Research on Free Damping Treatment for a Marine Life Hoist of the Helicopter

2012 ◽  
Vol 518-523 ◽  
pp. 3859-3864
Author(s):  
Jia Rui Qi ◽  
Jing Tao Dai ◽  
Yan Li Li ◽  
Dan Feng Zhang
Keyword(s):  
Loss Factor ◽  
Damping Ratio ◽  
Structural Vibration ◽  
Marine Life ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Damping Material ◽  
Damping Loss Factor ◽  
Actual Life

Free damping treatment for a marine life hoist of the helicopter is analyzed in this paper. Based on the pipe structure used in actual life hoist bracket, the complex rigidity method is used to analyze the damping loss factor of the pipe structure. When the temperature is 30°C and the thickness of the damping material is 2.5mm, the damping loss factor of the structure increases by 9.83 times. The damping ratio of the first mode reaches 11.61%. The results indicate that the free damping treatment can obviously increase the damping loss factor and the modal damping ratio of the structure, which can mitigate structural vibration and reduce noise induced by the vibration.

scholarly journals Identification of Loss Factor of Fiber-Reinforced Composite Based on Complex Modulus Method

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Hui Li ◽  
Yi Niu ◽  
Chao Mu ◽  
Bangchun Wen
Keyword(s):  
Loss Factor ◽  
Complex Modulus ◽  
Damping Ratio ◽  
Fiber Reinforced ◽  
Identification Procedure ◽  
Fiber Reinforced Composite ◽  
Modal Damping Ratio ◽  
Reinforced Composite ◽  
Modal Damping ◽  
Modulus Method

The identification of the loss factor of fiber-reinforced composite based on complex modulus method is presented. Firstly, the damping model of fiber-reinforced composite plate is established, and the relation between each loss factor and modal damping ratio is deduced based on the complex modulus method. Then, the least square relative error function is formed by using the modal damping ratio obtained in the experimental test, and the appropriate step-size is selected in the range of 0~10% to calculate the loss factor. Next, the identification procedure of loss factor of such composite material is summarized, and the corresponding identification procedure is realized based on self-designed MATLAB program. Finally, TC300 carbon/epoxy composite plate is taken as an example to carry out a case study, and its loss factors along the longitudinal, transverse, and shear direction are identified by the complex modulus method. By comparing the measured damping results obtained in this paper and the calculated damping results based on the Adams-Bacon model with the same loss factor, it is found that the corresponding maximum deviation between them is less than 15%, so the correctness of such identification method has been verified indirectly, which can be used to identify loss factor of fiber-reinforced composite with high precision and efficiency.

Experimental Study the Vibro-Acoustic Performance of a Double Glazed Window

2012 ◽  
Vol 503-504 ◽  
pp. 1129-1132
Author(s):  
Qi Bo Mao
Keyword(s):  
Damping Ratio ◽  
Normal Wave ◽  
Sound Transmission ◽  
Least Square ◽  
Structural Vibration ◽  
Mode Shapes ◽  
Reverberation Chamber ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Complex Exponential

This paper presents an experimental investigation of the sound transmission and structural vibration characteristics of the double glazed window. The laboratory experiments were performed placing the window between reverberation chamber and anechoic chamber. The window was subject to diffuse field, approximate normal wave and oblique wave acoustic excitations. The sound transmission performances at far-field were measured. Furthermore, experimental modal analysis has been performed. The Least square complex exponential algorithm is used to extract the modal parameters, i.e. mode shapes, natural frequencies and modal damping ratio of the structure. The results also show that the highest sound transmission of this experimental double glazed window appears around the mass-air-mass resonance frequency.

Modal damping ratio analysis of dynamical system with non-stationary responses

2016 ◽  
Vol 59 ◽  
pp. 138-146 ◽  
Author(s):  
Da Tang ◽  
Ran Ju ◽  
Qianjin Yue ◽  
Shisheng Wang
Keyword(s):  
Dynamical System ◽  
Damping Ratio ◽  
Ratio Analysis ◽  
Modal Damping Ratio ◽  
Modal Damping

scholarly journals Coupling of Flexural and Longitudinal Damped Vibration in a Two-Layered Beam

1998 ◽  
Vol 5 (5-6) ◽  
pp. 337-341
Author(s):  
F. Pourroy ◽  
S. Shakhesi ◽  
P. Trompette
Keyword(s):  
Damping Ratio ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Resonance Frequencies ◽  
Layered Beam ◽  
Flexural Vibrations

In dynamics, the effect of varying the constitutive materials’ thickness of a two-layered beam is investigated. Resonance frequencies and damping variations are determined. It is shown that for specific thicknesses the coupling of longitudinal and flexural vibrations influences the global modal damping ratio significantly.

Optimization Design on Vibration and Noise Reduction of Damping Sandwich Circular Saw

2012 ◽  
Vol 215-216 ◽  
pp. 433-437
Author(s):  
Ting Wang ◽  
Tao Yao ◽  
Guo Lin Duan
Keyword(s):  
Noise Reduction ◽  
Loss Factor ◽  
Optimization Design ◽  
Design Method ◽  
Optimal Thickness ◽  
Damping Effect ◽  
Circular Saw ◽  
Damping Material ◽  
Material Element ◽  
Damping Loss Factor

In view of the study of topology optimization design method on vibration and noise reduction of damping sandwich circular saw, the optimal thickness and layout of damping material were obtained. The optimization model of circular saw was established by using the coupling method, the optimum thickness of damping layer was found. By using ESO method, deleting elements method and modal loss factor sensitivity calculation method were obtained. Making use of modal loss factor sensitivity, ineffective elements were deleted by judging the whole structure damping effect on each damping material element, optimal configuration of damping sandwich circular saw structure under the stiffness condition was obtained, which reduced the vibration and noise and reached a certain stiffness requirements. By contrasting the damping loss factor of three different circular saw models, the results show that optimized circular saw structure has the best damping effect.

ODS Analysis on the Rack of Batching System Mixer

2013 ◽  
Vol 437 ◽  
pp. 257-260
Author(s):  
Li Zhang ◽  
Guang Yuan Nie
Keyword(s):  
Working Condition ◽  
Damping Ratio ◽  
Side Surface ◽  
Modal Parameters ◽  
Modal Shape ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Before And After ◽  
Structure Vibration ◽  
Batching Machine

By using ODS (Operating Deflection Shapes) technology, the modal parameters of the rack of a batching system mixer under operating condition are identified and the modal shape and modal damping ratio of the rack in a few working frequencies are obtained. The results show that, the batching machine rack on working condition has a significant effect on some frequency and the work principal modes that appear as before and after exercise of two beams above the rack and swaying motion of the brackets of the two side surface. This paper provides a valuable reference for the structure vibration optimization of batching system mixer.

Free Vibration Analysis of Frame-Core Tube Structures Attached with Damped Outriggers

2012 ◽  
Vol 238 ◽  
pp. 648-651
Author(s):  
Zhi Hao Wang
Keyword(s):  
Damping Ratio ◽  
Free Vibration Analysis ◽  
Structural System ◽  
Viscous Dampers ◽  
Core Tube ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
New Energy ◽  
Energy Dissipation System ◽  
Simplified Calculation

The classical outrigger in frame-core tube structure cantilevering from the core tube or shear wall connected to the perimeter columns directly, which can effectively improve the lateral stiffness of the structure. A new energy-dissipation system for such structural system is studied, where the outrigger and perimeter columns are separate and vertical viscous dampers are equipped between the outrigger and perimeter columns to make full use of the relative big displacement of two components. The effectiveness of proposed system is evaluated by means of the modal damping ratio based on the proposed simplified model. The mathematic models of the structural system are obtained with both the assumed mode shape method and finite element method according to the simplified calculation diagram. Based on the modal damping ratio, the optimal damping coefficients of linear viscous dampers are determined, and effectiveness of proposed system is confirmed.

scholarly journals Topology Optimization of Constrained Layer Damping on Plates Using Method of Moving Asymptote (MMA) Approach

2011 ◽  
Vol 18 (1-2) ◽  
pp. 221-244 ◽  
Author(s):  
Zheng Ling ◽  
Xie Ronglu ◽  
Wang Yi ◽  
Adel El-Sabbagh
Keyword(s):  
Topology Optimization ◽  
Energy Dissipation ◽  
Design Variable ◽  
Optimization Design ◽  
Damping Ratio ◽  
Design Tool ◽  
Optimization Approach ◽  
Constrained Layer Damping ◽  
Modal Damping Ratio ◽  
Modal Damping

Damping treatments have been extensively used as a powerful means to damp out structural resonant vibrations. Usually, damping materials are fully covered on the surface of plates. The drawbacks of this conventional treatment are also obvious due to an added mass and excess material consumption. Therefore, it is not always economical and effective from an optimization design view. In this paper, a topology optimization approach is presented to maximize the modal damping ratio of the plate with constrained layer damping treatment. The governing equation of motion of the plate is derived on the basis of energy approach. A finite element model to describe dynamic performances of the plate is developed and used along with an optimization algorithm in order to determine the optimal topologies of constrained layer damping layout on the plate. The damping of visco-elastic layer is modeled by the complex modulus formula. Considering the vibration and energy dissipation mode of the plate with constrained layer damping treatment, damping material density and volume factor are considered as design variable and constraint respectively. Meantime, the modal damping ratio of the plate is assigned as the objective function in the topology optimization approach. The sensitivity of modal damping ratio to design variable is further derived and Method of Moving Asymptote (MMA) is adopted to search the optimized topologies of constrained layer damping layout on the plate. Numerical examples are used to demonstrate the effectiveness of the proposed topology optimization approach. The results show that vibration energy dissipation of the plates can be enhanced by the optimal constrained layer damping layout. This optimal technology can be further extended to vibration attenuation of sandwich cylindrical shells which constitute the major building block of many critical structures such as cabins of aircrafts, hulls of submarines and bodies of rockets and missiles as an invaluable design tool.

Sign in / Sign up

Export Citation Format

Share Document