| Titanium alloy TC4 is widely used in aerospace,petrochemical and medical fields because of its low density,high specific strength and good corrosion resistance.Due to low hardness and fatigue performance deviation in many ways led to its further development.Rolling finishing is one of the effective means to improve the fatigue properties of metal materials.The finishing process can be used to improve the surface integrity of the parts and improve the fatigue resistance of the parts.Therefore,the aerospace titanium alloy TC4 is used as the research object.This paper uses the horizontal centrifugal roller grinding finishing technology to improve the surface integrity of titanium alloy and improve its anti-fatigue performance of the system.Firstly,the static strength analysis of the plate was carried out by ABAQUS.Based on the multiple orthogonal regression analysis method and FE-SAFE fatigue life simulation,the roughness,residual stress and external load factors were analyzed qualitatively.The initial location of crack initiation is determined.Then,the crack propagation path is simulated by ABAQUS6.11 integrated crackpropagation finite element method.Compared with the experiment,it is proved that the simulation is correct.Secondly,the three-factor and four-level orthogonal experimental method was used to study the variation of single-sided and double-sided surface integrity parameters of horizontal centrifugal roller and finish,and the influence of different process parameters on surface integrity parameters was obtained.When the single-sided processing and processing time is 60 min,the grinding block diameter is 10 mm,the loading amount is 80%,and the double-sided processing,the grinding block diameter is 5mm,the processing time is 15 min,the loading amount is 80%,the material removal amount is the largest.Whether it is single-sided or double-sided processing,grinding block diameter of 7mm,processing time 45 min,loading volume of 60%,the largest decline in surface roughness.When the grinding block diameter is 10 mm,the loading capacity is60%,and the processing time is 30 min,the residual compressive stress is the largest.Based on the the comprehensive parameters,the process parameters with better surface integrity: the grinding block diameter is 7mm,the processing time is 45 min,the loading capacity is 60%.Finally,through fatigue life comparison experiments of the single-sided and double-sided machining,it is concluded that the fatigue life after double-sided machining is slightly larger than that of single-sided machining.The fatigue life of sheet metal was determined by the method of multiple linear regressionanalysis.The formula of roughness,hardness,residual stress and stress level on fatigue life was fitted by means of error analysis and variance analysis.The fatigue limit of the specimen is 289 MPa without rolling and finishing,and the fatigue limit of the specimen is 450 MPa after single-side finishing and the fatigue limit is increased by 15.7%.The fatigue limit of the specimen is 578 MPa after double-side finishing and the fatigue limit is increased by48.5%.Furthermore,by observing the fracture morphology and the mechanism of fatigue resistance of the micro-structure,it can be seen that the micro-structure is refined before and after the processing and the crack initiation is in the sub-surface rather than the surface.The diffraction peak can be observed by XRD.It is shown that the residual compressive stress value is used to suppress the crack initiation and expansion to improve the fatigue life.In this paper,a vertical centrifugal roller grinding process TC4 titanium alloy to improve its surface integrity of the better process parameters.And the fatigue performance of the titanium alloy was improved.The research results provided the basis for the selection of the technical parameters of the titanium alloy parts of the centrifugal roller and finish,which provided a reference for the further application of the titanium alloy. |
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