft. The paper shows that PBP-class actuators could be used for defensive engagements as well with the engagement of oncoming hostile missiles. The paper concludes with prediction of engagement improvements for modern aircraft like the F-35 with 25 mm rounds as well as aircraft like the F-15 with 20 mm guided ammunition.

In this paper, a new prototype is proposed for accelerated orthodontic tooth treatment. In contrast to conventional methods, where heavy vibration generators are used, the proposed design is light and small and may remain into patient’s mouth without obstructing his daily activities. To do that, a PVDF Piezoelectric actuator layer is incorporated into a bio-compatible flexible structure which is to be excited by an external electric source. Generally, application of cyclic loading (vibration) reverses bone loss, stimulates bone mass, induces cranial growth, and accelerates tooth movement. This reduce the pain experience and discomfort associated with the treatment and also enhances the patient compliance with the treatment. Vibration has the advantage of minimal side effects in comparison to medicinal treatments. This configuration enables the operator to adjust the vibration frequency as well as the orthodontic force exerted on the tooth.

This paper presents the development process of an electrically insulating and liquid-impermeable coating for piezoelectric actuators. Against the background of flow investigations of an adaptive airfoil in a water tunnel the adaptive lip including PZT-ceramics for the active lip deformation must be insulated and sealed up against the ingress of moisture. Due to high electric field strength of 2 kV/mm between electrodes of multilayer actuators any ingress of moisture would lead to a reduction of the dielectric strength and may cause a short circuit. In order to prevent failure of the adaptive lip the electrical connections of the actuators have to be insulated by a waterproof coating. A service life of at least 10 7 load cycles at a frequency of 100 Hz is required for the actuators. Therefore the coating should be as ductile as possible otherwise it could crack and water could diffuse into the actuators. That is why the yield strength of the coating has to be higher than of the actuators, which is 0.3 %. For the investigation of the waterproofness several samples are coated with different materials in various processes. First the actuators are moulded in epoxy resin and then a diffusion-resistant PVF-foil is applied. After a screening of different materials, an additional coating with a two-component tar-epoxy resin in combination with a gold coating applied by a PVD process seems to be the most suitable process. Another promising waterproof coating is the atomic layer deposition (ALD). It is a slightly changed chemical vapor deposition (CVD) and referring to the studies of Abdulagatov et al. an ALD of aluminum oxide (Al 2 O 3 ) and titanium dioxide (TiO 2 ) can slow down the corrosion of static copper specimens in water for ∼80 days [1]. Through a redrying procedure during test intermissions an increased underwater service life of the piezoelectric actuators is achieved.

This paper investigates the heaving and pitching of a wing-like parameterized cantilevered plate with a leading edge stiffener and clamp variation when actuated with a surface-bonded piezoelectric actuator. The response is analyzed using a finite element model that is validated by comparison with known analytical solutions. The validated finite-element model is subjected to a harmonic excitation parametric analysis. The parameters varied in the model are the root clamped percentage, leading edge stiffener thickness, and the aspect ratio of the plate. The model is examined at the first two Eigen frequencies. Metrics of heaving and pitching are developed using surface fitting methods and their amplitudes and phases are reported throughout the parameter space. Emphasis is placed on the interaction and coupling of the first two modes of vibration with respect to the parameters. A piezo-composite wing prototype is fabricated and actuated harmonically with a Macro-Fiber Composite actuator while leading edge stiffener thickness and root clamped percentage is varied. The resulting experimental data is used to further validate the theoretical models.

In the conventional implementation of synchronized switch damping (SSD), the switches are intended to occur at every displacement extrema. However, recent work reveals that switching at the vibration peaks is only optimal for displacement reduction under resonance excitation. In general, the optimal switch timing is dependent on the excitation frequency along with the electromechanical coupling and modal damping of the structure. This work seeks to develop a control framework that searches through the possible switch times to find the optimal switch time for synchronized switch damping on an inductor (SSDI) under steady state excitation. The control law does not need any knowledge of the system, only requiring the voltage of the piezo actuator to develop a displacement estimate that is minimized by adjusting the switch timing. Furthermore, the controller naturally senses changes in the excitation and adapts the switch timing to best reduce displacement under the new excitation.

This paper focuses on the Synchronized Switching Damping (SSD) control, a semi-active vibration suppression technique based on the coupling between a mechanical structure and piezoelectric actuators. This control family is optimized for structures subjected to mono-harmonic excitation. Anyway, in the last years, different solutions to address multi-harmonic and multi-modal excitation have been developed. One of them is the so-called Modal SSD, where the switches of the shunting circuit are governed by the behavior of the modal coordinates of the structure. Although the control performance is good, this paper shows that there are still some issues to be solved. For this reason, the paper proposes a modified version of this control strategy able to improve the control performance without increasing the circuit complexity. The proposed solution is firstly described in detail and then tested and compared with the existing ones on the numerical model of a cantilever beam.

A new approach to measure direct current (DC) using shape memory alloy (SMA) tuning piezo cantilever resonant frequency technique is proposed in this work. The proposed current sensor system is designed using an electrically insulated SMA wire surface mounted on the cantilever beam with piezoelectric actuator. The cantilever beam is maintained at resonance using a closed loop piezo resonator circuit and the current ‘I’ to be measured is given to the SMA wire. The current induced temperature change of the SMA wire produces a mechanical shape change and produces a stiffness change to the resonating cantilever beam. The shift in resonant frequency due to the stiffness change is measured, which is related to the input electrical current ‘I’ to the SMA wire. The key enabling concept of this proposed work is to alter the cantilever resonant frequency using the shape changing property of SMA wire with input unknown electric current. The analytical model of the current sensor system is derived and the results are compared with the experimental results. The SMA coupled with piezo actuator based resonant current sensing system is evaluated for the input current range of 0 to 0.5A. The proposed current sensing concept is simple and completely novel and it is found that it has very high sensitivity to current and result is piecewise linear.

Impedance-based structural health monitoring (SHM) is a non-destructive, active technique for real-time structural damage assessment. Conventional impedance-based SHM practices apply a sinusoidal signal of fixed amplitude to excite the piezoceramic patch and obtain the impedance signature over a certain frequency range. Damage is then detected by comparing the measured impedance signature to a baseline measurement taken at the pristine state. In this work, the amplitude of the driving signal, which is directly related to the magnitude of the excitation force acting on the structure, is introduced as an additional variable, and sweeps over both frequencies and amplitudes are performed. Several structural defects, such as cracks and loose joints, are nonlinear in nature. Therefore, changing the excitation force will allow the detection of such damage induced nonlinearities and track their evolution. Numerical simulations are carried out to study the effects of nonlinearities on the impedance signature using a single mode model. Several types of structural nonlinearities, such as hardening, softening, and nonlinear damping are studied with the assumption that the piezoelectric actuator stays in its linear regime. Experiments are conducted on a single beam and a lap joint, and impedance signatures in the range of 12–15 KHz are measured at different levels of excitation. Nonlinear damping and softening behavior are detected experimentally by examining the measured impedance signatures. Numerical and experimental findings suggest the possibility of detecting and tracking structural nonlinearities using impedance measurements.

Previous work has demonstrated that piezoceramics are capable of generating net wave propagation without reflections in one-dimensional structures. The investigation into cylindrical traveling waves provides insight into unique dynamics (i.e., symmetric and non-symmetric modes) that have yet to be fully defined for two and three dimensional systems. The work herein will focus on the generation and characterization of traveling waves that propagate along the circumferential direction. The coupled system, given by a free-free cylinder with multiple piezoelectric actuator (PZT) patches, is used to evaluate several traveling wave modes in the cylinder. The use of structurally integrated piezoelectric patches as actuators has many advantages over the conventional shakers. Apart from the small, low weight, low cost and the size of these ceramic plates, PZTs can also generate waves over a wide frequency range. The use of multiple PZTs can be leveraged to excite the systems at a given frequency with a defined phase difference between them in order to generate highly controlled directional traveling waves in the cylindrical structure without reflections. Finite Element Modeling (FEM), in conjunction with experiments, were conducted to provide a comprehensive understanding of the generation and propagation behavior of the traveling wave modes in a thin walled cylinder.

Due to their very high applicable forces, frequencies and their stiffness, piezoceramics are feasible to serve as integrated actuators in machines. The application of piezo based components in production engineering was subject of plenty of investigations in the past. That focuses primarily on systems for condition monitoring, structural vibration reduction or chatter prevention. However there are currently also few approaches that aim to use piezo actuators for directly induced vibrations for improved machining processes. In this paper we present an overview of such systems, their parameters and the technological background. Known approaches will be classified and divided into groups considering their working principles, actuator performance and application technology. Ultra sonic machining (USM) for example is a comparatively old approach which applies ultrasonic vibrations of a sonotrode to an abrasive slurry for machining hard, brittle and nonconductive material. Vibration assisted machining (VAM) systems are rather different. They are characterized by low stroke, uncontrolled but highly frequent resonant vibrations of the tool to achieve enhanced chipping behavior or generally enable to machine certain hard materials. Fast Tool servo (FTS) systems are even more complex. They apply an overlaid controlled movement of the cutting edge to manufacture microstructures or possess to manufacture complex geometries like non circular bores or turned parts. Selected systems will be presented in detail showing their design approach, actuator parameters, control considerations and measurement data of manufactured parts. These will be for instance an ultrasonic deep hole drilling tool, a form honing system, an active spindle mounting for micro contouring and a piezo based machine table for manufacturing non circular bores in small workpieces. Summarized the existing systems will be compared considering their advantages and eventual hindrances. Beyond that the outlook will show problems, which need to be solved in the future to enable piezo assisted machining systems a more comprehensive application in manufacturing.

Traveling waves have shown the potential to transport material and are thus investigated as a propulsion mechanism. Through the use of piezoelectric actuators (PZTs), traveling waves were produced in beams with both free-free and fixed-free boundary conditions. It is shown that traveling waves can be generated by exciting two PZTs at a common frequency with a phase difference between the PZT signals. Experimentation showed the signal that creates the best traveling wave occurs at a driving frequency halfway between adjacent bending resonance frequencies and a phase difference of 90° between both PZTs signals. This has produced traveling waves in fixed-free beams and free-free beams in both air and water as well as for an underwater vehicle. These traveling waves generated useful propulsion in both the fixed-free and free-free beams.

This paper presents the design, optimization, realization and testing of a novel wing morphing concept based on compliant structures actuated by Macro Fiber Composites. The geometry of the compliant morphing ribs is determined through multidisciplinary optimizations. The static and dynamic behavior of the wing, and the effect of activating the actuators, is assessed using 3-D aeroelastic simulations. The performance and manufacturability of a wing designed according to this approach are investigated. The achieved active deformations produce sufficient roll control authority to replace conventional ailerons. The numerical simulation for the conformal shape adaptation of the wing is compared to experimental results, showing good agreement. The aerodynamic and structural behavior of the introduced concept is investigated through a validated finite element model, revealing the potential of the presented morphing wing. A closed-loop controller driving high-voltage electronics counteracts the nonlinearity and hysteresis of the piezoelectric actuators, allowing for controlling the wings’ morphing level.

There is interest in developing devices that mimic the sound transduction of the cochlear hair cells. Current artificial hair cell (AHC) designs have focused on passive transduction of sound into electrical signals. However, measurements inside living cochleae have revealed that a nonlinear amplification is at work in mammalian hearing. This amplification lowers the threshold for sound detection allowing mammals to hear faint sounds. The nonlinearity results in an amplitude compression whereby a large range of sound pressure levels produces a smaller range of displacements. This compressive nonlinearity gives the ear a large dynamic range. This work seeks to develop and analyze active artificial hair cells which employ a bio-inspired amplification to improve performance. This paper examines two artificial hair cell designs. The first is an 18.5 in long aluminum cantilever beam which is excited and controlled using piezoelectric actuators along the length of the beam. The second design is a one inch piezoelectric bimorph beam subject to a base excitation. In both cases a nonlinear feedback control law is implemented which reduces the beam’s linear viscous damping and introduces a cubic damping term. Model and experimental results show the control law amplified the response of the artificial hair cell to low excitation levels near the resonance frequency. Increasing input levels produced a compressive nonlinearity at resonance similar to that observed in measurements from mammalian cochleae. This work could lead to the development of new bio-inspired sensors with a lower threshold of detection, improved frequency sensitivity, and larger dynamic range.

Electromechanical actuators that generate large displacements, have large load capabilities, and demonstrate strong resonance characteristics are in great demand in the areas of precision positioning, active vibration control, and energy harvesting. Piezoelectric materials have been widely investigated for these applications because of their high energy density, quick response time, and relatively low driving voltages, but they demonstrate very small strain, typically about 0.1%. We present experimental and finite element results for two designs that use active and passive frames, respectively, to enhance the small strain in piezoelectric multilayer stacks. The first design, stacked-HYBATS, employs the synergetic contribution of d 33 and d 31 mode piezoelectric material. Finite element results show that this structure can generate over 50 microns of displacement and nearly 40 N of blocking force in a 36 mm × 22 mm × 10 mm footprint. The second design employs frames made from passive materials to form two stages of strain amplification in a 42 mm × 30 mm × 20 mm footprint. This two-stage design can produce over 600 microns of displacement and has a blocking force of 27 N. The active and passive materials of both designs can be varied to maximize displacement and/or blocking force. The stacked-HYBATS and the two-stage amplification system display favorable force-displacement capabilities and are promising for a variety of manufacturing and space technology applications.

Ultrasonic vibration has been proven effective in reducing dynamic friction when superimposed onto the macroscopic relative velocity between two surfaces. This phenomenon is often referred to as ultrasonic lubrication. Piezoelectric materials can be employed to generate ultrasonic vibration. Typically, solid or fluid lubricants are employed to mitigate wear. However, in applications such as aerospace systems, which operate in particularly harsh environments, traditional lubrication methods are not always applicable. This paper investigates the relationship between friction force reduction and wear reduction in ultrasonically lubricated surfaces. A pin-on-disc tribometer is modified through the addition of a piezoelectric transducer which vibrates the contact between pin and disc. A piezo-actuator is installed to generate 22 kHz vibration in the direction perpendicular to the disc. Three different linear speeds are employed by changing rotation speeds of the disc and running time. Friction and wear metrics such as volume loss, surface roughness, friction forces and stick-slip effects are compared before and after application of ultrasonic vibration. Relationships between linear speed and friction reduction, stick-slip reduction, and wear reduction are analyzed.

A coupled electro-aero-mechanical modeling and optimization scheme for two solid-state piezocomposite variable-camber wing concepts is presented. The proposed concepts employ a continuous inextensible surface, simple boundary conditions and surface bonded piezoelectric actuators. The partially-active surfaces are designed to have sufficient bending stiffness in the chordwise and spanwise directions to sustain shape under aerodynamic loading. In contrast, the in-plane stiffness is relatively high; however the necessary deformations that are required to change the aerodynamic response can still be attained while maintaining the surface perimeter constant. Coupled with the continuous boundary conditions and the spar structure, the proposed concepts can achieve significant change in aerodynamic response quantified in terms of lift coefficient and lift-to-drag ratio under aerodynamic loading. A coupled analysis of the fluid-structure interaction is employed assuming static-aeroelastic behavior which allows the realization of designs that can sustain aerodynamic loads. Two prototypes are briefly presented.

Synthetic jets offer new capabilities for localized active cooling of electronics due to their compact size, low cost and substantial cooling effectiveness. The design of devices to create synthetic jets and optimize active cooling performance is challenging due to the strong, two way, fluid-structure interaction (FSI) between the working fluid and the flexible structure that moves the fluid driven with piezoelectric actuators. Previous modeling efforts relied on lumped parameter approaches or electrical analogs. Although computationally less intensive, these approaches may not be accurate in all regions of the design space of interest and trade off fidelity for ease of use. In this effort, a 3D finite element model of the structure is coupled with a 3D computational fluid dynamics model of the fluid to explore the viability of such an approach. The motion of the structure moves the fluid grid, and the fluid feeds back pressure forces onto the structure that are required to converge at each iteration. Transient response of the deflection, pressure and exit velocity will be presented. Validation of the FSI model with experimental data for the frequency response of these quantities will also be presented.

Cylindrical shells, very commonly used in aerospace applications, are susceptible to buckling when subjected to static and dynamic or transient loads. Bucking load enhancement with minimum weight addition is an important requirement in space structures. Buckling control of space structures using piezoelectric actuators is an emerging area of research. The earlier work on enhancement of buckling load on columns reported a 3.8 times enhancement theoretically and 123% experimentally [1–2]. The enhancement was (25%) when buckling control was implemented on plates [3] using PZT actuators. Buckling control of cylindrical shells is challenging because of the uncertainties in the location of buckling and the coupling between bending and membrane action. Earlier attempt to improve the buckling load carrying capacity of the cylindrical shell did not result in a considerable increase in the buckling load [4]. This is because the buckling modes of cylindrical shell are very close to each other when compared to structures like column and plate. An optimized actuator location is hence necessary to improve the load carrying capacity of the cylindrical shells. Unlike vibration control problems where the actuators locations are optimized to minimize the structural Volume Displacement (SVD) or to maximize the energy dissipation, buckling control is aimed at controlling the critical modes of buckling and hence improving the load carrying capacity of the shells [5]. Numerical analyses are carried out, comparing different configurations used in buckling control of thin shells. Experiments are performed to support the numerical analysis as the behavior of cylindrical shells under axial compression is highly sensitive to geometric imperfections. Load – Axial shortening graphs are used to compare the performance of cylindrical shell for the various actuator configurations.