Research On Drag Reduction Performance Of Laser Textured Microstructures On Paint Surface

With the increasingly severe energy crisis in the 21st century,energy saving and the development of new energy-saving vehicles have become the main exploratory field of researchers.As a protective and decorative chemical mixture coating,paint is widely used in the automotive industry,agricultural machinery,aerospace engineering and other fields.On the premise of protecting the integrity of base material,the textured microstructure on paint surface can reduce the surface drag force of transportation and achieve the purpose of saving energy and reducing pollution.In this study,laser micromachining technology is used for the preparation of microstructures on paint surface,implementing the large-area,high-efficiency,and low-cost processing scheme of drag reduction paint surface,and providing technical support for energy saving and drag reduction of future automobiles,rail vehicles and aircraft.The main work is as follows:1.The drag reduction simulation and analysis of microstructure.The turbulent boundary layer flow mechanism was analyzed,and the effects of period and depth parameters on the drag force of microgroove structure was simulated and studied by Fluent software,the drag reduction effect of different microgroove structures and the effects of their characteristic size on the drag reduction effect were analyzed as well.The simulation results show that the drag reduction rate shows a trend of first increasing and then decreasing when the period and depth of microgroove are increased.Under the wind speed condition of 33.3 m/s,the maximum drag reduction rate reaches 6.50%when the groove period is 300μm,the depth is 20μm,and the width is 80μm.2.The effect of processing parameters for microstructure.The interaction mechanism between laser and paint was studied,and the effects of laser processing power,scanning times,scanning speed and other parameters for microstructure of paint surface were compared and analyzed for different wavelengths of 10.6μm CO₂laser and 1064 nm fiber laser.The results show that the 1064 nm fiber laser has better controllability and repeatability on textured paint surface.The expansion and fracture caused by local melting and vaporization leads to roughening of structure inside the microgroove.In addition,a large-area and high-efficiency machining scheme for freeform surface of bionic drag reduction microstructures is further proposed,which provides a new strategy for energy saving and drag reduction of future automobiles,rail vehicles,and aircraft.3.Testing and analysis of performance.The wind drag force test was carried out for microstructure samples,and the feasibility of laser textured microstructures on paint surface for drag reduction was verified.The effect of period on the drag reduction performance of microstructure surface was analyzed.As the period of microgroove structure increased from250μm to 400μm,the drag reduction rate showed a trend of first increasing and then decreasing.When the wind speed is 33.3 m/s,the maximum drag reduction rate is 7.21%at the period of 300μm.Models was established to analyze the drag reduction mechanism of microgroove structure,and the"bipolar tandem air bearing"model was proposed to reveal the difference of drag reduction rate between measurement and theoretical calculation.Finally,the wettability and durability of microgroove structure on paint surface were studied,which provide a reference for the study of multifunctional drag reduction paint surface.