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

2005 ◽  
Vol 127 (1) ◽  
pp. 93-99 ◽  
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.

H∞ control for a semi-active scissors linkage seat suspension with magnetorheological damper

2018 ◽  
Vol 30 (5) ◽  
pp. 708-721 ◽  
Author(s):  
Xiu-Mei Du ◽  
Miao Yu ◽  
Jie Fu ◽  
You-Xiang Peng ◽  
Hui-Feng Shi ◽  
...  
Keyword(s):  
State Feedback ◽  
Low Frequency ◽  
High Amplitude ◽  
Magnetorheological Damper ◽  
Seat Suspension ◽  
Damping Characteristics ◽  
The Neural Network ◽  
Inverse Models ◽  
Stiffness And Damping ◽  
Uncontrolled System

In this article, a robust state-feedback H∞ control for semi-active scissors linkage seat suspension with magnetorheological damper is investigated to reduce low-frequency and high-amplitude vibration, leading to health disorders in drivers or passengers. First, the stiffness and damping characteristics of the semi-active scissors linkage seat suspension are analyzed and a simplified model of the semi-active scissors linkage seat suspension is introduced. Then, the forward and inverse models of magnetorheological damper are described by the neural network method. Furthermore, the robust state-feedback H∞ control is established by considering the system uncertainties. The proposed approach is finally validated by experiment on a test rig under different sinusoidal excitations and load masses. Experimental results show that the human vibration is reduced up to 47.66% compared with the uncontrolled system.

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

2014 ◽  
Vol 229 (10) ◽  
pp. 1830-1838 ◽  
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.

Design Optimization of Aircraft Engine-Mount Systems

1993 ◽  
Author(s):  
Hashem Ashrafiuon
Keyword(s):  
Design Optimization ◽  
Vibration Isolation ◽  
Optimization Problems ◽  
Three Dimensional ◽  
Low Frequency ◽  
Aircraft Engine ◽  
Variable Metric ◽  
Design Variables ◽  
Engine Mount ◽  
Optimization Search

Abstract Design optimization of aircraft engine-mount systems for vibration isolation is presented. The engine is modeled as a rigid body connected to a flexible base representing the nacelle. The base is modeled with mass and stiffness matrices and structural damping using finite element modeling. The mounts are modeled as three-dimensional springs with hysteresis damping. The objective is to select the stiffness coefficients and orientation angles of the individual mounts to minimize the transmitted forces from the engine to the base. Meanwhile, the mounts have to be stiff enough not allowing engine deflection to exceed its limits under static and low frequency loadings. It is shown that with an optimal system the transmitted forces may be reduced significantly particularly when mount orientation angles are also treated as design variables. The optimization problems are solved using a Constraint Variable Metric approach. The closed form derivatives of the engine vibrational amplitudes with respect to design variables are derived in order to achieve a more effective optimization search technique.

Advancements in the Structural Stiffness and Damping of a Large Compliant Foil Journal Bearing: An Experimental Study

2004 ◽  
Vol 129 (1) ◽  
pp. 154-161 ◽  
Author(s):  
Mohsen Salehi ◽  
Hooshang Heshmat ◽  
James F. Walton
Keyword(s):  
Journal Bearing ◽  
Dynamic Stiffness ◽  
Operating Conditions ◽  
Test Facility ◽  
Squeeze Film ◽  
Structural Stiffness ◽  
Low Frequencies ◽  
Equivalent Viscous Damping ◽  
Damping Characteristics ◽  
Stiffness And Damping

This paper presents the results of an experimental investigation into the dynamic structural stiffness and damping characteristics of a 21.6‐cm(8.5in.)-diameter compliant surface foil journal bearing. The goal of this development was to achieve high levels of damping without the use of oil, as is used in squeeze film dampers, while maintaining a nearly constant dynamic stiffness over a range of frequencies and amplitudes of motion. In the experimental work described herein, a full compliant foil bearing was designed, fabricated, and tested. The test facility included a non-rotating journal located inside the bearing. The journal was connected to an electrodynamic shaker so that dynamic forces simulating expected operating conditions could be applied to the structurally compliant bump foil elements. Excitation test frequencies to a maximum of 400Hz at amplitudes of motion between 25.4 and 102μm were applied to the damper assembly. During testing, both compressive preload and unidirectional static loads of up to 1335 and 445N, respectively, were applied to the damper assembly. The experimental data from these tests were analyzed using both a single degree of freedom model and an energy method. These methods of data analysis are reviewed here and results are compared. Excellent agreement in results obtained from the two methods was achieved. Equivalent viscous damping coefficients as high as 1050N.s∕cm(600lbf.s∕in) were obtained at low frequencies. Dynamic stiffness was shown to be fairly constant with frequency.

Stiffness and Damping Characteristics of a Wide Parabolic Film Slider Bearing Operating with Ferrofluids

2014 ◽  
Vol 1052 ◽  
pp. 132-136
Author(s):  
Jaw Ren Lin
Keyword(s):  
Magnetic Fields ◽  
Dynamic Characteristics ◽  
Dynamic Stiffness ◽  
Slider Bearing ◽  
Inclined Plane ◽  
Damping Characteristics ◽  
Plane Film ◽  
Stiffness And Damping

This paper investigates the dynamic characteristics of parabolic film slider bearing operating with ferrofluids. Comparing with the slider bearing of an inclined plane film, the parabolic film slider bearing operating with ferrofluids in the presence of external magnetic fields provide higher better dynamic stiffness and damping performances.

Advancements in the Structural Stiffness and Damping of a Large Compliant Foil Journal Bearing: An Experimental Study

2004 ◽  
Author(s):  
Mohsen Salehi ◽  
Hooshang Heshmat ◽  
James F. Walton
Keyword(s):  
Journal Bearing ◽  
Dynamic Stiffness ◽  
Operating Conditions ◽  
Test Facility ◽  
Squeeze Film ◽  
Structural Stiffness ◽  
Low Frequencies ◽  
Equivalent Viscous Damping ◽  
Damping Characteristics ◽  
Stiffness And Damping

This paper presents the results of an experimental investigation into the dynamic structural stiffness and damping characteristics of a 21.6 cm (8.5inch) diameter compliant surface foil journal bearing. The goal of this development was to achieve high levels of damping without the use of oil, as is used in squeeze film dampers, while maintaining a nearly constant dynamic stiffness over a range of frequencies and amplitudes of motion. In the experimental work described herein, a full compliant foil bearing was designed, fabricated and tested. The test facility included a non-rotating journal located inside the bearing. The journal was connected to an electrodynamic shaker so that dynamic forces simulating expected operating conditions could be applied to the structurally compliant bump foil elements. Excitation test frequencies to a maximum of 400 Hz at amplitudes of motion between 25.4μm to 102μm were applied to the damper assembly. During testing, both compressive preload and unidirectional static loads of up to 1335N and 445N, respectively, were applied to the damper assembly. The experimental data from these tests were analyzed using both a single degree of freedom model and an energy method. These methods of data analysis are reviewed here and results are compared. Excellent agreement in results obtained from the two methods was achieved. Equivalent viscous damping coefficients as high as 1050 N.s/cm (600 lbf.s/in) were obtained at low frequencies. Dynamic stiffness was shown to be fairly constant with frequency.

A Systematic Approach for Optimal Mounting System Design of Truck Body

2005 ◽  
Author(s):  
Dongying Jiang ◽  
Yushun Cui ◽  
Zheng-Dong Ma ◽  
Rod Hadi
Keyword(s):  
System Design ◽  
Design Problem ◽  
Systematic Approach ◽  
Dynamic Stiffness ◽  
Optimal Path ◽  
Optimization Procedure ◽  
The Body ◽  
Design Variables ◽  
Engine Mount ◽  
Stiffness And Damping

Body mount system is utilized for isolating dynamic load and vibration into the cab from the rest of vehicle system. The behavior of the mount system not only depends on the performance of individual mounts but also on the complete system configuration. A systematic approach is proposed for optimal design of the truck body mount system. Design variables include the mount locations and mechanical properties of each individual mount. First, an advanced component mode-based substructuring method is utilized for developing reduced-order models of the cab body and the other related subsystems, such as the chassis frame, from the original detailed finite element models. An optimization procedure is then developed, which can be used to determine the geometric distribution of the mounts and their mechanical characteristics (e.g., dynamic stiffness and damping) for minimizing vibration amplitudes at the given locations in the body structure over a frequency range of interest. To determine the optimal mount distribution, a path variable is introduced at the interface of cab and frame, which allows each individual mount moving along the chassis frame in the permitted range. The optimal mount location design problem is thus transformed to an equivalent problem that determines the optimal path variables of each mount. MATLAB codes are developed for the mount system design problem. An example mount system design is given to illustrate the effectiveness and efficiency of the proposed approach, in which the mount stiffness and the mount locations are optimized simultaneously. The developed optimization tool can be extended for optimizing other general mounting systems, such as an engine mount system.

Dynamic Characteristics Optimization of Joint Interface of Machine Tool Based on Porous Oily Materials

2014 ◽  
Vol 709 ◽  
pp. 63-67
Author(s):  
Jian Feng Ma ◽  
Qiang Li ◽  
Ji Kun Feng ◽  
Liang Sheng Wu
Keyword(s):  
Porous Material ◽  
Machine Tool ◽  
Dynamic Characteristics ◽  
Machine Tools ◽  
Unit Area ◽  
Test System ◽  
Joint Interface ◽  
Characteristic Parameters ◽  
Damping Characteristics ◽  
Stiffness And Damping

The joint interface plays a significant role in machine tools and other machineries. A novel type of joint which consists of oily porous material was proposed in the paper. A test system for identifying the unit area dynamic characteristic parameters of Fe-based joint interfaces were represented. The stiffness and damping parameters were compare to the conversional structures. The result showed that the joint which contains an oil film interlayer formed by porous and steel was superior to the joint with non-media formed by steel in stiffness and damping characteristics. In the case of the same preload, the former’s stiffness is increased by about 50 %, and the damping is increased about five to six times.

Dynamic Characteristics of Aerostatic Thrust Bearings with Porous Inserts

1980 ◽  
Vol 22 (2) ◽  
pp. 55-58 ◽  
Author(s):  
B. C. Majumdar
Keyword(s):  
Perturbation Method ◽  
Dynamic Characteristics ◽  
Dynamic Behaviour ◽  
Thrust Bearing ◽  
Thrust Bearings ◽  
First Order ◽  
Design Variables ◽  
Stiffness And Damping ◽  
Film Stiffness ◽  
First Order Perturbation

A first-order perturbation method is adopted to find the dynamic behaviour of an aerostatic circular thrust bearing having a central porous insert as a restrictor. The linearized gas film stiffness and damping are derived and used to study their behaviour with other design variables.

Dynamic Characteristics Research of Magneto-Rheological Fluid Engine Mount

2015 ◽  
Vol 752-753 ◽  
pp. 913-917
Author(s):  
Gong Yu Pan ◽  
Qian Qian Wang ◽  
Xin Yang
Keyword(s):  
Dynamic Characteristics ◽  
Vibration Isolation ◽  
Dynamic Stiffness ◽  
Simulation Software ◽  
New Type ◽  
Engine Mount ◽  
Magneto Rheological ◽  
Stiffness And Damping ◽  
Vibration Isolation Performance ◽  
Isolation Performance

In order to improve the vibration isolation performance of engine mount, a new type of magneto-rheological semi-active mount with multiple inertia tracks is designed based on the existing magneto-rheological semi-active mount . The mechanical model is established according to the mount. The expression of the dynamic stiffness and damping lag angle is deduced, then the dynamic characteristics is simulated in the simulation software. At the same time, verify this model correct by the experiments.

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