CAJ | 학술논문

按照Lamb波理论，板内导波由多阶对称波和反对称波组成。当波长远大于板厚时，利用经典平板理论对Lamb方程进行简化，此时板内主要有零阶对称波S0和反对称波A0两种模态。认识薄板内声波模态，不仅有助于分析声源性质，提取有效信号，而且可以提高声发射检测中时差定位的准确性。利用PAC公司的Fieldcal标准信号发生器和Nielsen Hsu断铅法作为信号源在0.7 mm薄钢板上进行声波传播实验。通过比较实测波速和理论波速甄别板内的声波模态。实验发现对称波S0实测波速和理论波速比较吻合，而反对称波A0的波速由于频散而较难精确测量。综合两种模态波的波速情况，声发射检测中利用对称波速度进行声源定位计算更加接近薄壁结构声波的传播状况。
안조Lamb파이론，판내도파유다계대칭파화반대칭파조성。당파장원대우판후시，이용경전평판이론대Lamb방정진행간화，차시판내주요유령계대칭파S0화반대칭파A0량충모태。인식박판내성파모태，불부유조우분석성원성질，제취유효신호，이차가이제고성발사검측중시차정위적준학성。이용PAC공사적Fieldcal표준신호발생기화Nielsen Hsu단연법작위신호원재0.7 mm박강판상진행성파전파실험。통과비교실측파속화이론파속견별판내적성파모태。실험발현대칭파S0실측파속화이론파속비교문합，이반대칭파A0적파속유우빈산이교난정학측량。종합량충모태파적파속정황，성발사검측중이용대칭파속도진행성원정위계산경가접근박벽결구성파적전파상황。
According to Lamb theory, guided waves contain multiple symmetric and antisymmetric modes on a plate. When the wavelength is much greater than the plate thickness, classical plate theory can be used to understand the wave motion. There are two modes of propagation. One is called the extensional (S0) and the other the flexural mode (A0 ). In order to research these acoustic modes, a signal source named Fedical and the other named breaking pencil lead were used for a steel plate of 0.7mm thick. Both the fundamental extensional and flexural modes were detected with transducers. Acoustic modes were analyzed and wave velocities were measured. The experimental value of the extensional wave velocity is in close agreement with the theoretical velocity, but it is difficult to measure the flexural wave velocity accurately because of its dispersion. It can be concluded that extensional wave velocity is reliable for source localization in AE testing.