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前言目前,由于断裂力学的发展,可准确地评价有缺馅焊缝的强度和寿命,也可使设计愈益合理。由此,就迫切要求高精度地测定缺陷实际状况,特别是缺陷高度(板厚方向上的缺陷尺寸)。就测定焊缝缺陷高度方法而论,端部回波法简便且测定精度较高,获得愈来愈多的应用。端部回波法是根据缺陷端部回波声程和探头的折射角,按几何关系求出缺陷高度的方法。该方法的适用性和测定精度等,在很大程度上为下列因素所左右:①使用的探头、频率和折射角等测定条件;②缺陷的大小、粗糙度和倾角;③超声波相对缺陷面的入射角度;④工件的材质、形状和板厚;⑤端部回波的辨别方法;⑥缺陷高度的计算方法等。这些对适用性和测定精度等的影响条件虽未一一弄清,但多数已经明瞭。
Foreword At present, due to the development of fracture mechanics, the strength and life of the missing weld can be accurately evaluated, and the design can be made more and more reasonable. Therefore, it is urgent to accurately measure the actual condition of the defect, in particular, the height of the defect (the size of the defect in the thickness direction). With regard to the method of determining the height of weld defects, the end echo method is simple and has high measuring accuracy and more and more applications are obtained. End echo method is based on the end of the defect echo equation and the probe angle of refraction, according to the geometric relationship between the height of the defect method. The applicability and accuracy of this method are largely due to the following factors: (1) the probe used, the measurement conditions such as the frequency and the refraction angle; (2) the size, roughness and inclination of the defect; (3) Angle of incidence; ④ workpiece material, shape and thickness; ⑤ end echo identification method; ⑥ defect height calculation methods. Although these influences on applicability and measurement accuracy have not been clarified, most are clear.