DOI: 10.7910/dvn/9eid5d
title: Low-frequency ultrasound data (pulse-echo technique) with shear horizontal and longitudinal waves on the step-shaped concrete specimen “Pk050”

description: 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).
description: Python, 3.8
description: NumPy, 1.21.2
description: In all datasets, the centre of the rectangularly designed probe serves as reference point for the description of the X- and Y-coordinates, so that the rotation of the probe by 90° (Rot90) does not lead to inconsistencies. This rotation is required to change the direction of polarization and to vary the directional characteristic of the respective acoustic field, which depends on the aperture, simultaneously. 
The original data has been converted to *.csv and *.npy using the Python csv and NumPy libraries.
The filenames of the raw datasets (provided in *.csv-format) contain information about the number of measuring points as well as the orientation of the probe polarization.
Example: Pk050(*)_Shear(**)_X001-X201(***)_Y001(****)_Rot90(*****): (*)-Name specimen; (**)-Type of wave (Longitudinal (Long) and shear wave (Shear), respectively); (***)-X001-X201: position number X = 1 to position number X = 201 on X-axis; (****)-Y001: position number Y = 1 on Y-axis; (*****)-Rot90: polarization of shear wave in Y-axis (var. 1), Rot00: polarization of shear wave in X-axis (var. 2). The dataset named e.g. Shear_X001-X201_Y001_Rot90.csv therewith consists of all data acquired in X-direction (201 measuring points) at position Y = 0 mm in Y-direction. The shear horizontal waves are polarized in the Y-direction.