Analysis Of Front Structure Safety Performance Of Buses Based On Frontal Collision

Bus has a large passenger capacity,driving conditions are complex and diverse characteristics.Statistical analysis find that in recent years the occurrence of heavy traffic accidents vehicle type,bus accounted for 30%,while in the type of collision,frontal collision accounted for 13.64%,the proportion of both cases are the highest in the same type.With reference to the current crash safety regulations and research status at home and abroad,this paper selects a domestic fully loaded bus as the research object and analyzes the safety performance of its frontal structure during frontal collision as follows:Firstly,the finite element models of the whole bus,seat-dolly and front section frame are established in Hypermesh.The complete vehicle model is divided into four modules:chassis structure,body skeleton,exterior and interior of the body and other accessories are modeled separately,and each module is then verified by calculation in LS-DYNA,and the complete vehicle is assembled for each module after verification.The seat-bed finite element model is tested and simulated to verify that the model can be used for the analysis of the occupant damage of the whole vehicle.In addition,an experimental and simulated comparative analysis of the front section frame model is conducted to verify the validity of the established finite element model for the whole vehicle.Then,this study conducted a simulation test of the frontal crash of the whole vehicle with 100% overlapping rigid barriers at 30km/h with reference to the regulation JT/T1369-2020 "Occupant Protection of Bus Frontal Crash".The parameters required by the regulation are driver’s living space and occupant’s injury,and the output and boundary conditions of the vehicle model are set according to the requirements of the regulation.For this simulation,the driver survival space is extracted directly from the vehicle model and the occupant damage is extracted from the seat-dolly model.After the crash,the driver’s survival space L1 is 20 mm,and L2 and L3 are both 0,indicating that the driver’s survival space is invaded.The axial tensile force Fz of the neck of the left and right side dummies in the rear is 3.7 kN and 3.5 kN respectively,both higher than the index requirement of 3.1 kN;the ThAC value of the right side dummy’s chest is 35.6 g,exceeding the inspection index requirement of 30 g.The damage value of the rear dummy also failed to meet the standard requirement.The above results show that the initial model of this bus does not meet the standard requirements.The analysis of the deformation of the front structure of the bus revealed problems in the front surround crash structure and the bottom skeleton of the driver and other locations of the bus.Secondly,this study put forward the idea of improving the front structure of the bus for the problems existing in the initial model of the whole bus in frontal collision,and the main improvement methods are: adding hexagonal double-layer aluminum energy absorber,designing the steering wheel automatic forward flip structure and designing the through force transfer structure.With reference to the regulations,the improved vehicle model is verified,and the safety of the vehicle before and after the improvement is compared and analyzed.After the improvement,the vehicle performed well in the crash test,and the values of the distance parameters L1,L2 and L3 between the driver and the steering wheel are307 mm,330mm and 51 mm respectively,which indicated that the survival space of the driver increased after the crash;the damage values of the head,chest,neck and legs of the dummy are in accordance with the investigation index.The above data analysis verified the safety of the improved vehicle model and proved the effectiveness of the front structure improvement measures.Finally,the improved front structure of the vehicle model is combined with the actual situation,and the crash test under different working conditions is conducted according to the reference standard.There are two main cases: 1)the frontal crash test at different speeds,and the safety of the vehicle model under 30km/h,40km/h and 50km/h working conditions are compared and analyzed;2)the frontal crash test at 30km/h is conducted for the whole vehicle with complete mass,the whole vehicle with half full mass and the whole vehicle with full mass,and the safety of the three types of vehicles after the crash is compared and analyzed.The following conclusions are reached: a)Under the 40km/h speed condition,the driver’s living space and passenger damage values meet the standard inspection index,and the vehicle meets the standard requirements after the crash under this condition.In the50km/h speed condition,the chest damage values of the left and right dummies are 30.5g and 31 g respectively,which are greater than the indicator requirement of 30g;the neck damage value of the left dummy is Fz 3.15 kN,which exceeds the reference standard value of3.1kN;the neck damage value of the right dummy is Fx 3.4kN,which exceeds the reference standard value of 3.3kN.Therefore,the whole vehicle after the collision under this speed condition cannot meet the standard requirements.b)After the frontal collision of the whole vehicle with complete mass,the whole vehicle with half full mass and the whole vehicle with full mass,the driver’s living space L1,L2 and L3 are greater than 0,which meet the requirements of the index;the damage values of the passenger’s head,neck,chest and legs also meet the requirements of the index.Therefore,the above three types of mass vehicles meet the requirements of the regulations after the collision.