Views:5 Author:Site Editor Publish Time: 2019-10-23 Origin:Site
1 When the ultrasonic wave propagates in the medium, the interface will be reversed.
2 The ultrasonic directivity is good, the higher the frequency, the better the directivity;
3 Ultrasonic propagation energy is large, and the penetration force of various materials is better and strong. The following mainly introduces pulse reflection ultrasonic nondestructive testing.
The pulse signal has different crack anti-injection wave effect in the aluminum plate and propagation. After several experiments, it is found that the ramp pulse is a better choice.
The A-scan crack detection and crack width determination fixes the two piezoelectric disc
transducers transmitted and received by the ten letters on the same straight line J so that they constitute a set of transducer devices for transmitting and receiving. Using the scanning method, the transmitting and receiving device group is moved from the left to the test riding member. By analyzing the collected test data, the crack existing on the test piece can be clearly detected, and the width of the crack is determined. The value of the crack moves the device from the left to the right on the test piece. When the device is moved to the left position , only one upper edge reflection can be received. The acquired signal continues to move the set to the right, when is moving to the left position near point 2 (the left vertex of the crack). The collected signal. It has a curved reflected wave, the first reflected wave is the crack reflected wave, and the reflected wave of the upper edge of the test piece of the j-ray wave is reflected. The reflection time of the crack reflected wave is shorter than the reflection time of the edge reflected wave. When the device continues to move to the 3 area, the acquiring signal can be collected, and the scanning continues, and the electric energy finds the right vertex of the crack. When the end of the crack is encountered, it is immediately available in the piezo piece. Marking the end position of the crack, and determine the crack width by the end of the crack indicated by the left. Testing data acquisition and analysis software Via GP. IB interface, the data collected by the computer can be stored in EXCEL file and other multi-data forms, which is very convenient for analysis and use. The GP-IB interface used is a GP-IB interface for the PCI slot on one end of the computer. The digital oscilloscope TDS3034B itself has a GP-IB interface module. The test system can also use a slow RS-232 serial interface.
The ultrasound wave that is transmitted and received is converted by wave mode, and the transverse wave (also called shearwave) is transmitted in the aluminum plate. The non-destructive testing that the transverse wave can only perform below is the non-destructive testing of the transverse wave flaw detection method. The shear wave flaw detection method is that the sound wave is incident on the workpiece at a certain angle to generate a wave pattern conversion, and the transverse wave propagates in the structure. A method of structural flaw detection using transverse waves. After the transverse wave is incident on the L-piece, the sound wave will be reflected when the defect is perpendicular to the sound beam or the angle is large. A defect wave appears on the display screen. The test piezo disks crystal used were mainly aluminum plate. The propagation speed of the transverse wave in the aluminum plate aluminum is 3100 m/s. The position of the crack can be calculated and determined based on the transmission time of the wave obtained by the GPIB connected to the computer.
Crack detection by using piezoelectric ceramic crystal materials