Analysis Of Dynamic Model And Structure Stiffness In Vehicle Side Impact

Side impact has already become the most important accident pattern inChina. Good impact resistance of structure is the precondition of thepassenger protection. Adequate matching of stiffness among the different sidestructures could obtain a better effect on occupant safety. This paper focusedon the analysis of dynamic model and structure stiffness for vehicle sideimpact by means of theoretical computing, finite element simulation andexperimental research.The frontal impact process between MDB and rigid wall was simplifiedto single-lumped-mass dynamic model, in which the stiffness character ofspring-damper element was confirmed. The side impact process between MDBand vehicle was simplified to double-lumped-mass dynamic model, in whichthe stiffness character of spring-damper element was verified through thecontract of simulated velocity curves and measured velocity curves. On thatbasis, four-lumped-mass dynamic model for side impact was established,which fitted well with the actual velocity curves. This dynamic model wasmore convenient in calculating and the stiffness parameters were easy toobtain. By factor analysis on stiffness parameters, it was found that throughproper structure improvement, which included increasing the thickness of trimto0.28m, increasing the contact stiffness between front door and car body to120kN/m, and reducing the trim stiffness to9kN/m, pelvic peak accelerationof dummy could reduced from50.5g to24.9g.Vehicle structure stiffness was computed obtained from FE simulation. Itwas found that average stiffness was close to the stiffness in dynamic modeland piecewise linear stiffness could well fit for simulated stiffness curves.The time domain responses of force distributions on impact face which coulddistinguish the stiff parts in the area. Then the obtaining methods of timedomain responses of force distributions which could be realized in actual measurement were discussed. The result showed that when the forcemeasurements were equipped on the face of MDB without honeycomb,obtained time domain responses of force distributions were most similar tothat on impact face.In order to realize measurement of force distributions in side impact,load cell element was designed and the corresponding drop impact tests fordifferent materials were conducted. Then the stiffness computed by the loadcell was compared with that obtained by the acceleration. The result showedthat the load cell can reliably acquire the impact force in the area of125mm×125mm and the stiffness of specimen can be easily computed from thecollected data of load cell and accelerometer. Under specific working modes,the stiffness could be estimated by the acceleration data while the stiffnesscomputed by load cell data could be precise.