When you model a beam in SOLIDWORKS, you can set up the cross section to align with the default coordinate system. The contrived beam shown below was modeled with the bottom face parallel to the x axis:
If a simulation study is created and the beam is modeled using beam elements, SOLIDWORKS Simulation will automatically create a local coordinate system for the beam based on its cross section. The forces and stresses will be reported relative to this coordinate system. We can view this coordinate system by right-clicking on the component in the Feature Tree and selecting “Edit Definition”. This will bring up the “Apply/Edit Beam” Property Manager which contains a checkbox to “Show beam direction”.
As we can see, the red axis is along the axial direction of the beam, but the green (direction 1) and blue (direction 2) axes are not aligned with the x and y axes of our model. This is because SOLIDWORKS defines direction 1 to be parallel to the longest edge of the cross section. In our model, this is the sloped side section. This will affect reported values of moment of inertia compared to section properties obtained in the model. To rectify this, we can utilize a simple modeling trick to make the bottom edge the longest edge. If we sketch lines on the four sloped faces (interior and exterior) and use the Split Line command, we can effectively shorten the edge length without affecting the model geometry.
We can now go back to the study and, after right-clicking on the study name to “Update All Components”, we can edit the definition of the beam to see that the beam direction has updated.