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Selected issues of hydropneumatic suspension design for a high-speed tracked vehicle

Rybak Piotr Andrzej, Wojciechowski Michał, Hryciów Zdzisław

Systemy Logistyczne Wojsk

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2024

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Vol. 60, no. 1

23--48

EN

he effective operation of high-speed tracked vehicles in a combat vehicle configuration depends primarily on the correct identification of the expected operating conditions, already in the design or modernisation phase. This applies to both terrain, meteorological and climatic conditions. This approach considers the most unfavourable driving conditions and the level of dynamic loads acting on the vehicle hull, crew and equipment when making calculations. The dominant source of dynamic loads is movement at high speed on unpaved roads, off-road and when overcoming natural and artificial terrain obstacles of a predetermined or random nature. An important system responsible for the safety and reliability of this type of vehicle is the suspension. An appropriate design of the suspension parameters allows to reduce the negative dynamic loads (research hypothesis). The aim of the research was to develop a preliminary project of an initial suspension element – a hydropneumatic spring for a high-speed tracked vehicle - that allows minimising dynamic loads. The study used both theoretical and empirical research methods, including analysis, synthesis, deduction, induction, comparison and inference. The paper presents selected issues from the suspension design process for a high-speed tracked vehicle equipped with a hydropneumatic suspension. The problem was solved in three stages. In the first stage, the design of the hydropneumatic suspension unit, placed in the control arm, was made and the basic parameters were selected. In the second, the spring characteristic of the hydropneumatic unit was determined on the example of a hypothetical vehicle with assumed tactical and technical parameters. In the third stage, the strength of the control arm structure, under the heaviest load conditions, was checked using the Finite Element Method (FEM). The results obtained showed that the advantages of the hydropneumatic suspension, such as: progressive spring characteristics, improved vibration damping, possibility of introducing a semi-active or active suspension system, modularity of the structure and ease of maintenance and repair, make it more and more widely used in modern high-speed tracked vehicles.

PL

Efektywna eksploatacja szybkobieżnych pojazdów gąsienicowych, w konfiguracji wozu bojowego, związana jest głównie z właściwym, już na etapie projektowania lub modernizacji, określeniem przewidy- wanych warunków użytkowania. Dotyczy to zarówno warunków terenowych, meteorologicznych, jak też klimatycznych. Konsekwencją takiego podejścia jest przyjęcie najbardziej niekorzystnych warunków ruchu oraz poziomu obciążeń dynamicznych działających na kadłub pojazdu, załogę i wyposażenie. Dominują- cym źródłem obciążeń dynamicznych jest ruch ze znacznymi prędkościami po drogach nieutwardzonych, bezdrożach oraz podczas pokonywania naturalnych i sztucznych przeszkód terenowych o charakterze zdeterminowanym lub losowym. Istotnym układem odpowiedzialnym za bezpieczeństwo i niezawodność tego typu pojazdów jest zawieszenie. Odpowiedni dobór parametrów zawieszenia pozwala na ogranicze- nie negatywnych obciążeń dynamicznych (hipoteza badawcza). Celem badań było opracowanie projektu wstępnego elementu zawieszenia – resora hydropneumatycznego dla szybkobieżnego pojazdu gąsienico- wego, pozwalającego na minimalizację obciążeń dynamicznych. W badaniu wykorzystano zarówno teore- tyczne, jak i empiryczne metody badawcze, a wśród nich analizę, syntezę, dedukcję, indukcję, porównanie i wnioskowanie. W pracy przedstawiono wybrane zagadnienia z procesu projektowania zawieszenia dla szybkobieżnego pojazdu gąsienicowego wyposażonego w zawieszenie hydropneumatyczne. Zagadnienie rozwiązywano w trzech etapach. W pierwszym etapie wykonano projekt resora hydropneumatycznego zawieszenia typu wahaczowego i dobrano podstawowe parametry. W drugim wyznaczono charaktery- stykę sprężystości elementu hydropneumatycznego na przykładzie hipotetycznego pojazdu o założonych parametrach taktyczno-technicznych. W trzecim etapie, sprawdzono wytrzymałość konstrukcji wahacza przy najcięższych warunkach obciążenia z wykorzystaniem metody elementów skończonych. Otrzymane wyniki wykazały, że zalety zawieszenia hydropneumatycznego takie jak: progresywna charakterystyka sprężystości, poprawa tłumienia drgań, możliwość wprowadzeniu układu półaktywnego lub aktywnego zawieszenia, modułowość konstrukcji oraz podatność obsługowa i naprawcza sprawiają, że znajduje ono coraz szersze zastosowanie we współczesnych szybkobieżnych pojazdach gąsienicowych.

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Hydropneumatic suspension testing of a wheeled armoured personnel carrier

Hryciów Zdzisław, Rybak Piotr, Wojciechowski Michał, Wachowiak Przemysław, Kalicki Bartosz

Eksploatacja i Niezawodność

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2023

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Vol. 25, no. 2

art. no. 162497

EN

The purpose of this study was to determine the effect of gas pressure and temperature on the spring characteristic of a HP strut used in a wheeled armoured personnel carrier. The research was performed based on a simulation model. Data to validate the model were obtained during experimental tests. The results indicate, among other things, that the friction generated in the seals is an important source of resistance force. Comparison of the simulation results with the measured characteristics indicates a proper modelling of the strut operation. Simulation studies have indicated that it is easy to modify the required suspension parameters by adjusting the initial gas pressure. A linear effect of pressure on static deflection can be assumed. Temperature has a strong influence on the spring characteristic. When it changes, significant changes in vehicle height are observed due to the lack of a compensation system. The temperature changes are not only due to changes in ambient temperature, but also by intense heating of the HP struts caused by the vehicle moving over rough terrain.

3

Assessment of the impact of wear and tear of rubber elements in tracked mechanism on the dynamic loads of high-speed tracked vehicles

Rybak Piotr, Hryciów Zdzisław, Michałowski Bogusław, Wiśniewski Andrzej

Acta Mechanica et Automatica

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2023

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Vol. 17, no. 1

85--94

EN

The operation of high-speed tracked vehicles takes place in difficult terrain conditions. Hence, to obtain a high operational relia-bility, the design or modernisation process must be precise and should consider even the slightest details. The article presents issues re-lated to the problem of formulating vehicle models using partial models of flexible elements used in tracked mechanisms. Changes occur-ring in the shape and properties of elements such as track pads and roadwheel bandages as a consequence of operating conditions are presented. These changes are reflected in the presented elastic–damping characteristics of components of the crawler mechanism. Nu-merical studies have shown that deterioration of chassis suspension components after a significant mileage may increase dynamic loads (forces) acting on the running gear. Increased forces in the running gear naturally result in increased stresses in the road surface on which the vehicle is travelling, which can pose a danger (or excessive wear and tear) to road infrastructure components such as culverts, bridges and viaducts. In the literature, model tests of objects are carried out on models that represent new vehicles, and the characteristics of the adopted elements correspond to elements not affected by the process and operating conditions. Its influence should not be ignored in the design, testing and running of a special vehicle. The tracked mechanism, as running gear, is designed for special high-speed vehicles for off-road and off-road driving. Its design ensures high off-road traversability. The dynamic loads originating from off-road driving are super-imposed on those generated by the engine, drive train and interaction of the tracks with the roadwheels, sprocket, idler and supporting tracks return rollers.

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The safety of wheelchair occupants in motor vehicles

Hryciów Zdzisław

Archiwum Motoryzacji

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2022

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Vol. 97, nr 3

5--13

EN

Ensuring the free movement of disabled people, including the use of vehicles, is a fundamental right. Therefore, efforts should be made to draw up standards regulating both organisational and technical aspects related to the construction and testing of wheelchairs. The main purpose of the paper is a review the literature related to wheelchair transport safety and the current standards for wheelchair crash testing Wheelchair users must securely and safely attach their wheelchair to the vehicle when travelling. The most common methods include securing with a four-belt system or using docking systems. Docking systems allow the disabled person to restrain the wheelchair themselves. Their main limitation is the lack of standardisation. Issues related to in-vehicle wheelchair design and testing are mainly described in international ISO standards and, in the US, in ANSI standards. Not all wheelchairs are crash tested. Before using wheelchairs, it should be checked if they can be mounted in a car. An important issue is education of wheelchair users and their carers on proper wheelchair securing. Even when wheelchairs are effectively secured, occupants in wheelchairs could be seriously and fatally injured because of improperly used and positioned belt restraints.

5

The influence of temperature on the damping characteristic of hydraulic shock absorbers

Hryciów Zdzisław, Rybak Piotr, Gieleta Roman

Eksploatacja i Niezawodność

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2021

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Vol. 23, no. 2

346--351

EN

This paper presents the results of bench-tests and calculations assessing the influence of temperature on the performance of a two-pipe hydraulic shock absorber. The shock absorber prepared for the tests was cooled with dry ice to a temperature corresponding to that associated with the average winter conditions in a temperate climate. The temperature range of the shock absorber during testing was ensured via equipping it with a thermocouple and monitoring it with a thermal imaging camera. During testing, the shock absorber was subjected to kinematic forces of a selected frequency with two different, fixed displacement amplitudes. The results of the tests showed a direct correlation between the decrease of component resistance at lower temperatures. The rate of change in resistance was higher at lower temperatures. It was also found that the energy dissipated in one shock cycle decreased linearly with an increasing temperature. Finally, a method for determining the ideal use temperature of the shock absorber for the assumed operating conditions was also presented.

6

Evaluation of the influence of friction in a multi-leaf spring on the working conditions of a truck driver

Hryciów Zdzisław, Krasoń Wiesław, Wysocki Józef

Eksploatacja i Niezawodność

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2021

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Vol. 23, no. 3

422--429

EN

This article presents a simulation study of the suspension system in a vehicle that weighs approximately 12 tons (class N2). The authors have tested the influence of experimentally determined values of friction coefficients on the energy dissipated in the multi-leaf spring. The study was carried out using finite element analysis with LS-DYNA software. A nonlinear vibration model of the complete spring was developed, including the variable friction forces between the leafs. The model takes into account the sprung and unsprung mass of the chassis. Numerical tests were carried out using three different coefficients of friction (determined experimentally) for a selected speed of the car. Random realizations of the road micro-profile (type A, B, C) recommended by ISO 8608 were used. The results of the tests were presented in the form of acceleration curves in the vertical direction, comparative plots of daily vibration exposure A(8) and vibration transmission coefficient (T), and the distributions of RMS acceleration in frequency of one-third octave bands. This data was used to assess the quality of the vibration isolation system between the front suspension of the vehicle and the driver’s seat.

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Assessment of the effect of passenger car wheel unbalance on driving comfort

Hryciów Zdzisław, Wiśniewski Andrzej, Rybak Piotr, Tarnożek Tomasz

Archiwum Motoryzacji

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2021

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Vol. 94, nr 4

61--71

EN

This paper presents the results of experimental investigations of the effects of car wheel unbalance on driving safety and comfort. Basic information about types of wheel unbalance, their causes, and effects are included. The test subject was a BMW 3 Series car with rear-wheel drive. A specific unbalance was introduced on the front steered wheels. The vehicle was driven in a straight line on an asphalt road in good condition at speeds between 70 km/h and 140 km/h. During the test runs, acceleration waveforms were recorded from sensors placed on the lower control arm, driver's seat, and steering wheel. The vibration level of the unbalanced wheel increases with the driving speed and with the increase in unbalance. The highest increase in vibration amplitude occurred on the steering wheel at speeds between 100 km/h and 120 km/h. These vibrations have a direct effect on the driver. This is evidenced by negative driver perceptions such as fatigue and driving discomfort. This was also confirmed by the calculated vibration exposure levels. Driving with unbalanced wheels accelerates wear on the tyres, steering, drive, and suspension components of the vehicle.