Hi,

I am analysing a high impact crash at high speed (50m/s). I am mostly interested in the deformation and the load paths of the structure.

Ansys provides many default materials. One area of which are "explict materials" which include properties relevant to explicit impacts ( i must admid, materials is not a strong area of mine). Annoyingly it doesnt feature my chosen material (4130 steel) the closest available is 4340 which is a much stronger material. Therefore i have to create my own 4130 material.

So far I have defined my 4130 meterial by including the following mechanical properties.

Density

**Isotropic Elasticity** (*Youngs modulus, Poissons ratio, Bulk Modulus, Shear Modulus)*

**Bilinear Isotropic Hardening** (*Yield strength, tangent modulus*)

if i want to model plasticity of the part then Do I need to use one of the following:

**Johnson cook strength** (need test data)

**Bilinear isotropic.(**relevant?) I only used this as I could define the tangent modulus and assume a "perfectly plastic" material.

Originally i did model the material as "perfectly plastic" (tangent modulus within Bilinear Isotropic) so when an area subject to load exceeded yield then the part would essentially give up. At first I thought that this woudl be what I was looking for, however upon impact the structure resembles a bowl of spagetti (I am analysing a Tubular space frame chassis).

What would be the best approach to take in regards to modelling the 4130 material in a explicit condition.

Thank you

R.