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KALLAM HARANADHAREDDY INSTITUTE OF TECHNOLOGY

Mechanical Engineering Department II B.Tech II Sem A/Y :2019-2020

Branch: ME (A&B) Sub: Design of Machine Members-I (C212)

Name of the Course Coordinator/Advisor: D.Srinivasulu

UNIT-I INTRODUCTION AND STRESSES IN MACHINE MEMBERS

1. Definition of Machine design and necessity

2. What is General Procedure in Machine Design and explain?

3. How do you classify machine design?

4. What factors should be considered in machine design? (OR) What are the basic

requirements of Machine design?

5. What are the General considerations in the design of machine elements?

6. What are the factors to be considered in the selection of materials for the machine

members?

7.Explain the desirable properties of engineering materials used in mechanical

engineering design.

8. How do you Selection of Materials for Engineering Purposes

9.Enumerate commonly used engineering materials and explain them

10. What are the classifications of Metals, their Alloys and explain?

11. What is the duralumin?

12. What are the commonly used limits and fits according to Indian standards?

13. What is meant by ‘hole basis system’ and ‘shaft basis system’?

14. A mild steel rod of 12 mm diameter was tested for tensile strength with the gauge

length of 60 mm. Following observations were recorded : Final length = 80 mm; Final

diameter = 7 mm; Yield load = 3.4 kN and Ultimate load = 6.1 kN. Calculate : 1. yield

stress, 2. ultimate tensile stress, 3. percentage reduction in area, and 4. percentage

elongation.

15. Calculate the tolerances, fundamental deviations and limits of sizes for the shaft

designated as 40 H8 / f7.

16. Write short notes on the following : 1.Working Stress 2. Factor of Safety 3.

Poisson's Ratio

17.A shaft is transmitting 97.5 kW at 180 r.p.m. If the allowable shear stress in the

material is 60 MPa, find the suitable diameter for the shaft. The shaft is not to twist more

that 1° in a length of 3 metres. Take C = 80 GPa.

18.Describe various types of theories of failure (OR) state and explain various theories

of failure under static loading (OR) Explain briefly the various theories of failure

19.The load on a bolt consists of an axial pull of 10 kN together with a transverse shear

force of 5 kN. Find the diameter of bolt required according to 1. Maximum principal

stress theory; 2. Maximum shear stress theory; 3. Maximum principal strain theory; 4.

Maximum strain energy theory; and 5. Maximum distortion energy theory. Take

permissible tensile stress at elastic limit = 100 MPa and poisson’s ratio = 0.3

20. A cylindrical shaft made of steel of yield strength 700 MPa is subjected to static

loads consisting of bending moment 10 kN-m and a torsional moment 30 kN-m.

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Determine the diameter of the shaft using two different theories of failure, and

assuming a factor of safety of 2. Take E = 210GPa and poisson's ratio = 0.25.

21. A mild steel shaft of 50 mm diameter is subjected to a bending moment of 2000N-m

and a torque T. If the yield point of the steel in tension is 200 MPa, find the maximum

value of this torque without causing yielding of the shaft according to 1. the maximum

principal stress; 2. the maximum shear stress; and 3. the maximum distortion strain

energy theory of yielding.

UNIT-II STRENGTH OF MACHINE ELEMENTS

1. What is meant by `stress concentration'? How do you take it into consideration in

case of a component subjected to dynamic loading?

2. Define theoretical stress concentration factor

3. Explain briefly about the causes of stress concentration

4. Describe the method to determine stress concentration factors

5. Explain the methods of reducing stress concentration

6. Define Fatigue Stress Concentration Factor

7. Define the notch sensitivity

8. Determine the maximum stress produced in a rectangular plate 50mm wide, 8 mm

thick with a central hole of 10mm diameter. It is loaded in an axial tension of 1 KN.

Assume stress concentration factor Kt =2.5

9. A flat plate is subjected to a tensile force of 5KN as shown in figure. Take FOS = 2.5,

ultimate stress = 200 N/mm2. Calculate the palte thickness. Assume Kt at sec A-A = 1.8,

Kt at sec B-B = 2.16.

10. A stepped shaft has maximum dia = 45mm, minimum dia = 30mm, fillet radius =

6mm, if the shaft is subjected to an axial load of 10KN. Find the maximum stress

induced. Assume Kt = 1.45

11. A stepped shaft has maximum dia =50mm, minimum dia = 25mm, fillet radius 5mm.

If the shaft is subjected to a twisting moment of 1500 N-m, find the maximum stress

induced. Assume Kt = 1.35

12. Write Short notes on Fatigue failure

13. What are the factors tobe considered while designing machine parts to avoid

fatique failure?

14. Define stress cycle

15. Write about the design for fluctuating stresses

16. Fatigue (or) Endurance Limit

17. Explain the S-N Curve and Draw S-N curve for mild steel and explain its

significance

18. Write , Gerber method, 2. Goodman method, and 3. Soderberg method. and state

its application to different type of loadings.

19. subjected to a flexural stress which fluctuates between + 300 MN/m2 and – 150

MN/m2. Determine the value of minimum ultimate strength according to 1. Gerber

relation; 2. Modified Goodman relation; and 3. Soderberg relation. Take yield strength

= 0.55 Ultimate strength; Endurance strength = 0.5 Ultimate strength; and factor of

safety = 2.

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20. A bar of circular cross-section is subjected to alternating tensile forces varying

from a minimum of 200 kN to a maximum of 500 kN. It is to be manufactured of a

material with an ultimate tensile strength of 900 MPa and an endurance limit of 700

MPa. Determine the diameter of bar using safety factors of 3.5 related to ultimate

tensile strength and 4 related to endurance limit and a stress concentration factor of

1.65 for fatigue load. Use Goodman straight line as basis for design.

21. Determine the thickness of a 120 mm wide uniform plate for safe continuous

operation if the plate is to be subjected to a tensile load that has a maximum value of

250kN and a minimum value of 100kN. The properties of the plate material are as

follows:

Endurance limit stress = 225MPa, and Yield point stress = 300MPa.The factor of safety

based on yield point may be taken as 1.5.

22. A steel rod is subjected to a reversed axial load of 180kN. Find the diameter of the

rod for a factor of safety of 2. Neglect column action. The material has an ultimate

tensile strength of 1070MPa and yield strength of 910MPa. The endurance limit in

reversed bending may be assumed to be one-half of the ultimate tensile strength.

Other correction factors may be taken as follows:

For axial loading = 0.7; For machined surface = 0.8 ; For size = 0.85 ; For stress

concentration = 1.0.

23. A circular bar of 500 mm length is supported freely at its two ends. It is acted upon

by a central concentrated cyclic load having a minimum value of 20 kN and a

maximum value of 50 kN. Determine the diameter of bar by taking a factor of safety of

1.5, size effect of 0.85, surface finish factor of 0.9. The material properties of bar are

given by : ultimate strength of 650 MPa, yield strength of 500 MPa and endurance

strength of 350 MPa.

24. A cantilever beam made of cold drawn carbon steel of circular cross-section as

shown in Fig., is subjected to a load which varies from – F to 3 F. Determine the

maximum load that this member can withstand for an indefinite life using a factor of

safety as 2. The theoretical stress concentration factor is 1.42 and the notch sensitivity

is 0.9. Assume the following values :

Ultimate stress = 550 MPa; Yield stress = 470 MPa; Endurance limit = 275 MPa

Size factor = 0.85;Surface finish factor= 0.89

25. A simply supported beam has a concentrated load at the centre which fluctuates

from a value of P to 4 P. The span of the beam is 500 mm and its cross-section is circular

with a diameter of 60 mm. Taking for the beam material an ultimate stress of 700 MPa, a

yield stress of 500MPa, endurance limit of 330MPa for reversed bending, and a factor

of safety of 1.3, calculate the maximum value of P. Take a size factor of 0.85 and a

surface finish factor of 0.9.

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UNIT-III RIVETED, WELDED JOINTS AND BOLTED JOINTS

1. What do you understand by the term riveted joint? Explain the necessity of such a

joint.

2. . What are the various permanent and detachable fastenings? Give a complete list

with the different

types of each category.

3. What is the material used for rivets?

4. Classify the rivet heads according to Indian standard specification

5. How do you classify the riveted joints?

6. What are the Important Terms Used in Riveted Joints

7. What is difference between Caulking and fullering? Explain with the help of neat

sketches

8. Explain various ways in which a riveted joint may fail

9. A double riveted lap joint is made between 15 mm thick plates. The rivet diameter

and pitch are 25 mm and 75 mm respectively. If the ultimate stresses are 400 MPa in

tension,320 MPa in shear and 640 MPa in crushing, find the minimum force per pitch

which will rupture the joint. If the above joint is subjected to a load such that the factor

of safety is 4, find out the actual stresses developed in the plates and the rivets.

10. Find the efficiency of the following riveted joints : 1. Single riveted lap joint of 6 mm

plates with 20 mm diameter rivets having a pitch of 50 mm. 2. Double riveted lap

joint of 6 mm plates with 20 mm diameter rivets having a pitch of 65 mm. Assume

Permissible tensile stress in plate = 120 MPa, Permissible shearing stress in rivets = 90

MPa, Permissible crushing stress in rivets = 180 MPa

11. A double riveted double cover butt joint in plates 20 mm thick is made with 25 mm

diameter rivets at 100 mm pitch. The permissible stresses are: t = 120 MPa; = 100

MPa; c = 150 MPa. Find the efficiency of joint, taking the strength of the rivet in

double shear as twice than that of single shear.

12. Explain the procedure for designing a longitudinal and circumferential joint for a

boiler.

13. A pressure vessel has an internal diameter of 1 m and is to be subjected to an

internal pressure of 2.75 N/mm2 above the atmospheric pressure. Considering it as a

thin cylinder and assuming efficiency of its riveted

Joint to be 79% calculate the plate thickness if the tensile stress in the material is not to

exceed 88 MPa. Design a longitudinal double riveted double strap butt joint with equal

straps for this vessel. The pitch of the rivets in the outer row is to be double the pitch in

the inner row and zig-zag riveting is proposed. The maximum allowable shear stress in

the rivets is 64 MPa. You may assume that the rivets in double shear are 1.8 times

stronger than in single shear and the joint does not fail by crushing. Calculate the

efficiency of the joint.

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14. Describe the procedure for designing a lozenge joint.

15. Two MS tie bars for a bridge structure are to be joined by means of a butt joint with

double straps. The thickness of the tie bar is 12 mm and carries a load of 400 KN.

Design the joint completely taking allowable stresses as 100 MPa in tension, 70 Mpa in

shear and 150 MPa in compression.

16. What is an eccentric riveted joint? Explain the method adopted for designing such

a joint?

17. A bracket in the form of a plate is fitted to a column by means of four rivets A,B, C

and D in the same vertical line, as shown in Fig. 9.33. AB = BC = CD = 60 mm. E is the

mid-point of BC. A load of 100 KN is applied to the bracket at a point F which is at a

horizontal distance of 150 m from E. The load acts at an angle of 30° to the horizontal.

Determine the diameter of the rivets which are made of steel having a yield stress in

shear of 240 MPa. Take a factor of safety of 1.5. What would be the thickness of the

plate taking an allowable bending stress of 125 MPa for the plate, assuming its total

width at section ABCD as 240 mm?

18. The bracket as shown in Fig. is to carry a load of 45 kN. Determine the size of the

rivet if the shear stress is not to exceed 40 MPa. Assume all rivets of the same size.

19. An eccentrically loaded lap riveted joint is to be designed for a steel bracket as

shown in Fig. The bracket plate is 25 mm thick. All rivets are to be of the same size.

Load on the bracket, P = 50 KN; rivet spacing, C = 100 mm; load arm, e = 400 mm.

Permissible shear stress is 65 MPa and crushing stress is 120 MPa. Determine the size

of the rivets to be used for the joint.

20. Advantages and Disadvantages of Welded Joints over Riveted Joints

21. What are Classification of Welding

22. Explain the welding process and types of welded joints

23.Explain Strength of Transverse Fillet Welded Joints

24. Explain Strength of Parallel Fillet Welded Joints

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25. A plate 100 mm wide and 10 mm thick is to be welded to another plate by means of

double parallel fillets. The plates are subjected to a static load of 80 kN. Find the length

of weld if the permissible shear stress in the weld does not exceed 55 MPa.

26. A plate 100 mm wide and 12.5 mm thick is to be welded to another plate by means

of parallel fillet welds. The plates are subjected to a load of 50 kN. Find the length of

the weld so that the maximum stress does not exceed 56 MPa. Consider the joint first

under static loading and then under fatigue loading.

Given data: Width = 100 mm ; Thickness = 12.5 mm ; P = 50 kN = 50 × 103N ;

= 56 MPa = 56 N/mm2

27. A plate 75 mm wide and 12.5 mm thick is joined with another plate by a single

transverse weld and a double parallel fillet weld as shown in Fig. 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.

28. A 50 mm diameter solid shaft is welded to a flat plate as shown in Fig. If the size of

the weld is 15 mm, find the maximum normal and shear stress in the weld.

29. A rectangular cross-section bar is welded to a support by means of fillet welds as

shown in Fig. Determine the size of the welds, if the permissible shear stress in the

weld is limited to 75 MPa.

30. What are Advantages and Disadvantages of Screwed Joints

31. What are Important Terms Used in Screw Threads

32. What are the Common Types of Screw Fastenings and explain?

33. Discuss about the bolts of uniform strength

34. Write short notes on Designation of Screw Threads (Thread standards)

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

1.5 N/mm2. The cylinder head is connected by 8 bolts having yield point 330 MPa and

endurance limit at 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 2, find the size of bolt required. The stiffness factor for copper gasket

may be taken as 0.5.

36. Explain the Bolted Joints under Eccentric Loading

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37. A bracket, as shown in Fig above, supports a load of 30 kN. Determine the size of

bolts, if the maximum allowable tensile stress in the bolt material is 60 MPa. The

distances are : L1 = 80 mm, L2 = 250 mm, and L = 500 mm.

Given data: W = 30 kN ; t = 60 MPa = 60 N/mm2 ; L1 = 80 mm ; L2 = 250 mm ;

L = 500 mm

38. For supporting the travelling crane in a workshop, the brackets are fixed on steel

columns as shown in Fig. The maximum load that comes on the bracket is 12 kN acting

vertically at a distance of 400 mm from 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.

39. A flanged bearing, as shown in Fig. is fastened to a frame by means of four bolts

spaced equally on 500 mm bolt circle. The diameter of bearing flange is 650 mm and a

load of 400 kN acts at a distance of 250 mm from the frame. Determine the size of the

bolts, taking safe tensile stress as 60 MPa for the material of the bolts.

40. what is the Gaskets and explain Locking Devices?

DMM-I UNIT-IV

KEYS, COTTERS, KNUCKLE JOINTS AND SHAFTS

1. What is the key? State its functions

2. Explain different types of keys with sketches

3. What are the considerations in the design of dimensions of formed and parallel key

having rectangular

cross-section ?

4. Design the rectangular key for a shaft of 50 mm diameter. The shearing and crushing

stresses for the key material are 42 MPa and 70 MPa. Assume Width of key, w = 16

mm,and thickness of key, t = 10 mm

5. A 45 mm diameter shaft is made of steel with a yield strength of 400 MPa. A parallel

key of size 14 mm wide and 9 mm thick made of steel with a yield strength of 340 MPa

is to be used. Find the required length of key, if the shaft is loaded to transmit the

maximum permissible torque. Use maximum shear stress theory and assume a factor

of safety of 2.

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6. What is the effect of keyway cut into the shaft ?

7. A 15 kW, 960 r.p.m. motor has a mild steel shaft of 40 mm diameter and the

extension being 75 mm. The permissible shear and crushing stresses for the mild steel

key are 56 MPa and 112 MPa. Design the keyway in the motor shaft extension. Check

the shear strength of the key against the normal strength of the shaft.

8. What is a cotter joint? Explain with the help of a neat sketch

9. Difference between keys and cotters

10. Why a single taper is provide in cotter and not an both sides?

11. Discuss the design procedure of spigot and socket cotter joint.

12. Describe the purpose of gib in cotter joint. What are the applications of cotter

joints?

13. What are the design procedure for gib and cotter joint for square rods

14 . Sketch two views of a knuckle joint and write the equations showing the strength of

joint for the most

probable modes of failure.

15. Design and draw a cotter joint to support a load varying from 30 kN in

compression to 30 kN in tension. The material used is carbon steel for which the

following allowable stresses may be used. The load is applied statically.

Tensile stress = compressive stress = 50 MPa ; shear stress = 35 MPa and crushing

stress = 90 MPa.

16. Design a sleeve and cotter joint to resist a tensile load of 60 kN. All parts of the joint

are made of the same material with the following allowable stresses : t

= 60 MPa ;

= 70 MPa ; and c = 125 MPa.

17. Design a gib and cotter joint as shown in Fig. to carry a maximum load of 35 kN.

Assuming that the gib, cotter and rod are of same material and have the following

allowable stresses : t = 20 MPa ; = 15 MPa ; and c

= 50 MPa

18. Design a knuckle joint to transmit 150 kN. The design stresses may be taken as 75

MPa in tension, 60 MPa in shear and 150 MPa in crushing.

Given data : P = 150 kN = 150 × 103 N ; t = 75 MPa = 75 N/mm2 ; = 60 MPa = 60

N/mm2 ; c = 150 MPa = 150 N/mm2

19. Design a knuckle joint for a tie rod of a circular section to sustain a maximum pull of

70 kN. The ultimate strength of the material of the rod against tearing is 420 MPa. The

ultimate tensile and shearing strength of the pin material are 510 MPa and 396 MPa

respectively. Determine the tie rod section and pin section. Take factor of safety = 6.

20. Distinguish clearly, giving examples between spindle, axle and shaft.

21. Discuss the various types of shafts and the standard sizes of transmissions shafts.

22. What type of stresses are induced in shafts ?

23. How the shaft is designed when it is subjected to twisting moment only ?

24. Define equivalent twisting moment and equivalent bending moment. State when

these two terms are

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used in design of shafts.

25. What do you understand by torsional rigidity and lateral rigidity.

26. A line shaft rotating at 200 r.p.m. is to transmit 20 kW. The shaft may be assumed to

be made of mild steel with an allowable shear stress of 42 MPa. Determine the

diameter of the shaft, neglecting the bending moment on the shaft.

Given data : N = 200 r.p.m. ; P = 20 kW = 20 × 103 W; = 42 MPa = 42 N/mm2

27. A solid shaft is transmitting 1 MW at 240 r.p.m. Determine the diameter of the shaft

if the maximum torque transmitted exceeds the mean torque by 20%. Take the

maximum allowable shear stress as 60 MPa.

28. Find the diameter of a solid steel shaft to transmit 20 kW at 200 r.p.m. The ultimate

shear stress for the steel may be taken as 360 MPa and a factor of safety as 8.If a hollow

shaft is to be used in place of the solid shaft, find the inside and outside diameter when

the ratio of inside to outside diameters is 0.5.

29. A pair of wheels of a railway wagon carries a load of 50 kN on each axle box,acting

at a distance of 100 mm outside the wheel base. The gauge of the rails is 1.4 m. Find

the diameter of the axle between the wheels, if the stress is not to exceed 100 MPa.

30. A solid circular shaft is subjected to a bending moment of 3000 N-m and a torque of

10 000 N-m. The shaft is made of 45 C 8 steel having ultimate tensile stress of 700 MPa

and a ultimate shear stress of 500 MPa. Assuming a factor of safety as 6, determine the

diameter of the shaft.

31. A shaft made of mild steel is required to transmit 100 kW at 300 r.p.m. The

supported length of the shaft is 3 metres. It carries two pulleys each weighing 1500 N

supported at a distance of 1 metre from the ends respectively. Assuming the safe value

of stress, determine the diameter of the shaft.

32. A shaft is supported by two bearings placed 1 m apart. A 600 mm diameter pulley

is mounted at a distance of 300 mm to the right of left hand bearing and this drives a

pulley directly below it with the help of belt having maximum tension of 2.25 kN.

Another pulley 400 mm diameter is placed 200 mm to the left of right hand bearing and

is driven with the help of electric motor and belt, which is placed horizontally to the

right. The angle of contact for both the pulleys is 1800 and μ = 0.24. Determine the

suitable diameter for a solid shaft, allowing working stress of 63 MPa in tension and 42

MPa in shear for the material of shaft. Assume that the torque on one pulley is equal to

that on the other pulley.

33. A steel solid shaft transmitting 15 kW at 200 r.p.m. is supported on two bearings

750 mm apart and has two gears keyed to it. The pinion having 30 teeth of 5 mm

module is located 100 mm to the left of the right hand bearing and delivers power

horizontally to the right. The gear having 100 teeth of 5 mm module is located 150 mm

to the right of the left hand bearing and receives power in a vertical direction from

below. Using an allowable stress of 54 MPa in shear, determine the diameter of the

shaft.

34. A mild steel shaft transmits 20 kW at 200 r.p.m. It carries a central load of 900 N and

is simply supported between the bearings 2.5 metres apart. Determine the size of the

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shaft, if the allowable shear stress is 42 MPa and the maximum tensile or compressive

stress is not to exceed 56 MPa. What size of the shaft will be required, if it is subjected

to gradually applied loads?

35. A horizontal nickel steel shaft rests on two bearings, A at the left and B at the right

end and carries two gears C and D located at distances of 250 mm and 400 mm

respectively from the centre line of the left and right bearings. The pitch diameter of

the gear C is 600 mm and that of gear D is 200 mm. The distance between the centre

line of the bearings is 2400 mm. The shaft transmits 20 kW at 120 r.p.m. The power is

delivered to the shaft at gear C and is taken out at gear D in such a manner that the

tooth pressure FtC of the gear C and FtD of the gear D act vertically downwards.

Find the diameter of the shaft, if the working stress is 100 MPa in tension and 56

MPa in shear. The gears C and D weighs 950 N and 350 N respectively. The combined

shock and fatigue factors for bending and torsion may be taken as 1.5 and 1.2

respectively.

36. A steel spindle transmits 4 kW at 800 r.p.m. The angular deflection should not

exceed 0.25° per metre of the spindle. If the modulus of rigidity for the material of the

spindle is 84 GPa, find the diameter of the spindle and the shear stress induced in the

spindle.

37. Compare the weight, strength and stiffness of a hollow shaft of the same external

diameter as that of solid shaft. The inside diameter of the hollow shaft being half the

external diameter. Both the shafts have the same material and length.

UNIT-V (DMM-I) SHAFT COUPLINGS

1. What is the shaft coupling and essential difference between a clutch and a coupling?

2. What are the various Purposes of a coupling?

3. What are the requirements of a good shaft coupling?

4. Classify the coupling and explain them

5. Write the applications of couplings

6. Difference between rigid and flexible couplings

7. Design procedure of Sleeve or muff coupling

8. Design procedure of Clamp or split-muff or compression coupling,

9. Design procedure of Un protected type flange coupling

10. Design procedure of protected type flange coupling

11. Design procedure of Marine type flange coupling

12. Design procedure of Bushed pin type coupling

13. Write short note on Oldham Coupling

14. Design procedure of universal coupling

15. Write short note on universal coupling.

16. Design and make a neat dimensioned sketch of a muff coupling which is used to

connect two steel shafts transmitting 40 kW at 350 r.p.m. The material for the shafts and

key is plain carbon steel for which allowable shear and crushing stresses may be taken

as 40 MPa and 80 MPa respectively. The material for the muff is cast iron for which the

allowable shear stress may be

assumed as 15 MPa.

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17. Design a clamp coupling to transmit 30 kW at 100 r.p.m. The allowable shear stress

for the shaft and key is 40 MPa and the number of bolts connecting the two halves are

six. The permissible tensile stress for the bolts is 70 MPa. The coefficient of friction

between the muff and the shaft surface may be taken as 0.3.

18 . Design a cast iron protective type flange coupling to transmit 15 kW at 900 r.p.m.

from an electric motor to a compressor. The service factor may be assumed as 1.35.

The following permissible stresses may be used :

Shear stress for shaft, bolt and key material = 40 MPa, Crushing stress for bolt and

key = 80 MPa, Shear stress for cast iron = 8 MPa. Draw a neat sketch of the coupling.

19. Design and draw a cast iron flange coupling for a mild steel shaft transmitting 90

kW at 250 r.p.m. The allowable shear stress in the shaft is 40 MPa and the angle of twist

is not to exceed 1° in a length of 20 diameters. The allowable shear stress in the

coupling bolts is 30 MPa.

20. The shaft and the flange of a marine engine are to be designed for flange coupling,

in which the flange is forged on the end of the shaft. The following particulars are to be

considered in the design :

Power of the engine = 3 MW

Speed of the engine = 100 r.p.m.

Permissible shear stress in bolts and shaft = 60 MPa

Number of bolts used = 8

Pitch circle diameter of bolts = 1.6 × Diameter of shaft

Find : 1). diameter of shaft ; 2). diameter of bolts ; 3). thickness of flange ; and 4).

diameter of flange. 5). Draw neat sketch of the coupling.

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

shaft transmitting 32 kW at 960 r.p.m. The overall torque is 20 percent more than mean

torque. The material properties are as follows :

(a) The allowable shear and crushing stress for shaft and key material is 40 MPa and 80

MPa respectively.

(b) The allowable shear stress for cast iron is 15 MPa.

(c) The allowable bearing pressure for rubber bush is 0.8 N/mm2.

(d) The material of the pin is same as that of shaft and key.

Draw neat sketch of the coupling.

22. A torque of 3000 Nm is to be transmitted between two shafts by using a universal

coupling. Shaft is transmitting torque only. Find the diameter of the shaft and pin. Take

shear stress for shaft is 50 MPa and shear stress for pin is 30 MPa. If angle of inclination

of shafts is 150 and in plane angle driving shaft with shaft fork is 200 . Find the speed of

output shaft and speed of input shaft is 1200 rpm.

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DMM-I UNIT-VI MECHANICAL SPRINGS

1. Define spring. What is the purpose of mechanical springs?

2. Write the function of spring in machine

3. Generally, how the springs are classified ? Indicate the different types of springs by

sketches and give minimum two practical applications of each

4. What are types of material for helical springs

5. Explain the following terms of the spring : (i) Free length; (ii) Solid height; (iii)

Spring rate; (iv) pitch; and

(v) Spring index;

6. Draw the end connections for compression helical springs

7. Explain the design of helical compression springs with a neat sketch (or) Discuss the

stresses in Helical springs of circular wire

8. Explain what you understand by A.M. Wahl’s factor and state its importance in the

design of helical

springs?

9. Write the energy storage capacity of springs

10. Explain one method of buckling of compression springs

11. Explain the surging (spring surge) and critical frequency

12. How does surge in springs eliminated

13. What do you understand by full length and graduated leaves of a leaf spring? Write

the expression for

determining the stress and deflection in full length and graduated leaves.

14. Explain the utility of the centre bolt, U-clamp, rebound clip and camber in a leaf

spring.

14. A compression coil spring made of an alloy steel is having the following

specifications : Mean diameter of coil = 50 mm ; Wire diameter = 5 mm ; Number of

active coils = 20. If this spring is subjected to an axial load of 500 N ; calculate the

maximum shear stress (neglect the curvature effect) to which the spring material is

subjected.

15. A helical spring is made from a wire of 6 mm diameter and has outside diameter of

75 mm. If the permissible shear stress is 350 MPa and modulus of rigidity 84 KN/mm2,

find the axial load which the spring can carry and the deflection per active turn.

16. A closely coiled helical spring is made of 10 mm diameter steel wire, the coil

consisting of 10 complete turns with a mean diameter of 120 mm. The spring carries an

axial pull of 200 N. Determine the shear stress induced in the spring neglecting the

effect of stress concentration. Determine also the deflection in the spring, its stiffness

and strain energy stored by it if the modulus

of rigidity of the material is 80 KN/mm2.

17. Derive the expressions for springs in series and springs in parallel.

D.SrinivasuluReddy, M.Tech, (Ph.D) Associate Professor, Mechanical Engineering Dept.,

K.H.I.T, Guntur.