Evaluation of Damage Process of a Coating by Using Nonlinear Ultrasonic Method

Coatings

Lei He¹  Dingguo Xiao¹  Shiyuan Zhou¹  Pengzhi Ma¹  Chunguang Xu¹ 

[1] School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China;

关键词: acoustic nonlinearity;    material degradation;    simplified nonlinear parameter;    second-order and third-order nonlinear coefficient;   

DOI  :  10.3390/coatings11040440

来源: DOAJ

【 摘 要 】

During the service or external loading of the surface coating, the damage accumulation may develop in the coating or at the interface between the substrate and the coating, but it is difficult to measure directly in the early stage, so the acoustic nonlinear parameters are used as the early damage index of the coating. In this paper, the nonlinear wave motion equation is solved by the perturbation method and the new relationship between the relative ratio of second-order parameter and third-order parameter was derived. The nonlinear ultrasonic testing system is used to detect received signals during tensile testing of for the specimen with Al₂O₃ coatings. It is found that when the stress is less than 260 MPa, the appearance of the coating has no obvious change, but the nonlinear coefficients measured by the experiment increase with the increase of the tensile stress. By comparing the curves of nonlinear coefficients and stress respectively, the fluctuation of curves the second-order nonlinear coefficient A₂ and the relative nonlinear coefficient β′ to stress is relatively small, and close to the linear relationship with the tensile stress, which indicates that the two parameters of the specimen with Al₂O₃ coatings are more sensitive to the bonding conditions, and can be used as an evaluation method to track the coating damage.

【 授权许可】

Unknown