Mechanism Of Micro-cutting For QBe2 Thin-wall Pipe

With the rapid development of micro-machining technology,parts with micro-mechanical structural features have been widely used in aerospace and other fields.The thin-wall pipe springs discussed in this paper are one of them.The thin-wall pipe spring is a key flexible part of the inertial navigation system.The processing precision is about to directly influence the performance of the gyroscope.Since the thin wall thickness of the pipe spring is only a few tens of micrometers,the processing method has a great influence on the size,shape,residual stress and surface quality of the part.In this paper,the mechanism of micro-cutting and processing of QBe2 thin-wall pipe is studied by simulation and experiments.The influence mechanism of different processing parameters on the force,surface quality and tool wear of QBe2 micro-cutting is researched.The deformation mechanism with its superession of thin-wall pipe are researched to theoretically give a foundmental support for the processing in factory.The main contents of this paper and relavent conclusions in this paper are shown below:The J-C constitutive equation of QBe2 is established by material testing system(MTS)experiment and split Hopkinson pressure bars(SHPB)experiment.The micro-cutting mechanism of QBe2 is studied by using finite element simulation software AdvantEdge.The two methods of judging the minimum cutting thicknesses based on finite element simulation are verified.The prediction model of minimum cutting thickness is established and verified.The minimum cutting thickness effect is studied from the direction of specific cutting energy.The intrinsic relationship between the minimum cutting thickness effect and the cutting-edge radius effect is revealed from the direction of cutting specific energy.The theoretical prediction model of the cutting specific energy is verified by the simulation cutting experiment.The micro-cutting performance of QBe2 among polycrystalline diamond(PCD),cemented carbide and cubic boron nitride(CBN)tools has been compared in this paper.The surface roughness and surface texture of different tools has been analyzed.The same time,the tool wear including the rake face,cutting edge and flank has been studied.The results show that the PCD tool has steady micro-cutting performance due to its low surface roughness Ra,the smallest cutting force and the tool wear.The cemented carbide tool performs second only to the PCD tool and is also suitable for the micro-cutting of QBe2.The CBN tool has been proved unsuitable for the micro-cutting process of QBe2 in that the production of large built-up edge can result in the unstability of this process with rough surface and big cutting force.Meanwhile,the micro-cutting parameter of PCD tool has been optimized by orthogonal cutting experiment.The influence of tool wear on the cutting force and surface quality is also compared with the increase of the cutting distance of the cemented carbide tools and the PCD tools.The residual stress distribution law under various cutting parameters is studied by finite element simulation.The law of residual stress depth and value under different cutting depth and cutting-edge radius id studied.The law of deformation coused by the redistribution of residual stress on thin wall is studied.At the same time,the thin-wall deformation law under the cutting force is obtained by applying the Fx,Fy,Fz measured in experiments to the thin-wall pipe,which verifies the conclusion of the research on the cutting performance of QBe2.Meanwhile,it also provides a basis for improving the precision of thin-wall pipe machining.