Study On The Fracture Mechanism And Optimal Design For The Large Diameter Step Impact Drill

The large-scale step impact reverse circulation rock drilling performs an important function on the current bridge construction, water conservancy facilities, especially high-speed rail projects in the pile hole construction.Playing a non-optimized design according to the small drill simply and non-canonical manufacturing process are the primary cause for the fracture of the drill.In this paper,the force for YCJF-25-type impact drill is studied. Based on the establishment of the three-dimensional entities and the force model, the depth research for stress field and vibration mode of the large diameter drill is maded.The stress distribution and vibration characteristics are proved for the drill structure.The relation between the structure parameters of the drill and the stress distribution, the macro-scopic mechanical causes for the drill failure are studied.The research shows that there is a certain correlation between the drop height and drop frequency.Improving the drop height is more conducive to increasing the impact energy of the drill than improving the drop frequency. In this paper, the modal analysis is carried out for the large-diameter step impact reverse circulation rock drilling,the modal analysis map is gained.The damage influence for the bit of the drop frequency and natural frequency is studied.The structure optimization design scheme for the large-scale step impact reverse circulation rock drilling is brought up,in order to reduce stress concentration and optimize the drill bit modes, hereby improving the bit strength and extending its life. The results can provide a theoretical basis for the design of the large diameter drill bit.There is a certain theoretical and engineering application for improving the life of the bit.