| With the improvement of China’s comprehensive national strength, demand for traffic travel is increasing. As the major traffic tools of road transport, bus provides convenience and high-efficiency for the vast number of passengers, However, heavy traffic accidents occur frequently, causing heavy casualties. Although bus body of high-safety can reduce casualties, yet at present domestic has not promulgated evaluation criteria of passenger frontal impact safety. Therefore, the research on automobile impact safety is of great significance, which will greatly promote the development of the regulations in regard to bus impact.This article selects a certain full load 6120 bus as the research object. The geometric model of full-vehicle was established in CATIA and finite element model in HyperMesh. Impact of the front 100% overlap was conducted on the rigid barrier at the speed of 30km/h. The deformation, energy and acceleration were analyzed after the impact. And the simulation results were compared with the results of real vehicle tests for a bus in China, verifying that the impact model was of higher credibility.Referring to GB/T 20913-2007, the research on the frontal 40% offset impact of the full load bus was conducted, at the initial impact speeds such as 20km/h, 30km/h, 40km/h and 50km/h. Then the deformation, the energy, the acceleration and the intrusion of the A column were analyzed after each speed impact. The results showed that the front wall and chassis were the main deformation component, with the energy of 70% absorbed. At 20km/h and 30km/h, the deformation of the body was smaller, while at the 40km/h and 50km/h, the front part of bus was deformed severely, indicating the bus body can not realize the self-protection.In order to evaluate the driver’s living space more reasonably, an evaluation method of living space was discussed. After the impact, the corresponding survival space indices at four different velocities were 0.883, 0.759, 0.561 and 0.341, respectively. The function between the survival space indicatior and the impact speed was obtained by fitting the three order curve in MATLAB. According to the GB 26512-2011, the limits of each index was determined, by calculating, the critical survival space index was 0.688, which further accquired the corresponding critical speed of 34km/h.To validate the critical speed, five dummy models were set in typical regions of bus, and the rigid barrier impact of the front 40% overlap was conducted at the speed of 34km/h to analyze occupant head, neck, chest, pelvis, legs and other performance indicators after the impact. According to C-NCAP scoring rules, the driver was scored 14.1, under the condition that the full score is 16. Meantime, referring to the performance limits of C-NCAP indicators, the evaluation method of normalized damage assessment(WIC) was introduced. After the impact at 34km/h speed, the performance of the driver is basically consistent with the high performance limit of the regulations. Therefore, 34km/h is a critical speed of the selfproteciton and can be used to evaluate the structural safety of different bus.In this paper, engergy-absorbin properties of bus body have been studied from four different materials of Q460, Q390, Q420 and Q345 under the same impact speed. The results showed that under absorption the same impact energy, the material of higher yield strength have a rapid and little deformation. Therefore, in order to improve the bus crash safety in the premise of ensuring the lightweight, the high yield strength material shall be selected as possible to ensure that the energy can be absorbed quickly and that the structural deformation can be reduced.The research results of this paper can provide some references for the development of the domestic bus front offset impact standard. |
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