Control of Static Shape, Dynamic Oscillation, and Thermally Induced Vibration of Nozzles

2005 ◽  
Vol 128 (3) ◽  
pp. 357-363 ◽  
Author(s):  
D. W. Wang ◽  
H. S. Tzou ◽  
S. M. Arnold ◽  
H.-J. Lee
Keyword(s):  
Finite Element ◽  
Conical Shell ◽  
Shape Control ◽  
Numerical Data ◽  
Analysis Data ◽  
Mode Shapes ◽  
Thermal Excitation ◽  
Thermally Induced ◽  
Control Effectiveness ◽  
And Control

Static shape actuation and dynamic control of nozzles can improve their performance, accuracy, reliability, etc. A new curved laminated piezothermoelastic hexahedral finite element is formulated based on the layerwise constant shear angle theory and it is used for modeling and analysis of piezothermoelastic conical shell structures subjected to control voltages for static shape actuation and dynamically and thermally induced vibration controls. Free vibration characteristics of an elastic truncated conical shell nozzle with fixed-free boundary conditions are studied using the new finite element. Both frequencies and mode shapes are accurately computed and compared favorably with available experimental and other numerical data. This study is then extended to evaluate control effectiveness of the conical shell with laminated piezoelectric layers. Static shape control is achieved by an applied electric potential. Vibration sensing and control are carried out using the negative velocity control scheme. Control of thermal excitation is also investigated. Analysis data suggest that the dynamic behavior and control characteristics of conical shells are quite complicated due to the coupled membrane and bending effects participating in the responses. To improve control effectiveness, segmentation and/or shaping of sensor and actuator layers need to be further investigated.

Control of Static Shape, Dynamic Oscillation, and Thermally Induced Vibration of Nozzles

Aerospace ◽  
2003 ◽  
Author(s):  
D. W. Wang ◽  
H. S. Tzou ◽  
S. M. Arnold
Keyword(s):  
Finite Element ◽  
Conical Shell ◽  
Shape Control ◽  
Numerical Data ◽  
Analysis Data ◽  
Mode Shapes ◽  
Thermal Excitation ◽  
Thermally Induced ◽  
Control Effectiveness ◽  
And Control

Static shape actuation and dynamic control of nozzles can optimize their performance, accuracy, reliability, etc. A new curved laminated piezothermoelastic hexahedral finite element is formulated based on the layerwise constant shear angle theory and it is used for modeling and analysis of piezothermoelastic conical shell structures subjected to control voltages for static shape actuation, dynamic and thermally-induced vibration controls. Free vibration characteristics of an elastic truncated conical shell nozzle with fixed-free boundary conditions are studied using the new finite element. Both frequencies and mode shapes are accurately computed and compared favorably with the experimental and other numerical data. This study is then extended to evaluate control effectiveness of the conical shell with laminated piezoelectric layers. Static shape control is achieved by an applied electric potential. Vibration sensing and control are carried out using the negative velocity control scheme. Control of thermal excitation is also investigated. Analysis data suggests that the dynamic behavior and control characteristics of conical shells are quite complicated due to the coupled membrane and bending effects participating in the responses. To improve control effectiveness, segmentation and/or shaping of sensor and actuator layers need to be further investigated.

Free Vibration Characteristics of Sandwich Conical Shells With FGM Face Sheets: A Finite Element Approach

2019 ◽  
Author(s):  
Tripuresh Deb Singha ◽  
Apurba Das ◽  
Gopal Agarwal ◽  
Tanmoy Bandyopadhyay ◽  
Amit Karmakar
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Free Vibration ◽  
Conical Shell ◽  
Vibration Characteristics ◽  
Mode Shapes ◽  
Iteration Algorithm ◽  
Operational Life ◽  
Sandwich Type ◽  
Element Method

Abstract This paper presents an analytical investigation on the free vibration characteristics of symmetric sandwich conical shell with functionally graded material (FGM) face sheets using finite element method. Sandwich-type structures offer higher stiffness to weight ratio with excellent thermal barrier in high temperature application extending the operational life of the component. The sandwich-type conical structure used in the advanced supersonic and hypersonic space vehicles. The material properties of FGM face sheets are considered to be varied in thickness direction as per simple power law distribution in terms of the volume fractions of the FGM constituents. The core layer is considered as homogeneous and made of an isotropic material (Titanium alloy-Ti–6Al–4V). A finite element method is used to reduce the governing equations of vibration problem. The QR iteration algorithm used to solve the standard eigen value problem for determine the natural frequencies. Convergence studies are performed in respect of mesh sizes to substantiate the accuracy of the proposed method. Computer codes developed to obtain the numerical results for the combined effects of twist angle and rotational speed on the free vibration characteristics of symmetric sandwich conical shell with FGM face sheets. A detailed numerical study is carried out to examine the influence of the sandwich plate type, volume fraction index on the free vibration characteristics. The typical mode shapes are also illustrated for different cases.

Free vibration response of carbon nanotube reinforced pretwisted conical shell under thermal environment

2019 ◽  
Vol 234 (3) ◽  
pp. 770-783 ◽  
Author(s):  
Pabitra Maji ◽  
Mrutyunjay Rout ◽  
Amit Karmakar
Keyword(s):  
Carbon Nanotubes ◽  
Finite Element ◽  
Carbon Nanotube ◽  
Free Vibration ◽  
Conical Shell ◽  
Dynamic Equilibrium ◽  
Thermal Environment ◽  
Shear Deformation Theory ◽  
Functionally Graded ◽  
Mode Shapes

Finite element procedure is employed to analyze the free vibration characteristics of rotating functionally graded carbon nanotubes reinforced composite conical shell with pretwist under the thermal environment. In this paper, four types of carbon nanotube grading are considered, wherein the distribution of carbon nanotubes are made through the thickness direction of the conical shell. An eight-noded isoparametric shell element is used in the present formulation to model the panel based on the first-order shear deformation theory. For moderate rotational speeds, the generalized dynamic equilibrium equation is derived from Lagrange’s equation of motion, neglecting the Coriolis effect. The finite element code is developed to investigate the effect of twist angle, temperature, aspect ratio, and rotational speed on natural frequencies. The mode shapes of a carbon nanotube reinforced functionally graded conical shell at different twist angles and rotational speeds are also presented.

FEM Analysis of a Diesel Engine’s Cylinder Head

2012 ◽  
Vol 490-495 ◽  
pp. 3023-3026
Author(s):  
Shao Zhong Jiang
Keyword(s):  
Finite Element ◽  
Modal Analysis ◽  
Cylinder Head ◽  
High Speed ◽  
Structural Characteristics ◽  
Fem Analysis ◽  
Mode Shapes ◽  
Element Analysis ◽  
Frequency Distributions ◽  
And Control

The article aims at the cylinder head used in a high speed and higher-power diesel engine. In order to obtain the vibration characteristics and vibration frequency distributions. By means of modal analysis technology and finite element method (FEM), structural characteristics of the cylinder head using modal analysis is investigated. Firstly, a physical model of the cylinder head is built. Through the comparison of all the modal analysis results with different meshing densities, a tetrahedron ten-node element with length of 30mm is selected. Then finite element analysis of the model is taken by FEM software. The cylinder head’s modal parameters namely its natural frequency are calculated and its mode shapes are identified. The results can provide basis for the engine’s dynamic analysis and control of the diesel engine’s noise

Dynamic Characteristics of Inflatable Reflectors with Consideration of Assembly of Gores

2016 ◽  
Vol 16 (01) ◽  
pp. 1640003
Author(s):  
Bing Bing San ◽  
Li Wei Yin ◽  
Zhao Quan Zhu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Dynamic Characteristics ◽  
Iteration Method ◽  
Shape Control ◽  
Natural Frequencies ◽  
Nonlinear Finite Element ◽  
Mode Shapes ◽  
Nonlinear Finite Element Method ◽  
Subspace Iteration

This paper focuses on the dynamic characteristics of reflectors considering the effects of assembly of gores. A model is established to properly predict the assembled shape of planar gores, and nonlinear finite element method and subspace iteration method are adopted to analyze the dynamic characteristics of reflectors. A comparative study is carried out based on the dynamic analysis with ideal reflector and assembled reflector to illustrate the impacts of assembly on mode shapes and natural frequencies of the reflectors. The results show that the presence of assembly of gores and seaming tapes has significant effects on mode shapes and natural frequencies of reflectors, which will influence the shape control of reflectors.

scholarly journals An investigation into the free vibration analysis of intact and defective laminated coposite beams subjected to combined axial force and end moment

2021 ◽  
Author(s):  
Mir Tahmaseb T. Kashani
Keyword(s):  
Finite Element ◽  
Free Vibration ◽  
Axial Force ◽  
Free Vibration Analysis ◽  
Numerical Data ◽  
Mode Shapes ◽  
Future Research ◽  
Frequency Dependent ◽  
Advantages And Disadvantages ◽  
Free Mode

This research is focusing on the bending-torsion coupled free vibration modeling as well as the analysis of intact and defective pre-stressed beams subjected to combined axial force and end moment. In the recent years, many studies have been conducted in an attempt to investigate the free vibration of pre-stressed beams using numerical and analytical techniques. However, despite their numerous applications, there is limited research done on pre-stressed beams subjected to both axial force and end moment in addition to the coupled behavior caused by the latter one. In the present study, current trends in the literature are critically examined, new models are proposed, and numerical and semi-analytical formulations are developed to find the natural frequencies and mode shapes of different pre-stressed slender beam configurations. The proposed methods are compared in terms of accuracy and convergence. Furthermore, the effects of axial force, end moment and delamination defect on the vibrational behavior of each model are also investigated. Four different general types of thin beams, including isotropic, layered, composite and delaminated beams, are modeled using traditional Finite Element Method (FEM) and frequency-dependent Dynamic Finite Element (DFE) technique. The DFE formulation is distinct from the conventional FEM by the fact that the former exploits frequency-dependent basis and shape functions of approximation space, whereas the polynomial ones are used in the latter method. With regard to layered beams, a novel layer-wise method is introduced for both DFE and FEM. Delaminated beam is also modeled using both ‘free mode’ and ‘constrained mode’ models showing that the continuity (both kinematic and force) conditions at delamination tips, in particular, play a large role in formulation of ‘free mode’ model. In this case, the defect is assumed to be a single-symmetric through the thickness delamination. However, the presented models and formulations could be readily extended to more general cases. Where available, the results were validated against existing limited experimental, analytical, and numerical data in literature. In addition, the investigated cases are modeled in the commercial finite element suite ANSYS® for further validation. Finally, general concluding remarks are made on the performance of the presented models and solution techniques, where the advantages and disadvantages of the proposed formulations as well as possible future research works are highlighted.

Experimental and Numerical Analysis of Read/Write Head Suspension Dynamics for High-Performance Floppy Drive Systems

1990 ◽  
Vol 112 (1) ◽  
pp. 26-32 ◽  
Author(s):  
G. M. Frees ◽  
D. K. Miu
Keyword(s):  
Finite Element ◽  
Numerical Analysis ◽  
High Performance ◽  
Laser Doppler Vibrometer ◽  
Numerical Data ◽  
Floppy Disk ◽  
Element Model ◽  
Operating Conditions ◽  
Tracking Performance ◽  
Mode Shapes

Read/write head suspensions are critical components of high-performance floppy disk drives. Their dynamics affect head/media compliance, wear, and tracking performance. Vibration measurements are necessary in order to verify and adjust finite element models, to observe the influence of actual loading and operating conditions, and to study the effects of unmodeled components such as electrical wires and adhesives. A nonintrusive measurement technique using a Laser Doppler Vibrometer is utilized to measure the submicron vibrations. Excitation of the suspension is provided by a specially designed miniature air hammer and a piezoelectric transducer. Natural frequencies and mode shapes are extracted from the measurements and compared with numerical data from the finite element model. Research shows that boundary conditions are the most important parameters in the modeling of the suspension. A new design is proposed, using the verified model, to increase the tracking performance of the suspension. Synergy between experimentation and numerical analysis is emphasized.

scholarly journals Simultaneous Piezoelectric Actuator and Sensor Placement Optimization and Control Design of Manipulators with Flexible Links Using SDRE Method

2010 ◽  
Vol 2010 ◽  
pp. 1-23 ◽  
Author(s):  
Alexandre Molter ◽  
Otávio A. Alves da Silveira ◽  
Jun S. Ono Fonseca ◽  
Valdecir Bottega
Keyword(s):  
Finite Element ◽  
Piezoelectric Actuator ◽  
Control Design ◽  
Piezoelectric Actuators ◽  
Mode Shapes ◽  
Nonlinear Feedback ◽  
Lagrange Equations ◽  
State Dependent ◽  
Optimization And Control ◽  
And Control

This paper presents a control design for flexible manipulators using piezoelectric actuators bonded on nonprismatic links. The dynamic model of the manipulator is obtained in a closed form through the Lagrange equations. Each link is discretized using finite element modal formulation based on Euler-Bernoulli beam theory. The control uses the motor torques and piezoelectric actuators for controlling vibrations. An optimization problem with genetic algorithm (GA) is formulated for the location and size of the piezoelectric actuator and sensor on the links. The natural frequencies and mode shapes are computed by the finite element method, and the irregular beam geometry is approximated by piecewise prismatic elements. The State-Dependent Riccati Equation (SDRE) technique is used to derive a suboptimal controller for a robot control problem. A state-dependent equation is solved at each new point obtained for the variables from the problem, along the trajectory to obtain a nonlinear feedback controller. Numerical tests verify the efficiency of the proposed optimization and control design.

Modeling and Control of a Morphing Airfoil

2003 ◽  
Author(s):  
Christopher E. Whitmer ◽  
Atul G. Kelkar ◽  
Phuc Vu ◽  
Frank R. Chavez
Keyword(s):  
Finite Element ◽  
Dynamic Model ◽  
Structural Model ◽  
Linear Time ◽  
Mode Shapes ◽  
Morphing Wing ◽  
Structural Dynamic ◽  
Finite Dimensional ◽  
Aeroelastic Model ◽  
And Control

This paper presents aeroelastic modelling and robust control design for a morphing airfoil concept. A finite dimensional linear time invariant aeroelastic model is developed for a multi-input multi-output morphing airfoil structure. The shape of the airfoil (NACA airfoil series 2415) is controlled by actuators distributed along the top airfoil surface that produce vertical deflections of the top surface at several locations. This results in an airfoil shape change (i.e., “morphing” of the wing), which causes changes in the aerodynamic loading on the wing. The objective is to control the deformation of the airfoil in realtime so as to achieve the desirable aerodynamic forces on the wing. The structural model is developed using the finite element approach. A finite element toolbox in Matlab, namely FEMLAB, is used to obtain eigenfrequencies and mode shapes. A finite dimensional dynamic model of the structure is obtained by the assumed modes method. A static aerodynamic model is developed with a vortex lattice method and coupled with the structural dynamic model to yield a linear aeroelastic model of the morphing wing. A robust LQG design is presented for tracking the commanded lift and roll moment. Some parametric studies are also presented for the choice of different materials. Simulation results are given to demonstrate the viability of the proposed modelling and control methodology for morphing wing concept.

scholarly journals An investigation into the free vibration analysis of intact and defective laminated coposite beams subjected to combined axial force and end moment

2021 ◽  
Author(s):  
Mir Tahmaseb T. Kashani
Keyword(s):  
Finite Element ◽  
Free Vibration ◽  
Axial Force ◽  
Free Vibration Analysis ◽  
Numerical Data ◽  
Mode Shapes ◽  
Future Research ◽  
Frequency Dependent ◽  
Advantages And Disadvantages ◽  
Free Mode

This research is focusing on the bending-torsion coupled free vibration modeling as well as the analysis of intact and defective pre-stressed beams subjected to combined axial force and end moment. In the recent years, many studies have been conducted in an attempt to investigate the free vibration of pre-stressed beams using numerical and analytical techniques. However, despite their numerous applications, there is limited research done on pre-stressed beams subjected to both axial force and end moment in addition to the coupled behavior caused by the latter one. In the present study, current trends in the literature are critically examined, new models are proposed, and numerical and semi-analytical formulations are developed to find the natural frequencies and mode shapes of different pre-stressed slender beam configurations. The proposed methods are compared in terms of accuracy and convergence. Furthermore, the effects of axial force, end moment and delamination defect on the vibrational behavior of each model are also investigated. Four different general types of thin beams, including isotropic, layered, composite and delaminated beams, are modeled using traditional Finite Element Method (FEM) and frequency-dependent Dynamic Finite Element (DFE) technique. The DFE formulation is distinct from the conventional FEM by the fact that the former exploits frequency-dependent basis and shape functions of approximation space, whereas the polynomial ones are used in the latter method. With regard to layered beams, a novel layer-wise method is introduced for both DFE and FEM. Delaminated beam is also modeled using both ‘free mode’ and ‘constrained mode’ models showing that the continuity (both kinematic and force) conditions at delamination tips, in particular, play a large role in formulation of ‘free mode’ model. In this case, the defect is assumed to be a single-symmetric through the thickness delamination. However, the presented models and formulations could be readily extended to more general cases. Where available, the results were validated against existing limited experimental, analytical, and numerical data in literature. In addition, the investigated cases are modeled in the commercial finite element suite ANSYS® for further validation. Finally, general concluding remarks are made on the performance of the presented models and solution techniques, where the advantages and disadvantages of the proposed formulations as well as possible future research works are highlighted.

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