New Methods for Nonlinear Damping Identification of Damping Alloy

2007 ◽  
Vol 129 (5) ◽  
pp. 678-684 ◽  
Author(s):  
Ziying Wu ◽  
Hongzhao Liu ◽  
Lilan Liu ◽  
Daning Yuan
Keyword(s):  
Stress Field ◽  
Autoregressive Model ◽  
Nonlinear Behavior ◽  
Nonlinear Damping ◽  
Internal Damping ◽  
New Methods ◽  
Uniform Stress Field ◽  
Nonuniform Stress Field ◽  
Nonlinear Internal Damping ◽  
Versus Strain

This paper presents two methods for the identification of nonlinear internal damping of alloy. One is the moving autoregressive model (MARM) method, and the other is the time-varying autoregressive model (TVARM) method. These procedures have been successfully implemented on two numerical examples. Comparison between simulation results demonstrates that the computation accuracy of the TVARM method is higher than that of the MARM method. In the experiments, the internal damping properties of the alloy Al-33Zn-6Si are researched, employing the rectangle beam with a nonuniform stress field and the trapezoid beam with a quasi-uniform stress field, respectively. Experimental results show that the internal damping of the alloy increases with the increasing strain and appears a nonlinear behavior. Moreover, the damping values of the trapezoid beam are relatively higher than those of the rectangle beam. Compared to the MARM method, the TVARM method can give a better description of nonlinear damping because the relation curve of loss factor versus strain obtained by the TVARM method is smoother than that obtained by the MARM method.

Research on Nonlinear Damping Characteristics of Damping Alloy With Uniform Stress Field

Volume 1 ◽  
2004 ◽  
Author(s):  
Hongzhao Liu ◽  
Ziying Wu ◽  
Lilan Liu ◽  
Daning Yuan ◽  
Zhongming Zhang
Keyword(s):  
Stress Field ◽  
Nonlinear Function ◽  
Nonlinear Damping ◽  
Damping Capacity ◽  
Internal Damping ◽  
Uniform Stress ◽  
Nonlinear Relation ◽  
Uniform Stress Field ◽  
Half Power ◽  
Versus Strain

For the high damping metal material like damping alloy, the damping capacity usually changes with the strain amplitude and frequency nonlinearly. First, to extract the pattern of the internal damping versus strain, two time-domain calculation methods are presented in this paper. One is the moving exponent method (MEM for short) based on FFT (MEM+FFT) and the other is the moving autoregressive model method (MARM). The computing accuracy of the two methods has been compared through numerical simulations. The nonlinear relation curve of loss factor versus strain is achieved by the impulse excitation experiment employing uniform stress field. Then, to extract the pattern of the internal damping versus vibrating frequency, the sine sweep-frequency excitation experiment based on the half-power bandwidth method is carried out. The resulting curve indicates that the internal damping is also a nonlinear function of frequency.

Research on the Identification of Nonlinear Internal Damping and Kinematical Joint Damping of Mechanical Systems

Tribology ◽  
2005 ◽  
Author(s):  
Ziying Wu ◽  
Hongzhao Liu ◽  
Lilan Liu ◽  
Daning Yuan
Keyword(s):  
Free Vibration ◽  
Coulomb Friction ◽  
Characteristic Curve ◽  
Nonlinear Damping ◽  
Internal Damping ◽  
Window Method ◽  
Joint Damping ◽  
Alloy Material ◽  
Nonlinear Internal Damping ◽  
Simultaneous Identification

A simultaneous identification method of the nonlinear internal damping of alloy material and the Coulomb friction in the kinematical joints in a mechanical system is put forward in this paper. The free vibration differential equation of a vibration system with these two kinds of damping is established. According to the free vibration response signal, the nonlinear internal damping characteristic curve and the Coulomb friction are got by using the moving rectangle window method. Several types of the nonlinear damping models are investigated in simulations. The validity and accuracy of the proposed method are illustrated by the good simulation results, in which the computing accuracy of the nonlinear internal damping is higher than that of the Coulomb damping in kinematical joints.

Optimal decay of an abstract nonlinear viscoelastic equation in Hilbert spaces with delay term in the nonlinear internal damping

2020 ◽  
pp. 1-30
Author(s):  
Houria Chellaoua ◽  
Yamna Boukhatem ◽  
Baowei Feng
Keyword(s):  
Hilbert Spaces ◽  
Nonlinear Damping ◽  
Delayed Feedback ◽  
Internal Damping ◽  
General Decay Rate ◽  
Delay Term ◽  
Nonlinear Viscoelastic ◽  
Optimal Decay ◽  
Viscoelastic Equation ◽  
Nonlinear Internal Damping

In this paper, we consider a second-order abstract viscoelastic equation in Hilbert spaces with delay term in the nonlinear internal damping and a nonlinear source term. Under some suitable assumptions on the weight of the delayed feedback, the weight of the non-delayed feedback and the behavior of the relaxation function, we establish two explicit and general decay rate results of the energy by introducing a suitable Lyaponov functional and some properties of the convex functions. Moreover, we give some applications and examples. This work generalizes the previous results without time delay term to those with delay in the nonlinear damping.

Stability of a Simple Rotor With Nonlinear Internal Damping

1991 ◽  
Author(s):  
Erik Medgyesi
Keyword(s):  
Stability Analysis ◽  
Numerical Methods ◽  
Hysteresis Loop ◽  
Nonlinear Damping ◽  
Internal Damping ◽  
Nonlinear Internal Damping

Abstract The paper contains a stability analysis of the assumed inplane motion of a simple rotor with nonlinear damping, the form of which can approximate different hysteresis loop shapes. The analysis is carried so far as possible without resorting to numerical methods.

Computing of Nonlinear Damping Using the Moving Autoregressive Model Method

Volume 1 ◽  
2004 ◽  
Author(s):  
Ziying Wu ◽  
Hongzhao Liu ◽  
Lilan Liu ◽  
Daning Yuan ◽  
Zhongming Zhang
Keyword(s):  
Autoregressive Model ◽  
Loss Factor ◽  
Low Frequency ◽  
Nonlinear Behavior ◽  
Nonlinear Damping ◽  
Three Dimension ◽  
Model Method ◽  
Alloy Material ◽  
Natural Characteristic ◽  
The Relationship

Strictly speaking, internal damping of alloy materials is a function of temperature, frequency, strain and strain time rate and so on. Most of the previous papers with regard to damping computing only give a volumetric average when the alloy material is subjected to alternative stress. They cannot accurately describe the natural characteristic of damping. In this paper, the moving autoregressive model method (MARM) is presented to research the relationship between loss factor, strain and frequency of the alloys (Al-33Zn-6Si and Zn-27Al-1Cu). The experimental results show that the loss factor of alloy increases with the increasing strain, and increases with the increasing frequency in low-frequency region (below 400Hz). The damping appears strong nonlinear behavior. The three-dimension graph of the loss factor versus strain and frequency provides useful information for the optimum design of machine parts made from damping alloy.

Assessment of Internal Damping in Uniaxially Stressed Metals: Exponential and Autoregressive Methods

1998 ◽  
Vol 120 (2) ◽  
pp. 177-184 ◽  
Author(s):  
A. L. Audenino ◽  
E. M. Zanetti ◽  
P. M. Calderale
Keyword(s):  
Nonlinear Behavior ◽  
Least Square ◽  
Dissipated Energy ◽  
Exponential Fitting ◽  
Damping Capacity ◽  
Test Machine ◽  
Internal Damping ◽  
Cast Irons ◽  
Decay Signal ◽  
Specific Damping Capacity

When a metallic material is highly stressed, its internal specific damping capacity increases showing a nonlinear behavior. In spite of this, the most part of experimental methods employ nonhomogeneous stress fields measuring only a volumetric average, often called structural damping. To overcome this problem the procedure herein presented extends the applicability of the plain traction or compression methods to higher frequency range (up to 300 Hz). The introduced methodology corrects for elastic energy and dissipated energy relative to the test machine and to the fixtures. The experimental procedure is based on the acquisition of a decay signal when the test machine excitation force has been removed. Two different methods to extract the pattern of internal damping versus material strain have been compared: one is based on least square exponential fitting while the other employs an autoregressive model. Best results have been obtained combining the two techniques taking into account also the variation of Young’s modulus with strain. The resulting curves of the loss factor as a function of strain amplitude for three steels and two cast irons are presented.

The 〈111〉 Elliptic Inclusion in an Anisotropic Solid of Cubic Symmetry

1982 ◽  
Vol 49 (2) ◽  
pp. 353-360 ◽  
Author(s):  
H. C. Yang ◽  
Y. T. Chou
Keyword(s):  
Stress Field ◽  
Uniform Stress ◽  
Elliptic Inclusion ◽  
Cubic Symmetry ◽  
Elastic Fields ◽  
Closed Form Solutions ◽  
Strain Transformation ◽  
Anisotropic Solid ◽  
Uniform Stress Field ◽  
Free Strain

This paper deals with a generalized plane problem in which a uniform stress-free strain transformation takes place in the region of an elliptic cyclinder (the inclusion) oriented in the 〈111〉 direction in an anisotropic solid of cubic symmetry. Closed-form solutions for the elastic fields and the strain energies are presented. The perturbation of an otherwise uniform stress field due to a 〈111〉 elliptic inhomogeneity is also treated including two extreme cases, elliptic cavities and rigid inhomogeneities.

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