Johnson-Cook - Hardening Exponent n

michael_s

Hi all,

 

I am simulating quasi-static compression tests of battery packs.

Due to the reason that this model should be used for high-velocity impact tests as well, it is necessary to set up the polycarbonate with the Johnson-Cook Material law.

 

According to

https://community.altair.com/community?id=community_question&sys_id=7ba600ba1b2bd0908017dc61ec4bcb7a

the hardening exponent n has to be between 0 and 1.

 

According to a publication of the 'Army Research Laboratory' the hardening exponent is evaluated to 2 for this specific polycarbonate test specimens (they carried out several compression tests at different strain rates and temperatures):

 

 

These JC parameters have already been used for other simulations. These simulations have been carried out with LS-DYNA. Here it is possible to enter a value for n which is larger than 1.

 

Furthermore i found hardening exponents for other materials which are larger than 1 as well.

 

So, do you have any recommendations what I could do?

 

Thanks a lot and kind regards,

Michael

Simon Križnik

Hi,

 

Unfortunately, no material law supports strain hardening exponent exceeding 1. 

 

As a workaround, try with material law 36 which is an isotropic elasto-plastic material using user-defined functions for the work-hardening portion of the stress-strain curve for different strain rates. While this material law does not have the convenience of describing the work hardening with only a few parameters, it allows describing the work hardening in greater detail with tabulated input.