Research On Multi-body Simulation Method For Vehicle Rollover Safety

Safety,energy saving and environmental protection have always been important topics in the development of the automotive industry.Car safety,as an indicator directly related to the car user's own life and property,occupies a pivotal position in the minds of consumers.The frontal collision,side collision and backside crash collision in the automobile collision safety and occupant protection have been formed through many years of research and development,and a number of perfect evaluation mechanisms have been formed,which greatly reduce the death rate and economic loss of traffic accidents.The car tumbling accident is a type of traffic accident where the incidence is smaller than the above three types of accidents.Although the incidence of tumbling accidents is relatively small in all traffic accidents,the mortality rate is very high.In China,due to the lack of perfect and mature evaluation mechanisms for tumbling accidents,there are relatively few relevant studies.With the decrease of the incidence of frontal and side collision accidents,the incidence of tumbling accidents has shown an upward trend.Compared with frontal and side impacts,the automotive rollover process lasted longer and more complex,resulting in more difficult rollover accidents.The duration of tumbling accidents is mostly around 3000 ms,and the calculation time of the finite element simulation model based on LS-Dyna's nonlinear large deformation is too long.A complete FEM vehicle rollover model requires at least 3 days to complete a calculation using a high-performance computing server.The computational efficiency is extremely low,which brings great inconvenience to the research,especially for the occupant movement and damage related to the tumbling process..The deformation of the car body structure consumes more calculation time in the finite element calculation process,and most of the car body structure does not have deformation or deformation in the rolling process of the whole vehicle and has no significant influence on the occupant injury.Therefore,we can use the vehicle's finite model for parameter input,use the MADYMO to simplify the model,and study the occupant's motion characteristics and damage on the basis of ensuring the rollover attitude of the model is correct.In this thesis,the plastic hinge theory is applied to the tumbling multi-rigid body model.MADYMO is used to establish a fine multi-rigid model of a certain model,which effectively ensures the accuracy of the tumble model.Compared with the finite element model,the calculation time is shortened by more than 20 times.The vehicle rollover test was carried out on the vehicle under the FMVSS 208 regulations.The simulation model and the test vehicle showed a high degree of coincidence on the tumbling response.The validated model was used to analyze the dynamic response and damage of the dummy in the tumbling process.The regression analysis was used to study the relationship between the main parameters of the vehicle and the damage of the main driving neck in the rolling.The results showed that there was a positive correlation between the main driving neck injury and the change of the vehicle wheelbase.In order to verify the adaptability of the model,the simulation model was modified and simulated according to the spiral tumbling test standard.The subsequent spiral tumbling test showed that the model has good applicability and high application value.The vehicle rolling model established by using the multi-rigid body method described above can greatly improve the efficiency of research on rollover,especially on the occupant injury during rollover,and is beneficial to quickly determine the occupant's motion and damage influencing factors in the rollover process.The above research content is of great reference value for the study of automotive rollover safety,and it has practical value for the improvement of rollover safety performance of vehicles,which helps the vehicle manufacturers to develop safer automobiles.A new roof airbag structure dedicated to automobile rollover is proposed.Compared with the existing roof airbags,this new structure improves a number of deficiencies,making the deployment of the airbags safer for the occupants,and the protection capability being more lasting.