Optimization Of Fixture Layout For CAFD And Selection Method Of Clamping Mechanism

It is a very complicated process to process the blank into parts.In this process,not only the known conditions such as the blank material and the final machining shape of the workpiece are involved,but also the unknown parameters such as cutting heat and residual stress are involved.The coupling of these factors makes the parts appear bending,twisting or combined bending and twisting deformation after processing,resulting in cracking,and even lead to the overall scrapping of parts,which not only brings losses to China’s economy,but also slows down the pace of China’s aerospace industry.Therefore,it is of great significance to systematically analyze the complete machining process of aviation integral structural parts for the promotion of aerospace industry.Firstly,the processing process and its influencing factors of the whole structure parts are introduced based on the research results at home and abroad.The maximum factor that affects the deformation is residual stress.After comparing the measurement methods of residual stress,the stress value of crack flexibility method is determined and the residual stress distribution curve is obtained.The residual stress measured by the experiment is replaced into the finite element model,and the processing deformation value under the action of the model is compared with the experimental value and the analytical value to verify the correctness of the finite element model.Secondly,combined with the cutting theory,the machining deformation of parts under the coupling of constant cutting force and variable cutting force and residual stress is analyzed.Based on this,the influence of undercut phenomenon on the final machining deformation of parts is discussed.The residual stress is the main cause of the deformation of parts in high-speed milling process.The influence of cutting force can be achieved to a certain extent to ignore.At the same time,for multi frame structure,the odd and even machining sequence has the minimum deformation value.Under the same processing sequence,the structure of parts also has certain influence on deformation law.In addition,the influence of blank initial state on the deformation of machining is analyzed.The theory of blank bending deformation is used as the judgment basis for the existence of initial deformation of blank.The initial deformation value of the blank is preliminarily determined under several group of comparative simulation.Based on this,the processing deformation of parts under different initial blank deformation and the initial deformation of the specified blank are analyzed.The deformation rules of parts are obtained under different machining positions.The deformation inflection point is not only related to the force,but also the structure of the parts.Finally,the optimal machining position of the workpiece with and without initial deformation is obtained by means of the step decreasing algorithm.The optimal machining position of the part is related to the initial deformation of the blank.It is shown that the reasonable selection of the processing position and the processing direction can effectively reduce the machining deformation of the parts.