Natural Frequency Region – Fluid-Structural-Interaction approach for dynamic impact predictions and experimental verification of rubber–metal bonded systems with fluid

2018 ◽  
Vol 233 (2) ◽  
pp. 211-219 ◽  
Author(s):  
Robert K Luo ◽  
Ping Lou ◽  
Weidong Wang ◽  
Naizheng Guo
Keyword(s):  
Natural Frequency ◽  
Experimental Verification ◽  
Time Frame ◽  
Frequency Region ◽  
Design Stage ◽  
Dynamic Impact ◽  
Structural Interaction ◽  
Central Processing ◽  
Interaction Approach ◽  
Impact Predictions

This paper presents an integrated procedure for dynamic impact predictions and an experimental verification of rubber–metal bonded components with fluid to be used as a potential application in rail vehicle suspensions. There are three steps involved in the procedure. First, a quasi-static analysis was performed to verify the elastic properties of the rubber material using hyperelastic models. Second, a dynamic impact evaluation on selected hydro-mounts without fluid was conducted using the Natural Frequency Region (NFR) approach. Finally, a coupled NFR (with Fluid-Structural-Interaction) approach, different from the usual viscoelastic methods, was initiated to predict the dynamic impact responses of these components with the fluid in time domain. All the analyses have been validated with experimental data. The first two stages have been briefly described and the third stage is detailed in this paper. It should be noted that a powerful computer with multi-central processing units is essential to obtain a reasonable result within an acceptable time frame. It took approximately 40 h wall-clock time to complete the analysis using a workstation with 10 central processing units. It has been suggested that the natural frequency region–fluid–structure interaction methodology is reliable and could be used at the design stage and for engineering applications.

Springing Responses Analysis and Segmented Model Testing on a 550,000 DWT Ore Carrier

2016 ◽  
Author(s):  
Hui Li ◽  
Di Wang ◽  
Cheng Ming Zhou ◽  
Kaihong Zhang ◽  
Huilong Ren
Keyword(s):  
Natural Frequency ◽  
Design Stage ◽  
Resonant Vibration ◽  
Bending Moments ◽  
Wave Loads ◽  
Regular Waves ◽  
Segmented Model ◽  
Ship Model ◽  
Hull Structure ◽  
Stiffness Distribution

For ultra large ore carriers, springing response should be analyzed in the design stage since springing is the steady-state resonant vibration and has an important effect on the fatigue strength of hull structure. The springing response of a 550,000 DWT ultra large ore carrier has been studied by using experimental and numerical methods. A flexible ship model composed of nine segments was used in the experiment. The model segments were connected by a backbone with varying section, which can satisfy the request of natural frequency and stiffness distribution. The experiments in regular waves were performed and the motions and wave loads of the ship were measured. The experimental results showed that springing could be excited when the wave encounter frequency coincides with half or one-third the flexural natural frequency of the ship. In this paper, the analysis of the hydroelastic responses of the ultra large ore carrier was also carried out using a 3-D hydroelastic method. Comparisons between experimental and numerical results showed that the 3-D hydroelastic method could predict the motions and the vertical bending moments quite well. Based on this numerical method, the fatigue damage was estimated and the contribution of springing was analyzed.

scholarly journals Study of Vibration Behaviour of Stiffened Polymer Composite Shells for Underwater Structural Applications

2020 ◽  
Vol 70 (3) ◽  
pp. 342-350 ◽  
Author(s):  
Subhash R. Patil ◽  
H. N. Narasimha Murthy ◽  
G.S. Srivatsa ◽  
Viketh S. Yandigeri ◽  
Ramanraj K. ◽  
...  
Keyword(s):  
Natural Frequency ◽  
Polymer Composite ◽  
Modal Testing ◽  
Mode Shapes ◽  
Vibration Behavior ◽  
Filament Wound ◽  
Structural Applications ◽  
Response Method ◽  
Interaction Approach ◽  
Thick Shells

This paper presents vibration behavior of ring stiffened polymer composite thick shells used for underwater structures. Filament wound shells stiffened with internal and external rings and with hemispherical ends were tested for vibration in air and water in free-free boundary condition using roving hammer and fixed response method. Modal testing of the shells was performed under hydrostatic loading in a custom designed buckling tester for determining natural frequency at higher sea depths. Accelerometer was mounted on the inner surface of the shell. It was excited using a plumbob, rope and pulley arrangement. Experimental results were validated by modal analysis using Hyperworks and ANSYS. Vibration behavior in water was simulated by Fluid structure interaction approach. Experimental first natural frequency in water was lesser than that in air. With increase in hydrostatic pressure, the shell showed moderate variation in natural frequency. The experimental and numerical results of natural frequency and mode shapes were in good agreement with each other. Natural frequencies were lower in long and thick shells.

Influence of equipment rigidity on the natural bending frequency of the EMU train car body

2018 ◽  
Vol 77 (4) ◽  
pp. 251-255
Author(s):  
R. V. Guchinsky
Keyword(s):  
Natural Frequency ◽  
Specific Weight ◽  
The Body ◽  
Design Stage ◽  
Static Characteristics ◽  
Bending Vibrations ◽  
Car Body ◽  
Design Documentation ◽  
Normalized Parameters ◽  
Concentrated Masses

The first frequency of the own bending vibrations of the car body of the EMU train is one of the main normalized parameters associated with smooth running. Estimation of this parameter at the design stage allows to accelerate the process of development of design documentation and to reduce further number of tests. Rigidity of the undercarriage and roof equipment of the EMU train cars contributes to the overall rigidity of the body. When simulating the equipment with concentrated masses at the attachment points, underestimating the rigidity of the body results in underestimated values of the first natural frequency of bending vibrations of the body. It is shown that modeling the equipment with a rigid area with subordinate nodes at the attachment points makes it possible to simplify the process of constructing the model and adequately take into account the rigidity of the equipment not only in determining the static characteristics of body deflections, but also in calculating the dynamic characteristic and the first natural frequency. Using subordinate nodes of a rigid area on the surfaces of the fixing holes leads to a reassessment of the natural frequency. Value of the first natural frequency of the body oscillations is linearly dependent on the specific weight of the undercarriage equipment. When designing the bodies of EMU train cars (especially motor cars), in order to increase the frequency value, the equipment boxes should be located, taking into account the compatibility of the deformations of the box frames and the loadbearing structure of the body. Massive boxes for small equipment should be placed as close to the bolster beams as possible. If it is necessary to place largesize boxes under the car equipment, one should consider variants of its location in the central part of the body to include the box frames in the bend of the transverse beams of the frame.

Frequency Domain Structural Optimization of a Flexible Manipulator Incorporating a PD Controller in the Design Stage

1999 ◽  
Author(s):  
Yong Hoon Chang ◽  
Ali Seireg
Keyword(s):  
Structural Optimization ◽  
Natural Frequency ◽  
Dynamic Performance ◽  
Integrated Design ◽  
Flexible Manipulator ◽  
Design Stage ◽  
Pd Controller ◽  
Design Strategies ◽  
Flexible Mode ◽  
Modal Mass

Abstract This study investigates the potential advantages of integrated design strategies for flexible manipulators that utilize a controller in the process of optimizing the structural design. Clamped free and clamped mass beam models are considered in the investigation for the structural optimization with respect to natural frequencies and mass. A PD controller is utilized in the design process with several objective functions that incorporate weighted combinations of the mass of the structure, modal mass, modal stiffness, and the natural frequency of the rigid mode and the dominant natural frequency of the flexible mode. The results show that the objective function, which minimizes the mass and the product of the modal mass and modal stiffness of the rigid mode and maximize the natural frequency of the flexible mode with appropriate weighting factors, gave the best dynamic performance. Although a two link tubular planar manipulator with a PD controller and assumed beam models for the links is considered in the optimization based on modal parameters, the reported approach can be extended to time domain optimization of multi-link spacial robots with complex structures designed to perform particular tasks.

Analytical and Experimental Modal Characteristics of Cylindrical Shells

2005 ◽  
Author(s):  
Basem Alzahabi
Keyword(s):  
Natural Frequency ◽  
Natural Frequencies ◽  
Cylindrical Shells ◽  
Offshore Structures ◽  
Operating Conditions ◽  
Mode Shapes ◽  
Design Stage ◽  
Scaled Model ◽  
Modal Characteristics ◽  
Acoustic Signature

Cylindrical Shells are widely used in many structural designs, such as offshore structures, liquid storage tanks, submarine hulls, and airplane hulls. Most of these structures are required to operate in a dynamic environment. The acoustic signature of submarines is very critical in such high performance structure. Submarines are not only required to sustain very high dynamic loadings at all time, but also being able maneuver and perform their functions under sea without being detected by sonar systems. Reduction of sound radiation is most efficiently achieved at the design stage, and the acoustic signatures may be determined by considering operational scenarios, and modal characteristics. The acoustic signature of submarines is generally of two categories; broadband which has a continuous spectrum; and a tonal noise which has discrete frequencies. Therefore, investigating the dynamic characteristics of cylindrical shells is very critical first step in developing a strategy for modal vibration control for specific operating conditions. Unlike those of beam structure, the lowest natural frequency does not necessarily correspond to the lowest wave index. In fact, the natural frequencies do not fall in ascending order of the wave index in cylindrical shells. Mode shapes associated with each natural frequency are combination of Radial, Longitudinal, and Circumferential modes. In this paper, a scaled model of submarine hull segment under shear diaphragm boundary conditions is analyzed analytically and numerically. Then experimental modal analysis of the scaled model utilizing a fixed response approach was performed to obtain the modal characteristics of the cylindrical shell between 0 and 800 Hz. The cylinder was excited at predetermined points with an impact hammer, while the response was measured using an accelerometer at specified fixed point. Designing a boundary condition that simulate a shear diaphragm is very challenging task by itself. A total of ten natural frequencies were found within that range with their corresponding mode shapes. The experimental data were correlated with those results obtained analytically and numerically using the finite element methods using MSC.NASTRAN software. The results were found to be in excellent agreement.

Membrane and Bending Strain in Cylindrical Shell Vibrations

2009 ◽  
Author(s):  
Basem Alzahabi ◽  
Henry Kowalski
Keyword(s):  
Natural Frequency ◽  
Strain Energy ◽  
Natural Frequencies ◽  
Cylindrical Shells ◽  
Operating Conditions ◽  
Total Strain ◽  
Design Stage ◽  
Total Strain Energy ◽  
Scaled Model ◽  
Membrane Strain

Cylindrical Shells are widely used in many structural designs, such as offshore structures, liquid storage tanks, submarine hulls, and airplane hulls. Most of these structures are required to operate in a dynamic environment. Therefore, investigating the dynamic characteristics of cylindrical shells is very critical in developing a strategy for modal vibration control for specific operating conditions. Reduction of vibration amplitudes and in sound radiation is most efficiently achieved at the design stage, and the acoustic signatures may be determined by considering operational scenarios, and modal characteristics. In cylindrical shells, mode shapes associated with each natural frequency are combination of Radial, Longitudinal, and Circumferential modes, and unlike those of beam structure, the lowest natural frequency does not necessarily correspond to the lowest wave index. In fact, the natural frequencies do not fall in ascending order of the wave index in cylindrical shells. The ratio of membrane strain energy to total strain energy is high for modes with simple modal patterns and decrease toward zero as the number of nodal (n) lines increase, while the ratio of bending energy to total strain energy is small for simple nodal patterns and increase with increase in complexity of it. Modes associated with membrane deformation require a lot of strain energy while modes associated with bending deformation require less strain energy. The lowest natural frequency occurs where the sum of the two energies are at minimum. Moreover, the natural frequencies that are controlled by membrane strain energy are approximately independent of the shell thickness change. In this paper, a scaled model of submarine hull segment under shear diaphragm boundary conditions is analyzed analytically and numerically. Then the experimental modal analysis of the scaled model utilizing strain gauges was performed to decouple the strain components. Designing a boundary condition that simulate a shear diaphragm is very challenging task by itself. The experimental data were correlated with those results obtained analytically and numerically using the finite element methods using MSC.NASTRAN software. The results were found to be in excellent agreement.

scholarly journals Prediction of Room Noise Caused by Vibration of High Power Elevator Traction Machine

2021 ◽  
Vol 8 ◽  
pp. 16-20
Author(s):  
Shinichi Noda ◽  
Yoshitake Kamijo ◽  
Sueyoshi Mizuno ◽  
Makoto Matsushita
Keyword(s):  
Natural Frequency ◽  
High Power ◽  
Wave Motion ◽  
Acoustic Noise ◽  
Frequency Mode ◽  
Design Stage ◽  
Wave Phase ◽  
Phase Interference

Total simulation from vibration of elevator motor to noise at sitting room with anti-vibration measures is confirmed in design stage. This procedure also presents decrease of acoustic noise in sitting room. In this simulation, FEM calculates wave motion, such as wave phase, interference, diffraction and natural frequency mode of sitting room wall. These procedures yield the ration between vibration of elevator motor and acoustic noise in sitting-room.

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