# Large deformation strain

**URL:** <https://community.freefem.org/t/large-deformation-strain/1498>\
**Category:** General Discussion\
**Created:** [February 15, 2022, 11:27am UTC](https://community.freefem.org/t/large-deformation-strain/1498 "2022-02-15T11:27:02Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![amir](https://avatars.discourse-cdn.com/v4/letter/a/c37758/32.png) [@amir](https://community.freefem.org/u/amir)\
**Post date:** [February 15, 2022, 11:27am UTC](https://community.freefem.org/t/large-deformation-strain/1498/1 "2022-02-15T11:27:02Z")

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Hi,  
How can I write green strain?? I have a problem with the nonlinear term.

![strain](https://canada1.discourse-cdn.com/flex030/uploads/freefem/original/1X/11a77c591749e823a35d2133b29d378280a95b01.png)

There is einstein notation on index k.