DOI: 10.48804/gde9tw
title: LMSD 2021 Dataset for Damage Identification in Plates

description: &lt;h1&gt;LMSD 2021 Dataset for Damage Identification in Plates&lt;/h1&gt;

&lt;p&gt;These files contain data collected to experimentally validate damage identification methods for plate-like structures.&lt;/p&gt;

&lt;h2&gt;Experimental Setup&lt;/h2&gt;
&lt;p&gt;The inspected structure is a 600mm x 600mm x 4mm CFRP plate with crossply layup.
A 12 x 12 square grid of 144 nodes is defined on this plate, with 50mm spacing and 25mm offset from the edges of the plate.
The plate is hung with elastic bands to obtain free-free boundary conditions.
It is excited on its front-side with a PCB 086C03 impact hammer.
7 PCB 352a24 1D-accelerometers are installed on its back-side.&lt;/p&gt;

&lt;p&gt;Additional masses are glued to the plate to reproduce the scattering effect of damage.
Two types of scenarios are considered: point-like masses of 55g at pre-defined nodes on the grid and an elongated mass of 315g covering several nodes.
A total of 6 damage scenarios are considered, 5 point-like scenarios with 1, 3, 4, 5 and 6 added masses, respectively, and 1 elongated-mass scenario with 1 added mass.&lt;/p&gt;

&lt;p&gt;The included pictures summarize the experimental setup and show the 12 x 12 grid of nodes with the position of the 7 accelerometers/hammer impact locations in black and the positions of the added masses in red (the number labels at a given position indicate which scenarios have a mass added at that position).
Zoomed views are also provided of a 55g point-mass and a 315g elongated mass, glued to the plate.&lt;/p&gt;

&lt;h2&gt;Data Acquisition Procedure&lt;/h2&gt;
&lt;p&gt;To obtain the baseline FRFs, the responses are measured on the healthy plate from all 144 nodes to the 7 accelerometer nodes.
To obtain the damaged FRFs, the responses are measured on the damaged plate from the 7 accelerometer nodes to the 7 accelerometer nodes.
The resulting damaged responses form what is also referred to as the multistatic data matrix.
Each measurement is repeated 5 times and the responses are averaged to increase the SNR.
The measured FRFs consist of 8192 frequency bins between 0Hz and 1600Hz.&lt;/p&gt;

&lt;h2&gt;Data Structure and Organization&lt;/h2&gt;
&lt;p&gt;The baseline file contains:
&lt;ul&gt;
&lt;li&gt;frf 7x144x8192 double: baseline frf from all 144 nodes to the 7 accelerometer nodes.
&lt;li&gt;frequency 1x8192 double [Hz]: the frequencies in Hertz.
&lt;li&gt;node_position 144x2 double [mm]: position of the nodes in millimeters.
&lt;li&gt;probing_nodes 1x7 uint16: indices of the accelerometer nodes, which are also the nodes that receive hammer excitation to collect the damaged responses.
&lt;/ul&gt;
&lt;/p&gt;

&lt;p&gt;Each damage scenario is associated to a file with a corresponding, descriptive filename. Each of the files contains:
&lt;ul&gt;
&lt;li&gt; frf 7x7x8192 double: damaged frf from the 7 accelerometer nodes to the 7 accelerometer nodes (also referred to as multistatic data matrix). By convention, frf(i, j, :) is the frf measured at accelerometer i when a hammer excitation is applied at the location of accelerometer j.
&lt;li&gt;mass_nodes 1xn uint16: indices of the nodes at which a mass is added.
&lt;/ul&gt;
&lt;/p&gt;

&lt;p&gt;The datasets are provided both as mat files and npz files, alongside with helper functions to conveniently load the data and accelerate collaboration.
Note that the mat files use MATLAB-compatible indexing (i.e. node numbering starts at 1) while the npz files use conventional zero-based indexing (i.e. node numbering starts at 0).
For this reason all node indices in the probing_nodes and mass_nodes variables are offset by one in the mat files compared to the npz files.&lt;/p&gt;

&lt;p&gt;Helper functions and examples demonstrating how to load and process the data are provided alongside this dataset under MIT Licensing.&lt;/p&gt;

&lt;h2&gt;Licensing&lt;/h2&gt;
&lt;p&gt;Data produced and made available by the LMSD group, KU Leuven, under CC BY 4.0 Licensing.&lt;br&gt;
Code written by Nathan Dwek with the LMSD group, KU Leuven, made available under MIT Licensing.&lt;/p&gt;

&lt;h2&gt;Citing this Work&lt;/h2&gt;
&lt;p&gt;If you use the data itself directly, please cite this dataset appropriately. Proper citation text can be found on the dataset webpage in multiple formats.&lt;/p&gt;

&lt;p&gt;Please cite the relevant publication(s) below if your work is based on or compares to the damage identification methods they introduce:
&lt;ul&gt;
&lt;li&gt;N. Dwek, V. Dimopoulos, D. Janssens, M. Kirchner, E. Deckers, and F. Naets, "Damage Identification in Plate-Like Structures Using Frequency-Coupled L1-Based Sparse Estimation," (Pre-print submitted to MSSP, October 31, 2023). Available at &lt;a href="https://ssrn.com/abstract=4644311"&gt;SSRN&lt;/a&gt;. doi: &lt;a href="https://doi.org/10.2139/ssrn.4644311"&gt;10.2139/ssrn.4644311&lt;/a&gt;
&lt;li&gt;N. Dwek, D. Janssens, M. Kirchner, and E. Deckers, "Sparse Damage Identification at Off-Grid Locations on Plate-like Structures using Frequency-Coupled Group Lasso," to be presented at the 2024 European Workshop on Structural Health Monitoring, June 2024.
&lt;/ul&gt;
&lt;/p&gt;

&lt;h2&gt;Contact&lt;/h2&gt;
&lt;p&gt;Nathan Dwek - &lt;a href="mailto:nathan.dwek@kuleuven.be"&gt;nathan.dwek@kuleuven.be&lt;/a&gt;&lt;br&gt;
LMSD Group - &lt;a href="mailto:lmsd@kuleuven.be"&gt;lmsd@kuleuven.be&lt;/a&gt;&lt;br&gt;
Department of Mechanical Engineering&lt;br&gt;
KU Leuven&lt;br&gt;
Belgium
&lt;/p&gt;