Aaaaagh. Modding values is giving me a headache. What exactly do these tags mean, in simple English:
The simple English meanings pertain to the real world, not DF; check Wikipedia for them.
The way to use them is just to base them on an existing material, then make any changes you want to make(like double
*_YIELD and
*_FRACTURE, halve
*_STRAIN_AT_YIELD, and you get a material noticeably better.) This is more known for weapons than armor, but:
DF uses the
IMPACT_* params for blunt weapons, and possibly armor vs blunt. Similarly it uses
SHEAR_* for sharp, although there's a rumor
TORSION_* matters for sharp weapons penetrating armor.
TORSION_* and the remainder are used for wrestling.
With
*_YIELD and
*_FRACTURE, high is good; with
*_STRAIN_AT_YIELD AKA
*_ELASTICITY, low is good. For armor, raising all three may produce "mongolian silk" and lowering all three may produce something more rock-like, but I haven't tested that, it's based on assuming DF is like RL.
This all suggests it's not possible to make something good at being a weapon but bad at being an armor or vice versa(except by using density for blunts and
MAX_EDGE for sharps), which is weird(especially in a game), but the current system is clearly first-pass anyway.