scholarly journals Structural Modifications for Torsional Vibration Control of Shafting Systems Based on Torsional Receptances

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Zihao Liu ◽  
Wanyou Li ◽  
Huajiang Ouyang
Keyword(s):  
Vibration Control ◽  
Torsional Vibration ◽  
Structural Data ◽  
Element Model ◽  
Mode Shapes ◽  
Structural Modifications ◽  
Shaft System ◽  
Vibration Problems ◽  
Set Up ◽  
Levels Of Integration

Torsional vibration of shafts is a very important problem in engineering, in particular in ship engines and aeroengines. Due to their high levels of integration and complexity, it is hard to get their accurate structural data or accurate modal data. This lack of data is unhelpful to vibration control in the form of structural modifications. Besides, many parts in shaft systems are not allowed to be modified such as rotary inertia of a pump or an engine, which is designed for achieving certain functions. This paper presents a strategy for torsional vibration control of shaft systems in the form of structural modifications based on receptances, which does not need analytical or modal models of the systems under investigation. It only needs the torsional receptances of the system, which can be obtained by testing simple auxiliary structure attached to relevant locations of the shaft system and using the finite element model (FEM) of the simple structure. An optimization problem is constructed to determine the required structural modifications, based on the actual requirements of modal frequencies and mode shapes. A numerical experiment is set up and the influence of several system parameters is analysed. Several scenarios of constraints in practice are considered. The numerical simulation results demonstrate the effectiveness of this method and its feasibility in solving torsional vibration problems in practice.

Modal Analysis of a Simple Supported Beam Steel Bridge Based on ANSYS

2012 ◽  
Vol 594-597 ◽  
pp. 2867-2870
Author(s):  
Dong Li Wang ◽  
Tong Li ◽  
Chun Yu Wang
Keyword(s):  
Modal Analysis ◽  
Health Monitoring ◽  
Element Model ◽  
Rate Of Change ◽  
Mode Shapes ◽  
Steel Bridge ◽  
Bridge Health Monitoring ◽  
Bridge Model ◽  
Set Up ◽  
Index Value

The purpose and significance of bridge health monitoring is described in this paper. In order to study bridge health monitoring, Firstly, a finite element model for simply supported steel beam is set up on the basis of the Infinite Element Theory and the software ANSYS in response to laboratory experient. Through adding instantaneous excitation to the mid-span, do modal analysis for different injury of steel bridge model to reveal the natural frequency and mode shapes of the different injury of steel bridges, identify the different injury by comparing the index value and the rate of change.

Solution for the torsional vibration of the compressor shaft system with flexible coupling based on a sensitivity study

2018 ◽  
Vol 233 (4) ◽  
pp. 803-812
Author(s):  
Jianmei Feng ◽  
Ying Zhao ◽  
Xiaohan Jia ◽  
Xueyuan Peng
Keyword(s):  
Torsional Vibration ◽  
Sensitivity Study ◽  
Calculation Model ◽  
Mode Shapes ◽  
Primary Data ◽  
Elastic Model ◽  
Lumped Mass ◽  
Shaft System ◽  
Speed Fluctuation ◽  
One Year

This paper presents the root cause analysis and solving process of the torsional vibration problem in a reciprocating compressor shaft system. The field measured data showed that the fifth-order torsional resonance occurred in the shaft system. The lumped-mass method was adopted to calculate the torsional natural frequencies (TNFs) and mode shapes of the shaft system. A sensitivity study was conducted to investigate the effect of each inertia and stiffness in the calculation model on the first TNF of the shaft system. The uncertainties of the primary data of the calculation model were discussed, and the mass-elastic model was modified by adjusting the stiffness of the flexible disc coupling. After adding an inertia of 4.68 kg·m2, torsional resonance was avoided, and the speed fluctuation of the shaft system was significantly reduced. The compressor package has been operating normally for nearly one year after modification. The analysis methods and conclusions given here can provide guidance for trouble-shooting torsional vibration problems.

Analysis of Unimorph Piezoceramic Patches on Damped Square Shaped Plate

2013 ◽  
Vol 315 ◽  
pp. 965-971 ◽  
Author(s):  
A.M. Najib ◽  
A.J. Fairul ◽  
Ahmad Yusairi Bani Hashim ◽  
Hazman Hasib ◽  
M.N. Muhammad
Keyword(s):  
Low Frequency ◽  
Piezoelectric Element ◽  
Element Model ◽  
Mode Shapes ◽  
Vibration Displacement ◽  
Electric Excitation ◽  
Damping Control ◽  
Linear Behavior ◽  
Vibration Problems ◽  
Force Excitation

Active damping using piezoelectric element is one of the effective techniques to counter vibration problems. A 3D finite-element model is developed as part of investigation for damping control. The piezoelectric patches are surface bonded on quadrilateral thin plate and supported with spring damper elements. The main goal of this paper is to investigate mechanical characteristics of piezoceramic array on membrane and the effect of force excitation using small motor and electric excitation on the system. The system setup produced small vibration displacement and does not displace the plate beyond elastic strain region. The results show the linear behavior of piezoceramic and the correlation between electric excitation, motor vibration and displacement at the centre of the plate at different frequency range. The mode shapes and natural frequencies at low frequency spectrum are also presented. Therefore, the results can be used as reference to develop damping system with aid of piezoelectric patches.

Prediction Capabilities of Damped Updated Finite Element Models

2011 ◽  
Author(s):  
Vikas Arora
Keyword(s):  
Finite Element ◽  
Model Updating ◽  
Dynamic Properties ◽  
Detailed Comparison ◽  
Element Model ◽  
Mode Shapes ◽  
Finite Element Models ◽  
Complex Frequency ◽  
Structural Modifications ◽  
The Finite Element Model

Model updating techniques are used to correct the finite element model of a structure using experimental data such that the updated model more correctly describes the dynamic properties of the structure. One of the applications of such an updated model is to predict the effects of making modifications to the structure. These modifications may be imposed by design alterations for operating reasons. Most of the model updating techniques neglect damping and so these updated models can’t be used for accurate prediction of complex frequency response functions (FRFs) and complex mode shapes. In this paper, a detailed comparison of prediction capabilities of parameter-based and non parameter-based damped updated methods for structural modifications is done. The suitability of paramter-based and non parameter-based damped updated models for predicting the effects of structural modifications is evaluated by laboratory experiment for the case of an F-shape test structure. It is concluded that parameter-based damped updated models are likely to perform better in predicting the effects of structural modifications.

scholarly journals Partial Frequency Assignment for Torsional Vibration Control of Complex Marine Propulsion Shafting Systems

2019 ◽  
Vol 10 (1) ◽  
pp. 147
Author(s):  
Meilong Chen ◽  
Huajiang Ouyang ◽  
Wanyou Li ◽  
Donghua Wang ◽  
Siyuan Liu
Keyword(s):  
Vibration Control ◽  
Natural Frequency ◽  
Torsional Vibration ◽  
Control Method ◽  
Excitation Frequency ◽  
Frequency Assignment ◽  
Effective Control ◽  
Partial Frequency ◽  
Structural Modifications ◽  
Ship Propulsion

With the large-scale and complexity of ship propulsion shafting, it is more difficult to analyze and control the torsional vibration of shafting. Therefore, an effective control method for the torsional vibration of shafting is of great significance in the field of ship engineering. The main strategy of torsional vibration control adopted in this paper is to keep the natural frequency of a shaft system away from the excitation frequency through structural modifications. In addition, because the basic parameters of much of the equipment in engineering applications cannot be changed, this restriction cannot be ignored when seeking solutions related to structural modifications. This paper studies the partial eigenvalue assignment for the torsional vibration control of complex ship propulsion shafting using the gradient flow method, which can shift a “dangerous” natural frequency to a safe value, while satisfying complex physical constraints. The models of a ship propulsion system and a diesel generator set are established to demonstrate several different desired modification schemes and constraint conditions in practice. In particular, close frequencies are shifted. The numerical simulation results demonstrate that it is effective and feasible to make a partial frequency assignment of torsional vibration, which provides a reliable approach for the control of torsional vibration for complex shaft systems in practical engineering.

TIME-AVERAGE HOLOGRAPHY TO ANALYZE DYNAMIC BEHAVIOR OF SKIN TISSUES UNDER DIFFERENT CONDITIONS

2017 ◽  
Vol 17 (01) ◽  
pp. 1750020
Author(s):  
ANTONIO BOCCACCIO ◽  
GAETANO GENCHI ◽  
LUCIANO LAMBERTI ◽  
CARMINE PAPPALETTERE
Keyword(s):  
Dynamic Behavior ◽  
Mechanical Response ◽  
Element Model ◽  
Mode Shapes ◽  
Tissue Samples ◽  
Use Of Time ◽  
Time Average ◽  
Set Up ◽  
Reliability And Robustness ◽  
Skin Samples

This study aims to investigate the feasibility of using time-average holography to verify the integrity of skin tissue samples and detect changes in their mechanical response caused by exposure to thermal perturbations, radiations and mechanical loading. For that purpose, chicken skin samples are put into vibration and the corresponding modes are monitored by means of an optical set up based on time average holographic interferometry. Mode shapes of base samples computed by a parametric finite element model are consistent with experimental data. The holographic set up correctly detects the presence of defects previously included in the sample. Dynamic behavior of skin samples under various conditions of low/high temperature and load or exposed, for different periods of time, to UV radiation and microwaves also is successfully monitored. The reliability and robustness of the proposed approach is tested by performing the holographic observations on a large number of samples under different conditions. Potential benefits that may derive from the use of time-average holography in dermatology and plastic surgery (for example, in the quality control of artificial skin tissues to be implanted) are finally discussed.

Torsional Vibration Control of a Rotating Chamber Shaft System Using Electrorheological Fluid

2011 ◽  
Vol 35 (1) ◽  
pp. 17-24 ◽  
Author(s):  
Seung-Chul Lim ◽  
Ki-Kap Kim ◽  
Seong-Jin Kil ◽  
Jeong-Soo Shim ◽  
Ki-Up Cha
Keyword(s):  
Vibration Control ◽  
Torsional Vibration ◽  
Electrorheological Fluid ◽  
Shaft System

scholarly journals Vibration characteristics of triple-gear-rotor system in compressed air energy storage under variable torque load

2021 ◽  
Vol 104 (1) ◽  
pp. 003685042098705
Author(s):  
Xinran Wang ◽  
Yangli Zhu ◽  
Wen Li ◽  
Dongxu Hu ◽  
Xuehui Zhang ◽  
...  
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Element Model ◽  
Rotor System ◽  
Dynamic Responses ◽  
System Response ◽  
Rotating Speed ◽  
Torque Load ◽  
Set Up ◽  
Two Stages

This paper focuses on the effects of the off-design operation of CAES on the dynamic characteristics of the triple-gear-rotor system. A finite element model of the system is set up with unbalanced excitations, torque load excitations, and backlash which lead to variations of tooth contact status. An experiment is carried out to verify the accuracy of the mathematical model. The results show that when the system is subjected to large-scale torque load lifting at a high rotating speed, it has two stages of relatively strong periodicity when the torque load is light, and of chaotic when the torque load is heavy, with the transition between the two states being relatively quick and violent. The analysis of the three-dimensional acceleration spectrum and the meshing force shows that the variation in the meshing state and the fluctuation of the meshing force is the basic reasons for the variation in the system response with the torque load. In addition, the three rotors in the triple-gear-rotor system studied show a strong similarity in the meshing states and meshing force fluctuations, which result in the similarity in the dynamic responses of the three rotors.

scholarly journals Corrosion of Steel Rebars in Anoxic Environments. Part II: Pit Growth Rate and Mechanical Strength

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2547
Author(s):  
Elena Garcia ◽  
Julio Torres ◽  
Nuria Rebolledo ◽  
Raul Arrabal ◽  
Javier Sanchez
Keyword(s):  
Mechanical Strength ◽  
Chloride Content ◽  
Element Model ◽  
Offshore Structures ◽  
Anoxic Environments ◽  
Electrochemical Parameters ◽  
Cathode Area ◽  
Optical Profilometer ◽  
Set Up ◽  
Corrosion Of Steel

Reinforced concrete may corrode in anoxic environments such as offshore structures. Under such conditions the reinforcement fails to passivate completely, irrespective of chloride content, and the corrosion taking place locally induces the growth of discrete pits. This study characterised such pits and simulated their growth from experimentally determined electrochemical parameters. Pit morphology was assessed with an optical profilometer. A finite element model was developed to simulate pit growth based on electrochemical parameters for different cathode areas. The model was able to predict long-term pit growth by deformed geometry set up. Simulations showed that pit growth-related corrosion tends to maximise as cathode area declines, which lower the pitting factor. The mechanical strength developed by the passive and prestressed rebar throughout its service life was also estimated. Passive rebar strength may drop by nearly 20% over 100 years, whilst in the presence of cracking from the base of the pit steel strength may decline by over 40%.

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