1. NX nastran SEMODES 103 – Response Simlation
Rene Herrmann
Spektral analysis

2. Starting
Create your 3D model and Start Advanced Simulation SEMODES 103 – Response Simulation

3. Eigenfrequencies
Define 3D mesh and create material properties, density, E modulus and poison ratio. (fem file)
Create constraints - in my case 2 edges are locked (sim file)
Solve (Solution X) right mouse selection SOLVE and find EIGENFREQUENCIES first.

4. NEW SOLUTION PROCESS
Select from sim file NEW SOLUTION PROCESS -> Response Simulation, obtain NEW RESPONSE SIMULATION WINDOW and press OK, after that you have in SIMULATION NAVIGATOR

5. Normal Modes
Select under NORMAL MODES [X] -> EDIT DAMPING FACTOR

6. EVENT
Select under RESPONSE SIMULATION X (right mouse) -> NEW EVENT (OK)

7. Excitations 1
Select under EVENT_X, Excitations -> New Excitation -> Translational Nodal

8. Excitations 2 You will now select a point (node) to study
Once you selected a node you find (Select Node(1)

9. Excitations 3
You select on the right of a coordinate (z) and find a f(x) FUNCTION MANAGER

10. FUNCTION MANAGER
You select the ICON under bottom (NEW) and obtain a XY FUNCTION EDITOR
Select under CREATION STEPS [XY]
Select under XY DATA CREATE the left icon KEY IN FROM TEXT EDITOR (fill in as bellow and press OK ONCE) - frequency is 0 to 2000 Hz and 10 N load

11. Excitation - ready
When you come to NEW TRANSLATIONAL NODAL EXCITATION Window UNCHECK x and y directions – PRESS OK

12. SOLVE
SELECT in SIMULATION NAVIGATOR under EVENT_X, right mouse, EVALUATE FUNCTION RESPONSE, MODAL and get RESPONSE FUNCTIONS

13. SOLVE – what we got
The Eigenfrequencies we calculated first are now damped with 2% viscos damping, the spectrum we see is how a vibration at that resonance moves to other frequencies and decreases in amplitude

14. SOLVE MORE – NODAL RESPONSE
First go back to fem file – to see you model again.
SELECT under EVENT_X, EVALUATION FUNCTION RESPONSE and chose there EVALUATE NODAL FUNCTION RESPONSE.
OBSERVE : RESPONSE REQUEST , DATA COMPONENT [Z] and get

15. NODAL RESPONSE – what we learn
From the nodal response we see how ONE concrete NODE (point) on the model behaves.
You naturally choose a point (node) where you expect either large stresses (clappning positions) or large deflections (long free standing structures)
You see the amplitude of deflection (vibrational amplitude) a a given point and frequency