# Johnson Cook Plasticity Model

## Copper material modelling using Johnson Cook model in LS DYNA

Choose a channel featured in the header of iMechanica:

Hello,

## Vuhard

hello

i am using modified JC model for the simulation of segmented chip formation in machining of Ti64 alloy and i wrote a VUHARD subroutine for that,but two problem arises,

1.the simulation stops at higher value of frictional co-efficient and

2.the feed force is under predicted

since i didn't use dyieldDeqps,is it necessary?

plz help!

## Plotting the Johnson-Cook strength model

I'm trying to plot the stress-strain curve described by the Johnson-Cook strength (and eventually damage) models. The strength model is defined as:

σ=[A+Bεn][1+C ln(ε_dot*)][1-T*m]

where A, B, C, n, and m are material constants, ε_dot* is the non-dimensionalized strain rate, and T* is the homologous temperature where T*=(T-T0)/(Tmelt-T0)

To calculate the thermal softening (term in the last bracket of the J-C model), I need to determine the increase in temperature related to an increase in stress (and strain). I'm using the following equation:

## Naming of an "Epsilon Dot Zero" And a "Reference Strain Rate" of J-C Parameters in Abaqus/Explicit

Hello,

I'm a little bit confused with a naming convention of strain rates of Johnson-Cook plasticity and damage model in Abaqus. In J-C equations there are two parameters:

• ε.0 (epsilon dot zero) known as a reference strain rate which has the value of 1 s-1,
• ε. (epsilon dot) known as the plastic strain rate or the effective strain rate [s-1].

In Abaqus (Edit Material window), there are two parameters with the same(?) name:

## Johnson Cook Mathematical model

Dear friends,

Can anybody give me information/Website/papers/... on below mentioned topic ??

on Johnson Cook plasticity model with analytical forms of the hardening law and rate dependence. I am trying to use this in my high-strain-rate transient dynamic simulations (metals). I am using ABAQUS as analysis tool.

Thanks a ton in advance !

-Balappa Bhairnatti.

Tooltech Deutschland

Munich. 