D3_Buckling Analysis (Designer)

Buckling Analysis

Buckling Analysis 2

Step

00 Buckling Analysis

Overview of Buckling Analysis

Buckling analysis evaluates the instability of a structure subjected to compression loads.

The instability of the structure due to buckling is not dependent on the strengths of materials. Rather it is closely related to the

geometric shape, stiffness and boundary conditions of the structure.

When an axial compressive force is acting at the end of a long and slender structure, only the axial deformation proportional to the

magnitude of the load takes place. However, if the magnitude exceeds its critical point, the structure undergoes large deformation

without further increasing the load.

Buckling of cylinderical columns F

F

F F

A. Identical cross-section

subjected to the same

load, but with different

lengths

Deformed

Large

deformation

(buckling)

occurs

• For A, since the cross-sectional areas of the two cylindrical columns

are the same, the stresses are the same, defined by σ=F/A. However, a

large deflection (buckling) may occur if the length increases.

• For B, since the lengths are the same while their cross-sectional areas

are different, buckling will likely occur in the column of smaller

diameter, which is subjected to a larger stress. That is, a column with a

smaller cross-sectional area and longer length is more prone to

buckling.

B. Identical length

subjected to the same

load, but with different

cross-sections

Large

deformation

(buckling)

occurs

Deformed

Buckling Analysis 3

Step

00 Loads / Boundary Conditions

Overview of Buckling Analysis

• Loadings are applied in the same way as linear static analysis.

• Boundary conditions are defined in buckling analysis also identically to static analysis.

• Buckling is significantly affected by boundary conditions, which need to reflect true constraints.

Pinned-pinned Top free,

Bottom fixed Fixed-fixed

Top pinned,

Bottom fixed

Rectangular Pipe 4

Step

Rectangular Pipe

Summary

Summary 00 Buckling Analysis

- Unit: N, mm

- Geometric Model: Buckling.x_t

Loads and Boundary Conditions

- Fixed

- Force (160KN)

Results Verification

- Displacements

- Eigenvalues

- Mode Shapes

- Comparison with Theory

Rectangular Pipe 5

Step

00 Analysis Summary

Linear Buckling Analysis Types

Analysis Summary

Target Model Boundary Condition (Fixed) Finite Element model (Tetra Mesher)

Linear Buckling Analysis Objectives of Tutorial

Linear Static Analysis

Eigenvalues Analysis

Geom. Stiffness Calc.

Eigenvalues Calc.

(λ Calc.) 0 SI KK

Buckling Load Calc.

acr PP

Structural Stability

Verification

Apply concentrated load

at the top plane: -160 KN

Assign fixed boundary

condition at the other end

plane

Load Condition

(Conc. Load)

Understanding the basics of

linear buckling analysis and the

process of analysis

- A structure subjected to a large axial

pressure load

- A slender column under axial loads

- A thin cylindrical structure subjected to

external pressure around the edge

- A long and slender cantilever subjected to a

lateral pressure load acting at the tip

Rectangular Pipe 6

Step

00 Analysis Summary

Calculation of the critical load

3/850.7

33.0

70

160

3000:)(Length

10:)( Thickness

150150:Section Cross

mkg

GMaE

KNP

mmL

mmt

mmmm

2

2

4 L

IEnPcr

KNP 86.35234

))13.013.0()15.015.0((12

110701

2

3392

1

KNP 8.317534

))13.013.0()15.015.0((12

110703

2

3392

3

KNP 882134

))13.013.0()15.015.0((12

110705

2

3392

5

Rectangular Pipe 7

Step

Procedure

Model & LBC > Geometry > Import

4

3

01 Click [ ] (New).

Click [Geometry] - [Import].

Model: Select Buckling.x_t.

Click [Open].

Note: Tutorial models are included

in the folder, Manuals / Tutorials /

Files, in the installed program

folder.

1

2

3

4

Click [New] to activate all menus.

Check File type and Length Unit

1

2

Rectangular Pipe 8

Step

Procedure

Model & LBC > Geometry > Material 02 Click [Geometry] - [Material].

ID: “2” , Name: Enter “User Define”.

Elastic Modulus: Enter “70000”.

Poisson’s Ratio: Enter “0.33”.

Mass Density: Enter“7.85e-9”.

Click [OK].

1

2

4

3

1

2 2

3

4

Rectangular Pipe 9

Step

Procedure

Model & LBC > Geometry > Material (Material assignment-User Define) 03 After selection of the model in the

work window, right-click

Geometry.

Select [Material] > [User Define].

1

2

1

2

Right-click each part under Geometry

to assign them various materials.

To assign the same material on all the

parts, simply right-click Geometry and

select the material.

Rectangular Pipe 10

Step

Procedure

Model & LBC > Boundary > Support 04 Click [Boundary] - [Support].

Name: Enter Fix.

Target: Select 1 Plane (Refer to

Picture).

Condition: Enter Fixed.

Click [OK].

1

2

3

4

3

3

5

2

4

5

1

Rectangular Pipe 11

Step

Procedure

Model & LBC > Static Load > Force 05 Click [Static Load] – [Force].

Select Isometric2.

Name: Enter “Force”.

Target: Select 1 Plane. (Refer to

Picture)

Load Type: Select Total Force.

Y Direction Load: Enter “-160000”.

Click [OK].

1

2

3

6

4

3

7

3

5

6

7

2

4

5

1

Rectangular Pipe 12

Step

Procedure

Model & LBC > Mesh > Auto Mesh 06 Click [Mesh] - [Auto Mesh].

Select all the models as target.

Select High Speed Tetra Mesher.

Click [Option <<] button.

Verify that High-Order Element is

checked.

Click [OK].

1

2

3

2

3

6

Click [ ] (Select All) Icon to select

the total model displayed on the work

window.

4

4

5

6

5

1

2

Rectangular Pipe 13

Step

Procedure

Analysis & Results > Analysis Case > General 07 Click [Analysis Case] - [General].

Name: Enter “Buckling”.

Analysis Type: Select [Buckling].

Click [OK].

1

2

3

2

3

1

Rectangular Pipe 14

Step

Procedure

Analysis & Results > Analysis > Perform 08 Click [Analysis] - [Perform].

Click [OK].

Save As: Enter “Buckling”.

Click [Save(S)].

1

2

3

4

Once midas NFX is executed, the

solver becomes engaged. Click “Stop

Execution!” to interrupt the calculation.

1

2

3

4

Rectangular Pipe 15

Step

Procedure

Analysis & Results Works Tree > Buckling > Mode Analysis > MODE 1 09 Click [ ] (Top) Icon.

Select Deform>Deformed +

Undeformed (Transparent).

Select Auto Scale (*2).

In the Analysis & Results Works

Tree, Double-click MODE 1,

TOTAL DISPLACEMENT (V).

1

2 1

4

2 3

3

4

None (O)

Rectangular Pipe 16

Step

Procedure

Analysis & Results Works Tree > Buckling > Mode Analysis > MODE 3 10

4

Click [ ] (Top) Icon.







1

2

3

4

1 2

3

None (O)

Rectangular Pipe 17

Step

Procedure

Analysis & Results Works Tree > Buckling > Mode Analysis > MODE 5 11 Click [ ] (Top) Icon.







1

2

3

4

1 2

3

None (O)

Rectangular Pipe 18

Step

00 Analysis Summary

Comparison with Theory

2

2

4 L

IEnPcr

KNP 86.35234

))13.013.0()15.015.0((12

110701

2

3392

1

KNP 8.317534

))13.013.0()15.015.0((12

110703

2

3392

3

KNP 882134

))13.013.0()15.015.0((12

110705

2

3392

5

12

KNKN

n

KNKN

n

KNKN

n

904.80110744.50160

5

36.3075221.19160

3

875.3522055.2160

1

MODE 1

MODE 3

MODE 5

MODE 1

MODE 3

MODE 5

D3_Buckling Analysis (Designer)

Documents

Transcript of D3_Buckling Analysis (Designer)