受内压厚壁圆筒的塑性变形条件与脆断分析

The plastic deformation condition of a thick-walled cylinder subjected to internal pressure is analyzed based on the idea of elastic constraint, and it is found that the fundamental reason for brittle fracture of a thick-walled cylinder is that the high stress zone on the inner wall of a cylinder is restrained by the low stress zone on the outer wall, and the plastic deformation cannot be generated freely when the stress state reaches the yield condition of the material. Through theoretical calculation, the wall thickness design and material selection of internal pressure pipeline are given to avoid the occurrence of brittle fracture. Results show that, for different types of pipeline steels with external diameter 2b=300mm, the critical wall thickness decreases from 62.2mm to 12.9mm, and the limiting internal pressure decreases from 225.2MPa to 69.0MPa as the ratio of yield strength and tensile strength increases from 0.51 to 0.91. That is, the lower the ratio of yield strength and tensile strength of the selected material, the larger the range of the wall thickness size without brittle fracture, and the higher the ultimate bearing capacity of the pipeline within the range of the critical wall thickness. Therefore, the use of materials with lower ratio of yield strength and tensile strength and the control of reasonable pipe wall thickness can make the pipe absorb the impact energy with overall plastic deformation, when it is subjected to unexpected impact internal pressure, so as to avoid the brittle fracture of the pipe.