Repair Of Damaged Aeroengine Blade Surface

Engine blade is one of the most important components of aircrafts.With the bad working environment,the damage rate of engine blade is high,and the cost is large.So the recovery and reuse of blades can be of great economic benefit.In order to carry out automatic welding repair of damaged aero-engine blade under conditions where there is no original design model of blade and there is no standard part of blade,it is required to reconstruct the undamaged geometric model of the blade from point cloud data obtained by scanning the damaged blade through reverse engineering.In this paper,the repair method based on section curves is adopted.Firstly,the damaged section curves are repaired through curve extension,and then surface skinning technology is deployed to complete the recovery of the geometric model of the blade.Among them the repair effect of the geometric modeling of the defective blade heavily depends on the effect of the section curve extension.Therefore,this paper focuses on the algorithms for curve extension,on this basis the repair of the damaged engine blade surface is complemented.The main work is as follows:1.The similarity of two curves is studied quantitatively and a measurement of similarity between two curves suitable for repairing defective blade is proposed,on this basis,an algorithm for B spline curve extension based on the similarity with reference curve is presented.Different from the existing curve extension method,the proposed algorithm takes full advantage of the similarity between the defect section curves and the near intact section curves.Under the constraint of C~2continuity,the algorithm makes the shape of the extended curve reflect the change trend of the original section curve better.Experimental results show that the algorithm can meet the requirements in engine blade repair.2.A method for curve extension based on affine transformation of reference curve is presented.Firstly,the knot vector of the extended curve is determined by unifying the knot vector of the original curve and the reference curve.Then,the B spline unclamping algorithm is used to obtain the control vertices related to the original curve.Finally,optimization method is used to determine the new added control vertices.The objective function is the sum of the squares of distance between the control vertices of the reference curve after affine transformation and the corresponding vertices of the curve after extension.The experimental results show that the curve obtained from this extended algorithm is similar to the reference curve in shape,and has better fairness.