| As one of the important parts of the automobile, the automotive windshield not onlyworks as shelter and provides a good sight for the driver, but also functions as one of theimportant automotive safety components. Therefore, the investigation of the impactfracture mechanics on the windshield is of vital importance to the design of automotivepassive safety involving the pedestrian protection. However, due to the characteristics ofbrittle fracture of windshield, there has not yet been a methodology or simulation softwarethat is widely accepted in the automotive industry. Based on the experimentalinvestigations of the mechanical properties and the research on the material model of PVBfilm, this paper presents a new finite element model for the windshield glass and applies itto the automotive passive safety design using LS-DYNA. On the other hand, this paperinvestigates the impact fracture mechanics of laminated glass by using the combinedDE/FE method and CDFP software which are developed in our research group. Thesimulation results calculated by using CDFP are in good agreements with the experimentoutcomes, which shows that the combined DE/FE method has promising applications onthe impact fracture analysis of windshield glass. The main contents are as follows:First, the material properties of PVB interlayer material were studied intensively byexperiments. In view of the rate-dependent property of the PVB film, a tensile testingapparatus with variable strain rates for the PVB material was developed. Through thistensile testing apparatus, different stress-strain relationships of PVB material underdifferent strain rates were obtained. According to the experimental data, it is found that theMooney-Rivlin model at a strain rate can better describe the large deformation behavior s ofPVB material. During the impact damage process of laminated glass, based on theexperimental phenomenon that at the same time, the strain rates of different regions on thewindshield are different and at different time strain rates of same region on the windshieldchange, a correction Johnson-Cook model was obtained that can effectively describe theproperties of PVB material at different strain rates. Second, although the finite element method is difficult to effectively describe theimpact damage phenomenon of windshield, based on the needs of automotive passivesafety design, researchers are still using the finite element analysis software to analyze theimpact fracture behaviors of laminated glass by establishing the finite model of laminatedglass and using the element deletion method. This paper presents a new modeling method.In this method the PVB laminated glass is modeled by using a layer of shell elements and alayer of solid elements. From the comparisons of the simulation and experimental results,despite the failure mode has a big difference between the simulation and experiment, themodeling method can get a better consistency with the impact acceleration of experimentby compared with other finite element models of laminated glass. The impact accelerationis important for the evaluation of pedestrian protection performance.Finally, the combined DE/FE method and CDFP software were developed toinvestigate and simulate the impact damage phenomena of automotive windshield by ourresearch group. Because the discrete element method is computational inefficient, it stillneed a long time for the engineering applications of DEM. To confirm the feasibility of thecombined DE/FE method for simulating impact damage phenomenon of automotivewindshield, impact damage experiments with a small laminated glass specimen weredesigned. The glass on both sides of PVB was modeled by using DEM, while the otherparts were modeled by using FEM. The failure modes and impact acceleration of CDFPsimulation results are both consistent with the experimental results, which shows that thecombined DE/FE method has obvious advantages on the simulation and analysis of theimpact fracture phenomenon of the automotive windshield. |
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