Research On The Optimization Of Core-plate Structure Of Multi-layer Db For TC4

With the development of aeronautic and astronautic technologies, Titanium alloy materials are used in the aircraft extensively to reduce the structure weight. Superplastic forming and diffusion bonding technology adopted in the forming of many sandwich structures is an important technology for titanium alloy, which has many advantages in the integral forming of complex component. For sandwich structure, geometric shape and size of core-plate cavity directly affect the load resistance and forming of integral component, and connection status between core-plate pieces determines the forming results.Based on the theory of bending of thin plates for small deflection, deflection change under a certain load is discussed for square and rectangular cavity of four layers structure. When the thickness of thin plates is 1mm, the analyzed results show that load resistance of sandwich structure is better when side length of square is in below 50mm, and thinning rate of sheet is reasonable when the value of short side is about twice as large as that of the cavity depth. For rectangle structure, the deformation is little when the ratio of short side to long side, named k, is less than 0.4. It is difficult to form for less k, because rectangle structure is too narrow. Finite element simulation was calculated for the forming of sandwich structure core-plate in different weldingline distribution and temperature, whose results show that bending deflection of the weldingline occurs when weldingline distribution is not reasonable. Weldingline deformation is normal in the same condition when weldingline distribution is changed appropriately. Forming efficiency is higher if simulated temperature is 920℃. When superplastic forming and diffusion bonding technology is adopted in the forming of sandwich structures, the subsequent forming will fail if the connection is not complete between the core-plate sheets. The connection will be reliable if core-plate sheets are welded with laser, meanwhile, the forming will be successful. The core-plate sample was welded with CO2 laser, whose weldingline distribution is not reasonable, and then it was formed. The experimental results show that bending deformation of the weldingline is consistent with the simulation results.