Mechanical Analysis And Optimization Design Of Support Framework Of Positive And Negative Pressure Flat Flexible Ventilation Pipe

In many scenarios,such as underground space,subway tunnel,highway railway tunnel,high-rise building fire protection,fire rescue,etc.,ventilation system is required.Positive / negative pressure ventilation is generally adopted for ventilation,hard pipe and soft hose are used for positive pressure ventilation.Hard pipe or soft air pipe with support frame are generally used for negative pressure ventilation.However,hard air pipe is bulky,and it is not convenient for transportation,erection,connection and sealing,and it is not available in some special cases,such as excavation of special long single tunnel and ventilation and fire fighting of high-rise buildings;and spiral support frame Although the soft air duct has the ability to bear negative pressure,the spiral support skeleton flexible air duct can only be compressed axially,and the compression amount accounts for more than 1/4 of the original length,which makes it difficult to carry out.So this paper designs a ventilation pipe which can flatten and curl when it is not working,save space and convenient transportation,and can bear negative pressure when working,and carry on mechanical analysis and optimization design for its support skeleton snake spring.The main work and results are as follows:(1)According to the stress characteristics of positive and negative pressure air ducts,the design technical conditions of flat soft ventilation pipes are put forward.The overall design of the pipe wall and support framework is carried out: PVC coated cloth is selected as the manufacturing material for the pipe wall and the manufacturing technology is designed;the snake spring is selected for the support framework,and the65 Mn elastic spring is selected comprehensively considering the composition and mechanical properties of the material Spring steel is used as the material for the manufacture of snake spring.(2)The finite element simulation model is established,and the flattening simulation analysis of four snake springs with the same pitch,width and spring wire diameter is carried out /v iK =F mσ The value is the index of comprehensive evaluation of snake spring,namely the ratio of the elastic force to the mass and the maximum equivalent stress product.Finally,the V-shaped snake spring with the maximum Kv value is selected,and the sensitivity analysis of the spring spring f with the pitch,width,radius of arc and wire diameter is made,and the influence of spring wire diameter on the return force F is the greatest.(3)In view of the characteristics of high computational ability and long calculation time required for snake spring simulation and analysis,a proxy model of V-shaped snake spring simulation based on BP neural network is established.The orthogonal test sample data is used as the training data set of BP neural network,and the validity of the proxy model of BP neural network is verified by the test data set;the different V-shaped snake spring is obtained The optimal solution under pitch is analyzed and compared,and the structure of V-shaped snake spring with the maximum Kv value is selected.(4)The buckling finite element analysis of the equivalent rectangular section ring is carried out by using the radial compression stiffness equivalence between V-shaped snake spring and rectangular section spring.The critical load is calculated.The flat flexible ventilation pipe designed according to this design is proved to be effective.The operation is stable and non collapsible under the critical load,and the ventilation design of the flat soft air duct is achieved requirement.