Mechanical Sciences Lubrication Principles

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Author:
ereim
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29058
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Mechanical Sciences Lubrication Principles
Updated:
2010-08-06 11:36:01
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Lubrication
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Chap 09
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  1. The molecular attraction between particles that tends to cause unlike surfaces to stick together
    Adhesion
  2. The molecular attraction between particles that tends to hold a substance or a body together.
    Cohesion
  3. A layer of lubricant.
    Film
  4. Accelerated surface damage occurring at the interface of contacting materials subjected to small oscillating displacement.
    Fretting
  5. The friction that exists between moving bodies (or between one moving body and a stationary surface). The opposite of static.
    Kinetic friction
  6. Erosion of components caused by impingement of solid particles or water droplets that reduces the life of machinery.
    Particle or droplet erosion
  7. The friction that exists between a body at rest and the surface upon which it rests.
    Static friction
  8. A plastic flow phenomenon that typically occurs in rolling element bearings.
    Thermal softening
  9. The study that deals with the design, friction, wear, and lubrication of interacting surfaces in relative motion.
    Tribology
  10. The removal of material from one or more solid surfaces that are in contact.
    Wear
  11. DESCRIBE the environmental hazards associated with lubricants.
    Many lubricants are hazardous to the environment and are carcinogenic (can cause cancer).
  12. Define tribology.
    Tribology is defined as the study that deals with the design, friction, wear, and lubrication of interacting surfaces in relative motion.
  13. Describe sliding, rolling, and fluid friction.
    The friction that exists between moving bodies (or between one moving body and a stationary surface) is called kinetic friction

    Sliding friction exists when the surface of one solid body is moved across the surface of another solid body.

    Rolling friction exists when a curved body (i.e.,cylinder or sphere) rolls upon a flat or curved surface.

    Fluid friction is the resistance to motion exhibited by a fluid.
  14. Describe the desirable properties of lubrication.
    Cohesion is the property that holds the lubricant together and enables it to resist breakdown under pressure

    Adhesion is the property of a lubricant that causes it to stick to the parts being lubricated.
  15. Two modes in which friction and wear are affected by properties of the surfaces in contact as well as the lubrication.
    Boundary lubrication and thin-film lubrication
  16. Occurs in a system due to the shape and relative motion of the surfaces in contact.
    Hydrodynamic lubrication
  17. The result of a lubricant being supplied at a pressure that is high enough to separate the surfaces.
    Hydrostatic
  18. The lubricant is not bonded to the surface; therefore, the lubricant will not separate the surfaces.
    Thin-film lubrication
  19. A chemically bonded lubricant, which may or may not separate the surfaces, covers each surface and viscosity of the lubricant is not a factor for determining wear
    boundary lubrication
  20. When one tooth of a spur gear meshes with the tooth of a mating gear, the initial contact is sliding contact and results in the wear and tear of
    Tips and Roots of the teeth
  21. Lubricants may be broadly classified as
    liquid, semi-solid, or solid.
  22. Two common solid lubricants are
    graphite and molybdenum disulfide
  23. Recommended for gear drives when a higher load capacity lubricant is required.
    Extreme pressure (EP) additives
  24. Compounded oils are available with many different additives. The most commonly available is a molybdenum disulfide compound that has been successfully used in
    gear applications
  25. Used when a component cannot be lubricated on a timely basis or the system or
    component cannot be accessed during operation
    Greases
  26. Greases can have four parts
    fluid base, thickener, additives, and fillers
  27. Combine the properties of two or more specialized greases to function over a broader range of conditions and applications.
    Multipurpose greases
  28. Four classes of fluids generally used in hydraulic systems that operate in such an
    environment are:
      • phosphate esters,
      • water-glycol fluids,
      • invert emulsions, and
      • conventional emulsions.
  29. The major cause of lubrication-related failures is the
    incorrect amount of lubrication being applied to components.
  30. When too little lubricant is added, surface damage will result. The damage will rapidly cause failures that
    can be difficult to distinguish from primary fatigue failures and results in small flakes
    Spalling
  31. Occurs when two materials contact each other and the surface of one material is harder
    than the surface of the other materials.
    Abrasive wear
  32. Burrs at the sliding interface between two mating parts melts and welds the surfaces
    together
    Adhesive wear
  33. Defined as accelerated surface damage occurring at the interface of contacting materials subjected to small oscillatory displacement.
    Fretting wear
  34. Erosion of components caused by impingement of solid particles or water droplets can
    cause reduced life of machinery.
    Particle & Droplet Erosion
  35. Current that seeks ground through the bearing can be generated from stray magnetic fields in the machinery or can be caused by welding on some part of the machine with the ground attached so that the circuit is required to pass through the bearing.
    Spark Erosion
  36. Lubricants in gear units have two functions
    separate the tooth and bearing surfaces, and cool the surfaces
  37. The most common and foolproof method of gear lubrication.
    Splash lubrication
  38. Pressurized lubrication and is used on almost all high-speed gear drives, on spiral bevel drives, and on low-speed drives when splash lubrication cannot be used due to gear arrangement.
    Force-fed lubrication
  39. Grease has several advantages as compared to oil:



    • Easy to add additional grease



    • Offers better adhesion capabilities



    • Provides protection against moisture and contaminants



    • Easily retained in the bearing housing



  40. The single most important property of a lubricant and may be influenced by temperature, pressure, and fluid motion (shear).
    Viscosity
  41. That temperature at which oil will just flow under prescribed conditions.
    Pour point
  42. The temperature at which the oil produces sufficient flammable vapor to ignite when
    the vapor is brought into momentary contact with a flame.
    Flash Point
  43. The higher temperature at which the oil vapors will continue to burn when ignited
    Fire Point

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