One article: understand ultrasonic flaw detection of castings

Date：2022-09-08 17:22:35Views：1055

Nondestructive testing is divided into conventional testing technology and unconventional testing technology. Conventional testing technologies include ultrasonic testing (UT), radiographic testing (RT), magnetic particle testing (MT), penetrant testing (PT) and eddy current testing (ET). Unconventional nondestructive testing technologies include acoustic emission (AE), infrared (IR), and holographic nondestructive testing (hNT).

1、 Ultrasonic sound detection technology

UT flaw detection is one of the nondestructive testing methods in industry. When the ultrasonic wave enters the object and encounters a defect, part of the acoustic wave will be reflected. The transmitter and receiver can analyze the reflected wave, so that the defect can be detected abnormally accurately. The position and size of the internal defect can be displayed, and the material thickness can be measured.

2、 Ultrasonic flaw detection (UT)

1. Definition of ultrasonic flaw detectionIt is a technology that studies the reflected, transmitted and scattered waves through the interaction between ultrasonic waves and test pieces, detects and characterizes the macro defects of test pieces, measures geometric characteristics, changes in microstructure and mechanical properties, and then evaluates their specific applicability.

2. Principle of ultrasonic operation: mainly based on the propagation characteristics of ultrasonic wave in the test piece.

a. The sound source generates ultrasonic wave, and the ultrasonic wave enters the test piece in a certain way;

b. The ultrasonic wave propagates in the specimen and interacts with the specimen material and the defects therein, so that its propagation direction or characteristics are changed;

c. The changed ultrasonic wave is received by the detection device, and can be processed and analyzed;

d. According to the characteristics of the received ultrasonic wave, evaluate whether there are defects in the test piece itself and its interior and the characteristics of defects.

3. Advantages of UT flaw detection

a. Suitable for nondestructive testing of metal, non-metal and composite materials;

b. It has strong penetration ability and can detect internal defects of test pieces in a large thickness range. For example, for metal materials, thin-walled pipes and plates with a thickness of 1-2mm can be detected, and steel forgings with a length of several meters can also be detected;

c. The defect location is relatively accurate;

d. The detection rate of area defects is high;

e. It has high sensitivity and can detect defects with small internal size;

f. The detection cost is low, the speed is fast, the equipment is light, the human body and the environment are harmless, and the on-site use is convenient.

4. Limitations of ultrasonic flaw detection

a. The precise qualitative and quantitative analysis of the defects in the test piece still needs further study;

b. It is difficult to carry out ultrasonic testing on specimens with complex or irregular shapes;

c. The position, orientation and shape of defects have certain influence on the detection results;

d. Material and grain size have great influence on the detection;

e. When the commonly used manual A-type pulse reflection method is used for detection, the result display is not intuitive, and there is no direct witness record for the detection result.

5. Application scope of UT flaw detection

a. It can be used for metal, non-metal and composite materials from the perspective of the material of the detection object;

b. From the manufacturing process of the test object, it can be used for forgings, castings, weldments, cemented parts, etc;

c. From the shape of the detection object, it can be used for plates, bars, pipes, etc;

d. In terms of the size of the detection object, the thickness can be as small as 1mm or as large as several meters;

e. From the defect position, it can be either a surface defect or an internal defect.