| Turning chatter is a very harmful phenomenon in the process of metal cutting.It is a selfexcited vibration that seriously affects the quality of the machined surface.It is a very strong relative vibration between the tool and the workpiece in the process of metal cutting.Turning chatter seriously restricts the efficiency and machining accuracy of cutting.Scholars at home and abroad have made in-depth research on the formation mechanism,flutter monitoring and flutter control,especially in the aspect of flutter control,a variety of methods have been adopted to suppress flutter,such as variable parameter cutting,increasing the rigidity and damping of the added bed and a series of measures.Ultrasonic vibration turning is a kind of compound machining method,which has a certain effect on cutting chatter.In this thesis,ultrasonic vibration turning will be used to study the influence on turning chatter stability.The main research contents are as follow:(1)The dynamic model of the single degree of freedom regenerative turning chatter system is established,and the expression of the limit cutting width is finally obtained,and the blade chart of turning chatter stability is drawn,and the factors affecting turning chatter stability are compared and analyzed.According to the obtained system dynamics equation,the MATLAB/Simulink simulation platform is established to simulate the turning process in time domain.(2)Introducing the principle and characteristics of ultrasonic vibration turning,and analyzes its unique intermittent cutting characteristics.According to this characteristic,the influence of ultrasonic vibration on the energy intake of the system is studied,and the factors influencing the net cutting ratio are analyzed.(3)Based on the finite element analysis of the tool holder system of ultrasonic vibration turning,the natural frequency and mode shape are obtained.Then,the modal analysis of the tool holder system after the introduction of ultrasonic vibration is carried out to study the effect of ultrasonic vibration on the natural frequency and mode shape of the tool holder system,and the influence of the change of the natural frequency on the turning chatter stability is analyzed.(4)The turning vibration experiment platform is built.The vibration experiment of 304 austenitic stainless steel is carried out in the semi finishing range.Under different cutting conditions,the ultrasonic vibration turning experiment is carried out by comparing the ordinary turning.The acceleration signal at the tool tip is collected for frequency-domain analysis and the surface shape and roughness analysis of the workpiece.The main body of the chatter is determined and the chatter stability of the turning by ultrasonic vibration is studied At the same time,the influence of different cutting parameters and ultrasonic vibration parameters on the action effect is analyzed.The influence theory of ultrasonic vibration on turning chatter stability is verified(5)Finally,the same turning vibration experiment is carried out for 45 steel,and the influence of ultrasonic vibration on the turning chatter stability under various cutting conditions is studied,and the same effect is obtained. |
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