Answer:
Since only the directions x- and y- exist in the plane for surfaces, you must first determine which is to be the hoop stress and which the axial stress. In the following example, sigma_x should be the axial stress and sigma_y the hoop stress.
The example consists of an inclined circular container (Image 01). After the modeling, the program tries to align the local axis systems on the global axis system (Image 02). However, the x‑axis should run along the container for all surfaces in this case. This orientation can be achieved as follows.
First, the z‑axis of all surfaces must point inwards or outwards. In the example, the outside direction has been selected. If this is not the case for the surface, you can right-click the surface and use the "Reverse Local Axis System" feature to move the z‑axis to the other surface side. Then, select all surfaces and open the Axes tab in the Edit Surface dialog box. Image 03 shows the dialog box. In this case, one of the boundary lines oriented axially has been selected. Image 04 shows the aligned local axis systems now. All x-axes are axial and all y-axes run in the circumferential (hoop) direction.
Image 05 shows the results of the membrane stresses axial (sigma‑x,m) and along the circumference (sigma‑y,m).
