Narrow zone of wear in the crown of the bearing shell
DESCRIPTION OF THE DAMAGE
- Narrow wear marks in the shell crown
- More pronounced in the shell that receives most stress
- In severe cases: signs of material fatigue and initial rubbingmarks visible
Wear marks in the area of the crown in the form of adaptive run-in wear can be recognised. No other operating marks are visible in other parts of the bearing sliding surfaces.
DAMAGE ASSESSMENT
This appearance is caused by a horizontal oval bore. This reduces the bearing clearance in the crown meaning that the lubricating film is not fully stable and mixed friction occurs in places. If the shortage of lubrication continues, the temperature increases due to the frictional heat that results. The shortage of lubrication continues to intensify due to the increasing temperature level and the process reinforces itself until the first initial rubbing marks occur and fatigue damage occurs in this area due to increased surface pressure.
POSSIBLE CAUSES FOR THE DAMAGE
- Placement of the connecting rod or the housing striking faces
- Wrong bolt tightening when boring the bore
- Extreme connecting rod pressure load
Remedy
- Check the bearing line bore is correct: dimensions, roundness, cylindricity, surface
- Tighten bolts in accordance with the manufacturer‘s specifications with regard to tightening torques and the tightening sequence
- Check stress on the connecting rod