BEARINGS

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• Q1: Define Bearings.
  Ans: Bearings are machine elements that support rotating or moving shafts and reduce friction between moving parts.
• Q2: State any four functions of Bearings.
  Ans: The functions of bearings are as follows:

  • ➔ Support rotating shafts or axles
  • ➔ Reduce friction between moving parts
  • ➔ Maintain shaft alignment
  • ➔ Transmit loads safely
• Q3: State the classifications of Bearings.
  Ans: The classifications of bearings are as follows:

  • ➔ Radial Bearings
  • ➔ Thrust Bearings
  • ➔ Sliding Contact Bearings
  • ➔ Rolling Contact Bearings
• Q4: Define Radial Bearings.
  Ans: Radial bearings are bearings that support loads acting perpendicular to the shaft axis.
• Q5: Define Thrust Bearings.
  Ans: Thrust bearings are bearings designed to support loads acting parallel to the shaft axis.
• Q6: Define Sliding Contact Bearings.
  Ans: Sliding contact bearings are bearings in which the shaft slides over a lubricated surface, creating relative motion with minimal friction.
• Q7: Define Rolling Contact Bearings.
  Ans: Rolling contact bearings use rolling elements like balls or rollers between the shaft and bearing to reduce friction.
• Q8: Define Sleeve or Journal Bearings.
  Ans: Sleeve or journal bearings are cylindrical bearings in which the shaft rotates inside a hollow sleeve, usually with a lubricant layer.
• Q9: Define Full Journal Bearings.
  Ans: Full journal bearings completely surround the shaft, providing maximum support and load-carrying capacity.
• Q10: Define Partial Journal Bearings.
  Ans: Partial journal bearings support only a part of the shaft circumference, reducing friction but carrying less load.
• Q11: Define Fitted Bearings.
  Ans: Fitted bearings are bearings designed with a very small clearance to tightly fit the shaft for precise alignment and minimal vibration.
• Q12: Define Slipper Bearings.
  Ans: Slipper bearings are bearings with a curved or flat surface that supports the shaft at a sliding contact, often used in low-speed applications.
• Q13: Define Clearance Bearings.
  Ans: Clearance bearings are bearings designed with a small gap between the shaft and bearing to allow lubrication and thermal expansion.
• Q14: State four uses of Bearings.
  Ans: The uses of bearings are as follows:

  • ➔ Support rotating shafts in machines
  • ➔ Reduce friction and wear
  • ➔ Absorb radial and thrust loads
  • ➔ Improve machine efficiency and lifetime
• Q15: What is Diameter Clearance?
  Ans: Diameter clearance is the difference between the bearing internal diameter and the shaft diameter.
• Q16: What is Radial Clearance?
  Ans: Radial clearance is the total space between the shaft and bearing along the radius, allowing for lubrication and movement.
• Q17: What is Diametral Clearance Ratio?
  Ans: Diametral clearance ratio is the ratio of radial clearance to the shaft diameter.
  e = Radial clearance / Shaft diameter
• Q18: What is Eccentricity?
  Ans: Eccentricity is the distance between the center of the shaft and the center of the bearing.
  It occurs due to load or misalignment.
• Q19: What is the Eccentricity Ratio?
  Ans: Eccentricity ratio is the ratio of eccentricity to radial clearance.
  ε = E / C
  Where E = Eccentricity, C = Radial clearance
• Q20: What is Minimum Oil Thickness?
  Ans: Minimum oil thickness is the thinnest layer of lubricant between the bearing and shaft required to prevent metal-to-metal contact.
• Q21: What is Short Bearing?
  Ans: Short bearing is a bearing whose length is less than the shaft diameter (L < D).
  It has lower load capacity.
• Q22: What is Long Bearing?
  Ans: Long bearing is a bearing whose length is greater than the shaft diameter (L > D).
  It can carry higher loads and reduce pressure on the lubricant.
• Q23: What is Lubrication of Bearings?
  Ans: Lubrication of bearings is the process of applying a lubricant (oil, grease, or solid) to reduce friction and wear between the bearing and shaft.
• Q24: State Liquid lubricants for Bearing?
  Ans: Liquid lubricants include:

  • ➔ Mineral oils
  • ➔ Synthetic oils
  • ➔ Animal or vegetable oils
• Q25: State Solid lubricants for Bearing?
  Ans: Solid lubricants include:

  • ➔ Graphite
  • ➔ Molybdenum disulfide
  • ➔ PTFE (Teflon)
• Q26: State Semi-Liquid lubricants for Bearing?
  Ans: Semi-liquid lubricants include:

  • ➔ Grease
  • ➔ Oil-soap mixtures
  • ➔ Molten metals in special bearings
• Q27: State the Critical Pressure of Journal Bearing.
  Ans: Critical pressure is the maximum pressure that can be applied on a journal bearing without causing metal-to-metal contact or failure of the lubricant film.
• Q28: What is a Sommerfeld Number?
  Ans: Sommerfeld Number is a dimensionless number used to describe the performance of a journal bearing.
  S = (μ × N × P) / (p × (D/L)²)
  Where μ = Viscosity, N = Rotational speed, P = Load, D = Diameter, L = Bearing length