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COMPUTER AIDED DESIGN OF SHEET METAL DIE ASSEMBLY UTILISING

PRO | ENGINEER AND MECHANICA

Vamshikrishna Reddy Chada

B.Tech. Jawaharlal Nehru Technological University, India, 2007

PROJECT

Submitted in partial satisfaction ofThe requirements for the degree of

MASTER OF SCIENCE

in

MECHANICAL ENGINEERING

at

CALIFORNIA STATE UNIVERSITY, SACRAMENTO

FALL

2010


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A Project

by


Approved by:

________________________________, Committee ChairDr.Yong S.Suh

_________________________Date


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Student: Vamshikrishna Reddy Chada

I certify that these students have met the requirements for format contained in the

University format manual, and that this project is suitable for shelving in the Library and

credit is to be awarded for the project.

________________________, Graduate Coordinator _____________________Dr.Kenneth Sprott Date

Department of Mechanical Engineering


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Abstract

of



by


In recent years the development of more and more products has become a remarkable

trend in the automotive industry.The consumer demand for great variety and increasing

environmental concenrs are forcing manufacturers to improve product development

efficency encouraging the new desings in sheet metal die casting.The Pro Engineering

and Pro Engineering Mechancia is a widely applied tools for designing models and for

solving structural problems respectively.The punch,die and blankholder are three main

parts in this sheet metal die casting and these can be representedy by finite element

models,the die structure deflections and stress induced by loading condition can be

predicted and can be designed according to requirements.The role of the blank holder in

the generation of the restraining forces acting on the metal sheet is considered on top

most point.The known fact is the choice of restraining force distribution is a key point in

designing the sheet metal die.The factors that affect the actual restraining force

distribution are briefly analyzed,identifying control factors.This capability allows

achieving some actual advantages, considering that the technological development will


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supplies the engineers with hardware and software instruments able to analyze in short

time large problems.The Finite element analyis allows to foresee possible inconveniences

which could occur during the consturction by using only virtual models,before physical

model being made.

________________________________, Committee ChairDr.Yong S.Suh

______________________Date


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ACKNOWLEDGMENTS

While working on this project, some people helped me to reach where I am today and I

would like to thank all for their support and patience.

Firstly, I would like to thank Professor Dr. Yong S.Suh for giving me an opportunity to

do this project. His continuous support was the main thing that helped me to develop

immense interest on the project that led to designing of punch and die assembly with

emerging technologies. Dr.Yong S.Suh helped me by providing many sources of

information that needed from beginning of the project till the end. He was always there

to meet, talk and answer the questions that came across during the project.

Special thanks to my advisor Dr Kenneth Sprott for helping me to complete the writing of

this dissertation, without his encouragement and constant guidance I could not have

finished this report.

Finally, I would also like to thank all my family, friends and Mechanical engineering

department who helped me to complete this project work successfully. Without any of

the above-mentioned people the project would not have come out the way it did. Thank

you all.


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TABLE OF CONTENTS

Page

Acknowledgments...................................................................................................... VI

List of Figures ............................................................................................................. XI

Chapter

1. INTRODUCTION AND BACKGROUND ..............................................................1

1.1) Introduction ............................................................................................................1

1.2) Foundry Casting .................................................................................................... 2

1.3) Specifications......................................................................................................... 3

1.3.1) Upper Die ............................................................................................... 3

1.3.2) Blank Holder........................................................................................... 4

1.3.3) Lower Die Punch .................................................................................... 4

1.4) Diagrammatic View of Model ............................................................................... 5

1.5) Working Principle...................................................................................................6

1.6) Problem Description .............................................................................................. 7

1.7) Tools used for Modeling and FEA ........................................................................ 8

1.7.1) Pro/ENGINEER .................................................................................... 8

1.7.2) MECHANICA ....................................................................................... 8


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Chapter

2. DESIGN USING Pro/ENGINEER ........................................................................ 10

2.1) Introduction ......................................................................................................... 10

2.2) General Terms ..................................................................................................... 11

2.3) Geometric Terms ................................................................................................. 12

2.4) Pro/ENGINEER Versions ................................................................................... 13

2.5) Design of Sheet Metal Die Parts.......................................................................... 14

2.5.1) Design of Upper Die ............................................................................ 14

2.5.2) Design of Blank Holder ....................................................................... 15

2.5.3) Design of Lower Die Punch ................................................................. 16

2.5.4) Design of Pattern Surface Part .............................................................. 17

2.5.5) Design of Upper Die Surface Part ........................................................ 18

2.6) Design of Sheet Metal Die Assembly ................................................................. 19

2.6.1) Assembling Upper Die and Upper Die Surface.................................... 19

2.6.2) Assembling Lower Die and Pattern Surface ......................................... 20

2.6.3) Die Assembly ....................................................................................... 21

2.7) Sheet Metal Die Exploded View ......................................................................... 22

Chapter

3. FEA ANALYSIS USING MECHANICA ............................................................. 23

3.1) Introduction ......................................................................................................... 23


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3.2) Problems Solved Using MECHANICA .............................................................. 23

3.3) Steps in Preparing an FEA Model ....................................................................... 24

3.4) Setting Up the Model in MECHANICA ............................................................. 26

3.4.1) Running MECHANICA ....................................................................... 26

3.4.2) Material Specification........................................................................... 27

3.4.3) Applying the Pressure Load ................................................................. 29

3.4.4) Defining Displacement Constraints ..................................................... 30

3.4.5) Defining Planar Constraint ................................................................... 31

3.4.6) Running Basic Static Analysis ............................................................. 32

3.4.7) Running Auto Gem ............................................................................... 34

3.4.8) MECHANICA Convergency .................................................................35

3.4.8) Setting up Optimum Design Study ....................................................... 46

Chapter

4. RESULTS ................................................................................................................48

4.1) Results from Basic Static Analysis .......................................................................48

4.2) Results from Optimum Design Study Analysis ................................................... 48

4.3) Basic Static Vs Optimization-Deflections ............................................................49

4.4) Basic Static Vs Optimization-Stresses ................................................................ 50

4.5) Basic Static Vs Optimization-Principal Strain .................................................... 52

4.6) Dimensional Changes in Die Assembly ...............................................................54


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4.7) Graphical Results ................................................................................................. 55

4.8) Optimized Auto Gem............................................................................................57

CHAPTER

4. FEATURE WORK .................................................................................................58

References ...................................................................................................................59


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LIST OF FIGURES

1. Figure 1.4-1 Sheet Metal Die Assembly........................................ 5

2. Figure 2.5-1 Upper Die............................................................. 14

3. Figure 2.5-2 Blank Holder........................................................ 15

4. Figure 2.5-3 Lower Die Punch.................................................. 16

5. Figure 2.5-4 Pattern Surface..................................................... 17

6. Figure 2.5-5 Upper Die Surface Part........................................ 18

7. Figure 2.6-1 Upper Die Assembly............................................. 19

8. Figure 2.6-2 Lower Die Assembly............................................ 20

9. Figure 2.6-3 Die Assembly........................................................ 21

10. Figure 2.7-1 Exploded View..................................................... 22

11. Figure 3.3-1 Steps for FEA...................................................... 25

12. Figure 3.4-1 Model Setup......................................................... 26

13. Figure 3.4-2 Material Definition................................................. 27

14. Figure 3.4-3 Assigning Material................................................. 28

15. Figure 3.4-4 Assigning Load..................................................... 29

16. Figure 3.4-5 Assigning Displacement Constraint........................ 30

17. Figure 3.4-6 Assigning Planar Constraint................................... 31

18. Figure 3.4-7 Setting up Basic Analysis....................................... 32


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19. Figure 3.4-8 Running Basic Analysis.......................................... 33

20. Figure 3.4-9 Running Auto Gem................................................. 34

21. Figure 3.4-10 Setting up Convergence.......................................... 35

22. Figure 3.4-11 Running Multi-pass Adaptive Test........................... 36

23. Figure 3.4-12 Setting Up Optimum Design Study.......................... 46

24. Figure 3.4-13 Running Optimum Design Study............................ 47

25. Figure 4.3-1 Deflections in Fringe Display Type.......................... 49

26. Figure 4.4-1 Stresses in Fringe Display Type.............................. 50

27. Figure 4.4-2 Maximum Stress Locations..................................... 51

28. Figure 4.5-1 Principal Strain in Fringe Display Type................... 52

29. Figure 4.5-2 Maximum Principal Strain Locations....................... 53

30. Figure 4.6-1 Dimensional Changes in Die Assembly................... 54

31. Figure 4.7-1 Graphical Area Considered..................................... 55

32. Figure 4.7-2 Deflections in Graphical Display Type..................... 56

33. Figure 4.8-1 Auto-Gem after Optimization................................... 57


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Chapter 1

INTRODUCTION AND BACKGROUND

1.1) Introduction:

In recent years the development of more and more cars with different external appearance

has become a remarkable trend in the automotive industry. As another trend the

increasing use of high and ultrahigh strength steel grades for bodies should be mentioned.

Both trends generate higher costs for individual tools that are traditionally made as stiff

as possible. Sheet Metal Dies, one of the tools used in making sheet metal parts for

automobile industry account 35% of total cost of a vehicle program. The construction

cost of these dies is used as benchmark by the automotive companies to evaluate the cost

of any new vehicle program and also to determine where they stand compared to their

competitions.

These sheet metal dies are designed accordingly for a particular company based on the

internal process, safety guidelines and press allocations. As these sheet metal dies are

operated regularly and subjected to various load conditions in their lifecycle and hence

the die should provide sufficient safety factor to prevent any structural failure of dies and

also should compensate the elastic deformations or deflections. The die breakage during

production can cause a complete halt of production which stops the production cycle in

an industry. Due to this extreme importance of these dies to be safe during the entire

production cycle the die design standards are made very traditional and dies thus made of

heavy weight. Due to this heavy structure of the dies, the cost of raw material,


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construction costs, operating costs are huge. But, now the availability of finite analysis

can be performed on these dies for various line die operations and opportunities to

explore savings in weight can be explored to reduce the structural and operating costs.

The various safety measures can be analyzed by thorough finite element analysis and also

root cause of the breakage problems can be fixed in a more efficient manner.

The two key requirements of tool design are meeting functional performances and

achieving greater manufacturing reliability. There are number of important areas of the

die that can be standardized and helps to reduce the manufacturing cost and production

time. This applies more intended to pattern making activities that are time consuming,

expensive and more human errors.

1.2) FOUNDRY CASTING:

The old fashioned and manual approach to foundry pattern making has number of

drawbacks like

Dimensional accuracy cannot be assured Manufacturing times are too long Excess material on critical areas of the casting can result in poor quality and a

weaker casting

Poor quality pattern joints are a potential source of casting weakness and thuscompromise safety.


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The above errors can be overcome by using standard pieces and NC machining of

working surfaces, but designing the automated sheet metal casting dies are more helpful

compared to this old fashioned pattern making.

1.3) SPECIFICATIONS:

The sheet metal die assembly mainly consists of three parts. They are

1.3.1) UPPER DIE:Upper die is the upper portion of a die set that corresponds with

the lower die via blank holder and move down onto the work piece. Upper die is of

rectangular shape with hallowing centered area. All the four side of the upper die is

composed of rectangular ribs which make the force applied to be distributed evenly.

The upper area of the die is divided with uniform rectangular ribs which are useful to

place press slider firmly. The bottom part of the die consists of ten equally

dimensioned pins which lie on blank holder pins. The dimensions of the upper die

and material specifications are as follows.

Length = 1650 mm Width = 1170 mm Height = 485 mm Upper ribs = 230 * 200 mm Side ribs = 460 * 200 mm Material Used = High strength Steel Density of Steel = 7.82708e-09 ton/mm^3


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Poissons ratio = 0.27 Youngs Modulas = 19.98 Mpa1.3.2) BLANK HOLDER: The Blank holder is used to prevent the edge of a sheet

metal blank from wrinkling during deep drawing operations. Blank holder is

of rectangular in shape with rectangular ribs on bottom part. It has cushioned

pins on the bottom which lie on punch die. The dimensions and material

specification is as follows.

Length = 1650 mm Width = 1215 mm Height = 220 mm Bottom ribs = 215 * 155 mm Material Used = High strength Steel

Density of Steel = 7.82708e-09 ton/mm^3

Poissons ratio = 0.27 Youngs Modulas = 19.98 Mpa.1.3.3) LOWER DIE PUNCH: Punch die is bottom part of the die assembly. It is the

fixed part in die assembly and it is firmly fixed at the bottom. Punch die is of

rectangular in shape with rectangular ribs on bottom and on upper part a

pattern model of required shape is firmly fixed. The dimensions and material

specification is as follows.

Length = 1650 mm


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Width = 1215 mm Height = 160 mm Bottom ribs = 265 * 265 mm Material Used = High strength Steel Density of Steel = 7.82708e-09 ton/mm^3 Poissons ratio = 0.27 Youngs Modulas = 19.98 Mpa.

1.4) DIAGRAMATIC VIEW OF MODEL:

UPPERDIE

PINS

BLANKHOLDER

LOWERDIE

Figure 1.4-1: SHEET METAL DIE ASSEMBLY


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1.5) WORKING PRINCIPLE:

Sheet Metal die casting is one of the most advance technique used in automobile

industry. This die casting assembly mainly consists of upper die, punch, blank holder,

cushion pins, guided pins and press slider. The upper die is fixed to the press slider and

punch is fixed to the ground. The blank holder, which is supported by the cushion pins,

holds the blank sheet and controls the drawing between the upper die and the punch. The

1500 ton press/die has 900 tons of drawing force by the punch and 80 tons of blank

holding force deliverable to the blank holder. The press slider transfers the drawing load

to the upper die and the cushion pins delivers the holding load to the blank holder. The

load is applied firmly until the upper die guided pins completely moves on to the blank

holder pins and once when both pins contacts together the drawing load applied is

gradually reduced. As the drawing process proceeds, the blank sheet in the blank holder

gets the shape as the pattern on the punch. In order to count for the load differences

transferred among upper die, punch and blank holder the contact boundary conditions i.e.

the pins height both on upper die and blank holder must be adjusted accordingly. Then

the blank sheet with required shape is removed and new sheet is loaded and the process

will repeat again.


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1.6) PROBLEM DESCRIPTION:

Among the main components of sheet metal die, the role of blank holder in the generation

of the restraining forces acting on the metal sheet during the deep drawing is considered.

It is well known fact that the choice of restraining force distribution is a key point in

designing the sheet metal die. These restraining forces are mainly controlled by the height

and diameter of guided pins on upper die and blank holder. Due to the load of press

slider, large deformations are caused and big stresses are concentrated in the upper die

and blank holder. The evolution of the blank holder and upper die modeling in the finite

element simulation of the drawing process is reviewed and the need of deformable model

of the blank holder and upper die to obtain process realistic simulation is pointed out. The

factors that affect the actual restraining force distribution are briefly analyzed and also

identifying control factors like overall deformations of die.


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1.7) TOOLS USED FOR MODELING AND FEA:

1.7.1) PRO/ENGINEER

Pro/ENGINEER mechanical design software from Parametric Technology

Corporation is used for creating 3D computer models of mechanical parts and

assemblies and the creation of 2D drawings for the models. Like any software it is

continually being developed to include new functionality. Its main aimis to outline

the scope of capabilities to give an overview rather than giving specific details on

the individual functionality of the product. Pro/Engineer is a piece of software

that falls within the category of CAD/CAM/CAE and site alongside other similar

products currently on the market. Pro/Engineer is a feature based modeling

architecture incorporated into a single database philosophy with advanced rule

based design capabilities. The capabilities of the product can be split into the three

main heading of Engineering Design, Analysis and Manufacturing. This data is

then documented in a standard 2D production drawing or the 3D drawing standard

ASME Y14.41-2003.

1.7.2) MECHANICA

Finite Element Analysis (FEA), also known as Finite Element Method (FEM), is

one of the most important tools added to mechanical design engineers toolkit in

recent years. Because of very powerful desktop workstations, FEA is now

available at a practical cost to virtually all engineers and designers.


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MECHANICA is one of the many commercial systems that are available.

MECHANICA is an integrated option in Pro/ENGINEER and is actually

composed of two programs which are structural and thermal. In present paper the

structural MECHANICA analysis is used for analyzing the die assembly at

several boundary conditions.


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Chapter 2

DESIGN USING Pro | ENGINEER

2.1) INTRODUCTION:

Pro | ENGINEER is one of the mechanical design software from Parametric Technology

Corporation which include creating 3D computer models of mechanical parts and

assemblies, and creation of 2D drawings for the models. This CAD software runs on

Microsoft Windows and UNIX platforms. Like any other software it is continually being

developed to include much new functionality. Pro/Engineer is a piece of software that

falls within the category of CAD/CAM/CAE and site other similar products currently on

the market. Pro/Engineer is a feature based modeling architecture incorporated into a

single database philosophy with advanced rule based design capabilities. The capabilities

of the product can be split into the three main heading of Engineering Design, Analysis

and Manufacturing

It is different from many other CAD tools by the following way.

Pro/ENGINEER is a not a drafting system instead it is a three dimensional solidmodeling system.

The 3D solid model is the engineering document of record, not the drawing. It is not based on X, Y and Z axis system. Layers and colors are not related. Every time we save an object, it creates a new version of the object.


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Before we use Pro/ENGINEER we need to know some of the terminology and concepts

used.

2.2) GENERAL TERMS:

a) Parametric: Parameters are modified to affect changes in the model. Adimension is a simple example of a parameter.

b) Feature Based: It is a set of instructions that tells the system how to creategeometry. Features are created in a logical order to convey design intent to

the system.

c) Modeling: Creating computer images coupled with geometric informationdefining a part or assembly.

d) Model: It is the engineering document of record and contains all designinformation including dimension, tolerances, materials, notes, symbols,

and manufacturing data. Models are two types i.e. part model and

assembly model.

e) Sketch: Part models are a collection of sketched features. These sketchesdefine geometric design intent as the model is created.

f) Working Directory: It is the directory where all Pro/ENGINEER files aresaved.


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2.3) GEOMETRIC TERMS:

a) Axis: It is the center of a cylinder or other revolved feature. It is used ondrawings as centerlines and also to indicate symmetry on drawings.

b) Blend: A feature that is created by blending from one shape to another.c) Datum Plane: It is the foundation of all models. These are non-solid,

orthogonal, planar surfaces, and are used to create and orient the models

solid geometry. It includes three default datum planes which are Top,

Right and Front.

d) Edge: It is intersection of two part surfaces.e) Extrude: It is used to create a sketch normal to a plane.f) Pattern: It is used to create a series of similar features.g) Plane: It is usually a flat object. Usually a datum plane but also can be a

solid part face or surface.

h) Point: It can be created on surfaces, at vertices, etc.i) Revolve: This feature is used to create revolving sketch about a centerline.j) Round: It is a fillet radius on a solid part. It can be constant or variable.k) Sweep: It is a feature created by a sketch that follows a path or trajectory.l) Vertex: It is intersection of three edges.


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2.4) Pro/ENGINEER VERSIONS:

Name/Version Build Number Date

Pro/ENGINEER (Autofact1987premier) R1.01 1987

Pro/ENGINEER R 8.0 1991













Pro/ENGINEER R 2000i 1999

Pro/ENGINEER R 2000i2 2000

Pro/ENGINEER R 2001 2001

Pro/ENGINEER Wildfire R 1.0 2002




Pro/ENGINEER Wildfire R 5.0 2009Creo Elements/Pro R 5.0 (as of M065) 2010

The version used in this paper is Pro/ENGINEER Wildfire 3.0 2006.


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2.5) DESIGN OF SHEET METAL DIE PARTS:

2.5.1) DESIGN OF UPPER DIE:In order to design this in pro/ENGINEER feature used

are Extrusion, sketch and planes.

Figure 2.5-1: UPPER DIE


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2.5.3) DESIGN OF LOWER DIE PUNCH: In order to design this in pro/ENGINEER

features used are Extrusion, Pattern, Hole and Chamfer.

Figure 2.5-3: LOWER DIE PUNCH


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2.5.4) DESIGN OF PATTERN SURFACE PART: In order to design this in

Pro/ENGINEER an important special feature is used. It is drawn by following reverse

engineering principle i.e. import feature. It is imported from other CAD software.

Figure 2.5-4: PATTERN SURFACE


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2.5.5) DESIGN OF UPPER DIE SURFACE PART: In order to design this in

Pro/ENGINEER an important special feature is used. It is drawn by following reverse

engineering principle i.e. import feature. It is imported from other CAD software

Figure 2.5-5: UPPER DIE SURFACE PART


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2.6 DESIGN OF SHEET METAL DIE ASSEMBLY:In order to create the assembly of

sheet metal die, initially we have to assembly the upper die and upper die surface parts

and lower die and pattern surface. Hence it is assembled in the following way.

2.6.1) ASSEMBLING UPPER DIE AND UPPER DIE SURFACE: In order to assemble

these two parts in pro / ENGINEER the assembly features like Mate and Align are used.

Figure 2.6-1: UPPER DIE ASSEMBLY


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2.6.2) ASSEMBLING LOWER DIE AND PATTERN SURFACE: In order to assemble

these two parts in pro / ENGINEER the assembly features like Mate and Align are used.

Figure 2.6-2: LOWER DIE ASSEMBLY


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2.6.3) DIE ASSEMBLY: Now from the models which we have i.e. Upper die assembly,

Lower die assembly and Blank holder the final die assembly is made. Lower die is kept

in bottom position and upon that Blank holder is perfectly aligned and on the blank

holder Upper die assembly is made to align perfectly so that the final assembly is made.

Figure 2.6-3: DIE ASSEMBLY


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2.7) SHEET METAL DIE EXPLODED VIEW:Pro / ENGINEER is a perfect tool where

we can see the all parts in exploded view and also we come to know which parts are

aligned or mate together.

Figure 2.7-1: EXPLODED VIEW


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Chapter 3

FEA ANALYSIS USING MECHANICA

3.1 INTRODUCTION:

MECHANICA is one of the integrated Finite Element Analysis tool in Pro/ENGINEER.

This software is one of the many commercial systems that are available. Mechanica is

one of the unique Finite Element Analysis tool in many ways. When operating in

integrated mode with Pro/ENGINEER, MECHANICA is actually composed of two

programs i.e. Structure and Thermal. Structural analysis is used for linear static stress

analysis, modal analysis, buckling analysis and large deformation analysis (non-

linear).Thermal analysis is used for steady state and transient thermal analysis. In present

paper the structural analysis is used for sheet metal die assembly.

3.2 PROBLEMS SOLVED USING MECHANICA:

The problems that are solved by using structure analysis are simple analysis, a parametric

study called a sensitivity analysis, and a design optimization.

a) ANALYSIS: A model is defined by some geometry by using Pro/ENGINEERand this model is transferred into MECHANICA. The material properties are

specified, loads and constraints are applied, and one of several different types of

analysis can be run on the model.

b) SENSITIVITY STUDY: If we need to find out the overall effect on the solutionby varying one or more design parameters, MECHANICA is the perfect tool for

this case. We can do this by performing a number of similar analyses, and


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changing the geometry of the model between each analysis. It has an automated

routine which allows specifying the parameter to be varied, and the overall range.

Then it automatically performs all the modifications to the model and calculates

results for the intermediate values of the design parameters.

c) DESIGN OPTIMIZATION: For a model by designating some design variablesfrom some geometric parameters, we can make MECHANICA to find the

combination of values of the design variables that will minimize some objective

function like total mass, some design constraints like maximum stress or

deflections etc and will find the optimum set of design variables automatically.

3.3 STEPS IN PREPARING AN FEA MODEL:

After importing the model into MECHANICA, there are several steps to be followed in

order to get perfect solutions. The steps are as follows.

Recognize the model type Specifying the material properties, applied loads and model constraints Running Auto Gem to produce finite element mesh Solving the linear equations using solver Compute items of interest from the solution variables Display the results both graphically and Fringe mode.

The overall procedure can be explained by the following figure.


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Figure 3.3-1: STEPS FOR FEA

CREATEGEOMETRY

USING Pro/E

MODEL TYPE

RUNNING FINITE ELEMENT

MESH-AUTOGEM

REVIEW

COMPUTE/DISPLAY RESULTS OF

INTEREST

SOLVING LINEAR EQUATIONS

SIMULATION PARAMETERS

-MATERIAL PROPERTIES

-MODEL CONSTRAINTS

-APPLIED LOADS


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3.4) SETTING UP THE MODEL IN MECHANICA: After drawing the model in

Pro/ENGINEER we are ready to launch the MECHANICA.

3.4.1) RUNNING MECHANICA:Mechanica is an integrated tool in Pro/ENGINEER. In

order to run Mechanica, from pull down menu go to Applications and then Mechanica. It

pops up a window saying the units which are used by the pro/ENGINEER. Then a

window pops up which ask us to select model type and the analysis type. So, select solid

as model type and structural analysis for analysis type.

Figure 3.4-1: MODEL SETUP


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3.4.2) MATERIAL SPECIFICATION: Now, we have to assign the material to the parts

of sheet metal die assembly. It is a two-step process i.e. material definition and assigning

it to the part. So, in present paper the defined material is steel and it is assigned to all

parts i.e. for Upper die, Blank holder and Lower die. The following figures show the

defining material and assign materials respectively.

Figure 3.4-2: MATERIAL DEFINITION


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Figure 3.4-3: ASSIGNING MATERIAL


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3.4.3) APPLYING THE PRESSURE LOAD:Now a pressure load of 1000 lbm/in sec^2

is uniformly applied on the upper die. Now the model will appear similar to following

figure.

Figure 3.4-4: ASSIGNING LOAD


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3.4.4) DEFINING DISPLACEMENT CONSTRAINTS: The Lower die part in sheet

metal die assembly is fixed to ground. In order to define that in MECHANICA we have

to assign zero displacement constraint to lower portion of Lower die. Now the model will

appear similar to following figure.

Figure 3.4-5: ASSIGNING DISPLACEMENT CONSTRAINT


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3.4.5) DEFINING PLANAR CONSTRAINT: In order to distribute uniform load on

upper die by the pressure applied we have to define a planar constraint. This can be

shown in following figure.

Figure 3.4-6: ASSIGNING PLANAR CONSTRAINT


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3.4.6) RUNNING BASIC STATIC ANALYSIS:Now we have to set up basic analysis

from the pull down menu by selecting Analyses and Design studies. Initially the analysis

is run using Quick check and it detects any errors in the model. Once we pass through

this step the analysis is runes again by single and multi-pass adaptive methods. The

setting up of basic analysis is shown in following figures.

Figure 3.4-7: SETTING UP BASIC ANALYSIS


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Figure 3.4-8: RUNNING BASIC ANALYSIS


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3.4.7) RUNNING AUTO GEM: The finite element analysis mesh is created by using

automatic mesh generator, Auto Gem in MECHANICA. After running this the main

items which we can know are number of elements created, convergence on pass,

maximum Von Misses stress, maximum displacement, CPU time and elapsed time. These

can be seen in following figure.

Figure 3.4-9: RUNNING AUTO GEM


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3.4.8) MECHANICA CONVERGENCY: In order to converge the mesh size in

MECHANICA we have to run the basic static analysis in three ways i.e. Quick check,

Single pass adaptive and Multi pass adaptive. Quick check is done in order to check the

die assembly is properly constrained or not. Once the quick check is done then it is run in

Single pass Adaptive test in order to ensure that we get the basic deflections, stress and

strain results. Then we have to run again with Multi Pass Adaptive test by setting

maximum polynomial order to 9 and percentage of convergence to 5.Then the Auto Gem

is runned again and it calculates several equations and we get final mesh which is

converged and ready to set for the optimum design conditions.

Figure 3.4-10: SETTING UP CONVERGENCE


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Figure 3.4-11: RUNNING MULTI-PASS ADAPTIVE TEST

Summary of Multi-Pass Adaptive test from MECHANICA program:

Mechanica Structure Version L-03-38:spg

Summary for Design Study "basic_static"

Mon Nov 15, 2010 12:21:50

------------------------------------------------------------

Run Settings

Memory allocation for block solver: 128.0

Parallel Processing Status

Parallel task limit for current run:


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Parallel task limit for current platform: 64

Number of processors detected automatically: 2

Checking the model before creating elements...

These checks take into account the fact that Auto GEM will automatically create

elements in volumes with material properties, on surfaces with shell properties, and on

curves with beam section properties. Generate elements automatically.

Checking the model after creating elements...

No errors were found in the model.

Mechanica Structure Model Summary

Principal System of Units: Inch lbm Second (Pro/E Default)

Length: in

Mass: lbm

Time: sec

Temperature: F

Model Type: Three Dimensional

Points: 5640

Edges: 28786

Faces: 40676

Springs: 0

Masses: 0

Beams: 0


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Shells: 0

Solids: 1765

Elements: 17650

------------------------------------------------------------Standard Design Study

Static Analysis "basic_static":

Convergence Method: Multiple-Pass Adaptive

Plotting Grid: 4

Convergence Loop Log: (12:23:00)

>> Pass 1


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Elapsed Time (sec): 108.64

CPU Time (sec): 88.34

Memory Usage (kb): 418453

Wrk Dir Dsk Usage (kb): 139264

>> Pass 2


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>> Pass 3 > Pass 4


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Elements Not Converged: 2004

Edges Not Converged: 0

Local Disp/Energy Index: 72.9%

Global RMS Stress Index: 25.0%

Resource Check (12:33:33)





>> Pass 6


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>> Pass 7


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> Pass 8 > Pass 9


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Maximum Edge Order: 9

Solving Equations (14:10:25)

Post-Processing Solution (14:35:20)

Calculating Disp and Stress Results (14:47:12)

Checking Convergence (14:57:35)

Elements Not Converged: 0

Edges Not Converged: 0

Local Disp/Energy Index: 20.9%

Global RMS Stress Index: 7.5%






Hence from above all passes i.e. from 1 to 9 all elements are converged and then we run

optimum design analysis.


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3.4.8) SETTING UP OPTIMUM DESIGN STUDY:Now, the conditions which are

required to be satisfied in the design are given in optimum design study. The conditions

given are low overall displacement and the height to of pins on blank holder. The setting

up and running the optimum design study is shown in following figures respectively.

Figure 3.4-12: SETTING UP OPTIMUM DESIGN STUDY


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Figure 3.4-13: RUNNING OPTIMUM DESIGN STUDY


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Chapter 4

RESULTS

4.1) RESULTS FROM BASIC STATIC ANALYSIS:

Maximum Deflections:1.667in Maximum Stress:324.3Mpa Maximum Strain:0.134 Height of Pin:2.9526in Height of upperdie:21.2598in

4.2) RESULTS FROM OPTIMUM DESIGN STUDY ANALYSIS:

Maximum Deflections:1.922e^-03in Maximum Stress:293.2Mpa Maximum Strain:1.294e -04 Height of Pin:2.899in Height of upperdie:20.99in

These results can also be seen in graphical and fringe views by MECHANCIA tool.

These are as follows.


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4.3) BASIC STATIC Vs OPTIMIZATION-DEFLECTIONS:

Figure 4.3-1: DEFLECTIONS IN FRINGE DISPLAY TYPE


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4.4) BASIC STATIC Vs OPTIMIZATION-STRESSES:

Figure 4.4-1: STRESSES IN FRINGE DISPLAY TYPE


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4.5) BASIC STATIC Vs OPTIMIZATION-PRINCIPAL STRAIN:

Figure 4.5-1: PRINCIPAL STRAIN IN FRINGE DISPLAY TYPE


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Figure 4.5-2: MAXIMUM PRINCIPAL STRAIN LOCATIONS

Maximum Strain-Optimization, Basic Static


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4.6) DIMENSIONAL CHANGES IN DIE ASSEMBLY:After running optimum design

study we get the dimensional changes in height of pins and upper die and these can be

shown in following figure.

Figure 4.6-1: DIMENSIONAL CHANGES IN DIE ASSEMBLY


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4.7) GRAPHICAL RESULTS:The graphical results in MECHANICA can be known by

considering certain area in sheet metal die assembly. In present paper the top surface of

the blank holder is considered one of the areas where we interested to see graphical

results. The area we considered can be shown in following figure.

Figure 4.7-1: GRAPHICAL AREA CONSIDERED

The deflections at this area for basic static analysis and optimization can be viewed in

following figure.


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Figure 4.7-2: DEFLECTIONS IN GRAPHICAL DISPLAY TYPE


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4.8) OPTIMIZED AUTO GEM: After optimization the auto gem is runned again and the

result can be seen in following figure.

Figure 4.8-1: AUTO-GEM AFTER OPTIMIZATION


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Chapter 4

FEATURE WORK

Modification in designing to make it more robust. Finite Element Analysis of complete sheet metal die assembly including blank

sheet and pattern.

Vibration Analysis. Using any other FEA tool in getting more appropriate results.


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REFERENCES

1. Pro | ENGINEER WILDFIRE 3.0 BASIC DESIGNSteven G.Smith

2. Pro | ENGINEER WILDFIRE 3.0 MECHANICA TUTORIALRoger Toogood, SDC PUBLICATIONS

3. www.wikipedia.com
http://www.wikipedia.com/http://www.wikipedia.com/http://www.wikipedia.com/

final soft copy

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