Abaqus Output Strain E

[altaka]

I am doing elastic analysis of large deformations on Abaqus Student Edition 2021.
When I set the input file to output E and LE and looked at the result, the values ​​of E and LE are slightly different.
Since there is no plastic strain, I thought that the values ​​of E and LE would match. What is the cause of this?
The input file used is shown below.

* node, nset = nodes
1, 0.0, 0.0
2, 1.0, 1.0
3, 0.0, 2.0
* element, type = cps3, elset = elems
1, 1, 2, 3
* material, name = mat
* elastic
210.0, 0.3
** hyperelastic
** 0.1, 0.1, 0.1
* solid section, elset = elems, material = mat
1.0
* boundary
1, 1, 2
3, 1, 2
* step, nlgeom
* static, direct
1.0, 1.0
* CONTROLS, PARAMETERS = FIELD
1.e2, 1.e2,
* cload
2, 1, 50
* el print, elset = elems
E, LE
* output, field
* element output, elset = elems, variable = preselect
* node output, nset = nodes, variable = preselect
* matrix generate, stiffness
* element matrix output, elset = elems, stiffness = yes, outputfile = user
* end step

Thank you in advance.

 

[FEA way]

Check the documentation chapter "Conventions —> Stress and strain measures" to see how these two output variables (integrated strain E and logarithmic strain LE) are calculated in Abaqus. Keep in mind that there might be a small difference due to the nature of numerical calculations.

 

[altaka]

Dear FEA way
thank you for your answer.
When I investigated, I found that LE was calculated by log (B) in the large deformation.
B: left Cauchy–Green deformation tensor
Also, the calculation of E or EE was written in the manual as integration of the rate of deformation.
However, I did not know the specific integration method.
Do you know the material about the specific calculation method of E and EE?

 

[FEA way]

According to the aforementioned documentation chapter, it's a numerical integration of strain rate in a material frame of reference. You may find more details in the Theory Guide.