Research On Machining Deformation Control Technology Of Blisk Based On Stiffness Matching

As the core component of the aerospace engine,the blisk has the characteristics of complex surface and weak rigidity,and its manufacturing represents the national industrial technology level.The machining accuracy of blisk blades directly affects engine performance.With the development of engine,the blade is becoming larger in size and thinner in thickness and the thin-walled cantilever feature of the blade causes it to be easily deformed in the machining process.Meanwhile,blades generally use difficult-to-process materials,and the cutting force increased at the same time,which brings more difficulties to high precision manufacturing of blade.Therefore,this paper mainly focused on the machining deformation and proposed a deformation control method based on force and stiffness matching,studied the cutting force prediction model and considered the removed material impact on the blade stiffness.The specific research content of this paper includes four parts:(1)The cutting force prediction model was studied and the calculation algorithm of the cutter-workpiece engagement based on intersection between arc and tool swept surface was proposed.The cutter-workpiece engagement(CWE)determined the cutting situation of the cutter edge.Through analyzing the boundary composition curves of the CWE,and the tool swept surface of the last tool path was constructed as the machined surface of the workpiece.According to the information of tool movement,feasible contact area was extracted and discretized into a set of arcs.The CWE boundary was obtained by calculating intersection points between arc and tool swept surface,where the torus patch approximate the complex surface was presented to accelerate the intersection calculation.Experiments and application case had been carried out to illustrate the validity,and the comparison result shows that the computational efficiency of the CWE had been improved about 40%.Meanwhile,the slot cutting experiments of TC4 material were conducted to identify the cutting force coefficients,and then the cutting force prediction model was constructed.(2)The removed material impact on workpiece stiffness was considered and a nodes re-sorting method was proposed to calculate the deformation of the in-process workpiece(IPW).To reduce the scale of the global stiffness matrix and minimize the memory allocation for computation,the super-element method was adopted to construct the finite element model.The removed nodes number were determined with the tool movement,and the stiffness matrix of the IPW is directly obtained by eliminating the contribution of the removed nodes in the global stiffness matrix.To solve the inversion problem of large-scale stiffness matrix in the calculation of the cutting force-induced deformation,a nodes resorting method was proposed.And then,milling experiment was carried out and by scanning and reconstructing the machined surface,deformation calculation algorithm of the IPW was validated.(3)The deformation control method based on the cutting force and maximum stiffness direction matching was presented.The maximum stiffness direction was proposed in this paper according to the phenomenon that different deformations were produced when apply forces with the same magnitude but in different direction.The stiffness of the in-process blade was obtained by using the method of updating the stiffness of the IPW.To match the force with the maximum stiffness direction,the cutter orientation optimization algorithm was presented.The best cutter orientation was obtained by adopting the quantum particle swarms optimization algorithm at the key cutter location points,and the parallel computing was used to accelerate the optimization process.And then,the cutter orientations of all cutter location points were obtained by the quaternion interpolation algorithm.(4)Tool path planning and machining experiment of the blade were carried out and a cutter location point calculation algorithm based on torus patch approximation was proposed.To improve the computation efficiency of the cutter location point,the torus patch was constructed to approximate the blade surface and the tangential problem between cutter and complex surface was converted to the tangential problem between two analytical surfaces.The average computing time of the proposed algorithm was saved about 71.16%.Then,the machining experiments of the blade were performed and the machining error was obtained by comparing with theoretical contour data.The experimental results show that the machining deformation of the blade machined with the optimized cutter orientation was reduced by about 36.51%,and this indicates that the deformation control method proposed in this paper can effectively reduce the machining deformation of the blade.