Research On Mode Shapes-dependent Dominant Vibration Characteristics In The Processing Of Thin Plate Workpiece

Thin-walled parts are widely used in the equipment manufacturing industry in the fields of aerospace,energy,and marine engineering due to their light weight,strong flexibility,and the ability to manufacture parts with complex structures.However,due to the low rigidity of thin-walled parts,vibration or even chattering is easy to occur during milling,which seriously reduces the surface quality and accuracy of thin-walled parts.The current research work on machining vibration in the milling process of thin-walled parts mainly focuses on the stability analysis of the milling process and chatter suppression,but little attention has been paid to the contribution of each order mode shape of thin-walled parts to the vibration during the machining process.By analyzing the contribution of each order mode shape of the thin-walled parts in the machining process,it is helpful to obtain the suppression strategy for the processing vibration of thin-walled parts according to the characteristics of the dominant mode shapes.This article focuses on the vibration characteristics of thin-walled parts such as thin plate workpiece in the milling process,mainly from the identification of modal parameters of thin plate workpiece,the influencing factors of the dynamics characteristics of thin plate workpiece under tool contact,and the dominant vibration characteristics in the milling process of thin plate workpiece to conduct the research.The research results show that the mode shapes of the thin plate workpiece under different processing positions are different,the dominant vibration modes and the dominant mode shapes are also inconsistent,but the amplitudes of operational deflection shapes are consistent with that of the dominant mode shapes.Firstly,the dynamic parameters of the thin plate workpiece are analyzed.The first four order deformations of the thin plate workpiece are obtained by ANSYS finite element modal simulation analysis,and then the first four order mode shapes of the thin plate workpiece are obtained through experimental modal analysis.Finally,analysis of the mode shapes of the thin plate workpiece with five wall thicknesses is carried out.The simulation and experimental results provide a comparison for the subsequent analysis of the influence of the change of boundary condition under the tool contact on the modal parameters of the thin plate workpiece.Secondly,since the influence of the tool on the dynamic parameters of the thin-walled parts was not considered in the existing researches,the dynamic parameters of the thinwalled workpiece under the contact of the tool will be analyzed.It mainly analyzes the changes of the dynamic characteristics of the thin plate workpiece under several factors such as whether the tool is in contact with or not,the thickness of the thin plate,and the different contact positions of the tool,especially the influence on the mode shape.The results show that the contact position of the tool has a great influence on the mode shapes of the thin plate workpiece,which lays the foundation for the subsequent acquisition of the dominant mode shapes.Finally,the dominant vibration characteristics of the thin plate workpiece under milling at different positions are analyzed.The dominant vibration modal is extracted from the multi-point vibration response signals at different positions by Operational Deflection Shapes method,and the dominant mode shape is obtained based on the dominant vibration modal and the mode shapes under different milling positions.The relationship between the operational deflection shapes and the dominant mode shape has been explored,the experimental results of milling experiments with different machining parameters demonstrate that the amplitudes of operational deflection shapes are consistent with that of the dominant mode shapes;because the Operational Deflection Shapes method requires multi-point vibration signals,an online dominant vibration modal identification method based on the combination of Kalman filter and the state space equation is proposed.This method only requires the vibration signal of one point on the thin plate workpiece;the result shows that the dominant vibration modal of the thin plate workpiece obtained by the two methods are consistent.The research of the thesis provides an idea for vibration suppression in the processing of thin-walled parts.By suppressing the dominant mode shape,the vibration suppression at the position with large vibration amplitude in the processing position-dependent operational deflection shapes can be achieved.