Study On Mechanism And Process Of Polishing Enginering Ceramic With Ultraviolet Laser

Because of its thermostability,antioxidation and high wear resistance,Al2O3 is widely used in many fields such as mining,aerospace,electronic and trasmission industry.But there are many difficulties in processing due to engineering ceramics material's britteness,high hardness and poor reliability.So,laser polishing have aroused and there is a good prospect of application and development because it has wide application,high processing efficiency,non-contact,high processing quality.Theoretical and experimental researches on the mechanism of short-pulse ultraviolet laser polishing of Al2O3 ceramics were carried out in this paper.It also showed how technological parameters influenced on polishing quality by single factor experiment.Firstly,this article summarized the background,significance and status of studies on the polishing of Al2O3 ceramics by short-pulse ultraviolet laser.Secondly,theoretically analyzing,it described short-pulse ultraviolet laser polishing on Al2O3 ceramics' thermal effects,thermal stress and the mechanism of photochemical reactions.The temperature fields and stress fields of polishing on Al2O3 ceramics by short-pulse ultraviolet laser with various laser fluence,and the material removal mechanism in the process of short-pulse ultraviolet laser react with material was verified by experiment.Thirdly,the indentation depth and morphology on Al2O3 ceramics generated by short-pulse ultraviolet laser with various laser fluence and scanning speed was analyzed by ANSYS emulation analysis and experiment research,which provide as a basis for choosing the technological parameter of the polishing on Al2O3 ceramics by short-pulse ultraviolet laser.At last,single factor experiment was used to find how technological parameters influenced on material surface roughness while short-pulse ultraviolet laser polishing on Al2O3 ceramics.The main research methods and conclusions are as follows:1.A model of thermal effects between pulse laser and material was built that based on a one-dimensional heat conduction equation.According to the theory,it was deduced that the damage threshold of material melt and evaporation when short-pulse ultraviolet laser polishing on Al2O3 ceramics was 4.38J/cm and 6.67J/cm2,respectively.On the basis of changing relationship between thermal stress and the temperature of materials,the mathematical model of thermal stress was established,and the condition of the thermal stress fracture was found.By analyzing the photochemical reaction condition,it showed that when Al2O3 ceramics was polished by short-pulse ultraviolet laser,there wasn't a single photon absorption photochemical reaction,but it was possible to lead the photochemical reaction of multiphoton absorption.2.The results of ANSYS smulation analysis and experiment showed that the main reaction mode of short-pulse ultraviolet laser polishing on Al2O3 ceramics was thermal effects,and materials' fusion and vaporization.A microcrack would emerge on the material surface when the laser energy density was higher than 7J/cm2.As the laser energy density increased,there would be a plenty of regelation splash content on the material surface,and the whole piece of material would be stripped because of thermal effect's impact.3.Through the short pulse ultraviolet laser score ANSYS simulation and experimental research of Al2O3 ceramics,It deduced the short pulse ultraviolet laser polishing Al2O3 ceramics,reasonable laser fluence range is 5J/cm?7J/cm.4.The conclusions can be drawed by single factor experiment:(1)With the increase of the energy density,the surface roughness decreased first and then increased,the surface roughness Ra is minimum when the energy density is 7J/cm2;(2)With the increase of the energy density,The surface roughness increased first and then decreased,the surface roughness Ra is minimum when the laser velocity is 50mm/s;(3)The surface roughness Ra is minimum when the laser scanning interval is 2?m;(4)The surface roughness Ra is minimum when the laser defocus is 0.1mm;(4)The more complex the scanning way is,the lower the surface roughness is.