炭酸ガスレーザによる花崗岩の熱破壊

抄録

This paper shows the mechanism of fracture formation of a granite caused by thermal stress in the case of applying the impulsive CO₂ laser beam to its surface.
The equation for heat conduction in solid according with the conditions of the laser beam irradiation is solved, and the temperature distribution in the rock for each time elapsed is calculated by making use of its thermal properties in various temperature surroundings by employing the laser flush method.
Applying the temperature distribution to the common axi-symmetric finite element method, the thermal stresses in the rock can be obtained.In this process for setting up external forces of the nodal points the ‘thermal’ Young's modulus is used instead of conventional Young's modulus.
Appropriateness of above temperature calculation is confirmed experimentally by two ways.One is to observe the distribution of the surface temperature by infra-red ray TV camera, and the other is to measure the surface displacement perpendicular to it by He-Ne laser holography.
The simulation is made for the fracture propagation with time elapsed.The Griffith theory is adopted for the evaluation of fracturing in each element mesh in FEM.
In this simulation it has become clear that the greater part of the fractured elements occurs at tensile stress region, and the fractured region caused only by the thermal stress is limited.