| Resistance has a great impact on energy consumption in aerospace,ships,automobiles,pipeline fluid transportation and other fields.Bionic non-smooth surface drag reduction in the ridge structure drag reduction showing broad application prospects and great energy saving potential due to low energy loss,simple structure,remarkable drag reduction effect.The micro straight thin wall is the key geometrical feature of the rectangular flaky groove in the ridge structure of the drag reduction surface.With the development of micro cutting technology,the use of NC machining technology to prepare surface ridge structure is more and more mature,and has the advantages of high machining precision,simple process,low cost,and can realize large-scale industrial production.However,due to the low structural stiffness of micro straight thin wall parts,the elastic deformation,cutting vibration and chatter of thin wall will be produced in milling process,resulting in machining dimensional error and the reduction of workpiece surface machining quality,and then seriously affect the surface drag reduction performance.Therefore,aiming at the dimensional error reduction in thin wall machining process,this study carry out a series of researches through the research method combining finite element simulation,mathematical modeling and experiment in order to provide common cutting theory and technology for high precision preparation of rectangular sheet surface drag reduction structures in different application scenarios.The main research contents are as follows.Firstly,the unique size effect in micro milling process is analyzed by the simulation study,and the corresponding feed per tooth values when the size effect occurs in different tool cutting edge radius are identified,which provides guidance for the selection of subsequent thin wall machining parameters.Aiming at the deformation problem of micro straight thin wall parts,firstly,the finite element model of thin wall milling is established with the finite element simulation software Deform-3D,and the effectiveness of the model is verified by experiments,which lays the foundation for subsequent research.Then,the static simulation model of thin wall deformation is established by using the finite element simulation software ABAQUS,and the relationships between thin wall deformation and different positions,different loads,different matrix sizes,different clamping methods and different thin wall sizes are simulated.Finally,the simulation analysis of thin wall axial layered milling and deformation compensation is carried out to study the feasibility of the process.Secondly,aiming at the problem of machining dimension error of micro straight thin wall parts,a micro milling force model based on infinitesimal method theory and considering the influence of tool runout is established.The thin wall deformation model based on cantilever beam method and thin wall deformation model based on Rayleigh-Ritz formula method are established,and the thin wall deformation is predicted.Considering that in the micro machining process,the radial runout and deformation of the tool are in the same order of magnitude as the key cutting parameter feed per tooth,which will seriously affect the micro machining process.The radial deformation model of the tool based on cantilever beam theory is established and the radial runout model of the tool is regressed by experiment and least square method.The comprehensive dimensional error model and the iterative compensation model of thin wall comprehensive dimensional error are established.Thirdly,aiming at the problem of active control of micro thin wall cutting quality,a micro straight thin wall micro cutting parameter adaptive adjustment device is developed.The device is directly installed on the machine tool workbench,and an independent control system based on adaptive control theory is developed for it.Through real-time measurement of the radial cutting force generated in the process of thin wall cutting perpendicular to the direction of thin wall,the strategy of active control of the thin wall radial cutting parameter according to the value of the cutting force is developed to realize the real-time measurement of the cutting force and the on-line adjustment of the cutting parameter in the process of micro milling.The stability and real-time performance of the adaptive adjustment device and control system are verified by adaptive compensation experiment.Fourthly,a series of micro straight thin wall machining experiments are carried out based on the established micro straight thin wall dimensional error prediction model and dimensional error compensation model.The developed micro straight thin wall micro cutting parameter adaptive adjustment device to verified the effect of the established micro straight thin wall dimensional error prediction model and dimensional error compensation model and the developed micro straight thin wall micro cutting parameter adaptive adjustment.The results show that after iterative compensation for the comprehensive dimensional error of thin wall,the relative dimensional error of micro straight thin wall is reduced from 6.86% to 1.10% on the premise of ensuring the good shape accuracy of thin wall,and the machining accuracy of micro straight thin wall is significantly improved.Fifthly,the aforementioned mathematical model is modified to adapt to the prediction and compensation of thin wall dimensional error of two typical difficult-to-cut materials titanium alloy and super alloy commonly used in aerospace field,and the effectiveness of the model is verified through experiment.Based on the self-developed superhard CBN micro milling cutter,thin wall micro milling experiment of titanium alloy material and super alloy material are carried out to study the influence law of different tool rake angles on thin wall machining quality,and identify the tool rake angle with higher overall machining quality.At the same time,the influence of different auxiliary machining processes on the quality of thin wall machining is studied,and the better cutting environment is identified.Combined with error prediction and compensation model,tool and cutting environment,the micro straight thin wall machining of titanium alloy and super alloy is verified. |
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