Study On The Theory And Method For MR Intelligent Boring Bar With Self-Chatter-Suppression

The chatter always occurs in precision hole boring process, which is one of the main abnormal cutting conditions that influences the quality of workpicece. To solve this problem, the cutting chatter suppression in boring process was studied systematically in this dissertation . The research work is supported by the National Natural Science Foundation of China (Grant No. 50405036), "Research on the Theory and Method for Intelligent Boring Bar with Self-Chatter-Suppression Based on Magnetorheological Fluid ", and the Natural Science Foundation of Zhejiang Province (Grant No. Y104462), "Research on the Theory and Method for MR Intelligent Boring Bar with Self-Chatter-Suppression". And the rearsearch work was carried out by combining theoretical analysis, numerical simulation with experimental verification.In Chapter 1, the background and significance of the research were introduced, the development trend and current research situations of the technology of cutting chatter suppression were expatiated, then the research contents of this dissertation were proposed.In Chapter 2, the dynamic model of regenerative chatter is established, which is the main type chatter in boring process. Then, the chatter suppression mechanisms of variable speed cutting method was analyzed. Lastly, the variable structural stiffness method of chatter suppression was proposed. By comparing, it was found that the chatter suppression mechanism of variable speed cutting method is similar to variable structural stiffness method.In Chapter 3, a MR intelligent boring bar with self-chatter-suppression was proposed, whose stiffness and natural frequency are controllable. The structural parameters of MR chatter suppression unit was optimized, which is the key part of the MR intelligent boring bar. Lastly, the optimized results was validated by finite element analysis, and the simulation results show that the main performance of MR intelligent boring bar meet the design requirments.In Chapter 4, firstly, the stiffness and damping of MR intelligent boring bar were tested by static loading method, and the results show that the static stiffness and damping will increase obviously when the magnetic intensity increased. Secondly, the variable laws of the system stiffness and damping were investigated by transient exciting method by applying different magnetic intensity, and the results show that when the magnetic intensity increased, the stiffness of MR intelligent boring bar will increase monotonously, while the damping will firstly increased and then decreased. Thirdly, the intelligent boring bar was tested by steady state exciting method, and the results show that the system dynamic characteristics are influenced by vibration amplitude, frequency and magnetic intensity. Lastly, the dynamic response time of MR intelligent boring bar was tested.In Chapter 5, the constitutive model of MR fluid was established on the basis of Kelvin model and Maxwell model, and the results of numerical analysis show that the model can describe the MR fluid's dynamic characteristics accurately. Then, the dynamic model of MR intelligent boring bar was established based on the constitutive model of MR fluid, and its characteristics was analyzed by Lagrange equation. To meet the requirement of real-time control, a dynamic model of MR intelligent boring bar based on Bouc-Wen model was proposed. Then, the parameters of model was identified by nonlinear least square method. Lastly, the numerical simulation of the model was carried out, and the results show that it can discribe the dynamic characteristics of MR intelligent boring bar accurately.In Chapter 6, according to the characteristics of chatter development process, the boring process can be divided into two cases. On this basis, the nonlinear stochastic optimal semi-active control strategy and the varying stiffness semi-active control strategy were proposed respectively. Then, the control law of nonlinear stochastic optimal semi-active control strategy was derived, and the numerical simulation analysis was carried out. Lastly, the control parameters of varying stiffness semi-active control strategy was optimized by way of the theory analysis, and in addition, the numerical simulation was carried out.In Chapter 7, to verify the theory and method mentioned above, the experimental setup of MR intelligent boring bar was built on the CA6140 type lathe. A series of experiments were carried out, and the results show that the method can suppress chatter efficiently and surface quality of workpiece can be improved significantly.In Chapter 8, the chief work and innovations of this dissertation were summarized, and the further research subjects were proposed.