Chekroun M, Le Marrec L, Abraham O, Durand O, Villain G
Laboratoire Central des Ponts et Chaussées, Nantes, France.
Ultrasonics. 2009 Dec;49(8):743-51. doi: 10.1016/j.ultras.2009.05.006. Epub 2009 May 31.
Rayleigh waves measurements are used to characterise cover concrete and mortar in the frequency range 60-180 kHz. At these frequencies, the wavelength is comparable to the size of the aggregates, and waves propagate in a multiple scattering regime. Acquired signals are then difficult to interpret due to an important incoherent part. The method proposed here is the study of the coherent waves, obtained by averaging signals over several configurations of disorder. Coherent waves give information on an equivalent homogeneous medium. To acquire a large amount of measurements with accuracy, an optimised piezoelectric source is used with a laser interferometer for reception. Adapted signal processing technique are presented to evaluate the coherent phase and group velocities and also the coherent attenuation parameter. The sensitivity of these three parameters with the properties of concrete is discussed, as well as the necessity to use coherent waves to obtain accurate results.
瑞利波测量用于表征频率范围在60 - 180千赫兹的覆盖混凝土和砂浆。在这些频率下，波长与骨料尺寸相当，波在多重散射状态下传播。由于存在重要的非相干部分，采集到的信号难以解释。这里提出的方法是研究相干波，通过对几种无序配置的信号进行平均获得。相干波给出了等效均匀介质的信息。为了精确获取大量测量数据，使用了优化的压电源与激光干涉仪进行接收。还介绍了适用的信号处理技术，以评估相干相速度和群速度以及相干衰减参数。讨论了这三个参数对混凝土特性的敏感性，以及使用相干波获得准确结果的必要性。
