NX nastran SEMODES 103 – Response Simlation

Rene HerrmannSpektral analysis

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

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.

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

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

EVENT

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

Excitations 1

• Select under EVENT_X, Excitations -> New Excitation -> Translational Nodal

Excitations 2

• You will now select a point (node) to study• Once you selected a node you find (Select

Node(1)

Excitations 3

• You select on the right of a coordinate (z) and find a f(x) FUNCTION MANAGER

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

Excitation - ready

• When you come to NEW TRANSLATIONAL NODAL EXCITATION Window UNCHECK x and y directions – PRESS OK

SOLVE• SELECT in SIMULATION NAVIGATOR under EVENT_X, right mouse, EVALUATE FUNCTION

RESPONSE, MODAL and get RESPONSE FUNCTIONS

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

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

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