| Popis: |
For the polycrystalline diamond compact (PDC) bit, the first step of rock breaking is to press the bit into the rock. However, it is very difficult to theorize the pressing process, due to the complex structure of cutting tooth, the large deformation of the rock, and the nonlinearity of the cutter-rock contact. To solve the problem, this paper takes the parabolic Mohr strength criterion as the judging condition of rock failure, and establishes a numerical simulation program for the pressing process based on the arbitrary Lagrange-Eulerian (ALE) method and the general contact algorithm. The proposed program can adjust the mesh of the rock automatically, preventing the grid distortion caused by rock deformation and contact nonlinearity. The finite-element model created by the ALE method was analyzed by explicit dynamic algorithm, and the stress and strain fields of the PDC cutter were obtained by solving the model. In addition, the author analyzed how the weight on the bit (WOB) is affected by the diameter and back rake angle of the PDC cutter, as well as the friction coefficient between cutter and rock. The results show that the WOB increases with the increase of PDC cutter diameter, the WOB increases with the increase of dip angle in the range of 0–30°, and the WOB increases with the increase of friction coefficient. The established program fully reveals the interaction between PDC cutter and rock in the pressing process, facilitating further analysis on the rock-break mechanism of the PDC bit. |
