Design and process analysis of bus DCPD bumper
2024-04-25
With the development of lightweight, green and intelligent passenger cars, traditional PP injection molded double-layer structure plastic bumpers have been criticized for high mold costs, materials that cannot be recycled, and it is not easy to carry electrical parts. Large, poor appearance and other reasons were eliminated. Therefore, the research and development of new material bumpers with low mold cost, easy structure forming and good comprehensive durability has become an important research task for automobile OEMs.
New processes using dicyclopentadiene (DCPD) and reaction injection molding (Reaction Injection Molding) have become a new direction in bumper research and development. Automobile exterior parts made of DCPD material have the characteristics of low mold cost, simple structure and excellent product performance, which are very suitable for application in the process scheme of bumper molding. Based on the DCPD-RIM reaction, this paper first uses CATIA to design the bus bumper, then uses MoldFlow to analyze the bumper mold flow, then uses PreSys to analyze the bumper safety factor, and finally uses temperature box and artificial aging box to test the bumper sample bench performance, successfully completed the DCPD material in the bumper field instead of metal materials and traditional PP material attempt, the main work is as follows:
Firstly, based on the bumper regular material and reference, the DCPD material is tested to obtain its tensile strength, bending strength, Rockwell hardness, impact strength and other information. After testing the basic parameters of DCPD material, the process planning and equipment debugging of RIM reaction are carried out, so that the pressure in the raw material storage tank is suitable for the parameters of the raw material, the mixing nozzle can fully mix the raw materials, and the initial temperature and pressure in the mold are helpful to the filling of the raw material.
Secondly, CATIA is used to design the bumper foundation size parameters, important process parameters and connection fixing methods in detail. Use CATIA and CFD to design the size of the air intake grille so that it can absorb enough cold air to reduce the temperature of the engine room; use CATIA and LIDAR360 to arrange the position of the electrical parts and check the installation size on the bumper; use CATIA to design the important process parameters such as bumper fillet, mold angle and reinforcing rib in detail to reduce obstacles for subsequent mold flow analysis; CATIA is used to design the fixing point of the bumper in detail, and the combination of direct fixing method, plastic bracket fixing method and buckle connection is used to ensure that the bumper is evenly matched with the surrounding environmental parts.
The mold flow analysis of DCPD bumper is carried out by using MoldFlow again, and the filling process of material liquid is simulated by using 10-gate mode and 12-gate mode. The holding time, injection pressure, film temperature, weld line position, deformation and other information under the two gate modes are compared, and it is concluded that the 12-gate RIM mold is more conducive to bumper surface quality and matching effect.
Finally, PreSys is used to calculate and analyze the pedestrian protection of DCPD bumper, and the bumper assembly is tested by temperature box and artificial aging box. The pedestrian protection analysis calculates the scores of head type and leg type respectively, and obtains that the total score reaches the four-star standard of national standard and European standard. Bench performance analysis analyzes the performance of the bumper assembly such as long-term heat resistance, short-term heat resistance, cold and heat interchange, cold resistance, weather resistance, etc. After such tests, the bumper does not have boundary deformation and paint surface damage, which meets the operating conditions of the bus.
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