scholarly journals Vibration Analysis of Radial Compressor Impellers

1983 ◽  
Author(s):  
J. Wachter ◽  
H. Celikbudak
Keyword(s):  
Dynamic Behavior ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Design Parameters ◽  
Centrifugal Impeller ◽  
Structural Dynamic ◽  
Experimental Procedure ◽  
Radial Compressor ◽  
Comparison Of The Results ◽  
Important Design

There are many problems facing the designers of turbomachines with the demand for ever increasing capabilities and reliability. One problem that requires considerable attention is the vibration characteristics of some components. It is object of this work to determine the dynamic behavior, namely natural frequencies, mode shapes of a centrifugal impeller which are being important design parameters in order to avoid costly failures in the development phase. This work divides into three sections. First, a Finite Element structural dynamic analysis is presented. Then experimental procedure used to determine the natural frequencies and mode shapes is described together with the comparison of the results obtained both theoretically through FEM and experimentally. Finally, interferometric holography technique is used as a means for obtaining the dynamic behavior of the impeller.

scholarly journals Spatially Resolved Experimental Modal Analysis on High-Speed Composite Rotors Using a Non-Contact, Non-Rotating Sensor

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4705
Author(s):  
Julian Lich ◽  
Tino Wollmann ◽  
Angelos Filippatos ◽  
Maik Gude ◽  
Juergen Czarske ◽  
...  
Keyword(s):  
High Speed ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Fiber Reinforced ◽  
Structural Dynamic ◽  
Spatially Resolved ◽  
Glass Fiber Reinforced ◽  
Vibration Responses ◽  
And Performance

Due to their lightweight properties, fiber-reinforced composites are well suited for large and fast rotating structures, such as fan blades in turbomachines. To investigate rotor safety and performance, in situ measurements of the structural dynamic behaviour must be performed during rotating conditions. An approach to measuring spatially resolved vibration responses of a rotating structure with a non-contact, non-rotating sensor is investigated here. The resulting spectra can be assigned to specific locations on the structure and have similar properties to the spectra measured with co-rotating sensors, such as strain gauges. The sampling frequency is increased by performing consecutive measurements with a constant excitation function and varying time delays. The method allows for a paradigm shift to unambiguous identification of natural frequencies and mode shapes with arbitrary rotor shapes and excitation functions without the need for co-rotating sensors. Deflection measurements on a glass fiber-reinforced polymer disk were performed with a diffraction grating-based sensor system at 40 measurement points with an uncertainty below 15 μrad and a commercial triangulation sensor at 200 measurement points at surface speeds up to 300 m/s. A rotation-induced increase of two natural frequencies was measured, and their mode shapes were derived at the corresponding rotational speeds. A strain gauge was used for validation.

Split Vibration Modes in Acoustically-Coupled Disk Stacks

1995 ◽  
Author(s):  
Jung-Ge Tseng ◽  
Jonathan Wickert
Keyword(s):  
Natural Frequencies ◽  
Three Dimensional ◽  
System Level ◽  
Thin Plates ◽  
Mode Shapes ◽  
Design Parameters ◽  
Phase System ◽  
Acoustic Coupling ◽  
Annular Plates ◽  
Vibration Model

Abstract Vibration of an array of stacked annular plates, in which adjacent plates couple weakly through an acoustic layer, is investigated through experimental and theoretical methods. Such acoustic coupling manifests itself through split natural frequencies, beating in the time responses of adjacent or separated plates, and system-level modes in which plates in the array vibrate in- or out-of-phase at closely-spaced frequencies. Laboratory measurements, including a technique in which the frequency response function of all in-phase modes but no out-of-phase modes, or visa versa, is measured, demonstrate the contribution of coupling to the natural frequency spectrum, and identify the combinations of design parameters for which it is important. For the lower modes of primary interest here, the natural frequencies of the out-of-phase system modes decrease as the air layer becomes thinner, while those of the in-phase mode remain sensibly constant at the in vacuo values. A vibration model comprising N classical thin plates that couple through the three-dimensional acoustic fields established in the annular cavities between plates is developed, and its results are compared with measurements of the natural frequencies and mode shapes.

Mechanical Behavior of an Electrostatically Actuated Microplate

2003 ◽  
Author(s):  
Xiaopeng Zhao ◽  
Eihab M. Abdel-Rahman ◽  
Ali H. Nayfeh
Keyword(s):  
Differential Equations ◽  
Natural Frequencies ◽  
Finite Dimension ◽  
Equations Of Motion ◽  
Galerkin Approximation ◽  
Mode Shapes ◽  
Design Parameters ◽  
Electrostatically Actuated ◽  
Linear Eigenvalue Problem ◽  
Electrically Actuated

We present a nonlinear model of electrically actuated microplates. The model accounts for the nonlinearity in the electric forcing as well as mid-plane stretching of the plate. We use a Galerkin approximation to reduce the partial-differential equations of motion to a finite-dimension system of nonlinearly coupled second-order ordinary-differential equations. We find the deflection of the microplate under DC voltage and study the pull-in phenomenon. The natural frequencies and mode shapes are then obtained around the deflected position of the microplate by solving the linear eigenvalue problem. The effect of various design parameters on both the static response and the dynamic characteristics are studied.

scholarly journals Model Updating of Friction Stir Welding for Aluminium and Magnesium Plate Structure

2018 ◽  
Vol 150 ◽  
pp. 04004 ◽  
Author(s):  
Nazrotul Afina Nazri ◽  
Mohd Shahrir Mohd Sani ◽  
Muhammad Nasiruddin Mansor ◽  
Siti Norazila Zahari
Keyword(s):  
Friction Stir Welding ◽  
Natural Frequencies ◽  
Model Updating ◽  
Mode Shapes ◽  
Average Error ◽  
Element Analysis ◽  
Structural Dynamic ◽  
Friction Stir ◽  
Dissimilar Friction Stir Welding ◽  
Al 7075

Friction stir welding (FSW) of aluminium and magnesium alloys face high demands in automotive and aerospace application due to its advanced and lightweight properties. FSW is an emerging solid state joining process in which the material that is being welded does not melt and recast. The main objectives of this project are to perform model updating based on finite element analysis (FEA) and experimental modal analysis (EMA) of dissimilar material of aluminium alloy AL 7075 and magnesium alloy AZ 31B. Modal properties such as natural frequencies, mode shapes are obtained and compared between FEA and EMA. The discrepancies of first five modes natural frequencies are below than 10% and the model updating have been conducted to minimize the error between two methods. This model updating are based on sensitivity analysis in order to make sure which parameters are given more influence in this structural dynamic analysis. Young’s modulus and Poisson’s ratio both materials are selected in the model updating process. After perform model updating, total average error of the natural frequencies of dissimilar friction stir welding plate is improved significantly.

In vivo structural dynamic analysis of the dragonfly wing: the effect of stigma as its modulator

2019 ◽  
Vol 377 (2150) ◽  
pp. 20190132 ◽  
Author(s):  
Amit Kumar ◽  
Navin Kumar ◽  
Rakesh Das ◽  
Piyush Lakhani ◽  
Bharat Bhushan
Keyword(s):  
Drag Coefficient ◽  
Natural Frequencies ◽  
Leading Edge ◽  
Micro Air Vehicles ◽  
Active Role ◽  
Image Correlation ◽  
Mode Shapes ◽  
Correlation Technique ◽  
Structural Dynamic

The flapping of the dragonfly forewing under in vivo condition has been analysed by image correlation technique to get an insight of its structural dynamics. The modal parameters such as flapping frequency, natural frequencies, mode shapes and modal strain have been obtained that will facilitate the biomimetic design of wings for micro air vehicles. The stigma, which is a pigmented spot at the leading edge of the wing near the tip having heavier mass, takes an active role in the real-time flapping by shaping its trajectory as eight-shaped, which enhances the drag coefficient and stroke efficiency. The extra mass on it and its removal transformed the trajectory into two different elliptical and oval shapes, respectively, which reduced the drag coefficient and stroke efficiency of the flapping wing by altering the flapping kinematics. This article is part of the theme issue ‘Bioinspired materials and surfaces for green science and technology (part 2)’.

INVESTIGATION OF DYNAMIC PROPERTIES OF ELASTOMERIC BEARING COMPONENTS VIA MODAL ANALYSIS

2015 ◽  
Vol 76 (8) ◽  
Author(s):  
A. I. Yusuf ◽  
M. A. Norliyati ◽  
M. A. Yunus ◽  
M. N. Abdul Rani
Keyword(s):  
Modal Analysis ◽  
Dynamic Behavior ◽  
Natural Frequencies ◽  
Dynamic Properties ◽  
Experimental Modal Analysis ◽  
Mode Shapes ◽  
Seismic Loads ◽  
Ground Structure ◽  
Elastomeric Bearing ◽  
Earthquake Load

Elastomeric bearing is a significant device in structures such as in bridges and buildings. It is used to isolate the ground structure (substructure) and the above ground structure (superstructure) from seismic loads such as earthquake load. Understanding the dynamic behavior of the elastomeric bearing in terms of natural frequencies, mode shapes and damping are increasingly important especially in improving the design and the failure limit of the elastomeric bearing. Modal analysis is one of the methods used to determine the dynamic properties of any materials. Hence, the main objective of this research is to determine the dynamic properties of elastomeric bearing components in terms of natural frequencies, mode shapes, and damping via numerical and experimental modal analysis. This method had been successfully performed in investigating the dynamic behavior of rubber and steel shim plate.

Multi-Junction, Multi-Branch Torsional Vibration in a Geared Rotating System

2000 ◽  
Author(s):  
Qing Ke Yuan ◽  
David Y. Yao
Keyword(s):  
Torsional Vibration ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Design Stage ◽  
Design Parameters ◽  
Analysis Program ◽  
Vibration System ◽  
Rotating System ◽  
Steel Rolling ◽  
Mining Machinery

Abstract A multi-junction, multi-branch torsional vibration system is often found in a geared rotating system. This is an important part in many types of machinery, such as mining machinery, petroleum machinery, steel rolling machinery and automobiles. If the design parameters of the system are improper, there will be serious torsional vibration, which will cause noticeable sound disturbances, severe shakings, and component fatigue problems. Analyzing and pre-estimating critical speeds or torsional natural frequencies and mode shapes of the vibration systems in the design stage is very important to avoid future disastrous and costly repairs of the machinery. In this paper, a radical and effective method for calculating natural frequencies and mode shapes of multi-junction, multi-branch torsional vibration systems, has been put forward, a program named MJBTVAP (Multi-Junction, multi-Branch Torsional Vibration Analysis Program) based on this method has been developed, actual problems have been solved.

A Parametrization Describing Blisk Airfoil Variations Referring to Modal Analysis

2017 ◽  
Author(s):  
Thomas Backhaus ◽  
Thomas Maywald ◽  
Sven Schrape ◽  
Matthias Voigt ◽  
Ronald Mailach
Keyword(s):  
Modal Analysis ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Design Parameters ◽  
Surface Mesh ◽  
Main Mode ◽  
Airfoil Surface ◽  
Parametrization Method ◽  
Surface Meshes ◽  
Geometric Variation

This paper will present a way to capture the geometric blade by blade variations of a milled from solid blisk as well as the manufacturing scatter. Within this idea it is an essential task to digitize the relevant airfoil surface as good as possible to create a valid surface mesh as the base of the upcoming evaluation tasks. Since those huge surface meshes are not easy to handle and are even worse in getting quantified and easy interpretable results, it should be aimed for an easily accessible way of presenting the geometric variation. The presented idea uses a section based airfoil parametrization that is based on an extended NACA-airfoil structure to ensure the capturing of all occurring characteristic geometry variations. This Paper will show how this adapted parametrization method is suitable to outline all the geometric blade by blade variation and even more, refer those airfoil design parameters to modal analysis results such as the natural frequencies of the main mode shapes. This way, the dependencies between the modal and airfoil parameters will be proven.

scholarly journals Structural Dynamic Improvement for Petal-Type Deployable Solid-Surface Reflector Based on Numerical Parameter Study

2020 ◽  
Vol 10 (18) ◽  
pp. 6560
Author(s):  
He Huang ◽  
Qiang Cheng ◽  
Lei Zheng
Keyword(s):  
Solid Surface ◽  
Dynamic Properties ◽  
Dynamic Performance ◽  
Dynamic Test ◽  
Mode Shapes ◽  
Design Parameters ◽  
Prototype Model ◽  
Parameter Study ◽  
Structural Dynamic ◽  
Replacement Method

Petal-type Deployable Solid-surface Reflector (PDSR) is a kind of important structure widely applied in deployable reflector antennas in aerospace engineering. The dynamic properties of this reflector structure in deployed state are significant to the reflector accuracy for antennas. However, the study of the dynamic evaluation of deployable structure with revolute joints is difficult and seldom concerned by researchers. In order to study dynamic properties of the PDSR, the Cable Replacement Method (CRM) was utilized to equivalently simulate the nonlinear structural stiffness of the revolute joint for numerical analyses. The Finite Element Model (FEM) of this reflector structure was established by commercial software ANSYS (ANSYS Inc., Canonsburg, PA, USA) and verified by the theoretical analysis and dynamic test of actual prototype model. The natural frequencies and mode shapes of deployed reflector were computed to study the influence of drag spring design parameters as stiffness, pre-tensioned force, and distance of two adjacent linkage butts. Finally, the analysis results were concluded that the drag springs between two adjacent petals can essentially improve the dynamic performance of reflector structure in deployed state. It can be a useful technical system for future engineering applications of PDSR antennas.

Fluid-Structure Coupling Between a Finite Cylinder and a Confined Fluid

1984 ◽  
Vol 51 (4) ◽  
pp. 857-862 ◽  
Author(s):  
G. Garner ◽  
S. Chandra
Keyword(s):  
Dynamic Behavior ◽  
Finite Length ◽  
Natural Frequencies ◽  
Finite Cylinder ◽  
Mode Shapes ◽  
Infinite Cylinder ◽  
Fluid Structure ◽  
Coupled Mode ◽  
Confined Fluid ◽  
Structure Equations

The dynamic behavior of a finite length cylindrical rod in a fluid filled annulus is considered. The fluid and structure equations are solved simultaneously, with fluid-structure coupling accounted for. Coupled mode shapes and natural frequencies are obtained for various cases. It is found that for short lengths and/or higher modes, the effect of the fluid on the cylinder motion diminishes compared to the infinite cylinder case. In addition, coupled and in-vacuum mode shapes can differ in certain cases.

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