Study on Bonding Failure of Single Screw Motor Shell-Bushing Interface Based on Cohesive Zone Model

As the power component of the oscillator, the screw motor often fails at the bonding interface, and the mechanical mechanism of bonding failure has not been fully studied. Therefore, this paper establishes a shell-bushing cohesive zone model to explore the mechanical behavior and failure factors of the bonding interface. It is found that the mechanical model can well simulate the bonding failure process, the error is less than 5%, and the finite element simulation results are consistent with the failure position of screw motor in Daqing Oilfield. In addition, the effects of rotor position, drilling fluid pressure, interference, wall thickness and pressure difference on the bonding interface were studied. The results show that the rotor extrusion on the bushing in the circular arc section is the main position that causes the damage of the shell-bushing interface. The interference and pressure difference are the main factors causing the bonding interface failure of the even thickness screw motor, and the position of the maximum initial damage is given. When the drilling fluid pressure is 35 MPa, the maximum radial displacement of the conventional screw motor reaches 0.37 mm, and it is not recommended to be used in deeper Wells. The interference amount has a significant effect on the initial damage of the bonding interface of the even thickness screw motor, and it is not recommended to use a large interference amount for the even thickness screw motor. With the increase in wall thickness, the initial damage of the bonding interface of the screw motor decreases linearly. The research results provide a reference for the design of fixed rotor parameters and the optimization of vulcanized bonding process.