Numerical Simulation of the Evolution of Wrinkling Defects in the Hydromechanical Deep Drawing Process of the 2195 Al-Li Alloy Spherical Tank Dome
In order to meet the manufacturing requirements of high reliability and lightweight for lunar lander tanks,a hydromechanical deep drawing process is proposed for forming spherical tank domes.Compared with the Alluminum alloy of 2219 and 5A06,2195 Al-Li alloy has a poor plastic deformation ability.Also,the ratio of thickness verse diameter of blank is 2.5‰,which leads to a difficult in the hydroforming of tank dome with a diameter of 3 350mm.To solve the forming defects of crack and wrinkling,the simulation model is established with the new generation of 2195 Al-Li alloy,and the simulation tests under different values of liquid chamber pressure and binding force are carried out.The deformation rules are discussed,the forming mechanisms and control methods of defects are analyzed,the path of loading pressure in the forming process of tank dome is optimized,and thus the thickness distribution of the tank dome is obtained.The results show that,during the forming process without the liquid chamber pressure,the floating area of the blank subjects to a severe compressive hoop stress and 12 wrinkles exist along the longitude direction when the punch stroke reaches 0.24H,and the number of wrinkles is doubled when the punch stroke increases to 0.79H.However,during the forming process with the liquid chamber pressure,the introduction of the liquid chamber pressure makes the floating area change from a compressive stress status to a tensile stress status,which avoids the occurrence of wrinkles.Moreover,the effects of the binding force and liquid chamber pressure on the floating area are significant.The decrease tendency of the tank dome thickness increases with the increase in the binding force,while decreases with the increase in the liquid chamber pressure.The experiment on a blank with the initial wall thickness of 9.5 mm shows that,under the binding force of 2.5×106 N and the liquid chamber pressure of 8 MPa,the maximum thickness thinning rate is 7.4%,the thickness distribution is uniform,and there is no wrinkling defect.
2195 Al-Li alloyspherical tank dome of 3 350 mmhydromechanical deep drawingwrinkling defectLimited ratio of the thickness to diameter of 2.5‰shape deviation
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