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论文类型：期刊论文

发表时间：2022-06-01

发表刊物：NDT & E INTERNATIONAL

卷号：128

页面范围：102632

摘要：Macroscopic elasticity of plasma sprayed thermal barrier coatings (TBCs) is often anisotropic. Effective characterization of elastic constants is crucial for prediction and evaluation of TBC mechanical behaviors. However, elastic constants of TBCs sprayed on matrix is usually difficult to be determined. In this paper, an inversion method of TBC elastic constants is developed through ultrasonic back-reflection technique combined with Christoffel equation. An algorithm for calculating the coating ultrasonic velocities (longitudinal and transverse wave velocities) in different directions is proposed. A control device to adjust and measure the ultrasonic incident angle from water/coating/matrix/water multi-interface structure is designed. Five elastic constants of coating are inverted using the determined velocities combined with simulated annealing algorithm. Results show that the inverted elastic constants of plasma sprayed Al2O3 coating C-11, C-13, C-33, C-44, and C-66 are 104.99 GPa, 22.09 GPa, 185.78 GPa, 28.43 GPa, and 26.64 GPa, respectively. The deviations between experiment and inversion velocities were less than 2.37%, and Young's modulus in three orthogonal directions show anisotropy. Then, statistical features of pore and micro-crack, including content, orientation, etc., were analyzed using laser scanning confocal microscope and scanning electron microscope, which primarily indicates that micro-cracks with preferred orientation (mainly parallel to x(3) axis) are responsible for that elastic constant in the direction normal to the matrix is higher than that in the transverse direction.