Study On Mechanisms And Key Technologies Of Multi-focus Laser Separating Brittle Transparent Materials

Brittle transparent materials are widely used functional materials.Among them,the KDP crystal is the necessary material of China's "Inertial Confinement Fusion Project,(Shenguang Project)".At the same time,other brittle transparent materials,like glass materials,laminated glass materials,etc.,are also widely used in construction,automotive,shipbuilding,aerospace,military,optical and other fields.However,at present,the separation of brittle transparent materials are generally accomplished by mechanical methods,which facing a series of problems such as poor cutting quality,slow cutting speed,high cutting loss,and cumbersome cutting processes.To solve above problems,this paper innovatively utilizes multi-focus laser to separate a variety of brittle transparent materials to solve the existing problems of the separation of brittle transparent materials.In this paper,the mechanisms and key technologies of multi-focus laser separating brittle transparent materials were studied systematically,and the researches of the design of optical systems of multi-focus laser,theoretical modeling,finite element numerical simulation analysis,experimental exploration and so on were accomplished.The main achievements are as following:(1)The generation mechanisms and optical design processes of two kinds of multi-focus laser—derived multi-focus laser and flexible multi-focus laser were analyzed systematically.Among them,the derived multi-focus laser put two concave reflecting mirrors on both sides of the brittle transparent materials.The front concave reflecting mirror has a pore on the center,and the laser beam pass through the pore to enter the interior of the brittle transparent material.After the laser beam passes through the brittle transparent material and be focused for the first time,the laser beam will be reflected back and forth by the two concave reflecting mirrors and be focused by times,thereby generating multi-focus laser inside the brittle transparent material.At the same time,the flexible multi-focus laser innovatively utilize a series of focusing lenses with pores on the center to form the flexible multi-focus laser optical system.When the laser beam passes through the flexible multi-focus laser optical system,the laser beam will be divided into multiple parts by the pores on the focusing lenses and be focused by different numbers of focusing lenses,thereby obtain different focal lengthes and generate multi-focus laser inside the brittle transparent materials.Both this two methods could generate multi-focus laser inside the brittle transparent materials.Moreover,the multi-focus laser optical system were established,thereby mechanically and practically proving the correctness and feasibility of the optical design of multi-focus laser optical system.(2)The finite element models of multi-focus laser separating brittle transparent materials were established.Firstly,the mathematical models of the generated laser foci inside the brittle transparent materials were established,and then the optical fields inside the brittle transparent materials and heat source models inside the brittle transparent materials could be obtained.The finite element analysis software(ANSYS)combining the heat source models were used to obtain the distributions of temperature and thermal stress inside the brittle transparent materials in the separation process,thus accomplish the analysis of the separation mechanisms and proving that the thermal tensile stress generated by the laser foci is the key factor to accomplish the separation.(3)The theoretical analysis and experimental exploration of the derived multi-focus laser separating large size KDP crystal materials were carried out,and the high-quality separation of KDP crystal with thickness of 50 mm was accomplished for the first time on the world.The separation thickness of multi-focus laser is at least 4 times thicker than the existing laser separation methods of KDP crystal,and the cutting speed reached 200 ?m/s,which is at least 20 times higher than the traditional mechanical separating methods of KDP crystal.At the same time,the separation quality is extremely high,and the roughness of the separated surface reached 10.857 nm,the flatness reached 3.5389 ?m.Moreover,there is no separation defects like surface contamination,surface damage or edge damage on the separated surface.(4)The theoretical analysis and experimental exploration of flexible multi-focus laser separating glass materials were carried out,and the high-quality separation of the soda lime glass materials with thickness of 20 mm were accomplished successfully.The separation thickness of multi-focus laser separation is 2-4 times thicker than the existing laser cutting technologies,and a smooth separated surface without any micro-cracks,subsurface damage,chipping or corrugation was obtained.The roughness of separated surface reaches 1.6 nm,reaching the standard of mirror.At the same,the soda lime glass and ultra-white glass with thickness of 10 mm were separated by the same optical system with high quality,and the adjustability of flexible multi-focus laser were proved.The theoretical analysis and practical experiments proved the feasibility and reliability of flexible multi-focus laser separating glass materials.(5)The theoretical analysis and experimental exploration of multi-focus laser composite separating the laminated glass materials were carried out.This method utilize the composite separation mechanism to accomplish the one-time separation of laminated glass.For the two glass layers of laminated glass,they were separated by the thermal stress generated by the laser foci.For the PVB layer of laminated glass,they were separated by the fusion caused by the high temperature generated by laser focus.At the same time,the experiments were carried out to complete the high-quality separation of laminated glass with thickness of 5+0.38+5 mm by one-time,and the separation surface was very smooth(surface roughness of glass layer reached 10.24 nm)without any cutting defects such as micro-cracks,surface damage or breakage,etc.Moreover,this method simplified the separation processes of laminated glass from 5 steps to 2 steps,thus improved the separation quality and efficiency of laminated glass.Based on the experiments and numerical simulation analysises of multi-focus laser separating various brittle transparent materials,it was proved that the multi-focus laser separation could obtain high separation quality and simplify the separation process,which has great scientific significance and practical application prospect.