Non-destructive investigation of a structure by vibration analysis

我们已经开发了一种方法来估计的结构振动分析的缺陷的位置。我们使用了混凝土块的结构和缺陷是由厚度为200妈妈的乙烯基片建模。传感器阵列附着在混凝土块的表面上，并使用小锤施加振动脉冲。由于受迫振动在裂纹位置处反射，因此使用波束形成技术通过传感器阵列拾取反射波来估计位置。由于表面波的功率远大于缺陷所需的反射波的功率，因此不能正确地估计缺陷的位置。因此，我们提出了一种方法来消除无用的表面波，并取得了更好的估计。但这种方法要求裂纹必须平行于表面。为了避免这一限制，我们重新假设强迫振动在裂纹的位置反射，球面波辐射到传感器。在裂纹斜向块体表面的情况下进行了试验，取得了较好的效果。

We have developed a method to estimate the position of defects of a structure by vibration analysis. We used a concrete block as the structure and the defect is modeled by a vinyl sheet with a thickness of 200 mum. An array of sensors is attached on the surface of the concrete block, and a vibration pulse is forced using a small hammer. Since the forced vibration reflects at the position of a crack, the position will be estimated by picking up the reflection wave with an array of sensor using a beamforming technique. Since the power of the surface wave is much greater than that of the necessary reflection wave from the defect, the position of the defect could not been estimated correctly. So, we have developed a method to eliminate the useless surface wave, and a better estimation was achieved. But this method requires the restriction that a crack should be parallel to the surface. To avoid this restriction, we newly assume that the forced vibration reflects at the position of a crack and spherical wave is radiated to the sensors. Some experiments were carried out, and good results were obtained in the case that crack was slanting to the surface of the block.