Study on Optimization of the Process Parameters of Adaptive Flexible Polishing for Blade of Blisk
Author:Huai Wen Bo
The blisk is the core component of the major equipment in the fields of aviation,space,ship and sea,and energy and so on.The surface quality problem is very easy to induce fatigue failure,which leads to the shortening of service life of the engine.There are obvious milling residual heights and crest troughs on the surface of blisk,and the polishing process is needed to improve the surface quality.However,the polishing process mainly adopts the artificial polishing method.The surface quality consistency of the artificial polishing is poor and inefficient,and it not only affects the fatigue life,but also restricts the production cycle.In this paper,based on the polishing technology of "five axis numerical control + flexible grinding head + elastic grinding tool",the adaptive flexible polishing technology for the complex curved surface of the blisk was studied,and the efficient and reliable polishing process was established to improve the surface quality and production efficiency for the blisk.In order to realize the prediction and control of the surface roughness of the adaptive flexible polishing for the blisk,this paper takes "five axes numerical control + flexible grinding head + elastic grinding tool" as the research platform,and takes the abrasive cloth wheel as the grinding tool to study the adaptive flexible polishing process parameters optimization for the complex curved surface of the blisk,and deeply studies the process parameters influence law on the polishing,surface roughness optimization,process parameter interval optimization,surface roughness prediction,efficiency optimization,etc.The main research work and main conclusions are as follows:(1)A flexible adaptive polishing method for the complex curved surface was proposed.Based on the blisk structural characteristics,the structural composition and working principle of the test platform "five axis numerical control + flexible grinding head + elastic grinding tool(abrasive cloth wheel)" were analyzed,and the adaptive flexible polishing process for the complex curved surface of the blisk was proposed.(2)A polishing force prediction model was established.Polishing force is the key parameter affecting the integrity of polishing surface and ensuring the constant polishing force is the main way to achieve adaptive polishing.The influence parameters and its influence law for the polishing force of the abrasive cloth wheel were clarified through the single factor test.The main influence parameters of the polishing force were determined by the orthogonal test and the difference method.The parameters range for binary quadratic regression orthogonal rotation combination experiment were determined through the test for polishing force repetition characteristic and the material removal,and the polishing force prediction model was established by using the orthogonal test results.The stable region of the main process parameters that affects the polishing force was obtained by the model error variation trend.(3)The dividing method for process parameters stable and unstable range,optimal interval and non optimal interval were proposed based on the concept of process parameters sensitivity and relative sensitivity for surface roughness.Mathematical models of the process parameters sensitivity and relative sensitivity for surface roughness were established through orthogonal test.Then,the parameters stable range and optimal range for polishing process of the abrasive cloth wheel were obtained,providing theoretical and experimental basis for the process parameters selection and the surface roughness control.(4)The roughness ratio prediction model was established.The experiment proved that the surface roughness of the blisk polished before and after with the same polishing parameters have a significant linear relationship in a certain range and the roughness ratio can reflect the polishing results more scientifically.The roughness ratio prediction model was established based on the orthogonal center combination test results and verified by variance analysis.Then,optimized process parameters combination and optimal ratio were obtained by response surface method,and its estimated interval and fitness range for optimization ratio were calculated.The roughness ratio prediction model reliability,optimization parameter and estimation interval were verified by polishing tests.(5)The abrasive cloth wheel polishing efficiency was studied and optimized.In order to improve the polishing efficiency,the concept of polishing efficiency and critical polishing times were proposed,and two calculation methods for polishing times were established;one is that the polishing times,which must be less than critical polishing times,to make the value of the surface roughness up to 0.4μm could be solved by mathematical relation between the polishing time and the surface roughness;the other is that the sum of the polishing times of every abrasive cloth wheel with highest efficiency selected according to the current surface roughness to make the value of the surface roughness up to 0.4μm could be solved.The polishing process parameters(polishing force,rotation speed,particle size)influence laws on the optimized targets(surface roughness and polishing efficiency)were analyzed through the grey correlation degree,and the optimized process parameters combination were obtained.Two methods were used to calculate the polishing times,and the optimization parameters reliability was proved by the test results.Finally,the polishing experiment was carried out for four TC4 blades numbered with A,B,C and D on a certain type engine and verified the reliability of the optimization results of the polishing process parameters.