Effects of Entrapped Gas within the Fluid on the Stiffness and Damping Characteristics of a Hydro-Pneumatic Suspension Strut

2017 ◽  
Vol 10 (1) ◽  
pp. 204-209 ◽  
Author(s):  
Yuming Yin ◽  
Subhash Rakheja ◽  
Jue Yang ◽  
P-E. Boileau
Keyword(s):  
Damping Characteristics ◽  
Pneumatic Suspension ◽  
Stiffness And Damping ◽  
Suspension Strut

PROPERTIES OF AN INTERCONNECTED HYDRO-PNEUMATIC SUSPENSION SYSTEM

1995 ◽  
Vol 19 (4) ◽  
pp. 383-396 ◽  
Author(s):  
P.J. Liu ◽  
S. Rakheja ◽  
A.K.W. Ahmed
Keyword(s):  
Dynamic Properties ◽  
The Body ◽  
Ride Quality ◽  
Quality Performance ◽  
Fundamental Properties ◽  
Damping Characteristics ◽  
Load Carrying ◽  
Body Roll ◽  
Pneumatic Suspension ◽  
Stiffness And Damping

The static and dynamic properties of a vehicle suspension comprising hydraulic struts interconnected in the roll plane are investigated. The fundamental properties of the interconnected suspension are investigated and compared to those of the unconnected suspensions with and without the anti-roll bar, in terms of load-carrying capacity, suspension rate, roll stiffness as well as damping characteristics. The anti-roll performance of the interconnected suspension is analyzed for excitations encountered during directional manoeuvres. The ride quality performance is evaluated for excitations occurring at tire-road interface. It is concluded that the interconnected hydro-pneumatic suspension with inherent enhanced roll stiffness and damping characteristics can significantly restrict the body roll motion to achieve improved roll stability of a vehicle.

Multidisciplinary Co-Simulation of All-Terrain Crane With the Hydro-Pneumatic Suspension and Multi-Bridges Steering System

2010 ◽  
Author(s):  
Gang Qin ◽  
Jinglai Wu ◽  
Yunqing Zhang ◽  
Liping Chen
Keyword(s):  
Control Strategy ◽  
Ride Comfort ◽  
Control Valve ◽  
Steering System ◽  
Damping Characteristics ◽  
Hydraulic Steering ◽  
Pneumatic Suspension ◽  
Stiffness And Damping ◽  
Multi Body ◽  
And Control

Hydro-pneumatic suspension and multi-bridges steering system, which can meet the demands of ride comfort and steering maneuverability of the crane by their excellent nonlinear stiffness and damping characteristics and innovative control technology in their electro-hydraulic rear axle steering system, is used for construction industry vehicles widely. Such systems have great influences on controllability, steering stability, driving comfort and safety of a vehicle. Such a complex system includes mechanical multi-body, hydraulic, and control components which are influenced each other. However, few previous works concerned the coupling effects from multidisciplinary view, in general just single domain detail model are built and studied. This paper presents a detailed 5 axle all-terrain crane with hydro-pneumatic suspension and multi-bridges steering system consisting of the mechanical parts of suspension and steering multi-body model with ADAMS, suspension and steering hydraulic model that contain cylinder, control valve, and hydraulic pipes, etc., and the control strategy are built with AMESim software. A co-simulation is carried out to study the handling and stability of the vehicle affected by the hydro-pneumatic suspension and electro-hydraulic steering system. Some typical handling maneuvers, such as cornering steering releasing test and pylon slalom course of test are carried out by co-simulation to evaluate the control strategy of the steering and hydro-pneumatic suspension performance numerically. Comparisons between measured data and simulation results validate the correctness of the model.

Roll Plane Analysis of Interconnected Hydro-Pneumatic Suspension Struts

2005 ◽  
Author(s):  
Dongpu Cao ◽  
Subhash Rakheja ◽  
Chun-Yi Su
Keyword(s):  
Heavy Vehicles ◽  
Vertical Stiffness ◽  
Fundamental Properties ◽  
Plane Analysis ◽  
Damping Characteristics ◽  
Pneumatic Suspension ◽  
Parametric Studies ◽  
Suspension Stiffness ◽  
Variable Damping ◽  
Stiffness And Damping

This study presents a compact hydro-pneumatic strut design with enhanced working area to reduce the design pressure requirements for suspension applications. The two struts are interconnected in the roll plane to realize enhanced roll properties of the suspension. The feedback effects of the interconnecting pipes on the suspension stiffness and damping properties are derived and discussed. The influences of fluid compressibility on the effective ride and roll properties are also investigated. Asymmetric and variable damping valves are further introduced to realize adequately damped and soft ride, and high low speed damping in the roll mode. Fundamental properties of the proposed interconnected configurations are derived and compared with those of the unconnected struts with an anti-roll bar, in terms of suspension vertical stiffness, roll stiffness, and vertical and roll mode damping. Parametric studies are also performed to study the role of interconnecting parameters on the essential suspension properties. The results indicate that interconnected suspension with inherent enhanced roll stiffness and damping characteristics offers significant potential to improve the dynamic roll performance of heavy vehicles, while retaining soft vertical ride. The effectiveness of the proposed concept is further illustrated through simulation results attained under two different deterministic excitations.

Rotordynamic Performance of a Rotor Supported on Bump Type Foil Gas Bearings: Experiments and Predictions

2006 ◽  
Vol 129 (3) ◽  
pp. 850-857 ◽  
Author(s):  
Luis San Andrés ◽  
Dario Rubio ◽  
Tae Ho Kim
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Load Capacity ◽  
Test System ◽  
Foil Bearings ◽  
Rotor Imbalance ◽  
Synchronous Motion ◽  
Damping Characteristics ◽  
Rotor Surface ◽  
Stiffness And Damping

Gas foil bearings (GFBs) satisfy the requirements for oil-free turbomachinery, i.e., simple construction and ensuring low drag friction and reliable high speed operation. However, GFBs have a limited load capacity and minimal damping, as well as frequency and amplitude dependent stiffness and damping characteristics. This paper provides experimental results of the rotordynamic performance of a small rotor supported on two bump-type GFBs of length and diameter equal to 38.10mm. Coast down rotor responses from 25krpm to rest are recorded for various imbalance conditions and increasing air feed pressures. The peak amplitudes of rotor synchronous motion at the system critical speed are not proportional to the imbalance introduced. Furthermore, for the largest imbalance, the test system shows subsynchronous motions from 20.5krpm to 15krpm with a whirl frequency at ∼50% of shaft speed. Rotor imbalance exacerbates the severity of subsynchronous motions, thus denoting a forced nonlinearity in the GFBs. The rotor dynamic analysis with calculated GFB force coefficients predicts a critical speed at 8.5krpm, as in the experiments; and importantly enough, unstable operation in the same speed range as the test results for the largest imbalance. Predicted imbalance responses do not agree with the rotor measurements while crossing the critical speed, except for the lowest imbalance case. Gas pressurization through the bearings’ side ameliorates rotor subsynchronous motions and reduces the peak amplitudes at the critical speed. Posttest inspection reveal wear spots on the top foils and rotor surface.

Nonlinear Isolator Optimization Using RMS Cost Function

2004 ◽  
Author(s):  
A. Narimani ◽  
M. F. Golnaraghi
Keyword(s):  
Closed Form Solution ◽  
Optimization Method ◽  
Relative Displacement ◽  
Form Solution ◽  
Jump Phenomenon ◽  
Nonlinear Parameters ◽  
Strongly Nonlinear ◽  
Damping Characteristics ◽  
Stiffness And Damping ◽  
Boundary Limits

In this paper using a modified averaging method the frequency response of a general nonlinear isolator is obtained. Stiffness and damping characteristics are considered cubic functions of displacement and velocity through the isolator. Analytical results are compared with those obtained by numerical integration in order to validate the closed form solution for strongly nonlinear isolator. While increasing the nonlinearity in the system improves the response of the isolator, stability and jump avoidance conditions set boundary limits for the parameters. The effects of nonlinear parameters to avoid jump phenomenon are discussed in detail. The set of parameters where the system behaves regularly are found and the nonlinear isolator is optimized based on RMS optimization method. Using this method the RMS function of absolute acceleration of the sprung mass is minimized versus the RMS function of relative displacement.

Research on Stiffness and Damping Characteristics of Fixed Oily Porous Materials Joint Interface

2011 ◽  
Vol 422 ◽  
pp. 575-579
Author(s):  
Chong Nian Qu ◽  
Liang Sheng Wu ◽  
Jian Feng Ma ◽  
Yi Chuan Xiao
Keyword(s):  
Porous Material ◽  
Porous Materials ◽  
Parallel Plate ◽  
Joint Interface ◽  
Force Model ◽  
Equivalent Stiffness ◽  
Contact State ◽  
Damping Characteristics ◽  
Stiffness And Damping ◽  
Damping Model

In this document, using the anti-squeezed force model in the narrow parallel plate when fluid is squeezed, the equivalent stiffness and damping model is derived. It is further verified that it can increase the stiffness and damping while there are oil between the joint interfaces theoretically. Because the contact state of oily porous material can divide into liquid and solid parts, the document supposes that it is correct and effective to think the stiffness and damping of the two parts as shunt connection.

Modelling Fluid Inertia Forces of Short Journal Bearings for Rotordynamic Applications

1993 ◽  
Author(s):  
A. El-Shafei
Keyword(s):  
Momentum Equation ◽  
Journal Bearings ◽  
Fluid Inertia ◽  
Radial Acceleration ◽  
Damping Characteristics ◽  
Energy Approximation ◽  
Form Model ◽  
Fluid Inertia Effect ◽  
Stiffness And Damping ◽  
Inertia Forces

Abstract It has been recently suggested that fluid inertia may play an important role in the dynamic behavior of rotors supported on journal bearings. This paper presents a model for fluid inertia forces in short cylindrical journal bearings based on an energy approximation. The inertialess velocity profiles predicted by the solution of Reynolds’ equation are inserted in the axial momentum equation multiplied by the axial velocity profile and integrated across the film thickness, to obtain the pressure in short journal bearings including the fluid inertia effect. The pressure is then integrated to obtain the fluid inertia forces. It is shown that the inertia forces thus obtained are proportional to the usual radial, centripetal, tangential and coriolis accelerations of the journal, in addition to a nonlinear radial acceleration. Moreover, it is shown that the inertia forces contribute to the stiffness and damping characteristics of the journal bearings. The inertia coefficients of the bearings are obtained in cartezian and cylindrical coordinates, for both uncavitated and cavitated bearings, and are plotted versus the eccentricity ratio. The model thus obtained is an analytical closed form model for fluid inertia forces in short journal bearings. Such a model is the most suitable for rotordynamic applications, particularly for time transient rotordynamic simulations.

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