Controlled-fracture of prescored alumina ceramics using simultaneous CO2 lasers

Abstract

While brittle materials such as ceramics will clearly be at the forefront of improved energy efficiency, manufacturing problems related to shaping have proven to be troublesome. Fortunately, the usage of laser machining to shape structural ceramics is increasingly gaining acceptance as an alternative to traditional grinding and cutting methods. Despite the great promise of lasers for a variety of cutting and drilling procedures, premature fractures, poor surface quality, microscale damage, and prohibitively low cutting-speeds are still among the greatest obstacles, especially as the thickness is increased. While many factors contribute to the fractures encountered during laser machining, it is the inevitable and localized increase in temperature and the ensuing thermal stresses that usually cause the damage. As such, the minimization of heat buildup and the resulting thermal stresses often requires the slow and expensive practice of multiple pass or interrupted cutting or drilling. To help control fractures and allow faster machining, a unique method of simultaneously scoring and cutting known as “prescoring” was explored using alumina plates. This concept has now been used to refine the “controlled fracture” approach, where thermal stresses are used to drive a propagating crack along a preordained path using simultaneous CO2 lasers. Using this technique and a systematic design of experiment approach to investigate the effects of various parameters, the use of the dual-beam technique was shown to be capable of predictably controlling fractures in relatively thick alumina plates. In addition to providing a clean fracture surface, this method was also shown to be capable of machining these specimens faster and with less energy input than other laser machining procedures will allow.

Temperature distribution and thermal stress in glass irradiated by dual CO 2 lasers

“…It is inefficient to use furnace to heat the glass. A feasible method to reduce thermal gradients is preheating glass by CO2 laser before machining, that is the process of manufacturing glass with dual CO2 laser beams is briefly illustrated [13,14]. The preheating laser beam preheats glass to a proper temperature, which can reduce the thermal stress in glass when machined by machining laser beam.…”

Numerical investigation on machining glass with CO2 lasers

“…One is the controlled fracture method and the other is melting means. The former has attracted more attention and lots of research has been reported in literatures [7][8][9][10][11][12][13][14][15][16]. In contrast, very few studies have been made in detail to investigate cutting glass with the melting method except by Chui [17], due to the low thermal conductivity and the brittleness of the glass material.…”

“…With the development of laser technology, many studies have been carried out on cutting glass with lasers [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Li et al [3] put forward a mathematical model to explain the heat transfer of glass heated by a laser beam.…”

Laser cutting of sharp edge: Thermal stress analysis

“…They used a fixed grid algorithm to model the ablation process and the model developed was integrated with a probabilistic fracture model to assess the failure probability during the laser cutting process. Brugan et al [9] introduced a new method to control fractures for the fast laser machining of lamina plates. They accommodated the simultaneous scoring technique to enhance the thermal stresses for driving a propagating crack along a pre-ordained path using simultaneous CO 2 laser.…”