Study On Push-cylinder Stretch Forming Technology By Means Of Combination With Kinematics And Finite Element Numerical Simulation

With the continuous development of aerospace,shipbuilding,construction and many other fields,the demand for multi-variety,small batch and complex sheet metal products continues to increase.It is of great significance to explore and develop advanced plastic processing technology and equipment.In recent years,the proposal and successful application of flexible stretch forming process not only avoids the defect of insufficient flexibility of the clamping mechanism in the traditional stretch forming process,but also greatly improves the dimensional accuracy and material utilization of formed products.The occurrence of defects such as wrinkles and cracks are reduced.In this paper,the push-cylinder stretch forming technology is proposed based on the technical characteristics and development status of flexible processing.The push-cylinder stretch forming equipment is specially designed for this new process,and its outstanding feature is that the working pressure of the rodless cavity of hydraulic cylinders is used as the main forming force,which increase the working output of the equipment.This paper takes full advantage of kinematics and finite element numerical simulation to study the push-cylinder stretch forming technology from loading trajectory,stress distribution,strain distribution and thickness reduction rate.The experiments were carried out and the quality of formed parts were examined.The main research contents involved in this article are as follows:(1)The design ideas and equipment structural characteristics of the push-cylinder stretch forming technology were elaborated in detail.The displacement load used in the numerical simulation was designed,and the working procedure of the push-cylinder stretch forming technology on curved surface parts was summarized.(2)According to the push-cylinder stretch forming technology,a simulation model of kinematics and a finite element analysis model were established.Taking saddle-shaped parts as example,the differences between the theoretical trajectory and the simulated trajectory were compared,and the distribution of stress,strain as well as thickness were analyzed.(3)Compared and analyzed the process of push-cylinder stretch forming technology and pull-cylinder stretch forming process.By analyzing the forming process of spherical and saddle-shaped parts,it is found that the movement state was more stable during the pushcylinder stretch forming technology.When the precision of formed parts meets the requirements,the stress and strain under the condition of push-cylinder stretch forming technology increased while the springback decreased.(4)The saddle-shaped parts were processed by the push-cylinder stretch forming machine,and its surface quality as well forming accuracy were analyzed.