Study Of The Surface Integrity And Its Influence On Fatigue Life During Cryogenic Turning Titanium Ti-5553

Having the characteristics of high strength,high toughness,low density,corrosion resistance and so on,Titanium alloy Ti-5553 is widely used in the manufacture of structural parts in the aerospace field.As Ti-5553 material is metastable β phase titanium alloy,it belongs to a typical difficult-to-machine material.It is easy to come into being surface defects,surface plastic deformation and microstructure changes during processing,resulting in a reduction of fatigue life.The study found that low temperature is beneficial to inhibit tool wear and improve surface quality,but it is also possible to change material properties and microstructure simultaneously,thus affecting its fatigue life.Therefore,starting from liquid nitrogen low temperature cutting Ti-5553,contrast dry and high pressure cutting the surface integrity of processed materials is studied in this paper.The main work is as follows:The effects of different process parameters(cutting speed,feed rate,cooling conditions)on surface morphology were investigated.The surface roughness parameters Ra and Sq are used to evaluate the influence of different process parameters on the surface roughness,and the noise-noise ratio of surface roughness under different process parameters is calculat ed to analyze the influence law of process parameters on the surface roughness of cutting.The wavelet function is used to split the three-dimensional surface topography,and the variation law of different frequency signals and its influencing factors are analyzed.Based on the theory of plastic deformation and plastic deformation depth model,which can be used to analyze the influence of different process parameters on the plastic deformation in the gradient direction of the workpiece section.With the analyzation of image-pro plus image phase processing software and matlab,the effect of different process parameters on grain size and distribution is known to us.The variation rule of work hardening in the gradient direction of workpiece section is analyzed to determine the influence of process parameters on surface hardening rate.Based on the theory of residual stress generation in machining,can analyze the influence law of different process parameters on the residual stress on the surface of machined materials,and a simulation model of residual stress in machining can be set up.Combined with the variation law of plastic deformation gradient can build the residual stress distribution map in the gradient direction of processed material section,and the mapping relationship between residual stress and plastic deformation is analyzed.Design fatigue samples and fatigue experiments,establish ANSYS static tensile simulation to verify the feasibility of determining the fatigue experiment scheme.The key influencing factors of fatigue life and the response relationship are explored.The fatigue properties of Ti-5553 titanium alloy turned by liquid nitrogen at low temperature are analyzed.The mapping relationship between surface integrity and fatigue life of Ti-5553 titanium alloy turned by liquid nitrogen is established.