Ch. 1 Design against static load - Top Engineering · PDF fileCh. 1 Design against static load . ... applications of the Knuckle joint. (ii) Define and draw ... to sustain a tensile

GTU Paper Analysis (New Syllabus)

Machine Design and Industrial Drafting (2141907) Department of Mechanical Engineering Darshan Institute of Engineering & Technology

Ch. 1 Design against static load

Sr. No. Questions

Jun

– 15

Jan

- 16

1. Explain Mohr's circle diagram for principal stresses. 4

2. Differentiate between (1) Torsional Shear Stress & Transverse Shear Stress

(2) Compressive Stress & Crushing Stress 7

3. Name the different theories of failures of mechanical components made of ductile material. Explain the maximum shear stress theory giving conservative zone. 7

4. Explain in brief Coulomb Mohr Theory of failure of the mechanical components. 7

Examples

1. Determine the principals Stresses for 35mm rod diameter supported at end act as cantilever beam which is subjected to an axial compressive load of 15KN & twisting moment of 250Nm. 4

GTU Paper Analysis (Old Syllabus)

Machine Design & Industrial Drafting (131902) Department of Mechanical Engineering Darshan Institute of Engineering & Technology

Ch-1 Design Against Static Load

Sr. No. Questions

Jun

- 10

Dec

- 10

Jun

- 11

Dec

– 1

1

May

- 12

Jan

- 13

May

- 13

Nov

- 13

Jun

- 14

1. What is stress concentration? Explain methods to relieve stress concentration? Explain any two stresses with simple sketches.

04 04 04 04 07

2. Define factor of safety and state the important factors affecting the factor of safety.

02 03 04

3. Explain the importance of selection of materials in machine design. 02

4. Define following: (1) Proof Resilience (2) Preferred number (3) Principle stress

03

5.

Answer the following (Any THREE) : ( i ) Define factor of safety. List and explain the factors affecting Selection of it. ( ii ) Explain the various steps of machine design process. ( iii ) Explain the following materials giving their applications: FG200, 16Ni3Cr2, 40C8. ( iv ) Distinguish clearly between bending and bearing stress. (v) List and explain the factors affecting selection of suitable materials.

07

6. (a) Explain the following terms with neat sketches. 1) Tensile stress 2) Compressive stress 3) Principle Stress 4) Bearing pressure (b) Classify the different types of load & Explain each In brief.

07



7. Differentiate between (with neat sketch): 1) crushing and compressive stresses 2) torsional and transverse shear stress

04

8. Define the following : 1) proof resilience 2) Preferred Number 3)Factor of Safety 4)Residual stress 5) principle stress

05

Examples

1.

Determine the thickness of a 120 mm wide uniform plate for safe continuous operation of the plate is to be subjected to tensile load that has maximum value of 250 KN and minimum value of 100 KN. The properties of the plate material are as follows: Endurance limit=225 N/mm2, Yield point stress=300 N/mm2, Factor of safety=1.5

05

2.

A mild steel link is as shown in Fig. 2, which is subjected to a tensile load of 80 kN. Find the b. The permissible tensile stress is 70 MPa.

07

3.

1. Determine the minimum size of a circular hole that can be punched in a M.S. plate, 5 mm thick and having ultimate shear strength of 300 MPa. Take compressive strength of punch as 360 MPa. 2. Define machine design. Explain different types of design problems Stating suitable examples.

07

4. A wall bracket with rectangular cross section is shown in. The depth 07



of the cross-section is twice of the width. The force P acting on the bracket at 300 to the horizontal is 5 KN. The bracket is made gray cast iron FG 200 (Sut = 200N/mm2) and factor of safety = 3.5 Determine the dimensions of the cross section of the bracket.



Ch. 2 Design of Cotter and Knuckle joints.

Sr. No. Questions

Jun

– 15

Jan

- 16

1. No questions asked.

Examples

1. Design a knuckle joint to transmit 75 kN. The design stresses may be taken as 75 MPa in tension, 60 MPa in shear and 150 MPa in compression.

7

2. Design and draw a neat sketch of spigot rod for the cotter joint using the following data:

Axial load 30 KN Tensile stress = 50 N/mm2 Crushing Stress = 90 N/mm2 And Shear Stress = 35 N/mm2.

7



Ch-2 Design of Cotter and Knuckle Joints

Sr. No. Questions

Jun

- 10

Dec

- 10

Jun

- 11

Dec

– 1

1

May

- 12

Jan

- 13

May

- 13

Nov

- 13

Jun

- 14

Dec

– 1

4

1. Explain procedure to design cotter joint. 07

2. (i) State the different applications of the Knuckle joint.

(ii) Define and draw sketches of: Key, cotter. 04

3. Write design procedure for design of a socket and spigot joint, which may be subjected to an axial load. Write the design equations for different failure criteria. Draw sketches for the same.

07

4. Define cotter, Why taper is provided in a cotter? And What is the purpose of clearance in Cotter Joints? 04 05

Examples

1.

Two rods of 50mm diameter are to be joined by a cottered joint, with thickness of cotter as 12.5mm. If the joint is withstand an axial pull of 6000KN find the various dimensions required. The permissible stresses are 300 MPa in tension, 200 MPa in shear and 450 MPa crushing.

07

2. Design a knuckle joint to connect two mild steel bars under a tensile load of 25 kN. The allowable stresses are 65 MPa in tension, 50 MPa in shear and 83 MPa in crushing. Standard diameter of solid bars are

10



20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40 mm. Check failure of knuckle pin in shear, failure of rod end & forked end in tension, shearing and crushing

3.

Design a socket and spigot joint to resist a tensile load of 28 KN. All the parts of the joint are made from same material with following allowable stresses: σt =50 N/mm², σc =60 N/mm², τ =35 N/mm² , σb =50 N/mm²

10

4.

It is required to design a cotter joint to connect two steel rods of equal Diameter. The permissible stresses for the rods, spigot end and socket end are σt =96 N/mm2, σc = 134 N/mm2 & τ = 45 N/mm2.

For cotter, σt =80 N/mm2, τ = 40 N/mm2. Each rod is subjected to an

axial Tensile force of 80 KN. Calculate following dimensions:

1. Diameter of spigot 2. Width & thickness of cotter 3. Thickness of socket collar

09

5.

Design a knuckle joint for a tie rod of a circular section to sustain a max. Pull of 70kN. 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 F.S. =6.

07

6. Design a knuckle joint to connect two circular mild steel rods which are Subjected to a tensile load of 63 kN. The allowable stresses are 80 MPa in tension, 56 MPa in shear and 80 MPa in crushing.

07

7. It is required to design a knuckle joint to connect two circular mild steel rods subjected to an axial tensile load of 50KN. The design stresses are 80 MPa in tension and crushing and 40 MPa in shear for

07



all the parts.

8.

It is required to design a cotter joint to connect two steel rods of equal diameter. Each rod is subjected to an axial tensile load of 50 kN. The Permissible stresses are 67 MPa in tension, 34 MPa in shear and 134 MPa in crushing for all the parts.

07

9. A Knuckle joint is required to sustain a tensile load of 30 kN. Design the joint, if the permissible stresses are σt = 55 MPa, τ = 42 MPa, σc = 70 MPa.

07

10. Design a knuckle joint to connect two rods subjected to tensile force of 50 KN. The rods and pin are made of plain carbon steel 30C8. The permissible stresses are σt = σc = 80 MPa and τ = 40 MPa.

07



Ch. 3 Design and Analysis of Levers.

Sr. No. Questions

Jun

– 15

Jan

- 16

1. Explain with neat sketch three basic types of lever stating their practical examples. 4

2. Why taper is provided on cotter? What is its normal value? State its applications. 3

Examples

1.

A bell crank lever is to be designed to raise a load of 6 kN at short arm end. The arm lengths are 160 mm and 550 mm. The permissible stresses for lever and pin materials in shear and tension are 60 MPa and 90 MPa respectively. The bearing pressure on pin is to be limited to 13 MPa. Assume lever cross section as t×4t and fulcrum pin length as 1.25 times pin diameter.

7

2.

Design a Bell crank lever having load arm 500mm and effort arm of 150mm respectively. The maximum load to be raise is 4500N. Use the following allowable stresses for the pin and lever material.

Tensile Stress = 75 N/mm2 Shear Stress= 60 N/mm2 & Bearing pressure = 10 N/mm2 10



Ch. 3 Design and Analysis of Lever

Sr. No. Questions

Jun

- 10

Jun

- 11

Dec

– 1

1

May

- 12

May

- 13

Nov

- 13

Jun

- 14

Dec

– 1

4

1. Explain the general procedure usually adopted in the design of a lever.

07

2. Explain three basic types of levers with practical examples 04 03 04 07

3. Why a boss is generally needed at the fulcrum of the levers. 02

4. For a lever, define : (1)leverage (2)arm of the lever (3)mechanical advantage

03

5. Differentiate between simple and compound lever. 04

6. What is lever? Explain the principle on which it works. 04

7. Explain clearly the necessity of providing bosses on the lever at pin Locations.

04

Examples

1.

Design a bell crank lever to apply a load of 5 kN (vertical) at the end A of an horizontal arm of length 400 mm. The end of the vertical arm C and the fulcrum B are to be fixed with the help of pins inside forked shaped supports. The end A is itself forked. Determine the cross-section of the arms and the dimensions of the pins. The lever is to have mechanical advantage of 4 with a shorter vertical arm BC. The ultimate stresses in shear and tension for the lever and pins are 400 MPa and 500 MPa respectively. The allowable bearing pressure for the pins is 12 N/mm2. Assume a factor of safety as 4 and the cross-section of the lever as rectangular with depth (b) as three times the

10



thickness (t).

2.

Design a lever of a lever loaded safety valve based on following data: Steam pressure acting on the valve = 1.2 MPa Valve diameter = 60 mm. Width to thickness ratio for lever = 3: 1 Length to diameter ratio for pins = 1.25 : 1 The material used is forged steel with t σt =80 MPa, τ =50 MPa, σc =100 MPa, Pb = 20 MPa The lever has a rectangular cross section. The distance between the fulcrum and the dead weights on lever is 800 mm and distance between the fulcrum and the pin connecting the spindle of the valve to the lever is 100 mm. Calculate: (i) the length and the diameter of the pin connecting the valve spindle to the lever (ii) the lever cross sectional dimensions

07

3.

A bell crank lever is to be designed to raise a load of 15 kN at the short arm end. The arm lengths are 150 mm and 500 mm. The permissible stresses for lever and pin materials in shear and tension are 60 MPa and 90 MPa respectively. The bearing pressure on the pin is to be limited to 12 MPa. Assume the lever cross section as t x 4t and fulcrum pin length as 1.25 times pin diameter.

09

4.

The lever of a lever loaded safety valve shown in Fig. 4. The diameter of the valve is 80 mm and valve has to blow off at a pressure of 1.25 MPa. The permissible stress in tension, shear and crushing are 70 MPa, 20 MPa and 50 MPa respectively. The permissible bearing pressure for the pin may be taken as 20 MPa. Design the pins and the lever; assume rectangular cross section of the lever with height equal to three times the thickness.

07



5.

Design a rocker arm lever having equal arms of 160 mm length inclined at 1350 for an exhaust valve of a gas engine subjected to a maximum force of 2500 N at roller end. Consider – I cross section 6t x 2.5t x t size (where t = thickness of web and flange) for lever. The permissible stresses for the lever material are 80MPa in tension and design bearing pressure is pin 6 MPa for pin.

07

6.

Design a right angled bell crank lever having one arm 500 mm & the other 150 mm long. The load of 5 kN is to be raised acting on a pin at the end of 500 mm arm & the effort is applied at the end of 150 mm arm. The lever consists of steel forgings, turning on a point at the fulcrum. The permissible stresses for the pin & lever are 84 MPa in tension & compression & 70 MPa in shear, the bearing pressure on the pin is not to exceed 10 N/mm2.

10 07



Ch. 4 Design of Beams

Sr. No. Questions

Jun

– 15

Jan

- 16

1. Differentiate between beam and column. Enlist different types of beams. 3

2. Distinguish between beams, columns and strut giving suitable examples. 7

3. State and explain the CASTIGLIANO’S theorem and determine the magnitude of strain energy stored for a cantilever beam subjected to torsional moment T having span length L and cross Sectional area A. 7



Ch. 5 Design of Columns

Sr. No. Questions

Jun

– 15

Jan

- 16

1. Explain Euler's formula along with its applicability and limitations. 3

2. What is slenderness ratio of column? How crippling stress is decided by using Euler’s equations? Give the validity of the equation.

7

3. What are the limitations of Euler’s equation how they are overcome? Explain the two empirical formula with the name.

7

Examples

1.

A connecting rod of uniform rectangular cross-section having b/d ratio of 1.5 and length 100 mm is used for supporting an axial compressive load of 20 kN. It is hinged at both ends and made of alloy steel with ultimate compressive strength of 700 MPa and modulus of elasticity of 210 GPa. Considering factor of safety 4, determine cross-sectional dimensions using appropriate of Euler's and Johnson's formulae.

7

2.

A 300 mm long alloy steel rod is used to support an axial compressive load of 65 kN. One end of rod is fixed and the other end is free to support load. Assuming compressive yield strength 550 N/mm2 and modulus of elasticity 210 GPa, determine diameter of rod by buckling consideration. Use Rankine's formula with Rankine constant α = 1/7500. Take factor of safety 3.5.

7



Ch. 6 Design of Shaft, Keys and Couplings

Sr. No. Questions

Jun

– 15

Jan

- 16

1. Explain Axle, Spindle, Counter shaft and line-shaft with their examples 4

2. What is ASME code for shaft design? 3

3. Derive strength equations of sunk key based on shear and compression failures. 4

4. Discuss factors to be considered while selecting type of key. 3

5. Compare the weight, strength and rigidity of a hollow shaft of same external diameter as that of solid shaft, Both the shaft are made of same material. Assume that the diameter ratio for the hollow shaft as 0.6

7

Examples

1.

A hoisting drum 0.5 m in diameter is keyed to shaft which is supported in two bearings and driven through 12:1 reduction ratio by an electric motor. Determine power of driving motor, if maximum load of 8 kN is hoisted at speed of 50 m/min with 80% efficiency. Also determine torque on drum shaft and speed of motor in rpm. Determine also diameter of shaft for which working stresses are 115 MPa in tension and 50 MPa in shear. The drive gear whose diameter is 450 mm is mounted at end of shaft such that it overhangs nearest bearing by 150 mm. The combined shock and fatigue factors for bending and torsion may be taken as 2 and 1.5 respectively.

7

2.

A bushed pin type flexible coupling is used to transmit 10 kW power at 720 rpm. The design torque is 150% of rated torque. The keys have square cross-section. The permissible stresses are: For shaft and key material, τ = 66.67 N/mm2, σc = 200 N/mm2; For pin material, τ = 35 N/mm2, σt = 133 N/mm2; For flange material τ = 16.67 N/mm2. The permissible bearing pressure for rubber bushes is 1 N/mm2. The number of bushes is 4.

Design the bushed pin flexible coupling.

7

3. Design a split muff coupling to transmit 30 KW power at100 rpm, using the following data. 7



Number of bolts = 4, allowable shear stress for shaft and key = 40N/mm2, allowable tensile stress for the blots = 70N/mm2. Take co-efficient of friction = 0.3.



Ch. 6 Design of Shaft, Keys and Couplings

Sr. No. Questions

Jun

- 10

Dec

- 10

Jun

- 11

Dec

– 1

1

May

- 12

Jan

- 13

May

- 13

Nov

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Jun

- 14

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– 1

4

1. Answer the following: (i)Differentiate in between rigid and flexible coupling. (ii)What is critical speed of shaft?

04

2. Show that square key is equally strong in shearing and crushing. 04 05

3. What are the basic functions of the key? What is splined shaft? 04

4. Explain with neat sketch, design procedure of coupler. 04 07

5.

Suggest suitable ferrous material for the following parts stating the special Property which make it more suitable for use in manufacturing. 1. A shaft subjected to variable torsional and bending load 2. Valve 3. Machine tool bed 4. Keys (used for fastening) 5.Automobile cylinder block 6. Dies

04

6. What is ASME code for shaft design? 02 04

7. Discuss the effect of bearing pressure intensity & clearance provided between two faces of couplings in bushed pin type flexible coupling.

04

8. State & Explain the various criteria on which shaft are designed? 04

9. Explain purpose & requirement of shaft coupling. 03

10. State and explain the failures of shafts stating the reasons. 04

11. Compare the strengths of square key and rectangular key. What is 04



splined shaft? Explain the design of splined shaft.

12. Draw a neat sketch of a protected type flanged coupling and write the Design procedure with the design equations for different failure criteria.

07

13. Explain different types of keys with its applications. 07

14. State the difference between shaft, axle and spindle. 07

15. Attempt the following: (Any two) (i) How are the hollow shafts are beneficial over the solid shafts? (ii) State the reasons for failures of shafts? (iii) Define – Shaft, Axle ,Spindle

04

16. Differentiate between flexible coupling and rigid coupling? State the different applications of coupling?

04

17. A hollow shaft has greater strength and stiffness than solid shaft of equal weight. Explain.

04

18. Explain critical speed of shaft 04

19. Explain different types of keys with its applications 04

20. Explain functions and classification of shaft. 07

Examples

1.

The lay shaft driven by pulley ‘D’ from an electric motor is shown in Fig. Another belt drive from pulley ‘C’ is running a compressor. The permissible Shear stress of the shaft material is 85.5 N/mm2. The belt tensions for pulley C are T3 = 1500N, T4 = 600N. The shock and fatigue factors are: Kb=1.75 and Kt=1.25. The ratio of belt tension for pulley ‘D’ = 3.5, Diameter of pulley C=150mm, Diameter of pulley D = 480mm. Determine the diameter of the shaft.

10



2.

Design a protective type cast iron flange coupling for a shaft transmitting 15 KW power at a speed of 720 rpm. The permissible stresses are: For the shafts, keys, and bolts material , Permissible tensile stress (σt) = 133.33 MPa Permissible compressive stress (σc) = 200 MPa Permissible shear stress (τ ) = 66.67 MPa For flanges material, Permissible shear stress (τ ) = 16.67 MPa

10

3. Determine the diameter below which the angle of twist of a shaft and not the maximum stress, is the controlling factor in design of solid shaft in torsion. The allowable shear stress is 56 MPa and the maximum allowable twist is ¼ degree per meter. Take G = 84 MPa.

06

4. Compare the weight, strength and rigidity of a hollow shaft of same external diameter as that of solid shafts, both the shafts are made of same material. Assume that diameter ratio for the hollow shaft is di/do = 0.6

06

5. A flexible coupling as shown in fig 4, is used to transmit 15 KW power at 100 rpm. There are six pins and their pitch circle diameter is 200 mm. The length of pin in contact with the left hand flange, the gap between the two flanges and the length of bush in contact with the

06



right hand flange are 23, 5 and 35 mm respectively. The permissible shear and bending stress in the pin are 35 N/mm2 and 152 N/mm2 respectively. The permissible pressure for the rubber bush is 1 N/mm2. Calculate: 1) pin diameter by shear & bending consideration 2) O.D of the rubber bush.

6.

Design a cast iron flange coupling for a mild steel shaft transmitting 90 Kw at 250 rpm. The allowable shear stress in the shaft is 40 MPa and the angle of twist is not to exceed 1 degree in a length of 20 diameters. The allowable shear stress in the coupling bolts is 30 MPa. Take width of key = shaft diameter/4 & thickness of key = shaft diameter/6. Assume no. of bolts = 4.

07 07

7. A shaft transmits 75 kw power at 300 rpm load is gradually Applied. It is also subjected to B.M. of 500 N-M, shear stress in shaft material

10



should not exceed 40 N/mm2. Shaft must not twist more than 20 per meter length. Modulus of rigidity of shaft material is 0.8 105 N/mm2. Find the diameter of solid shaft. If the shaft is chosen is hollow with inside to outside diameter ratio = 0.5, Find the size of the hollow Shaft. What is the percentage saving in material by using hollow shaft instead of solid shaft?

8.

The armature shaft of a 40 kW, 720 r.p.m. electric motor mounted on two bearings are as shown in Fig.no.1.the total magnetic pull on the armature is 7 kN and it is assumed to be uniformly distributed over a length of 700 mm midway between the bearings. The shaft is made-up of steel with an ultimate tensile strength of 770 MPa and yield strength of 580 MPa. Determine the shaft diameter using ASME code if, kb = 1.5 and kt = 1.0 Assumed that the pulley is keyed to the shaft.

07

9.

A 600 mm diameter pulley transmits 16 kW power at a speed of 400 rpm. Pulley is cantilever at a distance of 200 mm from the nearest bearing. The weight of the pulley is 1500 N. It is driven by a horizontal belt drive. The co-efficient of friction between belt and pulley is 0.3 and the angle of lap 1800. Take the fatigue and shock factors as Kb = 2.0 and Ks = 1.5.Determine the shaft diameter.

07

10.

Design a cast iron split muff coupling to transmit a power of 10 kW at 250 rpm. Consider an overload of 25%. The allowable shear stress in the shaft and key is 36 MPa and for the muff 16 MPa. Take the co-efficient of friction 0.3 and the tensile strength of the high tensile bolts 150 MPa.

07

11.

A line shaft is driven by means of a motor placed vertically below it. The pulley on the line shaft is 1.5 meter in diameter and has belt tensions 5.4 kN and 1.8 kN on the tight side and slack side of the belt respectively. Both these tensions may be assumed to be vertical. If the pulley be overhang from the shaft, the distance of the centre line of the pulley from the centre line of the bearing being 400 mm, find the diameter of the shaft. Assuming maximum allowable shear stress of

10



42 MPa.

12.

Design a muff coupling to transmit 30 kW at 100 rpm. The allowable shear stress for the shaft and key is 40 MPa and the number of bolts connecting the two halves are 6. 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. Take width of key = Shaft diameter/4 and thickness of key = Shaft diameter/6.

09

13.

A belt driven C.I pulley of 0.9 m diameter overhangs the bearing by 0.2 m as shown in figure-3. The pulley is driven from the bottom by a belt. The angles of lap and tension on tight side are 180° and 2600 N respectively. The weight of pulley is 600 N. Assume co-efficient of friction between pulley and belt is 0.25. Shaft is made up of 30C8. yt =400 N/mm², ut =500 N/mm²Determine the shaft diameter according to ASME code. Take Ks=1.0, Kb=1.5.

07

14.

Design and draw a rigid type cast iron flange coupling for a steel shaft transmitting 15 KW at 200 rpm and having an allowable shear stress of 40 KN/mm². The maximum torque is 25% greater than the full load torque. The working stress in the bolt should not exceed 30 KN/mm². Assume that the same material is used for shaft and key and that the crushing stress is twice the value of its shear stress. The shear stress for cast iron is 14 KN/mm².

10

15.

The shaft and the flange of a marine engine are to be designed for flange coupling in which the flange is larger at the end of the shaft. Power of the engine = 3mw Speed of the engine = 100r.p.m. Permissible shear stress in bolts and shafts = 60N/mm2 No. of bolts used = 8 Pitch circle dia. Of bolts = 1.6 × dia. Of shaft Find : (1) Dia. Of shaft (2) Dia. Of bolt (3) Thickness and dia. Of flange.

07



16. A steel spindle transmits 4 Kw at 800 r.p.m. The angular deflection should not exceed 0.250 per metre of the spindle. If the modulus of rigidity for the material of the spindle is 84x103 N/mm2. Find the dia. Of spindle and the shear stress induced in the spindle.

07

17.

A 45mm diameter shaft is made of steel with a yield strength of 400 N/mm2. A parallel key of size 14 mm wide and 9 mm thick made of steel with a yield strength of 340 N/mm2 is to be used. Find the required length of key, if the shaft is loaded to transmit the max. permissible torque. Use max. shear stress theory and assume F.O.S. = 2

07

18

A horizontal shaft AD supported in bearings at A and B and carrying pulleys at C and D is to transmit 75 kW at 500 r.p.m. from drive pulley D to off-take pulley C, as shown in Fig :

1. Calculate the diameter of shaft. 2. The data given is P1 = 2 × P2 (both horizontal), Q1 = 2 Q2

(both vertical), radius of pulley C = 220 mm, radius of pulley D = 160 mm, allowable shear stress = 45 MPa.

10

19

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 1.70. 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 Standard shaft diameter: 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40 mm.

10



Take number of bolts are 3.

20 Find the diameter of a solid shaft to transmit 30kw at 230rpm.The shear stress is 50MPa.If a hollow shaft is to be used in place of solid shaft , find the inside and outside diameter when the ratio of inside to outside diameter is 6.8.

07



Ch. 7 Design of Threaded joints

Sr. No.

Questions

Jun

– 15

Jan

- 16

1. Differentiate between power screw and threaded joint. 4

2. Define Pitch, Lead, Nominal diameter and Core diameter for power screw. 4

3. What do you mean by bolt of uniform strength? Explain with neat sketch. 3

4. Draw a neat sketch of turn buckle used for tie rods, giving design procedure. 7

Examples

1. The nominal diameter of a triple threaded square screw is 50 mm, while pitch is 8 mm. It is used with a collar having outer diameter of 100 mm and inner diameter of 65 mm. The coefficient of friction at thread surface as well as at collar surface can be taken as 0.15. The screw is used to raise a load of 15 kN. Using uniform wear theory for collar friction, calculate: (i) Torque required to raise load, (ii) Torque required to lower load and (iii) Force required to raise load, if applied at a radius of 500 mm.

7

2. A bracket is bolted to column by 6 bolts arrange in two column. The distance between bolts along the row is 75mm and along the column 50mm. The joint is subjected to maximum eccentric force of 50KN acting at 150mm away from the centre of column. Taking allowable stress in the bolt as 150N/mm2, Determine the size of each bolt.

7



Ch. 8 – Design of Welded & Riveted Joint

Sr. No. Questions

Jun

– 15

Jan

- 16

1. Draw neat sketches of double V-Butt weld, single transverse fillet weld, single V-Butt weld and T-weld. 4

2. Draw neat sketch of Double riveted zig-zag butt joint with all terminology. 4

Examples

1. Two steel plates, 120 mm wide and 12.5 mm thick, are joined together by means of double transverse fillet welds. The maximum tensile stress for plates and welding materials should not exceed 110 N/mm2. Find required length of weld, if strength of weld is equal to strength of plates.

3

2.

Find the value of P for joint shown in Figure 1, based on a working shear stress of 100 MPa for rivets. Each of four rivets is of 20 mm diameter.

3. A solid rectangular bar of 100mm width and 150mm depth is welded to vertical column by means of fillet weld all around. The joint is subjected to 25KN at distance of 500mm from the plane of weld. Determine throat thickness using allowable stress of weld is 75N/mm2.

7



Ch. 8 – Design of Welded & Riveted Joint

Sr. No. Questions

Jun

- 10

Dec

- 10

Jun

- 11

Dec

– 1

1

May

- 12

Jan

- 13

May

- 13

Nov

- 13

Jun

- 14

Dec

– 1

4

1. Write types of failure in riveted joint. 02 04 03 03 04

2. What is self-locking and over-hauling of power screw? Why the efficiency of self-locking square threaded screw is less than 50%?

06 04 05 04 06 07

3.

Explain various failures of riveted joints. Explain the following terms related to riveted joints.

1) Pitch 3) Margin

2) Diagonal pitch

07 06 06

4. State the types of welded joints & mention the stresses produced in welds in each of joints and explain the general design procedure to design the welded joints

07

5. How will you select the material for screw and nut while designing power screw?

03

6. Explain the different types of threads used in power screw stating their applications.

03

7. What do you mean by eccentric loaded welded joint? Write the detail design procedure for designing such a joint.

07

8. What do you understand by overhauling of screw? 05

9. What are the advantages of welded joint over riveted joint? 02



10. Why are square threads preferable to V threads for power transmission?

03

11. Explain caulking & fullering in terms of riveted joint. 04

12. Derive an equation for torque calculation for lifting the load in power screws. 07

Examples

1.

A shaft of rectangular cross-section 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 N/mm2.

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2.

A triple threaded power screw, used in a screw jack, has a nominal diameter of 50 mm and a pitch of 8 mm. The threads are square and the length of nut is 48 mm. The screw jack is used to lift a load of 7.5 KN. The coefficient of friction at the threads is 0.12 and collar friction is negligible. Calculate: (i) the principal shear stress in the screw body, (ii) the transverse shear stresses in the screw and the nut, (iii) the unit bearing pressure. State whether the screw is self-locking or not.

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3. Explain the important terminology of riveted joints and find the efficiency of the double riveted lap joints with zig-zag riveting is to be designed for 13 mm thick plates. Assume 80 MPa. 60 MPa and 120

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MPa in tension, Shear and crushing respectively. Also calculate pitch of rivets.

4.

1. A circular shaft, d in diameter, is welded with annular fillet having throat thickness of t. shaft is subjected to bending moment only. Determine the moment of inertia of annular fillet weld.

2. Fig.2 shows 12 mm thick plates loaded by the forces of 100 KN applied eccentrically. Determine the required lengths L1 & L2 of the fillet welds so that they will be equally stressed in shear. Take working stress in shear for side fillets to be equal to 80 N/mm2

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5.

A bracket is to be attached to a wall with the help of six rivets. The different arrangements in which the bracket can be attached to the wall with these rivets are shown in fig. 3. The maximum allowable stress in shear is 60 N/mm2. Determine the way in which the rivets should be arranged so that the design is economical. The bracket is required to support a load of 90 KN with an eccentricity of 200 mm. also determine the diameter of rivet for the selected arrangement.

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6.

The screw shown in fig.5 is operated by a torsional moment applied at the lower end. The nut is loaded and prevented from turning by guides. The outside diameter of the screws is 50 mm, pitch of 8 mm and the thread is acme triple start. The coefficient of friction of the threads is 0.15. Assume the friction in ball bearing as negligible. If the torsional moment Mt is 45 Nm.

1) Determine the load which could be raised

2) Would the screw be overhauling?

3) Determine the average bearing pressure between the screw and nut thread surfaces.

08



7.

Design a double riveted butt joint with two cover plates for the longitudinal seam of a boiler shell 1.5 m in diameter subjected to a steam pressure of 0.95 N/mm2. Assume joint efficiency as 75%, allowable tensile stress in the plate 90 MPa, Compressive stress 140 MPa & shear stress in the rivet 56 MPa.

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8.

An eccentrically loaded lap riveted joint is to be designed for a steel bracket as shown in fig.-1. The bracket plate is 25 mm thick. All rivets are to be of same size, load on the bracket P = 50 KN, rivet spacing c = 100 mm, load arm e = 400 mm, permissible shear stress is 64 MPa, and crushing stress is 120 MPa. Determine the size of the rivets to be used for the joint.

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9. Design a bottle type screw jack for lifting a load of 150 KN (Only screw & nut) and having maximum lift of 300 mm. Select proper material & stresses.

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10.

A welded joint has to support a load of 80 kN. Suggest a suitable size of fillet weld if the safe shear stress for the weld material is 80 MPa.

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11.

A bracket is subjected to a load of 32 KN which is joined to a structure by means of 8 numbers of rivets as shown in Fig. 1. Find the size of the rivets if the permissible shear stress is 80 MPa.

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12. A bracket is fillet welded to a structure as shown in Fig. 3, which is subjected to a load of 50 kN. Find the size of weld required if allowable shear stress is not to exceed 75 MPa.

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13.

Design and draw a turnbuckle for a capacity of 40 kN., which is used for adjusting tension in a v-belt drive of a machine tool. The permissible stresses for rods and nut are 80 MPa in tension, 50 MPa in shear and 80 MPa in crushing.

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14.

The lead screw of a lathe machine has single start trapezoidal threads of 52 mm nominal diameter and 8 mm pitch. The screw is required to exert an axial force of 2 kN in order to drive the tool carriage, during turning operation. The thrust is carried on a collar of 100 mm outer diameter and 60 mm inner diameter. The values of co-efficient of friction at the screw threads and the collar are 0.15 and 0.12 respectively. The lead screw rotates at 30 rpm. Calculate

(i) The power required to drive the lead screw.

(ii) The efficiency of the screw.

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15. A circular shaft, 75 mm in diameter, is welded to the support by means of a circumferential fillet weld. It is subjected to a torsional moment of 3000 N-m. Determine the size of weld, if the maximum shear stress in

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the weld is not to exceed 70 N/mm2.

16.

A bolt of diameter d is enlarged near its head to a diameter D. The head is cylindrical having diameter D1 and thickness T as shown in figure-1. The bolt when fixed in a structure having 6 mm plate thickness t , takes a tensile load of P=30 KN. Determine the dimensions d, D, D1 of the bolt using design stresses for the material of bolt as: ts=60 N/mm², cs =50 N/mm², t =35 N/mm²

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17.

Design a double riveted, double strap, chain type butt joint for plates having 10mm thickness. Also find efficiency of the joint. Take ts =95 N/mm², cs =155 N/mm², t =80 N/mm²

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18 A welded joint as shown in figure-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 N/mm².



20

A double riveted double cover butt joint in plates 20mm thick is made with 25mm dia. Rivets at 100mm pitch. The permissible stress are ft=120 N/mm2, Shear stress= 100 N/mm2, fc= 150 N/mm2. Find the Efficiency of joint, taking the strength of the rivets in double shear as twice than that of single shear.

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21

The lead screw of a lathe has Acme threads of 50mm outside dia. And 8 mm pitch. The screw must exert an axial pressure of 2500 N in order to drive the tool carriage. The thrust is carried on a collar 110 mm outside dia. And 55 mm inside dia. And the lead screw rotates at 30 r.p.m.

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22 Calculate required height of the nut for simple screw jack from the following data. (1)The load to be lifted W is 150KN. (2) Compressive stress Ϭc=125/mm2 (3) Bearing pressure 18N/mm2 for nut.

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23. A bracket is welded to the side of a column and carries a vertical load P, as shown in Fig 3. Evaluate P so that the maximum shear stress in the 10 mm fillet welds is 80 MPa.

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24.

A plate, 60mm wide and 80mm thick. It is welded with another plate by means of single transverse and double parallel fillet welds. Find the length of each parallel fillets if allowable tensile and shear stress in the weld material are 80 and60Mpa respectively.

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25. Determine the ratio of torque required to raise and lower the load from the following data. Load=20KN, Pitch=8mm, Dia.Of screw=40mm,coefficient of friction=0.1

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Ch. 9 Introduction of Limits, Fits and Tolerances

Sr. No. Questions

Jun

– 15

Jan

- 16

1. Define Basic size, Tolerance and Deviation. 3

2. What are the parameters used for surface roughness measurement? Explain any two. 4

3. What is magnitude of tolerance? Give the list of 6 manufacturing methods along with the recommended tolerance grade.

7

4. Explain with the help of neat sketch the terminology used in relation with the tolerances. 7

Examples

1. In bush and pin assembly, pin of 30 mm diameter rotates in a bush. The tolerance for pin is 0.025 mm while for bush is 0.04 mm. If allowance is 0.1 mm, determine dimensions of pin and bush considering hole-basis system.

3



Ch. 9 Introduction of Limits, Fits and Tolerances

Sr. No. Questions

Jun

- 10

Dec

- 10

Jun

- 11

Dec

– 1

1

May

- 12

Jan

- 13

Nov

- 13

Jun

- 14

Dec

– 1

4

1. What is tolerance and transition fit? 02

2. Explain the machining symbol with all parameter. 02

3. What is fit and explain types of fits with neat sketch also state application of each.

04

4. Explain surface roughness symbols & importance of it. Differentiate between assembly drawing & detail drawing.

07 04 04 04

5. Differentiate between hole basis system & shaft basis system with necessary sketches.

04 04

6. Give symbol for straightness, flatness, perpendicularity, cylindricity, symmetry & angularity.

03

7. Write briefly about fits and tolerances used in design. 04

8. Define limits, fits, and tolerance. 03 03

9. Explain the machining symbol with all parameter. 03

10. Explain “Shaft base system” and “Hole base system” with necessary examples.

07

Examples

1. In bush and pin assembly, pin of 30 mm diameter rotates in a bush. The tolerance for pin is 0.025 mm while for bush is 0.04 mm. If allowance is 0.1 mm, determine dimensions of pin and bush considering hole-basis system.

Documents

Ch. 1 Design against static load - Top Engineering · PDF fileCh. 1 Design against static load . ... applications of the Knuckle joint. (ii) Define and draw ... to sustain a tensile