Quantitative research on defect of curved components with immersion ultrasonic testing

With the influence of curved surface, ultrasonic beam scattering and focusing will be enhanced during the propagation in curved components. So the acoustic energy is strengthened or weakened, resulting in difficulties of defect quantification. To overcome the disadvantage of high cost and low adaptability of traditional methods such as reference block, a defect quantification method based on ultrasonic measurement model for curved components with immersion ultrasonic testing is studied. Based on multi-Gaussian ultrasonic beam models and defect scattering models under the way of pulse excitation, an immersion ultrasonic measurement model for curved components is proposed. The model is verified by measuring the defect echo waves of a convex specimen and a concave specimen. Taking a flat bottom hole as an example, the defect quantification characterizing curves are established based on the ultrasonic measurement model. The characteristics of ultrasonic beam scattering and focusing in curved components are studied by simulation. Moreover, the relations between the relative defect wave amplitude and the curvature, as well as the defect depth and the defect quantification are analyzed. Therefore, the defects can be quantified by predicting the relative defect wave amplitude. As an example of the application, a steel curved component is studied during its immersion ultrasonic inspection, and the comparisons of the model predictions with experimental results show that the prediction deviation of the relative defect wave amplitudes is less than 1.2 dB, and the quantization error of the defect quantification is not more than 8.7%. So the proposed method is feasible, which can be conveniently and effectively applied to curved components with immersion ultrasonic testing. ©, 2014, Hangkong Xuebao/Acta Aeronautica et Astronautica Sinica. All right reserved.