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1 – 10 of over 2000
Article
Publication date: 1 October 2002

Jinwu Xiang, Guocai Hu and Xiaogu Zhang

An equivalent linear damping model is developed for forward flight condition, with the flap/lag/pitch kinematics and nonlinear characteristics of hydraulic damper taken into…

1176

Abstract

An equivalent linear damping model is developed for forward flight condition, with the flap/lag/pitch kinematics and nonlinear characteristics of hydraulic damper taken into account. Damper axial velocity is analyzed from the velocities of the damper‐to‐blade attachment point in time domain. For the case of blade lead‐lag oscillations without forced excitation and kinematics, the equivalent linear damping is calculated from transient response with energy balance method, Fourier series based moving block analysis and Hilbert transform based technology, respectively. Results indicate that equivalent linear damping decreases significantly with lead‐lag forced excitation and flap/lag/pitch kinematics, especially with the latter in flight condition.

Details

Aircraft Engineering and Aerospace Technology, vol. 74 no. 5
Type: Research Article
ISSN: 0002-2667

Keywords

Article
Publication date: 30 July 2020

Xu Li, Jun Li, Xiaoyi Zhang, Jianfeng Gao and Chao Zhang

Viscous dampers are commonly used in large span cable-stayed bridges to mitigate seismic effects and have achieved great success.

Abstract

Purpose

Viscous dampers are commonly used in large span cable-stayed bridges to mitigate seismic effects and have achieved great success.

Design/methodology/approach

However, the nonlinear analysis on damper parameters is usually computational intensive and nonobjective. To address these issues, this paper proposes a simplified method to determine the viscous damper parameters for double-tower cable-stayed bridges. An empirical formula of the equivalent damping ratio of viscous dampers is established through decoupling nonclassical damping structures and linearization of nonlinear viscous dampers. Shaking table tests are conducted to verify the feasibility of the proposed method. Moreover, this simplified method has been proved in long-span cable-stayed bridges.

Findings

The feasibility of this method is verified by the simplified model shaking table test. This simplified method for determining the parameters of viscous dampers is verified in cable-stayed bridges with different spans.

Originality/value

This simplified method has been validated in cable-stayed bridges with various spans.

Details

Engineering, Construction and Architectural Management, vol. 27 no. 8
Type: Research Article
ISSN: 0969-9988

Keywords

Article
Publication date: 13 November 2017

Zhiwei Wang, Yi Liu and Feng Wang

The purpose of this paper is to establish a simplified model of the closed hydrostatic guideway for the rapid analysis of static and dynamic characteristics. Further, the…

Abstract

Purpose

The purpose of this paper is to establish a simplified model of the closed hydrostatic guideway for the rapid analysis of static and dynamic characteristics. Further, the influence of compressibility and dynamic frequency are taken into consideration in the new dynamic model.

Design/methodology/approach

The new model is based on the second kind of Lagrange equation. In this model, the closed hydrostatic guideway is supported by 12 pads, and each oil pad is equivalent to a nonlinear spring-damper system. The equivalent spring coefficient and damper coefficient of the oil pad are extracted by the three different equivalent methods. Finally, the validation experiments of step load response and dynamic stiffness are conducted on a hydrostatic guideway.

Findings

For solving the step response, the linear spring-damper model and the nonlinear spring-damper Model 1 are better than the nonlinear spring-damper Model 2. The accuracy of the three methods are very high for static stiffness calculation. For the calculation of dynamic stiffness, the nonlinear spring-damper Model 2 is better than the nonlinear spring-damper Model 1. The linear spring-damper model has low precision for dynamic stiffness calculation, especially at high frequency. The accuracy of the new model is validated by experiments.

Originality/value

The equivalent method of nonlinear spring-damper system has higher accuracy. Different equivalent methods should be adopted for different load types. The computational speeds of the new dynamic model with the three methods are much better than finite element method (about ten times).

Details

Industrial Lubrication and Tribology, vol. 69 no. 6
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 1 January 1986

S. Rakheja and S. Sankar

The non‐linear damping mechanisms are expressed in two general forms: velocity dependent and displacement dependent. The non‐linear damping phenomena are expressed by an array of…

Abstract

The non‐linear damping mechanisms are expressed in two general forms: velocity dependent and displacement dependent. The non‐linear damping phenomena are expressed by an array of ‘local constants’, whose value depends upon excitation frequency, excitation amplitude, and type of non‐linearity. Thus, the non‐linear system is replaced by several localized linear systems corresponding to every discrete frequency and amplitude of excitation. Each of the localized linear systems, thus formulated, characterizes the response behaviour of the original non‐linear system, quite accurately in the vicinity of the specific frequency and amplitude of excitation. An algorithm is developed, which expresses the non‐linear damping by an array of ‘local constants’. The algorithm then employs the usual linear design tools to generate the response characteristics almost identical to the response behaviour of the non‐linear system.

Details

Engineering Computations, vol. 3 no. 1
Type: Research Article
ISSN: 0264-4401

Article
Publication date: 1 April 1991

S. RAKHEJA and A.K.W. AHMED

A local equivalent linearization methodology is proposed to simulate non‐linear shock absorbers and dual‐phase dampers in the convenient frequency domain. The methodology based on…

Abstract

A local equivalent linearization methodology is proposed to simulate non‐linear shock absorbers and dual‐phase dampers in the convenient frequency domain. The methodology based on principle of energy similarity, characterizes the non‐linear dual‐phase dampers via an array of local damping constants as function of local excitation frequency and amplitude, response, and type of non‐linearity. The non‐linear behaviour of the dual‐phase dampers can thus be predicted quite accurately in the entire frequency range. The frequency response characteristics of a vehicle model employing non‐linear dual‐phase dampers, evaluated using local linearization algorithm, are compared to those of the non‐linear system, established via numerical integration, to demonstrate the effectiveness of the algorithm. An error analysis is performed to quantify the maximum error between the damping forces generated by non‐linear and locally linear simulations. The influence of damper parameters on the ride improvement potentials of dual‐phase dampers is further evaluated using the proposed methodology and discussed.

Details

Engineering Computations, vol. 8 no. 4
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 5 August 2019

Min Zhang and Dongzhuo Wang

This paper aims to study the seismic response of frame structure with friction dampers.

168

Abstract

Purpose

This paper aims to study the seismic response of frame structure with friction dampers.

Design/methodology/approach

The state equation of the structure subjected to the earthquake is presented and solved, from which the maximum drift and the interlayer drift angle of the floors of the structure subjected to the seismic waves of four types of sites are analyzed.

Findings

The result indicates that the damping effect is significant on the floors with the friction damper but is almost little influence on the other floor.

Originality/value

The result indicates that the damping effect is significant on the floors with the friction damper but is almost little influence on the other floor.

Details

Engineering Computations, vol. 36 no. 7
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 19 May 2023

Cheng Xue, Zhaowang Xia, Xingsheng Lao and Zhengqi Yang

The purpose of this study is to provide some references about applying the semi-active particle damper to enhance the stability of the pipe structure.

72

Abstract

Purpose

The purpose of this study is to provide some references about applying the semi-active particle damper to enhance the stability of the pipe structure.

Design/methodology/approach

This paper establishes the dynamical models of semi-active particle damper based on traditional dynamical theory and fractional-order theory, respectively. The semi-active particle damping vibration isolation system applied in a pipe structure is proposed, and its analytical solution compared with G-L numerical solution is solved by the averaging method. The quantitative relationships of fractional-order parameters (a and kp) are confirmed and their influences on the amplitude-frequency response of the vibration isolation system are analyzed. A fixed point can be obtained from the amplitude-frequency response curve, and the optimal parameter used for improving the vibration reduction effect of semi-active particle damper can be calculated based on this point. The nonlinear phenomenon caused by nonlinear oscillators is also investigated.

Findings

The results show that the nonlinear stiffness parameter p will cause the jump phenomenon while p is close to 87; with the variation of nonlinear damping parameter μ, the pitchfork bifurcation phenomenon will occur with an unstable branch after the transient response; with the change of fractional-order coefficient kp, a segmented bifurcation phenomenon will happen, where an interval that kp between 18.5 and 21.5 has no bifurcation phenomenon.

Originality/value

This study establishes a mathematical model of the typical semi-active particle damping vibration isolation system according to fractional-order theory and researches its nonlinear characteristics.

Article
Publication date: 17 May 2022

Massicilia Dahmani, Abdelghani Seghir, Nabil Issaadi and Ouali Amiri

This study aims to propose a numerical modeling procedure for response analysis of elastic body floating in water and submitted to regular waves. An equivalent simplified…

Abstract

Purpose

This study aims to propose a numerical modeling procedure for response analysis of elastic body floating in water and submitted to regular waves. An equivalent simplified mechanical single-degree-of-freedom system allowing to reproduce the heave movements is first developed, then the obtained lumped characteristics are used for elastic analysis of the floating body in heave motion.

Design/methodology/approach

First, a two-dimensional numerical model of a rigid floating body in a wave tank is implemented under DualSPHysics, an open source computational fluid dynamics (CFD) code based on smoothed particle hydrodynamics method. Then, the obtained results are exploited to derive an equivalent mechanical mass-spring-damper model. Finally, estimated equivalent characteristics are used in a structural finite element modeling of the considered body assuming elastic behavior.

Findings

Obtained results concerning the floating body displacements are represented and validated using existing experimental data in the literature. Wave forces acting on the body are also evaluated. It was found that for regular waves, it is possible to replace the complex CFD refined model by an equivalent simplified mechanical system which makes easy the use of structural finite element analysis.

Originality/value

The originality of this work lies in the proposed procedure to evaluate the mechanical properties of the equivalent elastic system. This allows to couple two different software tools and to take advantages of their features.

Details

World Journal of Engineering, vol. 20 no. 5
Type: Research Article
ISSN: 1708-5284

Keywords

Article
Publication date: 1 March 1960

D.J. Mead

The theory is presented of the increase in damping that can be obtained when a damping compound is added to a simple structure vibrating in a bending mode. Consideration has been…

Abstract

The theory is presented of the increase in damping that can be obtained when a damping compound is added to a simple structure vibrating in a bending mode. Consideration has been given to the use of ‘Aquaplas’ damping compound on a vibrating stringer‐skin combination, and it has been shown that the maximum damping ratio is obtained when the material is applied to the stringer flange over the centre 40 per cent of the pin‐ended length of the beam. A preliminary experimental investigation is described, in which damping measurements were made on a simple structural specimen treated with Aquaplas. A new method was used successfully to determine the damping ratio of a heavily damped system. The damping properties of Aquaplas were evaluated, and some of the theoretical conclusions were verified. Some of the results obtained indicate that a more accurate mathematical representation must be sought for the visco‐elastic behaviour of Aquaplas than is provided by the ‘complex stiffness’ method.

Details

Aircraft Engineering and Aerospace Technology, vol. 32 no. 3
Type: Research Article
ISSN: 0002-2667

Article
Publication date: 1 February 1959

W.E. Hooper

The equations of motion developed by R. P. Coleman have been evaluated for a particular helicopter configuration and a large number of different combinations of rotor and fuselage…

Abstract

The equations of motion developed by R. P. Coleman have been evaluated for a particular helicopter configuration and a large number of different combinations of rotor and fuselage damping. These results are displayed graphically and reveal the dependence of the unstable range on rotor and fuselage damping. Some of the conclusions are in disagreement with those reached by Coleman. Both viscous and friction rotor dampers are considered.

Details

Aircraft Engineering and Aerospace Technology, vol. 31 no. 2
Type: Research Article
ISSN: 0002-2667

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