The Research On Anisotropy And Forming Properties Of TA2 Titanium Sheet

As an important lightweight structural material,titanium sheet is widely used in aerospace,automobile,biological medical and other high-tech fields due to its excellent performance of high and low temperature resistance,strong corrosion resistance,low density and high specific strength.At present,the anisotropy and forming properties of titanium sheet in plastic forming have not been studied systematically,which hinders the further promotion and application of titanium sheets to some extent.In this paper,the anisotropy and forming properties of TA2 titanium sheet were comprehensively researched through experiment,finite element simulation and theoretical calculation.The completed research work includes:(1)The uniaxial tension test was carried out on TA2 titanium sheet with different thickness and different material directions to obtain the basic mechanical properties parameters,which provided reliable data for further study on the anisotropy and forming properties of TA2 titanium sheet.The yield criterion of Hill48 based on stress anisotropy calibration is improved according to the equivalence principle of plastic work per unit volume.(2)The earing experiment was carried out to study the anisotropy of TA2 titanium sheet with different thickness.Stress and deformation anisotropy performance data were used to solve Hill48 yield criterion parameters,and lug test finite element simulation was carried out.The u-bend test of TA2 titanium sheet with different thickness and material direction was carried out with a small bending test device designed by ourselves.The modified Hill48 yield criterion was used to simulate the u-bend of TA2 titanium sheet,and the reliability of its prediction for the springback of TA2 titanium sheet was analyzed.(3)TA2 titanium sheet with thickness of 0.5mm and 0.8mm was bulged to obtain its forming limit diagram,based on the improved Hill48 yield criterion,finite element simulation of TA2 titanium sheet bulged was conducted.According to the M-K instability criterion,the forming limit of TA2 titanium sheet was theoretically predicted.Based on the test,simulation and theoretical calculation results,a new method for predicting the forming limit of sheet metal by using the thickness reduction rate was proposed.Based on the experimental verification,the method can be further extended to the study of forming limit under complex loading paths.The results of this study show that under the condition of using the calibration coefficient of deformation anisotropy performance,the finite element simulation based on Hill48 yield criterion can reasonably predict the earing condition in the drawing process of TA2 titanium sheet.The improved Hill48 yield criterion can reasonably predict the u-bend resilience of TA2 titanium sheet with different thickness and material direction.The forming limit of TA2 titanium sheet can be predicted by M-K instability criterion;The forming limit prediction method based on the thickness reduction ratio proposed in this paper can be extended to the forming limit under complex loading path.The related research results provide theoretical basis for the prediction and research of forming limit under large pre-strain,and also provide important theoretical basis and new research ideas for the study of sheet metal forming limit in the future.