Hi,
I see you have two mistakes, one in the setup and one in the design of the CAD model.
1) Constraints:
You are doing a static analysis. The model must be statically stable. The constraints need to prevent the model from moving in all six (6) directions: X, Y, and Z translation, and rotation about X, Y, Z. It is clear that you have not prevented rotation about the Y. My guess is other directions are also wrong.
For reasons that are too complex to explain now, the only constraints that have an effect on solid elements are Tx, Ty, and Tz. The Rx, Ry, Rz on the constraint dialog do nothing when applied to a solid. The fastest and easiest thing for you to do is fully fix all 4 legs so that you get results.
A more accurate setup is as follows (see the image below for the location of the 4 legs):
- Fully fix.
- Fix Tx and Ty. The X constraint prevents the model from rotating around the Y axis.
- Fix Ty.
- Fix Ty.
2) Model:
I see the doors are swinging in your results as shown by the yellow arrows in the figure. Swinging is not allowed in a static analysis because it means the doors are statically unstable. A static analysis requires everything to be stable. There are two methods to fix this second issue:
- Add a Tx constraint to one vertex on each door. (Do not apply the Tx constraint to a face or edge. Apply it to a corner of the door; that is, the vertex or point.) This will prevent the doors from swinging.
- Change the CAD model so that the door is imbedded into the cabinet. Change the model from "A" to "B".

One final note. You are not going to see the model tip over. Your second image that says "Not tip-over" is what you are going to see. The model cannot be allowed to tip over because you are doing a static analysis, the model must be statically stable, and tipping is not a static condition. You know it will tip or not tip by viewing the reactions forces.
Good luck!
John
John Holtz, P.E. Global Product Support
Autodesk, Inc. If not provided already, be sure to indicate the version of Inventor Nastran you are using!"The knowledge you seek is at knowledge.autodesk.com" - Confucius ๐