TITLE: Serial killer pore investigation: protocol for analyzing fatigue failure pores in additively manufactured Ti6Al4V
AUTHORS: Muofhe Tshibalanganda, Anton du Plessis, Stephan le Roux

[DESCRIPTION]
<div class = "text-blocks"><div class = "text-block">This protocol outlines the steps followed to determine a potential "killer pore" in the area of failure of DMLS Ti6Al4V specimen. </div><div class = "text-block">The methodology can be used more generally for positively identifying and quantifying small isolated pores in additively manufactured metals. In this case the focus was on analysis of a 4 mm region near the eventual fracture surface, to identify all pores in the vicinity of the "killer pore" - the one causing failure by fatigue tests. This protocol was developed for Ti6Al4V with 99.99% density (only small amount of porosity, very small pores only), tensile fatigue specimen round dogbone geometry with 5 mm gauge width.</div></div>

[STEPS]
?. [Before Scanning]
Wrap the sample inside a bubble wrap for support. Make sure the marked threaded grip is facing up.This is to know which side is up when analysing.
?. [Sample mounting]
Load the sample on a foam (e.g. florist oasis).
?. [Scanning Stettings]
The sample was scanned using the scanned using Phoenix V|Tome|X L240 (General Electric Sensing and Inspection Technologies Phoenix X-ray, Wunstorff, Germany) microCT system.   AB1Voltage160kV2Current100 µA3X-ray Sensitivity44Voxel size15 µm5Timing333 m/s6Images8007Averaging28Skip1
AB1Voltage160kV2Current100 µA3X-ray Sensitivity44Voxel size15 µm5Timing333 m/s6Images8007Averaging28Skip1
?. [Recontruction]
Reconstruction of the 3D data is done using General Electric Datos 2.2, using specifically beam hardening correction value of 8 - this reduces beam hardening artefacts significantly.
?. [Porosity analysis]
Analysis of 3D data is described here using Volume Graphics VGSTUDIO MAX 3.2 .
?. [Porosity analysis]
Register the sample - use simple registration to turn the sample upright in the software windows.
?. [Porosity analysis]
De-noising is done using the filters Adaptive Gauss with smoothing factor 0.8, edge threshold=0.1, iteration=1 and create a new volume.
?. [Porosity analysis]
Perfom the poroity analysis using Probability 0minimum voxel 8Maximum voxel 400Auto threshold deviationDeviation factorSelect the edge distance calculation
?. [Porosity analysis]
Use the ellipse Region of interest to crop the sample  excluding the area with the cone beam artefact.
?. [Porosity analysis]
Extract the region of interest to create new volume.
?. [Porosity analysis]
Define the material by using the automatic and advanced mode surface determination.
?. [Porosity analysis]
In the area of failure crop out 4 mm
?. [Porosity analysis]
Denoise using the non local mean filter using the smothing factor 2
?. [Porosity analysis]
Define the material by usinng surface determination. Use the automatic and advanced mode.
?. [Porosity analysis]
Sort by minimum edge distance to clearly define the potential crack intiating pores closest to the surface.
?. [Porosity analysis]
Save the defect analysis as csv file.
?. [Porosity analysis]
The data is saved including the filtered data set, as a image stack (tiff). These can be viewed manually without special software. The analyzed volume can be opened in free myVGL software.