Exam Question

(a) The connecting rod ovality of the bottom end bearing is caused by cyclic loading and the angular motion of the connecting rod. Importance of connecting rod ovality:
Ovality can disrupt the uniform oil film that facilitates hydrodynamic lubrication. A failure in this lubrication can result in direct metal-to-metal contact, overheating, and bearing failure.
Ovality causes an uneven distribution of forces on the bearing, crankpin, and gudgeon pin, leading to localized wear, pitting, and damage.
If the connecting rod’s deformation affects the piston’s motion, it may cause poor sealing of the piston rings, leading to blow-by gases, power loss, and increased emissions.