repo-test-doc: Accompanying data for the paper "Crack branching at low tip speeds: spilling the T"
# Contribution
* Elie Eid contributed to the experiments, their analysis, the numerical simulations and the writing of the paper.
* Rian Seghir contributed to the experiments and the fullfield measurements. He also contributed to the writing of the paper.
* Julien Réthoré contributed to the experiments and to the writing of the paper.
# Data collection: period and details
* Data have been collected during July 2021
# Funding sources
* Connect Talent IDS project funded by Région Pays de la Loire, Nantes Métropole and Ecole Centrale de Nantes with the additional support of of European Union.
* French Research National Agency programme through grant ANR-16-CE30-0007-01
# Data structure and information
- Four SCDC (Single Crack Direct Compression) specimens are dynamically loaded via an impact on the edge perpendicular to the notch.
- Specimens are mounted on a waveguide to ensure proper compressive wave entering the specimen and to hold the sample while keeping all other boundaries free.
- The impact induces a compressive wave; however, the presence of the hole creates a tensile zone sideways opening thus the notch and enabling the fracture initiation.
- Due to the absence of an impedance at the right-hand side boundary, stress-waves are fully reflected from the right-hand side boundary and deliver new loading-unloading conditions of the crack-tip modifying its advancement eventually leading to branching.
- Samples are laser-cut from a commercial PolyMethyl Methacrylate (PMMA) manufactured by Arkema. The pre-crack’s width matches the beam’s, ie. 200um. A synthetic speckle pattern is laser-engraved onto the sample surface (useful for ensuring quality and reproducibility of the pattern for the application of the DIC procedure).
- All images are captured using the High-spatial Resolution and Ultra-high speed (HR-UHS) Cordin camera Model 580 at 400 kfps with a resolution of 3296 x 2472 pixels. Field of view is 154.25mm x 115.69mm leading to a pixel size of 0.0468mm.
- `Ufreckles` is used to perform FE-based DIC using T3P1 linear triangular elements and a Tikhonov regularisation (over 3 elements). Eventually, Linear Elastic Fracture Mechanics (LEFM) parameters are obtained post-projecting displacement fields on Williams' series using Ufreckles.
- [https://zenodo.org/badge/DOI/10.5281/zenodo.1433776.svg](https://doi.org/10.5281/zenodo.1433776)
- [https://archive.softwareheritage.org/badge/swh:1:dir:73fae3c4e4fce0f9a2c36a7ccf3a7be7c229c5ca/](https://archive.softwareheritage.org/swh:1:dir:73fae3c4e4fce0f9a2c36a7ccf3a7be7c229c5ca;origin=https://github.com/jrethore/ufreckles;visit=swh:1:snp:9c0d967db98cef7f2b5d1dca641d392f75794b80;anchor=swh:1:rev:c83ced7bf43f3bd717f85c82a39c8cce2a5515db)
- Complete analysis of the data can be found in [Eid, E., Seghir, R., & Réthoré, J. (2023). Crack branching at low tip speeds: spilling the T. Journal of Theoretical, Computational and Applied Mechanics.]
## All test directories contain:
_Data_
- `raw images`: in /images/ folder in 16bit .tiff format
- `the timeline`: at root (time.txt) in µs
- `a distortion model`: at root (Distortion.mat) containing camera distortion modes and amplitudes for each camera sensor
- `a mesh`: at root (mesh_crack_conform.vtk) for FE-based DIC
- `VTK result fields`: in /Results/VTK/ containing experimental DIC mesh, nodal displacement, velocity and accelerations fields and elementary strain and strain-rate fields for each frame
- `Fracture parameters`: in /Results/VTK/LEFM.txt containing the identified LEFM parameters (for the main crack propagation from initiation to branching frames)
_Matlab Codes_ to produce results (working with Ufreckles)
- `MultiSensor_DIC_script.m`: in /Codes/ is the main script to run DIC
- `Shape functions`: in /Codes/shape_functions/ containing Zernike polynomial shape functions and deconvolution algorithm to get effective displacement from total displacement knowing camera distortions
## One directory per tested specimen:
- `T3DE`: impacted at a projectile velocity of 31.8 m/s
- `TAF1`: impacted at a projectile velocity of 30.5 m/s
- `TAF2`: impacted at a projectile velocity of 22 m/s
- `THOM`: impacted at a projectile velocity of 22 m/s