The study of the formation of a hollow cellular structure with a given geometry

Introduction. The use of superplastic forming technology presents a number of challenges, including the lack of experimental and analytical data and the absence of specialized processing facilities. Another crucial factor limiting the widespread use of this methodology is the uniqueness and complexity of the equipment for performing the superplastic forming operation. The study is aimed at determining the optimal shape of the primary blank for the superplastic forming (SPF) process in order to obtain acceptable elongation of the bridges and minimal shrinkage. Methods and materials. Titanium alloy grade VT-6 was used as the material for obtaining the samples. The shape of the initial workpiece was optimized using a model sample, in which the ratio of the height and width of the fillets varied from 3:2 to 3:6 mm. The sample was obtained from a sheet 5 mm thick, by mechanical processing. The two halves of the sample were pre-welded together along the contour using argon-arc welding and sealed after pumping out the air from the cavity between them. Diffusion welding of the sample took place in an autoclave. The SPF was carried out in a limiting container at a temperature of 900±10 °C, argon was supplied according to the law ensuring optimal metal drawing in superplasticity modes. The width of the welded surfaces was from 2 to 4 mm. Modeling and finite element analysis of the SPF process were performed in the MSC Marc software package. The microstructure of the samples was studied using an Altami MET 1C microscope (with a USB 3.0 5 MPix camera). Results and discussion. The results of finite element analysis and a full-scale experiment of SPF are presented to verify the modeling results. During the research it was found that in order to minimize the depth of the resulting sink marks it is necessary to ensure an optimal ratio of the fillet radii equal to 3:5 and 3:6. The difference in the width of the platforms before SPF and the lintels formed after SPF was determined. The smallest narrowing of the lintels is characteristic of the widest platforms. Conclusion. The combined use of finite element modeling and a full-scale experiment made it possible to preliminarily identify the optimal ratio of the height and width of the outer fillet, which allows for acceptable elongation of the bridges and minimal shrinkage.