Vibration Characteristics and Damping Analysis of the Blisk-Deposited Hard Coating Using the Rayleigh-Ritz Method

For the purpose of improving the working reliability of the blisk (integrally-bladed disk) under severe environment, a passive vibration reduction method by depositing a hard coating on both sides of blades is developed and then investigated systematically. Firstly, an analytical model of the blisk-deposited hard coating is taken into account. Secondly, by using the Oberst beam theory and axial symmetry property, the composite hard-coated blade is equivalent to a special homogeneous blade possessing the equivalent material parameters. Then, energy equations of the blisk with hard-coated blades are derived by using the complex-valued modulus, and then substituted into the Lagrange equations. Additionally, eigenvalue equations of the blisk with hard-coated blades are acquired by taking advantage of Rayleigh-Ritz method, and its natural characteristics are obtained subsequently. Further, the frequency response functions of the blisk with hard-coated blades are formulated by using proportional damping to achieve its damping matrix. Finally, a stainless-steel blisk with deposited NiCoCrAlY + YSZ hard coating on both sides of the blades is chosen as the study case to conduct numerical calculations, and the results are compared with those obtained by experimental tests in terms of natural frequencies and mode shapes. The variation of natural frequencies, modal loss factors and frequency response functions of the blisk generated by hard coating are studied, respectively, and the influence of the coating thickness on the damping capacity are further discussed.