Study on the numerical simulation of aeroengine titanium alloy casing containment

The containment process of aero-engine casing is very complex, which involves large deformation, material viscoplasticity and nonlinear dynamic response of structural elements. In this paper, a new method combining ballistic impact test and finite element analysis is proposed to evaluate the containment capability of real aero-engine fan casing. A blade-liked projectile was used to impact the half ring simulator to obtain the impact resistance of the titanium alloy casing. The high-speed cameras were aimed perpendicular to the path to measure pre- and post-impact velocities of the projectile. Using the DIC (Digital Image Correlation) technology to determine the deformation field of the half ring simulator. Based on the commercial finite element software LS-DYNA, a corresponding numerical simulation model was established. The predicted results of the residual velocity of the projectile, radial deformation of the target, and the morphology of structural damage are compared with experimental results. The good agreement between the two indicated the accuracy of the numerical method. Under the low energy impact, the projectile was rebound, and the half ring absorbed energy with bulge. Whereas in the high energy impact, the projectile penetrated the half ring target and result in tear in the rear surface. Finally, the validated numerical simulation method was employed to simulate the real fan blade/casing containment process, and the influence of the blade rotate speed and the blade size on casing containment are studied. The results show that, there were two major impacts between the fan blade and the casing, one is the leading edge of the blade impacts on the casing to form small tear marks, the other is the blade body subjected to the casing causing tear band and bend outward. Obviously, the second impact was the most destructive to the casing. With the increase of the blade rotate speed, the damage area of the casing enlarges, and the plastic deformation energy increases rapidly, thereby diminishing the containment capability. The size of the released blade mainly affects the second impact phase on the casing, with larger sizes resulting in higher levels of interaction forces.