Dynamic Analysis And Structural Optimization Of The Automotive Cooling Fan Shroud

With the rapid development of the automobile industry,the competition of the auto parts market is becoming more and more competitive.An effective way to improve product's competitiveness is to replace the original material by a more cost-effective material.In order to ensure the new product's working performance,using the method of structural optimization to optimize the new product's structure and reduce its production costs at the same time.The cooling fan is a very important part of the automobile cooling system,which plays a role in cooling the water tank to ensure the normal operation of the motor.As a main part of the cooling fan system,the fan shroud can fix the motor,which directly ensure the normal operation of the cooling fan.Because of the complex working environment,the fan shroud needs to bear various loads and dynamic excitations,which puts forward corresponding technical requirements for the strength and dynamic characteristics of the fan shroud.In this paper,a cooling fan shroud of an automobile is taken as the research object.In order to reduce the production costs,PP-GF30 was used to replace the original material called PA66-GF30.(1)The three-dimensional model of fan shroud was established by UG.According to the QC/T733-2006 Cooling fan module specification for automobile,the static strength and impact strength of the fan shroud were analyzed,and the strength was checked.(2)Dynamic analysis of the fan shroud with new material was carried out and the dynamic characteristics of the structure was analyzed.According to the results,the reasons for the excessive vibration of the new fan shroud when the motor works on the high speed were analyzed.(3)According to the differences between the new fan shroud and the original one in the dynamic characteristics,the analysis results of the original fan shroud's harmonic response was taken as a reference.Based on the HyperWorks platform,the design variables were selected.The structure of the fan shroud was optimized using GRSM algorithm so that the dynamic characteristics of the new fan shroud reached or exceeded the original level.(4)On the basis of dynamic characteristics of the fan shroud which is made of new material,reducing the volume of the fan shroud was taken as the goal,the dimensions of each part of the fan shroud was optimized to minimize the production costs.(5)The P-S-N curve of the new material was derived from the empirical formula.The fatigue life of the fan shroud under the environment of random vibration was calculated by nCode DesignLife,which provided a basis for further optimization design.Through the above-mentioned work,replacement design of material was achieved.After the optimization,the first-order natural frequency of the fan shroud increased by 11.2%,which can avoid the resonance excitation of the motor and meet the requirements of the original dynamic characteristics.Meanwhile the volume of the fan shroud reduced by 9.9%,which reduced the cost of production and was recognized by the manufacturer.The research method of this paper has a common value in engineering application,and has some guidance values for the design of material replacement for the same types of products.