Sensor for detecting defects of inner wall of center hole

Abstract

The invention relates to a sensor for detecting defects of the inner wall of a central hole, in particular to a sensor for detecting defects of the inner wall of a central hole of a pipeline and a rotor, which comprises two wafers, an ultrasonic transmitting wafer and an ultrasonic receiving wafer. During use, after being connected with an ultrasonic flaw detector, the sensor is placed on the inner wall of a center hole as shown in figure 2, the transmitting wafer generates ultrasonic surface waves, and the surface waves are received by the receiving wafer after moving along the inner wall of the center hole by a circle in the circumferential direction. In the propagation path of the ultrasonic waves, if longitudinal defects exist, forward surface waves can be weakened or blocked, so that the surface waves are displayed on the ultrasonic flaw detector. And the sensor moves along the axial direction of the hole, so that defect detection on the inner wall of the central hole is completed.

Description

Technical Field

[0001] The invention relates to the technical field of nondestructive testing, in particular to an ultrasonic sensor for detecting inner wall defects of a pipeline or a rotor center hole, in particular to a sensor for detecting inner wall defects of a center hole. Background Art

[0002] For many parts, such as the inner wall of thick-walled pipes and the center hole of turbine rotors, defects are easy to occur on the inner wall. According to relevant regulations, the inner wall defects need to be detected, but the conventional ultrasonic detection effect is poor or even cannot be detected. Using ultrasonic surface waves inside the center hole to detect inner wall defects is an effective method. However, the contact surface of ordinary ultrasonic surface wave probes is a straight line, which has poor contact with the inner wall of the pipe and the center hole. In addition, due to the rapid attenuation of ultrasonic surface waves, if the reflected echo is used to determine the defect, the sound path will be twice the distance from the defect to the probe. Therefore, the detection sensitivity of defects exceeding half a circle is not as good as that of dual crystal probes. In addition, the single crystal ultrasonic surface wave probe cannot receive the wave from the back, and there is no display on the screen when there is no defect in normal detection. Therefore, when the coupling conditions are not good, it cannot be detected and defects may be missed. Summary of the invention

[0003] The purpose of the present invention is to provide a sensor for detecting defects on the inner wall of a center hole, so as to improve the detection efficiency and detection sensitivity of defects on the inner wall of the center hole and reduce the detection cost.

[0004] A sensor for detecting defects on the inner wall of a center hole, characterized by: a double-crystal surface wave sensor design and an arc-shaped design of the contact surface between the sensor and the inner wall.

[0005] The aforementioned sensor for detecting defects on the inner wall of a central hole is characterized in that it specifically includes two important components: 1) The sensor contains two ultrasonic piezoelectric chips, one for transmitting ultrasonic waves and the other for receiving ultrasonic waves.

[0006] a) The angle between the crystal and the bottom surface of the acoustically transparent wedge should be at least greater than 75° to generate ultrasonic surface waves.

[0007] b) The directions of the two chips are opposite, that is, the ultrasonic emission direction and the receiving direction are opposite.

[0008] 2) The lower bottom surface of the sound-transparent wedge is arc-shaped, and the radius of the arc is 0.8 to 1 times the inner radius of the center hole to be tested.

[0009] By means of the sensor, inner wall defects of the pipeline inner wall, rotor center hole, etc. can be conveniently detected.

[0010] The present invention relates to a sensor for detecting defects on the inner wall of a central hole. The sensor is provided with two piezoelectric chips in opposite directions for transmitting ultrasonic surface waves and receiving ultrasonic surface waves coming from the opposite directions. The contact surface between the sound-transmitting wedge and the inner wall is designed in an arc shape so as to fit with the arc shape of the inner wall and maintain good coupling.

[0011] When in use, the sensor is connected to the ultrasonic flaw detector and placed on the inner wall of the center hole. Figure 2 As shown, the transmitting chip generates ultrasonic surface waves, which move around the inner wall of the center hole in a circle and are received by the receiving chip. If there is a longitudinal defect in the path of ultrasonic propagation, the advancing surface wave will be weakened or blocked, and thus displayed on the ultrasonic flaw detector. The sensor moves along the axial direction of the hole, completing the defect detection of the inner wall of the center hole. The above description is an overview of the technical solution of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is the sensor wafer arrangement of the present invention.

[0013] Figure 2 This is a schematic diagram of the acoustic beam propagation of the sensor detecting defects on the inner wall of the center hole. DETAILED DESCRIPTION

[0014] The present invention will be further described below with reference to the accompanying drawings.

[0015] A sensor for detecting defects on the inner wall of a center hole, characterized by: a double-crystal surface wave sensor design and an arc-shaped design of the contact surface between the sensor and the inner wall.

[0016] The aforementioned sensor for detecting defects on the inner wall of a central hole is characterized in that it specifically includes two important components: 1) The sensor contains two ultrasonic piezoelectric chips, one for transmitting ultrasonic waves and the other for receiving ultrasonic waves.

[0017] a) The angle between the crystal and the bottom surface of the acoustically transparent wedge should be at least greater than 75° to generate ultrasonic surface waves.

[0018] b) The directions of the two chips are opposite, that is, the ultrasonic emission direction and the receiving direction are opposite.

[0019] 2) The lower bottom surface of the sound-transparent wedge is arc-shaped, and the radius of the arc is 0.8 to 1 times the inner radius of the center hole to be tested.

[0020] By means of the sensor, inner wall defects of the pipeline inner wall, rotor center hole, etc. can be conveniently detected.

[0021] The present invention relates to a sensor for detecting defects on the inner wall of a central hole. The sensor is provided with two piezoelectric chips in opposite directions for transmitting ultrasonic surface waves and receiving ultrasonic surface waves coming from the opposite directions. The contact surface between the sound-transmitting wedge and the inner wall is designed in an arc shape so as to fit with the arc shape of the inner wall and maintain good coupling.

[0022] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the technical principles of the present invention, and these improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A sensor for detecting defects on the inner wall of a central hole, characterized in that: Design of dual-element surface wave sensor.

2. A sensor for detecting defects on the inner wall of a central hole according to claim 1, characterized in that: It includes two important components: 1) The sensor contains two ultrasonic piezoelectric chips, one for transmitting ultrasonic waves and one for receiving ultrasonic waves: a) The angle between the tangent line of the crystal and the bottom surface of the acoustically transparent wedge should be at least greater than 75° to generate ultrasonic surface waves; b) The two wafers are in opposite directions, that is, the ultrasonic emission direction and the receiving direction are opposite; 2) The lower bottom surface of the sound-transparent wedge is arc-shaped, and the radius of the arc is 0.8 to 1 times the inner radius of the center hole to be tested.

Images