Sprin

g D

esig

n

Way

ne B

ook

ME3

180

Nor

ton:

Mac

hine

Des

ign

Bas

ic S

prin

g B

ehav

ior

Som

e Ty

pes o

f Spr

ings

Som

e Ty

pes o

f Spr

ings

(2)

Som

e Ty

pes o

f Spr

ings

(3)

Som

e Ty

pes o

f Spr

ings

(4)

Sprin

g M

ater

ials

: Wire

sPr

oper

ties o

f int

eres

t

Hig

h st

reng

thH

igh

yiel

d M

odul

us m

ay b

e lo

w fo

r ene

rgy

stor

age

Cos

tTe

mpe

ratu

re re

sist

ance

(e.g

. val

ve sp

rings

)C

orro

sion

resi

stan

ce

Com

mon

Mat

eria

ls (p

artia

l lis

t for

wire

s)

The

Cur

ious

Beh

avio

r as D

iam

eter

D

ecre

ases

Hel

ical

Com

pres

sion

Spr

ings

Leng

ths

Free

Ass

embl

ed

Solid

or s

hut h

eigh

t

Wor

king

def

lect

ion

End

Trea

tmen

t

End

deta

ils a

ffec

t act

ive

coils

Plai

n Gro

und

Squa

red

Gro

und

Sprin

g D

efin

ition

s and

Cal

cula

tions

Sprin

g in

dex

C4<

C<

12

Act

ive

turn

s Na

Sprin

g de

flect

ion

resu

lts fr

om to

rsio

n un

der l

oad

Sprin

g st

ress

incl

udin

gTo

rsio

nD

irect

shea

rSt

ress

con

cent

ratio

n K c

or W

ahl f

acto

r Kw

Stre

ss D

istri

butio

n

cons

ists

of c

ompr

essi

ng th

e sp

ring

past

yi

eld

as p

art o

f man

ufac

ture

The

resi

dual

stre

sses

rem

ain

in th

e in

ner

surf

ace

of th

e w

ireTh

is re

duce

s sta

tic st

ress

durin

g fo

llow

ing

cycl

esSh

ould

not

be

used

in te

nsio

nSh

ot p

eeni

ng c

an a

lso

be u

sed

prim

arily

fo

r fat

igue

stre

ngth

Buc

klin

g an

d Su

rge

of C

ompr

essi

on S

prin

gsA

pro

blem

for l

ong

skin

ny sp

rings

Rod

insi

de is

so

met

imes

use

d to

el

imin

ate,

but

wea

r an

d fr

ictio

n re

sult

Dep

ends

on

ratio

Lf/

D

Surg

e is

ano

ther

pr

oble

m th

at o

ccur

s w

ith e

xciti

atio

n ne

ar

the

natu

ral f

requ

ency

Prop

ertie

s of S

prin

g M

ater

ials

--Y

ield

Yie

ld st

reng

th fo

r sta

tic lo

adin

gD

epen

ds o

n se

tB

efor

e se

t rem

oved

use

Wah

l fac

tor

Afte

r set

rem

oved

no

stre

ss c

once

ntra

tion

used

Prop

ertie

s of S

prin

g M

ater

ials

--Fa

tigue

Fatig

ue S

treng

thTo

rsio

n is

rele

vant

load

ing-

coul

d us

e vo

n M

ises

stre

ssM

ater

ials

test

ing

spec

ific

to h

elic

al

com

pres

sion

sprin

gs is

ava

ilabl

e, h

owev

erC

orre

ct fo

r tem

p., r

elia

bilit

y, e

nviro

nmen

t

Prop

ertie

s of S

prin

g M

ater

ials

--En

dura

nce

Endu

ranc

e St

reng

th (s

teel

s) u

nlim

ited

cycl

esFo

r hig

h ul

timat

e st

reng

ths,

endu

ranc

e lim

its m

ax

out a

t 45

kpsi

(unp

eene

d) a

nd 6

7.5

kpsi

(pee

ned)

Smal

l wire

s hav

e hi

gh u

ltim

ate

stre

ngth

Test

s hav

e be

en d

one

spec

ific

to sp

ring

wire

Tem

pera

ture

may

requ

ire c

ompe

nsat

ion

Cor

rosi

onR

elia

bilit

y

S-N

and

Mod

ified

Goo

dman

Dia

gram

Des

igni

ng S

prin

gs

Func

tiona

lity

Stiff

ness

Leng

ths

Dia

met

erFo

rces

R

elia

ble

oper

atio

nSt

atic

fact

or o

f saf

ety

Fatig

ue fa

ctor

of s

afet

yB

uckl

ing

and

surg

e

Man

ufac

tura

bilit

y

Inde

x C

Mat

eria

lW

ire a

nd c

oil d

iam

eter

Num

ber o

f tur

nsEn

d tre

atm

ent a

nd

cons

train

tSe

t and

shot

pee

n

Req

uire

men

tsD

esig

n C

hoic

es

Con

stra

ints

(oth

er)

Ben

d ra

dius

Hel

ical

Ext

ensi

on S

prin

gsSi

mila

r in

mos

t way

s to

com

pres

sion

sprin

gsU

sual

ly w

ound

to b

e cl

osed

co

il at

zer

o fo

rce

Thus

a p

relo

ad is

requ

ired

to

stre

tch

any,

i.e.

y=

k(F-

F i )

Sprin

g ho

ok is

a so

urce

of

failu

re in

ben

ding

and

to

rsio

nN

o se

t is u

sed

One

coi

l not

con

side

red

activ

e

End

Hoo

k St

ress

esB

endi

ng st

ress

:

Tors

iona

l stre

ss:

Tors

iona

l Spr

ings

The

wire

in a

tors

iona

l spr

ing

is p

rimar

ily

in b

endi

ngSp

ring

cons

tant

is ro

tary

M=

kLo

adin

g sh

ould

act

to w

ind

up c

oil

Des

ign

proc

ess r

esem

bles

com

pres

sion

sp

rings

Com

pres

sion

Spr

ing

Des

ign-

-Fat

igue

Stat

ic d

esig

n al

so im

porta

nt b

ut d

etai

ls le

ft to

ex

ampl

eD

ata

avai

labl

e fo

r spr

ings

with

load

ing

from

zer

o to

som

e co

mpr

esio

n va

lue

Firs

t con

stru

ct (o

r fin

d) S

-N c

urve

Nex

t con

stru

ct M

od-G

oodm

an c

hart

App

ly lo

ad li

ne fo

r giv

en p

relo

ad a

nd d

esig

n st

ress

Find

fact

or o

f saf

ety

to fa

ilure

poi

ntD

etai

ls d

iscu

ssed

via

Mat

hCad

solu

tion

Goo

dman

Cha

rt fo

r Exa

mpl

e 13

-4

Hom

ewor

k 10

Due

11/

28/0

1In

text

: 13-

1, 1

3-13

(Mus

t see

web

pag

e fo

r st

artin

g va

lues

in d

esig

n an

d pr

oble

m

stat

emen

t cor

rect

ions

)