A detection and location method for closed cracks in metal blocks based on finite amplitude method

Abstract

The invention relates to a method for detecting and locating a closed crack of a metal block based on a finite amplitude method. In the present invention, a series of sine waves are generated by a signal generator, and after being amplified by a power amplifier, the transmitting transducer is amplified to generate large-amplitude ultrasonic waves. The obliquely incident ultrasonic waves are transmitted to the metal block through the wedge as a detection signal, and the closed cracks in the metal block are periodically driven. Opening and closing, the sound wave is distorted to generate high-order harmonics. Most of the detection signals with high-order harmonics are reflected by the crack surface, and the detection signals are received by the receiving transducer and displayed and stored by the oscilloscope. The present invention uses wedges to connect the metal block and the transducer, and the angle at which the ultrasonic wave is incident on the metal block can be changed by using wedges with different inclination angles, so that the crack opening can avoid the situation that the detection sound wave propagation direction is detected, and the crack detection probability can be improved , it is more convenient when the simultaneous transmitting and receiving transducers are detected on the same side of the metal block.

Description

technical field [0001] The invention relates to a method for detecting and locating a closed crack of a metal block based on a finite amplitude method. Background technique [0002] Under the action of stress, the complete metal will break locally in some weak parts and form cracks. Cracks usually expand during the use of metals. It not only directly destroys the continuity of the metal, but also inevitably causes stress concentration at the end of the crack, which promotes crack propagation in metal components under lower stress conditions, and eventually fractures and fractures. Failure accident. Therefore, it is necessary to study a technology that can accurately detect early plastic deformation and fatigue cracks of metal materials. Compared with other nondestructive testing techniques, ultrasonic nondestructive testing technology has many advantages such as accurate defect location, high detection sensitivity, and harmless to the human body. However, due to the limita...

AI Technical Summary

Problems solved by technology

However, due to the limitations of the principle, the traditional linear ultrasonic testing technology can only stay in the qualitative analysis stage, and cannot achieve quantitative evaluation and precise positioning of micro-cracks.

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