| The technique of diamond wire-line taking -coring drill has been applied in China for more than 30 years. The drill process and operation rules have been formed completely. But the construction and strength of the wire-line taking -coring drill (for convenient, it will be called W.T. Drill) are kept original level:low strength of the drilling pole, short life of application, bad reliability, high accident rate in deep drilling, occurrence of drilling pole breaking accident. It can't satisfy mineral exploring drilling. For adapting the demand of the mineral exploration and the future development, reducing the difference with the developed country, we applied the pole and joint thread of W.T. Drill as our study objectives, studied theoretically and experimentally of their construction dimension and geometrical parameters, established the mechanics model, realized the optimized designation, applied and extended our research results into engineering, made designation and application of W.T. Drill in our country to be a higher level. (一),Main content and achievement of this study The pole and joint thread were studied deeply based on static Finite Element theory. The boundary condition of the FE model was defined, and then external load were calculated under the real work conditions. On base of these conditions, static 3D Finite Element model was built. The construction characters and failure modes of three joint modes between the pole and joint of the W.T. drill (include the integrated type with coarse ends of drill pole, both ends with thread joint type, both ends with friction or electric welding type, illustrated in figure 1.1) were analyzed and compared. The construction dimension of the real model for the Finite Element analysis was defined. Stress, strain and displacement field of the drill pole and joint thread under the working condition were simulated. The factors of life -limit of the pole were found. The joint thread of the drill pole was analyzed elaborately based on nonlinear contact Finite Element theory. The international FE software was applied, nonlinear FE model was built, the stress and strain of joint thread with different construction parameters were simulated and calculated, the distribution of the stress field and stress displacement field of the key part were obtained, deformation, destroy and failure of the thread were analyzed. On base of all of these studies, the formation parameters of the joint thread were optimized. The Von Mises Stress in the forth strength theory was regarded as the standard target, and the most optimized parameters were found in these way. The strength of the drill pole and the reliability of the joint thread were improved. The construction parameters of the joint thread include pitch of the screw, outer diameter of the screw thread, height of the thread and the taper. The samples of the optimized joint thread were checked by the limit –strength comparison experiments. The results show that the joint strength and reliability are improved obviously. The experimental results match the simulated results very well. The formation of the thread and the construction parameters were defined depend on our simulation, optimization and experiments at last.(二),Main conclusions of this study The distribution of the stress field and strain of the joint thread and drill pole area were observed and analyzed. The stress and strain with different construction parameters were simulated and analyzed at the same time. The Von-Mises stress in the forth strength theory was the main standard to define the most optimized parameters, following conclusions were obtained: 1. The main life-limit factor of the drill pole is that the local area of the joint thread area is under the high stress situation obviously at the normal work condition. The local area of the joint thread should be regarded as the key point in the following study. 2. The maximum stress was reduced 27 percent by optimizing the thread construction parameters (pitch of the screw and the total distance); the optimized parameters are: the pitch of the screw 10mm, the total distance 57mm. 3. The external diameter of the thread was changed from 90mm to 92mm, the maximum stress was reduced 26%. 4. The relationship between the height of the thread and the maximum stress is quite complex. The maximum stress is increased irregularly with the increase of the height of the thread. The maximum stress become stable with the decrease of the height of the thread; the height of the thread was confirmed as 0.85mm or 1.0mm according to the FE simulation results and the evaluation of the effect factors of the thread stress. 5. The effect of the taper alteration on the strength is very light. When the taper increased to 1/15, the maximum stress increased, which lead to the decrease of the construction strength, and possible decrease of the life of joint thread; the value of the tapershould be keep in a relative reasonable range; the range of the taper should be 1/30 ～1/22. (三),The application, extend and significant of this study Construction parameters of the W.T. Drill were defined finally, which depend on strength design theory of the drill pole cross -section, simulated analysis results by applying the Finite Element Method and our mechanical experimental on joint thread. The blueprint of W.T. Drill samples were designed and drawn, the samples of the W.T. Drill were trial manufactured. The samples were checked by different experiments, such as manufacture experiment, reliability experiment, application life experiments and so on. All the targets were satisfied or exceeded our demands. The company who applied the samples gave us a very high evaluation. Five sets of S95 W.T. Drill were trial manufactured and applied. The total quantity of experimental drill was 4600m, 10 exploring hole and 6500m were drilled accumulatively. The results of the experiments show that the strength and the life of the drill were improved and reached our optimized targets. The results of this study was applied and expended by Wuxi Ore Exploration Tool Factory Of The Ministry Of Land And Resource from March to October 2005. The new increased production value is 2 million Yuan, and new profit tax is 400 thousand Yuan. Simulated computational model was built basically in this study. The model can be applied in simulation and optimization of the W.T. Drill, and the results are exactitude. It can be applied in manufacture to create more profits. This study shows: to choose the different parameters of the joint thread is the best and the most economic method to improve the strength of thedrill pole. This study combined the modern CAE and testing technology, it can reduce the period of the research and optimization, improve the cognition of the failure mechanism of the drill pole. The perspective application and field are broad. In this study, the theoretical analysis and the simulated optimization on the designation were completed. The completed methods to analyze the integrated drill pole were built. The modern CAE were applied in construction optimization of the W.T. Drill. The improved drills were applied in real manufacture. We didn't find this kind of series studies domestically. This study is creative. The theoretical study here is elementary, more questions need to be discussed and researched more deeply. This study of the strength of the drill pole is based on structure statics. But the work condition of the drill pole is very complex in the real case. It is affected by alterative stress and fatigue. If the real work conditions are expected to be simulated, we need to build precise mathematic model to realize the numerical calculation. More precise studies need to be made deeply, and more scientists need persevere to put their efforts.
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