Green's strain measure in Abaqus

[pocoyo]

Many papers and texts mentioned Green's strain as the appropriate measure when dealing with large strain. However, in Abaqus Theory Manual, it says that Green's strain measure is often used for problems involving large motions but only small strain. Why these are different and what should be understood about "small strain" in Abaqus. And what is a strain measure to be used for problems involving large motions and large strain?
Many thanks,

Pocoyo

[Jorgen]

Some of the confusion might be related to the use of different definitions of Green strain.

There are many different types of strain that are suitable for large arbitrary deformations. Most common, I would think, are the logarithmic (true) strain defined by: ln[v], and the Green strain defined by: 0.5*[v^2 -1]. In these equations v is the left stretch tensor. Both of these strain measures are suitable for large deformations.

- Jorgen

[pocoyo]

Dear Jorgen,

Thank you for the reply.
Yes I am still confused about this as I am new in using large strain measures. Can you suggest where I can find information of "different definitions of Green strain", especially for those used in Abaqus.

For large deformation in compression, is it more appropriate to use Log strain measure than Green strain measure, and it is opposite in large deformation in tension?

Many thanks,
Pocoyo

[Jorgen]

When I mentioned different types of Green strain, I was mainly referring to the difference between Lagrangian and Eularian strains. And as you know, ABAQUS is using Eularian strains.

I claim that one type of strain is not more appropriate than any other type of strain, even in large deformations. What is important is to keep track of the type of strain that is used and write the constitutive equations appropriately.

- Jorgen