Surface Quality Analysis Of Laser Cutting Liquid Crystal

Liquid crystal glass has been widely used in laptops,monitors,high-definition wall-mounted and communications equipment.High-yield,high-efficiency and low-cost cutting method is required for making glass product.In the mechanical cutting method,the glass surface is first marked with the help of a wheel or diamond point tool and then an extreme force is applied to break the glass along the scribing path.Often,grinding and polishing are necessary to make a smooth surface finish,which not only increase the cost of fabricating but also becomes highly time consuming.Laser cutting for its non-contact,easy to control,non-polluting and other advantages become an important tool for contemporary machining.However,in the laser cutting process,due to environmental factors and the setting of cutting parameters change,it is easy to produce surface quality problems,such as cracks.Microscopic analysis of the laser cutting liquid crystal glass revealed that there are regular arrangement of edge crack bubbles of different sizes and other quality problems on the glass surface.As the cutting temperature changes,the edge crack gradually expands and develops a bifurcation connection after extending a certain longitudinal distance.Based on the above experiments,the surface quality of laser cutting liquid crystal glass was analyzed by theoretical derivation,experimental phenomenon and finite element simulation.the main contents of this paper are as follows:Firstly,the basic principle of laser cutting liquid crystal glass is discussed based on the knowledge of brittle fracture mechanics,thermoelasticity and heat transfer.The stress intensity factor calculation method and the fracture criterion of surface edge crack are analyzed based on the knowledge of fracture mechanics.Then,the main crack propagation phase of the cutting liquid crystal glass is analyzed based on the related papers at home and abroad.We inference that the crack propagation satisfies the maximum circumferential tensile stress.In addition,because of the different of tensile stress,temporal zone has more serious quality problems than Steady state zone.The liquid crystal glass reaches the softening temperature,causing Bubble generation.Second,Abaqus software is used to simulate the real situation of laser cutting liquid crystal glass.According to the finite element analysis results,we get that bubbles can cause the ambient temperature to rise and Larger bubbles will produce greater thermal effects.We can eliminate bubbles by changing laser cutting parameters and improving the glass production process.Finally,the finite element model of edge crack is established using a quarter node method to solve the stress intensity factor.The effect of laser cutting parameters on crack propagation was discussed and analyzed.We can increase or decrease the value of K_? and K_? by reducing or increasing the laser scanning speed.Moreover,the influence of laser power is greater than that of laser scanning speed.The theoretical calculation of the crack deflection angle is consistent with the experimental results.It is shown that the crack propagation direction satisfies the maximum tensile stress theory.The value of K_? increases with the crack growth.Near the crack bifurcation point,the value of K_? increases greatly,which indicates that the crack deflection angle increases rapidly.