The Simulation Study On The Gas Mask Exhalation Valve Working Condition

Exhalation valve is one of the key part of the gas mask,its air-tightness performance has directly impact on the usability of the entire gas mask.At present,the study about chemical defense valve is very few,thus,its working characteristics and the factors which will affect the valve working stability need to further investigated and researched.Therefore,research on the gas mask's character like valve air-tightness has great help in the comprehensive understanding of the exhalation valve working characteristic that has great improvement of whole gas mask's usage performance and with significant meaning.This article is analyze based on finite element analysis theory and parametric design theory.According to the rubber material's character to simulate the valve assembling process by determine its own constitutive model.According to the air-tightness requirement toward exhalation valve during its working condition to put forward the evaluation of valve's air-tightness performance by judge from its contact pressure that sensed with the valve's base.This discovery overcome the limitation that the physical testing method is the only get through way to evaluate whether the air-tightness performance is good enough or not,besides,realized to use the related parameters to directly value the valve air-tightness and determine the expiratory resistance by simulation.Last,through analyzing the valve and seat structure to find out the real facts that influence the valve air-tightness and improving it.In order to determine the constitutive model,the experimental data are input into ANSYS Workbench,and those commonly used Mooney-Rivilin,Yeoh and Ogden are selected to make the constitutive model for fitting.And comparing the physical experimental data curve with the simulation curve result.Final,we figure out the most suitable valve material's constitutive model is Mooney-Rivilin two-parameter model,two of which are C10=1.74 and C01 =-1.51.By analyzing the structural characteristics of the valve and the seat to get the two models appropriately simplified.The two-dimensional model was final choose for analysis by considering the amount of calculation and comparing the mesh generation between 3D model and 2D model.Use ANSYS Workbench to simulate the valve assembling process and determine the size of the valve assembly force.In order to figure out the working character of valve,we conducted simulation test toward breath in and breath out two aspects and final got the contact pressure and expiratory resistance of valve in breathing condition.According to this data,to set parametric modeling for the important structure which has affects toward the working performance of valve.After thousand times trying and simulation with the valve and pedestal base,finally we settled the improvement program.The simulation experimental result showed:the assembly force of valve is 11N,with very small deviation with the test result.The breath resistance is about 53pa.When the valve increases its thickness for 0.05mm the contact pressure sensed by valve would be stronger;when the chamfering of the shutter reduced by 0.02mm the valve contact pressure also will be stronger and the exhalation resistance could still meet the requirement.Thus,the conclusion of this case is to properly increase the valve's thickness or reduce the chamfer can improve the air-tightness.