How was the L, LT, ST coordinate system for Metals developed and adopted?

I am talking with some colleagues about comparing metallic and non-metallic materials. Obviously, "apples-to-apples" comparisons need to happen and that naturally means you need to equate certain directions in different coordinate systems.

This got me thinking: "how did MMPDS settle on L, LT, ST?" Was there resistance to forgings and extrusions being subjected to the same coordinate system (especially when you are looking at cylindrical vs non-cylindrical forms)? How were arguments against placing these various forms together in a single coordinate system resolved? Is there any documentation about the process that I could access, such as meeting notes?

Some Background

Materials' properties can vary with direction - this is called anisotropy. Various kinds of materials have "industry standard" coordinate systems so people know which directions people are talking about. For metals within aerospace engineering, this is the Metallic Materials Properties Development and Standardization organization. This group has determined (somehow?) that most directional properties can be described using their coordinate system, the orthogonally placed Longitudinal (or Long), Long Transverse, and Short Transverse directions. This allows for end products of varying metal-forming processes to be compared to each other: extruded vs cast vs forged etc. This sometimes, but not always, corresponds to grain directions. These grain directions, otherwise known as crystal orientations, are important to the materials behavior.

  • $\begingroup$ Meeting minutes for the last few years are at mmpds.org/meetings $\endgroup$
    – Jon Custer
    Sep 12, 2022 at 14:55
  • $\begingroup$ @JonCuster the problem is, of course, that these only cover the last several years, and this is something that was likely adopted very early on. A co-worker claims this system was approaching 100 years, but did not have a source. IDK who even made this! $\endgroup$
    – PipperChip
    Sep 12, 2022 at 15:41
  • $\begingroup$ Fair enough! I will confess to pointing to the accessible meeting notes, not actually going through them myself. If 100 years ago, one would have to find the written archives, should they even exist at this point, or some textbook at the time introducing them for the first time. $\endgroup$
    – Jon Custer
    Sep 12, 2022 at 15:46
  • $\begingroup$ "MMPDS settle on L, LT, ST" is a little cryptic... Could you at least give the explanation of these acrononyms ? $\endgroup$ Sep 13, 2022 at 19:37
  • $\begingroup$ @JeanMarieBecker How's that? I hope this is a bit more obvious. $\endgroup$
    – PipperChip
    Sep 13, 2022 at 22:56


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