A Constraint Function Technique for Improved Structural Dynamics

1986 ◽  
Vol 108 (1) ◽  
pp. 101-106 ◽  
Author(s):  
J. M. Starkey ◽  
J. E. Bernard
Keyword(s):  
Structural Dynamics ◽  
Natural Frequencies ◽  
Function Approach ◽  
Function Technique ◽  
Constraint Function ◽  
Frequency Bands ◽  
Design Changes

A constraint function approach is presented for finding design changes that remove natural frequencies from undesirable frequency bands for lightly damped structures. The technique requires the minimization of a function which becomes smaller when (1) natural frequencies clear out of undesirable bands, and (2) design changes become small. Useful forms of these functions are defined, and the number of possible minima is explored. Graphical intepretations of the constraint functions are given, and an example is included which shows the effects of the parameters which weight these two functions.

scholarly journals Using Pade´ Approximants and Curve-fitting to Approximate Eigenvalues and Eigenvectors for Large Design Changes

1996 ◽  
Vol 118 (1) ◽  
pp. 151-153 ◽  
Author(s):  
J. M. Vance ◽  
J. E. Bernard
Keyword(s):  
Finite Element ◽  
Natural Frequencies ◽  
Solution Process ◽  
Mode Shapes ◽  
Eigenvalues And Eigenvectors ◽  
Computational Burden ◽  
Design Change ◽  
Design Changes ◽  
Develop Software ◽  
Unique Method

Our overall goal is to develop software that facilitates the interactive participation of the designer in the optimization process. We are focusing this research on problems which use finite element solutions as part of the objective function. One challenge to implementing interactive participation in these types of problems is the high computational burden of computing a finite element solution for each design change. The research presented here focuses on a unique method to develop fast approximations for natural frequencies and mode shapes which can be used to avoid the time-consuming re-solution process and which will facilitate interactive design for systems with even large design changes.

scholarly journals Bellman function approach to the sharp constants in uniform convexity

2018 ◽  
Vol 11 (1) ◽  
pp. 89-93
Author(s):  
Paata Ivanisvili
Keyword(s):  
Uniform Convexity ◽  
Function Approach ◽  
Function Technique ◽  
Bellman Function ◽  
Sharp Constants

AbstractWe illustrate a Bellman function technique in finding the modulus of uniform convexity of {L^{p}} spaces.

Key Microwave and Millimeter Wave Technologies for 5G Radio

2018 ◽  
pp. 70-104
Author(s):  
Vojislav Milosevic ◽  
Branka Jokanovic ◽  
Olga Boric-Lubecke ◽  
Victor M. Lubecke
Keyword(s):  
Millimeter Wave ◽  
Wave Frequency ◽  
Professional Lives ◽  
Frequency Bands ◽  
Design Changes ◽  
Driverless Cars ◽  
The Future ◽  
Remote Healthcare ◽  
Antenna Systems ◽  
Simultaneous Transmission

This chapter presents an overview on the drivers behind the 5G evolution and explains technological breakthroughs in the microwave and millimeter wave domain that will create the 5G backbone. Extensions to millimeter wave frequency bands, advanced multi-antenna systems and antenna beamforming and simultaneous transmission and reception are some of the prospects that could lead to both architectural and component disruptive design changes in the future 5G. 5G is expected to include an innovative set of technologies that will radically change our private and professional lives, though applications of novel services, such as remote healthcare, driverless cars, wireless robots and connected homes, which will alter boundaries between the real and the cyber world.

scholarly journals A Novel Highly Accurate Finite-Element Family

2017 ◽  
Vol 2017 ◽  
pp. 1-20
Author(s):  
Giovanni Bernardini ◽  
Fabio Cetta ◽  
Luigi Morino
Keyword(s):  
Finite Element ◽  
Structural Dynamics ◽  
Hermite Interpolation ◽  
Natural Frequencies ◽  
Finite Thickness ◽  
Three Dimensional ◽  
Numerical Results ◽  
Small Thickness ◽  
Modes Of Vibration ◽  
Patch Technique

A novel Nth order finite element for interior acoustics and structural dynamics is presented, with N arbitrarily large. The element is based upon a three-dimensional extension of the Coons patch technique, which combines high-order Lagrange and Hermite interpolation schemes. Numerical applications are presented, which include the evaluation of the natural frequencies and modes of vibration of (1) air inside a cavity (interior acoustics) and (2) finite-thickness beams and plates (structural dynamics). The numerical results presented are assessed through a comparison with analytical and numerical results. They show that the proposed methodology is highly accurate. The main advantages however are (1) its flexibility in obtaining different level of accuracy (p-convergence) simply by increasing the number of nodes, as one would do for h-convergence, (2) the applicability to arbitrarily complex configurations, and (3) the ability to treat beam- and shell-like structures as three-dimensional small-thickness elements.

scholarly journals Discretized Lyapunov Function Approach for Switched Linear Systems under Dwell Time Constraint

2014 ◽  
Vol 2014 ◽  
pp. 1-10
Author(s):  
Yongchi Zhao ◽  
Shengxian Zhuang ◽  
Weiming Xiang ◽  
Lin Du
Keyword(s):  
Lyapunov Function ◽  
Dwell Time ◽  
Sufficient Conditions ◽  
Time Constraint ◽  
Switched System ◽  
Function Approach ◽  
Disturbance Attenuation ◽  
Function Technique ◽  
Synthesis Process ◽  
Control Synthesis

This paper is concerned with the stability and disturbance attenuation properties of switched linear system with dwell time constraint. A novel time-scheduled Lyapunov function is introduced to deal with the problems studied in this paper. To numerically check the existence of such time-scheduled Lyapunov function, the discretized Lyapunov function technique usually used in time-delay system is developed in the context of switched system in continuous-time cases. Based on discretized Lyapunov function, sufficient conditions ensuring dwell-time constrained switched system global uniformly asymptotically stable are established, then the disturbance attenuation properties in the sense ofL2gain are studied. The main advantage of discretized Lyapunov function approach is that the derived sufficient conditions are convex in subsystem matrices, which makes the analysis results easily used and generalized. Thus, theH∞control synthesis problem is considered. On the basis of analysis results in hand, the control synthesis procedures including both controller and switching law design are unified into one-step method which explicitly facilitates the control synthesis process. Several numerical examples are provided to illustrate the results within our paper.

Structural Dynamics and Load Analysis of Large Offshore Wind Turbines in Western Gulf of Mexico Shallow Water

2014 ◽  
Author(s):  
Ling Ling Yin ◽  
King Him Lo ◽  
Su Su Wang
Keyword(s):  
Gulf Of Mexico ◽  
Wind Turbine ◽  
Shallow Water ◽  
Structural Dynamics ◽  
Natural Frequencies ◽  
Offshore Wind ◽  
Normal Operation ◽  
Mode Shapes ◽  
Offshore Wind Turbine ◽  
Support Structure

In this paper, a study is conducted on wind and metocean loads and associated structural dynamics of a 13.2-MW large offshore wind turbine in Western Gulf of Mexico (GOM) shallow water. The offshore wind turbine considered includes a rotor with three 100-meter long blades and a mono-tower support structure. Natural frequencies and mode shapes of the blades and the mono-tower are determined first and used subsequently to establish a Campbell diagram for safe wind turbine operation. The results show that hydrodynamic added mass has little effect on the natural frequencies and mode shapes of the support structure but it introduces, in part, appreciable effects on loads carried by the turbine when the blades are pitched at wind speeds above the rated speed. Also determined, for normal operation and extreme metocean conditions (i.e., 100-year return hurricanes), are normal thrust on the wind rotor, blade-tip displacement, overturning moment and tower-top displacement sustained by the wind turbine.

scholarly journals An Evaluation of Material Properties Using EMA and FEM

2016 ◽  
Vol 24 (39) ◽  
pp. 15-22
Author(s):  
Rastislav Ďuriš ◽  
Eva Labašová
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Structural Dynamics ◽  
Material Properties ◽  
Elasticity Modulus ◽  
Natural Frequencies ◽  
Optimization Methods ◽  
Experimental Measurements ◽  
Element Analysis

Abstract The main goal of the paper is the determination of material properties from experimentally measured natural frequencies. A combination of two approaches to structural dynamics testing was applied: the experimental measurements of natural frequencies were performed by Experimental Modal Analysis (EMA) and the numerical simulations, were carried out by Finite Element Analysis (FEA). The optimization methods were used to determine the values of density and elasticity modulus of a specimen based on the experimental results.

Structural vibration design of a pod structure including an optical system of a fighter aircraft

2021 ◽  
Vol 263 (1) ◽  
pp. 5555-5561
Author(s):  
Taeyoung Yoon ◽  
Jaemyung Cho ◽  
Sungsoo Na ◽  
Seongho Yoon
Keyword(s):  
Structural Dynamics ◽  
Optical System ◽  
Natural Frequencies ◽  
Free Vibration Analysis ◽  
Structural Vibration ◽  
Mode Shapes ◽  
Element Analysis ◽  
Fighter Aircraft ◽  
Frequency Responses ◽  
Improving Accuracy

Structural vibration design of a pod structure including an optical system installed on a fighter aircraft is very significant in improving accuracy of targeting system to the target objects. To reduce and isolate the vibration generated during the flight, it is crucial to properly design the rubber mount between the pod and the aircraft. In this study, free vibration analysis of the pod is conducted through finite element analysis (FEA) and experiments. Correlations are performed with reasonably acceptable accuracy about the natural frequencies, mode shapes, and frequency response functions obtained by FEA and experiment. Then to optimize the structural dynamics of the pod, three variables are considered, which are mass of the dummies, the numbers of and positions of rubber mounts, and hyperelastic property of rubber mounts. In addition, the position of the pod on the fighter is analysed by FEM to estimate the possibility of further enhancement of its structural dynamics. Finally, forced vibration was undertaken using random signals of a shaker with 1Grms, 2Grms and 2.65Grms considering the test standard. It is found out that frequency responses of the pod are sensitive below 100 Hz to the values of the excitation signals. It is thus indeed to design appropriately the rubber mounts to improve structural dynamics of the pod, which results in the accuracy of targeting system.

Sign in / Sign up

Export Citation Format

Share Document