| With the continuous development of modern science and technology and the improvement of precision machining level,people have higher and higher requirements for the machining quality of parts such as precision and surface roughness.Nickel based superalloy is widely used in aerospace,chemical industry,shipbuilding and other high-tech fields due to its excellent corrosion resistance and high-temperature resistance.The physical and mechanical properties of Ni-based superalloy make it a typical hard to machine material.Precision grinding is an important method to manufacture nickel based superalloy blades.Because the blade is a thin-walled part,the blade is easy to produce vibration in the grinding process.These are the main reasons affecting the surface quality of blade tip.Therefore,this paper takes the blade tip of nickel base superalloy as the research object,and studies the relationship between the vibration and the machined surface quality of blade tip during grinding.The work of this paper includes:(1)Considering the dressing efficiency and dressing effect,the dressing experiment of metal bonded CBN grinding wheel was carried out.In order to reduce the influence of the vibration of the grinding tool system on the experimental results,the dynamic and static balance design of the grinding wheel rod was carried out to achieve the optimization effect.Taked the moving speed of grinding table and grinding depth of blade tip as variables,the single factor grinding experiment of nickel based superalloy blade tip was designed,and the variation rules of grinding force,surface roughness and surface morphology under different experimental processing parameters were obtained.(2)According to the dynamic model of the process system of surface grinder,the mathematical model between the unbalance of grinding wheel and the vibration displacement of blade was established.The static inherent characteristics of Ni-based alloy blade were obtained by hammering test.Taked the first grinding depth of blade as variable,the single factor experiment of blade tip grinding was designed to obtain the dynamic vibration characteristics of blade under different experimental processing parameters.(3)According to the grinding experiment results,the influence of machining parameters on blade vibration and blade tip surface roughness was analyzed,and the mathematical relationship model between blade vibration characteristics and blade tip surface roughness was established.According to the position of the blade machined by the grinding wheel in the grinding process,it was found that the surface quality of the different areas of the blade tip surface was different.The variation law of surface roughness in different regions of blade tip under different working conditions was discussed.(4)According to the dimensional accuracy requirements of the special-shaped blade tip surface of nickel based superalloy blade,the scheme of grinding instead of turning was proposed.The advantages and disadvantages of each scheme were compared,and the structural dimensions of CBN grinding wheel and dressing oilstone were designed and calculated.After comprehensive consideration,the blade tip of nickel based superalloy blade was ground by using thin grinding wheel,and the feasibility of the scheme was verified by experiments.The experimental results show that the unbalance of grinding wheel and the vibration of workpiece will affect the machining quality of blade tip.According to the mathematical relationship between the wheel unbalance and the blade v ibration displacement,we can know that the blade vibration increases with the increase of the wheel unbalance.It leads to the increase of the blade tip surface roughness and the worse the blade tip surface processing quality.The results show that the su rface roughness of the middle area of blade tip surface is the best.The research results provide theoretical and experimental references for the optimization of the grinding process of the tip and the grinding process of the thin-walled parts. |
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