Mapping Relationship Of Machining Trajectory Between Free-state And Clamped-state For Thin-walled Curved Surface Parts

With the rapid development of aerospace,national defense equipment,medical and people's livelihood and other fields,thin-walled curved surface parts have attracted wide attention because of their light weight and high specific strength.But,due to the poor rigidity of thin-walled curved surface parts,it is easy to produce clamping deformation under the clamping force,which results in machining errors(for short,clamping errors).Moreover,the workpiece-fixture system is an elastic system,and the machining errors caused by clamping rebound deformation of thin-walled surface parts are particularly significant.However,at present,there is no complete and effective method to avoid the clamping error of workpiece-fixture system.Most of the existing studies focus on the deformation control of workpiece clamping and the prediction and compensation of clamping error.There are few studies on the springback deformation of workpiece and the machining errors caused by the release of clamping force.In view of this,this paper studies a method of mapping the machining trajectory of thin-walled curved surface parts in free-state and clamped-state to ensure that the thin-walled curved surface parts meet the processing requirements after springback deformation due to the release of clamping force.Specific research contents are as follows:Firstly,according to the theory of elastic deformation for thin shells,based on the known layout of thin-walled curved parts,the mathematical model of deformation for thin shells mid-surface is established.Based on mid-surface deformation of thin shells and the theory of surface concomitance,a mathematical model of machining trajectory mapping for thin-walled curved surface parts is established,and the machining trajectory of thinwalled curved surface parts in clamped-state is generated,which lays a foundation for the re-planning of processing trajectory of thin-walled curved surface parts in clamped-state based on original design.Then,aiming at the problem that the scallop height and chord height errors of curved surface are excessive due to the existence of elastic deformation caused by clamping,a method of re-planning the machining trajectory for thin-walled curved surface parts in clamped-state based on harmonic mapping is proposed.Based on the indirect parametric subdivision method and the mature Delaunay algorithm,the parametric point cloud in three-dimensional space is triangulated,and the machining trajectory of the threedimensional space model is re-planned by dimension reduction.Finally,the circumferential cutting path of the pattern to be machined is obtained,which meets the requirement of machining accuracy.Finally,taking thin-walled cylindrical parts as an example,according to the proposed method of mapping the processing trajectory of thin-walled surface parts in free-state and clamped-state,the processing experiments of thin-walled cylindrical parts in clampedstate based on the original design are carried out.The results show that the average cutting depth is increased by 60% and the uniformity of cutting depth is increased by 75.9% compared with that of the unprocessed one,and the machining quality is improved obviously.Based on the mapping,the proposed method of reconfiguration of the machining trajectory of thin-walled surface parts under clamping state based on harmonic mapping is further adopted to improve the processing quality.The method of mapping the machining trajectory for thin-walled curved surface parts in free-state and clamped-state proposed in this paper can effectively reduce the machining error caused by clamping rebound deformation after the processing of thin-walled curved surface parts is completed,and significantly improve the machining quality of thin-walled curved surface parts.At the same time,it also provides theoretical basis and technical support for the actual production and manufacture of thin-walled parts...