Modeling And Stability Study On Micro Milling Force Of Titanium Alloy Circular Arc Thin-walled Parts

In recent years,with the rapid development of aviation,aerospace,biomedicine and other fields in China,the application of small-sized titanium alloy precision components with arc thinwalled features has been increasingly widespread.The micro milling technology that plays a leading role in them has also become a research hotspot.Among the various research areas,micro milling force prediction and stability study hold paramount importance.The establishment of an accurate micro milling force prediction model is a crucial prerequisite for optimizing process parameters,improving surface creation quality and processing stability.However,due to the coupling effect of multiple physical fields,problems such as runout,vibration,and deformation of difficult-to-machine materials such as titanium alloys are particularly significant during the micro milling process,which interferes with the prediction results.In addition,in the process of micro milling of arc thin-walled parts,due to the unconventional nature of its geometric features,the prediction of micro milling force becomes more difficult,which has become a key bottleneck restricting the development of these fields.To this end,this thesis takes titanium alloy arc thin-walled parts as the research object and conducts in-depth research on tool runout,coupled deflection deformation,micro milling force modeling and processing stability during micro milling.The main research contents are as follows.(1)Tool runout is classified and defined,including radial runout and tilt runout and calculation methods are proposed.The influence of tool runout on the instantaneous uncut thickness was analyzed.The instantaneous uncut thickness model was established based on the tool runout.A novel method is adopted to determine the tool center trajectory and cutting-edge trajectory and an iterative algorithm is used to calculate the instantaneous uncut chip thickness and cutting in and out angles.(2)The influence of deflection on micro milling force modeling is elucidated from three perspectives: tool deflection,workpiece deflection and coupled interaction.Considering the structural characteristics and force conditions of the tool and workpiece,they are respectively assumed to be Euler beams and Timoshenko beams.Based on these two beam theories,the element stiffness matrices are solved and calculated deflection deformation values.Simultaneously,a new iterative algorithm is proposed,incorporating the coupled deflection deformation values into the micro milling force modeling process to improve the instantaneous uncut chip thickness model.(3)A theoretical model of micro milling force is established,taking into account the micro milling processing mechanism and incorporating the shear effect,ploughing effect and coupling effects.The model considers the specific characteristics of the curved micro milling processing path and includes geometric analysis to calculate the cutting in and out angles as well as the instantaneous uncut chip thickness.Experimental data is obtained through curved micro milling processing experiments,which allowing for the identification of micro milling force coefficients.The micro milling force is predicted based on the established theoretical model.The rationality and accuracy of the model were verified by experiments.(4)From a dynamic perspective,this study conducts dynamic modeling of curved micro milling force by focusing on the tool-spindle subsystem and the workpiece-fixture subsystem.Both subsystems are classified and modeled,based on these models,a new double-flexibility coupled system dynamic model is developed.Stability prediction analysis is performed using a discrete method,proposed a technique for drawing stability lobes.To validate the accuracy and rationality of the model,experiments on the processing stability of arc thin-walled parts are designed based on the stability lobes,then analyzed the results.