Optimization Analysis on Strength of Run-through DTH Hammer Reverse Circulation Bit Based on LS-DYNA

Abstract:

The reverse circulation bit tail of spline DTH hammer is easily broken when drilling into extremely complex strata, such as hard, brittle and fragile ones. The structure design of reverse circulation bit tail was optimized to prolong the service life, and the simulation analysis was conducted on the reverse circulation bits before and after improvement by nonlinear dynamics simulation software LS-DYNA. It shows that due to the high-frequent impact force of hammer, the reverse drill bit tail is prone to having a big local stress concentration which causes fatigue rupture to the bit body. With the optimization of bit tail structure design, comparing with spline reverse circulation bits, the stress concentration of this new-structure bit decreases by 44% and 19% respectively under the conditions of without or with vent duct. Numerical simulations show that the bit service life can be greatly increased by optimization.

Key words:run-though reverse circulation bit; LS-DYNA; stress concentration; structure optimization analysis