Research Of Ultrasonic Peening Forming Technology On Perforated Plate

There are usually existing lightening hole,pilot hole and process hole in Aeronautical structural panel that often occur hole deformation, cracking and stress concentration When using Ultrasonic peening forming,which have serious influence on forming precision and strength properties of Aeronautical structural panel.All of the forming defects have close connection with the residual stress distribution determined by peening area, panel geometry and peening parameter.According to the forming defects of perforated plate,the theory of residual stress distribution are analyzed and forming mechanism of residual stress distribution to sheet forming are studyed.experiment and finite element are used to analysis the influence of peening process parameter to perforated plate quality.The process method and best parameter level are determined.The physical basic process was analyzed and the critical peening velocity of elastic deformation and elastic-plastic deformation was calculated through the collision theory.The formules of impact force and impact diameter were studied through elastic-plastic theory before and after sheet rebound. Relationship between the sheet bending and shot peening residual stress distribution was studied; formula for the sheet metal forming bending curvature radius and arc value are deduced.The forming characteristics and hole deformation state of perforated plate was analyzed.The peening region and sheet structure which were suit for single rate peening forming were discussed. The influence of peening parameters(the hole margin,thickened ring width,thickened ring thickness,the current intensity, the projectile diameter) to forming quality of perforated plate was analyzed.The selection of the best hole margin L is 3~10mm, the best thickened ring width M is 9~15mm and the best thickened ring thickness H is 1~3mm.The finite element scheme was estabilished and finite element method combined dynamic analysis and static analysis was adopted.The finite element model,material properties,mesh,load and boundary conditions was setted.The finite element method was used to analysis the influences between peening parameters and forming quality of perforated plate.On the whole, the maximum error of finite element results and experimental results is 22%, the average error is less than 10%,which means a good reference value.