The Approach To Holding Area Prediction Of 7075 Aluminum Alloy Thick Plate For Pre-Stretching Processes

In recent years,the domestic processing technology and equipment have been a huge development and progress,to be able to aerospace and other cutting-edge industries in the manufacturing process of the production of the deformation of the problem of rational planning and control.But the main factors which affect aviation structural materials of large Aluminum Alloy plate is the formation of the initial residual stress,and to eliminate or reduce the residual stress is generally in the blank production process,the main method is to prestretched aluminum alloy plate,the process and the manufacturing process without clearance.Thus,it's an important factor to reduce the effect of residual stress on the machining deformation by using the Prestretchingmethod.Therefore,it's very important to study the approch to holding area prediction of 7075 aluminum alloy thick plate for Pre-Stretching Process.Pre-stretching is the main method to eliminate the residual stress in aluminum alloy plate.But the holding of stretching machince clampers on the two ends of the plate can not only affect the cutting volume and yield of prestretched plate,as well as the elimination of residual stresses in end of plate.Therefore,by investigating the crucial technologies for the pre-stretching of aluminum alloy plate,including the constitutive model,boundary condition,failure criterion,as so on,the finite element analysis method is established for the limited pressure and slip factor.And then,while the function of initial holding length is constructed properly,the sum of the current holding length with a certain step can be taken as the next holding length.Thus,when the slip factors between the current holding length and the last one are calculated,the difference of the two can be judged.If the two is the same,the next holding length is increased with the same step along the same direction.Otherwise,the next holding length is decreased with the decreasing step along the opposite direction.The difference of the slip factor of current holding length with last holding length is iteratively validated until the absolute value of the step is not more than the given threshold value.Thus,the step-decreasing-if-direction-is-opposite planning method of the minimum holding length can be suggested to obtain the neural network training samples with the thickness of the plate and the stretch rate as input.With the nonlinearmapping of neural network,a neural network prediction model of the minimum holding length is established by the finite groups of training samples.By comparing the predicted value with the corresponding finite element simulation,it shows that the predicition error is less than 5%.Obviously,it is reasonable that the proposed step-decreasing-is-opposite algorithm based approach to holding area prediction of aluminum alloy thick plate for pre-stretching processes.