Investigation On Dynamic Characteristics Of TBM Gripping-Thrusting-Regripping Mechanism And Experimental Study Of The Reduced-Scale Test Bench

Aiming at the requirement of national independent research capability of tunnel boring machine,the thesis investigates the kinematics,statics and dynamics modeling method of the gripping-thrusting-regriping mechanism of the open tunnel tunneling machines.The outcomes may provide important support for the mechanical design and engineering construction.The main contents are as follows:Kinematic characteristics: Based on the analysis of the working principle,the topological structure of mechanism is investigated in detail,and the degree of freedom of mechanism is calculated under different conditions by improved G-K formula.The criteria of topological structure design are established under the strong impact rock-breaking load conditions.The kinematic model of the mechanism is established by using the vector approach,and mapping relationship between the given trajectory and cylinder displacement is analyzed by the simplified equations.Finally,taking the circular trajectory as an example,the variation of turning radius versus the cylinder displacement,shield and machine length is analyzed.Stiffness modeling: Combining the engineering accuracy and solution efficiency,the static stiffness model is established by taking into account the stiffness of the main beam,surrounding rock support interface and hydraulic cylinders.According to the strain energy equivalence principle,the main beam stiffness model is established.The stiffness model with the rigid main beam is established.Then,the overall static stiffness model of the mechanism is obtained by the superposition principle,and its validity is verified by finite element simulation.Finally,taking the engineering prototype parameters as an example,variation of the stiffness versus the tunneling distance is investigated,and influence of the stiffness on the adjustment accuracy is also studied as well as the contribution of the main beam stiffness.Dynamic modeling: A coupling dynamic model is proposed by considering several elastic factors such as surrounding rock,supporting units,hydraulic cylinders,main beam and motion pair.During modeling,the main beam is sperated into rigid segments by the finite segment method.According to the topology among the components and mass distribution,the lumped parameters and relevant generalized coordinates are determined,and relative displacement equations among the lumped-parameters are established.The dynamic equations of each component are established by Newton-Euler method.The rock-breaking load is calculated by considering roller cutter load,shield friction and rear system resistance.Natural characteristics: The natural characteristics during a period are studied based on the frequency equations by using the practical parameters,and the influence factors on the lower order natural characteristics and their sensitivity are also analyzed.The first six orders free-vibration modes and corresponding frequencies are obtained by the numerical simulation.The modal transition resulting from the increase of tunneling distance is also investigated.To validate the effectiveness of the model,the simulation is carried out through SAMCEF.The influence of stiffness,inertial and dimensional parameters on the low-order frequency is analyzed.The sensitivity equations of natural frequency to the main parameters are established by differential equtions directly.It is concluded that the stiffness of propel cylinders and cutter-head support unit are the main factors affecting the natural characteristics.Dynamic response analysis: According to the rock-breaking load spectrum,the rock-breaking load time history is simulated by considering the cutter-head rotation frequency and meshing sequence,and the dynamic responses are derived by the numerical method.The results indicate that the first four operating modals are the vibration of the whole mechanism,which is validated by the finite element simulation.The vibration energy analysis is implemented with different lumped-parameters and modes,respectively.The influence of damping on the vibration energy is studied by divided the damping matrix into a combination of proportional,structural and viscous damping.The response sensitivity to the parameters is studied by the derivation of the dynamic equations.Based on the operational modal results,the simplified model is established by reducing the lumped-parameter numbers and simplifying the coupling relationships of the generalized coordinates.The natural characteristics and dynamic response of cutter-head are calculated and compared with the original model.Dynamic experiment of the reduce-scaled test bench: According to the relationships between the rock-shield contact stiffness and pressure of surrounding rock,the surrounding rock simulating mechanism of the test bench is improved by adding disc-springs into side-shield cylinders to confirm the nonlinear characteristics,the natural frequency test during a period and dynamic response test with different duty parameters are implemented through LMS software,respectively.The results show that the test results are in good agreement with those of the simulation,which proves the effectiveness of the proposed dynamic modeling approach.Meanwhile,the test bench provides a technical platform for the prototype design and duty parameter selection.