CHAPTER 6: MECHANICAL PROPERTIES

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7.20 DESIGN/SAFETY FACTORS• Design uncertainties mean we do not push the limit.• Factor of safety, Nσ working= σ yNOften N isbetween1.2 and 4• Ex: Calculate a diameter, d, to ensure that yield doesnot occur in the 1045 carbon steel rod below. Use afactor of safety of 5.σ working220,000N⎛π d 2 ⎞ 5⎜ / 4⎟⎝ ⎠= σ yNd = 47.5 mm29
SUMMARY• Stress and strain: These are size-independentmeasures of load and displacement, respectively.• Elastic behavior: This reversible behavior oftenshows a linear relation between stress and strain.To minimize deformation, select a material with alarge elastic modulus (E or G).• Plastic behavior: This permanent deformationbehavior occurs when the tensile (or compressive)uniaxial stress reaches σy.• Toughness: The energy needed to break a unitvolume of material.• Ductility: The plastic strain at failure.30
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CHAPTER 7:MECHANICAL PROPERTIESISSU
Page 5 and 6:
7.2 COMMON STATES OF STRESS• Simp
Page 7 and 8: OTHER COMMON STRESS STATES• Bi-ax
Page 9 and 10: 7.2 STRESS-STRAIN TESTING• Typica
Page 11: ELASTIC DEFORMATIONS7.3 Stress-stra
Page 14 and 15: c07f08
Page 16 and 17: 7.4 ANESLATICITYAssumed:Time-indepe
Page 18 and 19: E(GPa)10 9 Pa1200100080060040020010
Page 20 and 21: II. MECHANICAL BEHAVIOR—METALS
Page 22 and 23: II. PLASTIC (PERMANENT) DEFORMATION
Page 24 and 25: • YIELD STRENGTH, σ yStress at w
Page 26 and 27: 7.6 TENSILE STRENGTH, TSMaximum pos
Page 28 and 29: 7.6 DUCTILITY, %ELDegree of plastic
Page 30 and 31: Stress-strain of iron at several te
Page 32 and 33: 7.6 TOUGHNESS• Ability to absorb
Page 34 and 35: 7.7 True stress & strainHARDENING:
Page 36 and 37: 7.8 Elastic Recovery After Plastic
Page 38 and 39: III. MECHANICAL BEHAVIOR—CERAMICS
Page 40 and 41: 7.11 Elastic Behavior (forceramics)
Page 42 and 43: IV MECHANICAL BEHAVIOR—POLYMERS7.
Page 44 and 45: 7.14 Macroscopic DeformationSemicry
Page 46 and 47: 7.15 Viscoelasticity DeformationLoa
Page 48 and 49: Polystyrene configurationsAlmost to
Page 50 and 51: c07tf05
Page 52 and 53: c07tf06b
Page 54 and 55: Correlation between Hardness and Te
Page 56 and 57: 7.18 Tear Strength & Hardness of Po
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CHAPTER 6: MECHANICAL PROPERTIES

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