Quantifying Stress Concentration Factors and Structural Yield Limits in 3D PDC Drill Bit Model with Finite Element Analysis

In petroleum drilling operations, optimizing weight on bit (WOB) is critical for structural integrity and economic bit life. This study developed a 3D numerical model of a 17½-inch Polycrystalline Diamond Compact (PDC) drill bit and analyzed its mechanical behavior under WOB levels of 5, 12, 19, and 22 metric tons using the Finite Element Method (FEM) in Ansys software. Considering the bit’s complex geometry, the upper connection shank cross-sectional area (Ashank = 155,170 mm2) was used to convert field load data into axial pressure. The alloy steel body and PDC cutters were evaluated separately. As expected from the linear-elastic assumption, Von Mises stress results showed a proportional linear increase with increasing load. For the drill body, minimum and maximum stresses were 20.93 MPa and 89.86 MPa, remaining well below the material’s yield strength (800–950 MPa) and confirming elastic behavior with a high safety margin. For PDC elements, minimum and maximum stresses reached 21.36 MPa and 82.35 MPa, with stress concentrations localized at the cutter base interfaces. Given the high material strengths of alloy steel (σy = 950 MPa) and PDC cutters (~6000 MPa), operational stresses remained within elastic boundaries, while revealing a significant localized geometric stress concentration factor (Kt ≈ 64.65) at cutter-pocket transition interfaces.