Low-frequency ultrasound data (pulse-echo technique) with shear horizontal and longitudinal waves on the step-shaped concrete specimen “Pk050”

This dataset contains raw data acquired in ultrasound measurements on a reference specimen made of concrete at Bundesanstalt für Materialforschung und -prüfung (BAM), Berlin (Germany). The internal specimen identifier is “Pk050”. The measurements were conducted using the pulse-echo method. The upper surface of the specimen was defined as measuring area. The aim of the measurements is to determine the geometrical dimensions (thickness) of the specimen “Pk050”. In addition to this, a dataset of a second specimen with identifier “Pk266” has been acquired. Pk266 has the same geometrical dimensions and concrete recipe as Pk050, but contains tendons [Reference: https://doi.org/10.7910/DVN/NUU0WZ]. The step-shaped specimen was made of the heterogeneous material concrete with a maximum aggregate size of D = 16 mm. The geometrical dimensions are l=2000 mm (length l corresponds to X-axis), b=800 mm (width b corresponds to Y-axis) and an step-wise thickness: d_1=571.3 mm, d_2=452.0 mm, d_3=330.9 mm and d_4=210.8 mm (thickness d corresponds to Z-axis). Each step has a length of about l=500 mm. The measurements were conducted with both commercially available and self-developed equipment. The ultrasonic probes M2502 (Dual Aperture Shear Wave DPC Transducer Array) and M2503 (Dual Aperture Longitudinal Wave DPC Transducer Array) are manufactured by the Acoustic Control Systems – ACS Group. The pulse generator used is a BAM in-house development. For data acquisition, a National Instruments USB-6316 system in 16-bit format has been used. The measurements were performed mechanized with an automated scanner system which was designed at BAM. The scanner is operated with a self-developed control and data acquisition software based on the programming language LabVIEW. The measuring grid consists of X=187 and Y=71 measuring points with a spacing of 10 mm in both directions. The start point for the measurement field is in X-axis 7 cm and in Y-axis 5 cm. At each point, 4000 samples were recorded with a sampling rate of 2 MS/s. The stored data are 16-bit signed integers in the range of A = ±2000 mV. For the complete description of the real dimensions of the measuring surface with a length of l=2000 mm and a width of b=800 mm the missing data points are filled with zero vectors. This means that in total there are 201 data points on the X-axis and 81 data points on the Y-axis. Two sets of data are provided, with varying direction of polarization of the shear waves (X- and Y-polarization, respectively). The three additional -vector- datasets contain the X- and Y- coordinates of the individual measuring points in mm as well as the Z-position of the samples in µs. The data is provided in the format *.csv and additionally in *.npy (NumPy).

本数据集包含在德国柏林联邦材料研究与测试研究所（Bundesanstalt für Materialforschung und -prüfung, BAM）开展的混凝土标准试样超声测量中获取的原始数据。试样内部标识符为"Pk050"，测量采用脉冲回波法（pulse-echo method），以上表面作为测量区域。本次测量的目的是确定试样"Pk050"的几何尺寸（厚度）。此外，本数据集还包含标识符为"Pk266"的第二份试样的测量数据：该试样与Pk050具有相同的几何尺寸与混凝土配合比，但内置预应力筋[参考文献：https://doi.org/10.7910/DVN/NUU0WZ]。

该阶梯状试样由最大骨料粒径D=16 mm的非均质混凝土制成，几何参数为：长度l=2000 mm（长度l对应X轴）、宽度b=800 mm（宽度b对应Y轴），阶梯状厚度分别为d₁=571.3 mm、d₂=452.0 mm、d₃=330.9 mm及d₄=210.8 mm（厚度d对应Z轴），每个阶梯段的长度约为500 mm。

本次测量采用商用及自研设备完成：超声探头M2502（双孔径横波DPC换能器阵列(Dual Aperture Shear Wave DPC Transducer Array)）与M2503（双孔径纵波DPC换能器阵列(Dual Aperture Longitudinal Wave DPC Transducer Array)）由声学控制系统集团（Acoustic Control Systems – ACS Group）制造；脉冲发生器为BAM自研设备；数据采集采用16位格式的National Instruments USB-6316系统。测量由BAM设计的自动化扫描系统机械化完成，该扫描系统搭载基于LabVIEW编程语言开发的自研控制与数据采集软件运行。

测量网格包含X轴187个、Y轴71个测量点，双向间距均为10 mm。测量场的起始点位于X轴7 cm、Y轴5 cm位置。每个测量点采集4000个采样点，采样率为2 MS/s。存储数据为16位有符号整数，幅值范围为A=±2000 mV。为完整描述总长l=2000 mm、总宽b=800 mm的测量表面的实际尺寸，缺失的测量点以零向量填充。这意味着X轴总计201个数据点，Y轴总计81个数据点。

本数据集包含两组数据，分别对应横波的两种极化方向（X极化与Y极化）。另有三组附加向量数据集，分别包含各测量点的X、Y坐标（单位：mm）以及采样的Z轴位置（单位：µs）。

数据以*.csv格式提供，同时提供*.npy（NumPy）格式文件。