Research On Double-Sided Laser Ceramic Processing Technology Based On Thermal Cracking Method

Laser thermal stress control fracture cutting technology(laser thermal cracking technology)is to use laser local irradiation to produce uneven thermal expansion,which in turn generates special tensile and compressive stress fields to control the crack propagation process.Since there is small heat-affected zone in the cutting process,the surface quality and mechanical strength of the cutting material are better than melt cutting,which is suitable for different types of brittle non-metallic materials and has broad application prospects.However,for ceramic materials with high hardness,high melting point,and opaque properties,the laser beam cannot pass through the interior of the material,which makes the cutting quality and efficiency of this technology when cutting such large thickness ceramic materials low.Therefore,achieving rapid crack-free cutting of large-thickness ceramic materials(thickness> 3 mm)has become an urgent problem to be solved in current laser thermal cracking technology.Therefore,on the basis of in-depth analysis and research on the process and mechanism of the existing laser thermal stress cutting technology,this paper proposes a new double-sided laser simultaneous cutting ceramic technology based on thermal stress-controlled fracture,using theoretical analysis and numerical simulation technology in-depth The distribution of the temperature field and stress field inside the material under the action of double-sided symmetrical synchronous laser radiation and the crack propagation method and efficiency during cutting are studied.,Provides an important theoretical basis and practical application value.Firstly,taking the one-dimensional model ceramic material as an example,the distribution function of the temperature field and the stress field in the thickness direction with time under the two types of boundary conditions acting on the upper and lower surfaces of the material simultaneously is deduced,and the materials under the two types of boundary conditions are determined.The stability time of stress extreme value on the symmetrical section,the size and position of stress extreme value and their function expressions are compared by the results of finite element numerical simulation.The research shows that for a certain thickness of the material,when the thermophysical parameters of the material are unchanged,by adjusting the stabilization time of the radiant heat,the maximum tensile stress extreme position can appear at the middle thickness of the cutting profile of the material,and along with the thickness,The direction is symmetrically distributed,and the maximum tensile stress gradually transitions to the maximum compressive stress on the surface of the material.Among them,the position stability time of the extreme value of the tensile stress is related to the thermophysical parameters of the material and the thickness of the material,and by adjusting the heat flux density on the surface of the material to achieve the control of the magnitude of the tensile stress.The above research provides a theoretical basis for the double-sided symmetric laser thermal stress-controlled fracture cutting of thick ceramics.Secondly,through the numerical simulation technology,the spatial distribution of the heat on the surface of the laser radiation material(laser heat source model,laser spot shape and size,the form of the surface of the laser radiation material)and the time distribution(laser power and scanning speed)parameters for the influence law of temperature field and stress field on the symmetrical section of ceramic material are deeply studied.Studies have shown that: increasing the radiation area can cause the peak tensile stress on the cutting surface to move from the front or back of the laser spot to the middle of the plate thickness;For the same laser radiation area,With the elliptical spot laser,the temperature and stress field of the material are more concentrated in the laser scanning direction,and its stress gradient and stress extreme value increase;Compared with the single-sided laser,under the action of the double-sided symmetric synchronous laser,a higher stress value is maintained across the entire cross-section of the ceramic material,and the high tensile stress area gradually expands from the upper and lower surfaces of the front area of the laser spot to the middle area in the thickness direction,under prefabricated penetrating cracks,the crack propagation form extends from the middle part of the thickness to both sides,the crack propagation speed is fast,and the phenomenon of delayed fracture is few.Finally,using the thermo-mechanical coupling and crack propagation numerical simulation technology,the temperature field and stress field on the cutting profile of the ceramic material and the crack growth process under the single-sided and double-sided synchronous laser processing conditions were numerically simulated,and the technologies was verified by comparative analysis Under the same laser processing parameters,the maximum cutting thickness of the material,the laser power required under the same cutting thickness,the laser scanning speed,and the advantages of crack propagation form and efficiency.Studies have shown that compared with single-sided lasers,The minimum laser power Pmin required for effective cutting when the double-sided symmetrical synchronous laser cuts materials of the same thickness is significantly reduced,and the required maximum cutting speed Vmin is more than doubled,which significantly improves the laser cutting efficiency;Under the same laser process parameters,the crack propagation speed on the cutting profile is faster than that on the single-sided laser,and the crack propagation distance along the laser scanning direction increases,which can cut larger thickness ceramic materials.