Comparisons Between Dynamic Characteristics of Pneumatic, Magnetorheological, and Hydraulic Shock Absorbers

2012 ◽  
Author(s):  
A. M. Salem ◽  
S. Olutunde Oyadiji
Keyword(s):  
Dynamic Characteristics ◽  
Shock Absorber ◽  
Testing Machine ◽  
Mr Damper ◽  
Nonlinear Behaviour ◽  
Hydraulic Shock ◽  
Shock Absorbers ◽  
Wide Range ◽  
Force Velocity ◽  
Force Displacement

The dynamic performance of automotive vehicles is influenced by the suspension system design. Suspensions owing damping elements with a wide range of non-linear behaviour can provide higher mobility and better ride comfort performances. Pneumatic suspensions due to their inherent nonlinear behaviour can provide high mobility performance while suspensions with MR dampers can provide this nonlinearity through the controllable damping force produced by the control of the MR fluid. The pneumatic and MR suspension models are usually developed from experimental force-displacement and force-velocity characteristics. The purpose of this paper is to measure and compare the dynamic characteristics of pneumatic, magnetorheological, and hydraulic shock absorbers. The study is carried out through measuring the characteristics of the different types of dampers at different frequencies and amplitudes using an Electro-Servo Hydraulic (ESH) testing machine. The shock absorber is subjected to sinusoidal excitation of frequency varying from 0 to 10 Hz, and amplitude varying from 0 to 10 mm. In the case of the MR damper, the tests are also done at different current levels of between 0 and 2 amp. The input displacement and acceleration to the shock absorber were measured using an LVDT (Linear Voltage Displacement Transducer) and an accelerometer, respectively while the input velocity was derived from the measured displacement and acceleration. This dual identification of the input velocity was done in order to ensure accurate representation of the velocity. The output force response of the shock absorber was measured by means of a force transducer. The force-displacement and force-velocity characteristics of each shock absorber were subsequently derived from the measured data. The results show the tunability of the MR damper characteristics in comparison to those of the pneumatic and hydraulic dampers.

An Experimentally Validated Model of a Motorcycle Shock Absorber for Studying Suspension Dynamics

2011 ◽  
Author(s):  
Alberto Doria ◽  
Marco Lucchini
Keyword(s):  
Shock Absorber ◽  
Fluid Motion ◽  
Shock Absorbers ◽  
Large Hysteresis ◽  
Wide Range ◽  
Compressibility Coefficient ◽  
Suspension Dynamics ◽  
Flow Through ◽  
Force Velocity ◽  
Compensation Chamber

Nowadays advanced shock absorbers are equipped with hydraulic valves that offer many possibilities of adjustment of orifices and shims. The theoretical force-velocity curve can be accurately designed and modified by means of these adjustments, in order to achieve the desired performance. Actually, compressibility of gas in compensation chamber, compressibility of oil, cavitation and compliance of seals and cylinders can significantly alter the force-velocity diagram. In some working conditions the behavior of the shock absorber may differ from the optimized one, with important consequences on the performance of the vehicle. Therefore there is the need of mathematical models able to predict the behavior of shock absorbers in the presence of large hysteresis phenomena, these models cannot be too complex and cumbersome, because they have to be implemented in multibody models of vehicles. The paper starts showing some experimental data collected by testing in laboratory a motorcycle shock absorber and aims to quantify the effect of hysteresis on performance and tuning. Then a mathematical model of a shock absorber is developed and presented. Valves are modeled with detail taking into account flow through bleed orifices and shim stacks and the effect of adjustments can be predicted. Compressibility of oil and compliances are taken into account by means of an equivalent compressibility coefficient. The model has a little number of parameters and a method is presented for identifying these parameters from laboratory tests. Some simulations show that the model is able to predict the behavior of the shock absorber over a wide range of frequencies. After validation, the shock absorber model is implemented into a two degree of freedom model of a rear suspension of a motorcycle. A MATLAB code is developed to solve the system of differential equations that describe the dynamic response of the suspension and the fluid motion inside the shock absorber. The response of the vehicle to a road bump is simulated. Acceleration of the suspended mass and tire load fluctuations show the effect of hysteresis and of adjustments of shock absorber on the performance of the vehicle.

Investigation into the dynamic characteristics of downhole perforation tools with multiple shock absorbers

2019 ◽  
Vol 20 (6) ◽  
pp. 622
Author(s):  
Xiaoqiang Guo ◽  
Jun Liu ◽  
Guorong Wang ◽  
Qingyou Liu ◽  
Xianming Song
Keyword(s):  
Dynamic Characteristics ◽  
Field Experiments ◽  
Shock Absorber ◽  
Response Amplitude ◽  
Ansys Software ◽  
Maximum Acceleration ◽  
Shock Absorbers ◽  
Tubing String ◽  
Testing Instruments ◽  
Multiple Shock

The use of large-charged perforating bullets after well perforation produces large impact loads, which can easily lead to early unsealing of packers, damage to testing instruments, stress failure of tubing strings, buckling deformation, and other adverse incidents. This study focuses on the safety of large-charged perforating bullets used in downhole tools. In addition, a dynamic model of downhole perforation tools with multi-shock absorber was designed, and ANSYS software was used to validate its accuracy. Perforation impact loading field experiments were developed, and the loading pressure was measured over time to obtain an even more accurate equation to calculate loading. Analysis of the effects of different numbers of shock absorbers on the dynamic characteristics of downhole tools was conducted, finding that increasing the number of shock absorbers from one to two significantly decreased the dynamic response amplitude of the downhole tools (displacement, axial force, and packer force). However, when the number was increased to three, the change in response amplitude was not significant. Based on the maximum acceleration of each section of the tubing string, the testing instrument is best installed at its upper end. As the number of shock absorbers is increased, the number of regions of the tubing string that undergo buckling deformation decreases. Increasing the number of shock absorbers helps prevent buckling deformation in the tubing string, and increases its service life.

The Effects of Fluid and Mechanical Compliance on the Performance of Hydraulic Shock Absorbers

1974 ◽  
Vol 96 (1) ◽  
pp. 101-106 ◽  
Author(s):  
R. W. Mayne
Keyword(s):  
Differential Equations ◽  
Shock Absorber ◽  
Rigid Wall ◽  
Hydraulic Shock ◽  
Orifice Area ◽  
Shock Absorbers ◽  
Constant Area ◽  
Mechanical Compliance ◽  
Hydraulic Shock Absorber ◽  
The Ideal

Dimensionless differential equations are developed which model a hydraulic shock absorber. These equations are solved numerically to determine quantitatively the effects of fluid compressibility and series and parallel springs on the shock absorber operation. Both variable and constant orifice area are considered for a system protecting a mass during impact against a rigid wall. The results show that a finely tuned variable area shock absorber is degraded by the considered forms of compliance. Performance of the constant area shock absorber can be improved by including compliance and, with an appropriate parallel spring, the ideal flat deceleration profile can be obtained without variable orifice area.

scholarly journals A General Modeling Approach for Shock Absorbers: 2 DoF MR Damper Case Study

2021 ◽  
Vol 7 ◽  
Author(s):  
Jorge de-J. Lozoya-Santos ◽  
Juan C. Tudon-Martinez ◽  
Ruben Morales-Menendez ◽  
Olivier Sename ◽  
Andrea Spaggiari ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Degrees Of Freedom ◽  
Linear Models ◽  
Mr Damper ◽  
Shock Absorbers ◽  
Magneto Rheological ◽  
The Mathematical Model ◽  
Force Displacement ◽  
Standard Tests

A methodology is proposed for designing a mathematical model for shock absorbers; the proposal is guided by characteristic diagrams of the shock absorbers. These characteristic diagrams (Force-Displacement, Velocity-Acceleration) are easily constructed from experimental data generated by standard tests. By analyzing the diagrams at different frequencies of interest, they can be classified into one of seven patterns, to guide the design of a model. Finally, the identification of the mathematical model can be obtained using conventional algorithms. This methodology has generated highly non-linear models for 2 degrees of freedom magneto-rheological dampers with high precision (2–10% errors).

Experimental Investigation on Magnetorheological Damper’s Characterization

2015 ◽  
Vol 1115 ◽  
pp. 476-479 ◽  
Author(s):  
Mohammad Meftahul Ferdaus ◽  
Muhammad Mahbubur Rashid ◽  
Mst. Nafisa Tamanna Shanta ◽  
Muhammad Hasibul Hasan
Keyword(s):  
Experimental Analysis ◽  
Testing Machine ◽  
Mr Damper ◽  
Stroke Rate ◽  
Brief Experimental Analysis ◽  
Stroke Length ◽  
Active Devices ◽  
Mr Fluids ◽  
Wide Range ◽  
Day By Day

Magnetorheological (MR) damper is one of the most advanced application of semi active devices. Its use is increasing day by day due to its huge advantages and wide range of application. The force delivered by MR damper can be varied by changing the viscosity of its internal MR fluids. Till now no details experimental analysis has been accomplished by considering various parameters. In this paper a brief experimental analysis has been investigated with the help of Universal Testing Machine to characterize MR damper. To characterize accurately MR damper has been analyzed experimentally for different stroke length, stroke rate, stroke mode. From the experimental results it is seen that the force delivered by MR damper has a proportional relation with input excitation current, stroke length and stroke rate.

scholarly journals Research on Theoretical Modeling and Parameter Sensitivity of a Single-Rod Double-Cylinder and Double-Coil Magnetorheological Damper

2020 ◽  
Vol 2020 ◽  
pp. 1-20
Author(s):  
Suojun Hou ◽  
Gang Liu
Keyword(s):  
Inertial Force ◽  
Mr Damper ◽  
Bond Graph ◽  
Inertia Force ◽  
Force Model ◽  
Damping Force ◽  
Mr Fluid ◽  
Force Velocity ◽  
Force Displacement ◽  
Bond Graph Theory

For the single-rod double-cylinder and double-coil magnetorheological (MR) damper studied in this paper, the damping force model of the damper is established by adopting multidisciplinary domain modeling method bond graph theory. Firstly, combined with the structure of the MR damper, the bond graph model of the MR damper was established, the damping force model of the damper was derived through the bond graph theory, and the influence factors, such as the displacement, velocity, and acceleration of the damper were considered in the model. Based on the simulation of force-displacement and force-velocity characteristics of the damping force carried out by the damper theoretical model under different currents and velocities as well as the comparison with the damper bench test results, it was found that the force-displacement and force-velocity characteristic experiment curves of the damper agreed well with the simulation results. Under different working conditions, the maximum error of damping force of the MR damper was 7.2%. The damping force model of the MR damper studied in this paper was compared with that of the damper without considering the inertia force of MR fluid, and the influence of the inertia force of MR fluid on the damping force of the MR damper was analyzed. The results show that when the frequency of the damper is large, the inertial force of MR fluid has an important influence on the damping force; therefore, considering the inertial force of MR fluid in the model can greatly improve the accuracy of the model. The influence degree of key parameters on the damping force of the MR damper was studied through the theoretical model; such key parameters ranging from large to small were the channel clearance, energizing current, piston diameter, motion velocity, channel length, zero-field viscosity of MR fluid, and nitrogen pressure. This provides a basis for the adjustment of the damping force of the MR damper.

scholarly journals The simplified approach to numerical modeling of polyurethane foam shock absorbers of complex structure: determination of effective mechanical properties and preparation of mathematical models of a homogenized material

2021 ◽  
Vol 2131 (4) ◽  
pp. 042056
Author(s):  
A Semenov ◽  
A Smirnov ◽  
M Stepanov ◽  
N Kharaldin ◽  
A Borovkov
Keyword(s):  
Strain Rate ◽  
Polyurethane Foam ◽  
Shock Absorber ◽  
Complex Structure ◽  
Material Model ◽  
Material Behavior ◽  
Stress Strain ◽  
Simplified Approach ◽  
Shock Absorbers ◽  
Wide Range

Abstract The first part of this paper is devoted to modeling foam taking into account the effect of strain rate on material behavior in the LS-Dyna software package for solving dynamic problems in a wide range of speeds. The MAT_083 material model was used, which analyzes the stress-strain state considering the dependence on the strain rate. The process of adaptation of experimental data for use in the MAT_083 material model is described. The second part of this study touches upon the homogenization of the properties of a shock absorber consisting of SKU-PFL-100 polyurethane (the modeling approach is described in the previous article) and polyurethane foam, the model of which is described in the first part of this paper. Homogenization of the shock absorber is carried out in order to reduce the number of elements in the problem and, accordingly, to improve the calculation performance. The stress-strain curves obtained during the compression of a shock absorber are used in the material MAT_083.

scholarly journals Development of Pneumatic Shock Absorber by Variable Damping

2019 ◽  
Vol 8 (6) ◽  
pp. 1355-1360
Keyword(s):  
Shock Absorber ◽  
Low Cost ◽  
Advanced Technology ◽  
Hydraulic Shock ◽  
Damping Properties ◽  
The Road ◽  
Shock Absorbers ◽  
Variable Damping ◽  
Cost Efficient ◽  
Pneumatic Shock

In commercial models and premium vehicles the damping is varied by sensing the road conditions, driver’s action etc. using ECU’s and damping properties are varied every second. This advanced technology is very costly and complicated for middle class consumers who also need some comfort with low cost. The main issue here is to vary the damping of hydraulic shock absorbers according to the shock to which it is subjected. Thus by sensing the speed of the shock absorber and changing the vibration absorbing capacity of the damper with respect to it will surely be useful. In this project we used a spring valve to sense the speed of the Shock absorber and controlling the valve which is fitted inside the damper. By Variable damping pneumatic shock absorber we can get enough comfort with a simple and cost efficient setup.

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