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PES University Departtment of Mechanical Engineering

Unit-1 Assessment Question Bank

Course: Design of Machine Elements Semester: Fifth Semester

PES University Departmen nt of Mechanical Engineering

04_02 Assessment: Question Baank Unit-1 Theory Questions Introduction to Design for Stattic Strength 1. 2. 3.

4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16.

Define Machine Desig gn and high light the important features of machine design With the help of a flow w chart explain briefly the basic procedure of machine design List the product speciffications of the following: a. Lathe b. Drilling machine c. Milling machine d. Scooter e. Car f. Water Turbine g. Oil Pump Design of individual components/elements is an important step in a design process. Justify this statement with w your own words What are the important components to be mentioned in a machine drawing? Distinguish between mechanism m and machine Distinguish between machine m and machine element Name the two classifie ed groups of machine elements, with examples State the main objectiv ve of designing a machine element List and explain the ba asic requirements of machine elements With the help of a flow w chart explain briefly the basic procedure of design of machine elements List the important information that can be obtained from a tension testt Name the standard to specify the shape and dimensions a specimen used for tension test o specimen used for tension test with relevaant notations and Write a neat sketch of relations Write the neat sketch of a stress-strain diagram of ductile material and mark the vital points Define the following mechanical m properties i. Strength ii. Elasticity iii. Plasticity iv. Stiffness v. Resilience vi. Toughness vii. Malleability viii. ductility 1

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17. 18. 19. 20. 21. 22. 23.

ix. Brittleness x. Hardness Define static load How do you define thee failure of machine components? Write the three modes of failure and explain briefly State the definition of factor of safety and write its mathematical expre essions What are the factors ag gainst which the factor of safety takes care? What are the factors on n which the magnitude of factor of safety depends? Under what conditionss higher factor of safety is chosen?

Theories of Failures 24. 25. 26. 27.

28.

Quote examples of ma achine components, which are subjected to several types of loads simultaneously. What is the design app proach to design a component subjected to severral types of loads simultaneously? Name the Principal the eories of elastic failures Write the statement of the following theories of elastic failures i. Maximum princip pal stress theory (Rankine’s theory) ii. Maximum shear stress s theory (Guest’s or Tresca’s or Coulomb’s theory) iii. Maximum distortiion energy theory (Hencky’s and Huber Von Mises theory) iv. Max imum princip pal strain theory (Saint Venant theory) v. Maximum total sttrain energy theory (Haigh’s theory) High light on the Selec ction and use of Failure Theories

Design for Fatigue Strength 29. 30. 31. 32. 33. 34. 35. 36. 37. 38.

Define stress concentration Write mathematical ex xpression for theoretical stress concentration factor Write and explain briefly the causes for stress concentration in machin ne elements Name the two methodss used to determine the stress concentration factors What are the guidelines to be considered by the designer while considering the theoretical stress conceentration factor? Who developed the strress concentration factors chart? Name and explain briefly the various methods used in practice to reduce the stress concentration in a mac chine component/element Why study of des ign oof machine element under fluctuating stress is so o important? What are the three typ pes of mathematical models used for expressin g cyclic stresses, explain briefly with a neat sketch? Define fatigue failure and name few machine components in whicch fatigue failure occurs

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39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52.

In brief explain the ba asic difference between failure due to static loa ad and the due to fatigue. Define fatigue or endurance limit Define fatigue life Who developed the lab boratory setup to estimate the endurance limit? What is S-N curve? W Why it is also called as Wöhler diagram Write and explain a S-N curve used for ferrous metals Define low-cycle and hhigh-cycle fatigue and explain briefly with a neat sketch What is difference between the notations Kt and Kf used in design of machine elements? Write the mathematica al expression for fatigue stress concentration factor Define notch sensitivitty What is derating factorrs? and name any four derating factors Explain briefly the any y two derating factors? With a neat sketch exp plain Soderberg and Goodman Lines What are the three reasons the Goodman line is widely used as the crriterion of fatigue failure?

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Numerical Questions Introduction to Design for Stattic Strength 1. Find the diameter of a rod made m of C14 material subjected to an axial load (direct load) as shown in Figure 1. Assume tthe factor safety as 3. 2. Find the diameter of a rod made m of 15C8 material subjected to an axial load (direct load) as shown in Figure 2. Assume tthe factor safety as 2.

Fig. 2 Fig. 1 3. Find the diameter of a rod made of C14 material subjected to a shear load ass shown in Figure 3. Assume the factor safety as 3.

Fig. 3 4. Find the diameter of a rod made of 35C8 material subjected to the load as shown in Figure 4. Assume the factor safety as 22.

Fig. 4 4

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5. Find the diameter of a rod made m of C14 material subjected to transverse load as shown in Figure 5. Assume the factor safety as 3. 6. Find the diameter of a rod made of 20C8 material subjected to the load as shown in Figure 6. Assume the factor safety as 22. F = 2 kN

Fig. 5

Fig. 6

7. Two round rods are joined by means of a knuckle joint as shown in Figure 7. Determine the diameter of rod (d) and the diameter d of knuckle pin (d 1), if the rod is underr a tensile load of 48 kN. Both rod and knucklee pin are made of Carbon steel (Cast steel, medium). Assume the factor of safety for rod as 3 and pin as 2. 8. Determine the required thickness of the steel bracket at section A-A when loaded as shown in Figure 8. The material of thee element is C35. Assume the factor of safety as 3.

Fig. 7

Fig. 8

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9. A grey cast iron FG 200 brracket shown in Figure 9 is subjected to a pu ull of 5 kN. The bracket has a rectangular cro oss-section whose depth is twice the width. Determine c/s of the bracket, assuming the factor of safety as 3.5.

Fig. 9

10. A load of F = 18 kN is acting g on a C-clamp at an eccentric of e = 220 mm as shown in Figure 10. The clamp fram me is made of Carbon steel C25. The crosss-section of the frame is rectangular with width three times the thickness. Determine the e dimensions b and t.

Fig. 10

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Theories of Failures 11. The stresses on two mutually y perpendicular planes through a point in a body y are 30 MPa and 15 MPa, both tensile along with w a shear stress of 25 MPa. Find the Principal Stresses. 12. The stresses on two mutually perpendicular planes through a point in a bo ody are 120 MPa and 30 MPa both tensile along with a shear stress of 60 MPa. Determiine the Principal Stresses. 13. The stresses on two mutually y perpendicular planes through a point in a body y are 80 MPa and 50 MPa both tensile. Determ mine the maximum value of the shear stress whic ch can be applied so that the maximum value of the permissible Principal Stress is limited to 120 MPa. 14. A plate of C45 steel is subjec cted to the following stresses:         Find the factor of safety using, u a. Maximum Princip pal Stress Theory b. Maximum Shear Stress S Theory and c. Maximum Distorttion Energy Theory (Hencky - Mises Theory) 15. A carbon steel C15 shaft of 60 6 mm diameter is subjected to a bending momeent of 25 x 105 Nmm and Torque T. Find the maximum value of Torque that can be transmitted without causing yield of the shaft acccording to: (Assume the FOS = 1.5) a. Maximum Princip pal Stress Theory b. Maximum Shear Stress S Theory and c. Maximum Distorttion Energy Theory 16. A material has maximum yield strength in tension and compression as 100 0 MPa. Compute factor of safety for the follow wing theories of failure d. Maximum Normaal Stress Theory e. Maximum Shear Stress S Theory and f. Maximum Distorttion Energy Theory Considering the following g stresses: i.          ii.          iii.          7

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17. A round rod of diameter 50 0 mm is to sustain an axial compression load of 20 kN and a twisting moment of 1.5 kNm m. The rod is made of carbon steel C40. Determ mine the factor of safety as per the following theories of failure: a. Maximum Principal Strain Theory b. Distortion Ene ergy Theory and c. Maximum Ela astic Strain Energy Theory 18. A rod of circular cross secttion is to sustain a torsional moment of 300 kNm and bending moment 200 kNm. Selectinng C45 steel and assuming factor of safety 66, determine the diameter of the rod as per the e following theories of failure: [Assume µ = 0.3]] a. b. c. d.

Maximum Princip pal Stress Theory Maximum Shear Stress S Theory Maximum Distorttion Energy Theory and Total Energy Theory

19. A circular rod of diameter 50 0 mm is subjected to loads as shown in Figure 111. Determine the nature and magnitude of stresses at the critical points. 20. A 50 mm diameter steel rod supports a 9 kN load and in addition is subjected to a torsional moment of 100 N-m as shown in Figure 12. Determine the maximum m tensile and the maximum shear stress.

Fig. 11

Fig. 12

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21. A bar of 50 mm diameter fixed f at one end is subjected to a torsional load of 1 kN-m in addition to an axial pull of 15 kN as shown in Figure 13. Determine the principal stresses if the length of the shaft is 250 mm.

Fig. 13 22. Determine the maximum no ormal stress and maximum shear stress at secction A-A for the crank shown in Figure 14, when w a load of 10 kN is assumed to be concentra ated , is applied at the centre of crank pin. Neglect the effect of transverse shear. ormal stress and maximum shear stress at secction A-A for the 23. Determine the maximum no crank shown in Figure 15, when w a load of 10 kN is assumed to be concentrated at the centre of crank pin.

Fig. 14

Fig. 15

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Design for Fatigue Strength 24. Determine the maximum strress induced in a plate of breadth 60 mm, length 80 mm and thickness 10 mm, with a holle of 12 mm diameter at the centre of the plate is subjected to a tensile load of 12 kN as show wn in Figure 16. Consider the stress concentration fa ctor (SCF) into account.

Fig. 16 25. Determine the maximum stress induced in a plate of breadth 100 mm, length 180 mm and thickness 15 mm, with a holle of 20 mm diameter at the centre of the plate is subjected to a tensile load of 15 kN as show wn in Figure 17. Consider the stress concentration factor (SCF) into account.

Fig. 17 26. Determine the maximum strress induced in a plate of breadth 60 mm, length 80 mm and thickness 10 mm, with a holle of 10 mm diameter at the centre of the plate is subjected to a transverse bending moment of 25 Nm as shown in Figure 18 . Con nsider the stress concentration factor (SCF) in nto account.

Fig. 18 10

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27. Determine the maximum stress induced in a plate of breadth 100 mm, length 180 mm and thickness 10 mm, with a holle of 10 mm diameter at the centre of the plate is subjected to a transverse bending moment of 40 Nm as shown in Figure 19. Con nsider the stress concentration factor (SCF) in nto account

Fig. 19 28. Determine the maximum strress induced in a plate of breadth 60 mm, length 80 mm and thickness 10 mm, with a nottch of radius 10 mm is subjected to a tensile lo oad of 12 kN as shown in Figure 20. Consideer the stress concentration factor (SCF ) into acco ount.

Fig. 20 29. Determine the maximum stress induced in a plate of breadth 120 mm, length 180 mm and thickness 12 mm, with a nottch of radius 15 mm is subjected to a tensile lo oad of 16 kN as shown in Figure 21. Consideer the stress concentration factor (SCF) into acco ount

Fig. 21 11

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30. Determine the maximum strress induced in a plate of breadth 60 mm, length 80 mm and thickness 10 mm, with a notcch of radius 10 mm is subjected to a transverse bending moment of 25 Nm as shown in Figgure 22. Consider the stress concentration fa actor (SCF) into account.

Fig. 22 31. Determine the maximum strress induced in a plate of breadth 80 mm, length 160 mm and thickness 12 mm, with a notcch of radius 12 mm is subjected to a transverse bending moment of 35 Nm as shown in Figuree 23. Consider the stress concentration factor (SCF) into account

Fig. 23 e 24, if the stress 32. Find the value of maximum stress induced in the fillet as shown in Figure concentration factor for the filleted f flat bar is considered and having a B/b ratio r of 1.2. Also determine the factor of safety if the flat bar is made of steel having a yield stress of 640 N/mm 2. The thickness of the bar is 25 mm.

Fig. 24 12

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e 25, if the stress 33. Find the value of maximum stress induced in the fillet as shown in Figure concentration factor for the filleted f flat bar is considered and having a B/b ratio r of 1.4. Also determine the factor of safety if the flat bar is made of steel having a yield stress of 540 N/mm 2. The thickness of the bar is 20 mm

Fig. 25 34. Determine the maximum stre ess induced in a plate of breadth 100 mm and thickness 12 mm, with a fillet radius 12 mm is subjected to a transverse bending moment of 20 Nm as shown in Figure 2.17 (DDHB). Connsider the stress concentration factor (SCF) into account 35. Determine the maximum stre ess induced in a grooved shaft of diameter 80 m mm and radius of groove 10 mm is subjected to an axial load of 10 kN as shown in Figurre 2.18 (DDHB). Consider the stress concentra ation factor (SCF) into account 36. Determine the maximum stre ess induced in a grooved shaft of diameter 100 mm m and radius of groove 12 mm is subjected to an axial load of 12 kN as shown in Figurre 2.18 (DDHB). Consider the stress concentra ation factor (SCF) into account 37. Determine the maximum stre ess induced in a grooved shaft of diameter 80 m mm and radius of groove 10 mm is subjectedd to a bending moment of 12 Nm as shown in Figure 2.20 (DDHB). Consider the stress concentration factor (SCF) into account 38. Determine the maximum stre ess induced in a grooved shaft of diameter 120 mm m and radius of groove 15 mm is subjectedd to a twisting moment of 15 Nm as shown in Figure 2.22 (DDHB). Consider the stress concentration factor (SCF) into account 39. Determine the maximum stre ess induced in a stepped shaft of diameter 150 mm m and radius of DDHB). Consider fillet 15 mm is subjected to aan axial load of 8 kN as shown in Figure 2.23 (D the stress concentration factor (SCF) into account

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40. Determine the maximum stre ess induced in a stepped shaft of diameter 150 mm m and radius of re 2.25 (DDHB). fillet 15 mm is subjected to a bending moment 12 Nm as shown in Figur Consider the stress concentra ation factor (SCF) into account

ess induced in a stepped shaft of diameter 150 mm m and radius of 41. Determine the maximum stre re 2.27 (DDHB). fillet 15 mm is subjected to a twisting moment 10 Nm as shown in Figur Consider the stress concentra ation factor (SCF) into account

s section is subjected to an axial pull of 100 kN, as shown in 42. A plate of rectangular cross Figure 26. Assuming the streess in the plate is limited to 200 MPa, determine the thickness of the plate.

Fig. 26 s section is subjected to an axial pull of 120 kN, as shown in 43. A plate of rectangular cross Figure 27. Assuming the streess in the plate is limited to 160 MPa, determine the thickness of the plate

Fig. 27

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44. A grooved shaft shown in Fiigure 28 is to transmit 5 kW at 120 rpm. Determ mine the diameter of the shaft at the groove if itt is made of C15 steel and take FOS 2.

Fig. 28 45. A stepped shaft shown in Fiigure 29 is subjected to a transverse load. The shaft is made of FeE 400 steel. Determine the e diameter d of the shaft based on the factor of safety 2. Consider the stress concentration into aaccount.

Fig. 29

46. A stepped shaft shown in Fiigure 30 is subjected to a transverse load. The shaft is made of FeE 370 steel. Determine the diameter d of the shaft based on the factor of safety 2.2. Consider the stress concentra ation into account

Fig. 30

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47. A flat plate subjected to a tensile force of 5 kN is shown in Figure 31. Thee plate material is grey cast iron FG 200 and thee factor of safety is 2.5. Determine the thickness s of the plate.

Fig. 31 48. Determine the maximum stress induced in the semi-circular grooved shaft shown in Figure 32, if it is subjected to: (Take e the stress concentration into account) a. An axial load of 40 4 kN b. A bending momennt of 400Nm and c. A twisting momennt of 500 Nm

Fig. 32

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Problems on stresses due to Fluuctuating Load: 49. A steel rod of material SAE92260 oil quenched is subjected to a tensile load which w varies from 120 kN to 40 kN. Design the ‘safe diameter’ of the rod using ‘Soderberg Diagram’. Adopt factor of safety as 2, stress cooncentration factor as unity and notch sensitivity factor as 0.8. It is given correction factor for load, size and surface as 0.75, 0.85 and 0.91 respectively. 50. A steel rod of material SAE92260 oil quenched is subjected to a tensile load which w varies from 150 kN to 50 kN. Design the ‘safe diameter’ of the rod using ‘Soderberg Diagram’. Adopt factor of safety as 1.5, stress concentration factor as unity and notch sensitiv vity factor as 0.8. It is given correction factor foor load, size and surface as 0.75, 0.85 and 0.91 respectively. 51. A piston rod is subjected to a maximum reversed axial load of 110 kN. It is made of steel having an ultimate stress of 900 9 N/mm 2 and the surface is machined. The average endurance limit is 50% of the ultimate strength. Take the size correction factor as 0.85 and factor of safety as 1.75. Determine thee diameter of rod.

52. A piston rod is subjected to a maximum reversed axial load of 120 kN. It is made of steel having an ultimate stress of 850 8 N/mm 2 and the surface is machined. The average endurance limit is half of the ultimate strength. Take the size correction factor as 0.....