Research On Dynamic Characteristics Of Rotary Drilling Rig Drill String And Nonlinear Energy Transfer Vibration Damping

Rotary drilling rig is a kind of widely applied construction machinery, and has awide adaptability and good environmental protection. Drill string is a key componentto determine both performance of rotary drilling rig and quality of hole. So it is veryimportant to study of this component. This dissertation focused on dynamiccharacteristics of drill string and nonlinear energy transfer vibration damping in rotarydrilling rig.In this dissertation, dynamic characteristics of drill string were studied, and lotsof influence factors were considered, such as coupling torque-bending, external andinternal damping, transverse mud force, coupling compression-bending, and so on.Based on the boundary conditions of drill string working, and to exert torque on thedrill string, the dynamics of partial differential equations are established. The finitedifference method is applied to calculate the equations, and to obtain numericalresults. The variation laws of the side-force and its phase at the bit and the power unitare analyzed under the different influence factors. By the simulation results showed,the distribution mass is relatively large influence on force of on drill string.Based on the forced character and nonlinear feature of drill string, the forcedequivalent model is established. Dynamical differential equations are derived.Model’s equations of motion and nonlinear responses on relational boundaryconditions are obtained by the variational method. Applying nondimensionalization,precision buckling of model is solved, and obtained natural frequencies and modeshapes of drill string as the function of exerting axial load. Bending deflections ofdrill string can be calculated. Subsequently, model linear vibration problem is solved.Through analyzing parameters, it is can be determined that drill string produceinternal resonance in the change of the load which drill string bearing. The internalresonance between the first mode and the second one is studied. Applying the multiplescale method for the theory analysis, to check whether nonlinear coupling between thefirst mode and the second one. By the numerical simulation, periodic orbits of twotypes mode action are obtained, and numerical results of energy transfer between twomodal are showed, in the same exciting grade and different boundary conditions.The model of drill string installed the nonlinear energy absorber (NEA) is builtand analyzed. Considering integrated damped beam-NEA system, its transientresponse is numerically computed by projecting dynamics of the partial differential equation in the functional space defined by the complete and orthonormal base ofnatural modes. The linear parts is separated and the target energy transfer is quantified.By the numerical simulation results indicating, an appropriately designed and placedNEA can passively absorb and locally dissipate a major portion of the energy inducedand irreversible, as verified by the significant levels of energy eventually dissipatedby the damper of the NEA.For drill string end producing oscillation in process of cutting, vibration dampingis researched in drill string end with nonlinear energy absorber. The interactionsbetween drill string and absorber have been researched by the combination ofnumerical conversion. Observations main resonance mode interaction between thecontinuum and the nonlinear energy absorber that controls energy transfer by higherharmonic wave. By frequency-energy plot (FEP), an appropriate transformationprocess is realized in transient attenuation. This process was decomposed by empiricalmode decomposition. Within the different characteristic time (or frequency) field, theresulting time-series were decomposed by intrinsic mode function. In the differenttime interval, the transient frequencies of main intrinsic mode function were analyzedfor nonlinear energy absorber and responses of bar end. Transient resonance capturesof intrinsic mode functions control energy transfer between nonlinear energy absorberand drill string end. At same time, it also verify that locally add to a nonlinear energyabsorber influencing on the dynamic of overall system. By analysis, there is toprovide a strong guidance for practical application of nonlinear energy absorber.At last, a vibration damping test of drill string end with a nonlinear energyabsorber was designed. The test results show that the effect of vibration damping isquite obvious, and so, the theory of vibration damping in the drill string above istrue. It’s a new way to solve drill string vibration damping.