scholarly journals Analytical Study of Coupling Effects for Vibrations of Cable-Harnessed Beam Structures

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Karthik Yerrapragada ◽  
Armaghan Salehian
Keyword(s):  
Natural Frequencies ◽  
Strain Tensor ◽  
Linear Displacement ◽  
Analytical Models ◽  
Space Structures ◽  
Distributed Parameter ◽  
Element Analysis ◽  
Model Studies ◽  
The Finite Element Analysis ◽  
Lagrange Strain

This paper presents a distributed parameter model to study the effects of the harnessing cables on the dynamics of a host structure motivated by space structures applications. The structure is modeled using both Euler–Bernoulli and Timoshenko beam theories (TBT). The presented model studies the effects of coupling between various coordinates of vibrations due to the addition of the cable. The effects of the cable's offset position, pretension, and radius are studied on the natural frequencies of the system. Strain and kinetic energy expressions using linear displacement field assumptions and Green–Lagrange strain tensor are developed. The governing coupled partial differential equations for the cable-harnessed beam that includes the effects of the cable pretension are found using Hamilton's principle. The natural frequencies from the coupled Euler, Bernoulli, Timoshenko and decoupled analytical models are found and compared to the results of the finite element analysis (FEA).

Vibration Modelling of String-Harnessed Beam Structures Using Homogenization Techniques

2014 ◽  
Author(s):  
Blake Martin ◽  
Armaghan Salehian
Keyword(s):  
Continuum Model ◽  
Dynamic Behaviour ◽  
Natural Frequencies ◽  
Strain Tensor ◽  
Space Structures ◽  
Power Cables ◽  
Structural Elements ◽  
Equivalent Continuum Model ◽  
Lagrange Strain ◽  
Equivalent Continuum

Harnessing structural elements with strings, power cables, and signal cables increases the complexity in modelling the dynamic behaviour of such structures. Developing models capable of accurately predicting the dynamic behaviour of these systems is of great importance for space structures that cannot be tested prior to launch. The focus of this work is obtaining an equivalent continuum model for string-harnessed beam-like structures with periodic wrapping patterns. The tension in the string is assumed to vary as the beam deflects. The displacement field with second-order terms is determined and from which the Green-Lagrange strain tensor is obtained. After finding kinetic and potential energy expressions Hamilton’s principle is used to obtain the partial differential equation and boundary conditions. Numerical results for the shift in the natural frequencies are presented for various string properties to investigate their effects on the structure.

Continuum modeling and vibration analysis of cable-harnessed plate structures of periodic patterns

2021 ◽  
pp. 1-54
Author(s):  
Pranav Agrawal ◽  
Armaghan Salehian
Keyword(s):  
Materials Science ◽  
Strain Tensor ◽  
Linear Displacement ◽  
Periodic Patterns ◽  
Element Analysis ◽  
Plate Structures ◽  
Solid Plate ◽  
Homogenization Approach ◽  
Repeated Pattern ◽  
Lagrange Strain

Abstract Over the past decade, modeling of cable-harnessed space structures has received special attention due to the need for better accuracies than the existing models. As these structures become more lightweight upon the advancements in the materials science it is imperative to further consider accurate models in which the dynamic effects of the added cables are better accounted for. Researchers have heavily focused on creating models for cable-harnessed beam-like structures, while very few works have considered plate-like structures. The proposed research aims at the development of an analytical model for cable-harnessed plate-like structures. Cables are assumed to be periodic in geometry to allow for the application of an energy-equivalent homogenization technique. To begin with, a linear displacement field and a second-order Green-Lagrange strain tensor for strain-displacement relationships are considered. The strain and kinetic energies of the fundamental element are found using these relations. The repeated pattern of the fundamental element over the area of the plate structure allows for the employment of the homogenization approach in which the kinetic and strain energies per area of the fundamental element are found and assumed to remain the same as an equivalent homogenized solid plate-like element. The governing dynamic Partial Differential Equations (PDEs) are found using the Hamilton’s principle. The results are validated using finite element analysis. A detailed parametric analysis is also performed to investigate the effects of various cable parameters and wrapping patterns on the dynamics of the host structure.

Updating of Non-Conservative Systems Using Inverse Methods

1997 ◽  
Author(s):  
Ladislav Starek ◽  
Milos Musil ◽  
Daniel J. Inman
Keyword(s):  
Analytical Model ◽  
Degrees Of Freedom ◽  
Ad Hoc ◽  
Natural Frequencies ◽  
Eigenvalue Problems ◽  
Model Updating ◽  
Analytical Models ◽  
Mode Shapes ◽  
Element Analysis ◽  
Modal Data

Abstract Several incompatibilities exist between analytical models and experimentally obtained data for many systems. In particular finite element analysis (FEA) modeling often produces analytical modal data that does not agree with measured modal data from experimental modal analysis (EMA). These two methods account for the majority of activity in vibration modeling used in industry. The existence of these discrepancies has spanned the discipline of model updating as summarized in the review articles by Inman (1990), Imregun (1991), and Friswell (1995). In this situation the analytical model is characterized by a large number of degrees of freedom (and hence modes), ad hoc damping mechanisms and real eigenvectors (mode shapes). The FEM model produces a mass, damping and stiffness matrix which is numerically solved for modal data consisting of natural frequencies, mode shapes and damping ratios. Common practice is to compare this analytically generated modal data with natural frequencies, mode shapes and damping ratios obtained from EMA. The EMA data is characterized by a small number of modes, incomplete and complex mode shapes and non proportional damping. It is very common in practice for this experimentally obtained modal data to be in minor disagreement with the analytically derived modal data. The point of view taken is that the analytical model is in error and must be refined or corrected based on experimented data. The approach proposed here is to use the results of inverse eigenvalue problems to develop methods for model updating for damped systems. The inverse problem has been addressed by Lancaster and Maroulas (1987), Starek and Inman (1992,1993,1994,1997) and is summarized for undamped systems in the text by Gladwell (1986). There are many sophisticated model updating methods available. The purpose of this paper is to introduce using inverse eigenvalues calculated as a possible approach to solving the model updating problem. The approach is new and as such many of the practical and important issues of noise, incomplete data, etc. are not yet resolved. Hence, the method introduced here is only useful for low order lumped parameter models of the type used for machines rather than structures. In particular, it will be assumed that the entries and geometry of the lumped components is also known.

Free Vibration Analysis of PZT Glide Heads

1999 ◽  
Vol 121 (4) ◽  
pp. 984-988 ◽  
Author(s):  
Alex Y. Tsay ◽  
Jin-Hui Ouyang ◽  
C.-P. Roger Ku ◽  
I. Y. Shen ◽  
David Kuo
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Natural Frequencies ◽  
Laser Doppler Vibrometer ◽  
Free Vibration Analysis ◽  
Mode Shapes ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Bonding Length ◽  
Measured Displacement

This paper studies natural frequencies and mode shapes of a glide head with a piezoelectric transducer (PZT) through calibrated experiments and a finite element analysis. In the experiments, the PZT transducer served as an actuator exciting the glide head from 100 kHz to 1.3 MHz, and a laser Doppler vibrometer (LDV) measured displacement of the glide head at the inner or outer rail. The natural frequencies were measured through PZT impedance and frequency response functions from PZT to LDV. In the finite element analysis, the glide head was meshed by brick elements. The finite element results show that there are two types of vibration modes: slider modes and PZT modes. Only the slider modes are important to glide head applications. Moreover, natural frequencies predicted from the finite element analysis agree well with the experimental results within 5% of error. Finally, the finite element analysis identifies four critical slider dimensions whose tolerance will significantly vary the natural frequencies: PZT bonding length, wing thickness, slider thickness, and air bearing recess depth.

Vibration Characteristic Analysis of V-Shaped Electrothermal Microactuator

2012 ◽  
Vol 503 ◽  
pp. 118-121
Author(s):  
Zhen Lu Wang ◽  
Xue Jin Shen ◽  
Ling Zhou ◽  
Xiao Yang Chen
Keyword(s):  
Theoretical Calculation ◽  
Natural Frequency ◽  
Mechanical Model ◽  
Natural Frequencies ◽  
Maximum Error ◽  
Vibration Characteristic ◽  
Characteristic Analysis ◽  
Element Analysis ◽  
The Finite Element Analysis

This paper is focused on the finite element analysis (FEA) and theoretical calculation of vibration characterization of V-shaped electrothermal microactuator. A vibration mechanical model about V-shaped electrothermal microactuator is presented. By having a comparison between FEA and theoretical calculation about natural frequencies of V-shaped electrothermal microactuator, the maximum error is within 0.19 %. This paper also analyzes the influences of microactuator geometric parameters on natural frequency. The length and thickness have larger effect on the natural frequency of the actuator, while the angle and width have less effect on the natural frequency.

Effect of Osteoporosis on Natural Frequencies in Mouse Femur: Vibration Test and Micro-CT Based Finite Element Analysis

2006 ◽  
Vol 326-328 ◽  
pp. 851-854 ◽  
Author(s):  
Yoon Hyuk Kim ◽  
Chang Hwan Byun ◽  
Taek Yul Oh
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Mesh Generation ◽  
Natural Frequencies ◽  
Treated Group ◽  
Vibration Test ◽  
Micro Ct ◽  
Element Analysis ◽  
Generation Algorithm ◽  
The Finite Element Analysis

In this study, the change of the natural frequencies in mouse femurs with osteoporosis was investigated based on a vibration test and a finite element. Three groups of the femurs include the osteoporotic group, the treated group and the normal group. In the vibration test, the natural frequencies were measured by the mobility test. For the finite element analysis, the micro finite element model of the femur was reconstructed using the Micro-CT images and the Voxel mesh generation algorithm. From the results, the averaged natural frequencies in the osteoporotic group were the highest, followed by those in the treated group. The finite element models were validated within 15% errors by comparing the natural frequencies in the finite element analysis with those in the vibration test. The developed Micro-CT system, the Voxel mesh generation algorithm, the presented finite element analysis, and vibration test could be useful for the investigation of the structural change of the bone tissue, and the diagnosis and the treatment in the osteoporosis.

Mechanics of Regular-Shape Nanomeshes for Transparent and Stretchable Devices

2020 ◽  
Vol 87 (10) ◽  
Author(s):  
Sandra Vinnikova ◽  
Hui Fang ◽  
Shuodao Wang
Keyword(s):  
Mechanical Properties ◽  
Finite Element Analysis ◽  
Analytical Models ◽  
Regular Polygons ◽  
Element Analysis ◽  
Micro Scale ◽  
Regular Shape ◽  
The Finite Element Analysis ◽  
Mechanical Performances ◽  
Analytical Expressions

Abstract Open nanomesh structures with nano/micro-scale geometric dimensions are important candidates for transparent, soft, and stretchable microelectrodes. This study developed analytical and numerical mechanics models for three types of nanomeshes that consist of regular polygons and straight traces. The analytical models described the transparency, effective stiffness, and stretchability of the nanomeshes and agree with the finite element analysis. The mechanical performances of the nanomeshes are compared based on the same level of transparency. The validated analytical expressions provide convenient guidelines for designing the nanomeshes to have levels of transparency and mechanical properties suitable for bio-integrated applications.

scholarly journals Design and analysis of demolition robot arm based on finite element method

2019 ◽  
Vol 11 (6) ◽  
pp. 168781401985396 ◽  
Author(s):  
Jiong Li ◽  
Yu Wang ◽  
Kai Zhang ◽  
Zhiqiao Wang ◽  
Jiaxing Lu
Keyword(s):  
Finite Element ◽  
Natural Frequencies ◽  
Impact Force ◽  
Second Order ◽  
Robot Arm ◽  
Element Analysis ◽  
Front End ◽  
The Finite Element Analysis ◽  
The Impact ◽  
Ansys Workbench

As a novel robot which mainly engages in the demolition and transformation of various concrete buildings, the demolition robot has developed rapidly in recent years. The impact force is mainly produced by the breaking hammer installed in the front end of the arm. As the most important part of a demolition robot, the boom arm is mainly composed of four parts including a supporting arm, a main arm, a fore arm, and a breaking hammer system. In this article, a mechanical model of the boom arm is established, and the finite element analysis obtaining the first four-order natural frequencies and modes is carried out in ANSYS Workbench. The results reveal that the resonation can be easily stimulated when a hydraulic breaking hammer is at the second-order frequency. The mounting block of the hydraulic breaking hammer, the hinge parts of the supporting arm, and the main arm are easily deformed or damaged in the Y direction by analyzing the deformation in three directions of the second-order mode. After the structure optimization, the vibration characteristics of the two parts are significantly enhanced, which provides a theoretical basis for optimizing the prototype and gives a reference in the experimental modes.

Analysis on Dynamic Characteristics of HTC100 NC Lathe Bed

2011 ◽  
Vol 328-330 ◽  
pp. 700-703
Author(s):  
Mo Wu Lu ◽  
Guo Ming Zhang ◽  
Wei Qiang Zhao
Keyword(s):  
Modal Analysis ◽  
Performance Indicators ◽  
Natural Frequencies ◽  
Dynamic Performance ◽  
Analysis Method ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
3D Solid ◽  
Modal Vibration ◽  
Ansys Workbench

The processing performance is closely related with dynamic performance and the dynamic performance is one of the most important performance indicators which is affecting the performance and product quality. The machine is affected most by the dynamic performance of machine bed. The modal analysis method is used to analyze the dynamic performance of the machine. In this paper, the modal analysis of lathe bed is conducted. A 3D solid model of HTC100 NC lathe bed is built with SolidWorks. In order to facilitate the finite element analysis, the model of lathe bed is simplified. The modal analysis of lathe bed is calculated with ANSYS Workbench 12. The first six natural frequencies and corresponding modes are obtained through modal analysis of the lathe bed. According to the low-order natural frequency and modal vibration shapes, the rigidity vulnerable area of lathe bed is realized, which provides the reliable theory to improve lathe bed structure.

Design of a New Compliant Mechanical Amplifier

2005 ◽  
Author(s):  
P. R. Ouyang ◽  
W. J. Zhang ◽  
M. M. Gupta
Keyword(s):  
Natural Frequencies ◽  
Lateral Displacement ◽  
Critical Parameters ◽  
Element Analysis ◽  
Amplification Ratio ◽  
Flexure Hinges ◽  
Compact Size ◽  
Double Beam ◽  
The Finite Element Analysis ◽  
Better Than

In this paper, a new topology that is a symmetric five bar profile for displacement amplification is proposed, and a compliant mechanical amplifier (CMA) based on the new topology is designed to amplify the stroke of a piezoelectric actuator. The new CMA can convert the motion generated by a PZT actuator with a large amplification ratio (24.4) in a very compact size, and it has a high natural frequency (573 Hz) and no lateral displacement. First, three existing topologies of CMA are analyzed and evaluated, which results in the new topology of CMA. After that, the new CMA is designed with different flexure hinges. The finite element analysis for the CMA shows that the double-beam symmetric five bar structure using the corner-filleted hinges can provide the best performance in terms of the displacement amplification and natural frequencies. The designed CMA is clearly better than the CMA based on the topology of a double symmetric four bar profile. Finally, the design is fine-tuned by examining critical parameters for the proposed CMA in light of a large displacement amplification ratio.

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