Fedél mintafeladat – Femap v11Finite Element Analysis
Femap v11
By János DEVECZ
(2018)
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1. Finite Element Analysis Overview
• Create a proper CAD model and prepare the model for FEM
• Discretize the continuum (Meshing) and select Element Types
• Select Interpolation Function (linear, quadratic, etc.)
• Define the Strain/Displacement and Stress/Strain relationships
• Set the Boundary Conditions (Loads & Constraints)
• Solve the Global Equation System Displacements
• Compute Additional Results
FuK Where:
K Stiffness-matrix (constant)u Nodal displacement vectorF External nodal force vector
In case of elastic material behavior the stress can be calculated by applying the Hooke-law.The equivalent stress (regarding the principal stresses and directions) can also be calculated.
FKu 1
Basic Equation of Finite Element Method
General Steps of Finite Element Method
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2. Femap Software Overview
Model informationToolbars
Messages areaEntity editor
Status line
Menubar
Bottom tabsSide tabs
WCS
Work area
WCS: 0,0,0
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2.1 Femap Basic Settings (1)
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2.2 Femap Basic Settings (2)
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2.3 Femap Basic Settings (3)
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THE END
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Shaft FEM Analysis (Bending & Torsion)
By János DEVECZ
(2018)
Femap v11 Example
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Pulley-drive arrangement with (simplified) loads
Tnom
F
D = 212 mm
Ft
Transmitted torque:
Tnom = 160 Nm
Ft
Belt Force:
Ft ≈ 1500 N
Shaft Tension Force:
F ≈ 2Ft = 3000 N
F
Ft
Ft
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Force equilibrium:
belt-force
belt-force
Ft = 2Tnom /D
Tnom
F
F = 3000 N
Tnom = 160∙103 NmmTorque Torsion (moment)
FEM analysis: Large pulley Shaft loads
Tension force Bending
Large pulley shaft
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3D model of Shaft (Solid Edge)
Filename: shaft.par
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Geometry dimensons:
Surface roughness:
Material (Femap):
d = 25 j6 mm | D = 40 mm | l = 42 mm | L = 62 mm | lret = 32mm
Ra,shaft = 1.6 mm | Ra,shoulder = 3.2 mm
AISI Carbon Steel 1025 Cold Drawn
Technical drawing of Shaft (Solid Edge)
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Finite Elements Analysis of Shaft (Femap)
File -> Import ->
Geometry…
{shaft.par}
|OK|
File -> Save
{shaft.modfem}
|OK|
• Import Geometry and Save the FEM model
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Geometry -> Curve –From
Surface -> Parametric
Curve…
Select Surface for
Parametric Curve: (Select
the half cylinder (1))
Method^ : On Point
Select Location for
Parametric Curve: (Select
the point (2))
() V-Direction
|OK| |Cancel|
(Repeat for surface (3) and
point (4), and the back half
cylinder 2x)
•Preparation of Model surfaces: Surface splitting
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(The yellow surfaces on the
pictures show the splitted
surfaces)
•Preparation of Model surfaces: Surface splitting – Result
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•Meshing the Geometric model
Mesh -> Geometry ->
Solids…
Material: AISI Carbon Steel
1025 Cold Drawn
|OK|
Midside Nodes [<NO>]
|Update Mesh Sizing…|
Element Size: [3]
(Size in mm)
|OK|
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•Defining the Constraints
Model -> Constraint ->
Set…
ID [1] Title: [fixation]
|Done|
Model -> Constraint -> On
Surface…
(Select the yellow surface on
the picture)
Title: [fixed]
Standard Type: () Fixed
|OK|
|Cancel|
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•Defining the Loads – Bending
Model -> Load -> Set…
ID [1] Title: [loads]
|Done|
Model -> Load -> On
Surface…
Entity Selection: (Select the
yellow surface on the picture)
|OK|
Title: [bending]
Force
Direction:
() Components
FX [3000], FY [0], FZ [0]
(Force Components in N)
(Listen to the sign of Force!)
|OK| |Cancel|
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•Defining the Loads – Torsion
Model -> Load -> On
Surface…
Entity Selection: (Select the
yellow surface on the picture)
|OK|
Title: [torsion]
Torque
Direction:
() Magnitude only
Magnitude [160000]
(Torquee Magnitude in Nmm)
(Listen to the sign of Torque!)
|OK|
Base: X [0] Y [0] Z [0]
Tip: X [0] Y [1] Z [0]
|OK|
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Model -> Analysis…
|New…|
Title: [bending and torsion]
Alalysis Prog.: 36..NX
Nastran
Alalysis Type: 1..Static
|OK|
|Analyze…|
|Done…|
•Setting the analysis parameters and start analysis
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•Show results – Deformation and Von Mises Stress
View -> Select…
Deformed Style:
() Deform
Contour Style:
() Contour
|Def. and Contour Data…|
Output Sets:
[1..NX NASTRAN Case 1]
Output Vectors:
Deform:
[1..Total Translation]
Contour:
[60031..Solid Von Mises
Stress]
|OK| |OK|
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THE END
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Fedél mintafeladat – Femap v11Tube Cap Finite Elements Analysis
Femap v11 Example
By János DEVECZ
(2018)
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1.1 Example – Tube Cap
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1.2 Example Overview – Assembled Parts (Cut View)
Cap
Bolt
Washer
Hex Nut
Gasket
Tube-flange
Internal
Pressure
Loads
• bolt pretension and pressure
Constraints
• friction and interference fit| 3
1.3 Tube Cap Overview – Applied Loads & Constraints
p = 10 MPa (3 x)
(internal pressure)
Fe = 20 kN (4 x)
(bolt pretension)
Friction area (4 x)
(fixed in all directions)
Flange (transitional fit)
(constraint only radially)
Equivalent cylinder
(pressure volume)
Loads
• bolt pretension and pressure
Constraints
• friction and interference fit | 4
2.1 Import Geometry
The choice depends on the
Units, set in CAD software!
(Unit in CAD & FEM = mm)
Cap.par
Cap.par
File name: Cap.par
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2.2 Views – Geometry (model)
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3.1 Geometry Preparation – Define Washer
Washer (circular area around a hole)
• effect surface of bolt pretension
• effect surface of friction
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3.2 Geometry Preparation – Define Washer (top)
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3.3 Geometry Preparation – Finished Washer (top)
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3.4 Geometry Preparation – Define Washer (bottom)
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3.5 Geometry Preparation – Finished Washer (bottom)
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3.6 Geometry Preparation – Exit Washer Command
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4.1 Meshing – TetMesh
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4.2 Meshing – Open Material Database
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4.3 Meshing – Select Material (X-40 Cast)
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4.4 Meshing – Material Confirmation
[MPa]
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4.5 Meshing – Set Avgerage Element Size
Avg. element size
No Midside Nodes necessary
[mm]
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4.6 Meshing – Finished Mesh
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5.1 Loads – Create New Dataset (1)
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5.2 Loads – Create New Dataset (2)
Loads
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5.3 Loads – Create New Dataset (3)
1..Loads
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5.4 Loads – Applying (On Surface)
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5.5 Loads – Select Washer Surfaces (top)
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5.6 Loads – Set Force value – Bolt (Z)
Bolt (Z)
[N]
[4 x]
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5.7 Loads – Select Dome Surfaces (inner)
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5.8 Loads – Set Prerssure value – Pressure (p)
Pressure (p)
[MPa]
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6.1 Constraints – Create New Dataset (1)
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6.2 Constraints – Create New Dataset (2)
Constraints
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6.3 Constraints – Create New Dataset (3)
1..Constraints
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6.4 Constraints – Applying (On Surface)
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6.5 Constraints – Select Washer Surfaces (bottom)
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6.6 Constraints – Set Constraint values – Bolt (FIX)
Bolt (FIX)
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6.7 Constraints – Select Flange Surfaces (two half)
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6.8 Constraints – Set Constraint values – Flange (RAD)
Flange (RAD)
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7.1 Define Analysis Type
<optional name>
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7.2 Run Analysis
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8.1 Results – Select Deformed and Contour Data
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8.2 Results – Set Contour Options
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8.3 Results – Show Stresses (von Mises)
[MPa]
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8.4 Results – Define Cutting Plane (1)
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8.5 Results – Define Cutting Plane (2)
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8.6 Results – Select Cutting Plane
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8.7 Results – Set Contour Options
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8.8 Results – Show Stresses (von Mises) (Cut)
[MPa]
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9.1 Global Remeshing – Delete Old Mesh (1)
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9.2 Global Remeshing – Delete Old Mesh (2)
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9.3 Global Remeshing – Define New Mesh – TetMesh
Geometry (model) Show/Hide
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9.4 Global Remeshing – New Average Element Size
New Avg. Element Size
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10.1 Local Remeshing – Meshing Toolbox
According to Curve(s)
Increase Nodes
Multply by Factor
Number of Elements
Equal Spacing
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10.2 Local Remeshing – Using Curves
Select Curve(s) to Remeshing
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10.3 Local Remeshing – Remeshed Regions
No. of Nodes, No. of Elements
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11.1 ReAnalysed – Show Stresses (Von Mises)
Analyse[MPa]
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11.2 Nodal Stress (Von Mises) inquiry (1)
[MPa]
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11.3 Nodal Stress (Von Mises) inquiry (2)
Examined
Node
[MPa]
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12.1 Convergence Curve – Overview
Steps to Convergence Curve:
1. Designate an examined point (preferably geometric point)
2. Meshing + Analyze Note the number of Elements (E) and
Stress () at the test point (Node)
3. Refine mesh + Analyze (with unchanged boundary conditions)
Note the number of Elements (E) and Stress () at the test point
(Node)
4. Repeat the step 3 as often as necessary
5. Plot the corresponding number of Elements and Stress pairs in
the E- coordinate system
6. Fit the convergence curve to the points
7. The asymptote of the fitted curve will be the accepted Stress | 55
No. of Elements (E)
Von Mises
Stress
[MPa]
Mesh4; E=15312 Mesh5; E=21983Mesh3; E=11734Mesh2; E=8664Mesh1; E=6715
xceba)x(f
a = 77.567249
b = 599.61779
c = 0.00049989295
Convergence-curve
red,1=56.5 MPa
red,2=70.3 MPa
red,5=78.7 MPa
red,3=75.1 MPa
~78 MPa
1
2
3
4
5
1
2
34
5
red,4=76.4 MPa
12.2 Convergence Curve – Plot
Examined Node
Accepted range
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THE END
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Connecting rod Buckling Analysis
Femap v11 Example
By János DEVECZ
(2018)
Air compressor – Connecting rod (3D View)
Connecting rod
Air compressor – Conecting rod (Cross Section View)
Connecting rod
Connecting rod (3D model)
Pcr
The buckling (Experiment)The buckling is an instability, leading to a failure. It is a sudden failure of a part subjected tohigh compressive stress, where the actual compressive stress at the point of failure is less thanthe ultimate compressive stresses that the material is capable of withstanding.
Pcr Pcr Pcr
The buckling (Theory)
Pcr Pcr Pcr Pcr Pcr Pcr
Connecting rod (Material, Load and Constraints)
F = 20000 N
Constraints:
TX, TY, RX, RZ
Required safety factor
against buckling:
SFreq = 6 ~ 10
Deformed shape
(mechanical model)
Undeformed shape
(mechanical model)
Constraint:
Pinned –
No Translation
Material: 70 Ni (with Chromium) Wrought
Constraints:
TX, TY, RX, RZ
Constraint:
Pinned –
No Translation
THE END
Crankshaft Modal Analysis
Femap v11 Example
By János DEVECZ
(2017)
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The resonance is a tendency of a system to oscillate with greater amplitude at some frequencies than at others.Frequencies at which the response amplitude is a relative maximum are known as the system's resonant frequencies orresonance frequencies. At these frequencies, even small periodic driving forces can produce large amplitude oscillations,because the system stores vibrational energy.
Resonance (theory)
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Crankshaft Torsional Vibration
Torsional vibration is a concern in the crankshafts of internal combustion enginesbecause it could break the crankshaft itself; shear-off the flywheel; or causedriven belts, gears and attached components to fail, especially when thefrequency of the vibration matches the torsional resonant frequency of thecrankshaft. Causes of the torsional vibration are attributed to several factors.
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Air compressor - Crankshaft
Crankshaft | 4
Crankshaft (modal analysis)
bearing
bearing
Fy = 20000 N
Constraint:
Radial Growth
Fy (force)
X
Y
Z
Resonance Frequencies [Hz] Critical Rotational Speeds [1/min]
Critical Frequency Range = 10...15 % of Resonance Frequency
Constraint:
Radial Growth
Constraint:
No Rotation mechanical model
of crankshaft
(undeformrd)
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THE END
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