hi, do you know the difference between bad bonding and fatigue failure? when mostly these bearing failure due to bad bonding or fatigue will happen? Thanks

bad bonding - manufacuring defect?
fatigue failure - prematrue fatigue - exposed to excessive load from abnormaly high vibration.

As Valve stated, there are a number of causes of bad bonding - but the root cause is in poor manufacturing, poor choice of materials, etc. from the bearing supplier.
Fatigue failure is caused primarily by system process (i.e. excessive loading such as unbalance)which is something you have more control over (not accounting for poor QC inspection of bearings).

To further complicate post-mortems, it is not always clear at first glance what the obvious root cause is since a poor design (e.g. babbit too thick but bond OK) PLUS hi system loads will also cause similar cracks and chunks of babbit not where you want them to be.

Google fatigue failures of fluid film bearings and you can find much more than I'm thinking of off top of my head

Regards
Jim P

In post analyzing failures (subsurface cracks, separation, to complete loss of babbit), the two can go

some brief decription would help some comment in..

pls comment. bottom journal bearing. bad bonding or fatigue?

2nd pic

3rd pic

last pic

i am not sure if we can actually pin pointed or prove even if the damaged bearing is having bad bonding. fatigue? a very broad element to involve in.

for me, it is not craking. it is just about to melt due to exposure to high operating temperature. we can se clearly 1/3 of the bearing white metal is melted and the cracking like portion is near to the melted area.

your second pic - is it the other end's bottom journal bearing?

the melted area - is it towards the rotor side or coupling side? bow rotor ya?

i didnt get to look at the final picture jsut now. you may bring bad bonding in for that picture. it is a localised falked portion. then again, the active failure is high temperature.

Aidil
A picture is worth a thousand words.
You obviously had some high heat and pounding going on and, as Valve pointed out, very uneven heating profile.
From what I can see, its not surprising that you have babbit falling out regardless of the quality of the bond.
You need to provide much more detail on vibration levels leading up to this event in order for someone to provide additional help.
Also, is this unit aligned (uneven heat profile)?