Expansion,Necking And Breakage Of Inner Pressed Cylinder Induced By Local Thermal Loading

The thermal-mechanical effect is the important content in the research of the laser breakage mechanism. The thermal-mechanical coupling breakage effects of some kinds of pre-loaded structures induced by low power laser make important meanings to the research of the laser breakage mechanism. The deformation and breakage of the cylinder with inner pressure irradiated by low power and continuous wave laser are researched in this paper from the experiment and numerical simulation. According to the experimental results, when the ratio of the inner pressure to the static-explosion pressure is equal to 0.082 or 0.157, the large deformation bulge emerges at the local thermal loading area. With the height of the bulge increasing, the global axial-cracks come into view at the climax of the bulge. From the metalographic analysis, it can be gained that before the. breakage of the cylinder, the shell undertakes larger necking deformation. The cracks at first emerge at the location where the largest necking deformation exists, that is the outer surface of the center of the thermal speckle. Then they expand to the thickness and diameter till the thermal-elastic-plastic fracture failure. When the ratio of the inner pressure to the static-explosion pressure is equal to 0.041, slight bulge appears at the local thermal loaded area. The global cracks come out at the center and edge of the thermal loaded area. But the penetration only appears at the edge of the light spot. The thermal-mechanical decoupling method is used in the numerical calculation with the large finite-element calculation program ANSYS. The deformation and stress distribution in the inner pressed cylindrical shell under the irradiation of low power laser are calculated. The calculation result shows that when P~Pb =0.082 and 0.175 the large deformation bulge firstly emerges at the local thermal loading area, then the shell begins to neck. The necking induces stress centralization in the local shell. The stress centralization makes that the hoop stress o~ in the outer surface of the center III of necking area firstly reaches the anti-stretch strength of the material in the corresponding temperature. This means that the cracks are firstly initiated in this area. The numerical simulation results conform to that of experiment.