Question

92. Which is a measure to increase the rate of adhesive wear? (a) Use high-viscosity lubricants (b) Maximize real area of contact (c) Increasing yield strength of materials (d) increasing the hardness of materials

93. Lubricating oil performs 4 main function: lubricates, cushions, cleans and _____? (a) improves fuel mileage (b) heats (c) cools (d) increases driver comfort

94. What determines how much friction occur between two surfaces? (a) The amount of force pushing the objects together and how irregular the surfaces. (b) Distance the object is pulled along the surface. (c) How fast the objects are moving. (d) How hard you push or pull the objects.

95. In what way does friction help us in our everyday life? (a) standing up (b) brakes on a car (c) skiing down a slope (d) All of above 96. In the case of crankshaft bearing of a marine diesel engine, the insufficient lubrication leads to the kind of wear called scuffing. Which statement presents the incorrect explanation of this scuffing event? (a) The two surfaces have a metallic contact causing adhesion, so the wear appeared. (b) The shortage of oil between crankshaft and bearing housing cause a plastic deformation in surfaceliners (c) The two surfaces of crankshaft and the bearing housing are very close (small amount of oil), thus the asperities removed. Hence, the contact area between them increased accordingly. (d) The surface of the bearing housing is softer than the surface of the crankshaft causing the dirt in the oil film to embedded into the bearing. 97. Under the high pressure condition the fluid film is squeezed out as the interacting surfaces come closer together, friction increases along with pressure and temperature. The machine is now approaching the lubrication regime called_____________ (a) Hydrodynamic lubrication (b) Boundary lubrication (c) Mixed film lubrication (d) Elasto-hydrodynamic lubrication

Answer 1

92) answer is Maximize real area of contact

Reason: Rate of adhesive wear is directly proportional to sliding velocity. Use of high-viscosity lubricants leads to decrease in sliding velocity hence wear will decrease.

Maximizing real area of contact will leads to increase in friction and leads to increase in wear (hence correct option)

Rate of adhesive wear is independent of yield strength.

Rate of adhesive wear is indirectly proportional to hardness of material hence increase in hardness leads to decrease in wear.