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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