Evaluation of the structural design of new liquid containers

Rochester Institute of Technology

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Theses

Thesis/Dissertation Collections

2001

Evaluation of the structural design of new liquid

containers

Jadranka Mandic

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EVALUATION

OF

THE STRUCTURAL

DESIGN

OF NEW LIQUID CONTAINERS

by

Jadranka Mandic

A Thesis

Submitted

to

the Department

of

Packaging

Science

of

Rochester Institute

of

Technology

Executive

Leader Program

2001

Department of Packaging Science

of Rochester Institute of Technology

Rochester, New York

CERTIFICATE OF APPROVAL

M.S. Degree

The M.S. degree thesis of Jadranka Mandie

has been examined and approved

by the thesis committee as satisfactory

for the thesis requirements for the

Master of Science degree

Dan Goodwin

CarI de Winter

Acknowledgements

[would like to thankallwhohelpedme withtheprofessionaladvice, as well as those who gave me support and _{understanding}

during

preparation and realization_ofthisproject.

Iam thankful toMr. Miso Rabatic for confidence hegave me, to work out

his

patent. I am _very grateful to prof. dr. Mladen

Sercer,

Polymer

Department,

for

his

motivation in the _{development of}this project, Iowe a

large

part _{of my} gratitude to prof. dr. Bojan

Jerbic,

Igor Cerin and personnel _{of CAD Lab} allfrom

Faculty

_{of Mechanical}

Engineering

and Naval Architecture_ofthe

University

_ofZagreb.

Prof.

dr.

Vjera

Krstelj

deserves the most _ofmy appreciation andgratitude for herencouragementand support.

- Thank

EVALUATION

OF

THE

STRUCTURAL

DESIGN

OF NEW LIQUID

CONTAINERS

by

Jadranka Man

die

March 2001

ABSTRACT

GECOS (Global

Eco

System)

bottle

with an additional _{using quality,} represents

new

idea,

which

is

patented

innovation.

Basicbottleassignment ofGECOS bottle

is for storage andtransportation ofthe liquids

from

food

domain,

such as _water,

juices or milk. Additional using quality of GECOS bottles comes from unique

construction,as well astheir closures. _{When GECOS bottle is empty it} can serve

as universal

building

elements, which are connected

by

closures as _connecting elements into new three-dimensional structures. In such a _{way, the} bottles are

easier to be

kept,

collected or used in a game as

didactic

and creative tool like

building

blocks.

In this thesis basic idea on GECOS

bottle design is

worked out

from

structural

design point of _{view, using} analytical approach. Supported

by

CAD (Computer

Aided

Design)

system, 3D model of GECOS bottle was created and translated into FEA (Finite Element

Analysis)

model. With quantified factors which are

necessary for structural design analysis the calculation ofstress and

deformation

TABLE

OF

CONTENTS

1.

INTRODUCTION

1

2. INVENTION

ESSENCE

2

3.

PRODUCT

DEVELOPMENT

PROCESS

4

3.1. CONCEPT

DEVELOPING

7

3.1.1.

FUNCTIONAL REQUIREMENTS

8

3.1.2.

MATERIAL

SELECTION

10

3.1.3. PROCESS OF PRODUCTION

12

3.1.4. CONCEPTUAL DESIGN

13

3.2. STRUCTURAL DESIGN

19

3.2.1. DESIGN METHODOLOGY

20

3.2.2. QUANTIFYING THE DESIGN PROBLEM

22

3.2.2.1. Part geometry

23

3.2.2.2.

Generating

the mesh

24

3.2.2.3. Material

mechanical properties

25

3.2.2.4.

Boundary

conditions

26

3.2.2.5.

Loading

conditions 27

3.2.3. RESULTS

30

[image:7.520.52.471.55.589.2]

LIST OF FIGURES

Fig. 1. DrawingsofGECOS bottle from thepatentapplication 3

Fig. 2. Flowchartofproductdevelopmentprocess 4

Fig. 3. Flowchart oftechnological developmentoftheproduct 5

Fig. 4. Flowchartofthesis_methodology 6

Fig. 5. Technologicalrequirements 7

Fig. 6. Frontview ofthree partsquareGECOS bottle 15

Fig. 7. Frontview ofthreepartsquareGECOS bottle 15

Fig. 8. Crosssection andbottomview of squareGECOS bottle 16

Fig. 9.

Top

view ofsquareGECOS bottle 16

Fig. 10. Closure 16

Fig. 11. 3D GECOS bottlemodel (printscreen_{from l-DEAS software)} 17

Fig. 12. 3D GECOS bottlemodel with closure (printscreen_{from l-DEAS software)} 17

Fig. 13. Wireframeof3DGECOS bottlemodel(printscreen_{from l-DEAS software)} 18

Fig. 14. Simplified 3D GECOS bottlemodel prepared_{for meshing} 23

Fig. 15. Finalelement model ofGECOS bottle (printscreen_{from l-DEAS software)} 24

Fig. 16. Idealizedconditions of supportedbottomofGECOS bottle 26

Fig. 17. Report from CAPE99 (bestsolution underNo.

1.)

28

Fig. 18. Idealized

loading

conditions 29

Fig. 19. Resultsofstresson MODEL A 30

Fig.20. Resultsof stress on

top

ofMODEL A 31

Fig. 21. Resultsof stress onbottomofMODEL A 31

Fig. 22. Resultsof stress onMODEL B 32

Fig. 23. Resultsof stress on

top

ofMODEL B 33

Fig. 24. Resultsofstress on bottomofMODEL B 33

Fig. 25. ResultsofdisplacementonMODELA 34

Fig. 26. Resultsofdisplacementon

top

ofMODEL A 35

Fig.27. ResultsofdisplacementonbottomofMODEL A 35

Fig. 28. Results ofdisplacementonMODEL B 36

Fig. 29. Results ofdisplacementon

top

ofMODEL B 37

Fig. 30. ResultsofdisplacementonbottomofMODEL B 37

LIST

OF

TABLES

Table 1.Averagevalues of material mechanicalproperties 25

Table 2. Solutionreport 28

1. INTRODUCTION

Confronted with the

fact,

that the containers

for

liquids are

daily

produced and

thrown _away

in

enormous _quantities, and that some ofthem have no _{using quality} after

being

emptied while the construction of the same one aggravates the disposal and

recycling, the idea has appeared

by

which _{to the containers,} aftertheir basic use, another

using quality isadded.

The

former

_{liquid packaging} ways, particularly in the food

industry,

for example

standard so-called PET containers,

tetrapack,

glass

bottles,

tins and other similar

containers,

have

the samemain

drawback

-after

being

_emptied,

they

were most

frequently

beenthrown_{away into}refuse. The ecological standards ofthedevelopedcountries "force"

the users of used containers to dispose the same one _{additionally into} special disposal

places assigned for _{that purpose,} in order to be recycled. Used containers are disposed

individually

or in smaller _{quantities, and,}

inherently,

they

are of no interest to the

consumer,butadditional worry.

By

this invention - GECOS (Global Eco

System)

bottle just these drawbacks are

eliminated. GECOS bottle is container for

liquids,

which on its _surface, have additional

parts, which enable the _connecting oftwo or more GECOS bottlestogether in a_way,that three-dimensional structures can be created. These structures enable easier

transport,

storage, as well as the _playing and amusement for children. Such greater _quantity, once

gathered

together,

"justifies"the transporttoeven more distanced disposalplaces,

because

additional plastic containers

-sacks and the

like,

for

taking

_away the _{empty GECOS}

bottles,

are not necessary.

Simply,

the entire block of _{empty GECOS}

bottles

_{is very}

monolithic, lightand simplefortransportation.

With different _geometry and volumes of this bottles it is possible to make

combinations ofthree-dimensional structures. It can be used in children's _play as

didactic

and creative

toy

as

building

blocks.

This invention is product of _{Mr. Miso Rabatic. The State Intellectual}

Property

Office receivedthe patent application with number

P20000021A,

andPatent

Cooperation

Treaty

(PCT/HR00/00001). Since there is a great

interest for

such

invention,

the goal of

2.

INVENTION ESSENCE

The proposed technical solution offers an additional _{using quality} ofused bottles.

The

invention

_novelty

is,

that it combines _existing advantages ofthe plastic bottles with special construction ofthe

bottle

and

belonging

closure.

The GECOS

bottles

are three

dimensional

building

elements of special surface

topology. The invention in its essence consistsofthebottle construction, which in its sides

has

sunk _{connecting places,} shaped to accept the closure as the _connecting element. In

order to ensure a compact _coupling

by

_{the closure, the} closure outer diameter is greater

than the diameter ofthe _connecting place in the bottle sunkage, it is toothed with small

elastic teethwhich enablethe_{necessary deformation. The} closure is constructed ina_way,

that in the middle it has a horizontal partition wall and _only on one side a thread. The

closureensureinter connectingoftwo GECOS bottles

by

pressing into connectingplace of

onebottlewith pressing-in into connectingplace ofotherbottle. Measure"a"

defines dimension

oftheside ofGECOS bottle

basic

shape

-the cube,

as well as distance betweenthe centers ofthe _connecting places onthe

bottle,

in order to

ensure the _{compatibility in} their

inter-connecting,

regardless ofthe size and shape of all bottleswhich come as resultfromthisinvention.

The drawings in patent application is _offering one, two and three part square

GECOS bottle. Threepart square GECOS bottle has been takeninto consideration. Bottle

VIEWD 1

CROSS SECTION K-K

L CROSSSECTION L-L

i

,

VIEWE _{CROSS SECTION M-M}

}f\

\

V

J

[image:10.520.83.473.68.356.2]

3.

PRODUCT

DEVELOPMENT

PROCESS

The

idea

or

innovation

have

to pass the product development process to become

commercialproduct.

i

1

^.

Marketing

Analyze ^ Requirements for ^ *" Development Evaluation of Product Development A ?

I

Idea (problem assignment) >

Planning

i_

_^. Technological ^_

Design

I

Design optimization

Technological

Evaluation

[image:11.520.27.493.116.457.2]

Drawing

oftechnicaland manufacture documents

Fig. 2. Flowchart of productdevelopmentprocess[1

]

Developmentofnew product

begins

withresearch and

development

planning. This

phase establishes need for product manufacture _according to the buyers' _requests,

marketing analyses, trend studying, analyses results of production

techniques,

or some

other criteria. In this _case, request

for development

comes

from idea

of an

individual

as

patentedinnovation. Request for product

development

describes

development

goals and

it

can

be

understoodas engineer problem.

Planning

considers _{economic-technical,} organizational and other _necessary

conditions

for

development

in

specific manufacture system.

Product planning

represents

operational scientific-methodological

discipline

because

of

decreasing

the risk of

scientific-methodological attempt of

getting

the answer on

launching

and_placingthe product on the

market,aswellas

its

market

life

time.

One

ofthemostimportanttasksofproduct_planning

is

decreasing

the

difference

between

thenumber of

innovations

andcommercial products,

which

is,

according

to the

McCarthy,

40:1.

[

1

]

The

last

part of

flow

chart shown at Fig. 2.

includes

activities as

first

_step to

designing.

From technical point of _view,

designing

has

the central place in product

development.

Approach

to product

development

and

designing

from technical,

economical

and sociological point of view

is

calledtechnological development.

Newproduct

Functional

requirements

_^. Assembleprojectteam

-? Conceptual partdesign

-4-Material selection en _^ c CD O Q. O c CD o > o _o c O) CO CD T3 ffl i_ D O D i_ CO c O) CO CD T3 O) c N ro c H

I

Structural conerns

7^

Tooling

and part fabricationfeasibility

1

Moldability

Computeraided structural analysis

N

y^ Computeraided

"? _{moldingsimulation}

J

Modified partdesign

J L

Prototypetool or

prototype part

production and

testing

Production

tooling

I

Detailedtooldesign

runners/filling mold_cooling part ejection mold structural Tooltrials partfabrication part evaluation process evaluation

Releasetoolfor

production

[image:12.520.33.490.198.598.2]

Technological

development

can

be divided

in 3 phases:

-concept

developing

(preliminary design)

structural

design

-finalizing

design

Inthis thesis _only parts of product

development

process which are shown

in flow

chartin Fig. 4. will

be

taken

into

consideration.

Newproduct ? Assembleprojectteam

Functional

requirements -?

Conceptual partdesign

^-1

Structural conerns

I

[image:13.520.75.438.179.368.2]

Computeraided structural analysis

Fig. 4. Flowchart of_{thesis methodology}

Material

selection

Thesis methodology:

After

defining

functional _{requirements, proposing} the material and process of

production, GECOS

bottle

dimensioning

can

be

_proceeded, as one ofthe most

important

phaseinproduct

development

process.

Whenthe GECOS

bottle

_geometry

is

_completely

defined,

structural design analysis

can

be

_performed, as _checking whether this

bottle

_geometry together with proposed materials canbarethepossible

loading

in

exploitation.

Considering

comprehensiveness oftheanalysis

for

the complicated

GECOS bottle

3.1.

CONCEPT DEVELOPING

Concept

developing,

asthe

first

phase

in

technological development process, starts

with an

idea.

The

idea includes

theart _component,to achieve nice and aesthetic

form,

and

from

this

beginning

the

idea is

developed

into

a workable product.

At

this point there

is

obviously

much to

be done

before

the

idea become

an actual product. There

is

still not

enough

information

tomake

determination

on

how GECOS bottle

should

be

built.

Function analysis, which

GECOS bottle

must_satisfy,

is

the

first

step inthe process.

Based on such _analysis, certain requirements can

be

established. Functional requirements

can

be divided

ongeneral andtechnological requirements.

Synthesis

of requirements

into

so called complex unit

forms

the list of

requirements.

Technological Requirements

r _? 1

Technical Requirements Social Requirements

Functionality

Manufacturability

-Society

Development - Health

-Ergonomy

- Esthetic - Education

-Ecology

-disposing

-recycling -security Economical Requirements [image:14.520.43.480.301.557.2]

3.1.1.

FUNCTIONAL

REQUIREMENTS

Theentiretechnological

development

processbeginswitha complete andthorough

definition

ofthe _{product specifications and end-use} requirements. This is thefirst stage of

development

and _very

important because

the technological development of product is

based

onthesespecifications.

Product

functional

_{requirements,} act as central _clearing point and vital

communication channelthroughwhichideasareassembled andevaluated.

Functionalrequirements:

The ultimate requirement of_anyproduct is thatit perform thefunction forwhichit is

designed.

Primary

function ofGECOS bottle is to store and transport liquids in food

domain,

which are _{easy fusible in water,} so this

bottle,

ones emptied can _{easily be}

washed. Liquids in the

bottles

are from food

industry,

such as mineral water,

juices,

milk

-as

long

as

they

are not carbonated. It

is because

of square shape ofthe

bottle,

whichdoesn't allowbulging.

GECOS bottle is made of plastic.

Loading

requirements:

Dimensional

bottle

_stability must be ensured even on worst

loading,

which can be

anticipated

during

bottle exploitation. It is assumed that it is the time when GECOS

bottle is

full,

packed and it

is

placed onthe bottom ofthe pallet

during

_warehousing

andtransport.

Environmental requirements:

Outer environmental _conditions, onwhich GECOS

bottle is

likely

to

be

_exposed, are

high

humidity

and variations

in

temperaturesbetween+40C (inwarehouse and

during

transport)

to-20C (since cooling beverage inrefrigerator).

Dimensional requirements:

Distance betweensunkcenters,which is equalto the cube side

length,

aswell as outer

diameterof_connectingelement

-closure,isthecritical

dimension.

GECOS bottleshould

be dimensioned in

such_waythat

its inner

volume

is

1 1.

- It

is

desirable to _{get as} higher _{cube and area effectiveness}

as

it is

possible

during

Ecological

requirements:

-Ecological

requirements refer_{to the material,assuming}thatplasticfor_makingGECOS

bottle

could

be

recycled.

Since

the construction ofGECOS bottle enable the easier

keeping

and _collecting, the _{empty GECOS}

bottles

will not be disposed

daily

into

refuse,

but

will be

disposed

more _rarely and

in

greater quantities on separate disposal

locations,

in order to enable _{their recycling,} what means that the environmental

pollutionwillbe significantly less.

Socialrequirements:

GECOS

bottle is new

designed,

so it will _satisfy

industry

and market needs for new

product.

Theclosure mustbeequippedwith_safetyring, asproofthatbottleswerenot opened.

GECOS bottleadditional _{using quality is}performed when it

is

_emptyandbecomesthe

objectof children's_play,which canbe composed inthree-dimensionalstructures, such

as

building

blocks. Inthis _{way it} satisfies educational requirements. It is _{necessary to}

offer enough different shapes of GECOS bottles to construct as more different

3.1.2.

MATERIAL SELECTION

In this phase materials and process which can produce GECOS bottle must be

selected.

Quality

of

design

solution of

GECOS bottle

directly

depends on characteristicsof

polymers as

design

materials and characteristics ofthe process for the production. Like

with _any other _material, product design in plastic must _satisfy two basic requirements.

GECOS

bottle

must provide reliable end-use

functionality,

and while

designing

the

bottle,

manufactureinspecified material and specifiedprocess mustbetakenintoaccount.

Plastics are material of

design.

Plastics are available in almost indefinite range of

properties, releasing them from the structural-design limitations imposed on metal and

glass. Basic truism of structural design is that the material and the process selected

profoundlyaffectthe_qualityand appearance oftheproduct.

[

3

]

Considering

the

liquids

in the

bottles,

as well as _{requirements, two} materials were

takeninto account. Firstmaterial

is

PET (Polyethylene

Terephthalate),

andthe second one

is FfDPE (High

Density

Polyethylene). Which ofthese two proposed materials would be

betterto use, from structuralpoint ofview,willbechecked

by

structuraldesignanalysis.

In structuraldesign analysis modelAwouldbe ofPET_material, while model B of

HDPE.Bothmodelswouldhavethesame_geometryandwouldbe loaded inthesame way.

Increased popularity of PET containers

by

consumers

has

called for

design

innovations

by

the industry. PETcontainers are ideal

for

bottling

_water, soft

drinks,

juices

and other food products. Some of the advantages of PET containers vis-a-vis other

packaging alternatives include:

flexibility

in

design,

superior _{clarity, easy} to

handle,

shatterproof, pure, inert and

lightweight,

excellent barrier _{to moisture, oxygen,} carbon

dioxide and aroma. Due to their extreme _{clarity (like glass),} PET bottles are always

preferredforcarbonatedsoftdrinks andmineralwater.

PETpossestheexcellentbalance of properties andthe

degree

of_{cristallinity}sothat

level of orientationinthe

finishing

product can

be

controlled.

PET bottles are

fully

recyclable and used

bottles

can

be

crushed and recycled

into

materialsforre-use orused

for

_making

textiles,

carpets and other plastic

items.

The most significant application features of HDPE are _easily processibility and

good moisture

barrier.

Its

low

_oxygen-,

hydrocarbon-,

and flavor-barrier properties limits

its use

for

some applications. The most

blow

molded HDPE containers are pigmented to

improve

appearance, although natural HDPE

is

used for _{many packaging} applications

particularly for food.

Clarity

ofHDPE is_poor, it is translucentin itsnatural stage and can

betintedwith_anyopaque color.

3.1.3.

PROCESS

OF

PRODUCTION

Selection

ofthe _processing method shouldtake place in the _earlystages ofdesign

process.

Since

PET and HDPE are selected for material which can _satisfy most of

requirements,production processwhich

is

compatiblewiththismaterials

is

blowmolding.

Blow molding

is

a process fortheproduction ofhollowobjectsinwhich airis used

to expanda

hot

preform (or parison) againstafemalemold cavity. Common featureof all

blow

molded articlesis

bottle

having

an_openingmuch smallerthanthebody.

[

4

]

An

important feature is

the _capability to provide _very thin wall selections with

relatively

low

stress.

PET istheresinthatcanbe

biaxially

oriented

by

stretchblow moldingwith careful

temperature _conditioning ofan injection molded _preform, but for the smaller bottles the

resinis alsousedinthebasic injection blow_moldingprocess.

HDPE is the resin most common used in blow molding in both extrusion and

injectionblow_moldingprocesses.

3.1.4. CONCEPTUAL DESIGN

The

invention in its

essence consists of square bottle construction, which on its

sides

has

sunk

connecting

_{places shapedto acceptthe closure as connecting} element. The

closure ispressed-inintothe_connectingplace ofboth GECOS bottles.

Several

ideas have

to be enquired and more than one model drawn before a clear

model canbe

formulated.

First it

is

_necessaryto

develop

aset of_{working drawings. When}

the general configuration is established, computer aided design

(CAD)

needs to

develop

complex curves and shapes representedintheapplication.

Mayor changes on GECOS bottle shape are made in cube corners and on corners

below the neck. Cube corners are not rounded as

they

were on drawings in patent

application. Now

they

are with slanted _edges, so the bottle looks as grind _prism, to

associate on

ice

or diamond. GECOS

bottles

basic form is prism which consists ofthree

cubeswithslanted edgesconnected with partition channels.

Becauseofbetterstatic _stabilitytheload

bearing

wall is designed bellowthebottles

neck, continuos through bottle height. On drawings in patent application the partition

channels stretches all over cross section.

On all cube surfaces there are sunk_connecting places assignedto accept closures.

This bottle has 14 sunkplaces, one onthe

top,

one onthe

bottom,

andone on each side of cubes.

Ontheupper part there istriangular sunk_surface, while onits outer cornerthere is

neck. The placement ofthe neck at the sides on the bottle makes the _{liquid pouring} out

easier. The

top

oftheneck

is

leveledwiththeuppersurface.

Beside the basic function ofthe closure to close the

bottle,

it is also universal

connecting element. The closure is pressed-in into the _connecting place ofthe bottles. In

orderto ensure a compactcoupling, theouter closure diameter is biggerthanthe diameter

of_{the connecting} place. The outer diameter of closure

is

toothed with small elastic teeth

which enablethe necessarydeformation.

Closure has horizontal partition wall and thread _{is only} on one internal side.

Internalclosure

thread,

as well as thethread on_{the neck,}

is

not _specified, which enabled

potential clienttoset_up

his

own

dimensions

depending

on machines and casts.

Beside

basic

closure each

bottle has

additional _ring as well, which enable greater

number of_{connecting combinations,}

but

static _stabilityas well whenthe bottle is full and

onthe pallet. Whenthe

bottle

is

full

and_{closed, the} closure

is

higherthan the

top

bottle

surface, so it can _carry over the whole

loading

on the bottle _neck, so the bottle would

become

static unstable. It _{is why}theadditional _ringmustbeput on

top

surface connecting

place,whenthebottle is fullandonpallet. Theclosure and additional_ringaretheninsame

level. The

dimensions

ofadditional_ring arethesame astheclosurebutwithoutthread.

Since

uniqueness ofthe construction enables _connecting into three-dimensional

structures and represents

interesting

toy

for children

-creative didactics tool

(building

blocks),

it

is

_necessarytoofferto themarket various paletteofshapes. For_example, bottles

with oneortwo

blocks,

depending

onrequired_volume, ortriangleprism made of_{one, two}

or three parts. All these combinations must ensure dimension compatibility because of

connecting.

[image:22.520.229.473.82.561.2]

Fig. 6. Frontviewofthreepart squareGECOS Fig. 7. Frontview ofthreepart squareGECOS

bottle bottle

[image:22.520.48.228.117.559.2]

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Fig. 9.

Top

viewofsquare GECOS bottle

033

Fig. 10. Closure

028

i

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i

ff

j

Fig. 8. Crosssectionandbottomviewofsquare

GECOS bottle

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l&d5 ras.

3.2.

STRUCTURAL

DESIGN CONSIDERATIONS

GECOS bottle functional

requirements

include

_{dimensional stability}andthe_ability

to withstand

externally induced

service stress. It is necessary to evaluate structural

reliabilityof suggested

design

toensurethatGECOS bottlewould serve adequately.

The goal of structural

design

process

is

to generate GECOS bottlethatwill be able

to withstandthe

loads

that are

likely

to be encountered

during

service. This must be done

within the constraints

dictated

by

the material. Since it is not possible to _quantify the

loading

conditions with great _certainty, structural design calculations willbe performed at

loading

conditionsthatarethought torepresenttheworst casescenario.

The purpose ofstructural design is achievement ofan acceptable _{probability that}

designed structure would not fit for the use

for

which it is _required, i.e. that it will not

reachaLimit State.

[

5

]

Since this_{philosophy is clearly}the goal of_{this thesis project,} itcan be difficult to

predict the _probability of failure for GECOS bottle design as the properties of plastic

materials are _{strong function} ofboth services environment and_{manufacturing} conditions.

Twofactorsthat toalargeextent arebeyondthecompletecontrol.

3.2.1.

DESIGN

METHODOLOGY

Different

approachesto structural

design

problemscan

be

used:

Design

by

experience

- Design

by

experimental approach

Design usingananalytical approach

Inthis thesisproject will

be

used analytical approach

[

5

]

[

6

] [

7 ].

Structural

_engineering relations allow us to estimate the stress that occur when

GECOS

bottle is

subject to mechanical

loading.

The results of such theoretical structural analysis provide sound

basis

on which design decisions can be made. An _engineering analysis generates an estimation ofhow GECOS bottle can be expected to behave under

loading,

since number of _assumptions, as material _{characteristics,} form _regularity, and

boundary

conditions,all ofwhich are_{simplifications,}mustbemade.

Use of computer aided linear structural analysis techniques has improved the accuracy, interpretation and speed at which structural design evaluations can be accomplished.

FEA (Finite Element

Analysis)

is used inthis structural design analysis. In FEA a complex problem is broken down into series ofinterrelated sub-problems that are solved

by

computersupport.

The first stage in FEA process is preprocessing. A 3D geometry ofthe GECOS bottleneedstobemodeled_{using CAD (Computer Aided}

Design)

system._{It is necessary}to

simplifythe geometry ofGECOS bottle for FEA. Finite element mesh made_up ofseries simple elementsinterconnectedat a_nodes,is superimposedinthisgeometry.

The number ofelements, or mesh

density

used in _{the analysis,}

depends

on

factors

such as the rate of change in strain at the particular area ofthe

bottle.

Exact solution

depends on proper shape offinite element and exact mathematical

description

of strain

divisionanddeformation inside finiteelement.

Boundary

or restraint conditions represent _any movement restrictions that the

model should obey.

The

loading

is applied at the end ofpreprocessing. In this case _only the static

loading

has beentakeninto consideration.

The second _{step in applying} the FEA method is solving the equations. Since

computer solves

hundreds

of equations _{simultaneously} stress and deformation are

generated asresult.

The

last

_stepoftheFEA method consistsofresultsinterpretationandevaluation.

By

analyzing the

loading

and calculation of deformation and stress, it will be

checkedwhichof proposed materialscan

be

used.

3.2.2.

QUANTIFYING

THE DESIGN PROBLEM

In order to evaluate the structural characteristics of the

bottle,

structural design

problems must

be defined.

_{It is necessary}to _specifynumber of

factors

before _starting with

anytypeof structural calculations.Those

factors include:

part_geometry

typeofsupport orrestraint

loading

conditions

materialbehavior /mechanical properties

environmental conditions

safety factors.

Once these items have

been

quantified, we can perform series of design

calculations, examine_{the results, modify}

design,

recalculate and repeat design

details

until

desiredresults are obtained.

3.2.2.1. PART

GEOMETRY

GECOS bottle has

very complex geometry. In order to predict the stresses and

deformation

that result

from

an anticipated service

loading,

it is

_necessaryto _simplify the

geometryofthis

bottle.

It

is

assumedthat sunk onthe sides and on the

bottom

of

GECOS bottle

wouldn't

influence

on output results.

Only

sunk on the

top

ofthe

bottle

remained, since there

is

expectedto occur maximum

deformation.

Thesesimplifications

have

influencedgreat deal

on

decreasing

thenumber of elementsin FEA.

}t.IDEAS8: FSB CAD/CAMlab:jadrank

Fig. 14. Simplified 3D GECOS bottle model prepared _{for meshing (print} screen from l-DEAS

software)

[image:30.520.37.484.253.582.2]

3.2.2.2.

GENERATING

THE MESH

Chosen

shape of

finite

element

is

triangle shell with

length

of 7,5 mm. Finite

element

is

thinshell withthicknessof

0,5

mm

Elements

are generated with given

density

overthe entire bottle surfaces. Thenthe

nodes

belonging

to theelements are optimized

in

a_waythatnotwonodes areplacedatthe

same

location.

The

generated mesh must

be

continuous.

Totalnumber of generated nodes

is

6655.

Total

number of generated elements

is 3322.

I-1I.IJU.M+, IJI.IIJ.'ilHMff.W'WJMIMMimmiM _Jfilxl

4Q.{3#n

-Fig. 15. Finiteelement model- FEM_ofGECOS bottle (print

screen_{from l-DEAS software)}

[image:31.520.37.485.257.586.2]

3.2.2.3.

MATERIAL MECHANICAL PROPERTIES

The mechanical characteristics of material must be quantifiedbefore any structural

design

calculations can

be

carried out. Material characteristics such as mass

density,

modulus of_elasticityandPoissons _ratio, areused in design equationsto evaluatethe stress

and

deformation

associated with GECOS bottles loading. In _addition, these maximum

stress estimations mustthen

be

comparedwithmaterial stress-strainbehaviorto determine

whetherthesevalues remain within acceptable limits forthematerial that willbe used for

GECOS bottle.

Unfortunately,

mechanical behavior ofplastic material is quite complex

and

difficult

to characterize it completely. In stress and deformation calculations it was

taken the average values of material mechanical properties. The simplificationwas made

by

taking

thePETandHDPEas

isotropic

_materials, sothelinearanalysis can

be

made.

Units Mechanicalproperties PET HDPE

p

Mg/mJ

Mass

density

1,36 0,95

E N/rW Modulusof_elasticity 2000 1000

V Poissons Ratio 0,3 0,3

<T

N/mm'

Compressionstrength 100 20

% Elongation 70 100

[image:32.520.67.454.315.442.2]

T C Temp,range -70/230 -20/250

Table. 1 Averagevalues of material mechanical properties

[

8

]

3.2.2.4. BOUNDARY

CONDITIONS

The

bottom

of

GECOS

bottle must

be

supported to

bare

the applied loading. In

order to remain

in

equilibrium

(i.e.

F=0),

balancing

forces

arethe reaction

forces

atthe

supports.

Support

conditions are

idealized.

Real

life GECOS

bottle

has

support conditions

that

differ from

these

idealized

cases to some

degree. Conditions

that reach the actual

support condition are to

fix

the

bottom

ofthe

bottle. Fixed

support condition of

bottom

plate prevents rotation aroundx,yand z axes and

displacement in

_{any direction.}

fflLi:

onsurtacsicreated

1 forcesonsurfacesoverwritten

1displacement restraintsonsurfacescreated

4 displacement restraintsonedgescreated

4 displacement restraintsonvertices-'points/locotions

r:

I

m

-_

^^^^

;

g)5tart||j^30[S||C^WMinV*gn32\oTd...||3JHASB:

FSBCAD/C-Fig. 16. Idealizedconditions of supportedbottomofGECOS bottle

[image:33.520.47.478.238.566.2]

3.2.2.5. LOADING

CONDITIONS

Once

part_{geometry and support conditionshave beenestablished, the}

loading

must

be

defined

and transformed or quantified into a

form

that

is

suitable for stress and

deformation

calculation.

In orderto evaluate the structural characteristics of a

bottle, location,

magnitude,

and type of

loading

must be quantified. It must be decided which types ofideal

loading

would reachthe real

life

situation.

GECOS bottles

are requiredto

function

under _variety ofdifferent end-use

loading

conditions. It

is

the

best

to evaluate the stress and

deformation

associated with

loading

conditions that are expectedto representthe "worst

loading

case conditions". Itshould

be

evaluated

for

safety.

GECOS bottle

is intended

for non-carbonated

liquids,

since the

filling

of such

liquid is made under atmospheric _pressure, in

full

bottle above the level liquid is

atmospheric pressure. The level ofliquid in full GECOS bottle is bellow the triangular

surface on the

top

ofthe bottle. The

top

of

full

GECOS

bottle

above the

liquid

will be

filled

with air under atmospheric pressure. Since the

load is

_acting on

top

ofthe

bottle,

expected maximum

deformation

under the

load

will occur on

top

of the

bottle.

In

accordance withthis theassumptionis toneglect

hydrostatic

_pressure,

because it

wouldn't

help

in

decreasing

the stress and deformation ofGECOS bottle

top

surface. The structural

designanalysis willbemade on_{empty GECOS bottle.}

It

is

assumption that "worst case

loading

condition"

appears while

bottles

are

packed onthe lowestrowonthepalletinwarehouseorintransport.

With software CAPE99 the most efficient _way of_putting the

bottles

on standard

Euro _pallet, with dimensions 1200x800x144 mm,

has

been established. Condition of

putting the second package onthepallet

is

by

height,

while allthe combinations

by

rows

and columns are permitted. No overhang is allowed on the pallet.

Maximum

allowed

height

of_{putting in}onthepallet

is

1.5 m,whilemaximum mass

is 1000 kg.

Secondary

package is defined as cardboard

tray

with stretch wrapping. Inside the

secondary package _putting

in

of

6, 8,

10 or 12 GECOS

bottles is

allowed.

Condition

of

putting GECOSbottles insecond packageis

by

height.

Sol. No.

Bottle Arrangement

Primary

package- GECOS bottle Secondary

package Cubbe

Eff.

Area

Eff.

L W H #

l

'ay

# rows

#/tray

#/load L W H

1 3L-2W-1H 77 77 240 25 5 6 750 231 154 240 82 93 3 5L-2W-1H 77 77 240 15 5 10 750 385 154 240 82 93 13 4L-2W-1H 77 77 240 17 5 8 680 308 154 240 75 84 15 6L-2W-1H 77 77 240 11 5 12 660 462 154 240 72 82

Table2. Solution Report

Product Name Product Code Datafile Name Solution Ref.

Cube Used Area Used Pallet type bottle_3s (15.03.) 1 C 82,3 % 92,6 % Euro

6 Bottle /

750 Bottle / Load

25 / Layer

5 Layer / Load

125 / Load

Bottle

Load

Outside Dimension

Length Width Height 77,0 77,0 240,0 mm

231,0 154,0 240,0 mm

1200,0 600,0 1350,0

We ight

Net Gross 1,000 1,050 Kg 6,300 6,300 Kg 787,500 812,500 Kg

Cube 1422 cm*3 8537 cm*3 1,30 m*3 Pad 240,0 154JO

!<$>!

390,0 77,0 240,0 77,0

l.This is an example for the CAPE PACK'

99 User Guides

2.Issued on 1/1/99

3. Issued byQC Department

4.Approved by QC Hanager

5-Use from 1/1/99

[image:35.520.37.488.58.149.2]

6. Valid until 31/12/99

Fig. 17. ReportfromCAPE99(bestsolution underNo.

1.)

[image:35.520.45.418.175.569.2]

Solution

under

No.

1.

(3Lx2WxlH)

gives the

best

cube

(82%)

and area

(93%)

effectiveness',

i.e.

the

largest

number of

bottles

on the pallet

(750),

and with lowest

number of

secondary

_{package per pallet(75). Onepallet consists of5rows}

by

height.

Since bottle

volume

is

1

1,

it is

assumedthat

liquid in

thebottle

is

water of

density

of

1000

kg/m3.

The

mass of water

is

1kg

per

bottle.

In suchcase,

loading

of

bottles in first

row on pallet

is

4kg,

i.e.

40 N.

Distribution

ofthis

force is indicated in

following

way:

-closure carries overthe

loading

ontheedge ofthe

bottle

neck, and sincethe neck

is

by

the

bottle

_angle,total

loading

is assumed 10 N. Inthiscase

loading

type

is

described as

concentrated at

line.

-additional_ring carries overthe

loading

on _ring sunk surface onthe

top

bottle surface.

In this case

loading

type

is described

as

distributed

over area and total

loading

is

assumed 30 N.

Point Location: 00 Model fliechanges

1 forcesonedgescreated

1 forcesaunsur<*cescreated

1 forcesansurfacesovBrvritton

00 0 0 file H.NbocaVbocallrati

Pick ForceonEdgej/TracboruonSurface) Pick FwceonEdBw*/Ti<fctononSurfaces[Done]

[image:36.520.46.478.318.645.2]

Zl

-a8start||j ^|0%jl_|jWci\WINNT\System32\oiid.,.|[{gl-OEASB: FSBCAD/C EH** 9*5

Fig. 18. Idealized

loading

conditions

3.2.3.

RESULTS

rii.lJll.MH:IJMiJJ'IBIIWIM*MIMWWW*)lffli-Fig. 19. ResultsofstressonMODEL A

Maximumstressunder requested

loading

of40 Non modelAis:

l,99E+04 mN/mm2

= _{19,9 N/mm2. It}

is

indicated_onthe

top

ofthe

bottle,

just

by

the sunk

edge on

top

_surface,opposite ofthe bottle neck, as it is shownin Fig. 19. Maximumstress

is

colored

in

red.

Comparing

with values on color

bar it

can be seen the distribution of

stress

in

GECOSS bottle. Maximum stress

is less

than compression strength of the

material which

is

100

N/mm2

for

the PET. It proves that model A will hold "predicted

worst case _scenario", i.e. that calculated stress

is

within tolerances and bottle is well

dimensioned. Since the compression

loading

is taken

into

account, the stress that occur

in

model can

be

compared withcompressionstrengthofmaterial. [image:37.520.43.479.87.405.2]

[image:38.520.46.455.371.682.2]

LJUilfU.^iJilJ.MJj.lilllHDillllllHilllUiMffmiiWunf

Fig. 21. ResultsofstressonbottomofMODEL A

[image:39.520.43.479.54.379.2]

LJI!.IJ.LM^,IJ.l.HJll.|iimf|MWIWI!S!HMBnm7

Fig. 22. ResultsofstressonMODEL B

Maximumstressunderrequested

loading

of40 NonmodelB is:

l,99E+04mN/mm2

= _{19,9 N/mm2. Sincethe}

geometryof modelB

is

the sameas_geometry

ofthe model

A,

as well as the

boundary

conditions and

loading,

also the distribution of

stress

is

equal, as

it is

shown

in

Fig. 22. Maximum stress

in

model B

is

equal to

compression strength ofHDPE

is

20 N/mm2. It can be concluded that model B needs

dimensionoptimization.

[image:40.520.42.466.55.367.2]

L,U,JH;.:lJi.,ij.i;|.B^Wra,;MwE!E

Jnl*l

Fig. 23. Resultsofstresson

top

ofMODEL B

-JC.I-DLA5(l: I SB LAD/LAMlab: jadiankam:M:\boca\bocal jnjx]

Fig. 24. Resultsofstress onbottomofMODEL B

[image:40.520.45.467.390.699.2]

tJa.ij.u.Mj.i.ij.i.ijjj^iJiiuMiijJi.ni.'iuimiHjmTiBinmr _njxj

[image:41.520.44.479.53.368.2]

;Ustsresuftsdata forlocationson a results_display 4-_Q.a& d

Fig. 25. Resultsofdisplacementon MODEL A

On model

A,

the greatest

displacement

is 2,46 mm and

it is located

between the

bottle

neck and sunk on

top

_surface, as

it is

shown in Fig.

26.,

where maximum

displacement is

colored

in

red. Fig. 25.

indicates

expected

displacement,

where mesh

modelrepresents_startingmodelbeforebottle

loading

(withoutdeformation). Until GECOS

bottle is

on _pallet,

it is

clamped with otherbottles that are beside

it,

but

that restriction

is

not predicted

in

boundary

condition and that

is

the reason _why this

bottle

have slightly

declining

because

offeccentricload.

lJl]]MIMH;JHJI1mi.l.Ukt.|lJ.I.W!MBBIMWIIW

[image:42.520.48.474.53.369.2] [image:42.520.45.469.392.705.2]

^jnlxl

|Generatesa report on selected_displayresufrs _4Q.0#n

Fig. 26. Resultsofdisplacementon

top

ofMODEL A

4kI DFA5 R: FSB CAD/rAMl.ih:j.idrank. _jDjxJ

Fig. 27. ResultsofdisplacementonbottomofMODELA

[image:43.520.46.481.54.384.2]

ESa,IJ.U:J4IJ.J.UJ,l.|iWBBjBWM!MiggI

Jn|x]

Fig. 28. Resultsofdisplacementon MODELB

Maximum

deformation

_occurring

in

model B equals

4,93

mm. Elongation as the

amount of stretch

in

FtDPE

is

100 %. Maximum

deformation

of model B is two times

higher

then maximum

deformation

of model

A,

and

it

can

be

concluded that model B

needsthickerwalls.

MODEL

A

MODEL B

Max

stress

in

N/mm2

20

20

Compression

strength

in N/mm2

100

20

Max

displacement

in

mm

2,46

4,93

Elongation

of material

in

%

70

100

Table3. Results

[image:43.520.38.484.500.608.2]

[image:44.520.44.468.56.363.2]

jh-.l-DLASo: r-su lad/lamlab: ladtankam:I l:\boea\bocal

Fig. 29. Resultsofdisplacementon

top

ofMODEL B

Fig. 30. Resultsof_displacementonbottomofMODELB

[image:44.520.44.468.385.697.2]

4. CONCLUSIONS

Model

formulation

and the

corresponding

_{calculations were performed with the}

following

assumptions:

-

Average

values of material mechanical characteristics were

taken,

withthe assumption

thatPETandHDPEare

isotropic

materials.

In

idealized

boundary

conditionsthe

bottom

of

GECOS bottle is fixed.

It

is

assumed that themost

intense

loading

case

is

whenthe

bottle is

in

lowest

rowon

pallet,

loaded

with

four

rows

full

of

filled bottles.

In structural

design

analyze _onlythe

static

load is

taken

into

consideration.

- Becausethe

non-carbonated

liquids

are

filled in bottles

under atmospheric_{pressure, the}

internal

pressure above the levelof

liquid

in full

bottle is

also atmospheric. The load

is

acting on

top

of

bottle,

and it is the place where maximum deformation is expected.

Sincethe

hydrostatic

pressure canbeseparatedfromtheeffects caused

by

loadapplied

on the upper _surface,

it

can

be

neglected. The structural design analysis

is

made on

empty bottle.

Geometry

simplification were

implemented

thatmade possible reduction of simulation

time through

decreasing

thenumber offinite_elements,which were usedincalculation,

yet withthe resultsprecisionkeptunchanged.

Twomodels

having

the same _geometry, loadedwiththe same static

load,

and with

the same

boundary

conditions but made ofdifferent materials were considered. Model A

was made of PET and Model B was made of HDPE. The calculations of stress and

deformationaremadeon modelAand modelB.

The results obtained from calculations of stress and deformation are presented in

Table 3. Asthe consequence ofthe compression characterofload was

imposed,

the stress obtained

from

analysis can _relatively

be

compared with compression strength of given

materials. As

it

can be seenthe maximum stress in case of model A

is five

times lower

than compression strength ofPET. Since the elongation ofPET is

70%,

the maximum

deformation of2,46 mm is considered acceptable for thepresent purpose. The maximum

stress in case of model B is the same as compression strength ofHDPE. In addition the

maximum deformation occurring in case of model B equals 4,93 mm.

Therefore,

can be

concludedthatmodel

B,

needsdimensionoptimization.

The model

A,

with wallthickness 0,5 mm, gives _satisfactoryresults ofstress and

deformation,

hence it can be concluded that the model A

is

well dimensioned. Further

more,it iscapable _{to withstand,}with gooddimensional_{stability, the}

loads

thatare

likely

to

beencountered

during

service.

Following

steps in the

development

of GECOS bottle are to make non-linear

analyze, and with CAM (ComputerAided

Manufacturing)

systemto check a_possibilityto

manufacturethat

bottle,

andtomaketheprototypesthatwillbeusedinthetesting.

REFERENCES

[

1

]

Raos &

Catic

-Razvoj

presanih polimernih

tvorevina,

_{(Development of}polymer

products), Zagreb 1992.

[

2

]

Robert A.

Malloy

-Plastic Part Design

for

Injection

Molding,

Hanser

Publishers,

Munich, Vienna,

New

York,

1994

[

3

]

HandbookofPlastic Materialsand

Technologies,

editor: Irvin I. Rubin

[

4

]

Fundamentalsof

Packaging

Technology,

W. Soroka

[

5

] Sidney Levy

& J.

Harry

DuBois

-Plastic Product Design

Engineering

Handbook,

Published

by

Van Nostrand Reinhold

Company,

NY 1977

[

6

]

Bruce C. Wendle- What

Every

Engineer Should Know AboutDEVELOPING

PLASTICS

PRODUCTS,

Marcel Deckker

Inc.,

NY 1991

[

7

]

PaulA. Tres

-Designing

Plastic Partsfor

Assembly,

4th

Edition,

Hansen Gardner

Publications

Inc.,

Munich2000

[

8

]

M.

Nadj

- Polimerni

materijali,Zagreb 1991

[

9

]

JosephF.

Hanlon,

HandbookofPackage

Engineering,

McGraw-Hill Book

Company,

USA,

1984.

[

10

]

l-DEAS Tutorial