design and engineering-risks

7/25/2019 Design and Engineering-Risks

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RELIABLE ELEMENTS OF

DESIGN

Dr. Shouri P.V.

Associate Prof. in Mechanical Enineerin!

Mo"el Enineerin #ollee!

Thr$$a$ara! #ochin % &'( )(*! +erala.

E,-ail /0shouri1-ec.ac.in


2/101

Design Process

Design process is a collection ofprocedures and habits that help teams

design better products


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Design - Then and Now


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How dose CE Reduce Time?


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What Do the End UsersWant?

Performance& Functionality Aordability

Ease of useincluding ergonomics Reliabilityand Long life- Safety

Lo maintenanceand easy assembly Aesthetics


7/101

!his amusing picture" of an anti-drugpropaganda pencil hose message is sub#ertedsimply by sharpening it$ !he truth is strangerthan some of the %ctions that accompany it itas sent to schools and recalled only after achild noticed the problem$ 'From a ())* +e

,or !imes report.


8/101

Aging is a /ery 0eneral Phenomenon1

According to Reliability !heory

Aging is +2! 3ust groing old4nstead

Aging is a degradation to failurebecoming sic" frail and dead


9/101

Product Design


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Design for Whom?


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4s the 5ustomer Satis%ed6


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Ultimate Goal of aDesigner


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Design - An 4terati#eProcess


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4s Product Design a5ompromise6


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ia!ilit"# $easi!ilit"#Desira!ilit"


19/101

%rea&-E'en (nal"sis

Some managerial 7uestions

8o much should e produce to brea

e#en6For a speci%c #olume" should e

manufacture the product oursel#es" or

outsource6For machine alternati#es A and 9" at hat

#olumes should e use machine A and at

hat #olumes" machine 96


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%rea&-e'en Chart


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Designer# User# Client

At times the user" the client and the customercould be the same or dierent


22/101

)*iral of Progress in+ualit"


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$actors (,ecting Product+ualit"


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What is Cost of +ualit"?

4t:s a term that:s idely used ; and idelymisunderstood$

!he uality 5osts

'(. 4nternal Failure 5ost'?.

E@ternal Failure5ost

'. Appraisal 5ost'B. Pre#ention 5ost


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*timum +ualit"


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$unction# !/ecti'es andConstraints in Design

$unction Chat does component do6

!/ecti'e

Chat is to be ma@imied orminimied6

Constraints

Chat non-negotiable conditionsmust be met6Chat negotiable but desirableconditions $$$6

Stiness and strength might be absolutere7uirements - hard constraints

5ost might be negotiable - a soft constraint


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Wh" 'er Design?


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How 0an" of These *tionsHa'e 1ou E'er Used?


29/101

4n the beginning as you addfeaturesfunctionality there is a good rise inuser e@perience$ 9ut it plateaus 7uicly ith a

sharp degradation$

)ta es of Prod ct life in


30/101

)tages of Product life inmar&et


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Point of Re-in'ention


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2ife C"cle E3tensions

Life 5ycle e@tensions can be achie#ed byaltering

the mareting mi@

(.Product

?.Price

.PromotionB.5hannels of Distribution


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Companies want their products to enjoy a long life

cycle

Altering the mareting mi@ can e@tend theproduct life cycle


34/101

+ot all products follo the con#entionalproduct life cycle


35/101

Apples designs ha#e consistently made

other destops loo bland and boring


36/101

5oca-5ola contour bottle is a masterpiece in

industrial design that dates bac to ()(G


37/101

5oncei#ed in ()? by 0eorge 5arardine" a cardesigner ho as oring on #ehiclesuspension systems at the time


38/101

Designed by Phillipe Starc in ())I" the JuicySalif is e@hibited in the Kuseum of Kodern Artin +e ,or - the design is based on the shapeof a s7uid$

Cash $low 4n'ol'ed at arious


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Cash $low 4n'ol'ed at arious

)tages


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Generali5ed 2ife C"cleDiagram


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Cost of Design

5ost of design is relati#ely lo for a product$8oe#er design is signi%cantly responsible forthe cost of its realiation

A good design alays brings don the cost8ence a good design should focus on costaspects of the product beyond its function andstrength

!his should be taen care of during e#ery phaseof design


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Cost of Change


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E,ort 6 Cost


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2n an a#erage" it taes about ( 9illionand (I years to bring a ne drug tomaret


45/101


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Concurrent s7 Traditional

Engineering


47/101

Reliability De%ned

Relia!ilit" is 89ualit" changing o'ertime:

As time tends to infnity reliability tends tozero.

Reliability terminates ith a failure ; that is"unreliability occurs$

Elements of Reliability'(. Probability

'?. Function

'. Coring 5onditions

Need for $ool-Proof )"stem


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Need for $ool Proof )"stemDesign

8umans err continuallyM it is an intrinsicpart of our nature$ System design shouldtae this into account$

!he system should be designed so that asingle act by a single person could cause

not cause calamity$

Emergence of Relia!ilit"


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Emergence of Relia!ilit"Engineering

!he %rst recorded usage of the ordreliability dates bac to the (*IIs" andas referred to a person and not atechnical system

!he ord reliability as %rst coined bythe English poet Samuel !$ 5oleridge" ho

along ith Cilliam Cordsorth startedthe English romantic mo#ement$


50/101

These lines Coleridge was writing in the year

1816, in praise of his friend the poet Robert

Southey


51/101

!he triode in#ented by Lee de Forest in ()IN"hich at the onset of Corld Car 44 initiated the

electronic re#olution" enabling a series ofapplications such as the radio" tele#ision" radarand others7

During Corld Car 44" airborne radios deli#eredinto remote locations of ar had appallingreliability of only about (O$

Car eorts also produced a ne eapon ofterror - the /-( rocet$ !he /-( rocet had ademonstrated reliability of ( success out of ((

attempts for a calculated reliability of )$


52/101

The V-2 rocket is a result of Werner Von Braunsredesign of V-1 rocket using the principles ofredundancy to enhance the rockets reliability.

!he /-? results are ritten in the historyboos for a demonstrated reliability

impro#ement program that resulted in thebuilding of more than *"III /-? rocet motorsof hich N"II ere %red$

5ompare the /-? 7uantities to only BB S5QDmissiles %red during the 0ulf ar and mostpeople today still remember terror falling fromthe sies #ia 5++ broadcasts$


53/101

V1 V2 S!"

The V-1 was first launched in the summer of 1!!,and o"er the ne#t se"eral months thousands of the

missiles were directed toward $ondon% &s they flew,

the engines made a distincti"e sound, leading the

'nglish to call them (bu)) bombs%*


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!he orean Car as a ar of hightechnology $

8oe#er" studies shoed ? of maintenancecosts for e#ery ( of capital costs during theorean Car$ 8igh maintenance costs led toestablishment of reliability re7uirements forrocurement of e ui ment$

!he %rst te@tboos ere ritten for the


57/101

!he %rst te@tboos ere ritten for theemerging %eld of reliability during the early()NI:s

During the ()NIs" TOIs" and T*Is applications ofreliability principles ere put to or$

During the mid ())Is" continuous processindustries such as petrochemical and re%ningbegan acti#e" formal" programs to impro#ereliability and decrease costs$

9oos on the sub3ect of reliability engineeringha#e e@ploded in sales #olumes during the

())Is$ !he ne boos are an engineering

Presently the largest number of reliability


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Presently" the largest number of reliabilityengineers in the orld is concentrated in theautomoti#e industry$

Some automoti#e companies estimatearranty cost represents ( the cost for ane automobile$ !his cost pressure results inreliability engineers oring to reduce the costof unreliability in the automoti#e industry forone reason - pre#ent loss of money$


59/101

Three $aces of Relia!ilit"

We see Reliability as three phenomenathat are oten lumped together to orm abathtub curve

T i # e

$

a

ilu

re

%

a

te

& a r l y $ a i l u r e s

o n s t a n t

$ a i l u r e % a t e

' n c r e a s i n g$ a i l u r e

% a t e

The value o bathtub curves lies inunderstanding concepts behind dierent

ailure rates and the medicine reuired

Pro!lem to !e (ddressed


60/101

Pro!lem to !e (ddressed!" the Relia!ilit" Engineer

The product starts to wear out as soon as you get

the +uality issues sorted out%not fair to the

customer

Ti#e


61/101

4nfant 0ortalit" Rate

!ndia " ## deaths per $%%% live births

&oa and 'anipur " $$

(erala " $)

'adhya *radesh " +,

-. . " /.0

ingapore " ).0

1apan " ).2

3hina " )%.)+

ri 4an5a " $2.+

2ife E3*ectanc"


62/101

2ife E3*ectanc"

!ndia " /+.+

(erala 6 7#

'adhya *radesh " +2

.% S% / 08%

Singapore / 81%6

2apan / 8%

China / 03%3Sri $an4a / 0!%0


63/101

%asic Relia!ilit" E9uationReliability is a measure of the probability for

failure-free operation and is often e#pressed as

5ey parameters describing reliability are mean

time to failure, mean time betweenbefore repairs,

mean life of components, failure rate and thema#imum number of failures in a specific time-

inter"al%

=

t

dttZ

etR )

23

23


64/101

Constant Ha5ard 0odel

7or a component with constant failure rate, the

reliability e+uation reduces to

where 9 is the constant failure rate

:n reality, e"en though this holds good only in-

between the period of infant mortality and wear-out, it is often a reasonably good assumption as

this time frame is e+ual to almost the entire lifetime

of any e+uipment%

tetR =23

ariation of Relia!ilit" with


65/101

ariation of Relia!ilit" withTime

(t)

Ti#e

The constant ha)ard model is generally usedfor the calculation of component reliabilities for

a gi"en system%

0T%$ of a Constant Ha5ard


66/101

0T%$ of a Constant Ha5ard0odel

The constant failure rate model is widely used in

the literature to reduce the computational burden

of the resulting problem because the parameter

mean time between failure ; becomes time-independent in this case%

*23))

===

dtedttRMTBF t

C t R li !ilit C l l ti


67/101

Com*onent Relia!ilit" Calculation

* particular co#ponent has an of +TT$ of ,hours. onsidering a unifor# failure rate /hat is

co#ponent reliability for 2 hours0

4)))

*

=;per hour>

t 2 hours

robability of failure 1-.343 .5321 ;or>5.3216

;or>34.73?5&)65.)2())3())

4)))*

==

eR

Elements of )"stem Design


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Elements of )"stem Design

Characteristics of Product ;


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;)"stem Design

( 5omponents----------------------Subsystems? 4nterrelated components

9oundary

B PurposeG En#ironment

N 4nterfaces

O 4nput* 2utput

) 5onstraints


70/101

)"stem Relia!ilit"

.23232323 7(* etctRtRtRtR ComponentComponentComponent =

Reliability of a process or system may be theproduct of many different reliability terms, such

as

@ith the increase of number of essential

components in the system, the system reliability

will decrease and to achie"e high systemreliability component reliability "alues should be

"ery high%

The Conce*t of Relia!ilit"


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* ")tructure

The logical arrangement of components that areimportant for system reliability is called Reliability

=loc4 Aiagram ;R=A>% The systems can be made

up of either

*) Series

() Barallel, or

7)


72/101

)eries Con


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Parallel Con


74/101

0i3ed Con


75/101

g "Con


76/101

Human %od"Vital rgansare connected

in series

Cells in "ital

organs areconnected in

parallel

Relia!ilit" 4ncreasing


77/101

Relia!ilit" 4ncreasingTechni9ues

ne way of achie"ing high reliabilities is by

introducing redundant parts% 7or e#ample we may

ha"e two parts in parallel such that the system

operates if at least one part operates%

R(t) 1-(1-.3,)(1-.3,) .337,

R(t) .3,

=y adding a redundant part we ha"e increased the

reliability of system at time t from D%E to D%0E

Hot )tand-!" s7 Cold )tand-!


78/101

!"@e ha"e been assuming that both parts are

operating whene"er the system is on this is some

times called hot standby and is not always

practical%

@e may need to pro"ide a cold stand by where thesecond part is switched into ser"ice when the first

one fails% Then we must also ta4e into account the

reliability of the switch%

:f the switching de"ice is ha"ing reliability D%8 attime t we ha"e the system reliability at time t as

R(t) .3, 8 (.,)(.39)(.3,) .3344

Relia!ilit" *timi5ation


79/101

Relia!ilit" *timi5ation

:t is usually necessary to perform trade-off

calculations to determine the ad"isability ofparallel redundancy "ersus impro"ement of the

reliability of the basic subsystem by other means%

2aunches


80/101

2aunches

!SS%-512 successful 2: failed 35.76 success rate

!S* - 1:,7 successful 1,5 failed 3.,6 success rate

&! - 22: successful 17 failed 32.76 success rate

hina - 133 successful 17 failed 32.16 success rate

;apan - 95 successful 1: failed 9,.46 success rate

'ndia - 55 successful 1 failed 74.16 success rate

Source: Claude $afleurFs Spacecraft 'ncyclopedia,21,

0inimi5e the Num!er of ital


81/101

0inimi5e the Num!er of italCom*onents

8ecrease the number o component parts or asystem and believe in the vital e9. :or asystem that contains + items connected in

series the system reliability is ;


82/101

Com*licated Designs Tendto Decrease Relia!ilit"

%est Desisgn is the )im*le


83/101

%est Desisgn is the )im*leDesign

& designer 4nows he has arri"ed at perfection not

when there is no longer anything to add, but when

there is no longer anything to ta4e away%

-- &ntoine de Saint-'#upery

The price of reliability is the pursuit of the utmost

simplicity% :t is a price which the "ery rich find "ery

hard to pay%-- Sir &ntony Goare

Parts Derating


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Parts DeratingQse derating to assure that stressesapplied to the parts are loer than the

stresses theparts can normally ithstand$


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86/101

0enerally failures occur if Load e>ceeds

Strength


87/101

ther Relia!ilit"


88/101

ther Relia!ilit"4m*ro'ement 0ethods

Re#ie the selection of any parts that arerelati#ely ne and unpro#en$

Qse standard parts$

5ontrol the operating en#ironment to pro#ideconditions that yield loer failure rates$

Specify replacement schedules to remo#e andreplace lo-reliability parts before they reach

the ear-out stage$

ther Relia!ilit" 4m*ro'ement0ethods


89/101

0ethodsPrescribe screening tests to detect infant-

mortality failures and to eliminatesubstandard components$

5onduct research and de#elopment to attainan impro#ement in the basic reliability ofthose components hich contribute most ofthe unreliability$

(utomoti'e Relia!ilit"


90/101

(utomoti'e Relia!ilit"

The proportion of electronic components used in

motor "ehicles has been increasing steeply inrecent years% :n fact, many industry obser"ers

e#pect electronic components to account for !D?

of total car production costs in the near future%

Gowe"er there is a concern that the life of the

electronic components is relati"ely low thereby

affecting reliability%

Ae"elopment of highly reliable, large-scale

software programs for microcomputer control has

become a crucial matter for the automa4ers%

Need for


91/101

A story tells of 8enry Ford:s buying scrapped

Ford cars and ha#ing his engineersdisassemble them to see hich parts failedand hich ere still in good shape$ Engineersassumed this as done to %nd the ea parts

and mae them stronger$

Ford e@plained that he anted to %nd the

parts that ere still in good shape$ !hecompany could sa#e money if they redesignedthese parts to fail at the same time as theothers$

Need for)"nchroni5ation


92/101

('aila!ilit"


93/101

"&"ailability is the ratio of time a system or

component is functional to the total time it isre+uired or e#pected to function%

MTTRMTBF

MTBFtyAvailabili

+

=

Relia!ilit" and )afet"


94/101

Relia!ilit" and )afet"

Design for = tools


95/101

gDesign for Kanufacture andAssembly

Design for Reliability

Design for Kaintainability

Design for Ser#iceability

Design for the En#ironment

Conce*t of Energ"


96/101

* g"Producti'it"

*roductivity ?Inputs

Outputs

@nergy *roductivityH

tEnergyInpu

Outputs

0inimi5ing Energ"Consum*tion at the Cost of


97/101

Consum*tion at the Cost ofRelia!ilit" ?

oog e s e un anc"(**roach Towards


98/101

(**roach TowardsRelia!ilit"

& ser"er room in Council =luffs, $owa

( 0easure of Google>s Energ"Consum*tion


99/101

Consum*tionIoogle used %3 billion 4ilowatt-hours of electricity

last year, about the same as what DD,DDD .%S%homes would use in a year / that is e+ui"alent to

one +uarter of the output of a nuclear power plant -

the Jew Kor4 Times reports%

ne Ioogle search is e+ual to turning on a 6D@

light bulb for 10 seconds%

7or e"ery 4ilowatt-hour used for computing in a

typical data center, nearly a whole additional

4ilowatt-hour is used for running cooling systems%

Considera!le Energ" Used for Cooling)"stems


100/101

)"s e s

& central cooling plant in IoogleLs Aouglas County, Ieorgia, data center

(fter all Relia!ilit" is a Pro!a!ilit"


101/101

Th k

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