Wave component solutions of free vibration and mode damping loss factor of finite length periodic beam structure with damping material

2018 ◽  
Vol 201 ◽  
pp. 740-746 ◽  
Author(s):  
Yongbin Ma ◽  
Kai Zhang ◽  
Zichen Deng
Keyword(s):  
Free Vibration ◽  
Finite Length ◽  
Loss Factor ◽  
Wave Component ◽  
Beam Structure ◽  
Damping Material ◽  
Damping Loss Factor

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.

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.

A strengthening approach for damping property and shape memory property of acrylic rubber/polylactide blends

2018 ◽  
Vol 51 (7-8) ◽  
pp. 626-643
Author(s):  
Chengliang Li ◽  
Xingxing Ji ◽  
Yang Lyu ◽  
Xinyan Shi
Keyword(s):  
Shape Memory ◽  
Loss Factor ◽  
Phenol Formaldehyde ◽  
Mechanical Analysis ◽  
Damping Properties ◽  
Shape Memory Property ◽  
Memory Property ◽  
Damping Material ◽  
Shape Memory Properties ◽  
Shape Memory Effects

In this work, a damping material was successfully prepared by blending acrylic rubber (ACM) and polylactide (PLA) with sulfur and soap salt as the curing agents. A phenol-formaldehyde (PF) resin was used as a modifier. The effects of PF on the mechanical properties, damping properties, compatibility and shape memory properties of the blends were studied. The compatibility and damping properties were characterized by dynamic mechanical analysis, Fourier transform infrared spectroscope and microstructure analysis. The shape memory properties were examined by thermal mechanical analyser. The results revealed that the tensile strength of the blends was decreased and the toughness was increased with the increase of PF loadings. The introduction of PF improved the compatibility between PLA and ACM, which was deduced from the fact that the glass transition temperature of ACM was increased and the two loss factor peaks became closer. It was also found that the loss factor peak became higher and the effective damping temperature range became wider due to the formation of hydrogen bonding, implying that the damping properties of ACM/PLA blends were significantly improved. The ACM/PLA blends exhibited good dual-shape memory effect and its shape recovery ratio was increased by introduction of PF and raising the trigger temperature. The blends also exhibited good triple-shape memory property, which was dramatically improved by the introduction of PF. The mechanisms for the enhanced shape memory effects were then analysed.

A New Methodology for the Accurate and Consistent Identification of Modal Parameters Using Multi-FRF Analysis

1995 ◽  
Author(s):  
R. M. Lin ◽  
S.-F. Ling
Keyword(s):  
Eigenvalue Problem ◽  
Loss Factor ◽  
Frequency Response Function ◽  
Natural Frequencies ◽  
Identification Problem ◽  
Modal Parameters ◽  
Frequency Range ◽  
Case Examples ◽  
Measured Frequency Response ◽  
Damping Loss Factor

Abstract A new method for the estimation of modal parameters is presented in this paper. Unlike the majority of the existing methods which involve complicated curve fitting and interpolative procedures, the proposed method calculates the modal parameters by solving eigenvalue problem of an equivalent eigensystem derived from measured frequency response function (FRF) data. It is developed based on the practical assumption that only one incomplete column of the FRF matrix of the test structure has been measured in a frequency range of interest. All the measured FRFs are used simultaneously to construct the equivalent eigensystem matrices from which natural frequencies, damping loss factor and modeshape vectors of interest can be directly solved. Since the identification problem is reduced to an eigenvalue problem of an equivalent system, natural frequencies and damping loss factors identified are consistent. Further procedures for normalizing the identified eigenvectors so that they become mass-normalized are developed. Numerical case examples are given to demonstrate the practicality of the proposed method and results obtained are indeed very promising. It is believed that with the availability of such identification method, modal analysts’ dream of intelligent and full automatic modal analysis will become a reality.

An efficient semi-analytical static and free vibration analysis of laminated and sandwich beams based on linear elasticity theory

2021 ◽  
pp. 030932472110626
Author(s):  
Zhao Yin ◽  
Hangduo Gao ◽  
Gao Lin
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Free Vibration ◽  
Mechanical Load ◽  
Geometric Model ◽  
Free Vibration Analysis ◽  
Sandwich Beams ◽  
Beam Structure ◽  
Precise Integration ◽  
Element Method

Based on the two-dimensional (2D) elastic theory without enforcing any beam assumption, an efficient semi-analytical scaled boundary finite element method (SBFEM) is proposed to solve the bending and free vibration responses of composite laminated and sandwich beams under the mechanical load. The scaled center is placed at infinity, which produces the accurate result by discretizing only the longitudinal direction of the beam structure treated as a one-dimensional (1D) discretization problem. A new kind of 1D high-order spectral element shape functions with the advantages of high accuracy and superior convergence is introduced in SBFEM coordinate system to approximate the geometric model and corresponding variables. The principle of weighted residual in conjunction with the Green’s theorem are applied to obtain the SBFEM governing equation of each layer with respect to radial displacement fields. The solution of equation is indicated analytically by a matrix exponential function, which can be accurately solved by using the precise integration technique (PIT). Finally, an effective and simple stiffness matrix is obtained. By comparing two examples with the solutions based on the finite element method (FEM), the results show that the proposed method has good accuracy and rapid convergence with only a few meshes. The numerical examples are given to investigate the parametric effects of the stacking sequence, thickness ratio, boundary condition, and load form on the variation of the displacement, stress and natural frequency. The results validate that the present technique is also applicable to the complex beam structure with softcore layer inside.

The Backing Design in the Free Damping Cylindrical Shell Damping Test

2013 ◽  
Vol 437 ◽  
pp. 475-480
Author(s):  
Bang Hui Yin ◽  
Min Qing Wang
Keyword(s):  
Cylindrical Shell ◽  
Energy Method ◽  
Design Problem ◽  
Loss Factor ◽  
Cylindrical Shells ◽  
Harmonic Response ◽  
Different Types ◽  
Damping Loss Factor

The ANSYS harmonic response results are post-processed with the energy method to obtain the damping loss factor (DLF) of different types of free damping structures. Firstly, the DLF of free damping cylindrical shell in air is compared with DLF of free damping plate in air. Secondly, the DLF of free damping cylindrical shell with stiffened ribs in air is compared with that without stiffened ribs in air. Thirdly, the DLF of free damping cylindrical shell in water is compared with the DLF of free damping plate in water. Fourthly, the DLF of free damping cylindrical shell with stiffened ribs in water is compared with that without stiffened ribs in water. In the end, based on the above analysis, the backing design problem in air and water are discussed. Studies have shown that: DLF of free damping cylindrical shell is close to that of free damping plate in air; DLF of free damping cylindrical shell with stiffened ring ribs is close to that without stiffened ring ribs in air; When testing free damping cylindrical shells DLF in air, plate with the same thickness can be used as the backing; DLF of free damping plate is close to that of free damping cylindrical shell in water; DLF of free damping cylindrical shell with stiffened ring ribs is close to that without stiffened ring ribs in water; When testing free damping cylindrical shells DLF in water, plate with the same thickness can be used as the backing.

Experimental Determination of the Damping Loss Factor of Highly Damped Ribbed-Stiffened Panels

2008 ◽  
Author(s):  
Jesús Ortiz Martinez ◽  
Márcio Calçada ◽  
Roberto Jordan ◽  
Samir N. Y. Gerges
Keyword(s):  
Experimental Determination ◽  
Loss Factor ◽  
Stiffened Panels ◽  
Damping Loss Factor

Measurement of SEA damping loss factor for complex structures

2008 ◽  
Vol 123 (5) ◽  
pp. 3060-3060 ◽  
Author(s):  
Maxime Bolduc ◽  
Noureddine Atalla
Keyword(s):  
Loss Factor ◽  
Complex Structures ◽  
Damping Loss Factor
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