Study on fatigue life prediction of drill pipe for mine drilling

At present, it is difficult to predict the fatigue life of mining drill pipe in the coal mine, and there is no scrap standard and scrap basis, which leads to the frequent occurrence of drill pipe fracture accidents in the coal mine and seriously affects the safety and construction progress of exploration drilling, gas extraction drilling and water exploration drilling in the coal mine. The working conditions of mine drill pipe are complex, so the fatigue life, fracture failure reason and optimization of structure and technology of drill pipe cannot be studied reliably based on elastic-plastic mechanics. In this article, through comprehensive drill pipe by torque, bending moment and axial force and shaft under complex load conditions, such as the constraint force of drill pipe constraint model is established, based on fracture mechanics and damage mechanics using the analytic method and finite element analysis method to study the fatigue life of drill pipe, and based on the research and development of the drill pipe dynamic performance testing system to test the fatigue life of drill pipe, put forward the mine drill pipe fatigue life prediction methods, provide the basis for the design of the drilling and drill pipe. The results showed that, in accordance with the existing pipe rod body, screw thread processing technology, the type 73 drill pipe in 4 000 N·m, construction drilling end hole diameter of 96 mm, through the drill pipe dynamic performance test system for testing the fatigue life of drill pipe, drill pipe fatigue life of 5.32×105～4.78×105 revolutions, fatigue life and fatigue life prediction of drill pipe model is consistent, drill pipe fatigue life of the minimum position in the male thread, rod body under by 1 mm scratch can not influence the whole fatigue life of drill pipe.