diffmpm Working on Bingham Material

Issue #9

Jul 02 '23 13:07 SachinJalan

I had a doubt in bingham.tcc file, in the function compute stress Eigen::Matrix<double, 6, 1> mpm::Bingham<Tdim>::compute_stress( const Vector6d& stress, const Vector6d& dstrain, const ParticleBase<Tdim>* ptr, mpm::dense_map* state_vars)

can you please tell what is the state_vars.

Jul 02 '23 20:07 SachinJalan

I haven't implemented state variables yet but I think it's just a dictionary. See

https://github.com/cb-geo/mpm/blob/53fcb7609375fd44bf3481d24ee18bfdf0393adb/include/materials/bingham.tcc#L32-L37

Jul 02 '23 20:07 chahak13

Yes, it's a dict to store variables specific to individual material points

Jul 02 '23 21:07 kks32

In the particles.py class the init function does not have dvolumetric_strain while it has been computed in later functions of the same class.

Jul 03 '23 14:07 SachinJalan

Thanks for pointing that out. I added it to the init method. The reason it worked fine was that every time a new value is assigned to it so it was not needed to be carried over by jax (un/)flattening but better to have it there.

Jul 04 '23 20:07 chahak13

In the test cases of bingham material I am getting a deviation from the answer present in the CB-Geo test case from bingham in case 3 and 4 which are for yielded case, The tau value is coming off by a value of 20-30 I have checked the code multiple times but am unable to find any error, the dvolumetric strain is coming correct. I think the strain rate has some error it is coming [-0.25,-0.375,0.0,-0.625,0,0] can you please see once

Jul 12 '23 11:07 SachinJalan

@SachinJalan Let me see if I can find something. Can you be a little clearer about where you think the error is stemming from? Trying to pin in the issue - you say dvolumetric_strain is correct but the strain rate isn't? What would be the expected strain rate?

Jul 14 '23 03:07 chahak13