| Serving as the core parts of an aeroengine,turbine blades work in high temperature and high pressure environment.Damages will occur after the blades work for a period of time.If the damaged blades can be repaired,the service cycle of the blades will be prolonged and the cost of use will be remarkably reduced.At present,the solutions for aeroengine blade repair rely mainly on manual operation and the repair processes are separated,so the efficiency are low and the quality varies while executed by different people.In this thesis,a method of automatic reparation for turbine blades is proposed.The measurement and repairation processes are integrated on the CNC machine tool.Firstly,the damaged blade is measured with on-machine inspection technology.Then,the measure datas are used to reconstruct the repair geometry of the blade.The reconstructed model is used as a reference to generate scanning path of lasser cladding.Finally,the CNC machine tool performs the trajectory commands until the repair operation finished.Based on the scheme described above,several problems are studied in this thesis.1)On-machine inspection path planning and post processing for blade measure.A software for on-machine inspection was developed with NX Open development toolkit.The software can be used to generate measure paths for platform,radial surface,shape curve and freeform surface.Besides,a post process tool for measure path of Heidenhain iTNC-530 CNC system was developed with NX Post Builder.2)Measuring reference calibration for blade workpiece.The measurement accuracy depends significant on the measuring reference,however,errors may occur while reclamping the blades on the machine tool.So,two calibration algorithms were developed with the measure data of the plane and surface feature at blade root.3)Measure data registration for blade shape curves.As for the torsional deformation problem of blade workpiece,a registration algorithm based on Gaussian Mixture Model was developed.The torsion and deviation value of the balde shape can be calculated with this method.This algorithm possesses stronger applicability while take the point cloudmatching probability into considerate.4)Extraction of the repair geometry at blade top.Top wear is a common damage form of blade.In this thesis,a simple method is proposed to obtain the repair geometry of the defected blade.The design model is transformed base on the shape curve registration result at first.Then the repair geometry is obtained by splitting the design model with a section surface,which is fitted with the measure data of the damaged blade top.Accurate repair geometry can be obtained since there is no need to judge the extension height of the geometry by user.5)Laser cladding path planning for the repair geometry of defected blade.Damaged forms are varied among different blades,while the top surface of the blade model is relatively uniform.So the top surface of the blade model is used as the basis to slice the repair geometry in this thesis.Then the contour parallel and Zigzag combine method is used to generate the laser cladding trajectory of each layer.An on-machine inspection experiment based on Hermle C400 AC daul rotary table machine tool is processed to validate this method.The experiment result indicate that the algorithms presented above work well in turbine blades damaged model reconstruction.As for the Laser cladding path planning strategy,the reparation result is verified with the material additive simulation module for the time being. |
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