STEADY STRESSES AND VARIABLE STRESSES IN MACHINE MEMBERS Introduction to the design process – factors influencing machine design – Direct, Bending and torsional stress equations – calculation of principle stresses for various load combinations, Design of curved beams – crane hook and 'C' frame – Factor of safety – theories of failure – stress concentration – Design for variable loading – Soderberg, Goodman and Gerber relations

1. STEADY STRESSES AND
VARIABLE STRESSES IN
MACHINE MEMBERS
UNIT-1

2. Design process

3. Types of design

4. Types of design

5. DESIGN PROCESS

6. DESIGN PROCESS
1.Recognition of Need

7. DESIGN PROCESS
2 . Definition of Problem

8. DESIGN PROCESS
3 . Synthesis

9. DESIGN PROCESS
4. Analysis and
optimization

10. DESIGN PROCESS
5. Evaluation

11. DESIGN PROCESS
6. Presentation

12. OPTIMUM DESIGN

13. FACTORS INFLUENCING MACHINE DESIGN
1. Strength and Stiffness
2. Surface Finish and Tolerance
3. Manufacturability
4. Ergonomics and aesthetics
5. Working atmosphere
6. Wear and Hardness Requirement
7. Cooling and Lubrication
8. Safety and Reliability
9. Noise requirement
10. Cost

14. SELECTION OF MATERIAL BASED ON MECHANICAL
PROPERTIES

15. INDIAN STANDARDS (BIS)
for Plain Carbon Steel

16. .

17. Alloys

18. PREFERRED NUMBERS

19. Arithmetic Progression

20. Geometric Progression

21. Geometric Progression

22. Meaning & Designation
R 10 Series

23. Meaning & Designation
R 20 Series

24. .

25. .

26. LIMITS , FITS AND TOLERANCE

27. Terms Used

28. Terms Used

29. Terms Used

30. Terms Used

31. Terms
Used

32. Terms
Used

33. Unilateral – Bilateral Tolerances

34. Hole Base & Shaft Base System

35. Hole Base System

36. Shaft Base System

37. FITS

38. Introduction
FITS

39. TYPES - FITS
Clearance Fit

40. Types Of Clearance Fit

41. INTERFERENCE FIT

42. TRANSITION FITS

43. Features of types of fits

44. tolerance grades Usage

45. Basic Hole and Basic Shaft
Letter H
Letter h

46. Calculation of Tolerance Grades

47. .

49. .

50. 38.73mm + (10.92861/ 1000)
= 38.73 + 0.01092861
= 38.7409 mm

51. .

54. HOLE

55. SHAFT

57. .

62. .

66. Notch Sensitivity (q)

67. Fatigue stress Concentration Factor
(Kf)

68. Relation Kt , q and Kf

69. Design for variable loading
Static Stress
Varying Stress

70. Cyclic loads produce cyclic stress which can lead to mechanical fatigue
failure:
Mechanical Fatigue = The progressive and localized structural damage
that occurs when a material is subjected to cyclic loading. The cyclic
stress is well below tensile, Su and yield, Sy , strengths!

71. Varying Stress -Types
1. Completely Reversed or Cyclic Stresses
2. Fluctuating Stresses
3. Repeated Stresses
4. Alternating Stresses

72. 1.Completely Reversed or Cyclic Stresses

73. 2. Fluctuating Stresses

74. 3. Repeated Stresses

75. 4. Alternating Stresses

77. FATIGUE CRACK

78. • Fatigue limit, endurance limit, and fatigue
strength are all expressions used to describe a
property of materials.

80. Endurance
• Endurance strength is the stress level that a
material can survive for a given number of load
cycles.
• Endurance limit is the stress level that a
material can survive for an infinite number of
load cycles.
• Estimate for Wrought Steel:
Endurance Strength = 0.50(Su)
• Most nonferrous metals (aluminum) do not
have an endurance limit.

82. Factors affecting endurance limit
1. Load Factor (KL)
2. Surface Finish Factor (KSF)
3. Size Factor (KSZ)
4. Reliability Factor (KR)
5. Miscellaneous Factors (K)

89. S-N Curve
• S of S-N curve stands for "Stress". That means repeatitive load.
• N stands for "Number of cycles to failure".
S describes a vertical axis and N describes a cross axis. Those make a
graph below.