The Dynamic Analysis On Drilling System Of ZY-200 Type Rotary Drilling Rig

Rotary drilling rig is one of multifunction and high efficiency foundation equipments.It adopts loop free craft construction bored pile, which has the merit of swiftness, pore-forming depth deep, high quality and low noise.Rotary drilling rig is being widely used on high-rise, road, bridge, power plant, airfield, large-scale port, deep-water dock and so on.It has important sense on accelerating the construct rate, guaranteeing the engineering quality, depressing engineering cost, improving performance and protecting the environment.The center of the rotary drilling rig are power unit and drilling system.The torque is generated by hydraulic power head and stress is provided by oil cylinder.The torque and stress convey to drill bit via the extension-type drill stem.Then the main hoist elevates the drill bit filling with boring mud outside the hole.The drilling system of rotary drilling rig include drill stem and drill bit.As the main component to convey the power, the drill stem should transmit the torque and power to the drill bit, and it will be occur cross banding deforming.So the drill stem must bear high pulling torque, great presser and overcome prodigious bending moment.At the same time, the friction resistance type extension-type drill stem rotating with definite speed in the hole, would generate vibration.With conventional static analysis, we can only obtain the stress instance of the drill stem at the special work condition, and incapable of gaining the kinetic characteristics of important part.The structure of drilling system is hugeness and stress complex and it is difficult to analyses with general mechanical analysis means.When the paper analyses the drilling system, reduce the drill stem to a beam as the length of the stem much greater than its radial length.The dynamic characteristics of the beam is primarily its cross bending vibration.The drilling system vibrates within one plane surface.The movement of the unit of the beam can be described with axial transversal displacement neglecting the impact of shear deformation.For the action of the oil cylinder, the ends of beam bearing the stress when working.So the units of the beam should bearing the stress besides shearing force and bending moment.The paper apply the concept of the Finite Element Method, divide one beam into some units, According to the Rayleigh beam element theory, establish the kinetic equation of the unit of the drilling system using the Lagrangian equation, and combine the equation of the units together and acquire the mathematical modeling of the drilling system.Obtain the path motion of the center of the drill bit underground according to the Runge-Kutta method.We can see that the central axis of the dill stem is no longer vertical in the course of practice drill, having an effect on the verticality of the pore-forming.It should be more analyses the transverse vibration characteristic of the drilling system, and to known its natural frequency and fundamental undamped natural mode of vibration.Secondly, the paper built five different models of different working condition in ADAMS/Vibration.And divides the drill stem into the flexibility beam element.Acquire the frequency response characteristic of the system.It can be seen that the natural frequency of the system continually depress with the increase of drilling depth.At the same time, we obtain the natural frequency and mode shape of the system of all work conditions.Comparing the exciting frequency by power unit, we can draw a conclusion that the power unit should avert some rotation rate to prevent resonance.It can be seen that the nodes of the mode shape increase with the increment of the steps.The mode of vibration behaves as multiple order buckling form.It shows strong flexibility state, the drill stem approach the down hole slides up and down, behaves as"snake"aitch mode of motion.The dill stem and drill bit will be failed if this condition can't be controlled in time.Sometime it is very difficult to adjust rotation rate for avoiding resonance when the resonance frequency range is wide. It is necessary for the operator to known the transverse vibration instance of the drilling system underground.In order to guarantee the quality and verticality of the pore-forming, they can stop and restart later after adjustment if they can't avoid the resonance frequency.The paper establish the dynamic equation of the drilling system according to the Finite Element Method, and acquire the path motion of the center of the drill bit underground using the Runge-Kutta method; built five different models of different working condition in ADAMS/Vibration, obtain the natural frequency and mode shape of the drilling system.Comparing to the exciting frequency by power unit, work out the rotate rate which can be easy to cause resonance, and it has some reference value for the operator.