Numerical Simulation of Shock Absorbers Heat Load for Semi-Active Vehicle Suspension System

Dynamic simulation, based on modelling, has a signtficant role during to the process of vehicle development. It is especially important in the first design stages, when relevant parameters are to be defined. Shock absorber, as an executive part of a semi-active suspension system, is exposed to thermal loads which can lead to its damage and degradation of characteristics. Therefore, this paper attempts to analyse a conversion of mechanical work into heat energy by use of a method of dynamic simulation. The issue of heat dissipation from the shock absorber has not been taken into consideration

Contribution to the research of oscillatory loads of sprung and unsprung masses in order to create conditions for laboratory tests of heavy motor vehicles

Introduction/purpose: Motor vehicles are complex dynamic systems due to spatial displacements, changes in the characteristics of components during their lifetime, a large number of influences and disturbances, the appearance of backlash, friction, hysteresis, etc. The aforementioned dynamic phenomena, especially vibrations, cause driver and passenger fatigue, reduce the lifetime of the vehicle and its systems, etc. Methods: In general, the movement of vehicles is carried out on uneven roads and curvilinear paths in the road. Not only do oscillatory movements cause material fatigue of vehicle parts, but they also have a negative effect on people's health. That is why special attention must be paid to the coordination of the mutual movement of the subsystems, and in particular, the vehicle suspension system, even at the stage of the motor vehicle design. For these purposes, theoretical, experimental or combined methods can be used. Therefore, it is very useful to have the experimental results of the oscillations of the vehicle subsystem in operating conditions, so the aim of this work was to use the movement of the 4x4 drive FAP 1118 vehicle in operating conditions (due to higher speeds - in road conditions) to define the conditions for testing oscillatory loads in laboratory conditions. Results:This is made possible by registering and identifying statistical parameters of registered quantities. Conclusion: Based on the measured data, the research can be programmed on shakers in laboratory conditions, and, at the same time, the size to be reproduced can be chosen as well

Contribution to the analysis of the influence of parameters of elasto-damping elements to the vehicle ride comfort

During development of motor vehicles, a significant role has a dynamic simulation, which is based on the modeling. Role modeling is very important in the early stages of design, during definition of the vehicles main parameters. Literature sources provide complete responses to the influence of the forces in springs, shock absorbers and tires on the vehicle oscillatory comfort, but hardly anyone engaged in analysis of parameters of the models of elasto-damping elements on the oscillations of the vehicle. This paper will attempt to be made, on the basis of the adopted models of springs, shock absorbers and tires, perform analysis of the influence of parameters on the oscillations of the vehicle. For that purpose they used so-called sensitivity functions

A contribution to the modeling of truck powertrain vibration

Under the effect of excitation of road roughness, powertrain, as well as of the conditions of movement (acceleration, braking, curvilinear movement) the vehicles masses perform a complex spatial vibrations. The negative effects of these oscillatory movement or dynamic loads caused by it and transmitted to the supporting system of the vehicle can be reduced by proper selection of the characteristics and position of the mounting system of the powertrain.For the analysis of these effects can be used a theoretical, experimental and combined methods. In this article, the research was carried out with use of the theoretical methods by using simplified mechanical model of the powertrain, wherein the observed vibration of the truck produced in FAP

Contribution to research of the influence of axle oblique alignment on motor vehicle fuel consumption

Fuel consumption is of great importance for a vehicle performance evaluation, starting from the development design stage. Later, in service conditions, considerable efforts are made to keep consumption parameters within acceptable limits. Periodical vehicle servicing is mostly focused on the control of engine parameters, although there are some other influential parameters that may produce a considerable impact on fuel consumption

A contribution to the investigation of the heat load of shock absorbers of semi-active suspensions in motor vehicles

Dynamic simulation, based on modeling, has a significant role during the process of vehicle development. It is especially important in the first stages of vehicle design, when relevant vehicle parameters are to be defined. Shock absorbers as executive parts of vehicle semi-active suspension systems suffer thermal loads, which may result in damage and degradation of ther characteristics. Therefore,this paper shows an attempt to analyze converting of mechanical work into heat by using the dynamic simulation method. Introduction Shock absorbers are integral elements of semi-active suspension systems for vehicles (hereinafter SASS). They directly affect the active vehicle safety. The role of shock absorbers is to absorb mechanical vibrations transferred from the road and to ensure the safety of passengers in a vehicle. The kinetic energy of vehicle vibrations transforms into mechanical work or heat in shock absorbers. In practice, in the first stage of vehicle development, the shock absorber parameters are chosen from the condition of damping vibrations of vehicles, but their thermal shock loads should be also taken into account. Motor vehicles have complex dynamic characteristics manifested by spatial movement, parameters change during operation, a number of disturbing influences, backlash, friction, hysteresis, etc. The above-mentioned dynamic phenomena, especially vibration, lead to fatigue of driver and users, reduce the life of the vehicle and its systems, etc. The main objective of the system is to reduce the reliance of the above-mentioned negative effects, improving the vehicle behavior on the road and allow the exploitation of vehicles in a wide range of service conditions. Classical systems cannot satisfiy these conditions, so there was a need to introduce new suspension systems with controlled characteristics (briefly called "semi-active", or "active" systems). Oscillatory model of vehicle The differential equations of vibratory motion of the given vehicle model  have been written using the "NEWEUL." software package. The data input has been done in accordance with the program requirements, and 24 coordinate systems (including inertial-OI1I2I3 global coordinate system) have been used to define the dynamic vehicle model with seven degrees of freedom. Thermal load on the shock absorbers of the semi-active suspension system Due to the relative motion between sprunged and unsprunged masses, mechanical work in the absorbers is equivalent to the amount of heat Q, J. As the heat flux is of a random size, it was assessed as appropriate to calculate the average power (flux) for each buffer separately, and the data are given in Table 1 Table 1 Medium heat flux during a movement of  20, s Medium flux, W Front left absorber Front right absorber Rear left absorber Rear right absorber Speed 30,m/s, Mass 100% 2.330434E-006   5.569178E-006 5.358273E-006 2.944404E-006 Speed  5, m/s Mass 100% 2.435122E-006   5.673833E-006 5.477176E-006 2.968751E-006 Mass 75%, Speed 5, m/s 2.431798E-006   4.518553E-006 4.263119E-006 2.748116E-006 For  illustration, Fig. 1 shows the work converted to heat amount in the  shock absorbers of the semi-active suspension system, for a vehicle speed of  5 m/s. The analysis of the heat amount data for a speed of 5 and 30, m/s,for an illustrative example of a speed of 5, m / s , given in Fig. 1 shows that the amount of heat production increases with the covered distance (time). If the vehicle speed increases, the amount of heat decreases. The example in  Fig. 2 shows the effect of the vehicle load on the heat amount generated in the semi-active suspension system absorbers. Namely, the figure shows mechanical work (converted into heat) in the shock absorbers of a partially loaded vehicle (75%) while moving at a speed of 5, m / s. It can be determined that the reduced load on a vehicle leads to reduced thermal shock loading of vehicles, which is in accordance with heat flux.ConclusionBased on the study,the following can be concluded: Models of vehicles with semi-active suspension systems can be used for calculating thermal load on the suspension,speed increase during vehicle movement along the path of identical properties, decreases the production of heat in shock absorbers, andincrease in load of the vehicle leads to the increase in the production of heat in shock absorbers.<br /

A contribution to research of the influence of steering trapeze on bus steered wheels shimmy

Steered wheels shimmy is a harmful phenomenon in the steering system ofthe vehicle. It causes driver's fatigue and fatigue of the elements of steering system, increased tire wear etc. In practice, efforts are being made to reduce or eliminate the occurrence of this effect, and the buses are sometimes equipped with shock absorbers in the steering trapeze. In this paper an attempt is made to analyze the influence of shock absorber in the steering trapeze on the steered wheels shimmy of a bus. Analysis showed that shock absorbers significantly affect the reduction of steered wheels shimmy

A contribution to research of degradation of characteristics of vibration parameters on vibration aspect of vehicle comfort

Dynamic simulation, based on modeling, has a significant role in vehicle development, especially in the early stages of design process, when relevant parameters are being defined. In praxis it is usually assumed that vibration parameters are unchangeable, what is basically wrong. All researches indicate that vibration parameters degrade in time of vehicle service, consequently leading to a variation of its dynamic characteristics. This paper, based on preliminary research results, attempts to point out the necessity of taking into consideration this variation in the earliest phases of vehicle design by its implementation in the vehicle simulation model

A contribution to investigation of the damping forces in classical shock absorbers

Shock absorbers are fundamental part of the vehicle suspension. Suspensions are needed to guarantee vehicle handling, passenger riding comfort and braking. Bearing that in mind, the tire-road contact forces need to be as stable as possible. Each wheel should always remain in contact with the ground. Comfort means that vibrations, induced by road profile during riding, are of a minimal nuisance to the passengers. When designing a new vehicle, a lot of development effort is focused on the optimal choice of the suspension parameters, stiffness (including stabilisers) and damping. In this paper will be presented the results of influence of the cinematic parameters (relative: displacement, velocity and acceleration) to the force that occurs in the shock absorber. The experimental results are obtained by testing of three types of classic shock absorbers from the production of Magnety-Marelli - Turin, under the influence of random excitation. To determine the level of influence of individual cinematic parameters, the theory of the partial coherence functions was used

Contribution to research of thermal loads in commercial vehicles powertrain mounts / Приложение к исследованию тепловой нагрузкиопоры силового привода грузового автомобиля / Prilog istraživanju toplotnih opterećenja oslonaca pogonske grupe teretnog motornog vozila

Due to the effects of excitations of road micro-roughness and the powertrain as well as due to the conditions of movement (acceleration, braking, curvilinear movement), the weights of commercial vehicles perform complex spatial oscillations. The negative impact of these movements or dynamic loads caused by them and transmitted to the supporting system of the vehicle can be reduced by a proper selection of the position and characteristics of the powertrain mounts. Elastic and damping forces in mounts perform mechanical work that turns into heat energy. Theoretical, experimental and combined methods can be used for the analysis of thermal loads of mounts. In this paper, research was carried out with theoretical methods using a mechanical model of the powertrain. Vibrations were observed on a freight vehicle powertrain of FAP 1314 middle-class vehicles. Bearing in mind the presence of classical (rubbermetal) and hydraulic mounts in modern commercial vehicles, the authors analysed the thermal loads of the mentioned vehicle type using a mathematical model. / Под действием возбуждений, возникающих в результате микрошероховатости дорог, трансмиссии, а также условий движения (ускорение, торможение, криволинейное движение), массы коммерческих транспортных средств совершают сложные колебательные движения. Негативное воздействие этих перемещений, а соответственно и динамических нагрузок на опорную систему транспортного средства, может быть снижено при соответствующем выборе положения и характеристик опоры силового агрегата. Как показывает практика, при согласовании характеристик опоры силового привода чаще всего учитываются такие факторы, как минимальный шум и вибрации транспортного средства, в то время как проблеме тепловых нагрузок, которым они подвергаются при эксплуатации, практически не уделяется никакого внимания. Необходимо учитывать тот факт, что повышенные тепловые нагрузки неизбежно приводят к повреждению опоры и ухудшению ее характеристик. Следует отметить, что силы упруго-демпферных опор выполняют механическую работу, преобразуя механическую энергию в тепловую. Анализ тепловых нагрузок на опоры может быть выполнен с помощью теоретических, экспериментальных и комбинированных методов. В настоящей работе представлены результаты исследования, полученные на основании теоретических методов и упрощенной механической модели трансмиссии. В ходе исследования испытаны вибрации силового привода грузового автомобиля среднего класса производственной линейки ФАП 1314. С учетом того, что современные грузовые автомобили оснащены как стандартными механическими, так и гидравлическими опорами был проведен анализ тепловой нагрузки с помощью математического моделирования, применяемого в обоих случаях. Исследования проведены с целью определения соотношения тепловой нагрузки стандартных механических и гидравлических опор с помощью математических моделей, таким образом, полученные результаты могут считаться ориентировочными, что является важным фактором на этапе проектирования коммерческого автотранспортного средства. Анализ показал, что количество тепла, вырабатываемого при применении гидравлических опор, значительно выше, чем в случае применения стандартных механических опор. Кроме того, расчет парциальных функций когерентности теплового потока показал, что их значения находятся в диапазоне от 0,216 до 1, что указывает на взаимозависимость между входными значениями и тепловым потоком. Кроме того, доказано, что инерционная сила и крутящий момент оказывают большее влияние на тепловую нагрузку силовых агрегатов, чемвибрационное возбуждение рамы транспортного средства. / Pod dejstvom pobuda od mikroneravnina puteva, pogonske grupe, kao i od uslova kretanja (ubrzavanje, kočenje, krivolinijsko kretanje) mase teretnih vozila vrše složena prostorna oscilatorna kretanja. Negativan uticaj tih kretanja, odnosno dinamičkih opterećenja koje ona izazivaju i prenose na noseći sistem vozila, može se smanjiti pravilnim izborom položaja i karakteristika oslonaca pogonske grupe. U praksi se usaglašavanje karakteristika oslonaca pogonske grupe, najčešće, vrši iz uslova minimalne buke i vibracija vozila, pri čemu se, uglavnom, zanemaruju toplotna opterećenja kojima su oni izloženi u eksploataciji, a zna se da ona neminovno dovode do oštećenja samih oslonaca i narušavanja njihovih karakteristika. Treba napomenuti da elasto-prigušne sile u osloncima vrše mehanički rad koji se pretvara u toplotnu energiju. Analiza toplotnih opterećenja oslonaca može se vršiti korišćenjem teoretskih, eksperimentalnih i kombinovanih metoda. U ovom radu istraživanja su vršena primenom teorijskih metoda uz korišćenje uprošćenog mehaničkog modela pogonske grupe. Pri tome su posmatrane vibracije pogonske grupe teretnog motornog vozila srednje klase iz proizvodnog programa FAP 1314. Imajući u vidu zastupljenost klasičnih (gumeno-metalnih) i hidrauličkih oslonaca pogonske grupe kod savremenih teretnih motornih vozila, u radu su izvršene analize toplotnih opterećenja pomenutog vozila, uz korišćenje matematičkog modela. Realizovana istraživanja imala su za cilj da se utvrdi odnos toplotnih opterećenja klasičnih i hidrauličkih oslonaca, uz pomoć modela, pa se dobijeni rezultati mogu usvojiti kao orijentacioni, što je neophodno u fazi izrade idejnog projekta teretnog motornog vozila. Analiza je pokazala da je razvijena količina toplote kod hidrauličkih oslonaca višestruko veća nego u slučaju korišćenja klasičnih oslonaca. Pored toga, izračunate parcijalne funkcije koherenci toplotnog fluksa su pokazale da su njihove vrednosti u intervalu 0,216 do 1, što ukazuje na to da postoji veza između ulaznih veličina i toplotnog fluksa. Pri tome, veći uticaj na toplotna opterećenja oslonaca pogonske grupe imaju inercijalna sila i obrtni moment motora nego oscilatorne pobude okvira vozila