Part A

1. Describe the material properties of hardness, stiffness and resilience.

2. What are the methods used to improve fatigue strength?

3. A shaft of 70mm long is subjected to shear stress of 40 MPa and has an

angle of twist equal to 0.017 radian. Determine the diameter of the shaft.

Take G = 80 Gpa.

4. What is the main use of woodruff keys?

5. What is a gib? Why is it provided in a cotter joint?

6. A helical spring of rate 12 N/mm is mounted on the top of another spring of

rate 8 N/mm. Find the force required to give a deflection of 50mm.

7. What is the purpose of flywheel that is used in an IC engine?

8. What is meant by life anti-friction bearings?

9. What are the essential requirements in an end face seal?

10. State the two types of eccentric welded connections.

11. Differentiate the stress distribution in a bar subjected to axial force and

beam subjected to bending.

12. For Ductile material, which of the strength is considered for designing a

(a) component subjected to static loading.

( b) component subjected to fatigue loading.

13. Why a hallow shaft has greater strength and stiffness than solid shaft of

equal weight?

14. What types of stresses are developed in the key?

15. State any two advantages of welded joints over rivted joints.

16. What is the meaning of bolt M24 x 2 ?

17. State any two important applications of leaf spring.

18. Sate the following: (i) leverage (ii) load on the lever.

19. What is the advantages of Teflon which is used for bearings?

20. What is the purpose of flywheel that is used in an IC engine?

21. What are the factors to be considered for deciding the magnitude of factor

of safety?

22. List out the methods of reducing stress concentration factor.

23. State Castigliones theorem.

24. What is the difference b/w rigid and flexible coupling?

25. Why are through bolts not preferred in assembly applications?

26. Which factor causing residual stress in welded joints? How are they

relieved?

27. Define spring index.

28. What is Wahl factor and why is it required?

29. Differentiate sliding contact and rolling contact bearings.

30. In what respect the flywheel differs from the governor.

Part B

1. A cast-iron link, as shown in figure, is to carry a load of 20 KN. If the tensile

and compressive stresses in the link are not to exceed 25 MPa and 80 MPa

respectively, obtain the dimensions of the cross section of the link at the

middle of its length.

Space for figure

2. A hot rolled steel shaft is subjected to a torsional moment that varies

from 330 Nm clockwise to 110 Nm counter clockwise and an applied

bending moment at a critical section varies from 440 Nm to -220 Nm.

The shaft is of uniform cross section and no keyway is present at the

critical section. Determine the required shaft diameter. The material has

an ultimate strength of 550 MPa and yield strength of 410 MPa. Take

the endurance limit as half the ultimate strength, factor of safety of 2,

size factor of 0.85 and a surface finish factor of 0.62.

3. A hoisting drum 0.5 m in diameter is keyed to a shaft which is supported

in two bearing and driven through a 12:1 reduction ratio by an electric

motor. Determine the power of the driving motor, if the maximum load

of 8 kN is hoisted at a speed of 50 m/min and the efficiency of the drive

is 80%. Also determine the torque on the drum shaft and the speed of

the motor in r.p.m. Determine also the diameter of the shaft made of

machinery, steel, the working stresses of which are 115 MPa in tension

and 50 MPa in shear. The drive gear whose diameter is 450 mm is

mounted at the end of the shaft such that it overhangs the nearest

bearing by 150mm. The combined shock and fatigue factors for bending

and torsion may be taken as 2 and 1.5 respectively.

4. Design a rigid flange coupling to transmit a torque of 250 Nm b/w two

co-axial shafts. The shaft is made of alloy steel, flanges out of cast iron

and bolts out of steel. 4 bolts are used to couple the flanges. The shafts

are keyed to the flange hub. The permissible stresses are given below:

Shear stress on shaft = 100 MPa

Bearing or crushing stress on shaft = 250 MPa

Shear stress on keys = 100 MPa

Bearing stress on keys = 250 MPa

Shearing stress on cast iron = 200 MPa

Shearing stress on bolts = 100 MPa

After designing the various elements, make a neat sketch of the

assembly indicating the important dimensions. The stresses developed

in the various members may be checked if thumb rules are using for

fixing the dimensions.

5. For supporting the travelling crane in a workshop the brackets are fixed on

steel columns as shown in figure. The maximum load that comes on the

bracket is 12kN acting vertically at a distance of 400 mm form the face of

the column. The vertical face of the bracket is secured to a column by four

bolts, in two rows (two in each row) at a distance of 50 mm from the lower

edge of the bracket. Determine the size of the bolts if the permissible value

of the tensile stress for the bolt material is 84 MPa. Also find the cross-

section of the arm of the bracket which is rectangular.

Space for figure

6. Find the maximum shear stress induced in the weld of 6 mm size when a

channel, as shown in fig. is welded a plate and loaded with 20 kN force at a

distance of 200 mm.

Space for figure

7. A helical compression spring made of oil tempered carbon steel is

subjected to a load which varies from 400 N to 1000 N. The spring index is 6

and the design factor of safely is 1.25. If the yield stress in shear is 770 MPa

and endurance stress in shear is 350 MPa, find: (i) size of the spring wire (ii)

diameter of the spring (iii) Number of turns of the spring and (iv) Free

length of spring. The compression of the spring at the maximum load is 30

mm. The modulus of rigidity for the spring.

8. A single cylinder double acting steam engine delivers 185 kW at 100 r.p.m.

The maximum fluctuation of energy per revolution is 15 % of the energy

developed per revolution. The speed variation is limited to 1 percent either

way from the mean. The mean diameter of the rim are 2.4m. Design and

draw two views of the flywheel.

9. Design a journal bearing for a centrifugal pump for the following data. Load

on the journal=20000N, speed of the journal=900 r.p.m. type of oil is SAE

10, for which the absolute viscosity at 55c = 0.17 N/m-s; Ambient

temperature of oil = 15. 5c maximum bearing pressure for the pump = 1.5

N/mm. Calculate also mass of the lubricating oil required for artificial

cooling if rise of temperature of oil be limited to 10c. Heat dissipation

coefficient = 1232 W/m/c.

10. Determine the dimensions of an I section connecting rod for a petrol

engine from the following data:

Diameter of the piston = 110mm

Mass of the reciprocating parts = 2kg

Length of the connecting rod from centre to centre = 325 mm

stroke length = 150 mm

R.P.M = 1500 with possible over speed of 2500

Compression ratio = 4:1

Maximum explosion pressure = 2.5 N/mm.

11. (i) Explain the following with mathematical expressions. Maximum

principle stress theory; Von-mises stress theory.

(ii) A cost iron pulley transmits 12 kW at 330 rpm. The diameter of the

pulley is 1.3 m and it has four straight arms of elliptical cross section in

which the major axis is twice the minor axis. Determine the dimensions of

the arm if the allowable bending stress is 18 MPa.

12. A shaft of 760 mm length is simply supported at its ends. It is subjected to

a central concentrated cyclic load that varies from 12 to 36 kN. Determine

the diameter of the shaft assuming a factor of 2, size correction factor of

0.8 and surface correction factor of 0.85. The material properties are

ultimate strength = 500 MPa; yield strength = 280 MPa; and endurance

limit = 250 MPa. Fatigue stress concentration factor = 1.5.

13. Design a Knuckle joint to with stand a tensile load of 70 KN using steel with

the following permissible stresses

( in tension ) = 60 MPa

( in crushing ) = 72 MPa

T ( in shear ) = 48 MPa

14. Design a bushed-pin type of flexible coupling to connect a pump shaft to a

motor shaft transmitting 30 kW at 900 rpm. The overall torque is 15% more

than mean torque. The material allowable properties are as follows:

( in crushing for shaft and key material ) = 80 MPa

T ( in shear for shaft and key material ) = 40 MPa

T ( in shear for cast iron ) = 15 MPa

Bearing pressure for rubber bush = 0.8 MPa

Material of the pin as same as that of shaft and key. Draw the sketch of the

coupling.

15. A steam engine of effective diameter 300 mm is subjected to a steam

pressure of 1.5 MPa. The cylinder head is connected by 8 bolts having yield

point 330 MPa and endurance limit of 240 MPa. The bolts are tightened

with an initial preload of 1.5 times the steam load. A soft copper gasket is

used to make the joint leak-proof. Assuming a factor of safety equal to 2,

find the size of bolt required. The stiffness factor for copper gasket may be

taken as 0.5.

16. (i) A plate 75mm wide and 12.5 mm thick is joined with another plate by a

single transverse weld and a double parallel fillet weld as shown fig. 1. The

maximum tensile and shear stresses are 70 MPa and 56 MPa respectively.

Find the length of each parallel fillet weld, if the joint is subjected to both

static and fatigue loading.

Stress concentration factor for transverse weld is 1.56 and for parralled

fillet weld is 2.7

Space for figure

(ii) A welded joint as shown in fig.2 is subjected to an eccentric load of 2

kN. Find the size of weld, if the maximum shear stress in the weld is 25

MPa

Space for figure

17. Design a spring for spring loaded safety valve for the following condition:

Operating pressure = MPa

Diameter of the valve seat = 110 mm

Design shear stress for the spring = 360 MPa

G = shear modulus = 82 GPa

The spring is to be kept in the casing of 130 mm inner diameter and 400

mm long. The spring should be at maximum lift of 6 mm when the pressure

is 1.08 MPa

18. A bearing for an axial flow compressor is to carry a radial load of 2500 N

and thrust of 1500 N. The service imposes light shock and the bearing will

be in use for 40 hours/week for 5 years. The speed of the shaft is 1000 rpm.

Select suitable ball bearing for the purpose and give the required tolerances

on the shaft and the housing. Diameter of the shaft is 50 mm.

19. A punching press pierces 30 holes per minute in a plate using 12 kN-m of

energy per hole during each revolution. Each piercing takes 35% of the time

needed to make one revolution. The punch receives power through a gear

reduction unit which in turn is fed by a motor driven belt pulley 750 mm

diameter and turning at 240 rpm. Find the power of the electric motor if

overall efficiency of the transmission unit is 80%. Design a cast iron

flywheel to be used with the punching machine for a coefficient if

fluctuation of speed is 0.05, if the space considerations limits the maximum

diameter to 1.3 m.

Allowable shear stress in the shaft material = 48 MPa

Allowable tensile stress for cast iron = 5 MPa

Density of cast iron = 7200 Kg/m.

20. A hollow shaft is required to transmit 600 kW at 110 rpm the maximum

torque being 20% greater than the mean. The shear stress is not to exceed

63 MPa and twist in a length of 3 meters not to exceed 1.4 degrees. Find

the external diameter of the shaft. If the internal diameter to the external

diameter is 3/8. Take modulus of rigidity as 84 MPa.

21. A machine component is subjected to fluctuating stress that varies from 40

to 100 N/mm. The corrected endurance limit stress for the machine

component is 270 N/mm. The ultimate tensile strength and yield strength

of material are 600 and 450 N/m respectively. Find the factor of safety

using: (i) Gerber theory; (ii) Soderberg line; (iii) good man line and (iv) Also,

find factor of safety of safety against static failure.

22. The layout of a shaft carrying two pulleys 1 and 2 and supported on two

bearing A and B is shown in figure. The shaft transmits 7.5 kW power at 360

rpm form pulley 1 to pulley 2. The diameters of pulley 1 and 2 are 250 and

500 mm respectively. The masses of pulley 1 and 2 are 10 and 30 kg

respectively. The belt tensions act vertically downward and the ratio of belt

tensions on the tight side to slack side for each pulley are 2.5:1. The shaft is

made of plain carbon steel 40 C8 ( syt = 380 N/mm) and the factor of safety

is 3. Estimate suitable diameter of shaft. If the permissible angle of twist is

0.5 per meter length, calculate the shaft diameter on the basis of torsional

rigidity. Assume G = 79300 N/mm.

Space for figure

23. It is required to design a bushed pin type flexible coupling to connect the

output shaft of an electric motor to the shaft of a centrifugal pump. The

motor delivers 20 kW power at 720 rpm. The starting torque of motor can

be assumed to be 150% of the rated torque. Design the coupling and

specify the dimension of its components.

24. A safety valve, 50 mm in diameter is to blow at a pressure of 1.5 MPa. It is

help on its seat by means of a helical compression spring, with an initial

compression spring, with an initial compression of 25 mm. The maximum

lift of valve is 10 mm. the spring index can be taken as 6. The spring is made

of patented and cold drawn steel wire with ultimate strength of 1500

N/mm and modulus of rigidity of 81370 N/mm. the permissible shear

stress for the spring wire should be taken as 30% of the ultimate tensile

strength. Design the spring and calculate: (i) wire diameter (ii) mean coil

diameter (iii) number of active turns; (iv) total number of turns; (v) solid

length of spring; (vi) free length of spring; (vii) pitch of the coil.

25. A right angled bell crank lever is designed to raise a load of 5 kN at the

short arm end. The length of the short and long arms are 100 and 450 mm

respectively. The lever and pins are made of 30C8 ( syt = 400 N/mm) and

the factor of safety is 5. The permissible cross section and the ratio of width

to thickness is 3:1. The length to diameter ratio of fulcrum pin is 1.25:1.

Calculate (i) the diameter and the length of fulcrum pin (ii) the shear stress

in the pin (iii) the dimensions of the boss of the lever at the fulcrum and (iv)

the dimensions of the cross section of the layer. Assume that the arm of

bending moment on the lever extends up to the axis of the fulcrum.

26. A single row deep grove ball bearing is subjected to a radial force of 8 kN

and a thrust force of 3 kN. The shaft rotates at 1200 rpm. The expected life

L10th of the bearing of the shaft is 75 mm. select a suitable ball bearing for

this application.

27. The tuning moment diagram of a multi-cylinder engine is drawn with a

scale of (1mm = 1) on the abscissa and ( 1mm = 250 N-m) on the ordinate.

The intercepted areas b/w the torque developed by the engine and the

mean resisting torque of the machine, taken in order from one end are -

350, +800, +600, +900. -550, +450 and -650mm. the engine is running at a

mean speed of 750 rpm and the coefficient of speed fluctuations is limited

to 0.02. a rimmed flywheel made of grey cast iron FG 200 ( p = 7100 kg/m)

is provided. The spokes, hub and shaft are assumed to contribute 10% of

required moment inertia. The rim has rectangular cross section and ratio of

width to thickness is 1.5. determine the dimensions of rim.