Dynamics Study And Optimization Design Of Impact-buffer Mechanism In GCD-1500Cable Drill

Cable percussive drill had been widely used in domestic engineering fields such aswater-well drilling, railway and road construction, etc, owning to its featuring withstrong applicability, simple structure, low cost, simple operation and other advantages.However, during the drilling process, it always existed several problems such as largeload fluctuations, noise, low efficiency and high energy consumption, as well asbuffer springs fracture. Most of percussive drills were designed by experience orsimplified formulas, it had not been considered of the influence of the coupling effectof impact linkage mechanism, spring buffer and the wire rope-percussion bit-geotechnical systems on the rig system performance, and the optimization designmethod of the percussive drill had not been proposed.In order to solve the problems above and offer theory for more perfect design ofpercussive drill, this dissertation analyzed the main fatigue causes of buffer springs,studied the influence on the drill performance of spring buffer and optimized thestructure size of the linkage mechanism with GCD-1500cable drill as the researchobject. The issues being mainly studied are listed as follows:First, fatigue analysis of the buffer spring was done on the basis of stress responseabout buffer spring during percussive drilling. The main fatigue cause of buffersprings was the system dynamic characteristics affected the spring’s response stressspectrum; the fatigue failure of once impact was equivalent to multiple stress cycle,not just one pulse stress cycle based on traditional fatigue design of buffer spring.Second, on the condition of various bore depth, the buffer spring’s stress responsewas analyzed to predict fatigue life of the spring. The fatigue damage of buffer springwould be increased by a single impact, and fatigue life would be shorten with theincrease of the bore depth. Especially on the condition of “idle impact”, buffer springwas damaged severely，which should be avoid.Third, the models of spring buffer with different preload were built to analyze theinfluence of preload on the modal frequency of the system, the movement ofpercussion bit and input power of the drive motor. A large preload force(F=34590N)of spring buffer could reduce the interference of impact mechanism movement on thewhereabouts of percussion bit, improve impact velocity, and avoid negative torquedamage motor, enhance drilling efficiency. Moreover, a large preload force could avoid impact load action on buffer spring while the wire rope was tightened suddenly,so as to prolong the fatigue life of spring.Finally, the parametric model of cable percussive drill was built. Differentobjective functions were selected to optimize impact linkage mechanism. Under thesame conditions of impact velocity, impact linkage mechanism was optimized bytaking the root mean square of impact gear torque as the objective function, whichwas more reasonable than single-objective optimization, and had some degree ofguiding significance in optimization design of percussive drill.By all the works mentioned above, this dissertation studied the influence ofspring buffer system and impact linkage mechanism on the dynamic characteristics ofthe rig system, and exercised the structural optimization design of impact linkagemechanism, which provided reliable parameters and systematic methods for thesystem dynamics research, buffer spring reliable design and optimization design ofpercussive drill.