The Experts below are selected from a list of 69 Experts worldwide ranked by ideXlab platform
Ron Barrett - One of the best experts on this subject based on the ideXlab platform.
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post buckled precompressed subsonic micro flight control actuators and surfaces
Smart Materials and Structures, 2008Co-Authors: Ron Barrett, Roelof VosAbstract:This paper describes a new class of flight control actuators using Post-Buckled Precompressed (PBP) piezoelectric elements to provide much improved actuator performance. These PBP actuator elements are modeled using basic large deflection Euler-beam estimations accounting for laminated plate effects. The deflection estimations are then coupled to a high rotation kinematic model which translates PBP beam bending to stabilator deflections. A test article using PZT-5H piezoceramic sheets built into an active bender element was fitted with an elastic band which induced much improved deflection levels. Statically the bender element was capable of producing unloaded end rotations on the order of ±2.6°. With axial compression, the end deflections were shown to increase nearly 4-fold. The PBP element was then fitted with a graphite-epoxy aeroshell which was designed to pitch around a tubular stainless steel Main Spar. Quasi-static bench testing showed excellent correlation between theory and experiment through ±25° of pitch deflection. Finally, wind tunnel testing was conducted at airspeeds up to 120kts (62m/s, 202ft/s). Testing showed that deflections up through ±20° could be Maintained at even the highest flight speed. The stabilator showed no flutter or divergence tendencies at all flight speeds. At higher deflection levels, it was shown that a slight degradation deflection was induced by nose-down pitching moments generated by separated flow conditions induced by extremely high angles of attack.
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post buckled precompressed pbp subsonic micro flight control actuators and surfaces
The 14th International Symposium on: Smart Structures and Materials & Nondestructive Evaluation and Health Monitoring, 2007Co-Authors: Ron Barrett, Roelof Vos, Roeland De BreukerAbstract:This paper describes a new class of flight control actuators using Post-Buckled Precompressed (PBP) piezoelectric elements to provide much improved actuator performance. These PBP actuator elements are modeled using basic large deflection Euler-beam estimations accounting for laminated plate effects. The deflection estimations are then coupled to a high rotation kinematic model which translates PBP beam bending to stabilator deflections. A test article using PZT-5H piezoceramic sheets built into an active bender element was fitted with an elastic band which induced much improved deflection levels. Statically the bender element was capable of producing unloaded end rotations on the order of ±2.6°. With axial compression, the end deflections were shown to increase nearly 4-fold. The PBP element was then fitted with a graphite-epoxy aeroshell which was designed to pitch around a tubular stainless steel Main Spar. Quasi-static bench testing showed excellent correlation between theory and experiment through ±25° of pitch deflection. Finally, wind tunnel testing was conducted at airspeeds up to 120kts (62m/s, 202ft/s). Testing showed that deflections up through ±20° could be Maintained at even the highest flight speed. The stabilator showed no flutter or divergence tendencies at all flight speeds. At higher deflection levels, it was shown that a slight degradation deflection was induced by nose-down pitching moments generated by separated flow conditions induced by extremely high angles of attack.
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all moving active aerodynamic surface research
Smart Materials and Structures, 1995Co-Authors: Ron BarrettAbstract:The structural and aerodynamic characteristics of a new class of active flight control surface are presented. This new type of surface uses a symmetric, subsonic aerodynamic shell which is supported at the quarter-chord by a Main Spar and actively pitched by an adaptive torque-plate. The structural mechanics of the torque-plate and several actuator elements are detailed, including newly invented interdigitated electrode (IDE) and constrained directionally attached piezoelectric (CDAP) elements. Laminated plate models demonstrate that both generate similar deflections with comparable torsional stiffness. An experimental torque-plate specimen constructed from PSI-5A-S2 piezoceramic shows high torsional deflections and stiffness as well as excellent correlation with theory. The constrained torque-plate was integrated into a 12.5 cm span *5 cm chord adaptive missile fin which was designed for Mach 0.6 flight under standard conditions. The specimen showed static pitch deflections up to +or-8.1 degrees and dynamic deflections of +or-19 degrees at resonance. The active surface was also wind tunnel tested up to 40 m s-1 and demonstrated invariant pitch deflections as a function of airspeed, a steady break frequency of 50 Hz, no flutter, buffet or divergence tendencies and steady lift coefficient changes up to +or-0.51.
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all moving active aerodynamic surface research
Symposium on Active Materials and Smart Structures: Society of Engineering Science 31st Annual Meeting, 1995Co-Authors: Ron BarrettAbstract:The structural and aerodynamic characteristics of a new class of active flight control surface are presented. This new type of surface uses a symmetric, subsonic aerodynamic shell which is supported at the quarter-chord by a Main Spar and actively pitched by an adaptive torque- plate. The structural mechanics of the torque-plate and several actuator elements are detailed, including newly invented interdigitated electrode and constrained directionally attached piezoelectric elements. Laminated plate models demonstrate that both generate similar deflections with comparable torsional stiffnesses. An experimental torque-plate specimen constructed from PSI-5A-S2 piezoceramic shows high torsional deflections and stiffness as well as excellent correlation with theory. The constrained torque-plate was integrated into a 12.5 cm plan X 5 cm chord adaptive missile fan which was designed for Mach 0.6 flight under standard conditions. The specimen showed static pitch deflections up to +/- 8.1 degree(s) and dynamic deflections of +/- 19 degree(s) at resonance. The active surface was also wind tunnel tested up to 40 m/s and demonstrated invariant pitch deflections as a function of airspeed, a steady break frequency of 50 Hz, no flutter, buffet or divergence tendencies and steady lift coefficient changes up to +/- 0.51.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Roelof Vos - One of the best experts on this subject based on the ideXlab platform.
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post buckled precompressed subsonic micro flight control actuators and surfaces
Smart Materials and Structures, 2008Co-Authors: Ron Barrett, Roelof VosAbstract:This paper describes a new class of flight control actuators using Post-Buckled Precompressed (PBP) piezoelectric elements to provide much improved actuator performance. These PBP actuator elements are modeled using basic large deflection Euler-beam estimations accounting for laminated plate effects. The deflection estimations are then coupled to a high rotation kinematic model which translates PBP beam bending to stabilator deflections. A test article using PZT-5H piezoceramic sheets built into an active bender element was fitted with an elastic band which induced much improved deflection levels. Statically the bender element was capable of producing unloaded end rotations on the order of ±2.6°. With axial compression, the end deflections were shown to increase nearly 4-fold. The PBP element was then fitted with a graphite-epoxy aeroshell which was designed to pitch around a tubular stainless steel Main Spar. Quasi-static bench testing showed excellent correlation between theory and experiment through ±25° of pitch deflection. Finally, wind tunnel testing was conducted at airspeeds up to 120kts (62m/s, 202ft/s). Testing showed that deflections up through ±20° could be Maintained at even the highest flight speed. The stabilator showed no flutter or divergence tendencies at all flight speeds. At higher deflection levels, it was shown that a slight degradation deflection was induced by nose-down pitching moments generated by separated flow conditions induced by extremely high angles of attack.
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post buckled precompressed pbp subsonic micro flight control actuators and surfaces
The 14th International Symposium on: Smart Structures and Materials & Nondestructive Evaluation and Health Monitoring, 2007Co-Authors: Ron Barrett, Roelof Vos, Roeland De BreukerAbstract:This paper describes a new class of flight control actuators using Post-Buckled Precompressed (PBP) piezoelectric elements to provide much improved actuator performance. These PBP actuator elements are modeled using basic large deflection Euler-beam estimations accounting for laminated plate effects. The deflection estimations are then coupled to a high rotation kinematic model which translates PBP beam bending to stabilator deflections. A test article using PZT-5H piezoceramic sheets built into an active bender element was fitted with an elastic band which induced much improved deflection levels. Statically the bender element was capable of producing unloaded end rotations on the order of ±2.6°. With axial compression, the end deflections were shown to increase nearly 4-fold. The PBP element was then fitted with a graphite-epoxy aeroshell which was designed to pitch around a tubular stainless steel Main Spar. Quasi-static bench testing showed excellent correlation between theory and experiment through ±25° of pitch deflection. Finally, wind tunnel testing was conducted at airspeeds up to 120kts (62m/s, 202ft/s). Testing showed that deflections up through ±20° could be Maintained at even the highest flight speed. The stabilator showed no flutter or divergence tendencies at all flight speeds. At higher deflection levels, it was shown that a slight degradation deflection was induced by nose-down pitching moments generated by separated flow conditions induced by extremely high angles of attack.
Erik Lund - One of the best experts on this subject based on the ideXlab platform.
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dmto a method for discrete material and thickness optimization of laminated composite structures
Structural and Multidisciplinary Optimization, 2014Co-Authors: Soren Norgaard Sorensen, Rene Sorensen, Erik LundAbstract:This paper presents a gradient based topology optimization method for Discrete Material and Thickness Optimization of laminated composite structures, labelled the DMTO method. The capabilities of the proposed method are demonstrated on mass minimization, subject to constraints on the structural criteria; buckling load factors, eigenfrequencies, and limited displacements. Furthermore, common design guidelines or rules, referred to as manufacturing constraints, are included explicitly in the optimization problem as series of linear inequalities. The material selection and thickness variation are optimized simultaneously through interpolation functions with penalization. Numerical results for several parameterizations of a finite element model of a generic Main Spar from a wind turbine blade are presented. The different parameterizations represent different levels of complexity with respect to manufacturability. The results will thus give insight into the relation between potential weight saving and design complexity. The results show that the DMTO method is capable of solving the problems robustly with only few intermediate valued design variables.
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on structural optimization of composite shell structures using a discrete constitutive parametrization
Wind Energy, 2005Co-Authors: Erik Lund, Joachim StegmannAbstract:In this article a novel method for structural optimization of laminated composite shell structures such as wind turbine blades is presented. The outer shape of a wind turbine blade is typically determined by aerodynamic considerations and therefore not subject to change. Furthermore, the thicknesses of the shell structures are also considered fixed. The design objective is chosen to be a global quantity such as maximum stiffness or lowest eigenfrequency with a constraint on the total mass, such that the cost of material can be considered. The design optimization method is based on ideas from multiphase topology optimization where the material stiffness (or density) is computed as a weighted sum of candidate materials, and the method is easy to implement in existing finite element codes. The potential of the method to solve the combinatorial problem of proper choice of material, stacking sequence and fibre orientation simultaneously for maximum stiffness or lowest eigenfrequency design is illustrated on both small test examples and a real-life Main Spar from a wind turbine blade. Copyright © 2004 John Wiley & Sons, Ltd.
Kim Branner - One of the best experts on this subject based on the ideXlab platform.
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the effect of delaminations on local buckling in wind turbine blades
Renewable Energy, 2016Co-Authors: Philipp Ulrich Haselbach, Robert Bitsche, Kim BrannerAbstract:In this article the effect of delaminations on the load carrying capacity of a large wind turbine blade is studied numerically. For this purpose an 8.65 m long blade section with different initial delaminations in the Main Spar was subjected to a flapwise dominated bending moment. The model was setup in Abaqus and cohesive elements were chosen for modelling delamination growth.
Philipp Ulrich Haselbach - One of the best experts on this subject based on the ideXlab platform.
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the effect of delaminations on local buckling in wind turbine blades
Renewable Energy, 2016Co-Authors: Philipp Ulrich Haselbach, Robert Bitsche, Kim BrannerAbstract:In this article the effect of delaminations on the load carrying capacity of a large wind turbine blade is studied numerically. For this purpose an 8.65 m long blade section with different initial delaminations in the Main Spar was subjected to a flapwise dominated bending moment. The model was setup in Abaqus and cohesive elements were chosen for modelling delamination growth.
