Study On Laser Surface Texturing And Drag Reduction Technology

Surface texturing technology plays an important role in the field of friction reduction.In this thesis,the processing ability of laser surface texturing technology for alumina ceramics and silicon nitride ceramics was discussed.The influence of the surface texture on the tribological properties was analyzed by experiments and simulation.In order to understand the laser surface texturing process on ceramics more comprehensively and accurately,this thesis compared the effects of single pulse intervals processing and ring packing processing with a high-power nanosecond laser.The results show that single pulse intervals processing has advantages of high processing efficiency and low residual stress.The processing quality depends heavily on the quality of laser spot and the dimple diameters range from 18μm to 53μm.The ring packing processing which can be used to make micro-pits with diameters larger than 70μm has been more widely used.The quality of surface textures can be effectively improved by adjusting the ring packing processing parameters,but the machining efficiency is relatively lower.The processing quality of a picosecond laser on laser surface texturing on alumina ceramics and silicon nitride ceramics is analyzed.Results show that the adjustment of the average power,scanning speed and repetition times can effectively reduce the roughness at the bottom of the groove,decrease the taper of the groove and reduce the production of oxidation products.The tribological properties of laser surface texture on polyimide were studied by a friction tester.Results show that the surface texture can improve the tribological properties of polyimide materials.The surface textures with a certain space can effectively improve the bearing capacity of the friction pairs and reduce the friction between the friction pairs.However the burrs produced in the machining process will seriously affect the surface roughness and increase the friction when the spacing is too small.The micro-pits with spacing greater than 10μm,diameter of 30μm,depth from 10-15μm,have the best tribological performance.The tribology performance of surface texture under hydrodynamic lubrication was primarily studied by computational fluid dynamics(CFD).It was found that the bearing capacity and friction property can be significantly improved by using micro surface textures.The hydrodynamic lubrication performance of surface texture has connection with the variations of texture parameters and the appearance of eddy in the fluid region.The eddy in the fluid region could have negative influence on the performance of surface texture.The micro-pits with depth from 2μm to 10μm,width of 40μm have the optimal performance.The results of this study can offer meaningful reference for the laser surface texturing tech and its application in friction reduction.