Hi Ash,
I think that you should attach your model (or models) to a reply so that someone can look at them. Use "File > Export" to create an Archive File (.f3d). If that does not work because of the type of model, then you can follow the instructions in this article to create an archive of a model with references: How to make a local archive (back-up) file in Fusion 360
Otherwise, here are answers to your questions.
1) Modal Analysis
Are the results exactly the same or almost the same? Compare the first mode for each model (because that is where the largest difference will be seen).
- If the results are exactly the same, it may be that the load that you are applying does not change the frequency! A frequency change is created when parts are in tension or compression. A part in bending does not experience a frequency change.
- If the results are almost the same, then the load is not large enough to create a significant change in the frequency.
- Note that you may need to look at the calculated frequencies in the Solver Output text to see enough precision to know whether the calculated frequencies are exactly the same or almost the same.
Here are the types of things that need to be provided in order to understand why the results "do not change".
- What does the model look like?
- What are the results?
- How much stress is created by the 300 N load?
- Is the load creating mostly bending, compression, or tension?
2) Buckling Analysis
You have not provided any information about what the "failure" is, so it is not possible to provide any suggestions on what should be changed.
- Is there an error message?
- How many warnings are in the solver output? ("Results > Solver Data > Solver Output").
- What does the model look like? What are the load and constraints?
Again, the best solution for this is to provide the model.
John Holtz, P.E. Global Product Support
Autodesk, Inc. If not provided, indicate the version of Inventor Nastran you are using.If the issue is related to a model, attach the model! See What files to provide when the model is needed.