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Strain at yield

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This article is about the current version of DF.
Note that some content may still need to be updated.

Strain at yield is a mechanical property that materials possess. As with yield and fracture, there are six types of strain at yield, one for each of the six forces: impact, compressive, tensile, torsion, shear, and bending. Although in real life it represents the level of strain when forced by one of the forces, it is simplified greatly. Only impact strain at yield has been verified to have an effect.

A higher number means more strain (more flexible). A lower number means less strain (more rigid).

Elastic Modulus

The formula used by the raws to calculate strain at yield from a real-world elastic modulus value is the raw yield strength (in KPa) divided by the elastic modulus (in GPa/10 or Pa × 108). As it represents strain, this value is a dimensionless quantity.

For example, iron has an [IMPACT_YIELD] of 542,500 KPa and its bulk modulus is 170 GPa. (542500/[10 × 170]) = 319.1…, thus its [IMPACT_STRAIN_AT_YIELD] is 319.

An online material helper to simplify these calculations for modding can be found here: https://putnam3145.github.io/helper

Young's modulus is used for tensile and bending elasticity, the shear modulus is used for shear and torsion elasticity, and the bulk modulus is used for impact and compressive elasticity.

Strain at yield of materials

The strain at yield of materials is defined by the following tokens:

As stated above, only [IMPACT_STRAIN_AT_YIELD] has been observed to affect the material. Lower strain at yield materials will shatter when hit by an attack, even if the attack is with an edge weapon.

Material Strain at yield
Stone, Bone, Tooth, Horn, Hoof, Pearl, Shell, Soap, Tallow, Chitin, most frozen liquids 100
Metal template, Wood template, Plant template, Seed template, most powders 1000
Nail 5000
Cartilage 25000
Skin, Fat, Muscle, Sinew, Nerve, Organ template, Leather, Cheese, Leaf

Minimum for structurally elastic armor (clothing, mail)

50000
Hair, Feather, Scale, Silk, Thread 100000