Abstract
Blade crack will cause severe mistuning of hard-coated blisks, which will lead to vibration localization. To identify crack mistuning and analyze influence factors, in this study, a mistuning identification method of blade cracks in hard-coated blisks is presented based on modified component mode mistuning reduced-order model, in which the hard-coated blisk with blade crack is decomposed into a substructure of tuned hard-coated blisk and a substructure of coated blade with cracks. Crack mistuning of each coated blade can be obtained by a single identification calculation. After verifying the rationality of this identification method, the influence factors of blade crack mistuning are analyzed. The influence factors include the crack location on the coated blade (cracks occurring only in coating or only in blade substrate or both in blade substrate and coating), crack length, crack position in the radial direction of the blisk, and modal data type of coated blisk used for mistuning identification calculation. The research results show that, with the increase of crack length, the mistuning of crack occurring only in the coating does not increase continuously but decreases firstly and then increases. For the first bending modes, the closer the blade crack is to the blade root, the larger the mistuning is. For the second bending modes, the blade crack located at the position of maximum modal displacement will produce large mistuning. For hard-coated blisk with blade crack, these crack mistuning variation rules are of great significance to the dynamic analysis and the determination of the crack location.
Highlights
The variation trend of frequency eigenvalue deviation rates calculated by the modal data of first swing mode family and first torsion mode family is in poor agreement with that of crack lengths (as shown in Figure 8(b) and (d))
It is important to note that the mistuning of the cracks occurring both in hard coating and blade substrate is not equal to the sum of the other two kinds of crack mistuning
For the first bending and second bend mode families, the mistuning of cracks occurring only in blade substrate and the mistuning of cracks occurring both in hard coating and blade substrate shows a nonlinear increase trend with the linear increase of crack length at most locations
Summary
As one of the core components of modern aeroengines, the blisk (integral bladed disk) is exposed to a harsh working environment of high temperature, high pressure, and high rotation speed for a long time.[1,2] Under the combined action of shocks and loads of centrifugal, aerodynamic, and thermal, the blisk will produce hightemperature creep, corrosion, high-frequency fatigue damage, and other failure forms.[3,4] In order to improve service life, the hard coatings with vibration reduction, heat insulation, wear resistance, corrosion resistance, and other functions have been widely used on the blisk.[5,6,7,8] As an important form of high-frequency fatigue failure, blade cracks will lead to vibration localization of the hard-coated blisk.[9,10,11,12] The intensification of vibration will accelerate crack propagation, which is likely to cause catastrophic failure.[13,14,15] for the cracked blisk or. In order to more accurately study the vibration location and other dynamic behaviors of hard-coated blisks with blade cracks, for the hard-coated blisk, it is necessary to investigate blade crack mistuning identification method and crack mistuning influence factors. Through the studies of the above literature, it is found that most of the researches reflect the mistuning effect generated by the blade crack based on the analysis of the vibration location of the blisk or bladed disk. An undamped free vibration model of the hard-coated blisk with blade cracks is established based on the finite element method. According to the identification algorithm proposed in “Theory” section, the crack mistuning of the coated blades of the numerical hard-coated blisks is calculated.
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