Fixture Layout Optimization For Adaptive Machining Of Aircraft Structural Parts

Adaptive machining with responsive fixtures is an effective way to release and eliminate deformation during the machining process of aircraft structural parts.Adaptive machining is based on the principle of "6+X" locating principle.The special processing mode of adaptive machining puts forward new requirements on the layout design of aircraft structural parts,how to design and optimize the fixture layout for adaptive machining is the key issue to be solved urgently.In view of the above problems,this dissertation deeply studies the fixture layout optimization for adaptive machining of aircraft structural parts.The main innovations are as follows:(1)A fixture layout design method for adaptive machining of aircraft structural parts is proposed.In view of the fact that the parts are supported during the process of adaptive machining,the rigidity of the process system is changed.The elastic deformation of the aircraft structure is analyzed during the machining process.The design criteria of floating unit are given.The calculation model of the elastic deformation of the aircraft structure parts is established based on the calculation method of the deflection of the fixed beam and the thin plate,and the layout design of the fixture is fulfilled to meet the allowable value of the elastic deformation in the machining of the workpiece.(2)The deformation simulation of clamping system for adaptive machining is studied.Aiming at the stiffness modeling problem caused by complex structure of adaptive fixture,considering the deformation of fixture unit caused by clamping force,the modeling method of floating fixture unit is studied and the stiffness of floating fixture unit is calculated.Based on the strategy of clamping deformation compensation,the contact stiffness between the workpiece and clamping unit in the clamping system is analyzed,and the machining deformation simulation model considering contact and friction is established.(3)The method of fixture layout optimization for adaptive machining is studied.Aiming at the processing characteristics of adaptive machining,taking the position of the clamping point as the design variable and the minimum elastic deformation of the workpiece web as the objective function,the genetic algorithm and the finite element method are integrated,an iterative optimization method for the number and position of clamping points is given.And then,the fixture layout that meets the elastic deformation requirements of the workpiece is determined.(4)Based on the above studies,the cutting comparison test was designed.After optimization of the fixture layout,the workpiece web roughness increased by 23.1%,indicating that the machining rigidity of the workpiece was improved and the flatness was improved by 24.3%,which indicated that the deformation of the part was improved.The dynamic stiffness of the clamping system has also been improved,which proves the effectiveness of the method for optimizing the fixture layout for adaptive machining of aircraft structural parts.