A New Damping Model for Nonlinear Stiffness Systems With Variable Preload Displacements and Constant Amplitude Decay Ratios

1994 ◽  
Vol 116 (1) ◽  
pp. 257-263 ◽  
Author(s):  
T. Xu ◽  
G. G. Lowen
Keyword(s):  
Energy Loss ◽  
Mathematical Description ◽  
Nonlinear Damping ◽  
Damping Coefficient ◽  
Nonlinear Stiffness ◽  
Constant Amplitude ◽  
Damping Force ◽  
Damping Model ◽  
Good Agreement

This study of the behavior of nonlinear stiffness systems with variable preload displacements and constant amplitude decay ratios showed that the energy loss per cycle is dependent on these preload displacements. By introducing a nonlinear damping force, which is a function of both displacement and velocity, the associated work per cycle can be made approximately the same function of the preload displacement as is the case for the energy loss. In this manner, it becomes possible to make the resulting damping coefficient essentially independent of the preload displacement. This new damping model was incorporated into the mathematical description of an over-running sprag clutch. Confirming experimentation showed very good agreement with computed results.

A New Damping Model for Non-Linear Stiffness Systems With Variable Preload Displacements and Constant Amplitude Decay Ratios

1992 ◽  
Author(s):  
T. Xu ◽  
G. G. Lowen
Keyword(s):  
Energy Loss ◽  
Mathematical Description ◽  
Damping Coefficient ◽  
Constant Amplitude ◽  
Damping Force ◽  
Non Linear ◽  
Linear Damping ◽  
Damping Model ◽  
Good Agreement

Abstract This study of the behavior of non-linear stiffness systems with variable preload displacements and constant amplitude decay ratios showed that the energy loss per cycle is dependent on these preload displacements. By introducing a non-linear damping force, which is a function of both displacement and velocity, the associated work per cycle can be made approximately the same function of the preload displacement as is the case for the energy loss. In this manner, it becomes possible to make the resulting damping coefficient essentially independent of the preload displacement. This new damping model was incorporated into the mathematical description of an over-running sprag clutch. Confirming experimentation showed very good agreement with computed results.

A Study of the Roll Motion by Means of a Free Decay Test

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Hamid Zeraatgar ◽  
Mohsen Asghari ◽  
Firooz Bakhtiari-Nejad
Keyword(s):  
Damping Ratio ◽  
Nonlinear Damping ◽  
Damping Coefficient ◽  
Roll Motion ◽  
Damping Force ◽  
Restoring Force ◽  
Cubic Form ◽  
Damping Coefficients ◽  
Decay Test ◽  
Nonlinear Form

In this study, a method for the extraction of damping by tracing free roll decay is presented. For this purpose, in calm waters, a bulk carrier model is given a large initial roll angle and then released. Consequently, the roll motion is recorded. Restoring coefficients and virtual moments of inertia for the model are determined by means of an inclining test and recording the damped period, respectively. The linear damping coefficient is evaluated by using the damping ratio. Four different forms of combinations of restoring moment and damping coefficient are assumed in order to determine the nonlinear form of the roll motion. These equations are numerically solved for various damping coefficients and results are compared with the experimental data. By virtue of this comparison, the damping coefficients are determined for each case. It may be concluded that the use of the nonlinear restoring moment, which is an odd polynomial of the fifth order, and the cubic form for the nonlinear damping moment best fits the roll behavior for the ship model. The amount of energy dissipated by the damping moments is also calculated in the time domain. The energy method also confirms that the nonlinear form of restoring force in conjunction with the cubic form of the damping force is the best solution of the roll motion for small to large angles.

scholarly journals Displacement Transmissibility Characteristics of Harmonically Base Excited Damper Isolators with Mixed Viscous Damping

2013 ◽  
Vol 20 (5) ◽  
pp. 921-931 ◽  
Author(s):  
Xiaojuan Sun ◽  
Jianrun Zhang
Keyword(s):  
Damping Ratio ◽  
Harmonic Balance Method ◽  
Nonlinear Damping ◽  
Viscous Damping ◽  
Damping Force ◽  
Response Characteristics ◽  
Damping Characteristics ◽  
Linear Damping ◽  
Frequency Ratios ◽  
Good Agreement

The viscous damping force in the mixed form asfd(x˙)=c1x˙+c2|x˙|x˙can well describe damping characteristics of isolators and dampers in many cases. In this paper, performance characteristics of single-degree-of-freedom (SDOF) linear-stiffness isolators with mixed and piecewise mixed viscous damping are analytically examined under harmonic base excitation. Based on the first-order harmonic balance method (HBM), both relative and absolute displacement transmissibility expressions with the equivalent linear damping coefficient (ELDC) are given. And the analytical calculations show good agreement with the numerical results. Also, the influence of nonlinear damping on the response characteristics is investigated by comparing the transmissibility of linear and nonlinear systems. The resonant frequency always shifts to a lower value as the nonlinear damping component of the forcefd(x˙)=c1x˙+c2|x˙|x˙becomes stronger, and when the damping ratio in the corresponding linear model is relatively high, the relative transmissibility decreases at frequencies higher than the resonance frequency of the corresponding linear damping system and the absolute one increases for the frequency ratios above2. Finally, the displacement transmissibility of a nonlinear isolator with piecewise mixed viscous damping is discussed and the process shows research similarity with the non-piecewise case.

Parametric Study of Damping Characteristics of Magneto-Rheological Damper: Mathematical and Experimental Approach

2020 ◽  
Vol 15 (3) ◽  
pp. 37-48
Author(s):  
Zubair Rashid Wani ◽  
Manzoor Ahmad Tantray
Keyword(s):  
Structural Control ◽  
Research Work ◽  
Testing Machine ◽  
Input Voltage ◽  
Damping Coefficient ◽  
Control Technique ◽  
Damping Force ◽  
Active Devices ◽  
Active Structural Control ◽  
Magneto Rheological

The present research work is a part of a project was a semi-active structural control technique using magneto-rheological damper has to be performed. Magneto-rheological dampers are an innovative class of semi-active devices that mesh well with the demands and constraints of seismic applications; this includes having very low power requirements and adaptability. A small stroke magneto-rheological damper was mathematically simulated and experimentally tested. The damper was subjected to periodic excitations of different amplitudes and frequencies at varying voltage. The damper was mathematically modeled using parametric Modified Bouc-Wen model of magneto-rheological damper in MATLAB/SIMULINK and the parameters of the model were set as per the prototype available. The variation of mechanical properties of magneto-rheological damper like damping coefficient and damping force with a change in amplitude, frequency and voltage were experimentally verified on INSTRON 8800 testing machine. It was observed that damping force produced by the damper depended on the frequency as well, in addition to the input voltage and amplitude of the excitation. While the damping coefficient (c) is independent of the frequency of excitation it varies with the amplitude of excitation and input voltage. The variation of the damping coefficient with amplitude and input voltage is linear and quadratic respectively. More ever the mathematical model simulated in MATLAB was in agreement with the experimental results obtained.

Application of Semi-Active Oil Damper System to Base Isolation Systems

2002 ◽  
Author(s):  
Takashi Kawai ◽  
Yasuo Tsuyuki ◽  
Yutaka Inoue ◽  
Osamu Takahashi ◽  
Koji Oka
Keyword(s):  
Base Isolation ◽  
Shaking Table ◽  
The Other ◽  
Damping Coefficient ◽  
Damping Force ◽  
Mass Model ◽  
Maximum Acceleration ◽  
Rubber Bearing ◽  
Single Mass ◽  
Isolation Systems

This paper deals with one of the applications of the Semi-Active Oil Damper system, which applies base isolation systems reducing the maximum acceleration. The theory of the Semi-Active Oil Damper system is based on Karnopp Theory. The theory has been actually now in use for a Semi-active suspension system of the latest Shinkansen (New trunk lines) trains to improve passenger’s comfortable riding. Various experiments have been conducted using a single mass model whose weight is 15 ton on the shaking table. This model is supported by the rubber bearing. The natural frequency is 0.33Hz of this system. Two Semi-Active Oil Damper were installed in the model and excited the table for one horizontal direction. The maximum damping force of each Semi-Active Oil Damper used for the model is 4.21 kN. The damper can change the damping coefficient by utilizing two solenoid valves. Therefore, the dynamic characteristic of the damping force has two modes. One is a hard damping coefficient and the other is a soft one. It was confirmed that the maximum acceleration of the Semi-Active Oil Damper system can be reduced more than 20% in comparison with the passive Oil Damper system in our tests.

scholarly journals A Method of Predicting the Energy Losses in Vaneless Diffusers of Centrifugal Compressors

1989 ◽  
Author(s):  
Huashu Dou
Keyword(s):  
Experimental Data ◽  
Energy Loss ◽  
Total Energy ◽  
Wall Friction ◽  
Energy Losses ◽  
Flow Conditions ◽  
Centrifugal Compressors ◽  
Flow Losses ◽  
Vaneless Diffusers ◽  
Good Agreement

The flow losses in the veneless diffusers of centrifugal compressors is investigated. It is found that the total energy loss in vaneless diffusers is a function of Bsin2 α0 when inlet flow conditions and radius ratio between inlet and outlet are given. A wall friction coefficient equation is derived and a method of predicting the total energy loss excepting mixing loss is presented. A comparison is made between results obtained from this method and experimental data generated by the author as well as data from the literature. Good agreement is obtained.

A Comparison of the Effects of Nonlinear Damping on the Free Vibration of a Single-Degree-of-Freedom System

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Bin Tang ◽  
M. J. Brennan
Keyword(s):  
Free Vibration ◽  
Equations Of Motion ◽  
Nonlinear Damping ◽  
Degree Of Freedom ◽  
Damping Force ◽  
Single Degree Of Freedom ◽  
Sdof System ◽  
Single Degree ◽  
Dependent Term ◽  
Quadratic Damping

This article concerns the free vibration of a single-degree-of-freedom (SDOF) system with three types of nonlinear damping. One system considered is where the spring and the damper are connected to the mass so that they are orthogonal, and the vibration is in the direction of the spring. It is shown that, provided the displacement is small, this system behaves in a similar way to the conventional SDOF system with cubic damping, in which the spring and the damper are connected so they act in the same direction. For completeness, these systems are compared with a conventional SDOF system with quadratic damping. By transforming all the equations of motion of the systems so that the damping force is proportional to the product of a displacement dependent term and velocity, then all the systems can be directly compared. It is seen that the system with cubic damping is worse than that with quadratic damping for the attenuation of free vibration.

Dynamic Property Analysis of Damping Rubber in Rail Fastenings under Different Deformation Condition

2014 ◽  
Vol 494-495 ◽  
pp. 706-710
Author(s):  
Bin Zhang ◽  
Yan Yun Luo ◽  
Zhi Nan Shi
Keyword(s):  
Mechanical Model ◽  
Dynamic Stiffness ◽  
Excitation Frequency ◽  
Nonlinear Damping ◽  
Deformation Condition ◽  
Damping Force ◽  
Restoring Force ◽  
Dynamic Mechanical ◽  
Large Distortion ◽  
Hydraulic Servo

This paper studies the experimental research on dynamic characteristics of the damping rubber in high elastic fastening by the electro-hydraulic servo movement tester. Based on a hypothesis superposition theory of nonlinear elastic restoring force and nonlinear damping force, a non-linear dynamic mechanical model is proposed. The dynamic stiffness and damping parameters of the rubber are obtained in different deformation conditions based on the dynamic mechanical model. The dynamic stiffness is analyzed, and the results show that dynamic stiffness is closely related to excitation frequency and amplitude. Furthermore the dynamic stiffness is analyzed under different free surface of rubber components by using FEM. That also reveals the changeable characteristics and affected factors of the damping rubber of the high elastic fastenings in large distortion condition.

Reduced-Order Nonlinear Damping Model: Formulation and Application to Postflutter Aeroelastic Behavior

AIAA Journal ◽  
2021 ◽  
pp. 1-11
Author(s):  
X. Q. Wang ◽  
Pengchao Song ◽  
Marc P. Mignolet ◽  
P. C. Chen
Keyword(s):  
Nonlinear Damping ◽  
Model Formulation ◽  
Reduced Order ◽  
Damping Model
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