# Jump condition for elasticity on an interface **URL:** \ **Category:** General Discussion\ **Created:** [May 22, 2025, 2:19pm UTC](https://community.freefem.org/t/jump-condition-for-elasticity-on-an-interface/3930 "2025-05-22T14:19:28Z")\ **Posts on this page:** 1\ **Showing post:** 2
**Author:** ![fb77](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/fb77/32/3796_2.png) [@fb77](https://community.freefem.org/u/fb77)\ **Post date:** [May 22, 2025, 6:58pm UTC](https://community.freefem.org/t/jump-condition-for-elasticity-on-an-interface/3930/2 "2025-05-22T18:58:36Z")
Dear Loïc, Instead of using `intalledges` you can use `int1d(Th,5)`, and `jump` will be available. For the second term, you have to take the integral “from the outside”. For that you need to have a clockwise orientation of \Gamma. About the int1d on an internal boundary of a discontinuous function (and the related orientation issue), see > [@Normal stress in a horizontal line inside of a mesh from top side only](https://community.freefem.org/t/normal-stress-in-a-horizontal-line-inside-of-a-mesh-from-top-side-only/3717/2): > > Hello, Your approach is correct. Using buildmesh you can put a border that is inside the domain. Then it has a label (1 in your case) that can be used to compute int1d(Th,1)(). This “internal border” is considered as a boundary. In particular if you write int1d(Th) without mentioning a label, it will integrate on all boundaries, including the “internal boundary”. When you have a finite element function u that is discontinuous through the internal boundary (for example if u is P0 on Th), your… But take care that in order to keep the inside region in you mesh (and not exclude it), for a clockwise orientation of \Gamma you will need to apply `buildmesh` with a negative number on border 5, like `mesh Th=buildmesh(b1(10)+b2(10)+b3(10)+b4(10)+b5(-20));` François. --- _[View the full topic](https://community.freefem.org/t/jump-condition-for-elasticity-on-an-interface/3930)._