Research On The Acoustic Field Calculation And Inspection Reliability Of Ultrasonic Test

Ultrasonic test plays an important role in guaranteeing the operational safety and product quality, and how to improve and evaluate the reliability of ultrasonic testing has become one of the key issues that need be solved for our country’s industrial transformation. The main works included in this article focus on the acoustic field calculation and inspection reliability. Firstly, the ultrasonic acoustic field calculation model is established and the mechanism of the propagation of ultrasonic acoustic field and its interaction with the defect is studied, and the application of our model on the aided design of inspection procedure, performance demonstration and echo analysis could improve the reliability of ultrasonic testing; Secondly, based on reliability analysis method of detection, ultrasonic detection experiments are designed to study the influence of different factors on reliability of the detection(POD) and reliability of the sizing (POS); Finally, a reliability assessment method for procedure evaluation and optimum is proposed based on the random parameters generation model, acoustic field calculation model and POD probability model.The acoustic propagation model for calculation of the acoustic field of all types of probe and transmission medium is established based on the Raleigh integral and Pencil method, and so as the quantitative relationship between acoustic field distribution and the parameters of specimen, probe and inspection. The model considered the sound field emission of the common ultrasound probe, such as the contact probe, flooding focused probe, double crystal probe, phased array probes, etc; the transmission and attenuation of acoustic field in the isotropic and anisotropic media, multi-media and the reflection, refraction and wave mode conversion on the surface and bottom of specimen. The MATLAB programs are developed for calculation and digital display of the distribution of acoustic field, and the calculation results are compared with the commercial software for validation of our model. The result indicates that the ultrasound propagation model is suitable for the practical application of ultrasonic testing, and could be applied to probe and testing procedure design.In order to improve the accuracy and speed of calculation, the defect scattering model for crack-like and volume defects (excluding slag), and slags are established based on the Kirchhoff approximation and the Born approximation theory. The MATLAB programs are developed for calculation various types of defect echo in one-layer isotropic media, and the results could be displayed in terms of A scan, B scan, C scan and echo dynamic curves. The numerical results are compared with experimental results and commercial software for validation of our model. The results show that the self-built model is suitable for the on-site applications. At the same time, the Ultrasonic Testing Calculation and analysis system (UT-CAS) is established based on the propagation model, defect scattering model and Auld’s reciprocity principle, and its application of aided design of inspection procedure, performance demonstration and echo analysis for ultrasonic testing of complex medium is given.Based on reliability analysis method of inspection, the experiments of automatic and manual ultrasonic testing of carbon steel and stainless steel weld are designed. In automatic ultrasonic testing experiments, the POD and POS of different probe types, defect types, scanning locations are calculated and compared based on Bootstrap re-sampling technique and log-normal distribution model, and the influence of different inspection parameters on reliability of detection is quantitatively assessed. In the manual ultrasonic test, the POD and POS of the high level, low-level people and the automation equipment are calculated and compared based on Log-odds model and the log-normal distribution model. The results show that the ultrasonic test results is a random process, the inspection parameters have a great impact on the reliability of detection, especially for human factors, different inspectors in the same conditions obtained much different results form echo other. So the effective reliability assessment is extremely needed.The reliability analysis method based on acoustic field calculation is proposed to solve the small sample problem of field data, and avoid high cost and difficulty of block manufacture. The defect echo signal which is used as an input for the probability model to calculate the POD and parameter (size, angle and location) curves is calculated based on randomly generated model and acoustic field calculation model. This method could be applied to the assessment and optimum of the nuclear power plant in-service inspection process through quantitative analysis of the influence of complex component structures, defect size and orientation, probe and array parameters on the reliability of detection.