Study On Crashworthiness Design Methodology Of School Bus Seat

Due to frequent accidents of the school bus,our government emphasis more and more on the safety of school bus.As an important safety component of school bus,the safety level of seat is directly related to the students' lives.Considering the safety issues of school bus seats,our country had proposed a safety regulation of school bus seats GB24406.In 2012,the regulation was modified to expand the scope of the school bus seats which were claimed to meet regulatory requirements and increase the requirements of dynamic test with dummies.The dynamic test which was proposed in new regulation has increased the safety requirements of school bus seat and made design process of school bus seat more and more difficult.The domestic development of school bus is later than other countries.The design of school bus seats mainly focuses on imitating foreign seats or modifying the passenger seat of normal bus which leads to poor qualification rates of school bus seats.With the regulatory requirements getting more stringent,the various safety studies of school bus seats started in recent years,especially about the dynamic test.Many manufacturers gradually began to use the CAE technology in the design and optimization process of seat in order to predict the performance of products.However,the applications of CAE technology mainly focused on a large number of simulation based on the geometry data which had been modified several times.There is lack of studies of design rules and methodology.Therefore finding a forward design methodology which can quicken the design and optimization process and reduce quantities of CAE simulation is of great practical significance.The thesis was supported by the school-enterprise cooperation project which aimed at finding a design methodology of school bus seat through the optimization process of a seat.Ls-dyna and Madymo software were used to established a dynamic simulation model of the school bus seat,which was validated by comparing with the actual test.The injury source and dynamic response of dummies and seats were also carefully analyzed.The concept of energy density was introduced to make the analysis process of collision energy suited for multi-conditions and dummies.In addition,the stiffness distribution of school bus seat was studied as well and the concept of 3-dimension stiffness was put forward in the paper.Some studies on the relationship between stiffness of seats and damage response of passengers had been accomplished.In order to accelerate the optimization process of seats,reduce the quantities of computation and realize the forward design of seat performance,the simplified mechanical model of the school bus seats was introduced in the process of optimization which realized the parameterization of seat mechanical property.Mechanical parameters of school bus seat were treated as optimization factors which were used in the ISIGHT software.Optimal Latin hypercube DOE method and Genetic optimization algorithm were chose to find the optimal stiffness performance of seats which should minimize the injury of passengers.Meanwhile,a mechanical parameter database of standard parts which is in the selection range of seat frame had been established and realized the selection of the parts was based on the mechanical requirements of seat performance.The final optimized results can fully meet the requirements of the dynamic tests,and validate that the simplified mechanical model was effective in the optimization process of seat which has a great practical significance to achieve the forward design of seat performance.