高溫合金微小缺陷的超聲識別方法研究.pdf

1、 The research of identification methods for tiny flaw in superalloy using ultrasonic testing A Dissertation Submitted for the Degree of Master On Instrumentation Engineering By He Boda Under the Supervision of Prof. Lu

2、 Minghui College of Measuring and Opto-Electronic Engineering Nanchang Hangkong University, Nanchang, China June, 2018II Abstract Because aeroengines work in harsh environments such as high temperature and high pressure,

3、 engines have extremely high demands on the materials they manufacture, and even minor defects can cause serious accidents that cause machine crashes. The coarse-grained superalloy materials have been widely used in airc

4、raft engine manufacture because of their high strength, fatigue resistance, and high temperature resistance. However, the average grain size of the coarse-grained superalloy materials is large, and the conventional ultra

5、sonic detection technology will cause serious scattering when it is detected. The severe background noise generated will greatly affect the signal-to-noise ratio of the ultrasonic detection signal. , it is difficult to i

6、dentify the flaw echo. Therefore, it is very important to study the detection and identification methods of tiny defects of coarse-grained superalloys. This dissertation focuses on the ultrasonic detection and identifica

7、tion method of tiny defects in coarse-grained high-temperature alloys. It uses the characteristics of the defect and the nonlinear frequency response characteristics of the ultrasonic flaws to identify and analyze the de

8、fects, and proposes a new rough. Crystal superalloy material tiny defects identification method, and made some innovative results. The main work of this article is as follows: First of all, theoretical analysis is made o

9、n the difficulties and significance of detection of tiny defects in coarse-grained superalloy materials. The influence of tiny defects on the law of acoustic propagation was studied, and the identification of tiny defect

10、s using the characteristics of acoustic diffraction and nonlinear response was determined. Secondly, using the ABAQUS finite element simulation software to simulate the diffraction propagation law of the sound model, the

11、 flat bottom hole model and the small defect model. And simulate the ultrasonic nonlinear response in the tiny flaw model. Finally, a series of flat-bottom hole defects and a cross-hole defect were designed and manufactu

12、red in the test piece. The simulation results were first checked in the A-scan experiment. The optimal probe and system parameter settings were selected to detect and identify artificial defects in the feature scanning s