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# Johnson Cook strength parameters for AISI 4130 Steel

## Johnson Cook strength parameters for AISI 4130 Steel

(OP)
Hi All,

I want to analyse the the deformation of a tubular space frame chassis by the means of a crash test simulation. I am using Abaqus and will use an explicit solver to analyse the short during event that will undergo highly nonlinear and transient forces. I am currently in the process of setting the material properties and want to define a "johnson cook parameter".

Now I am a new user to Abaqus so i am unsure what the best approach to take here would be. Within the material property under "plasticity". In the example that I have been following, the user has used an generic low graded aluminum material and at the section he has enetered the following parameters in the attatched picture.

If anyone has any experience wth using an explicit dyanmics solver within Abaqus then any information covering this would be greatly appriciated.

Is this just a simple case of plotting the Stress/Strain Curve for 4130 and from that I can derive the Plastic Strain?

Thanks

Ryan

### RE: Johnson Cook strength parameters for AISI 4130 Steel

The only problem is that strain rates in a crash are about 1,000,000 times those in a tensile test.
Hence, various strain rate dependent models.
The energy absorption, degree of deformation, and crack propagation mechanics all change at real high strain rates.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

### RE: Johnson Cook strength parameters for AISI 4130 Steel

You will need multiple stress-strain curves to start with simulation, a regular curve with low strain rate, and curves with higher rates up to the order of 10^3 per second to mimic crash. Each curve will give you one yield stress and corresponding plastic strain.
Johnson cook model includes three components: strain harden, strain rate harden, and softening due to adiabatic temp increase. strain harden component will be derived from the regular curve, strain rate harden will be derived from yield stress vs strain curve, softening component will be from adiabatic curves (density is needed).

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