How does Abaqus calculate strain and strain increment from displacement?

[falloutranger]

I have two questions concerning strain in Abaqus:
1. In Abaqus CAE, the user can only specify as boundary conditions the applied displacement and time. So how does Abaqus calculate the applied strain and strain increment, especially for non-linear problems where the relation between displacement and strain is non-linear?

2. What is the Jacobian matrix used for in Abaqus? For example, when you run a UMAT subroutine, it needs to pass stress and Jacobian matrix back to Abaqus at the end of every increment. Does Abaqus use the Jacobian matrix at all? Does it use the Jacobian matrix to calculate the strain increment (DSTRAN) that it needs to apply in the next step? If so, how does it calculate DSTRAN ?

 

[IceBreakerSours]

Both of your posts makes me suspect you are new to the FEM world. If that is the case, then you should take - at the very least - a good introductory course on FEM. If it is unavailable, there are many resources available online for free - books/lecture notes/video lectures - while great, none of which will be as valuable as taking a course. NAFEMS offers certification, which may be quite valuable as well. Finally, Abaqus documentation answers all of your questions very well.

*********************************************************
Are you new to this forum? If so, please read these FAQs:

http://www.eng-tips.com/faqs.cfm?fid=376

http://www.eng-tips.com/faqs.cfm?fid=1083

 

[ShadowWarrior]

Same question asked by OP -

https://www.reddit.com/r/fea/comments/430uu6/how_does_abaqus_calculate_strain_and_strain/

 

[testing]

He also posted the same questions in /r/engineering as well