Learning Forum

[cplasf1998]

May I ask how the positive and negative values of internal forces in a shell element are defined? If the direction is the same as the element coordinate system, it is positive; otherwise, it is negative. For example, N22 and N11 are both tensile forces, so are their values negative?

[mjmiddle]

In workbench Mechanical and APDL, you can report results in a chosen coordinate system or the global coordinate system, which is how results are reported when no coordinate system in set. In Mechanical, if you set a result to use the solution coordinate system, then yes, this means the element coordinate systems. In APDL, you can issue the RSYS,SOLU command before any postprocessing commands then it will set the element coordinate systems.

https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v251/en/ans_cmd/Hlp_C_RSYS.html

[dlooman]

A line load like N11 will be positive if the stress in that element x direction is positive (tensile.)  It's basically stress times thickness.  If you know a little APDL you can create a one element test to show that.