a 汽车整车及零部件欧阳海彬_radioss application in airbag simulation

1、Altair 2012 Hyperworks 技术大会论 RADIOSS Application in Airbag SimulationHaibin OuYang, Peigang Su, Shuibo Wu(YanFeng KSS (Shanghai) Automotive Safety Systems CO.,Ltd 201315)Abstract: Virtual modeling and simulation are increasingly used to help develop restraint systems, and airbag simulation is the ne

2、cessary steps during airbag research and design progress. This paper introduces RADIOSS application in airbag simulation. The dynamic simulation has been checked with physical test and shows very good correlation, which proves that airbag modeling is reliable and acceptable.Keywords: Tank Test, Airb

3、ag Validation, Drop Tower, RADIOSS1 IntroductionVirtual modeling and simulation are increasingly used to help develop restraint systems and enhance the value of virtual design with simulation are regularly used by system supplier, which is effective in evaluating and optimizing the performance of re

4、straint systems1.The most common airbag simulation method assumes uniform pressure andtemperature everywhereide the airbag. This is a close representative of the airbag afterit is fully inflated and the gas flowide airbag stabilizes. This paper uses uniform pressuremethod to achieve airbag validatio

5、n.2 TheoryAn airbag model in RADIOSS is defined as a monitor volume, the most important parts of airbag definition are gas properties of mass injection and outgoing mass, the latter often includes vent hole outgoing flow and porosity outgoing flow due to fabric material property.2.1 Mass injection3T

6、he amount of mass injected into the airbag needs to be defined with respect to time.The data can be obtained by airbag manufacturer or a tank experiment. A diagram of a classic tank experiment can be seen in Figure 1.Figure 1. Tank Experiment DiagramThe mass versus time curve can be derived from the

7、 pressure curve ifis known:Tm = (1) -1-Altair 2012 Hyperworks 技术大会论 Where, M is the molecular weight of the injected gas, R is the perfect gas constant : = c c, = .The average estimate for temperature of injection is: (2)T = Where, P is the total pressure variation during the experiment. m is the to

8、tal injected mass, which can be derived from the mass of propellant in the pyrotechnic inflator and the chemical reaction.2.2 Outgoing mass determination32.2.1 Isenthalpic modelVenting or the expulsion of gas from the volume, the status is assumed to be isenthalpic. The flow is also assumed to be un

9、shocked, coming from a large reservoir and through a small orifice with effective surface area.The Bernouilli Equation isConservation of enthalpy leads to velocity u at the vent hole.then written as: = + (3) Applying the adiabatic conditions: =(4)Where P is the pressure of gas into the airbag, and i

10、s the density of gas into the airbag. Therefore, the exit velocity is given by: 1 =(5) ()() () () Where =is the averaged density of the gas andis the = ()() ()fraction of massic averages of heat capacities at constant pressure and constant volume. The mass out flow rate is given by: = = (6)2.2.2 Che

11、mkin modelPorosity definition can define the surface for outgoing flow with the following equation: = Where is the density of the gas within the airbag, Funct_ID is the outflow velocity function defined by users.3 Airbag DefinitionThis section deals with airbags model implemented into RADIOSS code.

12、There are several ways and methods to model an airbag with the “Monitored Volume” option, and uniform pressure classical method is commonly used, the keyword and brief descriptionshown below.(7)-2-Altair 2012 Hyperworks 技术大会论 Table 1 Type AIRBAG KeywordLine 2:Isur defines airbag surface.Line 5, 6: D

13、efinition of initial gas properties Line 7: Njet defines the number of injectorside airbagLine 8, 9: Definition of gas injection information, include gas properties, gas flow, temperature and sensor information, which is validated during Tank Test.Line 11: Number of VentLine12-14: Definition of vent

14、 properties include vent area, out flow equation, scale coefficient, which are often validated by verification test. Outgoing massdeterminations of Isenthalpic and Chemkin model have different definition.FVMBAG type airbag of RADIOSS may be used for Out Of Position(OoP) situationwhere the gas flow e

15、ffects must be taken into account.4 RADIOSS ApplicationA specific series of airbag tests are conducted to help validate the modeling of side airbag, Drop tower test is commonly used to correlate airbag characteristics of airbag module in a controlled environment. The following is a successful exampl

16、e that simulated by RADIOSS, the set-up and acceleration result of impactor are shown in Figure 2, the acceleration data has similar output.Figure 3 illustrates the kinematics comparison of the simulation with test result of the model, its kinematics sequency from the side view was captured correspo

17、nding to test view and the comparisons show very good correlation.After airbag component validation, the airbag model can be applied in the airbagrestraint system level simulation to evaluate the occupant performance.-3-1234567891011121314/MONVOL/AIRBAG/1 AIRBAG_SAB#Isur1#Scal_TScal_PScal_SScal_ASca

18、l_D 00000#MuPextTphi 0.10.10132293#Gammaicpaicpbicpci#Njet1#Gammacpacpbcpc#ImassIflowSmassItempStempIsensor #IjetN1N2N30000#Nvent 1#SventAventBvent310.5#TventdPdefdtPdefIvDPFvDP 00000#IportIporPIporAFportFporPFporA000000#IportIporPIporAFportFporPFporA000000Altair 2012 Hyperworks 技术大会论 a Setupb Accel

19、eration resultFigure 2. Setup and Acc resultFigure 3. Kinematics Comparison of Simulation and Test Result5 Conclusion1.The CAE-based airbag simulation is presented in this paper with drop tower test. Both acceleration result and kinematics comparison show that the validated airbag definition is reasonable and accepted.Uniform pressure method of RADIOSS is a quick method and gives rather goodresults for predicting the intera