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针对现有超声仿真模型计算所得的结构噪声和散射衰减与实际情况符合程度较差的问题,根据奥氏体不锈钢焊缝的晶粒特征及其弹性特性,建立了壁厚78mm的二维焊缝MINA超声仿真模型。采用能够体现晶粒背散射现象的时域有限差分法作为模型的仿真计算平台,计算结果表明,2.25MHz中心频率下算得的A扫描信号不仅能够重现结构噪声和散射衰减现象,而且一次底面回波波形、峰值频率以及噪声幅度与实验信号符合良好。此外,利用A扫信号合成的焊缝B扫图像与实验之间也有较好的对应性。
According to the problem that the structural noise and scattering attenuation calculated by the existing ultrasonic simulation model are not in conformity with the actual situation, according to the grain characteristics and elastic characteristics of austenitic stainless steel weld, a two-dimensional weld with 78mm wall thickness MINA ultrasonic simulation model. The time-domain finite difference method, which can reflect the backscattering of grains, is used as the simulation platform of the model. The calculated results show that the A-scan signal calculated at 2.25MHz center frequency can not only reproduce the structure noise and scattering attenuation phenomenon, Waveform, peak frequency, and noise amplitude agree well with the experimental signal. In addition, there is a good correspondence between the B-scan image of weld and the experiment using A-scan signal.