大口径火炮身管药室内膛裂纹电磁超声表面水平剪切波检测方法

大口径火炮身管药室内膛在射击过程中承受高温高压，易产生网状多裂纹，对安全性能造成隐患，但传统检测手段对内壁清洁度要求较高，且检测周期长。为此，提出基于电磁超声表面水平剪切波（SH波）的身管药室内膛裂纹检测方法，对缺陷进行检测。建立表面SH波电磁超声换能器的辐射声场有限元模型，分析永磁体长度和对数对辐射声场的影响，对电磁超声换能器设计参数进行优化。在研究表面SH波声场特征的基础上，建立表面SH波在含有交叉裂纹的身管药室中传播的有限元模型，分析表面SH波与不同夹角裂纹缺陷的作用规律，并通过实验予以验证。结果表明，当使用12对长度为20 mm的永磁体制成的电磁超声换能器时，能够对10 mm×1 mm×2 mm的交叉裂纹进行检测，分析裂纹夹角与回波幅值的影响规律，为身管药室内膛多裂纹检测提供了可靠依据。

Detection Method for Chamber of Large-caliber Artillery Barrel Based on Electromagnetic Ultrasonic Surface SH-wave

The inner bore surface of a large-caliber artillery barrel with drug chamber must be subjected to high temperature and pressure during the launching process. This may produce multi-network cracks and pose a hidden danger to safety and performance. The challenge remains that the traditional detection methods have higher requirements for inner wall cleanliness while the detection period takes a long time. A detection method based on electromagnetic acoustic transducer surface shear-horizontal(SH) wave is proposed to detect the cracks on the inner bore surface of a gun barrel with chamber. Quantitative detection is also carried out in assessing defects. This process includes establishing a finite element model relating to the radiated sound field of surface SH wave on permanent periodic magnet electromagnetic acoustic transducer(EMAT). The influences of length and pair number of permanent magnet on the radiated sound field are analyzed, and the design parameters of EMAT are optimized. In studying the characteristics of surface SH wave sound fields, a finite element model of the surface SH wave propagation in a gun barrel with the chamber with cross cracks was also established. The law of interaction relating to the surface SH wave and crack defects with different angles were verified through both study and experiment. The results illustrate that the electromagnetic acoustic transducer composed of 12 pairs of permanent magnets with length of 20 mm could be used to detect the cross cracks with 10 mm×1 mm×2 mm, and analyze the influence law of crack angle and echo amplitude.