scholarly journals Shock Performance of Different Semiactive Damping Strategies

2010 ◽  
Vol 8 (02) ◽  
Author(s):  
D. F. Ledezma-Ramirez ◽  
N. Ferguson ◽  
M. Brennan
Keyword(s):  
Harmonic Excitation ◽  
Degree Of Freedom ◽  
Harmonic Vibration ◽  
Passive Stiffness ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Variable Damping ◽  
Stiffness And Damping ◽  
Shock Pulses

The problem of shock generated vibration is presented and analyzed. The fundamental background is explained based on the analysis of a single degree-of-freedom model with passive stiffness and damping. The advantages and limitations of such a shock mount are discussed. Afterwards, different semi-active strategies involving variable damping are presented. These strategies have been used for harmonic excitation but it is not clear how they will perform during a shock. This paper analyzes the different variable damping schemes already used for harmonic vibration in order to find any potential advantages or issues for theoretical shock pulses.

A Probabilistic Analysis of Single-Degree-of-Freedom Blade Vibration

1993 ◽  
Author(s):  
Kenan Y. Sanliturk ◽  
Mehmet Imregun ◽  
David J. Ewins
Keyword(s):  
Natural Frequencies ◽  
Probabilistic Approach ◽  
Substantial Reduction ◽  
Forced Response ◽  
Degree Of Freedom ◽  
Cumulative Probability ◽  
Blade Vibration ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Stiffness And Damping

The effects of random stiffness and damping variations on damped natural frequencies and response levels of turbomachinery blades are investigated by employing probabilistic approach using a single-degree-of-freedom (SDOF) model. An important feature of this study is the determination of the cumulative probability distributions for damped natural frequencies and receptance frequency response functions without having to compute their probability density distributions since it is shown that those of stiffness and damping can be used directly. The advantage of this approach is not only in the simplicity of problem formulation but also in the substantial reduction of computational requirements. Furthermore, results suggest that both stiffness and damping properties should be considered as random parameters in statistical analyses of forced response.

Periodic Motions in a Single-Degree-of-Freedom System Under Both an Aerodynamic Force and a Harmonic Excitation

2019 ◽  
Author(s):  
Bo Yu ◽  
Albert C. J. Luo
Keyword(s):  
Numerical Simulations ◽  
Analytical Approach ◽  
Aerodynamic Force ◽  
Excitation Frequency ◽  
Harmonic Excitation ◽  
Degree Of Freedom ◽  
Periodic Motions ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Stable Period

Abstract In this paper, a semi-analytical approach was used to predict periodic motions in a single-degree-of-freedom system under both aerodynamic force and harmonic excitation. Using the implicit mappings, the predictions of period-1 motions varying with excitation frequency are obtained. Stability of the period-1 motions are discussed, and the corresponding eigenvalues of period-1 motions are presented. Finally, numerical simulations of stable period-1 motions are illustrated.

scholarly journals Optimization of Multiple Tuned Mass Damper (MTMD) Parameters for a Primary System Reduced to a Single Degree of Freedom (SDOF) Through the Modal Approach

2020 ◽  
Author(s):  
Piotr Wielgos ◽  
Robert Geryło
Keyword(s):  
Degrees Of Freedom ◽  
Research Work ◽  
System Optimization ◽  
Degree Of Freedom ◽  
Primary System ◽  
Single Degree Of Freedom ◽  
Modal Approach ◽  
Single Degree ◽  
Stiffness And Damping ◽  
The Impact

The research paper presents a new approach towards constructing motion equations for structures with attached MTMDs (multiple tuned mass dampers). A primary system, with MDOF (multiple dynamic degrees of freedom) was reduced to an equivalent system with a SDOF (single degree of freedom) through the modal approach, and equations from additional MTMDs were added to a thus-created system. Optimization based on H2 and H∞ for the transfer function associated with the generalized displacement of an SDOF system. The research work utilized GA (genetic algorithms) and SA (simulated annealing method) optimization algorithms to determine the stiffness and damping parameters for individual TMDs. The effect of damping and stiffness (MTMD tuning) distribution depending on the number of TMDs was also analyzed. The paper also reviews the impact of primary system mass change on the efficiency of optimized MTMDs, as well as confirms the results of other authors involving greater MTMD effectiveness relative to a single TMD.

Fast Simulation of a Single Degree-of-Freedom System Consisting of An Iwan Element Using the Method of Averaging

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Drithi Shetty ◽  
Matthew Allen
Keyword(s):  
Equations Of Motion ◽  
Element Model ◽  
Degree Of Freedom ◽  
Single Degree Of Freedom ◽  
Weakly Nonlinear ◽  
Single Degree ◽  
Integration Schemes ◽  
Current Implementation ◽  
Modal Model ◽  
Stiffness And Damping

Abstract While Iwan elements have been used to effectively model the stiffness and energy dissipation in bolted joints, integrating the equations of motion of these elements is fairly expensive since implicit schemes, such as Newmark’s methods, need to be used. This paper presents a method of simulating dynamic systems containing nonlinear Iwan elements that significantly reduce the computation cost by using closed-form expressions for stiffness and damping in the microslip regime and an averaging method for regions of time in which no external force is applied. The proposed algorithm is demonstrated on a single degree-of-freedom (SDOF) system to evaluate the range over which it retains accuracy and the improvement in performance it offers. Although the current implementation is limited to SDOF systems, it can be used to simulate the response of each mode in structures exhibiting weak nonlinearity that can be modeled using the modal Iwan approach. To verify this, the dynamic response of a finite element model of a beam assembly, integrated using the Newmark-β method, has been compared with its equivalent modal model integrated using the proposed algorithm. The results show that the algorithm accurately predicts the response in a fraction of the time taken by implicit integration schemes, so long as the modes remain uncoupled and weakly nonlinear.

Categorization of Dynamic Loading Into Force-Controlled Loading and Displacement-Controlled Loading

2018 ◽  
Author(s):  
Ichiro Tamura ◽  
Shinichi Matsuura ◽  
Ryuya Shimazu ◽  
Koji Kimura
Keyword(s):  
Dynamic Loading ◽  
Kinematic Hardening ◽  
Harmonic Excitation ◽  
Degree Of Freedom ◽  
Skeleton Curve ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Dynamic Loadings ◽  
Restoring Forces

To investigate the behavior of inelastic single-degree-of-freedom systems, the maximum restoring forces and maximum deformations of the systems due to a harmonic excitation are calculated and drawn as a diagram. These systems have restoring forces characterized by bilinear skeleton curve of the kinematic hardening type. The diagram shows two types of characteristics, and the dynamic loadings can be categorized into force-controlled loading and displacement-controlled loading.

Dynamic Analysis and Optimization of Tensioner in Automotive Serpentine Belt Drive Systems

2002 ◽  
Author(s):  
Mostafa Nouri ◽  
Jean W. Zu
Keyword(s):  
Optimum Design ◽  
Harmonic Excitation ◽  
Degree Of Freedom ◽  
System Component ◽  
Belt Drive ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Serpentine Belt ◽  
System Vibration ◽  
Drive Systems

A design methodology is developed to achieve optimum design of tensioner in serpentine belt drive systems. System component responses to a harmonic excitation from the crankshaft are obtained analytically by using a complete multi-degree of freedom model and also in explicit expressions using an equivalent single-degree of freedom model. Sequential quadratic programming and Kuhn-Tucker methods are applied to obtain the optimum design of the system modeled as multi-degree of freedom and single-degree of freedom respectively, with the objective of minimizing the undesired vibration of system components. It is shown that system vibration behavior improves substantially by optimizing the design of tensioner device.

scholarly journals EFFECT OF GYROSCOPE PARAMETERS ON GYROSCOPIC TREMOR SUPPRESSION IN A SINGLE DEGREE OF FREEDOM

2019 ◽  
Vol 19 (04) ◽  
pp. 1950024
Author(s):  
BRENDON C. ALLEN ◽  
STEVEN K. CHARLES
Keyword(s):  
Frequency Response ◽  
Wrist Joint ◽  
Systematic Investigation ◽  
Degree Of Freedom ◽  
Single Degree Of Freedom ◽  
Know How ◽  
Single Degree ◽  
Tremor Suppression ◽  
Stiffness And Damping ◽  
Input Torque

Although tremor is one of the most common movement disorders, there are few effective tremor-suppressing options available to patients. Gyrostabilization is a potential option, but we do not currently know how to optimize gyrostabilization for tremor suppression. To address this gap, we present a systematic investigation of how gyrostabilizer parameters affect tremor suppression in a single degree of freedom (DOF). A simple model with a single DOF at the wrist and a gyroscope mounted on the back of the hand was used to focus on the most basic effects. We simulated the frequency response of the system (hand + gyroscope) to a tremorogenic input torque at the wrist. Varying system parameters one at a time, we determined the effect of individual parameters on the system’s frequency response. To minimize the bandwidth without adding significant inertia, the inertia and spin speed of the flywheel should be as high as design constraints allow, whereas the distance from the wrist joint axis to the gyroscope and the precession stiffness and damping should be kept as low as possible. The results demonstrate the potential of gyroscopic tremor suppression and can serve as foundation for further investigations of gyroscopic tremor suppression in the upper limb.

Identification of Structural Parameters by Wavelet Transform of Acceleration Response

1999 ◽  
Author(s):  
Akira Sone ◽  
Ryutaro Segawa ◽  
Shizuo Yamamoto ◽  
Arata Masuda ◽  
Hiroaki Hata
Keyword(s):  
Wavelet Transform ◽  
Numerical Simulations ◽  
Structural Model ◽  
Structural Parameters ◽  
Degree Of Freedom ◽  
Acceleration Response ◽  
Single Degree Of Freedom ◽  
Displacement Response ◽  
Single Degree ◽  
Stiffness And Damping

Abstract The method to identify structural parameters of multi-degree of freedom structures by the wavelet transform of displacement response is previously proposed However, the vibration of structure is measured by the accelerometers. Therefore, if it is possible to identify structural parameters by the wavelet transform of only acceleration responses, it is very useful. In this paper, the method to identify structural parameters such as stiffness and damping by wavelet transform of acceleration responses is presented. To verify the applicability of the proposed method, numerical simulations using the single degree of freedom structure and the four-degree-of-freedom structure and the experiments using simple structural model are conducted. From both results, it has been clear that the proposed method can give the good estimation for the structural parameters.

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