Displacement, stiffness and load behaviour of laser-cut RAINBOW actuators

Juuti, Jari; Heinonen, Esa; Moilanen, V.-P.; Leppävuori, S.

doi:10.1016/s0955-2219(03)00465-5

Cited by 17 publications

(6 citation statements)

References 4 publications

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“…The produced components can exhibit large displacements due their higher coercive electric field and improved piezoelectric coefficients affected by their internal stress [3,[10][11][12]. It is therefore natural that the properties and methods of producing prestressed actuators are extensively investigated [13][14][15][16]. However, only little has been reported about the optimisation of the poling conditions.…”

Section: Introductionmentioning

confidence: 99%

Poling Conditions of Pre-Stressed Piezoelectric Actuators and Their Displacement

et al. 2005

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The poling procedure has always been the key issue in producing piezoelectric actuators with optimised performance. This is also true with the relatively new category of pre-stressed bender actuators, where mechanical bias achieved with a passive layer is introduced in the actuators during manufacturing. Due to these factors, the behaviour of the actuator under poling is different compared to its bulk counterparts. In this paper, two different thicknesses of commercial PZT 5A and PZT 5H materials were used in bulk actuators and pre-stressed benders realised by new method. Pre-stress was introduced by using a post-fired biasing layer utilising sintering shrinkage and difference in thermal expansion. The hysteresis loop of the actuators was measured under 0.5-7.0 MV/m electric fields at 25-125 • C temperatures, providing information about their remnant polarisation and coercive field before poling. The results showed that high electric field and 25 • C temperatures in poling provided higher remnant polarisation and coercive electric field than using 125 • C temperature at poling. Difference was especially significant in coercive electric field values where up to 114.8% difference was obtained for PZT 5H bulk actuator and 65.9% for pre-stressed actuators. Higher coercive fields can be utilized as increased operating voltage range of piezoelectric devices. The differences in results obtained here and by others can be explained by the different pre-stress level, stronger clamping of the thicker passive layers of the RAINBOW and THUNDER actuators and passive ring area introducing high tensile stresses. The same conditions were used to pole the actuators, after which the displacement and dielectric constant of the actuators were measured. The displacement measurements showed that remnant polarisation has good correlation with displacement. This fact can be used in estimating pre-stressed actuator performance before actual poling. The dielectric constant measurements with a small signal after poling gave even better correlation than the remnant polarisation.

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Section: Introductionmentioning

confidence: 99%

Poling Conditions of Pre-Stressed Piezoelectric Actuators and Their Displacement

et al. 2005

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“…The laser machined steps were designed to produce cross-sections with linearly and exponentially increasing thickness towards the edge of the actuators for both sample thicknesses previously used in RAINBOW and THUNDER actuators [10]. The exponential profile was copied from the cross-section of the RAINBOW actuators according to previous experiments [11,13]. After micro-machining the thinnest part of the actuators was 64% and 46% of the total thickness of 375 µm and 500 µm, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…Contributing factors for the improved performance are suggested to be the massloading effect, reduced elastic stiffness, enhanced phase transition and enhanced domain reorientation due to a larger tensile stress compared to corresponding pre-stressed benders [4,10]. In addition, RAINBOW has a unique structure due to the reduction process at high temperature creating a non-uniform thickness of the piezoelectric and reduced layer [11][12][13]. In the earlier analysis only constant thickness for the reduced layer has been used and the effect of the non-uniform actuator geometry in displacement capabilities has not been reported.…”

Section: Introductionmentioning

confidence: 99%

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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“…Besides metals and alloys LBM is also used in different industrial applications to machine ceramic work materials successfully. Commercial piezoceramic discs are laser cut to provide complex shapes in RAIN-BOW actuators [39]. Cutting of commercially available ceramic tiles using diamond-saw, hydrodynamic or USM are time consuming and expensive in processing of particular shape.…”

Section: Lbm Applicationsmentioning

confidence: 99%