1. Name the various sources of stress concentration in machine elements.

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3 TWO MARKS QUESTIONS 1. Name the various sources of stress concentration in machine elements. 2. What is meant by resilience of a body? 3. What are the factors to be considered for the selection of materials for the design of machine elements? 4. What do you mean by eccentric loading? 5. Name the various materials used for design of machine components. 6. What do you mean by eccentric loading? 7. Define the following properties of a material (a) Ductility (b) Creep 8. What is meant by endurance limit? 9. What are the various phase of design process? 10. State St.Venant theory of failure. 11. With sketch show any two ways of reducing stress concentration factor. 12. What factors should be considered in machine design? 13. What is the difference between ductility and malleability? 14. What is S-N diagram? 15. Define ultimate stress. 16. Define factor of safety.

4 18. Name the theories of failure suitable for ductile and brittle materials. 12 MARKS QUESTIONS 1. Explain design process with neat diagram. 2. Explain following failure theories in details. a) Maximum strain energy theory. b) Maximum principal stress theory. 3. Explain the following theories of failure: (a) Maximum principal stress theory (b) Maximum Shear theory (c) Distortion energy theory 4. State and discuss the various theories of failure. 5. Drive Soderberg s equation and state its application to different types of loadings. 6. (a) State and explain any two engineering materials. (4) (b) State and explain maximum strain theory. (8) 7. A shaft as shown in figure is subjected to a bending load of 3kN, Pure torque of 1000 N-m and axial pulling of 15 kn, calculate the stresses at A and B.

5 8. The load on a bolt consists of an axial pull of 10kN together with a transverse shear force of 5kN Find the diameter of bolt required according to (a)maximum principal stress theory (b) maximum shear stress theory. 9. A machine component is subjected to a flexural stress which fluctuates between +300MN/m 2 strength and 150MN/m 2. Determine the value of minimum ultimate 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 = A leaf spring in an automobile is subjected to cyclic stresses such that, the average stress is 160 MPa and the variable stress is 450 MPa. The material properties are: Ultimate strength = 150 MPa, yield strength = 350 MPa, endurance limit = 270 MPa. Estimate, under what factor of safety, the spring is working by (i) Goodman method and (ii) Soderberg method. 11. A mass of 500 kg falls through a distance h at the middle of a simply supported 4m long beam. Determine the value of h so that the maximum stress induced in the beam is 150 MPa. Take the modulus of beam section as 2.5 x 10 5 mm 3 and second moment of area as 12 x 10 6 mm (a) Determine the thickness of a 120mm wide uniform plate for safe continuous operation if the plate is to be subjected to a tensile load that has a maximum value

6 of 250kN and a minimum value of 100kN. The properties of the plate material are as follows. Endurance limit stress is 225 MPa and yield point may be taken as 1.5. (8) (b) What is factor of safety? List the factors to be considered while deciding the factor of safety. (4) 13.(a) A hollow shaft of 40mm outer diameter and 25mm inner diameter is subjected to a twisting moment of 120N-m, simultaneously, it is subjected to an axial thrust of 10kN and a bending moment of 80N-m. Calculate the maximum compressive and shear stresses. (10) (b) Define the terms equivalent torque and equivalent moment. (2) 14. A cantilever rod circular cross-section made of cold drawn. Steel 35C8(S ut = 550 N/mm 2, S yt = 320 N/mm 2 and S e = 275/mm 2 ) is shown in figure 1. It is subjected to a load which varies from-100 N to N. The surface finish factor and size factor are 0.9 and 0.8 respectively. The theoretical stress concentration factor and notch sensitivity at the fillet are 1.4 and 0.9 respectively. If the factor of safety is 2, determine d of the rod for infinite life by (a) Goodman method (b) Soderberg method (c)modified good man method 15. Determine the wall thickness of a cylindrical vessel closed at both ends, according to a) Maximum shear stress theory, b) Maximum distortion energy theory, and c) Maximum strain theory. The data are: Internal

7 pressure = 20 N/mm 2, Internal diameter of the vessel = 300 mm, Allowable tensile stress = 120 N/mm 2, Poisson s ratio = A hot rolled steel shaft is subjected to a torsional load varying form 300 N-m clockwise to 150 N-m counter clockwise and to a bending moment at a critical section varying from 400 N-m positive to 200 N-m negative. The shaft has uniform cross section and no keyway is present at the critical section. Determine the required shaft diameter assuming s y = 400 N/mm 2 and factor of safety = (a) Define Direct shear and torsional shear. (4) (b) Determine maximum stress induced in the shaft when transmitting 22 kw at 420 Rpm.The diameter of the shaft is 40mm. Take stress concentration into account. 18. A hot rolled steel shaft having s u = 600 MN/m 2, s y = 450 MN/m 2, s e = 300 MN/m 2 is subjected to a variable moment which varies between +300 to 200 Nm and a variable torque which varies between 250Nm to 150 Nm neglecting any stress concentration factor, determine the diameter of the shaft to have a factor of safety of 2.

8 QUESTION BANK ASSIGNMENT-II TWO MARKS QUESTIONS 1. Differentiate between strength design and rigidity design of shafts. 2. What are the uses of a flexible coupling? 3. What types of stresses are induced in shafts? 4. Write short note on universal coupling. 5. State the classification of shafting. 6. State the classification of rigid type coupling. 7. What is a key? State its function. 8. Differentiate between keys and splines. 9. What is the advantage of Gear coupling? 10. Why flexible coupling are preferred? 11. What are the advantages of hollow shaft over solid shaft? 12. What is torsional rigidity of a shaft? 13. What is the difference between a coupling and a clutch? 14. State the advantages of couplings. 15. What are the commonly used shaft materials? 16. What are flexible couplings and what are their applications? 17. What are the applications of cotter joint?

9 12 MARKS QUESTIONS 1. Determine the diameter of a hollow shaft, transmitting a torque of 400 N-m and subjected to a bending moment of 500 N-m. Assume the shock and fatigue factor in torsion and bending as 1.2 and 1.3 respectively. The ratio of outer to inner radii is Find the diameter, if the shaft is a solid one. Compare the weights of the hollow and solid shafts. 2. A solid circular shaft is subjected to a bending moment of 3000N-m and a torque of 10000N-m. The shaft is made of 45C 8 steel having ultimate tensile stress of 700Mpa and an ultimate shear stress of 500Mpa. Assuming a factor of safety as 6, determine the diameter of the shaft 3. Design a shaft to transmit power from an electric motor to a lathe head stock through a pulley by means of a belt drive. The pulley weighs 200W and is locked at 100 mm from the centre of the bearing. Diameter of the pulley is 200mm. Maximum power transmitted 1.5 HP.at 120 rpm. angle of lap of belt 180. Co-efficient of friction between belt and pulley 0.3. Shock factor in bending 1.5 shock factor in twisting 2.0. Allowable shear stress in the shaft 35 N/mm Determine the diameter of hallow shaft inside diameter 0.5 times the outside diameter. The permissible shear stress is limited to 200 N/mm 2. The shaft carries a 900mm diameter cast iorn pulley mounted on the shaft placed below it. The belt ends are parallel and vertical The ratio of tensions in the belt is 3. The pulley on the hallow shaft weights 800 N and overhangs the nearest bearing by 250mm. The pulley is to transmit 35 kw at 400 r.p.m. 5. A shaft is to transmit 50kW at 1200rpm. It is also subjected to a bending moment of 275N-m. Allowable shear stress is 60 N/mm 2. The shaft is not to twist more than 2 in a length of 2m. Design the shaft. Take G = 80 x 10 3 N/mm 2 6. A shaft is supported on two bearings which are 1 meter apart. The shaft carries two belt pulleys A and B at a distance of 200mm and 800mm form the left hand bearing. The diameter of both pulleys is 500mm with 180 overlap. The two belt directions are perpendicular to each other. The maximum belt tension in any belt is 2500 N. The ratio of belt tension is 2.2. The shaft is made of steel with an ultimate tensile strength of 800 N/mm 2 and tensile yield strength of 550 N/mm 2. If K b and K t are 1.5 and 1.0 respectively, design the shaft using ASME Code. 7. In an axial flow rotary compressor, the shaft is subjected to a maximum torque of 1500 N-m and a maximum bending moment of 3000 N-m. Neglecting the axial load on the compressor shat, determine the diameter of the shaft. Assume that the load is applied gradually. The shear stress in the shaft is

10 limited to 50 N\mm 2. Also design a hollow shaft for the above compressor taking inner diameter as 0.4 times the outer diameter. What is the percentage of material saving in hollow shaft? 8. Design a shaft to transmit 1.5 kw at 125 rpm, from an electric motor to a lathe headstock through a pulley using a flat belt drive. The pulley is located at 120mm form the centre of the bearing. Diameter of the pulley is 200mm. The pulley weights 225 N. angle of lap of the belt is 180 and the coefficient of friction between belt and pulley is 0.3. Shock factor in bending is 1.5 and in twisting 2. Take allowable shear stress for the shaft materials as 40N/mm Determine the diameter of hallow shaft having inside diameter 0.5 times the outside diameter. The shaft carries a 900mm diameter cast iron pulley is driven by another pulley mounted on the shaft placed blow it. The belt ends are parallel and vertical. The ratio of tensions in the belt is 3. The pulley on the hollow shaft weight 800N and overhangs the nearest bearing by 250mm. The pulley is to transmit 35 kw at 400 rpm. 10. Design a bushed-pin type flexible coupling to transmit 25 kn at 960 rpm. Use the following stress values: (a) shear stress = 50MPa (shaft and key), (b) shear stress = 30 MPa (pin) (c) crushing stress = 90 MPa (key) (d) bearing pressure = 0.45 N/mm 2 (rubber bush) 11. A marine type flange coupling the used to transmit 3.75MW at 150 rpm. The allowable shear stress in the shaft and bolts may be taken as 50Mpa. Determine the shaft diameter and the diameter of the bolts. 12. Design a knuckle joint to transmit a load of 120 KW in tension or compression. Assume the following permissible stresses are: 1) Permissible tensile stress = 85 N/mm 2. 2) Permissible shear stress = 70 N/mm 2. 3) Permissible crushing stress = 165 N/mm Design a cast iron protective flange coupling to connect two shafts in order to transmit 7.5 kw at 720 r.o.m. The following permissible stressed may be used. Permissible shear stress for bolt and key materials = 33N/mm 2, Permissible crushing stress bolt and key material = 60N/mm 2 Permissible shear stress for cast iron = 15N/mm 2.

11 14. A rigid type of coupling is used to connect two shafts transmitting 15 kw at 200rpm. The shaft keys and bolts are made of C45 steel and the coupling is cast iron. Design the coupling. 15. Design and draw a protective type of cast iron flange coupling for a steel shaft transmitting 15kW at 200 rpm and having an allowable shear stress of 40 N/mm 2. The working stress in the bolts should not exceed 30 N/mm 2. 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 maximum torque is 25% is grater than full load torque. The shear stress for cast iron is 14N/mm The flange coupling transmits 18.5 kw at 500 rpm. Find (a) Shaft diameter taking s s = 56 N/mm 2, (b) dimensions of the key, (c) Shear stress in the bolts taking bolt circle diameter = 3 x shaft diameter and (d) shear stress in the hub. 17. Design a C.I. flange coupling to transmit 80kW H.P. at 200 rpm. The following permissible stresses may be used. Allowable shear stress in the shaft is limited to 45 N/mm 2. Permissible shear stresses for key material = 45 N/mm 2. Permissible crushing stresses for bolt and key = 160 N/mm 2. Shear stress for bolt material = 30 N/mm 2. Permissible shear stress for cast iron = 8 N/mm A knuckle joint is required to withstand a tensile load 25kN. Design the joint if the permissible stress in tension = 56N/mm 2, Permissible shear stress = 40N/mm 2, Permissible crushing stress = 70 N/mm A knuckle joint is subjected to a axial load of 100kN. Determine the diameter of the knuckle pin considering the load to be uniformly distributed over the pin in the eye and uniformly varying over the portion of pin in forks. Use the following data: shear Allowable tensile and Compressive stress for pin = 600 N/mm 2.Allowable stress for pin = 300 N/mm 2.Allowable bearing pressure for pin = 200 N/mm 2. Thickness of eye = 1.5 x pin diameter. Total fork thickness = Eye thickness Draw a neat sketch of the joint.

12 20. Design a cotter joint to transmit a load of 120 kn in tension or compression. Assume the following permissible stresses. [s t ] = 85 N/mm 2, [t] = 70 N/mm 2, [s c ] = 165 N/mm Design a Knukle joint to transmit a load of 120 KN in tension or compression. Assume the following permissible stresses. Design tensile stress = 90 N/mm 2. Design Shear stress = 70 N/mm 2. Design compressive stress = 160 N/mm A knuckle joint is required to withstand a tensile load 25kN. Design the joint if the permissible stress in tension = 56N/mm 2, Permissible shear stress = 40N/mm 2, Permissible crushing stress = 70 N/mm 2