Research On The Formability Of T2 Copper Sheet In Polymer Powder Based Flexible Die Forming Technique

Sheet metal stamping technique attracted the attention of scholars from home and abroad due to its advantages of large-scale production,high efficiency and low cost.Its forming methods include rigid die forming and flexible die forming.With the development of science and technology,higher requirements are put forward for the shape and quality of forming parts,with local complex or small-scale structures,such as proton exchange membrane fuel cell bipolar plates and various tubular parts with lateral structures.When these parts are formed by rigid die,it is difficult to process and assemble the die and this leads to high cost.Moreover,the forming capacity is limited because of the stress concentration in the rigid die forming process.Aiming at solving the problems mentioned in the rigid die forming process,such as the die processing and assembling,and the poor forming capacity of the sheet,a flexible die forming process based on polymer powder medium,in which the polymer powder replaces the rigid punch to form copper sheets,is proposed.Polymer powders are elastic solid particles,easy to seal,and they are small sized particle so this process has better die-sticking property when forming complex and small sized parts.In this paper,tube bulging parts,cup-shaped drawing parts and fuel cell bipolar plates are successfully formed by polymer powder medium based flexible die forming technology.A series of important forming indexes such as forming limit,forming fitness and forming surface quality of the forming parts in the forming process are analyzed,and the formability of this process is researched.The devices used for measuring lateral force in polymer powder compression test and producing tubular parts with lateral structures were developed.And the lateral stresses at different height were obtained by direct and indirect methods.In the tube bulging test,the numerical simulation of the tube bulging process was carried out by using ABAQUS software and by comparing the experimental and simulated data,the lateral stress distribution during powder compression was obtained.Furthermore,based on cup-shaped parts and bipolar plate forming experiments,the forming parameters in flexible die forming technique of polymer powder medium,such as forming force,forming limit,wall thickness distribution,forming contour and surface quality,were studied.The results show that the flexible die forming method of polymer powder medium has the advantages of high forming limit,good surface quality and good attachment performance.It can be used to form small and medium sized parts with complex structures.