圆螺纹套管接头的抗压缩极限载荷分析

采用非线性有限元方法，以API8牙圆螺纹套管接头为研究对象，在标准锥度公差条件下，模拟套管接头的上扣过程，计算分析上扣过程中内、外螺纹导向面和承载面上的应力分布，并对套管接头在压缩工况下的承载极限进行分析，得到套管接头在压缩载荷下的失效形式，失效载荷，并提出相应的失效判据。

CRITICAL COMPRESSIVE LOAD ANALYSIS OF CASING CONNECTION WITH ROUND PROFILE THREAD

The critical compressive load analysis was performed for API 8 casing connection with round profile thread, and the casing make-up process under standard fit tolerance was simulated using nonlinear finite element method. The stress and strain distributions over guiding flank and loading flank of box and pin thread were calculated to determine the failure criteria of casing connection under axial compression. Under make-up torque and axial compressive load, stresses of pin thread are greater than those of box thread. The most critical part is on the root of the first two fitting teeth of casing connection. According to this fact, the critical load at which the connection is failed can be determined by the rate of total equivalent strain of pin,that is, as the total equivalent strain of the section of the first fitting tooth of inside surface of pin increases smoothly with axial compressive load to a maximum value, the corresponding load is treated as critical load. Using the criteria proposed in this paper, the failure pattern and failure load of casing connection were obtained, and the results demonstrate that the critical compressive load can be slightly increased by increasing makeup torque.