Question 47

The Correct Answer is B **Explanation for Option B (Correct Answer):** The proper location for journal bearing oil grooves is **as a side relief where the two shells meet (Option B)**. This location is chosen for optimal lubrication distribution without disrupting the formation of the crucial hydrodynamic oil wedge. 1. **Side Relief/Split Line:** The point where the two bearing shells (halves) meet (the split line or side) is typically an area of low pressure and is not part of the primary load-bearing surface. 2. **Distribution:** Placing the groove here allows pressurized oil to enter the bearing and be distributed axially and circumferentially to the non-load-bearing areas. As the journal rotates, this oil is then dragged into the converging wedge area (where the pressure is built up) to form the hydrodynamic film. 3. **Preventing Film Failure:** Grooves placed at the split line act as feed channels but do not interfere with the high-pressure zone, ensuring that the necessary hydrodynamic oil film pressure is maintained. **Explanation of Incorrect Options:** * **A) in the region of the load bearing surface:** This is incorrect. The load-bearing surface is where the hydrodynamic pressure is highest. Placing a groove here would vent the high pressure, cause the oil film to rupture, and lead to metal-to-metal contact, resulting in failure (scoring or wiping). * **C) halfway between bottom and where shells meet:** While this area is outside the absolute maximum pressure zone (which is typically slightly offset from the bottom center), it still falls within the main pressure-generating region. Placing a continuous groove here would significantly disrupt the pressure buildup needed for proper hydrodynamic lubrication. * **D) at the bottom of the bearing:** This is the primary region of the maximum steady load (especially in horizontal shafts). Placing a groove directly at the bottom center would entirely interrupt the hydrodynamic wedge, immediately dropping the pressure to zero and causing catastrophic failure of the bearing film.