Determination Of TFT-LCD Substrate Glass Constitutive Parameters And Analysis Of Its Cutting Process

The demand for LCD in China is growing rapidly, and the quantity of domestic product is considerable. At the same time, it appeared a lot of problems of restriction on production efficiency in the cutting process, especially the LCD substrate glass rejection rate and the service life of the cutter wheel.The demand for LCD in China is growing rapidly, and the quantity of domestic product is considerable. At the same time, it appeared a lot of problems of restriction on production efficiency in the cutting process, especially the LCD substrate glass product yield and the service life of the cutter wheel.In the process of cutting TFT-LCD substrates glass, the cutter wheel pressed into the glass first, and then cut the substrate glass along the expected scribing trajectory under the support of cutter component. During the cutting process, the service life of cutter wheel are seriously affected by the continuous impact, moreover, it plays a decisive role to the rate of finished products that the groove formed by cracks initiating and expanding under the action of cutting edge. Therefore, the two problems of improving the production efficiency of LCD substrate glass and the service life of cutter wheel are relevant.In this paper, the JHC (Johnson and Holmquist Ceramic Model) constitutive model theory was used and the cutting process was simplified to two-dimensional plane. Firstly the calculation model of cutting process was established in combination with dynamic mechanical properties and the brittleness property of TFT-LCD substrate glass. Secondly the cutting process was simulated numerically by applying the explicit dynamic analysis computer software LS-DYNA. Thirdly the constitutive parameters were modified repeatedly by comparing the simulation results of groove with the actual cutting result, and the constitutive parameters suitable for LCD substrate glass were obtained. Finally, based on the constitutive parameters, the contact force between cutter wheel and LCD substrate glass was analysed and the simulation results of groove was gained under normal cutting condition.On the basis above, through simulating three kinds of abnormal cutting processing, the force applied on cutting wheel and the simulation result of groove at different cutter wheel-shaft fit tolerance was obtained, which was used to analyse the influence over both the finished product rate of substrate glass and the service life of cutter wheel. At last, the main factors influencing calculation precision in cutting process numerical simulation of were explored, and the suggestions for improving calculation accuracy were given in this paper. Main content is:1. By contrasting elastic, elastic-plastic and JHC constitutive theory, JHC constitutive model theory was selected to describe the dynamic mechanical properties and brittleness characteristics of the TFT-LCD substrate glass in the cutting process, and then explicit dynamic analysis computer software LS-DYNA was used to simulate the cutting process numerically.2. After getting the cutting process parameters and cutting result of the groove’s profile by experiment, the simplified calculation model of cutting process was established, which combined with the JHC constitutive model and the material’s mechanical properties, and then the preliminary constitutive parameters were calculated by running the program compiled for calculation model of cutting process. The simulation results were obtained after establishing the finite element model of cutting process by applying computer software LS-DYNA. In addition, the actual cutting results were compared repeatedly with the simulation results in order to modify the preliminary constitutive parameters. The work of simulating, comparing and modifying were circulated until the final parameters are suitable for TFT-LCD substrate glass numerical simulation.3. Final constitutive parameters were used for further simulation of cutting process. The characteristic of contact force, between cutter wheel and TFT-LCD substrate glass, and the effects of simulation results of groove were analyzed under three different cutter wheel-shaft fit tolerance in cutting process. This can provide theoretical reference for actual working state of cutter wheel.4. Based on a lot of simulation results, several primary factors affecting the calculation accuracy were summarized through analyzing parameters controlling the calculation process, and suggestions for the improvement of calculation accuracy were given.