Dynamic Response and Containment of Blade Shedding in Gas Turbine Engines

In this thesis, the problem of blade shedding in aviation gas turbine engines (GTE) is investigated analytically, numerically and experimentally. The work is divided into three integrated sections. The first is concerned with the dynamic response of traditional metallic blades and advanced metal matrix composite (MMC) blades accounting for their geometric and material nonlinearities, and mode coupling effects. The transient response of traditional metallic blades under a periodic contact load and decaying centrifugal force field is obtained by modeling the blade as a rotating tapered Timoshenko beam. The dynamic behavior of realistic advanced MMC blades is determined using a unified beam formulation and micromechanics homogenization scheme. The second is concerned with blade shedding experiments. A novel instrumented scaled down test rig is designed and developed using dimensional analysis to ensure its dynamic equivalency with a GTE. This test rig is used to study the interactions of a released blade with a single trailing blade and a fully bladed disk. The third is concerned with the finite element (FE) analysis of blade shedding to examine the containment capability of various containment ring designs and propose a new improved system. This comprehensive study includes fundamental planar impact studies, and blade shedding analysis of a fan disk with single-ring and dual-ring designs. The outcome of this work reveals that the lateral displacement of a blade due to a decaying centrifugal force field is an order of magnitude higher than that observed at constant rotational speeds. A significant increase in the natural frequency and reduction in weight can be achieved with the use of MMC blades. Remarkably, the experimental results confirm the FE predictions of a typical fan disk. They clearly show the influence of the trailing blades on the trajectory of the released blade, large deformation of the trailing blades and confinement of the released blade at the tip of the trailing blades. The proposed dual-ring design composed of ductile frontal aluminum ring and backing Kevlar ring with an interfacial gap has the potential to successfully arrest the released blade within the confines of the ring.Ph.D