Manufacturing of prestressed piezoelectric unimorphs using a postfired biasing layer

Juuti, Jari; Jantunen, Heli; Moilanen, V.-P.; Leppävuori, S.

doi:10.1109/tuffc.2006.1632674

Cited by 17 publications

(18 citation statements)

References 30 publications

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“…5. The values are modest compared to values of RAINBOW, THUNDER or PRES-TO, but can be significantly improved by increased prestress, addition of passive material or proper clamping [15].…”

Section: Resultsmentioning

confidence: 85%

“…After measurement, electrodes were sprayed on the actuator surfaces using conductive silver paint (Electrolube, UK) with low mechanical strength to avoid the constraining effect of the fired electrodes with its associated additional influence on the bending [15]. The coercive electric field was measured by Radiant RTV6000HVS system (Radiant Technologies, USA) and poling of the actuators was carried out in a 3.0 V/µm electric field in silicone oil at room temperature for 30 minutes.…”

Section: Methodsmentioning

confidence: 99%

“…1) along the centreline of the free and clamped actuators was measured in a ±0.5 V/µm electric field at 10 Hz frequency using a fibre-optic laser vibrometer OFV-5000 (Polytec GmbH, Germany) and XY-table [16,17]. Additionally, displacement at the centre of the free gradient actuators was measured from ±0.1 V/µm to ±0.5 V/µm electric fields at 10 Hz frequency under applied weights up to 18.8 g. Stiffness of a PZT 5H bulk disc and micromachined actuators was measured utilising the measurement system presented by Juuti et al [15]. The actuators were placed freely on an alumina ring in order to allow larger bending of the samples.…”

Section: Methodsmentioning

confidence: 99%

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Electromechanical performance of structurally graded monolithic piezoelectric actuator

et al. 2008

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In this paper, the effect of structural gradients in monolithic piezoelectric actuators is investigated. Different cross-section profiles were micro-machined with a laser into commercial PZT 5H bulk discs with thicknesses of 375 µm and 500 µm (∅ 25 mm). Profiles and curvatures of the actuators were measured which showed both concave and convex structures, thus indicating pre-stress of the actuators. After poling, the distribution of out-of-plane displacement was scanned by a fibre-optic laser vibrometer. Maximum displacements of ∼6.3 µm and ∼24.8 µm were obtained from a freely moving and clamped ∼375 µm thick actuator, respectively, in a ±0.5 V/µm electric field at 10 Hz frequency without load. Furthermore, deflection in the centre of the actuators was measured up to 184 mN load using the same electric field and frequency. Bending of the bulk actuators without any additional layer was a consequence of the gradient in poling and driving electric field via thickness variation of the material. Hence, different regions produced strain distribution and bending in a similar fashion to other benders. Actuators with the highest arch height exhibited the highest displacement and load bearing capabilities derived from the increased area moment of inertia and enhanced piezoelectric response due to pre-stress. The results show that the monolithic bending actuators can be realised by simple structural designing of the actuator. Such structural gradients can be one reason contributing to the higher displacement of RAINBOW actuators compared to other pre-stressed actuators. In a further development, the structural gradients can be utilized in high displacement pre-stressed actuators and in miniaturized monolithic piezoelectric devices.

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“…5. The values are modest compared to values of RAINBOW, THUNDER or PRES-TO, but can be significantly improved by increased prestress, addition of passive material or proper clamping [15].…”

Section: Resultsmentioning

confidence: 85%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Electromechanical performance of structurally graded monolithic piezoelectric actuator

et al. 2008

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“…Next the profile and the curvature of the actuators were measured with a DEKTAK 8 Stylus Profiler (Veeco, USA). The electrodes were sprayed on the micro-machined bottom surfaces using conductive silver paint (Electrolube, UK) with moderately low adhesion to avoid the constraining effect associated with fired electrodes [11]. Hysteresis measurements were then performed in silicone oil at 25-100°C temperatures with 0.5-5.0 kV/mm electric fields for both the graded samples and a bulk disc (PZT 5H, ∅ 25 mm) with thickness of 375 µm.…”

Section: Methodsmentioning

confidence: 99%

Non-uniform electric field in poling of structurally graded monolithic piezoactuator

et al. 2010

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In this paper the effect of a non-uniform electric poling field and its optimisation for structurally graded piezoelectric actuators are investigated. The two compared actuator structures were both based on commercial PZT 5H bulk discs with thicknesses of 375 µm (Ø 25 mm), where one was machined into a graded structure with a step-like decrease of the thickness towards the centre and one intact. The hysteresis loops of the pre-stressed concave shaped actuators were measured under 0.5-5.0 kV/mm electric fields at 25-100°C temperatures, and the remanent polarization and coercive electric field were determined. The graded structured actuator obtained ∼10% higher coercive field compared to the non-graded actuator, when measured at 25°C and 5.0 kV/mm. On the other hand the remanent polarisation values of the graded actuator were slightly lower than non graded bulk values. However the maximum decrease was only 9.6% under 5.0 kV/mm. The results show that strain and stress gradients in the structure are generated when exposed to an electric field. Furthermore, as a consequence of the restricted dimension changes, an inherent bending of the monolithic ceramic structure was obtained which can be utilised, for example, in miniaturised micro-machined actuators or in larger pre-stressed benders.

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“…A solution consists of pre-stressing the component in compression to have a symmetric actuation profile. For patch actuators, carefully chosen layers can compress the material during a heating cycle using different coefficients of thermal expansion [81]. In the case of piezoelectric stack actuators, the piezoelectric layers are placed inside a casing with a compressive spring.…”

Section: Asymmetric Actuationmentioning

confidence: 99%

Smart actuation mechanisms for helicopter blades : design case for a Mach-scaled model blade

Paternoster¹

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Today's helicopters are the result of collaborative work in mechanical engineering and aeronautics. The European project "Clean Sky" aims at improving the efficiency and the global transport quality of aircraft. In the field of rotorcraft, the research in this project is currently focussing on active blade systems to adapt the aerodynamic properties of the blade to the local aerodynamic conditions. Fuel-efficiency, reduction of vibration and noise and increase of the helicopter maximum speed are the benefits expected from these new technologies. To envision the implementation of these innovative blade concepts, this thesis investigates the selection process for actuators, the methods to design and optimise actuation systems and the procedures to validate them through simulations and testing.Integrating an actuation system in helicopters is especially difficult because of a combination of challenges. To begin with, these include the tremendous loads due to the rotation of the blade, the limited space available, and constraints regarding durability. Secondly, the impact that the actuation system will have on the rotor blade behaviour has to be taken into account. And lastly, integrating the component inside the actual structure of a rotor blade should be feasible. A system based on piezoelectric actuators provides a potential solution to meet these challenges. A selection process has been established in Chapter 2 to match an actuation technology to application requirements. Among many of the smart blade concepts under development, the active Gurney flap is considered in the framework of the Clean Sky Innovative Technology Development project "Green Rotor Craft", for its potential impact on the blade performance and technology readiness. Actively deploying the Gurney flap on the retreating side of the helicopter increases the lift of the rotorcraft and its overall performances. To validate this technology, numerical studies and wind-tunnel testing on reduced-scale rotor blades are necessary. The procedures detailed in this work are applied to the design of an actuation system to fold and deploy a Gurney flap for a Mach-scaled rotor blade. Additional challenges arose due to the reduction in size: the centrifugal acceleration is increased and the space available inside the blade is drastically reduced.Computational Fluid Dynamic simulations are performed in the first step of the design procedure to obtain the aerodynamic loads on the Gurney flap for various realistic combinations of deployment levels, orientations of the blade in the flow and airspeeds (Chapter 4). Secondly, the design of the actuation mechanism is performed using a two-step approach: (1) computer generated topologies are analysed to find a suitable initial geometry; (2) an optimisation is carried out to maximise the displacement and force of the structure integrating a piezoelectric patch actuator. The resulting structure presents the characteristic shape of a "Z" (Chapter 5). It converts the strains generated by the piezoelectric actuator into rela...

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Manufacturing of prestressed piezoelectric unimorphs using a postfired biasing layer

Cited by 17 publications

References 30 publications

Electromechanical performance of structurally graded monolithic piezoelectric actuator

Electromechanical performance of structurally graded monolithic piezoelectric actuator

Non-uniform electric field in poling of structurally graded monolithic piezoactuator

Smart actuation mechanisms for helicopter blades : design case for a Mach-scaled model blade

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