Research On The Optimization Of The Structure Of The Urea Tank Support For Heavy-duty Trucks

Selective Catalytic Reduction(SCR)is the main technical route of heavy trucks for meeting Euro IV and above emissions requirements.Urea box,as the major part of SCR,is fixed on automotive chassis by urea box bracket.Due to the poor working conditions,complex environment,stress and heat impact in heavy truck operation process,the urea box bracket is easily fractured,even loose fixation or fall to the ground,which will seriously affect regular work of SCR.The heavy truck urea box bracket is the main study object of this paper.The paper utilizes finite element software to make fault analysis in order to optimize structure of urea box bracket,remove possible defaults and improve the quality.Firstly,this paper selects finite element analysis software to set up finite element assembly model and make finite element model analysis on the urea box bracket.It shows that the urea box bracket model frequency of level 1 and 2 are within the road excitation frequency range,the model frequency of level 3 is close to the engine idle frequency.The urea box bracket will be easily fractured under insufficient rigidity condition.In the second place,we improve the material and structure of the urea box bracket,like increase the thickness,intensify stiffener,change section shape and enhance strength.By making model and stress analysis comparison between original urea box bracket and improved one,the model frequency of improved bracket increases obviously and avoids engine idle ignition frequency.On the other hand,the dynamic stress decreases distinctly as well as the crack stress,which is only 3% to 4% before improved,and the stress of welding point in bracket root decreases more than 60%.At last,we carry out a 60,000 km road test of the improved urea box bracket.The test result presents that the bracket is still in good appearance and without any crack or fracture.After launching into the market,we make an after-sale tracking of optimized urea box bracket on 40 vehicles in alpine areas,highland,and high humidity areas.The failure rate of the optimized bracket decreases significantly from 10.26% to 0.75%.The after-sale claim also decreases and will reduce more than CNY 1,000,000 expenses annually.The above results indicate that,we can accurately find the failure cause through finite element model analysis,and make targeted improvement in material and structure.Thus we can increase model frequency,decrease dynamic stress,carry out road test and finally make sure the optimized urea box bracket in reliable and stable quality.