Selective modal control of blade vibrations by local laser shock peening

The main purpose of this study is to explore the selective modal control of blade vibrations using laser shock peening (LSP) for the mode shapes with stretching of the mid-plane, which are commonly encountered in some local zones of the higher-order mode shapes. The zones with stretching of the mid-plane are selected for LSP, which leads to residual stresses and grain refinement, in order to control the corresponding mode. A kind of diamond-shaped specimen is chosen as the object of the study to simulate the actual blade. First, theoretical measurements and the finite element method are used to analyze the mechanism of selective modal control. The effects of LSP in different selected zones on modal stiffness and damping are compared, and the selective modal control is simulated. Then, an excitation test was conducted; the experimental results are in good agreement with the simulation, which effectively proves the correctness of the analysis. As the amplitude of the excitation increases, the vibration shows a significant nonlinearity. At this time, the blades treated by LSP show an unusual jump phenomenon, which limits the vibration amplitude in a smaller range. A further experimental analysis is performed for the interpretation of this phenomenon. Based on the above results, it is proved that the local LSP can effectively control the vibration of a certain mode, which provides a more flexible method for blade design, especially for improved design of the blade after styling.