A-AMB2022-01 Benchmark Frequently Asked Questions

A-AMB2022-01 Benchmark Frequently Asked Questions

• Why are the videos at an angle? Is the sample at an angle or the laser? If the sample, is it tilted with respect to gravity?
  • The laser beam is vertical and aligned with gravity.  Horizontal is defined as orthogonal to the laser/gravity, and the sample surface is tilted 7 degrees from horizontal. This tilt is necessary for the integrating sphere so that the initially strong specular component of the reflected light does not escape through the laser entrance port on the sphere.

• What is the surface roughness and preparation of the aluminum samples?
  • The top surface where the laser is incident is polished to a specular (i.e. highly reflective) finish. The same is true for the sides where the X-ray beam is incident to and exits from.

• What are the differences between raw and processed X-ray images?  Which should we use for comparison?
  • The “raw” images come directly from the high-speed camera used for the X-ray images. These are provided so that the participant can apply whatever image processing tools they wish. We have also provided our processed images that we have applied our own methods to. This process has been detailed in one of the provided publications. The participant can choose whichever set of images suits their use.  

• Will keyhole/melt pool measurements from the images for Ti-6Al-4V be provided? If not, will scale information will be available?
  • We will not provide our own measurements of the melt pool features from the images. The scale of the images is 1.923 micrometers per pixel.

• Will the material properties of any of the alloys (Ti and Al) required for computational modeling be made available?
  • Only the material composition of the alloys is given, both of which are NIST Standard Reference Materials (SRM). The Ti-6V-4Al alloy is NIST SRM 654b and the Al 5182 is NIST SRM 1241c. The certificates of analysis for these materials can be found by searching the SRM number at https://www.nist.gov/srm. 

• Is there a reason why this challenge is released first, rather than being released with other tasks?
  • AM-Bench benchmarks are typically large sets of interrelated measurements released on a three-year cycle.  To provide additional flexibility, we have introduced smaller sets of benchmarks that are asynchronous with these regularly scheduled benchmarks.  A-AMB2022-01 is the first of these asynchronous benchmarks.  The release of this asynchronous benchmark also provided the opportunity for the AM Bench teams to test their new data curation and data publication machinery before the much larger AM Bench challenge releases in April.

• Can the same group submit multiple sets of results (we might use different methods to predict the same measures)?  What is a "group"; an institution or can there be multiple groups within an institution?
  • An individual research group may submit multiple sets of results but must specify in advance a single set of results to be used for the judging.
  • Multiple research groups from the same institution are free to submit results, but these groups must be independent.  For cases where this is not clear, please contact Lyle.Levine [at] nist.gov (Lyle[dot]Levine[at]nist[dot]gov).

• Oxygen content in chamber?
  • The experiments were performed in an argon gas environment at atmospheric pressure. The oxygen content was not measured.

• Is laser scan speed given relative to the laser, or the angled sample?
  • The laser scan speed is given with respect to a horizontal surface at the sample position.

• Is there any effect of vapor plume on the power measurement? Since, all of these are keyhole cases there can be substantial attenuation of the laser beam. Will it influence the accuracy of power measurement?
  • In this study, we do not provide information about the vapor plume. We leave it up to the participant to determine what effect, if any, this may have on our measured results.

• The experimental configuration is nearly identical, except that the calibration sample width is 300 um and the challenge sample width is 1 mm?
  • That is correct. The Ti-6V-4Al sample used for the calibration data was 300 micrometers thick in the direction through which the X-ray beam transverses. The Al sample used for the challenge data is 1 mm.

• In the Ti64 scanning cases, maximum depth is at the beginning of the simulation. Do we need to submit the maximum depth or the depth at the quasi-steady state?
  • For the challenge problems, the maximum depth is the maximum depth at any point during the entire laser exposure.

• Is the 7-degree inclination in the same direction for the scans of the calibration and challenge configuration?
  • Yes, the tilt direction is in the same direction for all samples. The raw and processed images have the correct tilt direction, but some images were flipped along the vertical axis when making the example movies for visual effect.

• Are the laser powers the same for the calibration and prediction? In that case why does the provided .csv file power column only go up to 100 W?
  • The laser powers were different, but the measured laser powers are given for all cases. The power for the calibration data is given in the .csv files containing the absorption information. The laser power for the challenge problems are found in the template files used to record and submit the solutions.