Dynamic Analysis and Parameter Identification of a Single Mass Elastomeric Isolation System Using a Maxwell-Voigt Model

2006 ◽  
Vol 128 (6) ◽  
pp. 713-721 ◽  
Author(s):  
Jie Zhang ◽  
Christopher M. Richards
Keyword(s):  
Parameter Identification ◽  
Dynamic Analysis ◽  
Frequency Response ◽  
Natural Frequency ◽  
Damping Ratio ◽  
Response Spectra ◽  
Isolation System ◽  
Single Mass ◽  
Voigt Model ◽  
Stiffness And Damping

Dynamic analysis and parameter identification of a single mass elastomeric isolation system represented by a Maxwell-Voigt model is examined. Influences that the stiffness and damping values of the Maxwell element have on natural frequency, damping ratio, and frequency response are uncovered and three unique categories of Maxwell-type elements are defined. It is also shown that Voigt and Maxwell-Voigt models with equivalent natural frequencies and damping ratios can have considerably different frequency response spectra. Lastly, a parameter identification method is developed for identifying Maxwell-Voigt models from frequency response spectra. The method is based on constant natural frequency and damping ratio curves generated from modal analysis of potential Maxwell-Voigt models.

Mitigation of Vortex-Induced Vibrations of a Pivoted Circular Cylinder Using an Adaptive Pendulum Tuned-Mass Damper

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Sina Kheirkhah ◽  
Richard Lourenco ◽  
Serhiy Yarusevych ◽  
Sriram Narasimhan
Keyword(s):  
Frequency Response ◽  
Natural Frequency ◽  
Damping Ratio ◽  
Tuned Mass Damper ◽  
Single Frequency ◽  
Fundamental Frequencies ◽  
Transverse Vibrations ◽  
Synchronization Region ◽  
Vortex Induced Vibrations ◽  
Mass Damper

A novel adaptive pendulum tuned-mass damper (TMD) was integrated with a two degree-of-freedom (DOF) cylindrical structure in order to control vortex-induced vibrations of the structure. The natural frequency of the TMD was adjusted autonomously in order to control the vortex-induced vibrations. The experiments were performed at a constant Reynolds number of 2100 and for four reduced velocities, 4.18, 5.44, 6.00, and 6.48. Two TMD damping ratios, 0 and 0.24, were investigated for a constant TMD mass ratio of 0.087. The results demonstrate that tuning the natural frequency of the TMD to the natural frequency of the structure decreases the amplitudes of transverse and streamwise vibrations of the structure significantly. Specifically, the transverse amplitudes of vibrations are decreased by a factor of ten and streamwise amplitudes of vibrations are decreased by a factor of three. Depending on the value of the TMD damping ratio, the frequency of transverse vibrations is either characterized by the natural frequency of the structure or by two other fundamental frequencies, one higher and the other lower than the natural frequency of the structure. The results demonstrate that, independent of the TMD damping and tuning frequency ratios, the frequency of streamwise vibrations matches that of the transverse vibrations in the synchronization region, and the cylinder traces elliptic trajectories. A mathematical model is proposed to gain insight into the frequency response of the structure and fluid-structure interactions. The model shows that, for low TMD damping ratios, the frequency response of the structure equipped with the TMD is characterized by two fundamental frequencies; whereas, for relatively high TMD damping ratios, the frequency response of the structure is characterized by a single frequency, i.e., the natural frequency. In both cases, the fluid forcing within the synchronization region is linked to the fundamental frequency/frequencies of the structure. Thus, the classical definition of synchronization applies to multiple DOF structures undergoing vortex-induced vibrations.

Maxwell-Voigt and Voigt Models for Vibration Isolation: Influence of Fractional Damping and Time Delay

2018 ◽  
Author(s):  
Sudhir Kaul
Keyword(s):  
Time Delay ◽  
Frequency Response ◽  
Fractional Order ◽  
Vibration Isolation ◽  
Damping Ratio ◽  
Maximum Amplitude ◽  
Damping Force ◽  
Fractional Damping ◽  
Integer Order ◽  
Voigt Model

This paper presents results from a follow-up study of fractional damping and time delay. Fractional damping has been used in the literature to demonstrate certain advantages over integer-order damping in many applications involving viscoelastic characteristics. It is observed that fractional damping can be used to influence stability boundaries, natural frequencies and vibration amplitudes, thus providing modeling flexibility in predicting the response of an isolated system during preliminary design. Additionally, time delay or lag is known to be inherent in a damped system, therefore a direct representation of time delay in modeling the damping force is expected to enhance model fidelity. This paper investigates the use of Voigt and Maxwell-Voigt models that incorporate fractional damping and time delay. In this paper, fractional damping has been particularly introduced to investigate possible improvements in the frequency response. Results indicate that fractional damping can be used to significantly enhance the capability of the Voigt model. The influence of the fractional order is found to be analogous to the damping ratio in an integer-order model. Fractional order is seen to exhibit a somewhat limited influence on the Maxwell-Voigt model. However, attributes such as the peak frequency and maximum amplitude are seen to be directly influenced by the fractional order. Although time delay is seen to exhibit an influence on the frequency response, it needs to be limited within useful bounds. Overall, it is observed that fractional order and time delay can be used to improve the accuracy of the Voigt and Maxwell-Voigt models. These enhanced models can be used for the design and development of elastomeric isolators and vibration isolation systems.

Identification of a Frequency Response Model of Joint Rotation

1990 ◽  
Vol 112 (1) ◽  
pp. 1-8 ◽  
Author(s):  
J. D. Becker ◽  
C. D. Mote
Keyword(s):  
Transfer Function ◽  
Natural Frequency ◽  
Isometric Contraction ◽  
Damping Ratio ◽  
Isometric Contractions ◽  
Response Model ◽  
Function Model ◽  
Joint Rotation ◽  
Dorsal Interossei ◽  
Stiffness And Damping

A second order, linear oscillator transfer function model is fit to the measured transfer function relating the abduction-adduction rotation of the first finger to the applied moment. Nearly constant isometric contractions of the first palmar and dorsal interossei are maintained by the subjects during the measurements. The stiffness and damping components of the identified models increase significantly with increasing isometric contraction when compared to those recorded under relaxed contraction. Muscle fatigue causes the natural frequency, damping ratio and stiffness of the joint rotation to decrease under full isometric contraction, and it causes the natural frequency and stiffness to increase when the muscles are relaxed.

Direct generation of floor design spectra (FDS) from uniform hazard spectra (UHS) — Part II: extension and application of the method

2020 ◽  
Vol 47 (12) ◽  
pp. 1387-1400 ◽  
Author(s):  
Amin Asgarian ◽  
Ghyslaine McClure
Keyword(s):  
Reinforced Concrete ◽  
Dynamic Analysis ◽  
Damping Ratio ◽  
Shear Walls ◽  
Response Spectra ◽  
Companion Paper ◽  
Uniform Hazard Spectra ◽  
General Applicability ◽  
Design Spectra ◽  
Floor Acceleration

This paper extends the methodology presented in the companion paper to study the effects of non-structural components’ (NSCs) damping ratio and their location in the building on the pseudo-acceleration floor response spectra (PA-FRS) of reinforced concrete buildings, and propose equations to derive floor acceleration design spectra (FDS) directly from the uniform hazard design spectra (UHS) for Montréal, Canada. The buildings used in the study are 27 existing reinforced concrete structures with braced frames and shear walls as their lateral load resisting systems: 12 are low-rise (up to 3 stories above ground), 10 are medium-rise (4 to 7 stories), and 5 are high-rise (10 to 18 stories). Based on statistical and regression analysis of floor acceleration spectra generated from linear dynamic analysis of coupled building–NSC systems, two sets of modification factors are proposed to account for floor elevation and NSC damping, applicable to the experimentally-derived FDS for roof level and 5% NSC damping. Modification factor equations could be derived only for the low-rise and medium-rise building categories, as insufficient correlation in trends could be obtained for high-rises given their low number. The approach is illustrated in detail for two typical buildings of the database, one low-rise (Building #4) and one medium-rise (Building #18), where the proposed FDS/UHS results show agreement with those obtained from detailed dynamic analysis. The work is presented in the context of a more general methodology to show its potential general applicability to other building types and locations.

scholarly journals Study On The Vibration Amplitudes Of Reinforced Concrete Bridge Piers Using ABAQUS Software

2021 ◽  
Vol 28 (2) ◽  
pp. 37-45
Author(s):  
Mais Ghassoun ◽  
Ali Algharrash ◽  
Reem Alsehnawi
Keyword(s):  
Dynamic Analysis ◽  
Natural Frequency ◽  
Dynamic Characteristics ◽  
Vibration Amplitude ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Response Amplitude ◽  
Experimental Results ◽  
Important Indicator ◽  
Design Values

The Dynamic characteristics such as damping ratio and natural frequency are an important indicator for predicting the dynamic behavior of bridges, but it is customary during the design that the designer assess the dynamic properties of the dynamic analysis because it is very difficult to determine the damping of the origin before construction and damping is taken as a predetermined constant value independent of the response amplitude and frequency of the structure. In the dynamic analysis of constructions design some experimental research has been concerned with the determination of dynamic structural properties and their relationship with the response amplitude experimentally, but the changes in dynamic properties with vibration amplitude has never been taken During dynamic analysis, further analytical treatments and computer modeling were required to study different cases based on the experimental results available by simulating them with a computer model. Dynamic characteristics are very essential to accurately determine the dynamic response, and it is necessary to study the effect of changes of the actual dynamic characteristics of bridges, which were determined by measuring their vibration in the results of dynamic analysis and comparing them with results that do not take into account the changes of dynamic properties and with laboratory results in order to assess the role of. Dynamic analysis inputs in simulating vibrations by monitoring their responses. As a result, it was found that the dynamic properties are independent of the shape of the external exactions. Also, it was concluded that relationships express the change of dynamic properties in terms of vibration amplitudes. And Similar reliance of the dynamic characteristics to the vibration amplitude is confirmed for the pier model, where the increase of the amplitude of the acceleration is accompanied by a decrease in the natural frequency, and an increase in the damping ratio is obvious. Before choosing design values when considering the dynamic characteristics of a structure, we need to give unique concentration to the predictable vibration amplitudes. Dynamic characteristics changes during dynamic analysis should be considered to produce analytical results that simulate experimental results and are closer to reality.

Frequency response of human soleus muscle

1976 ◽  
Vol 39 (4) ◽  
pp. 788-793 ◽  
Author(s):  
P. Bawa ◽  
R. B. Stein
Keyword(s):  
Frequency Response ◽  
Natural Frequency ◽  
Soleus Muscle ◽  
Damping Ratio ◽  
Low Frequency ◽  
Second Order ◽  
Order System ◽  
Pass Filter ◽  
Stimulus Pulse ◽  
Low Pass Filter

1. The properties of human soleus muscle were studied by systems analysis. Single stimulus pulses and random stimulus pulse trains were applied to a branch of the nerve to soleus muscle and the resultant tension fluctuations were recorded. 2. The frequency-response function between stimulus pulses and tension conforms to that of a second-order, low-pass filter. The parameters of the second-order system, low frequency gain, natural frequency, and damping ratio, varied systematically with the angle of the ankle. As the ankle was flexed (the length of the muscle was increased), the low frequency gain increased, the natural frequency decreased, and the damping ratio was unaffected or increased slightly. 3. These results are discussed in relation to the twitch responses of human soleus muscles and the responses previously observed in cat muscles.

Determination of frequency response from step response: application to fluid-filled catheters

1979 ◽  
Vol 236 (2) ◽  
pp. H376-H378 ◽  
Author(s):  
S. A. Glantz ◽  
J. V. Tyberg
Keyword(s):  
Decay Rate ◽  
Frequency Response ◽  
Natural Frequency ◽  
Damping Ratio ◽  
Step Change ◽  
Step Response ◽  
Undamped Natural Frequency

The performance of a fluid-filled catheter can be described by reporting its undamped natural frequency and damping ratio. These parameters can be measured by subjecting the catheter to sinusoidally varying pressures at a wide variety of frequencies to obtain the frequency response. They can also be computed from the response to a step change in pressure, which is often easier to produce. This paper derives the required equations and includes a graph which permits one to look up the undamped natural frequency after measuring the period and decay rate of the oscillation following a step change in pressure.

Study of a Hybrid Vibration Isolator and Its Properties

2005 ◽  
Author(s):  
Shi-Jian Zhu ◽  
Xian-Jun Wu
Keyword(s):  
Transfer Function ◽  
Natural Frequency ◽  
High Frequency ◽  
Damping Ratio ◽  
Structural Vibration ◽  
Good Effect ◽  
High Frequency Range ◽  
Frequency Range ◽  
Isolation System ◽  
Passive Isolation

In order to isolate the structural vibration in high frequency range effectively, low damping ratio of the isolator is preferred in the high frequency range. While in order to constrain the peak response value near the natural frequency, high damping ratio is preferred. Damping ratio of a passive isolation system is constant with respect to frequency. It cannot fulfill such a conflict request. A novel hybrid isolator, which consists of a passive one and a force actuator, was brought out in this paper to achieve a varying damping ratio with respect to frequency. The force actuator detects the deformation of the isolator and generates actuating force according to a designed transfer function. The transfer function was designed to have the property of increasing the damping near the natural frequency of the suspension system and decreasing the damping ratio in the high frequency range. Two application examples were given and good effect was found.

Exact Evaluation of Natural Frequency and Damping Ratio from a Frequency Response Curve

2000 ◽  
Vol 123 (3) ◽  
pp. 403-405 ◽  
Author(s):  
M. V. Drexel ◽  
J. H. Ginsberg
Keyword(s):  
Frequency Response ◽  
Natural Frequency ◽  
Damping Ratio ◽  
Fundamental Property ◽  
Response Curves ◽  
Single Degree Of Freedom ◽  
Analysis Techniques ◽  
Modal Damping ◽  
Exact Evaluation ◽  
Simple Characteristic

Several experimental modal analysis techniques fit resonance peaks to the response curves of a single degree of freedom system in order to identify the natural frequencies and modal damping ratios. The present study identifies a fundamental property of frequency response curves that allows the natural frequency to be identified from a simple characteristic of the curve, independently of the damping ratio. After the natural frequency has been determined, the damping ratio can be computed directly. The fundamental property holds for all values of damping, which eliminates the need to approximate either the natural frequency or damping ratio.

Dynamic Analysis and Optimization of WEDM Based on AWE and LMS

2015 ◽  
Vol 741 ◽  
pp. 772-778
Author(s):  
Hong Xu ◽  
Yi Chao Ding ◽  
Chui Min Luo ◽  
Wen Yong Guan
Keyword(s):  
Machine Tool ◽  
Dynamic Analysis ◽  
Natural Frequency ◽  
Electrical Discharge Machine ◽  
Dynamic Parameter ◽  
Element Analysis ◽  
Operation Process ◽  
Joint Surfaces ◽  
Discharge Machine ◽  
Stiffness And Damping

In the operation process, the Wire Electrical Discharge Machine (WEDM) has certain imperfections such as vibration and the descent of machine precision which vibration produces. This paper studies the dynamic parameter of the machine tool and optimizes the natural frequency and vibration. Taking the DK7725 taper machine tool as an example, the paper establishes a 3Dmodel with Pro-Engineer 5.0.According to the Masataks Yoshimura method, the authors could ascertain the stiffness and damping of joint surfaces among machine main parts and ascertain the equivalent dynamic model. In order to have a modal analysis about the machine tool structure, the virtual dynamic analysis module of ANSYS Workbench Environment (AWE) is used. Through the study of dynamic parameter, the authors optimize and improve the natural frequency and vibration of machine tools, compared with the finite element analysis results and the no-optimization data. And the final results show that the change rates of each order natural frequencies optimized ranges from 0% to18.9%, and the whole mechine’s optimization achieves satisfied effect.

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