Research On Key Techniques Of Adaptive Machining For Repair Of Typical Damaged Blade

Blades are the important parts in the domain of aero-space.The extreme service condition,such as high pressure and temperature,causes different kinds of damage on the blade.For the intrinsic value of the blades,it is much more economical to choose repair for the damaged ones and thus extend their life of service instead of replacement.Because of the error in the manufacturing and the distortion in routine service,the actual blade is no longer identical to its original design model,which causes the necessity for the work of the reconstruction of the blade according to the measured data.The method for the model reconstruction and the repair NC machining tool path generation is studied in this thesis,aimed at two common patterns of broken blades,namely the tip-broken blade and the edge-broken blade.Coordinate measuring machine is adopted for the scanning of the blade surface,and the iterative closest point algorithm is used to match the measured data points,to decrease the error caused by the location.Then,the data points are sorted,adjusted and interpolated to shape the blade section curves,which are successively smoothed based on the theory of minimized energy.Next,a method for the alignment of the adjacent section curves is proposed to solve the problem of the distortion on the rebuilt surface.Then,the model reconstruction for the given two kinds of blades are presented.Finally,the damaged part on the reconstructed surface is extracted and utilized to generate offset faces,and on the theory of iso-parametric tool path generation,the zigzag tool path and spiral tool path are generated for the edge-broken blade and the tip-broken blade,respectively.Comparative experiments on the blade model reconstruction are implemented,with the existing methods as well as the method proposed in this thesis.The Gaussian curvature and the average deviation between the data points and the reconstructed surface serve as two criterions for the quality assessment of the rebuilt blade,the result shows that the proposed method ensures the smoothness and the approach to the blade's actual shape.Tool path for the edge-broken blade and the tip-broken blade is generated,with which the NC machining process is simulated to reprofile the repaired blade,the result shows that the thickness of the residual material is within the acceptable range,which approves the feasibility of the tool path generation method.