Dynamic characteristics of a quasi-zero stiffness vibration isolator with nonlinear stiffness and damping

This paper presents an analytical and experimental analysis of the characteristics of a squeeze-type magnetorheological (MR) mount which can be used for various vibration isolation areas. The concept of the squeeze-type mount and details of the design of a squeeze-type MR mount are discussed. These are followed by a detailed description of the test set-up for evaluating the dynamic behaviour of the mount. A series of tests was conducted on the prototype mount built for this study, in order to characterize the changes occurring as a result of changing electrical current to the mount. The results of this study show that increasing electrical current to the mount, which increases the yield stress of the MR fluid, will result in an increase in both stiffness and damping of the mount. The results also show that the mount hysteresis increases with increase in current to the MR fluid, causing changes in stiffness and damping at different input frequencies.

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Design and structural performance measurements of a novel multi-cantilever foil bearing

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406214547529 ◽

2014 ◽

Vol 229 (10) ◽

pp. 1830-1838 ◽

Cited By ~ 8

Author(s):

Kai Feng ◽

Xueyuan Zhao ◽

Zhiyang Guo

Keyword(s):

Dynamic Characteristics ◽

Dynamic Load ◽

Dynamic Stiffness ◽

Excitation Frequency ◽

Viscous Damping ◽

Equivalent Viscous Damping ◽

Foil Bearing ◽

Load Tests ◽

Stiffness And Damping ◽

Motion Amplitude

With increasing need for high-speed, high-temperature, and oil-free turbomachinery, gas foil bearings (GFBs) have been considered to be the best substitutes for traditional oil-lubricated bearings. A multi-cantilever foil bearing (MCFB), a novel GFB with multi-cantilever foil strips serving as the compliant underlying structure, was designed, fabricated, and tested. A series of static and dynamic load tests were conducted to measure the structural stiffness and equivalent viscous damping of the prototype MCFB. Experiments of static load versus deflection showed that the proposed bearing has a large mechanical energy dissipation capability and a pronounced nonlinear static stiffness that can prevents overly large motion amplitude of journal. Dynamic load tests evaluated the influence of motion amplitude, loading orientation and misalignment on the dynamic stiffness and equivalent viscous damping with respect to excitation frequency. The test results demonstrated that the dynamic stiffness and damping are strongly dependent on the excitation frequency. Three motion amplitudes were applied to the bearing housing to investigate the effects of motion amplitude on the dynamic characteristics. It is noted that the bearing dynamic stiffness and damping decreases with incrementally increasing motion amplitudes. A high level of misalignment can lead to larger static and dynamic bearing stiffness as well as to larger equivalent viscous damping. With dynamic loads applied to two orientations in the bearing midplane separately, the dynamic stiffness increases rapidly and the equivalent viscous damping declines slightly. These results indicate that the loading orientation is a non-negligible factor on the dynamic characteristics of MCFBs.

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A Variable Viscosity Approach for the Analysis of Steady State and Dynamic Characteristics of Two-Lobe Journal Bearing With TiO2 Based Nanolubricant

Volume 2: Structures and Dynamics; Renewable Energy (Solar, Wind); Inlets and Exhausts; Emerging Technologies (Hybrid Electric Propulsion, UAV, ...); GT Operation and Maintenance; Materials and Manufacturing (Including Coatings, Composites, CMCs, Additive Manufacturing); Analytics and Digital Solutions for Gas Turbines/Rotating Machinery ◽

10.1115/gtindia2017-4646 ◽

2017 ◽

Author(s):

Ashutosh Kumar ◽

Sashindra Kumar Kakoty

Keyword(s):

Steady State ◽

Dynamic Characteristics ◽

Journal Bearing ◽

Volume Fraction ◽

Variable Viscosity ◽

Flow Coefficient ◽

Viscosity Model ◽

Nano Lubricant ◽

The Stability ◽

Stiffness And Damping

Steady-state and dynamic characteristics of two-lobe journal bearing, operating on TiO2 based Nano-lubricant has been obtained. The effective viscosity is obtained by using Krieger-Dougherty viscosity model for a given volume fraction of nanoparticle in the base fluid. Various bearing performance characteristics are then obtained by solving modified Reynolds equation for variable viscosity model and couple stress model. The stiffness and damping coefficients are also determined for various values of the volume fraction of the nanoparticle in the nanofluid. Results reveal that load carrying capacity and flow coefficient increase whereas friction variable decreases without affecting the stability condition of two-lobe journal bearing operating on TiO2 based nanolubricant. On the other hand attitude angle and dynamic coefficients remains constant for all the values of volume fraction of nanoparticle.

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Investigation of nonlinear landing gear behavior and dynamic responses on high performance aircraft

Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering ◽

10.1177/0954410019854628 ◽

2019 ◽

Vol 233 (15) ◽

pp. 5674-5688

Author(s):

PS Suresh ◽

Niranjan K Sura ◽

K Shankar

Keyword(s):

Dynamic Response ◽

Nonlinear Dynamic ◽

Landing Gear ◽

Flight Mechanics ◽

Dynamic Responses ◽

Nonlinear Stiffness ◽

Response Model ◽

Nonlinear Dynamic Response ◽

Vertical Descent ◽

Stiffness And Damping

The dynamic responses simulation of aircraft as rigid body considering heave, pitch, and roll motions, coupled onto a tricycle landing gear arrangement is presented. Equation of motion for each landing gear consists of un-sprung mass vertical and longitudinal motions considering strut nonlinear stiffness and damping combined with strut bending flexibility. Initially, the nonlinear dynamic response model is subjected to an input of riding over staggered bump and the responses are compared with linear landing gear model. It is observed that aircraft dynamics and important landing gear events such as vertical, spin-up and spring-back are truly represented with nonlinear stiffness and damping model considering strut bending flexibility. Later, landing response analysis is performed, with the input from nonlinear flight mechanics model for several vertical descent rate cases. The aircraft and landing gear dynamic responses such as displacement, velocity, acceleration, and reaction forces are obtained. The vertical and longitudinal drag forces from the nonlinear dynamic response model is compared with “Book-case method” outlined in landing gear design technical specifications. From the reaction force ratio calculation, it is shown that for lower vertical descent rate case the predicted loads are lesser using nonlinear dynamic response model. The same model for higher vertical descent rate cases predicts higher ratios on vertical reaction for main landing gear and longitudinal reaction for nose landing gear, respectively. The scope for increase in fatigue life for low vertical descent rate landing covering major design spectrum and the concern for static strength and structural integrity consideration for higher vertical descent rate cases are discussed in the context of event monitoring on aircraft in services.

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Dynamic Characteristics Analysis of Flexible Mechanism Using Three Parameters Damping Model

Volume 2 ◽

10.1115/esda2004-58045 ◽

2004 ◽

Author(s):

Hongzhao Liu ◽

Baixi Liu ◽

Daning Yuan

Keyword(s):

Differential Equations ◽

Dynamic Characteristics ◽

Virtual Work ◽

Dynamic Equations ◽

Linkage Mechanism ◽

Varying Coefficients ◽

Characteristics Analysis ◽

Time Varying Coefficients ◽

Stiffness And Damping ◽

Damping Model

In this paper, a practical structural damping model for the dynamic analysis of damping alloy is presented. The differential equations of the beam element with three parameters representing stiffness and damping characteristics are deduced through the three parameters constitution and the virtual work principle. By means of the Kineto-Elastodynamic theory, the established element dynamic equations are assembled into the system dynamic equations of flexible linkage mechanism. In order to solve the high order differential equations with time-varying coefficients, a closed form numerical algorithm is constructed. Lastly, an example of a four-bar elastic linkage mechanism is given to show the effectiveness of the proposed method in studying dynamic characteristics of structure containing damping alloy components.

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Numerical Modeling and Analysis of Nonlinear Dynamic Response for a Bolted Joint Beam Considering Interface Frictional Contact

Volume 4A: Dynamics, Vibration, and Control ◽

10.1115/imece2018-86743 ◽

2018 ◽

Author(s):

Dongwu Li ◽

Chao Xu ◽

Dong Wang ◽

Lihua Wen

Keyword(s):

Constitutive Model ◽

Dynamic Response ◽

Numerical Results ◽

Experimental Results ◽

Bolted Joints ◽

Interface Element ◽

Nonlinear Stiffness ◽

Friction Contact ◽

Structural Dynamic ◽

Stiffness And Damping

For an assembled structure with many bolted joints, predicting its dynamic response with high fidelity is always a difficult problem, because of the nonlinearity introduced by friction contact between jointed interfaces. The friction contact results in nonlinear stiffness and damping to a structure. To realize predictive simulation in structural dynamic design, these nonlinear behaviors must be carefully considered. In this paper, the dynamics of a multi-bolt jointed beam is calculated. A modified IWAN constitutive model, which can consider both tangential micro/macro slip and nonzero residual stiffness at macroslip phase, is developed to model nonlinear contact behaviors due to joint interfaces. A whole interface element integrating the proposed constitutive model is developed. The element is used to model the nonlinear stiffness and damping caused by bolted joints. The interface element is placed between the two contact interfaces. The other part of the beam is modeled by linear beam elements. A Matlab code is developed to realize the proposed nonlinear finite element dynamic analysis method. A hammer impact experiment for the bolt-jointed beam is conducted under different excitation force levels. The calculated nonlinear numerical results are compared with experimental results. It is shown that the effect of joint nonlinearity on structural dynamics can be observed from the response predicted by the proposed method. The numerical results agree well with the experimental results. This work validates the necessary of using nonlinear joint model for dynamic simulation of jointed structures.

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An Efficient Technique for Design of Hydraulic Engine Mount via Design Variable-Embedded Damping Modeling

Journal of Vibration and Acoustics ◽

10.1115/1.1855930 ◽

2005 ◽

Vol 127 (1) ◽

pp. 93-99 ◽

Cited By ~ 9

Author(s):

Jun-Hwa Lee ◽

Kwang-Joon Kim

Keyword(s):

Dynamic Characteristics ◽

Low Frequency ◽

High Amplitude ◽

Nonlinear Damping ◽

Efficient Design ◽

Equivalent Viscous Damping ◽

Damping Characteristics ◽

Design Variables ◽

Engine Mount ◽

Stiffness And Damping

For an efficient design of hydraulic mounts, it is most important to have a good mathematical model available, which must be simple yet capable of representing dynamic characteristics of the hydraulic mounts accurately. Under high amplitude excitations in the low-frequency range, the hydraulic mounts show strongly frequency-dependent stiffness and damping characteristics, which are related with so-called inertia track dynamics. Since nonlinear damping models based on fluid mechanics are typically used to predict the dynamic characteristics of the hydraulic mounts, relations between various design variables, such as geometry of the inertia track, and resultant stiffness and damping characteristics are understood only by tedious numerical computations. In this paper, the use of an equivalent viscous damping model—derived from a nonlinear model and represented in terms of design variables in an explicit manner—is proposed and, based on the equivalent linear model, are presented simple as well as very useful formulas for an efficient design of the hydraulic mounts.

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Dynamic Characteristics of Spiral-Grooved Opposed-Hemisphere Gas Bearings

Journal of Tribology ◽

10.1115/1.4034423 ◽

2016 ◽

Vol 139 (3) ◽

Cited By ~ 4

Author(s):

Guangwei Yang ◽

Jianjun Du ◽

Weiping Ge ◽

Tun Liu ◽

Xiaowei Yang

Keyword(s):

Dynamic Characteristics ◽

Degrees Of Freedom ◽

Dynamic Stiffness ◽

Translational Motion ◽

Coupling Coefficients ◽

Dynamic Coefficients ◽

Large Eccentricity ◽

The Stability ◽

Stiffness And Damping ◽

Gas Bearing

The traditional eight-coefficient bearing model only considers the translational motion of the bearings and neglects the tilting motion and coupling effects between them. In this paper, the dynamic characteristics of the spiral-grooved opposed-hemisphere gas bearing considering five degrees-of-freedom are studied, and 50 dynamic coefficients including the translational, tilting, and coupling components are completely calculated. The Reynolds equations and their perturbed equations are solved by the finite element method to obtain the dynamic stiffness and damping coefficients. The effects of the tilting motion on the dynamic coefficients and response are analyzed, respectively. The results show that the coupling coefficients between the translational and tilting motions, which have been neglected in most previous studies, are significant at large eccentricity ratio. But these coupling coefficients have little effect on the dynamic response. On the other hand, the influences of the tilting motion on the synchronous response and natural frequency are remarkable and will decrease the stability of the rotor bearing system.

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Study on Nonlinear Damping Properties of Hydro-Pneumatic Suspension System for XP302-Pneumatic Tyred Roller

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.945-949.987 ◽

2014 ◽

Vol 945-949 ◽

pp. 987-991

Author(s):

Bang Sheng Xing ◽

Ning Ning Wang ◽

Le Xu

Keyword(s):

Dynamic Performance ◽

Nonlinear Damping ◽

Suspension System ◽

Nonlinear Stiffness ◽

Damping Properties ◽

Vehicle Dynamic ◽

Nonlinear Mathematical Model ◽

Computer Simulation Program ◽

Pneumatic Suspension ◽

Stiffness And Damping

The nonlinear stiffness and damping properties of the hydro-pneumatic suspension system are introduced, and the nonlinear mathematical model of it is established. Using MATLAB 2009b to establish the computer simulation program and draw out the nonlinear stiffness curve and damping properties curve of the hydro-pneumatic suspension system. Then, researching the influences of related parameters' changes on the nonlinear stiffness and damping properties of the hydro-pneumatic suspension system. The simulation of vehicle dynamic performance research's foundation is provided.

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