workshop: bicycle frame design modified by (2009): neysa a. fuentes department of mechanical...

Workshop: Bicycle Frame Design

Modified by (2009): Neysa A. FuentesDepartment of Mechanical EngineeringUniversity of Puerto Rico, MayagüezJelisa Torres RamosDepartment of Mechanical EngineeringUniversity of Puerto Rico, MayagüezJose R. VázquezDepartment of Mechanical EngineeringUniversity of Puerto Rico, MayagüezProf Vijay K. Goyal, Ph.D.Associate Professor, Department of Mechanical EngineeringUniversity of Puerto Rico at Mayagüez

Department of Mechanical EngineeringUniversity of Puerto Rico, Mayagüez

http://touringdane.files.wordpress.com/2008/07/bicycle_parts_labeled.jpg

This is a simple static analysis of a frame of bicycle using a hollow aluminum

tube. The schematic dimensions of the bicycle are shown in the figure 1.

Initially, the flowing cross-sectional dimensions are used for all frames: Outer

diameter = 25mm and Thickness φ t =2mm

Problem Description

The material properties of aluminum are:

Material Properties Values

Young’s Modulus (E) 70 Gpa

Poisson’s Ration ( ) ν 0.33

Density ( ) ρ 2,580 kg/m3

Ultimate Tensile Strength( U) σ 210 Mpa

Elongation at Break 10 %

Problem Description (cont.)

Even if the bike is under the dynamic loads, only two static design criteria are considered here, the vertical bending test and the horizontal Impact.

Vertical bending test: When an adult ride the bike, the nominal load can be estimated by the vertically

downward load of 600N at the seat position and a load of 200N at the pedal crank location. When a dynamic environment is simulated using the static analysis, the static loads are often multiplied by a certain “G-factor”. In this design project, use G = 2. Use ball-joint boundary condition for the front dropout ( 1 ) and sliding boundary condition for rear dropouts ( 5 and 6 ).

Horizontal Impact: The BNA’s (Bureau of National Affairs) “Requirements for Bicycles” manual calls

for a single compressive loading test. A load of 980N is applied to the front dropout horizontally with rear dropouts constrained from any translational motion. Use G = 2. For this case the weight of the person (1200N) in the bike will also be considered in addition to the load at the bike pedals (400N) both of these loads have already been multiplied by the G factor.

Starting ANSYS

From your desktop:

Click on: START > All Programs >

ANSYS 11.0 >

ANSYS Product Launcher.

Here we will set our Working Directory and the Graphics Manager

• This is the11.0 ANSYS Product Launchermain window.

• Select the Working Directory and typethe name of work shop on Job Name.

Working Directory Setup

• Click the button:Customization/Preferences.

• On the item of Use custom memory settings type 128 on Total Workspace (MB):and type 64 on Database (MB):

• Then click the Run bottom.

Graphics Setup

* This setup applies to computers running under 512 MB of RAM

• This is ANSYS’s Graphical User Interface window.

ANSYS GUI Overview

We’ll set preferences in order to filter quantities that relate to this discipline only.

Click Preferences from ANSYS Main Menu.

Select (check): “Structural ” & h-Method ”

Step 1: Set Preferences

Define element Types

1) Go to ANSYS Main Menu > Preprocessor > Element type > Add/Edit/Delete

2) In the display window named Element Type Click ADD

In the new display window select pipe and Elast straight 16

3) Then click OK on Library of Element Types and CLOSE on the window of Element Types

Step 2: Element Type

1

2 3

Step 2: Element Type You should have one element type on the Element Types window

Step 3: Real constants • This part is to enter the dimensions of the tube:

• Outer diameter = 25mm and Thickness φ t =2mm Go to ANSYS Main Menu > Real Constants > Add/Edit/Delete > Add > OKIMPORTAT!!! You have to use all the dimension on the same unit since ANSYS is a dimensionless Program. We will use all the dimensions on meters > Add the values

=φ .025 and t =.002 > OK > The window of Real Constants (3) now said SET 1 > CLOSE

1 2

3

Now we are going to define the bicycle frame constant material properties. We are going to

define the material’s behavior and then we’ll define Young’s Modulus (E), poison’s ratio (ν), and

density (ρ).

GO to ANSYS Main Menu > Preprocessor > Material Properties > Material Models

A new window ‘Define Material Model Behavior (1) will appear, on this window make a Double-

click on Structural > Linear > Elastic > Isotropic > a new window will appear (2) > put the

values of Young’s Modulus (E) and poison’s ratio (ν) > OK > CLOSE

To enter the value of density > Double-click on Density (3)> enter the value > OK > CLOSE

Step 4: Define Materials

1

2 3

We’ll start by creating keypoints

– Keypoints: These are points, locations in 3D space.

ANSYS Main Menu > Preprocessor > Modeling > Create > Keypoints

> In active CS

Enter 1 for Keypoint Number, enter 0, 0.325, 0 for X, Y, Z respectively. Click

Apply , @ keypoint #8 click ok instead of apply.

Step 5: Build Geometry

Keypoints X (m)

Y (m)

Z (m)

1 0 0.325 02 0 0.400 -0.0203 0.500 0.400 04 0.400 0 05 .825 0 0.0506 0.825 0 -0.0507 0.400 0 0.0108 0.400 0 -0.010

Make the same for the next seven Keypoints (don’t forget to change the Keypoint Number),

we have a total of eight Keypoints .

After put the values of Keypoint 8, press OK , don’t press APPLY, if you press APPLY, press

CANCEL. Enter 2 for Keypoint Number, enter 0, 0.400, -0.020 for X,Y,Z

respectively. Click Apply

Enter 3 for Keypoint Number, enter 0.500, 0.400, 0 for X,Y,Z


Enter 4 for Keypoint Number, enter 0.400, 0 , 0 for X,Y,Z


Enter 5 for Keypoint Number, enter 0.825, 0, 0.050 for X,Y,Z


Enter 6 for Keypoint Number, enter 0.825, 0, -0.050 for X,Y,Z


Enter 7 for Keypoint Number, enter 0.400, 0, 0.010 for X,Y,Z


Enter 8 for Keypoint Number, enter 0.400, 0, -0.010 for X,Y,Z

respectively. Click OK

Display Window after creating all eight Keypoints

Choosing Isometric view on the right menu


CREATING THE LINES to make the bicycle frame

Now we are going to create lines that will connect the keypoints, we can made this

using two different procedures, using the ANSYS Main Menu or using codes. For

this type of geometry is more appropriate use CODES.

Using Main Menu:

We’ll start by creating straight lines from keypoint 1 to 2.

Main Menu > Preprocessor > Modeling > Create > Lines > Lines

> Straight Lines

– This feature creates a straight line between two points.

For the first Line select keypoints 1 and 2 and for the second line select keypoints

2 and 3 and continue with the other lines. Click Apply and OK


Step 4: Build GeometryUsing Main Menu:

Step 4: Build GeometryUsing the CODES:

In the ANSYS Command Prompt

L,1,2 “Lines, node, node”L,2,3L,3,4L,4,7L,4,8L,7,5L,8,6L,5,6L,1,4L,3,5L,3,6

Geometry after adding the 11 lines (elements)

Glue all the lines together!!!


Here we’ll define the meshing for our bicycle frame.

ANSYS Main Menu > Preprocessor > Meshing > Size control > ManualSize > Lines > All Lines

In SIZE Element edge length 0.020

Click OK

Step 5: Create Mesh

Step 5: Create Mesh

ANSYS Main Menu > Preprocessor > Meshing > Mesh > lines On the window named Mesh Lines Pick All > OK

Save your JOB!!!Utility Menu > File > Save as...

Put the name that you want!

Step 6: Define LoadsHorizontal Impact:

The BNA’s (Bureau of National Affairs) “Requirements for Bicycles” manual calls for a single compressive loading test. A load of 980N is applied to the front dropout horizontally with rear dropouts constrained from any translational motion. Use G = 2. Therefore a load of 1960N is applied to the front dropout horizontally in addition to a load at keypoint 3 of 1200N and a load of 400N to keypoint 4.

Before apply the constrains go to Preprocessor > Loads > Analysis Type > New Analysis > static > OK

Step 6: Define LoadsKeypoint 1

Preprocessor > Loads > Define loads > Apply > Structural > Displacements > On keypoints > Select the keypoints 1 > Select UY, UZ

Keypoint 5 and 6 Preprocessor > Loads > Define loads > Apply > Structural > Displacements > On keypoints > Select the keypoints 5 and 6

Final view after apply the constrains

Select All DOF > OK

Go to Loads > Define Load > Structural > Force/Moment > On Keypoints > select key point 1 > OK

In Lab Direction Of Force/Mon > select FX

In apply as > constant valueIn VALUE Force/moment value > enter the 1960 > OK


In Lab Direction Of Force/Mon > select FY

In apply as > constant valueIn VALUE Force/moment value > enter the -1200 > OK


In Lab Direction Of Force/Mon > select FX

In apply as > constant valueIn VALUE Force/moment value > enter the -400 > OK

Step 6: Apply Loads

1 2 3

Step 6: Apply Loads

Step 7: Obtain SolutionANSYS Main Menu > Solution > Analysis Type >New AnalysisClick on Static (or choose corresponding analysis type), then click ok

Step 7: Obtain SolutionANSYS Main Menu > Solution > Solve >Current LSClick on OK

Step 7.5: Get Happy!

Step 8: Review Results• To see a 3D go to .. PlotCtrls > Style > Size

and shape > [/Eshape] Display element > ON > OK

Step 8: Review ResultsTo see the Deformation General Postproc > Plot Results > Deformed Shape > on the new window > Def + underformed > OK

Step 8: Review Results

Deflections: Nodal SolutionGeneral Postproc > Plot Results > Contour plot > Nodal solutionOn the Display Window > select Nodal Solution > DOF Solution > Displacement vector sum

On Undisplaced shape key > select Deformed shape (or your preference)>OK


Stresses - Von Misses General Postproc > Plot Results> Contour Plot > Nodal Solution On the display window

> Stress> Von Mises Stress > Ok !!


Cross Section For a cross section … Go to menu.. WorkPLane > Display working plane.. An additional 3 axes appears, that is your working plane.Go to… WorkPLane > Offset WP to > by nodes > select the node closest to the cross section that you want > OK

Selected node

Cross Section (1) Then go to… WorkPLane > Offset WP by Increments…And play with the movement of the working plane… It is also useful to rotate in the different axis to get the orientation you want.Remember you want to cut the cross section with the planes X and Y.

(2) PlotCtrls > Style > Hidden line Options..

(3) In the display window in [/TYPE] Type of plot .. Select SECTION > OK

(4) Play with the view until obtain cross section

Cross Section WY Basic idea, use planes WX & WY

to cut a cross section of the desired part in the tube.

WX

WZ

Cross Section

It also helps to use the Dynamic Model Mode rotate the model by right clicking and dragging.

Bending momentSelect General Postproc>Element Table > Define Table... to define the table (remember SMISC,6 and SMISC,12)

ADD > by sequence num > SMISC and put , 6 > apply , put 12 and OK > close

• To see the bending moment plots first go back to PlotCtrls > Style > Hidden line Options

Change in [/TYPE] to Z-bufferedClick OK

Bending moment

And, General Postproc> Plot Results >Contour Plot > Line Elem Res... to plot the data from the Element Table > choose and OK

Bending moment

Bending moment

Optimization

Go to… Design Opt > Analysis File > AssignBrowse for the file used to run the FEM Analysis

workshop: bicycle frame design modified by (2009): neysa a. fuentes department of mechanical...

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