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EN
Vehicle speeds have increased due to improved road condition. However, this increased speed can result in high energy collisions. Recently, a vehicle occupant in South Korea was killed by a fragment ejected from a concrete median barrier that was struck by a vehicle. The current design impact level of a concrete median barrier (CMB) is SB5-B (270 kJ). However, the impact level of the mentioned accident was estimated as over SB7 (2300 kJ). In the present work, a series of numerical analyses was conducted to reduce the fragmentations of CMB due to impact. Field test were utilized to verify the newly developed model of CMB in impact events. The wire-mesh reinforcements and increment of the cross section were considered as design modifications. In particular, a special device to absorb a significant collision energy has been developed without a dramatic increase in construction cost. This device consists of an empty space around the dowel bars which fix the barrier to the foundation. The empty space allows the dowel bars to deform to absorb collision energy. The performance of the new concrete median barrier equipped with the shock absorbing devices was verified by using carefully designed field test data.
EN
This article presents results of tests of the effect exerted by technical condition of shock absorbers on the braking efficiency of an automotive vehicle. The tests were conducted using Fiat Seicento featuring front shock absorbers which enabled shock-absorbing fluid-level adjustment. The tests comprised measurements conducted on the shock absorbers in four states, i.e. the nominal state with the fluid level at 100%, with shock-absorbing fluid levels of 25%, 50% and 75% as well as with the fluid tank completely empty (0%). Road tests of braking efficiency were conducted on cobbled pavement by means of a decelerometer.
PL
Diagnozowanie stanu technicznego amortyzatorów zabudowanych w zawierzeniach samochodowych jest zagadnieniem trudnym ze względu na to, iż stanowią one elementy złożonego układu mechanicznego zawierającego elementy sprężyste i tłumiące o nieliniowych charakterystykach, które w czasie eksploatacji ulegają degradacji. W referacie przedstawiono wynik badań samochodu z amortyzatorami z zaprogramowanymi usterkami na stanowisku harmonicznym. Obiektem badań był samochód osobowy marki Fiat Seicento. Eksperyment badawczy polegał na pobudzeniu pojazdu do drgań wymuszonych mas nieresorowanych i resorowanych i rejestracji przyśpieszeń drgań tych mas. Badaniom poddano amortyzatory o zaprogramowanych usterkach w postaci ubytku płynu amortyzatorowego od 100% do 35% dla amortyzatorów przednich. Przyspieszenie płyt, wahacza (mas nieresorowanych) i nadwozia (mas resorowanych) rejestrowano za pomocą czujników przyspieszenia. Uzyskane w ten sposób wyniki badań poddano analizie falkowej z wykorzystaniem falki Morleta w środowisku MatLab i w oparciu o te przekształcenia wyznaczono wartości maksymalne amplitud drgań w zależności od stopnia ubytku płynu amortyzatorowego.
EN
Diagnosing the technical condition of shock absorbers installed in automotive suspensions is a difficult issue due to the fact that they are elements of a complex mechanical system containing elastic and damping elements with nonlinear characteristics that degrade during operation. The paper presents the result of testing car with shock absorbers with programmed faults on the harmonic stand. The test object was a Fiat Seicento passenger car. The research experiment consisted in stimulating the vehicle to vibrations of forced masses, unsprung and sprung, and registration of vibration accelerations of these masses. The tests were subjected to shock absorbers with programmed faults in the form of loss of shock absorber fluid from 100% to 35% for rear shock absorbers. The acceleration of plates, swingarm (unsprung masses) and bodywork (sprung masses) were recorded by acceleration sensors. The results obtained in this way were subjected to wavelet analysis using the Morlet wavelet in the MatLab environment and based on these transformations the maximum of vibration amplitudes were determined depending on the degree of loss of the shock absorber fluid.
PL
W artykule przedstawiono wyniki badan stanu technicznego amortyzatorów na stanowisku z harmonicznym wymuszeniem kinematycznym typu Eusama stosowanym na stacjach kontroli pojazdów. Jako parametr eksploatacyjny przyjęto ciśnienie w ogumieniu (założono obniżoną wartość w stosunku do zalecanej wartości nominalnej) oraz określono wpływ tego parametru na wartości uzyskane podczas testów na stanowisku badawczym. Pomiary powtarzano kilkukrotnie zadanych parametrów. Wyniki pomiarów zestawiono tabelarycznie i w formie wykresu i na ich podstawie sformułowano wnioski końcowe.
EN
The article presents the results of the technical state of shock absorbers on the stand with harmonic Eusam type kinematic forcing applied at vehicle inspection stations. As operating parameter, the pressure in the tires was assumed (assumed a reduced value in relation to the recommended nominal value) and the impact of this parameter on the values obtained during testing on the test bench was determined. The measurements were carried out several times. The results are summarized in tabular form and in the form of a graph and based on them final conclusions were formulated.
EN
The model of a mono-tube shock absorber with a bypass is proposed in this paper. It is shown that the application of an additional flow passage (bypass) causes changes to the damping force characteristics when the excitation amplitudes are large. In such cases, the damping force values increase, thereby improving safety of the ride. For small excitation amplitudes, the shock absorber behaves in a similar fashion as shock absorbers without a bypass, ensuring a high comfort level of the ride on roads with smooth surfaces.
PL
Budowa amortyzatorów z biegiem lat bardzo się zmieniała. Wraz z rozwojem technologicznym samochodów pojawiały się coraz nowsze ich modele. Technologie stosowane w amortyzatorach były ulepszane wraz z ich rozwojem, aby sprostać wymogom producentów samochodów. Głównym celem stosowania amortyzatorów w samochodzie jest zapewnienie utrzymania ciągłego kontaktu kół z nawierzchnią drogi poprzez przechwycenie i rozproszenie nadmiaru energii w układzie mechanicznym. W dzisiejszych czasach używanych jest wiele różnych rodzajów amortyzatorów, do których możemy zaliczyć m.in. amortyzatory mechaniczne, hydrauliczne, hydrauliczno-pneumatyczne, magnetyczne, elektromagnetyczne, cierne, powietrzne, elastomerowe, sprężynowe oraz gumowe, których przeznaczenie oraz budowa pozwala na pracę w różnych warunkach atmosferycznych na całym świecie. W pracy dokonano na stacji kontroli pojazdów, badania stanu technicznego amortyzatorów w 30 samochodach poruszających się po polskich drogach. Następnie sprawdzono te wyniki z przepisami prawnymi obowiązującymi w Polsce i na Słowacji.
EN
The construction of shock absorbers has changed over the years. With the technological development of cars, newer and newer models appeared. The technologies used in shock absorbers have been improved along with their development to meet the requirements of car manufacturers. The main purpose of using shock absorbers in the car is to ensure continuous contact of the wheels with the road surface and the comfort of driving by appropriate damping of vibrations captured from the body. Nowadays, many different types of shock absorbers are used, i.e. mechanical, hydraulic and hydraulic-pneumatic and many others which purpose and construction allows them to work in various atmospheric conditions all over the world. For this reason the shock absorbers of 30 cars traveling on Polish roads were examined at the vehicle inspection station. After the trails these results were contrasted with the legal provisions in force in Poland and Slovakia.
7
Content available remote Comparison of computing efficiency of different hydraulic vehicle damper models
EN
This paper deals with comparisons of computing efficiency of 20 damper models with functional and hybrid approaches, which can be used to solve typical problems in vehicle dynamics. Efficiency is evaluated based on model accuracy and computing time. The computed results of different damper models are compared to measurements of an actual car damper. Its damping characteristics were measured on a hydraulic damper test rig with three different excitations.
PL
W artykule porównano efektywność dwudziestu modeli amortyzatorów, funkcjonalnych i hybrydowych, które można stosować przy rozwiązywaniu podstawowych problemów dynamiki pojazdów. Efektywność jest oceniana przez dokładność odwzorowania i czas obliczeń. Odpowiedzi kolejnych modeli amortyzatora porównywano z wynikami badań rzeczywistego amortyzatora samochodowego na stanowisku ze wzbudnikiem.
EN
The paper presents a quarter car model two degrees of freedom (wheel and body), with vertical guiding system, the model being equipped with suspension stroke limiters and with excitation by wheel and/ or by body. The model reproduces elastic and damping characteristics of wheel and of rebound and compression stopper bumpers, the spring elastic characteristic and the shock absorber damping characteristic on rebound and compression, function piston speed. The road profile is generated with simple or summation of harmonic functions, or by reproducing real roads. The forces acting on full vehicle body e.g. aerodynamic and inertial forces are reproduced in the proposed quarter model by vertical forces reduced to the analysed quarter part. Thus, the model can be used for evaluation the vertical and horizontal stability at acceleration, deceleration, pitch and roll, at aerial forces, the body ground clearance and the comfort. The model can evaluate the influence of the damping and elastic characteristics of suspension and wheel, of the static position, of the vehicle load state, of the road profile and of the external forces, to the vehicle behaviour
PL
W danej publikacji został opisany model matematyczny zaworu talerzowego jednorurowego amortyzatora, wyprowadzenia którego zastosowano metodę sił. Metoda ta wyraża związki pomiędzy przemieszczeniami i siłami działającymi na elementy amortyzatora. Stosowanie metody sił w praktycznej sferze modyfikacji amortyzatorów samochodowych pozwala efektywnie analizować wpływ różnych parametrów, w tym ilość, wzajemne położenie i właściwości materiałów talerzy zaworu, na generowaną amortyzatorem wielkość siły tłumienia. Tłumienie, które generuje amortyzator, wywiera znaczący wpływ na komfort jazdy samochodem oraz jego dynamikę. W publikacji również został stworzony kompletny model jednorurowego amortyzatora. Walidacja modelu matematycznego oraz możliwość zastosowania jego w praktyce zostały ocenione na podstawie eksperymentalnych pomiarów charakterystyk amortyzatorów na specjalnym stanowisku.
EN
In this paper, a mathematical model of a monotube shock absorber’s shim valve, which is developed by applying the force (flexibility) method, is described. This method expresses the relationship between displacements and the forces existing in the shock absorber structure. An application of the force method in the field of practical modification of vehicle shock absorbers enables to effectively analyse the influence of a wide range of parameters, including the number of shims in the valve, their disposition and the properties of the material on the level of the damping force. The damping of the shock absorber considerably impacts comfort and road holding characteristics of the vehicle. In addition, a whole model of a monotube shock absorber is designed in this paper. The validation and practical application of the mathematical model were evaluated by carrying out experimental measuring of the characteristics of the shock absorber using a special stand.
EN
The article provides a discussion on oscillatory methods used for technical condition assessment of shock absorbers in automotive vehicles, focusing primarily on free vibration methods. It comments on results of simulation studies of a simple two-mass model conducted by application of a pulse input function. Results of experimental tests have also been provided in the paper. The foregoing tests consisted in recording of accelerations of the body of an automotive vehicle equipped with a shock absorber enabling simulation of shock absorbing liquid leakage. The follow-up analyses were conducted to establish the decrement of damping as well as the damping coefficient.
PL
W artykule opisano metody drganiowe stosowane w ocenie stanu technicznego zawieszenia pojazdu samochodowego ze szczególnym uwzględnieniem metody drgań swobodnych. Przedstawiono wyniki badań symulacyjnych dla prostego modelu dwumasowego przy wykorzystaniu wymuszenia impulsowego. Zaprezentowano również wyniki badań eksperymentalnych. Badania te polegały na rejestracji przyśpieszeń drgań nadwozia pojazdu samochodowego wyposażonego w amortyzator umożliwiający zasymulowanie wycieku płynu amortyzatorowego. W ramach analiz wyznaczono dekrement tłumienia oraz współczynnik tłumienia.
EN
This paper explains the role of magnetorheological fluids and elastomers in today’s world. A review of applications of magnetorheological fluids and elastomers in devices and machines is presented. Magnetorheological fluids and elastomers belong to the smart materials family. Properties of magnetorheological fluids and elastomers can be controlled by a magnetic field. Compared with magnetorheological fluids, magnetorheological elastomers overcome the problems accompanying applications of MR fluids, such as sedimentation, sealing issues and environmental contamination. Magnetorheological fluids and elastomers, due to their ability of dampening vibrations in the presence of a controlled magnetic field, have great potential present and future applications in transport. Magnetorheological fluids are used e.g. dampers, shock absorbers, clutches and brakes. Magnetorheological dampers and magnetorheological shock absorbers are applied e.g. in damping control, in the operation of buildings and bridges, as well as in damping of high-tension wires. In the automotive industry, new solutions involving magnetorheological elastomer are increasingly patented e.g. adaptive system of energy absorption, system of magnetically dissociable [hooks/detents/grips], an vibration reduction system of the car’s drive shaft. The application of magnetorheological elastomer in the aviation structure is presented as well.
EN
Landing gear as one of the most crucial systems ensuring safe take-off and landing must be rigorously tested before first flight of each newborn aeroplane. In the static and dynamic tests strength, functionality and energy absorption capability of landing gear components (wheel, brake, shock absorber, support structure and retraction system) are verified. One of the most important is an energy absorption dynamic test. During drop, test campaign a landing gear damping system is not only verified but also optimized by changing parameters like: damping orifice diameter, geometry of gas and oil chambers and shock absorber and tire inflation pressures. This process often takes substantial amount of time because of influence of the mentioned parameters on landing gear energy absorption efficiency. Other factors like landing configuration spin up and spring back effects generated during wheel contact with the ground [1] also have to be considered in the energy absorption optimization process. The paper describes the landing gear drop test campaign and main challenges, which have to be overcome to achieve optimal dynamic characteristics of the system. The tested object was the main landing gear of the 1400 kg General Aviation aircraft certified in accordance with EASA CS-23 regulations. The drop test campaign was carried out in Warsaw Institute of Aviation Landing Gear Laboratory.
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.
EN
Hydraulic shock absorbers are mechanical devices responsible of vibration damping. Although a high level of development and tuning has been carried on, in order to ensure high performance standards in almost every situation, some dynamic phenomenon affecting internal fluid may reduce the damping capacity. In hydraulic shock absorbers, the energy is dissipated forcing the internal fluid through calibrated orifices; this energy is converted in heat and dispersed outwards from the external walls. Hydraulic fluid has therefore a fundamental role for the proper functioning of the overall device, and the most important variations of its chemical-physical properties have to be considered. One of the most dangerous phenomena involving the internal fluid is cavitation, which could affect performances and generate structural damages of the internal components of the damper. The aim of this work is to diagnose the phenomenon of cavitation using experimental data from a prototype of monotube shock absorber equipped with transparent walls and developed for research purposes. The identification of force and displacement parameters is carried out through experimental tests on the prototype, which is a totally adjustable device equipped with pressure and temperature transducers for every chamber. The optical access provided from the transparent wall allows to collect images from a high-speed camera, which could be related to the signals coming from the transducers. This approach is valuable for analyzing the occurrence and the time development of dynamic phenomena of cavitation of the flow or the motion of the main valve blades. Finally, the acquisition of the optical images, coupled with evidences from experimental data, allows to characterize the dynamic events of cavitation, from his onset.
15
Content available remote Ocena możliwości zwiększenia wiarygodności i końcowych wyników testu EUSAMA
PL
Artykuł dotyczy diagnozowania amortyzatorów metodą EUSAMA, ze szczególnym uwzględnieniem sił tarcia w zawieszeniu pojazdu. Przedstawione są tutaj wyniki pomiarów tego rodzaju oporów w dwunastu samochodach osobowych. Zasadniczy fragment pracy poświęcony jest symulacjom komputerowym testu EUSAMA z wykorzystaniem nieliniowego modelu "ćwiartki" pojazdu. Omówiona jest struktura ogólna tego oryginalnego odwzorowania oraz jego formalny opis. Obliczenia numeryczne poprzedza udana weryfikacja eksperymentalna autorskiego modelu. Ocena metody EUSAMA dokonywana jest przede wszystkim na podstawie badań symulacyjnych. Analizowane są końcowe wyniki prób przy zmianach tłumienia wiskotycznego oraz tarcia suchego w zawieszeniu samochodu. Rezultaty badań symulacyjnych poddane są także częściowej weryfikacji eksperymentalnej, która i w tym przypadku wypada pozytywnie. Końcowy fragment artykułu ma aspekt praktyczny i zawiera propozycję korekcji wyniku próby EUSAMA ze względu na zakłócający wpływ tarcia suchego w zawieszeniu samochodu.
EN
The article focuses on diagnosing the shock absorbers using the EUSAMA method, with a particular emphasis on the friction forces in the vehicle suspension. The measurement results of such resistances in twelve passenger cars are shown here. The main fragment of the paper is devoted to the computer simulation of EUSAMA test using non-linear “quarter-car” model. Overall structure of the original model and the formal description are discussed. The numerical computations are preceded by a successful experimental verification of the author’s model. The EUSAMA method assessment is made primarily on the basis of simulation studies. Final results of tests in view of the changing viscous damping and dry friction in the car suspension are analysed. The simulation tests results are also subject to partial experimental verification which also in this case has a favourable outcome. The final part of this dissertation has a practical aspect and contains a proposal to correct the EUSAMA test result due to the distorting effects of dry friction in the car suspension.
EN
The paper presents comparison of damping characteristics determined for new hydraulic shock absorbers. The damping characteristics were determined on indicator test stand for six new front shock absorbers of the same type. On the basis of these results was made the statistical analysis as well as the comparison of the received characteristics.
PL
W ramach referatu przedstawiono porównanie charakterystyk tłumienia wyznaczonych dla nowych amortyzatorów hydraulicznych. Charakterystyki tłumienia wyznaczono na stanowisku indykatorowym dla sześciu przednich nowych amortyzatorów tego samego typu. Na podstawie otrzymanych wyników przeprowadzono analizę statystyczną oraz przeprowadzono porównanie jakościowe otrzymanych charakterystyk.
EN
The paper offers analysis of the effect of different types of tyres and tyre inflation pressure on the measurements of shock-absorber efficiency. Testing was carried out in accordance with the EUSAMA method for testing shock-absorbers' efficiency using test stand "Safeline 400/800". Literature review presents a survey of the most up-to-date studies regarding the topic under consideration in this particular paper. For the purpose of research, heavily used summer tyres and slightly worn winter tyres were selected. The effect of air pressure in tyres (varied in range of [1.6 ... 3.0] bar) on the variation of shock-absorber efficiency has been assessed. The correlation between vibration inducing platform and vertical acceleration of the wheel has been examined. Findings obtained through research are depicted graphically. Results about shock absorbers efficiency variation because of the tyres types and pressure and wheel's replication of the vertical acceleration of the vibrating test plate are summarized and conclusions are drawn at the end.
PL
W artykule przedstawiono wyniki badań drgań pojazdu samochodowego z zabudowanymi amortyzatorami o zidentyfikowanym stanie technicznym. Podczas badań rejestrowano przyspieszenia drgań pionowych w wybranych punktach konstrukcyjnych pojazdu, między innymi na płycie podłogowej w miejscach przylegania stóp pasażerów do podłogi. W ramach analizy wyników wyznaczono miary amplitudowe w wyznaczonych pasmach częstotliwościowych. Porównano wartości tych miar w zależności od stopnia wypełnienia amortyzatorów czynnikiem roboczym. Pozwala to na wstępną ocenę wpływu stanu technicznego amortyzatora na poziom i dynamikę ekspozycji drgań ogólnych na człowieka.
EN
The paper presents the results of research on vehicle vibration with built-in shock absorbers identified technical state. The vertical vibration acceleration were measured at selected points of the vehicle construction, including on the floor in the foot passengers adhere to the floor. The amplitude measures were calculated in chosen frequency bands. The comparison of these measures, depending on the percent of filling of working fluid of shock absorber were presented. This allows for the pre-evaluation of the influence of the technical state of shock absorber on the level and dynamics of whole-body vibration exposure on humans.
EN
The weight decreasing of small cars can be very effective by using of lightweight materials. Movable masses of such cars like suspension arms, wheel rims, drive shafts can be made of magnesium alloy, brake discs can be made of aluminum alloy. Such masses can mate with electromagnetic shock absorbers with possibility of recuperation for energy of chassis vibrations, changing it into the useful electric power. Main parts of the shock absorber are the cylinder with the set of coils and the rod with a set of permanent magnets. Cylinder can be made of magnesium alloy. Coils winding has been connected to electric wires placed inside light spring. Three-phase current generated in the set of coils can be supplied through the controlled rectifier into battery. Dimensions of electromagnetic shock absorber have been close to those of hydraulic shock absorber, so it can be used in the typical chassis of automobile. The scheme of the shock absorber has been shown in the article. The elaborated model of road roughness and of moving masses for small car, connected to electromagnetic shock absorber has been shown in the article. It has been analysed the values of dynamic parameters during operation of electromagnetic shock absorber with movable masses of small car driven in different road conditions. Results of such analysis have been presented in the article. The aim of the study has been to estimate and to compare the amount of recuperated energy by the electromagnetic shock absorber – rectifier – battery assembly for the cases of car movable masses made of steel and for the one of lightweight materials
EN
A nonlinear boundary value problem of two degrees-of-freedom (DOF) untuned vibration damper systems using nonlinear springs and dampers has been numerically studied. As far as untuned damper is concerned, sixteen different combinations of linear and nonlinear springs and dampers have been comprehensively analyzed taking into account transient terms. For different cases, a comparative study is made for response versus time for different spring and damper types at three important frequency ratios: one at r = 1, one at r > 1 and one at r <1. The response of the system is changed because of the spring and damper nonlinearities; the change is different for different cases. Accordingly, an initially stable absorber may become unstable with time and vice versa. The analysis also shows that higher nonlinearity terms make the system more unstable. Numerical simulation includes transient vibrations. Although problems are much more complicated compared to those for a tuned absorber, a comparison of the results generated by the present numerical scheme with the exact one shows quite a reasonable agreement.
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