my metallic design capability maintenance studies update 9th october 2016

Mr. Geoffrey Allen Wardle MSc. MSc Capability Maintenance Examples 2012-2013.

1

MY METALLIC DESIGN CAPABILITY MAINTENANCE STUDIES.

By Mr. Geoffrey Allen Wardle MSc. MSc. Snr MAIAA 2012 to Date.


This is presentation gives examples of metallic airframe design work I have undertaken on my own

initiative to maintain my capabilities with the Catia V5.R20 toolset in addition to Workbooks 1 and 2,

and my current AIAA design study. The descriptive work contained herein is based Cranfield

University MSc and University of Portsmouth MSc academic studies Cranfield Aerospace design

standards, my FATA technology research project INCAT training, EASA CS 25-571 and referenced

texts.

2

MY METALLIC DESIGN CAPABILITY MAINTENANCE STUDIES.

WING_10012_MET_RIB_12_BASELINE_1000-0001B

Al/Li Rib 12 from FATA Design Project.


Section 1:- Design Guides For Machined Parts:

Section 2:- My CATIA V5.R20 Design Capability Machined Part Examples (Methodology: FDT:

and 2D drawing development).

Section 3:- My CATIA V5.R20 Design Examples of Sheet Metal Parts (Methodology and 2D

drawing development).

Section 4:- My CATIA V5.R20 Assembly Design Examples (Methodology).

Section 5:- My CATIA V5.R20 GSA Design Examples (Methodology and SAFESA methods of

error control).

Section 6:- Advanced Metallic Technology Additive Manufacturing Technology.

Section 7:- High Speed Machining Studies of Research for Al alloys.

Section 8:- Operation oriented Machining Using the Catia V5.R20 Workbench based on

previous Unigraphics V.14 NC simulation work. (In Work). I plan a separate presentation of

Catia V5.R20 Operation - oriented Machining using the NC Workbench for FATA Wing Project

Rib 30 using lessons learnt from these studies and now intend to publish it on LinkedIn at the

end of Sept 2016. 3

Machined metal, Sheet metal, Assembly design, and Analysis, presentation contents.


The metallic structural components designed for AIAA design project by myself include the wing ribs

which are to be produced as double sided machining's from Aluminium Lithium alloy by 5 axis high

speed machining the machining methods, standards, and design practices (parts shown are

designed by myself), which are applied in all machined component design undertaken to date. The

following sections contain my examples of machined part design, sheet metal design, and metallic

assembly, and FEA worked examples for proficiency practice more examples will be added.

The one of the most effective weight reduction features for the all metallic aircraft wings has been

the adoption of large scale five axis high speed machining of many structural components

previously made by the sheet metal fabrication route, and the use of ruled surfaces, and minimum

fillet radii, and if essential scalloping. This includes integrally machined wing cover skin stringers,

machined spars (with web crack stoppers), and ribs, thus enabling a reduction in fastener weight,

less scope for fatigue cracking propagating from fastener holes, reduced parts count and assembly

costs. Also joining high speed machined components can be achieved with bath tub joints or

integral end tabs without the need for separate cleats and additional fasteners. Other weight

savings have been gained from the application of titanium alloy in place of steels for highly loaded

or high temperature components produced as near net shape forgings, or even in the case of

Super Plastically Formed titanium alloy structures employed as lower wing access port panel

covers, replacing the formally sheet fabricated covers. Titanium is also more compatible than

aluminum when used with composites in that it is not susceptible to galvanic corrosion and has a

compatible coefficient of thermal expansion. Also the adoption of Aluminium Lithium alloys in such

applications as wing ribs with a density saving of 5% over conventional aluminium alloy structures.

4

Design of Machined and sheet metallic components for the design studies.


1 piece machining

5 piece welded assembly

5

Machining verses Fabrication

Consideration should be given to integrating smaller details into 1 piece machining to reduce

weight parts count and assembly operations as shown below.

Benefits of machining detail :- Only 1 item required to manufacture, hence inventory

reduced: No sub-assembly / welding time: Weight reduction: Better quality: Better

accuracy.


6

SECTION 1:- DESIGN GUIDES FOR MACHINED PARTS.

X+

Z+

Y+

A

B

X+

Z+

Y+

A

B

Project Metallic wing ribs / posts

/ splices and other components.

Test Box assembly.

5 Axis Machining.

See references (1) , (2), (3) and (4) for all material in this section.


Figure 1(a) Example of 3 axis machining:-

3 Axis Machining:-

During machining the cutter can move simultaneously

along the X,Y & Z axes. The tool axis orientation is fixed

during machining. Usually used for simple geometries

where missed material is not a major issue.

(This example shows the spiral milling of a shallow

pocket feature on a compound surface).

Figure 1(b) Example of 5 axis machining:

5 Axis Machining:-

During machining the cutter can move along the X, Y &

Z axes and rotate around e.g. the X & Y axes

(designated A & B axes motion) during the machining

cycle. This capability enables the Fanning and Tilting of

the tool during machining for complex deep pockets

where excess material is an issue.

Fig 1 (a/b):- Machining Methods for Metallics applied in the design studies.

X+

Z+

Y+

A

B

Figure 1(b)

X+

Z+

Y+

Figure 1(a)

7


Design for Manufacture:-

To machine an External Flange surface produced as a

result of splitting the model with a complex surface is both

time consuming and costly.

Therefore to aid manufacturing, the complex surface can

be replaced by a ruled surface provided the Chord Height

Error (CHE) is within the values specified in Design

Standards. (see Figure 2)

Where the CHE value exceeds the specified maximum, the

flange is produced by splitting the model with a faceted

surface. (see Figure 3).

A bespoke Flange application will be available in the near

future to automate the creation of the Faceted Ruled

Surface. As this was not available at the time of writing, the

exercise accompanying the course requires manual

generation of this geometry

External Flanges produced by complex surfaces are

permissible, but should only be used in extreme cases and

in agreement with manufacturing due excessive machining

costs

Fig 2 /3:- Machined Metallics:- Chord Height Error applied for design studies.

Figure 2 Figure 3

CHE

Preferred Non-Preferred

8


Design for Manufacture:-

In Figure 4 the area shaded in Black indicates the 5

Axis Landing, and is the remaining material following

machining of the internal face of the closed angle

flange, and represents the difference between the as

designed and as manufactured part.

In such cases, it is a mandatory requirement for

allowances to be made for the loss of fastener seating

area.

The remaining material can be further reduced by

additional machining.

The area shown in Black in Figure 5 represents the

preferred condition of 5 axis landings following

machining.

Figure 4

Figure 5 Preferred

Fig 4/5:- Machined Metallics :- 5 axis landings applied in the design studies.

9


Figure 6:-Fillet and Corner Radius.

Fillets used in the design studies.

Standard fillet radius : 4.0 mm

Non-Standard : 2.5 mm, 0.5 mm, 6.0 mm, 8.0 mm & 12.5 mm

Imperial Size : 3.0 mm (1/8) used on US projects.

Fillets less than 3.0 mm must be evaluated by stress and fatigue

analysis

Fillet Corner Radius

Cutter Radius

Cutter Fillet

10

Corner Radius

Standard corner radius are produced : cutter radius + 0.5mm

(minimum)

Standard Cutters Generated Radius(mm) Generated Radius(inch)

9.00

12.0

16.0

20.0

25.0

32.0

50.0

5.00

6.50

8.50

10.5

13.0

16.5

25.5

0.21

0.27

0.33

0.41

0.52

0.65

1.00


Corner radius

Flange height

11

Figure 7:-Flange Height and Corner Radius Ratio.

Corner Radius Cutter Dia Flange Height (4xd)

5.0 9.0 36.0

6.5 12.0 48.0

8.5 16.0 64.0

10.5 20.0 80.0

13.0 25.0 100.0

16.5 32.0 138.0

Avoid using long cutters by working to a maximum 4 x cutter diameter:

Any flange height more than 4xd must be discussed with Machining rep:

Long cutters cause, bad finish, reduce tool life, increased cost and manufacture (slower, speeds,

feeds and smaller depth of cuts).


12

Figure 8:- Split Corner Radius maintains flange height /corner radius ratio.

Smaller corner radius to maintain standard flange height & corner radius ratio

A split corner radius can be used to fulfil tighter fastener spacing & maintain flange height

and corner radius ratio

A minimum of 1.5 mm clearance from fastener to corner radius is required


13

Figure 9:- Flange & Stiffener thickness / height ratio.

Thickness

Flange

Height

Free standing

flange 1:10

Supported

flange / stiffener

1:25 Aluminium

1:20 Titanium

Aluminium 1:25 (Supported) Steel / Titanium 1:20 (Supported)

Thickness Flange Height Thickness Flange Height

1.0 25.0 1.0 20

1.5 37.5 1.5 30

2.0 50.0 2.0 40

2.5 62.5 2.5 50

3.0 75.0 3.0 60

Minimum flange / stiffener thickness are constantly being challenged by design to reduce weight.

Minimum thickness on Aluminium : 1.0 mm up to flange / stiffener height of 25 mm (Supported)

Minimum thickness on Titanium & Steel : 1.5 mm up to flange / stiffener height of 20 mm (Supported)

Avoid free standing flanges due to buckling as the ratio goes to 1:10 (Stress raiser).


14

Minimum web thickness are constantly being challenged by design to reduce weight.

Improved cutter technology and new manufacturing methods will all contribute to reduce web thickness.

It is difficult to identify generic sizes but current guidelines are listed below ;

Figure 10:- Web Thickness (Bases).

Aluminium Steel / Titanium

Supported bases up to 250 mm x 250 mm envelope 1.0 mm 1.2 mm

Unsupported bases up to 150 mm x 150 mm envelope 1.2 mm 1.5 mm

Unsupported bases up to 250 mm x 250 mm envelope 1.5 mm 2.0 mm

Tooling lug Tooling lug

Supported

Unsupported


15

Figure 11:- Chamfers / Hand finishing and Part marking.

Chamfers

Chamfers to be standard angles where possible (3-axis parts) 30, 45, 60, 75 are common sizes: Dimensions

parallel to the machine datum and not from OML face: Chamfer form is easier to produce than radius form

including multiple chamfers.

Datum Plane Radius form non-preferred Multiple Chamfer

OML

Hand Finishing

Minimise hand finishing requirements, details should have all sharp edges removed ONLY: Blend out scanned

peak heights, cutter mismatches and dwell conditions only if stated: Stress / Fatigue strongly reject hand

finishing due to fatigue life: NB Excessive hand finishing increases the product cost, lead time manufacture and

risk of scrap.

Part Marking

Part marking position & type to be identified on drawing: Part marking to be viewable once details are

assembled: Class 1 parts to be permanently part marked in accordance with specification ( minimum envelope

size 20 x 40): Class 2 & 3 parts to be part marked to a minimum envelope of 20 x 40, all other parts are bag &

label.


16

Details parts that are made out of extruded plate, extrusions, and forgings have Grain Direction

identified see figure 12:

Grain direction is determined by the structures group & shown on 2d drawing:

If removal of Dead Zones is critical, then a note on the drawing is required:

If grain direction is not critical then a note is required on the 2d drawing : Grain direction

immaterial or Grain direction control not required for structural purposes.

Max Material sizes : Material ThicknessLength Width

Aluminium 160 mm 4000 mm 1250 mm

(Thickness in 5mm increments)

Titanium 100 mm 4000 mm 1250 mm

(Thickness in 5mm increments)

Any components outside these sizes would require a forged billet or forging

Material has different thickness bands which are defined as Ruling Section or Ruling

Dimension.

Each band has different properties, Structures group will determine the Maximum Ruling

Dimension for each detail.

Grain Direction.


17

Figure 12:- Grain direction definition.

ST

LT

L

L

LT

LT

ST

ST

ST

Parting Plane

ST Across parting plane.

Figure 12(a) Plate, Strip, and Sheet. Figure 12(b) Extrusion.

Figure 12(c) Forging. Figure 12(d) Grain direction on 2-D drawing.


18

Figure 13:- Scalloping on Flange top profiles.

Tooling lug Cutter Dia

4 rad

5 mm rad minimum

4 mm flat on flange top

Scallop depth = 1 x

fastener diameter

10 mm flat for 16 Dia Cutter



Scalloping should be avoided at all times, but if scalloping is required, the above manufacturing

options should be used to assist tooling lugs & preferred cutters.

The use of ball end cutters should be avoided, due to bad finish & increase in machining time.


19

Avoid steps in webs

Keep webs simple to avoid tooling & reduce

machining run time

Figure 14:- Steps in webs and two sided machining features.

0.25mm min

Step condition

Machine pockets stage 1

Machine aperture stage 2

When designing details that require

machining from 2 stages avoid

mismatch / false cut features by

designing a step.

Figure 14(a) Web Steps should be avoided.

Figure 14(b) Web Steps conditions for 2 stage cutting process.


20

Flange & Stiffener Tops Up to10 deg

Produce flange top parallel to

web up to 10 deg

Over 10 deg

Produce flange top normal to flange over 10 deg to

avoid sharp edge

Avoid sharp edge

Figure 15:- Designing out stress raisers in flanges and stiffeners.

Sharp edge Modify Stiffener end to make normal

Stiffener end

Plan view

Plan view


21

Figure 16:- Designing out stress raisers in flange thickness changes.

Non-preferred

1.8 mm 6.0 mm

1:3.3 ratio

Preferred

1.8 mm 2.5 mm 3.8 mm 6.0 mm

Flange & web thickness should be no greater than 1:3


22

T Max 0.3 T Min 2.0 rad

Counterbores

T

0.3 T min

Countersink

The depth of counterbores should be no greater

than 0.3 times the thickness of the material. Countersink should be no more than

70% Holes to be 1.5 mm away from fillet.

Fastener hole to flange edge to be 2 x dia + 1mm

Figure 17:- Stress Raisers:- fasteners and thickness / fillet radius ratios.

Thickness & fillet radii ratios.

t r

h

Radius r : The lesser of

r = 0.5 t

r = 2 h

t 1 r

h


r = t 1

r = 2 h

t 1 r

t 2


r = t 1

r = t 2

t 2

t 1


r = t 1

r = 0.5 t 2

r


r = 0.5 t 1

r = 0.5 t 2

t 2

t 1

r

Note : where the rule results in a radius of less than 4.0 mm then 4.0 mm will be used.


2

3

Figure 18:- Designing to avoid KTs stress raisers in of machined parts.

KT 1.5 mm min

separation

Corner

rad

Flange

rad

Corner

rad

Flange

rad

Corner rad & Flange rad Non-Preferred Preferred

5-Axis Landing

Fillet Fillet

Corner

rad Corner

rad

KT 1.5 mm min

separation Non-Preferred Preferred

KT

1.5 mm min

separation

External

rad

External

rad

Fillet

Fillet

External rad & Fillet

Non-Preferred Preferred

Stiffener rad & Flange rad

Stiffener

rad

Stiffener

rad

KT

Flange

rad

1.5 mm min

separation

Flange

rad Non-Preferred Preferred


24

Figure 19:- Web scalloping stress raisers in an acoustic fatigue area.

Figure 19(a):- Shows the result of a acoustic fatigue on a test box

aluminium spar with scalloped web stiffeners.

Crack failure

at fillet / radii.

Figure 19(b).

Make flange top flat.

Figure 19(c).

Figures 19(b) and 19(c) Scalloping of stiffeners should be

avoided as the cracks start at fillets/radii, so where possible

keep stiffener tops flat.


25

Surface

Drill H8 Drill

H11 Ream H7

Blind hole

Hole normal to

surface

Depth of countersink

Figure 20:- Hole design for manufacture standards.

Standard hole sizes to rationalise existing drill sizes (Check with Cranfield University machining standards):

H tolerances to be used where possible:

Tooling / jigging holes to be 6mm H8 where possible:

Freeze fit bushed holes to be H7 reamed:

Loctite bushed holes to be clearance holes:

Clearance, fastener, anchor nut etc. holes to be H11:

Holes to be normal to surfaces:

Blind holes to have angle of drill tip on drawing:

Countersinks to be modelled on details or dimensioned on 2d drawing:

Holes that require modelling : 12.5 mm & above: Jigging / Tooling holes: D shaped holes:

Holes below 12.5 mm to have point & vector.


26

Figure 21:-ASME 14.5M Geometrical Dimensioning and Tolerancing / F,D&T.

Fig 21(a):-2-D Catia Geometrical Dimensioning & Tolerancing. Fig 21(b):- 3-D Catia Functional Dimensioning & Tolerancing.

Datum axis is created to replicate assembly build philosophy (e.g. datum face & 2 tooling holes )

Identify features & tolerances to be controlled on assembly (e.g. positional tolerances, profile tolerance, flatness

tolerance etc.

Inspect in restrained condition (light finger pressure) unless specified in freestate.

Inspect on a CMM (co-ordinate measuring machine) which has a six degrees of freedom i.e. linear X,Y,Z & rotational X,Y,Z.

Boxed dimensions to 3 decimal points on metric drawings & 4 decimal points on imperial drawings.


27

SECTION 2:- MY CATIA V5.R20 DESIGN CAPABILITY MACHINED PARTS.

See references (2), (5), and (6) for all methodologies used in this section.


28

Outside

No Hyperlink

Hyperlink to Task

KEY

Single or

Multi-Use

Part?

Start

Insert Bodies

& Geometrical Sets

Snap data to

Key Diagram

Is part

correctly

positioned in

Production

Assy?

Y

Copy / Paste Special

As Result required

reference elements

N

Begin Modelling Multi-Use

Single-Use

Copy / Paste Special

A\C axis As Result in

Production Assembly

Inside or

Outside of

Production

Assy?

Inside

Single or

Multi-Use

Part?

Copy / Paste Special A\C axis As

Result Outside of Assembly

Single-Use

Multi-Use

Chart 1:- General Model Conditioning Process: Single & Multi-Use Parts

Task 1(a)

Task 1(b) Task 2

Task 3


Task 1(a):- Copy / Paste Special As Result - A\C Axis Outside the Production Assembly

The A\C axis and the parts datum axis is copied

into the model outside of the Production

Assembly product structure.

Method:-

1. Begin a new Part:

2. Open the Key Datum part either in its own

window (as illustrated), or its assembly window.

If the latter, the Key Datum part needs to be

active within the Product Structure:

3. Firstly copy the REF_A\C axis (naming is project

dependant) in the Key Datum part:

4. Paste the copied axis into the new part using

the Paste Special As Result option:

5. Repeat the process to copy in the new parts

Datum Axis from the Key Datum part

e.g. J/XXX/1 FRAME DATUM X700:

3

5

4

1 2

5

29


Task 1(b):- Copy / Paste Special As Result - A\C Axis in Production Assembly.

The A\C axis is copied into the model within the

Production Assembly product structure.

Method:-

1. Activate the part containing the reference A\C

axis (naming is project dependant):

2. MB3 on the A\C axis and select Copy in the

contextual menu:

3. Activate the receiving part for the A\C axis:

2

1

3

30


Task 1(b):- Copy / Paste Special As Result - A\C Axis in Production Assembly.

The A\C axis is copied into the model within the

Production Assembly product structure.

Method:-

4. MB3 on the active part node and select Paste

Special in the contextual menu:

5. Select As Result in the Paste Special window:

6. Click OK and the A\C axis is copied into the

receiving part as an isolated element:

7. Ensure Absolute Axis System of part is current

e.g. Gold in colour.

If not, MB3 on Absolute Axis System and select

Set As Current via the contextual menu

4

5

6

7

31


Task 2:- Inserting Bodies and Geometrical Sets.

This task is common to both Single and Multi-use

parts and regards the preparation of the parts

Specification Tree with respect to the addition of

Geometrical Sets; Reference Geometries;

additional Bodies, etc., to facilitate the modelling

process

Method:-

1. Use the Insert -> Body, and/or Insert ->

Geometrical Set functions to build the model

structure

2. Illustrated is a suggested structure, however the

content may vary depending upon the part type

3. If necessary, you can re-arrange the items

position in the tree using the Reorder Children

function as illustrated

4. Select item(s) to be reordered, then click on the

green arrows to reposition them in the tree until

the required structure is achieved, then click OK

1

2

3

32


Task 2:- Inserting Bodies and Geometrical Sets (continued).

Include additional Geometrical Sets and Bodies

to further manage the structure of the data

Method:-

5. Creating a structure within an existing

Geometrical Set enables you to manage various

aspects of the geometry more distinctly

6. You can add additional Bodies in advance, or

during the modelling process

As Geometrical Sets, the Bodies can be re-

ordered into a logical sequence in the structure

Typically as a rule of thumb, adopt the Boolean

method of modelling if the Specification Tree is

likely to exceed 20 features

5

6

33


Example Specification Tree Structures

34

Machined Part

Generative Sheet

Metal Part

Multi-surface Part

- Option 2

Task 2:- Inserting Bodies and Geometrical Sets (continued).


Task 3:- Copy / Paste Special As Result: Reference Elements.

Copy / Paste As Result the reference element(s)

to be used for the design e.g. Surfaces, Datum

Planes, etc., into the appropriate geometrical set

within the part.

Note: task is not applicable to Multi-Use parts

Method:-

1. Activate the part within the Production Assembly

containing the reference element(s):

2. Locate the e.g. PORT Master Surfaces,

elements within the Specification Tree of the

reference part and select them:

3. MB3 on any one of the chosen elements and

select Copy in the contextual menu:

1

2

3

35


Task 3: Copy / Paste Special As Result: Reference Elements (continued).

Method:-

4. Activate the receiving part e.g. FRAME_700:

5. Copy / Paste Special As Result, the selected

elements into the relevant geometrical set within

the receiving model structure:

6. Repeat the process for the STBD Master

Surfaces:

7. Following the pasting of the PORT & STBD

surfaces the content of the geometrical sets is as

illustrated:

The process is repeated until all the required

reference elements are copied into the receiving

part to facilitate its design.

5

4

7


Cranfield Aerospace Design Standards used throughout the project.

When creating a new part ensure an axis system has been created. If not create one at 0, 0, 0:

Ensure Part Number attribute and the CATPart filename prefix are the same (based upon project part

naming convention):

Modelling location is dictated by part type and Project Specifications.

Refer to document design standards for specific Model Conditioning rules regarding positioning

of Single and Multi-use parts.

Insert Bodies and Geometrical Sets as required and rename them with short meaningful, descriptive names.

The name can be new, or appended to the system generated name.

More specific model conditioning requirements are outlined below in this presentation for Machined Parts

and Sheet Metal.

37


The objective of this exercise was to design a fast jet fuselage frame based only on the Outer

Mould Line surface model of the forward fuselage, and the key datum model of the forward

fuselage frame and longeron stations. The modeling exercise followed the stages outlined below to

produce the Frame_X700 model shown in figures 26 and 27 and can be examined at an interview

on my laptop.

Stage 1:- Build the Vehicle Assembly Product Structure: Insert / Position / Condition part

FRAME_X-700.

Stage 2:- Create Stiffener Layout Sketch: Define Stiffener Planes: Remove FWD_Body from

the base feature.

Stage 3:- Create External Joggle body and Remove.

Stage 4:- Create the FWD Stiffeners figure 22.

Stage 5:- Remove the Stiffener Caps body: Create and Add Picture Frame body.

Stage 6:- Create reference sketch for penetrations: Create sketch for Pad Ups: Create Pad Ups

and Penetration features and outer Joggle.

Stage 7:- Create Fuel Sealing Groove for FWD face each side.

Stage 8:- Apply Fillet radii to Stiffener Walls and Caps.

Stage 9:- Create an additional body containing the parts penetrations: The penetrations are

created using the Hole function, and positioned according to the previously created reference

sketch.

Stage 10:- Repeat stages 1-9 for aft side of the frame where appropriate.

38

Capability Maintenance example :- 1 Machined Part FRAME_X-700


Reference sketches are used to determine

the layout or positioning of key features of

the design

The example illustrated shows a Stiffener

Layout sketch

The sketch is subsequently used for the

creation of a series of Planes which act as

sketch supports for the Stiffener Feature

sketches

Application of Reference Sketches to determine key design features.


In addition, it is also possible to use a

Reference sketches as symmetry

elements in the definition of other

sketches.

This example shows how a series of

Pocket profiles could be constrained to the

Reference sketch

If the Reference sketch is modified,

elements referencing the modified

element(s) are repositioned accordingly as

shown in the lower image

Application of Reference Sketches to determine key design features.


It is permissible to add a geometrical set to

the part Specification Tree specifically for

the management of sketches in order to

locate them readily rather than search

through the tree for them

Note that features created from these

sketches clone the sketch on which they

are based such that all are highlighted

when anyone one of them are selected

If the sketches in the PartBody appear as

shown, but are not visible on screen it is

likely that the SKETCHES geometrical set

is hidden

The Sketch Management process employed in the frame design exercise.

Cloned

Sketches

PartBody sketch in show

but not visible in model


As an alternative to using a geometrical set as a

container for all sketches, you could consider

using them only for Reference sketches

Sketches in the tree, at any level, can be

presented to you more logically than in a

geometrical set by using the menu function Tools

-> Parameterization Analysis

By selecting on in the window, the location of

the original sketches in the Specification Tree

are shown clones are not shown

A further benefit of the function, in terms of sketch

management, is the capability to also identify

sketches in a variety of solving states e.g. under

or over-constrained, etc.

Further uses could also be to:

- verify if other issues exist within the model

- simplify the presentation of Specification

Tree entities e.g. Bodies

- display only Knowledge entities

The Sketch Management process employed in the frame design exercise.


As the design task progresses, the content

of the geometrical sets increases,

sometimes to the point where identifying

relevant geometry is problematic due to the

quantity of elements

Typically elements used to construct other

geometry are only likely to need to be

modified occasionally, if at all

The Group function can package away

such elements, yet they remain accessible

for modification when / if required

In this example the only elements to be

visible in the tree are the two which are

currently shown

Note the difference between the tree

length of the geometrical set and the

Group, and then consider how many other

elements in other geometrical sets could

be managed in the same way?

Geometrical Sets Group Function employed in the frame design exercise.


To Create or Manipulate a Group

MB3 on geometrical set & select Create

Group via contextual menu

Select required Inputs the elements to

remain visible in the specification tree

Click OK to create the Group

MB3 on Group and select either to

(a) expand the content to e.g. modify an

element

(b) edit the Input list

(c) remove the group and revert back to a

geometrical set

Select Collapse Group to repackage

elements

1

2

3

4

4b

4c

4a

5

Geometrical Sets Group Function employed in the frame design exercise.


FWD Side Features:-

Figure 22:- Capability Maintenance example 1 Machined Part FRAME_X-700

Penetrations

Stiffeners

Picture Frame

Pad Up

Pocket Base &

System Pad

Ups

Internal \ External

Joggles

Groove (Fuel Sealing)

- One Each Side

Stiffener

Caps

45


This is a double sided 5 axis machining and the complete frame was modelled as shown

starting with outer mould line (OML) surfaces.

FWD Side AFT Side

Figure 23:- Capability Maintenance example 1 Machined Part FRAME_X-700

46


47

Figure 24:- Key datum model for Machined FRAME_700 design position data.


48

Figure 25:- Master OML surface geometry for Machined FRAME_700 design.


Figure 26:- Example of my Catia V5.20 Frame X-700 Fwd face from OML surfaces.

49


50

Figure 27:- Example of my Catia V5.20 Frame X-700 Aft face from OML surfaces.


Figure 28:- Example of my Catia V5.20 Frame X-700 Aft face with FDT applied.

51


52

Figure 29:- Example of my Catia V5.20 metallic design of undercarriage component.


53

Figure 30(a):- Example of the layout of the pre-drilled web fastener holes in the rib posts.


54

Figure 30(b):- Example of the layout of the flange fastener holes in the rib posts.


55

Figure 30(c):- The projection of the rib post flange fastener layout on to the OML.

Flange fastener points projected to OML.

Flange fastener vector line

normal to OML.

Wing Top Cover Skin OML Surface.


56

Figure 30(d):- Example of the layout of the completed Rib Posts 34.


57

Figure 31(a):- Example of the layout of the flange fastener holes in the spar splice.

Flange fastener nutplate footprint projected to

IML for clearance assessment.


58

Figure 31(a):- Example of the layout of assembled spar splice.


Figure 32:- My Catia V5.20 preliminary metallic design FATA Al/Li Rib 12.

59


Chart 2:- Drafting of Machined Parts and Assemblies Catia V5.20 metallic design.

Create new drawing

Create Project Specific Drawing Border

Filtering Data for Assembly Views

Instantiate Catalogue Details if required

Annotate Views if required

Save CAT

Drawing

View Creation

View Modification Options

Assembly View Content Modification

Create Drawing Comments

= Hyperlinks

Manual Pre-selection

Scenes

From Scenes

Spatial Query

Lock the Views

Overload Properties

Modify Links

Local Axis System

No Hyperlink

Hyperlink to Task

KEY

60


61

Figure 33:- Example of my Catia V5.20 metallic machined assembly.


62

Figure 34:- Example of my Catia V5.20 Sheet metal part design.


Figure 35:- Example of my Catia V5.20 Frame X-700 draft views GD&T applied.

63


64

SECTION 3:- CATIA V5.R20 DESIGN EXAMPLES SHEET METAL PARTS.



65

Generative Sheet Metal is typically used to design parts which are typically manufactured using V benders or press tooling. This workbench cannot produce features such as Flanges

which reference surface geometry, or to create Joggle features.

Aerospace Sheet Metal is typically used to design parts which are typically manufactured via the Hydroforming process. This workbench can produce features such as Flanges which

reference surface geometry, and to create Joggle features.

Functionality Overlap Certain functions are common to both workbenches (sometimes with limitations), and others are workbench specific. The following table outlines these

functions:

Generative Sheet Metal only icons

Aerospace Sheet Metal only icons

Common Icons

Limited functionality compared to

Generative Sheet Metal workbench

Design of sheet metallic components for capability maintenance.


Chart 3:- The BAE Systems Catia V5 New Part Sheet metal process overview.

Select Generative Sheet Metal Design from Shareable Products tab in Tools / Options / General

Create New file

Enter Generative Sheet Metal Design workbench

Set Sheet Metal Parameters

Create Wall

Create Features

Check Flattened Component

Create Block and Heel Lines / Curves

Save CATPart

66


Figure 36:- My Catia V5.R20 Aerospace Sheet Metal Frame from OML surfaces.

67


68

Figure 37:- My Catia V5.R20 Aerospace Sheet Metal Floor panel design from surfaces.


69

Figure 38:- Example of my Catia V5.R20 Aerospace Sheet Metal Fairing design.


70

Figure 39:- My Catia V5.R20 Aerospace Sheet Metal Bracket from reference geometry.


71

Figure 40:- Example of my Catia V5.R20 Generative sheet metal design work.


Figure 41:- Example of my Catia V5.R20 Generative sheet metal design work.


SECTION 4:- CATIA V5.R20 EXAMPLES ASSEMBLY DESIGN.

73 See references (2), (5), and (6) for all methodologies used in this section.


N

Y

Is a Key

Diagram

available?

Does

Production

Assembly

exist?

Does Data

already

exist?

Is Reference

Geometry modelled

in local axis?

Chart 4:- Adding To or Creating Data in a Production Assembly.

Start

Y

N

Verify Position of Data

N

Open Production Assembly Create Production Assembly

Insert Existing Data Add New Data

Y Snap data to Key Diagram

Position as required

N

Y

No Hyperlink

Hyperlink to Task

KEY

74


The methodology applied to product assembly creation.

Is also referred to as the Vehicle Assembly

In CATIA V5 terms, it is the CATProduct holding all

the CATIA data relevant to the design of this

vehicle, in effect, it is the virtual aircraft - the DMU

Within this structure, key parts are located with

respect to a Key Datum product which was also

used to position the reference geometry

To ensure engineers working on the project have

access to the correct reference data, the content of

the product structure is organised such that the data

is held within master models located in the upper

region of the tree structure in a component node

named REF_REFERENCE_GEOMETRY

Designers take the required reference geometry

from the master model(s) into their own after

inserting and positioning it correctly within the A\C

environment

This master geometries methodology will be

employed throughout the FATA project and was

used in the assemblies of the robot shown in figure

42 as well as the analysis assemblies in the next

section.

Production (or Vehicle) Assembly Reference geometry container

Reference geometry

assemblies by design

discipline

Design assemblies

by design discipline

Std. Parts container

75


Chart 5:- Catia V5. R20 Assembly Positioning Options.

Various positioning options are available, the majority of which were covered during the Fundamentals course

The functions illustrated are available in the Assembly Design and Digital Mock-Up (DMU) Navigator

workbenches

These functions illustrated have been used by myself at Cranfield University since 2003 and BAE Systems from 2009

and are employed on the FATA project.

76


77

Figure 42:- Example of my Catia V5.20 FATA OB LE Spar assembly in DMU.


Chart 6:- Creating a Production Assembly with Reference Geometry.

Create New Production Assembly

Create a New Reference Component and Fix

Check for latest and Insert Key

Diagram into Reference

Component and Fix

Check for latest and Insert

Reference Geometry into

Reference Component

Snap data to Key Diagram and Fix

Is the Reference Geometry

modelled in local axis?

Y

N

N

Y

Fix Geometry

Is a Key Diagram available?

Insert Reference Geometry into

Reference Component

Position as required

Fix Geometry

No Hyperlink

Hyperlink to Task

KEY

78


79

SECTION 5:- MY CATIA V5.R20 GSA DESIGN EXAMPLES.



The objective of this work is toolset skills enhancement with the Catia V5.R20 GSA system, below

are the limitations of the Catia V5 R20 FEA toolset which need to be considered when applying this

toolset:-

a)Material Linearity:- In Catia, it is assumed that the stress and strain are linearly related through

Hooks law, therefore metals should not be loaded into the plastic deformation region, and rubber

type materials cannot be analyzed by this toolset.

b)Small Strains:- The strains used in Catia are the infinitesimal engineering strains which are

consistent with the limitations above in (a). As an example, problems such as crushing of tubes

cannot be handled by this software.

c)Limited Contact Capabilities:- Although Catia is capable of solving certain contact problems,

they must be within the limitations noted above in (a) and (b). Furthermore, no friction effects can

be modeled by the software.

d)Limited Dynamics:- The transient response in Catia V5 is based on model superposition.

Therefore a sufficient number of modes have to be extracted in order to get good results. The direct

integration of the equations of motion are not available in this version.

e)Beam and Shell Formation:- In these elements shear effects are neglected. Therefore, the

results of thick beams and shells may not be very accurate although not an aerospace issue.

Although these issues seem severe limitations most basic mechanical design problems can be

analyzed using this tool set as such problems are governed by linear elastic analysis.

80

Catia V5.R20, FEA Skills toolset enhancement evaluating system limitations.


The stresses evaluated in Catia V5.20 GSA are von Mises stresses (after Richard von Mises (1883-

1913) in accordance with Maximum Distortion Energy Theory which states the only that portion of

the normal stress which causes shear distortion acts to promote yielding. These are called the

stress deviations or deviatoric stresses:- x : y : z and are defined such that:-

x = x + : y = y + : z = z + (eq 1.)

Substituting these expressions for the normal stresses in the strain energy density formula yields:-

uo = uv + ud

where:-

Uv = (1/2K) ud = (1/2E) (x + y + z ) v /E (x y + x z + y z ) + 1/2G (xy + yz + zx )

Here, uv is the portion of the strain energy density due to volume change, and ud is the distortion

strain energy density. From Equation 1 and the definition of hydrostatic stress, = (x + y + z ),

the deviatoric stresses can be written :-

x = x - (y + z): y = y - (x + z): z = z - (x + y)

These together with equation for the shear modulus in isotropic material:- G = E / 2(1+v) gives the

following expression for the distortion strain energy density:-

ud = 1+v / 3E {1/2 [(x y) + (x z) + (y z)] + 3(xy + xz + yz) } (eq 2.)

For example in a uniaxial tension test, the only non zero stress is x hence the distortion strain

energy density when yield occurs (x = y) is:-

ud = (1+v / 3E ) y

81



According to the maximum distortion energy theory of failure, yield occurs when the distortion strain

energy density equals the distortion strain energy density at the yield point of a tensile test

specimen therefore:-

1+v / 3E {1/2 [(x y) + (x z) + (y z)] + 3(xy + xz + yz) } = (1+v / 3E) y

The von Mises stress, vm , a point is defined as:-

vm 1/2 [(x y) + (x z) + (y z)] + 3(xy + xz + yz) (eq 3.)

Therefore according to the maximum distortion energy theory, the failure criterion is:-

vm = y (eq 4.)

Here vm is an invariant, having the same value regardless of the coordinate system used, so that in

terms of the maximum, minimum and intermediate values of principle stresses:-

vm 1/2 [(max min) + (max int) + (int min)] (eq 5.)

or

vm 1/2 (max min) 1+ (max int / max min) + (int min / max min)

From this one can deduce that:-

0.866 (max min) < vm < (max min) (eq 6.)

Therefore von Mises stresses are less than the maximum principle stresses, which means that the

maximum shear stress failure criterion is slightly more conservative than the distortion energy

criterion. In plane stress:-

vm = (x + y - x y) + 3 xy (eq 7.)

82



There are two types of solid element available in Catia V5.R20 Generative Structural Analysis

which are Linear and Parabolic. Both are referred to as tetrahedron elements shown below.

Limited Hex elements are also available. As are Linear and Parabolic shell elements as well are

limited QUAD elements.

83

Solid Tetrahedron Elements.

Linear. Parabolic.

The Linear tetrahedron elements are faster computationally but less accurate. On the other hand,

the Parabolic elements require more computational power but lead to more accurate results.

Parabolic elements have the very important feature that they can fit curved surfaces better than

Linear elements. In Catia V5 solid machined parts are generally analyzed using solid elements,

where as thin walled and sheet structures are analyzed using shell elements. Linear triangular

shell elements have three nodes each having six degrees of freedom, i.e. three translations and

three rotations, the thickness of the shell has to be provided as a Catia input. As is the case with

the solid tetrahedron elements the Parabolic elements are more accurate.

Linear

18 DoF.

Parabolic

36 DoF.

Sheet Triangular Shell Elements.

Catia V5.R20, FEA Skills toolset enhancement evaluating system components .


The element size and sag icons appear on each part on entering the Analysis & Simulation >

Generative Structural Analysis toolset. The concept of element size is self explanatory, i.e. the

smaller the element size the more accurate the results at the expense of longer computation time

and processor power. The sag is a unique Catia term, in FEA the geometry of a part is

approximated with elements, and the surface of the part and FEA approximation of a part do

exactly coincide. The sag parameter controls the deviation between the two, therefore the smaller

the sag value generally the better the results.

Catia V5s Finite Element Analysis module is geometrically based, therefore the boundary

conditions cannot be applied to nodes and elements. The boundary conditions can only be applied

at the part level. On entering the Generative Structural Analysis workbench, the parts are

automatically hidden. Therefore, before boundary conditions can be applied, the part must be

brought back into the visual working space, and this was carried out by pointing the cursor to the

top of the tree, the Links Manager.1 branch, right-clicking, selecting Show. At this point both the

part is visible and the mesh is superimposed on it, the latter was hidden by pointing the cursor at

Nodes and Elements and right-clicking Hide. This has been the methodology for each worked

example in this presentation, figures 43,45,47,48,50,51,53 show the parts, with constraints and

loading, where figures 44,46,49,52,54 show the total displacement magnitude analysis and Von

Mises stress analysis with maximum and minimum values in each case. The three analysis

examples in this presentation form a small part of my Workbook two which is leading into complex

studies of airframe structures.

84

Catia V5.R20, FEA Skills toolset enhancement evaluating system methods.


To perform an accurate finite element analysis of a structure a number of stages have to be passed

through during the construction of a suitable simulation model. In passing through these stages

several representations of the structural problem have to be crated and subsequently assessed

from an error viewpoint, these correspond to the various levels of abstraction which the stress

engineer has to consider in creating a finite element model.

The most important is the Idealised World which takes the real world model and turns it into a form

which can be analysed by the Finite Element Method. This is a very profound level of abstraction

which converts the structural model with its welds, rivets, bonded joints etc. into a smoothed model

in which each component, together with its boundary condition, loading situation etc. can be

mathematically defined. Thus, the decisions concerning such factors as the linearity or otherwise of

the structural behaviour are made at this stage. It is the most critical part of the whole finite element

analysis process as in a loose sense, the construction of an idealised world represents a transition

from a world exterior to the computer to an interior world.

Once the idealisation process has been performed a number of closely related representations are

constructed and are illustrated on the left hand side of Chart 7. These allow the generation of a

finite element model and, subsequently a finite element solution. Although they have a part to play

in the SAFESA Method they are not relevant to the description of the method as presented here.

The key aspects of the SAFESA are the identification of errors created in the idealisation process

and their treatment so that the eventual solution coming from the analysis corresponds in an error

controlled manner to the behaviour of the real world structure. 85

Catia V5.R20, FEA application of the SAFESA procedure to current work.


The SAFESA method is a systematic error control procedure which is used to support Finite

Element Modelling and ensures the total consistence of error control irrespective of the end users

level of experience. Errors are injected into an analysis through a number of individual causes

which can be categorised under a number of general headings: -

Mathematical model of the structure: The derivation of an appropriate mathematical model to

fit the description of the real structure employs physical laws, mathematical manipulation and

behavioural assumptions. The behaviour assumptions are needed so that the physical laws can

be manipulated mathematically to yield a useful set of expressions. Each behavioural

assumption introduces approximations and associated errors. In certain cases the model

reduces the dimensionality of the problem for example, from 3 to 2 dimensions.

Domain: Domain error relates to the geometrical region and the associated geometrical

simplification of the structures being analysed. The domain in most analysis is typically not

complete and may be limited to a portion of the total structure, with boundary conditions applied

explicitly at the interface with the rest of the structure. Often errors are generated by eliminating

or simplifying geometric detail. For example small cut - outs may be ignored or local stiffening

material might be smeared into adjacent structure.

Material: The structural model to be used for the analysis, the dimensional reduction and

associated mathematical manipulations fix the framework within which the material response is

described. This can involve significant approximation and is a potential source of error with

structural idealisation.

86



87

Chart 7:- FEA modeling and SAFESA methods of error control.

SAFESA Error

Control

(1) Idealisation (2) Discretisation

& Meshing (3) Solving

(4) Post -

Processing

(5) Obtain

Qualification

Response

(6) Calculation of

Allowable

Response

(7) Comparison of

Qualification &

Allowable Response

(8) Validation

Review

(1.1) Global

Boundaries &

Loading Actions

(1.2) Global Load

Paths & Geometry

(1.3) Structural

Sub-Division

(1.4) Boundaries &

Loading Actions

for Features

(1.5) Load Paths &

Geometries for

Features

(1.6) Preliminary

Error Assessment

& Planning

(8.1) Follow Up

Error Assessment

(8.2) Test Program

(8.3) Experience

Data Key.

FEA Modeling

Start

End


Boundary conditions and loading: The structural model also defines the form or type of the

boundary condition that can be applied and these are difficult to abstract from the physical

situation being analysed.

Error Treatment and Error Control: -In the preceding paragraphs the nature of the errors which

can occur in the analysis of a real world structure by the application of the Finite Element Method

has been highlighted. Realising that errors are present in a particular phase of the analysis process

is the beginning of the error control process, but methods required to treat and hopefully, bound

them. In performing this error control process there are two broad approaches adopted by

SAFESA. Firstly there are methods of error control which rely on a calculation process and which

often require exploiting the results from a finite element analysis. Essentially these are interior to

the analysis process and cannot supply objective error control but have a very important role to

play. Secondly there are exterior procedures which can be used to provide a measure of

objectivity, and these attempt to exploit information which is extracted from the real world problem.

These treatments are briefly outlined below: -

1) Interior Calculation Based Error Treatment Techniques: - Interior methods mainly employ

finite element models to check finite element models either by employing sequences of models

or by extracting the maximum information from a given model. Such a process is, essentially,

cyclic in nature with the analyst processing through a series of steps involving feedback loops.

Thus in an ideal situation the application of interior methods would begin with scoping

calculations, followed by hierarchical modelling and concluding with sensitivity studies.

88



2) Exterior Error Treatment Techniques: - As has already been discussed the interior methods

are not grounded in a reality which includes the real world. They represent a set of techniques

which, providing a datum point is available, are able to treat and control the additional errors

which are driving the analysis away from the datum. The datum being referred to in this case is

the finite element model which is directly related to a given real world structure together with

errors which cause the model to deviate from real world behaviour. In order to create a specific

datum structure it is necessary to characterise the structure in a unique manner.

The primary method for creating a starting point for the majority of analysts is to employ past

experience. Whilst this is an effective way to make progress it is not often done in a systematic

manner which allows a logical connection from the current problem to previously encountered

similar ones. Engineers rely on intuitive knowledge in deciding that one structure is sufficiently

close to a second example that the modelling procedures used in the first one, can be applied

to the second. Many years of experience in solving problems using finite element analysis

methods are a very valuable commodity in solving new structural analysis problems.

The question of how to relate one structure to another through a logical connection requires the

establishment of similarity rules. These, in turn, require that a set of parameters be identified

which uniquely define a given structure. A specific datum model for a given problem may be

either a complete model for a comparable problem or a model for a major sub component. In

the case of a complex structural design the error treatment process may therefore, require

several such models employed in a hierarchical sequence.

89



The individual processes described above for treating errors need to be embedded in a routine

process if they are to be of any value to an analyst. This embedding process has resulted in the

creation of the SAFESA Method. It transforms the error treatment and control processes into an

applicable, quality control, step-wise procedure.

Each step within this process may itself be considered as a procedure with input data, a process or

action resulting in the generation of an output data set as outlined on the right hand side of Chart 7

in steps 1.1 through 1.6. Although these steps feed information from one step to the next in a linear

sequential manner, feedback loops are possible as indicated by the dotted lines. Indeed it is

unlikely that a simple pass through the structure will be satisfactory. Initial assumptions about

structural behaviour etc. are often incorrect and require revising. The process is decomposing the

structure in a step-wise manner to chase down errors. At each step the errors are identified and the

associated treatment procedures applied. A flagging process is used to identify that errors at a

specific stage in the Method have not been adequately treated and must be handled satisfactorily at

a later stage or during one of the feedback loops. If an error source cannot be treated this will

remain flagged as untreated and will be picked up at step 8.2 when a test programme is defined to

provide the analyst with the information to understand the nature and influence of the error.

The Method is therefore, an algorithm with a stopping criteria which requires that no error flags

remain set when the final step is completed. All the aspects relating to error sources and the control

of errors discussed above are incorporated, with the exception of the use of a datum and the

associated similarity rules. The latter is omitted due to the current incomplete state of this work. The

remaining parts of the Method are comprehensive and are applicable to the analysis of any

structure, and Table 1 error treatment techniques for identified errors.

90



ERROR SOURCES.

ERROR TREATMENT.

First Stage. Second & Subsequent Stages.

Domain. Experience / Simplification /

Calculations. Model improvement.

Boundary conditions. Experience / Existing test results /

Simple calculations.

Sensitivity analysis / Model

improvement.

Loading. Experience / Existing test results /

Simple calculations.

Sensitivity analysis / Model

improvement.

Behaviour. Experience / Simple calculations. Comparison with physical limits /

Model improvement.

Material. Experience / Simple calculations. Sensitivity analysis.

91

Table 1:- Error treatment techniques for the identified error sources.


Four examples of these ongoing studies are given here:-

1)Bearing Shaft Assembly using Analysis Connections:- Problem statement:- The assembly

shown in figure 43 consist of a shaft of 1 diameter and length 6, and two bearings with dimensions

as shown. All parts are made of aluminum with E=10.15E7 psi and v = 0.346. The bottom faces of

the bearings are clamped and the shaft is subjected to a total downward load of 100lb distributed

on its surface. The objective of this analysis was to predict stresses and deflections in the structure.

Full stress report was produced the results are shown in figures 44(a) and 44(b).

2)Tensile Test Specimen Assembly:- Problem statement:- The assembly consisted of two steel

pins (1diam x 3 long) and an aluminum block (10x 4x1). The constrained and loaded assembly

is shown in figure 45. The end faces of the bottom pin are clamped, and the end faces of the top

pin are given a displacement of 0.01 (0.254mm) causing the block to stretch. The objective was to

determine the force necessary to cause this deflection and predict the stresses in the structure, for

this analysis Parabolic Tetrahedron elements were used for this analysis. A full stress report was

produced, the results are shown in figures 46(a) and 46(b).

3)Spot Weld Analysis:- Two sheets of made of steel having a thickness of 0.03 are spot welded

together at four dotted points as shown in figure 47. The edge AB of the bottom plate is clamped

and the edge CD of the top L section is loaded with a 10lb force. All the dimensions shown are in

inches. The objective was to use Catia V5.R20 Generative Structural Analysis to predict the

stresses in these parts. Linear Triangular elements were used for this analysis. A full stress report

was produced, the results are shown in figures 48 to 49.

92

Catia V5.R20, FEA Skills toolset enhancement worked examples.


4) Analysis of a fastened assembly:- This assembly consisted of two plates, clamped together

with a preloaded steel bolt. One plate was loaded causing the bending of the entire structure.

The objective of this analysis was to predict the stresses and deflections to which the assembly

was subjected. The top plate was 1 by 1 square with a thickness of 0.125: the bottom plate

was 1 by 2 with a thickness of 0.125 each had a 0.125 radius hole 0.5 from the trailing edge

as shown in figure 50. The bolt had a shaft radius of 0.125 and length 0.4, and a head radius

of 0.2 and thickness of 0.1. The assembly was constructed using Coincidence constraint's and

the material steel was applied. The resultant assembly being meshed, restrained, and contact

connected as shown in figure 51, then a tightening force of 50lbs was applied to the bolt

tightening connection, analysis was then undertaken of displacement, and Von Mises stress in

the assembly, the results are shown in figures 52(a) and (b). Subsequently a distributed load of

100lbf was applied to the leading edge of the lower plate as shown in figure 53 in the Z direction

as a distributed force, and the assembly was re-analysed for displacement and Von Mises

stress values, the results are shown in figures 54(a) and (b).

The final outcome of this research will be the analysis of metallic and composite wing structures in

support of my FATA wing research program.

93

Catia V5.R20, FEA Skills toolset enhancement worked examples.


94

Figure 43:- Example my Catia V5.R20 FEA:- bearing assembly exercise load and constraints.

2 inch 1 inch


Figure 44:- My Catia V5.R20 aluminum bearing beam assembly analysis.

Figure 44(a) :- Total displacement magnitude

analysis of the bearing beam assembly.

Maximum deflection = 0.000881691

Minimum = 0

95

Figure 44(b) :- Von Mises Stress (nodal

values) analysis of the same bearing beam

assembly. Maximum stress = 1902.12 psi,

Minimum stress = 17.7862 psi.


96

Figure 45:- Example my Catia V5.R20 FEA:- tensile specimen exercise load and constraints.


97

Figure 46:- My Catia V5.R20 two material tensile test specimen assembly analysis.


analysis of the tensile specimen assembly.

Maximum deflection = 0.01 Minimum = 0in

the pins and Maximum deflection of 0.00851

Minimum = 0.00148 in the test block.

Figure 46(b) :- Von Mises Stress (nodal values)

analysis of the same tensile specimen

assembly. Maximum stress = 50732.6 psi, in the

top pin Minimum stress = 51.8327 psi in the

test block.


98

Figure 47:- My Catia V5.R20 FEA Spot welded sheet assembly problem structure.

C

D

A

B

5 in

12 in

3 in

4 in

2 in

2 in

2 in

2 in

2 in

C

D

A

B

5 in

12 in

3 in

4 in

2 in

2 in

2 in

2 in

2 in

1in

10 in

Sheet Material = Steel:

Sheet Thickness = 0.03 inch:

Top L section loaded edge C-D:

Bottom plate clamped edge A-B.


99

Figure 48:- Example my Catia V5.R20 FEA:- Spot welded sheet exercise load and constraints.


100


analysis of the spot welded sheet assembly.

Maximum deflection = 1.38369 Minimum = 0.


values) analysis of the spot welded sheet

assembly. Maximum stress = 35325.8psi,

Minimum stress = 265.515psi. Maximum

stress was in the weld line as expected.

Figure 49:- My Catia V5.R20 Sheet steel spot welded assembly analysis.


101

Figure 50:- Example my Catia V5.R20 Bolted assembly components for analysis.


102

Figure 51:- Example my Catia V5.R20 Bolted assembly constrained and preload for analysis.


103

Figure 52:- My Catia V5.R20 Bolted assembly preload analysis.


values) analysis of preloaded bolted



stress the bolt as expected.

Figure 52(a):- Total displacement magnitude

analysis of the preloaded bolted plate

assembly. Maximum deflection = 3.35588e-

005 Minimum =1.0 the max value being in

the bolt as expected.


104

Figure 53:- Example my Catia V5.R20 Bolted assembly constrained meshed with distributed load.


105

Figure 54:- My Catia V5.R20 Bolted assembly preload with added end load analysis.

Figure 54(a) :- Total displacement

magnitude analysis of the loaded

bolted plate assembly. Maximum

deflection = 0.0448786 Minimum =

1.0 the max value being in the lower

plate edge as expected.


values) analysis of preloaded bolted



stress the bolt region as expected.


Although not the main focus of this study, new developments in the manufacturing of metallic

structural components are under investigation as an alternative to current high speed machining

which wastes a large part of the stock material, (reduced by near net forging). These new

innovative processes are termed Additive Manufacturing as they build up the material to form the

part instead of cutting away surplus material as is the case with current machining. GKN

Aerospace, Boeing, Airbus, and Cranfield University are all involved in research into this technology

for airframe applications and figure 55 illustrates how a leading edge rib structure could be

optimized for this process.

There are two types of Additive Manufacturing process which are: - (1) Powder Based

Technologies: (2) Wire Based Technologies, which will be outlined below based on a presentation

given by Dr. Wilson Wong GKN Aerospace (ref 13).

(1) Powder Technologies:- In this process powder is transferred from a hopper to the work build

plate and melted in the desired shape by either Electron Beam Melting: Selective Laser Melting.

Where as Nozzle Deposition feeds the powder through a nozzle direct to work under the laser.

Electron Beam Melting yields good mechanical properties and enables high part complexity, but

has relatively poor surface finish and is not as precise when compared to Selective Laser Melting.

Selective Laser Melting is highly accurate, and also enables high part complexity, but has a slow

part build up rate and develops residual stresses in the part. Nozzle Deposition features a higher

part build rate than the other two powder bed technologies and is suitable for build repairs, however

the method has a high power utilisation and is limited in part complexity. These processes and their

applications are shown in figures 56 and 57 respectively. 106

Section 6:- Advanced Metallic Technologies (Additive Manufacturing).


107

Advanced Metallic Technologies :- Additive Manufacturing (continued).

Figure 55:- Braced web leading edge rib candidate for Additive Manufacturing.

See reference (9), for all material reported in this section.


108

Nozzle Deposition

Direct Metal Deposition.

Selective Laser Melting.

Electron Beam Melting.

Figure 56:- Powder Based Additive Manufacturing Technologies.


109

Figure 57:- Powder Based Additive Manufacturing Technology applications.


(2) Wire Based Technologies:- In this process the material is feed to the work piece as a wire and

is deposited to form the product by either a laser or an electron beam as shown in figure 58. Laser

Wire Deposition this is relatively fast and is suitable for repairs, however is suited for low complexity

parts, and yields a relatively poor surface finish. Electron Beam Wire Deposition is also relatively

fast yielding good mechanical properties, but is also limited on part complexity, and imparts residual

stresses, requiring post processing. The applications of wire based deposition additive

manufacturing are shown in figure 59.

Additive manufacturing offers significant savings in raw material, energy, cutting fluids, and lead

time over conventional machining, and hence cost reductions. However there are issues that need

to be addressed to qualify these processes as the machining replacement for metallic materials and

these are:-

Materials Variables:

Material Allowables:

Process Variability (between machines):

Materials Properties Variation:

Raw Material Cost: Process Speed:

Machine Costs:

Design and Analysis Toolset.

All of which are being addressed by current research programs. 110

Advanced Metallic Technologies :- Additive Manufacturing (continued).


111

Wire

Electron

Beam

Electron Beam Wire Deposition.

Laser Wire Deposition.

Figure 58:- Wire Based Additive Manufacturing Technologies.


112

Figure 59:- Wire Deposition Additive Manufacturing Technology applications.


The High Speed Machining process reduces weigh, time, and cost over multi-part assemblies of

sheet aluminium components however the major limitation on the High Speed Machining processes

is vibration, and the focus of this section is to review published methods of reducing this vibration

applicable to aluminium alloys in airframe engineering. Factors effecting vibration are:- Dynamic

Stiffness between the tool tip and the work piece: The Force Balance between the cutting force and

the run out force: and the main factor is Chatter between the tool and the work piece.

As Chatter is the major factor effecting vibration it will be dealt with in some detail based on Boeing

published work. Chatter is a self excited vibration between the tool and the work piece which

results in the following:- (1) Large cutting forces: (2) Accelerated tool wear often resulting in a

catastrophic tool failure: (3) Creates unacceptable surface finish on work piece resulting in

part rejection: (4) Adversely affects the life of machine components.

113

Section 7:- High Speed Metallic Machining Research for Al alloys.

Tool

Deflection

Chip Thickness

Cutting

Force

Figure 60:- Effects of Chatter.


Controlling Chatter in HSM is highly depended on:- (a) tool spindle speeds Revolutions Per Minute

(RPM): (b) work piece chatter: and (c) the depth of cut of each tool set up to maximize Material

Removal Rate (MRR).

a) Selection of the optimum spindle speed:- This is in turn dependant on stability lodes which are a

function of machine / tool dynamics (which are different for each tool set-up and machine.

Therefore the testing of cutting parameters is undertaken using modal analysis to determine the

Machine Dynamics employing a MetalMax system. This enables a stability lobe of depth of cut

against RPM defining stable and unstable regions enabling stability predictions to be made, and

these analytical stability lobes provide an estimate of the optimum process parameters i.e.

spindle speed and Depth Of Cut (DOC). Analytical stability lobes provide an estimate of the

optimum processing parameters i.e. spindle speed and DOC, however experimental verification

is often required simplifying assumptions in chatter predictions, and accounting for variations in

the system dynamics at speed.

Experimental verification is achieved through cutting tests using actual production machine,

tools, holder, set length. Changes with speed make offline predictions difficult, and cutting tests

are performed by measuring the chatter frequency using sound (by microphone) because

sound is proportional to displacement of the tool tip, sensors at the base of the spindle are

usually ineffective because tool vibrations are usually very small in this area. The evaluation

spindle speed is selected as a multiple of the chatter frequency, ie

= *60 / # Teeth

Where = multiple, RPM = revolutions per minute.

114

Control of Chatter in High Speed Machining of Al alloys (continued).


To determine the optimum spindle speed the calculation employs the RPM equation as

illustrated in the example below:-

= *60 / # Teeth

For spindle with a chatter frequency of 2000Hz a speed of 60,000 RPM:-

1) 30,000 RPM for 40,000 RPM spindle gives 2 waves between subsequent teeth.



All cases maintain constant chip thickness.

115

Control of Chatter in High Speed Machining of Al alloys (continued).


Weak chatter control effects amplitude and volume of chatter. It has been found (references 8

and 9) that feed rates do not strongly affect the onset of chatter, and chatter is a function of

the phase relationship between the passing of subsequent teeth.

Reference 8 uses the Rambaudi example reproduced below:-

i. Spindle speed 24,000 RPM, 240 Inches Per Minute (IPM) feed rate, 0.750inch Radial

Depth of Cut (RDOC), 0.125inch Axial Depth of Cut (ADOC) = Chatter Free.

ii. Spindle speed 20,000 RPM, 40 IPM feed rate, 0.375inch RDOC, 0.250inch ADOC =

Sever Chatter in corners.

Spindle specific NC programming requires:- dynamics which are unique for spindles, tool

holders, and tools: machine

my metallic design capability maintenance studies update 9th october 2016

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