The Investigation On Surface Integrity In Grinding Titanium Alloy TC11with Small Grinding Wheel

The titanium alloys, duo to their high specific strength, good performance at high or low temperature and good corrosion resistance, were widely used in the aviation, aerospace, and so on. Lots of titanium alloy parts had to be applied in the hostile environment, therefore, not only the surface roughness needed to be fulfill the requirements, but also the surface integrity needed, which gave to the considerable difficulty in the machining. However, the surface integrity in grinding titanium alloy was not widely researched at home and abroad. The large grinding wheel and belt were not easily used for the complex curved surface, small cavity or small grinding space. What’s more, it is not efficient to grind parts by hand, and the surface quality is not easily guaranteed. Thus, the titanium alloy TC11is chosen, and it is necessary to investigate the surface integrity in grinding titanium alloy with small grinding wheel on the computerized numerical control machine.Firstly, the small green SiC wheel with elasticity and vitrified CBN wheel with super hardness were chosen to grind the titanium alloy TC11. The small SiC wheel was used to grind titanium at low velocity, and the vitrified CBN wheel was used at high speed. The many factors and levels orthogonal grinding parameters were estabilished for the two kinds of grinding tools, respectively.Secondly, the investigation on surface integrity in grinding titanium alloy TC11was done. For the surface roughness, the surface rouness values were measured, and the sign-noise ratio S/N were done subsequently. The optimal combination of grinding parameters was gotten, which was used to grind titanium, and the good surface topography was gotten. The ANVOA was also done, and the factors that have the most important influence on the surface roughness will be confirmed. For the microhardness, the microhardness profiles were drawn, and the reason of the microhardness variation was analysed. The metallotraphic structure of ground surface was measured. Phase transformation, white layer and recrystallized amorphous layer were not observed, and the reason that caused deformation of the crystalline grain was gotten. For the residual stress, the reason causing the residual stress was analysed, and the measurement method and stress formual were given. The residual compressive stress was obtained, which satisfied the requirement. Thirdly, the contact model of grinding wheel and workpiece was established, and the finite element simulation that grinding force caused the deformation of workpiece and residual stress in the grinding process was done. The law of grinding force casusing displacement variation was obtained, the maximal displacement deformation in the normal grinding force direction was observed. The larger grinding force was, the larger the displacement deformation and residual stress were.Finally, the heat flux model was set. The grinding temperature field and stress field were simulated by finite element method. The temperature field was changed with the heat source moving. The temperature reduced gradually from the grinding center to outer, and then reached to the stable state as time went. The simulated results indicated that the grinding temperature rised when the grinding force was larger and larger. The temperature was larger at the geometric contact length rather than at the actual contact length.The residual compressive stresses-49.0-62.2MPa were obtained in the ground surface. Compare to the actual measurement value, they were all residual compressive stresses and the same order of magnutide, which was a good base to establish grinding parameters and to forecast the grinding result.