Numerical Analysis Of Ultrasonic Impact Forming Process Of 2024 Aluminum

Ultrasonic Impact Forming is a new dieless process which can be used to form small curvature plate deformation technology.It can produce compressive residual stress in both upper and bottom plate surface to improve the mechanical properties,which is suitable for large size thin plate.It has board application prospects in the manufacture field,especially in the Aerospace field.In this paper,the free stress and prebending ultrasonic impact forming process of 2024 aluminum plate is simulated by finite element method which is benefical to understand the forming mechanism and promote the application of this technology.In this paper,the method of simulating the ultrasonic impact forming process by developing the submodels by steps which is according to the physical process is proposed.The three step free ultrasonic impact forming model which including ultrasonic impact model,data transfer model and plate forming model and four step prebending ultrasonic impact forming model which including prebending model,ultrasonic impact model,data transfer model and plate forming model are developed to analyze the forming process of strip and square plate with different controlled parameters.In the free ultrasonic impact model,the transformation of the energy and the transmission of the stress wave and equivalent plastic strain are analyzed.The influences of the controlled parameters,including impact velocity,pin mass,pin shape,the device moving velocity and device offset distance,on the residual stress distributions within the target plate are discussed,which indicat that the distributions of the residual stress are non-uniform and the average compressive residual stress in the plate surface is larger in the device offset distance.The effect of the impact velocity and device offset distance on the residual stress distribution is large than other controlled parameters.The residual stress and strain obtained by ultrasonic impact model are extended to the plate forming model.The influences of the residual stress distributions on strip deformation and the influence of the residual stress distributions and plate stiffness on square plate deformation are obtained by simulating the plate forming model of the strip and square plate.The results indicate the relationship between the residual distribution and the plate deformation.The influence of the residual stress distributions and plate stiffness on the plate deformation and their influence degree are analyzed.The influence of the different prebending state on the plate deformation is analyzed by using prebending ultrasonic impact forming model.The plate deformation in the prebending direction increases and the the plate deformation in the vertical prebending direction decreases with the increasing of the prebending radius.The influence of the residual stress distribution and plate stiffness on the plate deformation is analyzed by comparing the strip and square plate deformation,and it indicates that the effect of the plate stiffness is large.The simulation method of the plate with complex impact trajectory is proposed.And the analysis process is demonstrated by square plate deformation with turning shape impact trajectory.This method can be used to predict the plate deformation with regular impact trajectory.The plate cylindrical deformation is obtained by using prebending ultrasonic impact forming model with interval areas impact trajectory and the spherical deformation is obtained by using free ultrasonic impact forming model with round shape impact trajectory,and their influence factors are discussed.