DOI: 10.7910/dvn/kvn7cy
title: Low-frequency ultrasound data (pulse-echo technique) with shear horizontal and longitudinal waves on a reference polyamide specimen “BAM-Pk218”

description: This dataset contains raw data observed with ultrasound measurements on a polyamide reference specimen at Bundesanstalt für Materialforschung und -prüfung (BAM), Berlin. The internal specimen identifier is „Pk218“. 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 was to determine both the specimen thickness and the position of a hole drilled parallelly to the measuring area.
The cuboidal specimen was made of the isotropic-homogeneous material polyamide PA6. The geometrical dimensions are l=1000 mm (length l corresponds to x-axis), b=600 mm (width b corresponds to y-axis) and d=294,5 mm (thickness d corresponds to z-axis). The hole was drilled through the entire width in y-direction and is parallel to the surfaces x/y and y/z. The hole diameter is D=50 mm. The depth of the hole centre is t=194,7 mm (z-axis) in relation to the measuring area, where z=0 mm. The lateral hole position is x=600 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 used pulse generator 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=101 and y=61 measuring points with a spacing of 10 mm in both directions. At each point, 4.000 samples were recorded with a sampling rate of 2 MS/s. The stored data are 16-bit (signed oder unsigned) integers in the range of A=±2000 mV. Two sets of data are provided, with the direction of polarization of the shear wave differing (x- and y-polarization, respectively). The 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 raw data are store line by line in x-direction.
The data is provided in the format *.csv and additionally in *.npy (Python).
description: Python, 3.8
description: numpy, 1.21.2
description: To ensure that a measuring position with the same coordinates in both datasets also correspond to the same measuring position on the specimen, the entire specimen surface was scanned. The centre of the rectangularly designed probe serves in all datasets 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. However, this means that the probe could not be entirely coupled to the polyamide in the edge areas of the specimen. In all datasets, full coupling is achieved from a distance of 7 cm to both component edges.
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 amount of the measuring points as well as the orientation of the probe polarization.
Example: 
Shear(*)_x001-x101(**)_y001(***)_Rot90(****): (*)-Type of wave (Longitudinal (Long) and shear wave (Shear), respectively); (**)-x001-x101: position number x = 1 to position number x = 101 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-x101_y001_Rot90.csv therewith consists of all data acquired in x-direction (101 measuring points) at position y=0 mm in y-direction. The shear horizontal waves are polarized in the y-direction.