Wyniki wyszukiwania - Biblioteka Nauki

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On „VZN" damper behaviour at crash

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Niculescu A. I. , Jankowski A. , Sireteanu T.

Journal of KONES

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2009

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tom Vol. 16, No. 2

369-374

EN

On landing operation, a brutal contact with the dech or ground, can damage the plane or chopper and hurt the pilot, the crew or the passengers. The paper presents the advantages confer by suspensions using VZN dampers, in this situation. The Romanian self adjustable damper (shock-absorber) concept- VZN-granted with European Patent EU 1190184 and Romanian Patent 118546 assures damping coefficients increasingly by stroke from lower value up to the very high values, giving thus possibility to dissipate a huge energy at all speed regimes high, medium or low. With a convenient damping valve placement and/or dimension, the VZN concept confers possibilities to assure constant decelerationforces, at the human body limit resistance, this solution dissipating the maximal energy ąuantity. The paper indicates solutions for VZN tuning in order to be used to realize constant deceleration at crash and developed one of them for a practical device realizes. The samples where developed so to be realized with components used in actual automotive shock absorber manufacturing, so prototypes being easy to realize. Despite the simulations was realized considering standard damper dissipating energy function piston speed, not sąuare piston speed, the standard damper dissipated 48.5% lower energy comparative to VZN one. This means in the same situation in which VZN damper reduces constant speed from 20 [km/h] to zero, the standard dampers reduces speed up to 11.5[km/h], then collapsing the aerial vehicle.

2

Experimental Identification of a Magnetorheological Damper Model to Compare Semi-Active Control Strategies of Vehicle Suspensions

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Sireteanu T. , Stancioiu D. , Giuclea M. , Stammers C. W.

Mechanika / Akademia Górniczo-Hutnicza im. St. Staszica

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2003

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tom T. 22, z. 3

433-438

EN

The efficiency of various semiractive control strategies of vehicle suspensions equipped by magnetorheological fluid dampers (MRD) are compared. The parametric model of the damper dynamie behaviour is developed by an inverse method employing genetic algorithms. The model parameters are determined using the measured damping characteristics for a set of constant control current values and harmonie imposed motion. The model is validated on the data measured for variable control current and different types of damper toading. Taking into account the good agreement between predicted and measured data, the obtained model is used to compare by numerical simulation the efficiency of two semi-active control strategies (balance logic, sky-hook) used to improve the vehicle comfort.

3

Advantages conferred by shock absorbers with cylindrical actuator application to landing gear

100%

Niculescu A. I. , Jankowski A. , Kowalski M. , Sireteanu T.

Journal of KONES

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2016

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tom Vol. 23, No. 1

255--262

EN

Shock absorber with cylindrical actuator is a new concept of integrated damper with floating device, in international patent application PCT/EP2016/061515, with wide application in road, rail and aerial vehicles. Comparative to the known solution with rubber sleeves or bellows, the new one is capable to work at more increased pressure being more compact and due to metallic cylinder is more reliable. The other important advantage consists of it applicability at any kind of shock absorber without any special preparation, the solution consisting of replacing the dust shield with a pneumatic cylinder sealed against rod with a gasket and sliding closed in the lower part by sealing element/s fitted in trough/troughs practiced in an annular body fastened against the outer cylinder. For a better behaviour the patent application contains and solutions with double sliding sealing working at high pressure and thus assuring enough floating forces to sustain the vehicle without standard metallic spring so it can be utilized successfully in aerial vehicles landing gear. By using displacement and pressure transducers and equipment of control and command, it becomes an active suspension. The paper presents the double sliding sealing solution and demonstrates, by simulation the advantages confer by this new solution of shock absorber with cylindrical actuator in landing gear. This purpose was realized a virtual suspension model on which simulated hard landing for vehicle load and unload states, for different pneumatic spring preloaded forces.

4

A novel device with variable friction for shock and vibration control

75%

Sireteanu T. , Mitu A. M. , Ghitau G. , Niculescu A. , Jankowski A. , Kowalski M.

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2017

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tom Vol. 24, No. 3

261--268

EN

In this article a passive system, which exploits the properties of the Coulomb friction and leads to high affordability of controlling shocks and vibrations by means of cheap devices is presented. The friction force developed by the proposed device is dependent on the motion stroke by convenient modulation of contact force between the elements of friction coupling. For providing the system self-centring properties or necessary vertical load capacity, coil springs can be incorporated into the device structure. The device hysteresis characteristic can be simply adjusted to comply with requirements of the considered application. A general mathematical model of device dynamic behaviour is developed and applied to shock and vibration isolation systems. The article presents a novel passive device with variable friction which hysteresis force-displacement characteristics have “butterfly” shape, achieved by appropriate design of friction coupling. This shape of hysteresis loops can mitigate the drawbacks of constant friction devices. The schematic of mechanical systems to analyse the dynamic behaviour of shock and vibration isolation systems with variable friction device are shown.