A detection method for micro-defects near the surface of hexagonal crystal materials based on shear wave backscattering
A defect detection, hexagonal crystal technology, applied in the direction of material analysis, analysis of materials, measuring devices, etc. using sound waves/ultrasonic waves/infrasonic waves
Active Publication Date: 2020-09-29
CENT SOUTH UNIV
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However, this method has not been applied to the backscattering model of hexagonal materials
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[0091] In this specific embodiment, an AZ80 magnesium alloy test block containing tiny near-surface artificial defects is taken as an example to illustrate a method for effectively detecting tiny near-surface artificial defects of hexagonal crystal materials. In the present invention, the test block is firstly fixed in a water tank filled with water, and the ultrasonic pulse generator / receiver (also known as ultrasonic instrument) is used to excite the ultrasonic focusing probe, and the ultrasonic focusing probe is clamped on the five-degree-of-freedom motion platform by the probe frame, and the The motion control card installed on the computer is connected to the control circuit to control the motion of the five-degree-of-freedom motion platform, adjust the posture of the ultrasonic focusing probe in the water tank, and use the high-speed data acquisition card on the computer to acquire and store the original ultrasonic A wave output by the ultrasonic instrument The signal is ...
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Abstract
The invention discloses a method for detecting near-surface small defects of a hexagonal crystal material based on transverse wave back scattering. The method comprises the steps of describing a near-surface ultrasonic back scattering phenomenon in a polycrystalline material by virtue of a transverse wave-transverse wave single scattering response model, introducing a grain size distribution function and a hexagonal crystal elasticity modulus covariance so as to correct an original model, giving out a confidence upper limit of grain size noise through the organic combination of an extreme value distribution theory and the corrected transverse wave-transverse wave once scattering response model, and carrying out defect imaging by taking the confidence upper limit as a time varying threshold. According to the method, the defects of a near-surface transverse through hole with a diameter of 0.2mm and a burial depth of 1mm can be effectively detected. Compared with a traditional longitudinal wave fixed threshold value method and a time varying threshold method, the method disclosed by the invention has the advantages that the possibility that the grain size noise is falsely detected asthe defect under a high gain is inhibited, and the influences caused by a large-interface echo generated by mismatching of acoustic impedance between a coupling agent and a detected part on a near-surface defect signal are eliminated.
Description
technical field [0001] The invention relates to the field of ultrasonic nondestructive testing, and more specifically relates to an ultrasonic testing method for tiny defects based on the theory of extreme value distribution. Background technique [0002] Most hexagonal metals have low density, high specific strength and excellent impact resistance, such as magnesium alloys and titanium alloys, which have gradually become economical substitutes for steel and aluminum alloys, and are widely used in aerospace, automotive and military industries. For example, it can be used to manufacture key components such as aircraft hubs, flaps, missile engine brackets, and satellite control panels. If the component has tiny near-surface defects, it will be continuously subjected to cyclic loads and impact stresses during service, and damage such as fatigue cracks and stress corrosion cracks will be formed along the near-surface defects; when these defects reach a critical size, it is even ...
Claims
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IPC IPC(8): G01N29/06G01N29/11G01N29/44
CPCG01N29/069G01N29/11G01N29/44
Inventor 李雄兵黄远添宋永锋倪培君
Owner CENT SOUTH UNIV