Dynamics Analysis Of Downhole Drilling Drill Rod

Drill rod is one of the largest consumption and important "power transmission system " in underground drilling work. Its service behavior and useful life have been the most favorite performance index.The working states of the drill rods are extremely complex. Under the harsh environment, drill rods have to suffer huge-cycle form the piston and torques from drilling,but also corrosions from mineral water and rock resistance. The approaching of the shock frequency of the drilling to the drill rods’ nature frequency will lead to the resonance effect,and a serious distortion in the radical direction. The huge impact of moment also rends huge tension and compression stress in lengthwise direction. These can easily affect the useful life and service performance of drill rod, especially when the resonance and the high strength impact happen at the same time. To solve these issues,the thesis did following research works :(1) An analysis of the instant drill rod impacted by piston theoretically is acted, and the stress wave propagation process of transmission in the interface between the drill rod and piston. YGZ- 90 mode drilling, for example, it worked out the time history of incident stress wave when matching with H35 hollow hexagonal screw thread connection brazing of drill rod is, according to the stress wave transmission and reflection theory and regularities between the drill rod and the piston collision.(2) Based on ANSYS platform.The drill rod is analyzed from the view of the resonance in failure reasons. Throw the finite element simulation analysis,the first sixth order natural frequencies and the corresponding vibration mode under the natural frequencies are got in the example of a drill rod with a length of 2105 mm. For different lengths of the hollow hexagonal threaded drill rod, the modal analysis is carried on, through these, it gets an relationship between the length and different length of drill rods’ natural frequency. Through the harmonic response analysis, response peak is calculated when the structure is under the dangerous frequency, and also the degree influenced by each order natural frequency of drill rod. These provide a certain basis for drill impact frequency and natural frequency of the drill rod matching and avoiding the occurrence of resonance phenomenon in actual drilling work.(3) Analysis of the reason of the fraction in terms of kinetics is done here. By LS-DYNA simulation software, matching an H35 hollow hexagonal threaded drill rod with a length of 2105 mm with YGZ- 90 drill impact dynamics, the analysis of the drill in two extreme working conditions(fixed end reflection and free end reflection) is acted. It will present the progress of the generation of stress wave and stress wave propagation in the drill rod when impacted once by double cylinder, and the part of the drill most prone to fail in drilling process. Analyzing the stress distribution of the drill and comparison with the scene sampling, proved the simulation analysis roughly consistent with the actual site, and the dynamic analysis done to the drill is feasible.