| As a kind of auxiliary lane,the truck escape ramp is used to let the brake failure vehicle drive away from the main road in the mountainous area and slow down till stop.At present,the fall protection net installed at the end of the truck escape ramp in engineering applications does have a protective effect on the vehicles that rush out of the truck escape ramp,but lack of theoretical basis and verification.To this end,finite element method is used to design and research the cumulative protection performance of the flexible fall protection net installed at the end of the truck escape ramp.The results provide a theoretical basis for improving the design and construction of the truck escape ramp,also have a good engineering application prospect.The main research contents are as follows:First,this thesis summarizes the current research status and proposes research methods and technical routes suitable for flexible fall protection net installed at the end of truck escape ramp.After comparative analysis of finite element methods,ANSYS APDL,Hyper Works and LS-DYNA softwares and explicit analysis are utilized to design and research the fall protection net;the LINK160,BEAM161 and LINK167 elements are used to establish the finite element model of the fall protection net,the plastic kinematic material,elastic cable material are used to simulate the real material characteristics of the fall protection net.Secondly,combine design with simulations,design the fall protection net and verify the rationality of the design parameters by the impact simulations.The specific process is to first design the overall size,material,mesh length,braiding form,shape and support structure of fall protection net,and then impacted by the rigid sphere,the Hybrid Ⅲ 50 th dummy model and the Ford F800 model,such as sit posture dummy impact,squat posture dummy impact,cab impact and whole vehicle impact.Finally,stress initialization method is used to research the cumulative protection performance of the fall protection net by two consecutive vehicle impacts.After first impact complete,Dynain file is used to retain the residual deformation and stress of the fall protection net and transfer it to the start of the second impact.The second impact is performed after the stress initialized. |
