Design Chapter 1 2 & 16 mark q&A

8/10/2019 Design Chapter 1 2 & 16 mark q&A

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Design of various types of springs, optimization of helical springs, rubber springs,

Design of flywheels considering stresses in rims and arms, for engines and punching

machines.

UNIT IV

D!I"N #$ N%"& !T#%IN" '(NT!

)*%T+*

. -hat is meant by semi elliptical leaf springs /(*&01UN 2345 /N#V0D6

235

The spring consists of number of leaves, which are held together by U- clips. The long leaf

fastened to the supported is called master leaf. Remaining leaves are called as graduated

leaves.

2. Define the term 7fluctuation of energy7. /(*&01UN 2345

The variations of energy above and below the mean resisting torque line are called fluctuationof energy.

8. -hat is a spring /N#V0D6 2325

A spring is an elastic member, which deflects, or distorts under the action of load and regains

its original shape after the load is removed.

4. !tate any two functions of springs. /N#V0D6 2325

i.To measure forces in spring balance, meters and engine indicators. ii.To store energy.

9. -hat are the various types of springs /(*&01UN 2325

i.Helical springs ii.piral springs iii.!eaf springs iv."isc spring or #elleville springs

:. 6lassify the helical springs. /(*&01UN 2325

a.$lose % coiled or tension helical spring. b.&pen %coiled or compression helical spring.

;. Define < 'eaf springs /(*&01UN 2325

A leaf spring consists of flat bars of varying lengths clamped together and supported at both

ends, thus acting as a simply supported beam.

=. Define < >elleville !prings /N#V0D6 235

They are made in the form of a cone disc to carry a high compressive force. 'n order toimprove their load carrying capacity, they may be stac(ed up together. The ma)or stresses are

tensile and compressive.

?. -hat is spring inde@ /65 /N#V0D6 235

The ratio of mean or pitch diameter to the diameter of wire for the spring is called the spring

inde*.

3. -hat is pitch /N#V0D6 235

The a*ial distance between ad)acent coils in uncompressed state.

. -hat are the reAuirements of spring while designing /N#V0D6 235a.pring must carry the service load without the stress e*ceeding the safe value.


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b.The spring rate must be satisfactory for the given application.

2. -hat are the end conditions of spring /N#V0D6 235

a.+lain end. b.+lain and ground end c.quared end d.quared and ground end.

8. -hat is bucBling of springs /(*&01UN 235The helical compression spring behaves li(e a column and buc(les at a comparative small

load when the length of the spring is more than times the mean coil diameter.

4. -hat is surge in springs /(*&01UN 235

The material is sub)ected to higher stresses, which may c.se early fatigue failure. This effect

is called as spring surge.

9. -hat is a laminated leaf spring /N#V0D6 235

'n order to increase, the load carrying capacity, number of flat plates are placed and below the

other.

:. -hat is nipping of laminated leaf spring /N#V0D6 235

+restressing of leaf springs is obtained by a difference of radii of curvature (nown as nipping.

;. -hat are the various application of springs /(*&01UN 235

The springs are used in various applications, they are

a.Used to absorb energy or shoc(s e.g. shoc( absorbers, buffers, e.t.c.

b.To apply forces as in bra(es clutches, spring-loaded valves, e.t.c.

c.To measure forces as in spring balances and engine indicators

d.To store energy as in watches

=. Define free length. /(*&01UN 235

/ree length of the spring is the length of the spring when it is free or unloaded condition. 't is

equal to the solid length plus the ma*imum deflection or compression plus clash allowance.

!f 0 solid length 1 2ma* 1 3.45 26a*

?. Define spring inde@. /(*&01UN 235

pring inde* $ is defined as the ratio of the mean diameter of the coil to the diameter of the

wire.

$ 0"7d

23. Define spring rate /stiffness5. /N#V0D6 235The spring stiffness or spring constant is defined as the load required per unit deflection of

the spring. 80 97y 9here 9-load y-deflection

2. Define pitch. /(*&01UN 235

+itch of the spring is defined as the a*ial distance between the ad)acent coils in uncompressed

state. 6athematically +itch 0 free length7 n-4

22. -hat are the points to be taBen into consideration while selecting the pitch of the

spring /(*&01UN 235

The points ta(en into consideration of selecting the pitch of the springs are

a.The pitch of the coil should be such that if the spring is accidentally compressed the stressdoes not increase the yield point stress in torsion.


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b.The spring should not be close up before the ma*imum service load is reached.

28. Define active turns. /(*&01UN 235

Active turns of the spring are defined as the number of turns, which impart spring action

while loaded. As load increases the no of active coils decreases.

24. Define inactive turns. /N#V0D6 2335

'nactive turns of the spring is defined as the number of turns which does not contribute to the

spring action while loaded. As load increases number of inactive coils increases from 3.5 to 4

turn.

29. -hat are the different Binds of end connections for compression helical springs

/N#V0D6 2335

The different (inds of end connection for compression helical springs are

a.+lain ends b.:round ends c.quared ends d.:round ; square ends

2:. -rite about the eccentric loading of springs /N#V0D6 2335'f the load acting on the spring does not coincide with the a*is of the spring, then spring is

said to be have eccentric load. 'n eccentric loading the safe load of the spring decreases. and

the stiffness of the spring is also affected.

2;. -hat are the disadvantages of using helical spring of non+circular wiresE3 0 L 1 >

Lnergy at O 0 L 1 > % > 0 L 0 Lnergy at A

/rom above, we see that the energy is ma*imum at L and minimum at #.

6a*imum energy0 L 1 > and minimum energy0 L % ?>

The ma*imum fluctuation of energy,

P L 06a*imum energy % 6inimum energy0JL 1 > % JL % ?> 0 I mm>

0I D >I.? 0 4> N3 -m

The fluctuation of speed is Q 4.5 of the mean speed, therefore total fluctuation of speed,

B4% B>0 ? of mean speed 0 3.3? B.

$oefficient of fluctuation of speed 0 JB4% B>7 B 0 3.3?.

m 06ass of the flywheel rim

6a*imum fluctuation of energy JPL,


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6ass of the flywheel rim Jm

5E?0 A D C " D 0 t>D C D 4.IE D I>33 0 45N E> t>

t>05E?745N E> 0 3.33?5?

t 03.35N m 0 5N. 0 E3 mm

b 0 t 0 D E3 0 >3 mm

2. * helical spring is made from a wire of :mm diameter and has outside diameter

of ;9mm.If the permissible shear stress is 893(pa and modulus of rigidity

=4LN0mm2 , find the a@ial load which the spring can carry and the deflection per

active turn. /N#V0D6 25


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8. Design a spring for a balance to measure 3 to 333N over a scale of length =3mm.

the spring is to be enclosed in a casing of 29mm diameter .The appro@imate

number of turns is 83.the modulus of rigidity is =9LN0mm2 .*los calculate the

ma@imum shear stress induced /*pril 2, N#V0D6 35

4. Design a helical compression spring for a ma@imum load of 333N for a

deflection of 29mm using the value of spring inde@ as 9. The ma@imum


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permissible shear stress for spring wire is 423(pa and the modulus of rigidity is

=4LN0mm2. /N#V0D6 3, 3?5

9. Design a close coiled helical compression spring for a service load ranging form

2293N to 2;93N.the a@ial deflection of the spring for the load range is :mm.

*ssume a spring inde@ of 9.The permissible shear stress intensity is 42m3(pa

and modulus of rigidity , " H =4 LN0mm2 .Neglect the effect of stress

concentration .draw a fully dimensioned sBetch of the spring ,showing the details

of the finish of the end coils /*pril 35


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:. Design and draw a valve spring of a petrol engine for the following operating

conditions

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Design Chapter 1 2 & 16 mark q&A