MET 34800 – Engineering Materials Chapter 5

MET 34800 – Engineering Materials Chapter 5...

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MET 34800 – ENGINEERING MATERIALS IUPUI ENGINEERING TECHNOLOGY ENT Department
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CHAPTER 5 TRIBOLOGY AND ENGINEERING MATERIALS Engineering Materials: properties and selection, 9th ed. Kenneth G. Budinski, Michael K. Budinski
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Upon completion of this chapter, the student should: have an understanding of tribology and its importance have a knowledge of the fundamentals of friction have a knowledge of the type of wear that can occur have a review of the fundamentals of bearings and lubricants CHAPTER GOALS 3
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Origin of the word “tribology” Friction costs (10% of GDP) Wear cost (5% of GDP) Scope of tribology INTRODUCTION 4
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Lubrication in building pyramids da Vinci’s friction experiments Amonton’s friction laws Identification of static and kinetic coefficient of friction 5.1 HISTORICAL STUDIES OF FRICTION AND WEAR 5
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Real area of contact Hertz stress equations Stress in real contacts are different from the apparent stress 5.2 CONTACT MECHANICS 6
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Figure 5–1 Concept of real and apparent area of contact 5.2 CONTACT MECHANICS 7
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Figure 5–2 When real surfaces contact, the raised features of the surfaces carry the load 5.2 CONTACT MECHANICS 8
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Figure 5–3 Hertz equation for the contact of a sphere on a flat surface under elastic conditions 5.2 CONTACT MECHANICS 9
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Role of surface roughness Components of friction: F=F a +F p +F s +F n Area independence µ = S/P Different types of friction Rolling friction Measurement Lubricated friction Significance Use of published friction data in design 5.3 FRICTION 10
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Figure 5–4 The force required to move surface A up the rugosities on surface B 5.3 FRICTION 11
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Figure 5–5 Types of friction 5.3 FRICTION 12
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Figure 5–6 The difference between the coefficient of frication and the traction coefficient; they are mathematically similar, but differ in point of force application. 5.3 FRICTION 13
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Figure 5–7 Pure “rolling” only occurs in areas a and b 5.3 FRICTION 14
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Figure 5–8 Equations for friction force 5.3 FRICTION 15
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Figure 5–9 Rolling friction test. Rolling resistance number is the height of the hill divided by the distance travelled on rolling from the top (car in neutral with engine running). 5.3 FRICTION 16
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Figure 5–10 Types of friction force recordings that can be encountered 5.3 FRICTION 17
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Figure 5–11 Average friction coefficients for various materials in reciprocating motion of an annular ring rider (0.1 on a type 316 stainless steel counterface at 50% relative humidity (RH) at various normal forces. The stroke was 50 mm and the frequency was 0.5 Hertz. The friction force was averaged for eight cycles in each test.
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