Thermal Analysis of Vehicular Twin-Tube Hydraulic Gas-Precharged Shock Absorbers

In this study of temperature rising in vehicular twin-tube hydraulic gas-precharged shock absorbers,thermodynamic analyses were conducted via simulations.Equations on heat conduction,heat convection as well as radiation were derived by applying certain laws governing heat transfer;an equivalent thermal resistance network model of a shock absorber undergoing heat transfer was established innovatively;moreover,the shock absorber’s thermodynamic model of control volume system was built by using the first law of thermodynamics;and finally,time required for shock absorber to reach thermal equilibrium and corresponding value of steady temperature were calculated by programming.In this way,a lower thermal equilibrium temperature will be achieved,hence help to improve reliability of shock absorbers in work by offering low ambient temperature,by reducing amplitudes and frequencies of external incentives exerted on them and by increasing flow rate of ambient air passing around them.

Basic Problems in Design and Inverse Engineering Solution for Outer Characteristic of Vehicle Suspension Shock Absorbers

Based on the theory and the practical experiences of linearity design of feasible design area and inverse solution of non linear outer characteristic of suspension shock absorber, in accordance with non linearity outer characteristic formed by open up damping coefficient, full open damping coefficient and smoothness to safety ratio of suspension shock absorber, a method and a research conclusion of the feasible design and inverse solution for the basic problems of designing and inverse solution of non linear outer characteristic of suspension damping components are provided.

ANALYSIS OF THE DEFLECTION OF REEDS IN AUTOMOTIVE HYDRAULIC SHOCK ABSORBERS

The deformation of reeds in automotive hydraulic shock absorbers is analyzed with the finite element method. Combination of different thick reeds mounted on different supports is studied. The computational results show that deformation of the overlapped reeds is not always equal to the sum of deflection of single reed under any conditions. Experimental results prove computational results to be correct and computational method effective. The method of analysis and view of point can provide reference to the design and manufacture of hydraulic shock absorbers using reeds.

Study of relationship between motion of mechanisms in gas operated weapon and its shock absorber

The article deals with the motion of the breech block carrier and the weapon casing of an automatic weapon mounted on a flexible carriage and the base of the weapon.Earlier works,which did not consider the dynamic properties of the base of the weapon,did not allow to reconcile the calculated and experimental results of the weapon casing displacement when shooting from firing rests.For the analysis of the motion of individual parts,the methods of mathematical modelling and firing experiments using a high-speed camera were chosen.Calculations show the best accord with experiment when modelling the system with 4 degrees of freedom.The oscillation of the system regarding the movement of the breech block carrier and the weapon casing was investigated under changed conditions of rate of fire,the use of a muzzle brake and different types of shock absorbers.The velocities and displacements of the weapon casing and the breech block carrier at different values of the impulse of the gases to the breech block carrier were determined.

IDENTIFICATION OF NONLINEAR PROPERTIES OF AN AIRCRAFT LANDING GEAR SHOCK STRUT

A simple but realistic method for identifying nonlinear stiffness and damp-ing of an air-oil shock strut widely used in aircraft is developed.In the method a powerseries expansion is used to niodel the nonlinear dynamic properties of the strut. and after introducing new variables lhe nonlinear identitication problem can be reduced to alinear one with unknown linear paranieters. An unbiased, efficient and consistentestimator for the vector of the linear parameters is obtained under conditions of mini-mizing the sum of squared residuals which is assumed to be stationary and uncorrelatedwith the observed data.The order and the most effective independent variables in themodel are detennined by the criterion of residual series correlation infonnation entropyand the procedure of best subset regression, respectively. Experiinent demonstrates thatthe results are quite satisfactory, and the method developed is realistic, which can beused to study the dynamic properties of a strut in full detail.

CAD/CAE OF THE WORKING CHARACTERISTICS OF A NEW TYPE OF FLUID COUPLING SHOCK ABSORBER

For purpose of simulation of the working characteristics of a new type offluid coupling shock absorber for vibration protection of sensitive equipment, a physical model ispresented by analyzing the internal fluid dynamic phenomenon with respect to the coupling shockabsorber and implemented in MATLAB software package. Using the model it is possible to evaluate theimportance of different factors for design of the shock absorber. In the meantime, the key-modelmachine is designed for coupling dynamic test. Comparisons with experimental results confirm thevalidity of the model. So the CAD/CAE software has been developed in MATLAB for design andexperimental test of the new coupling shock absorber.

Effect of Porosity on the Mechanical Properties and Wear Performance of 2% Copper Reinforced Sintered Steel Used in Shock Absorber Piston Production

Powder metallurgy （P/M） method has mainly been used to produce automobile parts such as self-lubrication beds, shock absorber parts, and gear wheels. In order to investigate the effect of porosity on the mechanical and tribological properties in sintered steel, specimens with 10%, 15%, and 20% porosity were produced in a 10 mm×10 mm×55 mm prismatic shape by pre-alloying powders of the MPIF Fe-C-0.205 alloy used in the production of shock absorber pistons. Sintering was carried out at 900℃ for 45 min in an argon atmosphere. Tensile, charpy, and microhardness tests were performed on these specimens. In addition, the wear performance of a 2% Cu reinforced sintered steel alloy under dry sliding conditions was determined. Metallographic studies such as pore formation, worn surface, and fractured surface analyses were performed by scanning electron microscopy and optical microscopy. The results indicate that irregular pore formation tendencies increase with an increase in porosity （%）. Furthermore, an increase in porosity was shown to decrease the mechanical properties and increase the wear trace area and the friction coefficient of sintered steel.

DESIGN METHOD OF MAGNETORHEOLOGICAL FLUID SHOCK ABSORBER FOR CAR SUSPENSION

The Bingham constitutive model, which is previously used in depiction of magnetorheological （MR） fluids rheological behaviors for design devices, exhibits discontinuous characteristics in representation of pre-yield behaviors and post-yield behaviors. A Biviscous constitutive model is presented to depict rheological behaviors of MR fluids and design automotive shock absorber. Quasi-static flow equations of MR fluids in annular channels are set theoretically up based on Navier-Stokes equations and several rational simplifications are made. And both flow boundary conditions and flow compatibilities conditions are established. Meantime, analytical velocity profiles of MR fluids though annular channels are obtained via solution of the quasi-static flow equations using Biviscous constitutive model. The prediction methodology of damping force offered by MR fluid shock absorber is formulated and damping performances are predicated in order to determine design parameters. MR fluid shock absorber for Mazda 323 car suspension is designed and fabricated in Chongqing University, China. Measurements from sinusoidal displacement cycle by Shanchuan Shock Absorber Ltd. of China North Industry Corporation reveal that the analytical methodology and design theory are reasonable.

A new weir surface repair layer with shock absorbing cushion design

A shock absorbing cushion has never been introduced into any traditional weir surface repair layer design. However, shocks induced by high discharge with heavy sediment can easily produce brittle fracture and peeling over a weir surthce repair layer as it is impacted by floods accompanied by particles of different sizes. In this study, transcending traditional designs, the authors developed a composite unit designed with a shock absorbing cushion that has performed well during field tests, proving that the weir body can be effectively protected even if the composite units are directly laid on a severely uneven weir surface repair layer.

Vibration energy regeneration of electric vehicle shock absorber

The twin-tube shock absorber was studied and the relevant factors of thermal equilibrium were simulated. The dynamic model of the shock absorber was constructed and simulation curves of force-displacement and force-velocity were output. The experiment of the twin-tube shock absorber was carried out, and the results were compared with the modeling resultss. Further, the vibration energy regeneration model was established, and the bench simulation study was carried out. The re- sults showed that the energy regeneration model not only absorbed shock energy but also converted vibration energy into electricity energy.

APPLICATION OF MODERN ROBUST OPTIMAL DESIGN METHOD TO THE SHOCK ABSORBER IN A CAR*

To reduce the variation of velocity characteristic of the shock absorber in acar, a modern robust optimal design method is applied to its structural parameters design. Firstly,the method is used to obtain the robust values which have low sensitivity to velocitycharacteristic and analyze the influences of the parameters on velocity characteristic. Secondly,the method is used to obtain their maximum tolerances under the condition of ensuring productquality. The results obviously improve the velocity characteristic.

Water Hammer Model of Shock Absorber Throttle Slice

In allusion to easy invalidation of damping valve in vehicle shock absorber caused by the impact from the road surface, the importance of the study of damping valve water hammer pressure is presented. The physical model of damping valve with the circle throttle slice is established. The time for the throttle slice deformation is studied by using the finite software, and the laws that how the structure parameters affect the deformation time are obtained. Combining the theory of water hammer, the water hammer initial and boundary condition of the damping valve is deduced, and the water hammer model of throttle slice is established. The analysis of simulation results indicates that the water hammer pressure amplitude and the amount of water hammer oscillation period can be reduced and the dependability of the valve can be enhanced by modifying the structure parameters and aperture width between slice and valve body.

Processing the rig test data of an air filling twin-tube shock absorber

A separation method is proposed to design and improve shock absorber according to the characteristics of each force. The method is validated by rig test. The force data measured during rig test is the resultant force of damping force, rebound force produced by pressed air, and friction force. Different characters of damping force, air rebound force and friction force can be applied to seperate each force from others. A massive produced air filling shock absorber is adopted for the validation. The statistic test is used to get the displacement-force curves. The data are used as the input of separation calculation. Then the tests are carried out again to obtain the force data without air rebound force. The force without air rebound is compared to the data derived from the former tests with the separation method. The result shows that this method can separate the damping force and the air elastic force.

PARAMETRIC MATCHING SELECTION OF MULTI-MEDIUM COUPLING SHOCK ABSORBER

To achieve the dual demand of resisting violent impact and attenuating vibration in vibration-impact-safety of protection for precision equipment such as MEMS packaging system, a theo- retical mathematical model of multi-medium coupling shock absorber is presented. The coupling of quadratic damping, linear damping, Coulomb damping and nonlinear spring are considered in the model. The approximate theoretical calculating formulae are deduced by introducing transformation-tactics. The contrasts between the analytical results and numerical integration results are developed. The resisting impact characteristics of the model are also analyzed in progress. In the meantime, the optimum model of the parameters matching selection for design of the shock absorber is built. The example design is illustrated to confirm the validity of the modeling method and the theoretical solution.

Analysis of thermal-mechanical coupled characteristics of vehicle twin-tube shock absorber

A comprehensive model that included mechanical dynamics of the shock absorber coupled with its thermal properties was proposed innovatively.Moreover a thermal-mechanical coupled model which reflected the closed-loop positive feedback system was established by using MATLAB/SIMULINK,and some curves of shock absorber temperature rising characteristic were obtained by simulation ＆computation under several operating modes and different parameters conditions.Research results show that：shock absorber design parameters,external excitations,and thermo-physical properties parameter,such as oil density have effect on the shock absorber temperature rising characteristic.However other thermo-physical properties parameters,such as oil specific heat,cylinder density,cylinder specific heat,and cylinder thermal conductivity,have no effect on it.The results may be used for studying reliability design of the shock absorber.

COMPLEX NONLINEAR MATHEMATICAL MODEL FOR A KIND OF VEHICLE SHOCK ABSORBORS

A nonlinear mathematical model for the shock absorber in TJ7100 is developed. The oil compressibility and the entrapped gas in the oil are considered in the model. As a result, the hysteresis in the force velocity diagram is included. The results of computer simulation and the experiment are basically identical. The MATLAB/SIMULINK is used for the development of the simulation software. It is found that the pressure inside the cylinder is high if the inputs of velocity or displacement are big by simulation. This is certainly one of the main reasons for which the leak is appeared between the rod and the seal of the shock absorbers for a relatively short time in China.

A Phase-Dependent Hypothesis for Locomotor Functions of Human Foot Complex

The human foot is a very complex structure comprising numerous bones, muscles, ligaments and synovial joints. As the only component in contact with the ground, the foot complex delivers a variety of biomechanical functions during human locomotion, e.g. body support and propulsion, stability maintenance and impact absorption. These need the human foot to be rigid and damped to transmit ground reaction forces to the upper body and maintain body stability, and also to be compliant and resilient to moderate risky impacts and save energy. How does the human foot achieve these apparent conflicting functions？ In this study, we propose a phase-dependent hypothesis for the overall locomotor functions of the human foot complex based on in-vivo measurements of human natural gait and simulation results of a mathematical foot model. We propse that foot functions are highly dependent on gait phase, which is a major characteristics of human locomotion. In early stance just after heel strike, the foot mainly works as a shock absorber by moderating high impacts using the viscouselastic heel pad in both vertical and horizontal directions. In mid-stance phase （-80% of stance phase）, the foot complex can be considered as a springy rocker, reserving external mechanical work using the foot arch whilst moving ground contact point forward along a curved path to maintain body stability. In late stance after heel off, the foot complex mainly serves as a force modulator like a gear box, modulating effective mechanical advantages of ankle plantiflexor muscles using metatarsal-phalangeal joints. A sound under- standing of how diverse functions are implemented in a simple foot segment during human locomotion might be useful to gain insight into the overall foot locomotor functions and hence to facilitate clinical diagnosis, rehabilitation product design and humanoid robot development.

Dynamic Analysis for Structures Isolated with Dampers

In this paper, mathematical models and dynamic analyses for both SDOF and MDOF structures isolated with dampers are established and performed, and a comprehensive computation method is provided. The shock absorbing effect is illustrated through an example of a two DOF damper-isolated system excited by sinusoidal waves and actual ground acceleration input recorded in earthquakes. It is shown that most of the responses of the structure with dampers reduce greatly near the resonant zone, but acceleration is enlarged in the lower or higher frequency zone; among various parameters, the influence of frictional coefficient n is the most significant, that of damping ratio of the dampers , is the second, and that of stiffness coefficient of the dampers k, is the slightest.

Application of Elastic Stiffness Damper with Disc Spring to Numerical Control Punch

The paper aims to analyze the impacts of punch damper stiffness on equipment base and vibration, andintroduce the development and application of a disc spring damper featured hard-soft-hard variable stiffness. Adamper has four damping columns with C-type disc springs whose laminates plate number gradually increases setby set. Compared with its counterparts, this kind of dampers has the advantages of high energy absorption andvibration damping effect, which not only can effectively reduce the vibration of the foundation of punch press,but also prevents the vibration range from increasing. Also, this kind of dampers is of low cost and convenient touse.

AN ELASTIC OSCILLATION MODEL FOR GOODS IN A SHORTAGE MARKET

In this paper. an oscillated model.which results from the shortage action in market economy with elastic replacement of goods is obtained.And some naturalrelations between the model and a typically oscillatory model are established Theresults can interpret some market phenomena and provied the theoretical tools for theeconomic program.