| Along with the improving of the automobile capability, the function of brakesystem for the security of automobile becomes more and more important. Thevibration of the brake system during braking, not only affect the comfort but alsoinfluence the security of the automobile. The unequally wear of the frictionmaterial, is also an important factor for the declination of the braking ability.When performing the analysis, synthesis or prediction, the dynamiccharacteristic of the braking system is needed .But maybe, the actual system be notcompleted or can not be tested through the examination because of the security orthe economy. So the system should be tested by simulation. During the simulation,the rigid body system can only reflect the whole braking capability, but can notreflect the friction or the deformation of each part concretely. So if we want to lookinto the influence of the deformation and the friction of some position, we must setup the flexible multi-body model.This paper mainly concerning modeling of flexible multi-body of automobilebrake system and the contribute of relative parameter to the unequally wear,abnormal wearing of the friction material during the braking process, expounds thetheory of the modeling the flexible multi-body of brake system utilizing the FEAtechnology and the multi-body dynamic technology, expounds the applicationmethod and the mechanics model, and provides a feasible means for deeply study.The flexible multi-body model of brake system is set up through the followingsteps : found the FEA model of the components of the brake system in Hyperworks,analyze the FEA mode ,then convert the FEA model to the neutral file for Adams(including the mode conversion matrix ,mode stiffness matrix and the modefrequency), then import the neutral file into the Adams, modeling the flexiblemulti-body model of the brake system in Adams.The flexible multi-body model of the brake system not only concerns theflexibility deformation of the components of the brake system, but also concernsthe influence of moment of inertia of the rotating components of the automobile.Add the equivalent moment inertia to the brake disc, if not the simulation will bebadly distorted.Aiming at the brake system of MPV ,the paper quest for the key technic formodeling the flexible multi-body: partition the model to found the FEA model inthe Hyperworks ,analyze the FEA mode in the Optistruct, the interface of FEAsoftware and dynamic software Adams, and the modeling the flexible multi-body inAdams. In them, the emphases are modeling the FEA model and the difficulty pointis to set up the contact between the brake disc and the friction plate, in order tosimulate the friction between them. Then simulate the braking process utilizing theflexible multi-body model, and as the conclusion, we get the variety of the friction,deformation, velocity and the acceleration along with time.Via the simulation, we can get the following conclusions:1. Via the dynamics analysis and calculation, the model accords with theactual process of braking.2. The friction will increase with the dynamic friction coefficient, but highdynamic friction coefficient will cause the abnormal vibration and worsen thestability of the brake system, even the stability of the whole automobile. On thecontrary, the lower the dynamic friction coefficient is, the lower the brakingcapability is. So when selecting brake shoe, the dynamic friction coefficient mustfulfill the request of both brake capability and stability.3. The fiddling error caused during the manufacturing and the assembling ,may cause the violence fluctuate of the friction during the braking process4.Because of the limitation of the time and my ability ,the paper ignores theincreasing process of the pressure in brake cylinder from zero to 10MPa, and thedecreasing process of the pressure in brake cylinder when loosen the braking pedal.Furthermore, it's not sufficient to evaluate brake capability only by brake systemmodels, but also models of whole vehicle and the effect of suspension and steeringsystem on brake capability in addition.5. Because of the limitation of the hardware, the curve of the friction fluctuateviolently, if want to smooth the curve, we must increase the number of the Vforceand the marker. It is a challenge for the hardware.The paper only perform the primary analysis of the dynamics characteristic ofthe brake system, we can perform more analysis on this basic, for example thethermodynamics analysis. Further more, to evaluate the brake system, the brakingprocess under multi-operating mode is needed, and surface-roughness of the road isalso an important factor.The modeling of flexible multi-body can effectively analyze and solvecomplex three-dimensional dynamic subjects of brake system and evaluate brakecapability. Further research and study on this basis will result in a convenient andeffective solution that can be much helpful to study, design and development of thebrake system.
|
PDF Full Text Request