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. To meet the fan casing containment assessment requirements of engine, a new method combining ballistic impact test and finite element analysis is proposed to evaluate the casing containment capability. 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 positioned perpendicular to the projectile's trajectory to accurately capture and measure its velocities both before and after impact.. The DIC (digital image correlation) technology is used to determine the deformation field of the half ring simulator. Based on the contact-impact dynamics software, a corresponding numerical simulation model was established. The residual velocity of the projectile, radial deformation of the target, and the morphology of structural damage of numerical predictions are compared with those of experimental results. The good agreement between the two results 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 effect of the blade rotate speed and the blade size on casing containment are studied. The results show that the fan casing in rotating state can contain more impact energy than that in ballistic impact test. It is suggested that the design for the ballistic impact test can be scaled to 0.76 times the size of the real containment system. Additionally, a parametric correlation model is developed between the casing containment capacity and the characteristics of the released blade, especially the rotate speed and size. It is found that the internal energy of the casing is in a quartic relationship with the blade released speed and a quadratic relationship with the blade size. Moreover, as the blade size increases, the critical containment speed of the casing decreases exponentially.