Machining Metamorphic Layer Of QBe2 Tube Spring And Its Influence On Stiffness

At present,China is moving to a powerful industrialized country,which puts forward higher requirements for the machinery manufacturing industry,especially for the aerospace manufacturing industry.The machining of thin-walled structural parts widely used in aerospace field requires high requirements and is difficult,which is one of the research hotspots of aerospace precision machining.Thin-walled parts have the advantages of small volume,light weight,high strength and strong bearing capacity,and the processing requirements for them include not only the shape and size accuracy and surface quality,but also the performance requirements.The processing requirements of QBe2 thin-walled tube springs include the performance index-stiffness,one of the key factors affecting its stiffness is the metamorphic layer introduced by processing.In this thesis,supported by the 13th Five-Year Pre-Research Project of Equipment Department:Low-rigidity****Technology(No.41423020201),starting with the metamorphic layer of QBe2,the cutting mechanism of QBe2 was first explored through cutting experiments,and the influence of cutting parameters on cutting force,surface topography,roughness and processing of metamorphic layer was studied.Then,the influence of metamorphic layer on cutting process was studied through simulation.Finally,combined with the mechanism experiment and simulation results,the research was carried out.The main research contents are as follows:(1)The cutting mechanism experiment of QBe2 was carried out with PCD(Polycrystalline Diamond)cutter,and the turning metamorphic layer of QBe2 was obtained by dry cutting.Through experimental research on the influence of cutting parameters on cutting force,surface roughness,surface topography and depth of modified layer,it is found that cutting depth and feed rate have the most significant influence on cutting force,feed rate has the most significant influence on surface roughness and cutting depth has the most significant influence on depth of modified layer.(2)By studying the morphology and physical properties of the machined metamorphic layer,a finite element cutting simulation model of QBe2 considering the machined metamorphic layer is established.The influence of the metamorphic layer on the equivalent stress and strain in the cutting process under different cutting conditions is studied by finite element simulation,and the influence of different blunt radius of the cutting edge on the machined surface is studied.It is concluded that the machined surface quality is poor when the cutting depth is close to the thickness of the metamorphic layer,which should be avoided in actual machining.(3)Considering the actual service situation of QBe2 tube spring,the influence of modified layer on the spring stiffness of QBe2 tube is studied by finite element simulation.It is found that the increase of the depth of modified layer leads to the increase of the spring stiffness of QBe2 tube.The cutting force measured by experiment is applied to the finite element model of tube spring,and the variation law of deformation under different depth of metamorphic layer is studied.It is found that the depth of metamorphic layer has little effect on deformation.(4)The prediction model of cutting force and depth of metamorphic layer on cutting parameters is obtained through experiments,and the cutting parameters are optimized.According to the experiment and simulation to guide the machining of QBe2 tube spring,an auxiliary support vibration suppression device is proposed,which can effectively control the machining deformation,and ultra-precision turning the QBe2 tube spring according to the optimized parameters,so that the depth of the machined QBe2 tube spring deterioration layer meets the requirements.