Fracture in diesel engine block near mounting --- are there any indications

[akv1234]

 

[TugboatEng]

From the pictures in your other post, there are multiple fracture locations. This indicates a sudden impact type of failure. This engine block was dropped.

 

[akv1234]

This is an diesel engine fitted in a vehicle what could have caused such an impact

 

[3DDave]

What sort of vehicle? I have seen some amazing work done by clever operators that looks a lot like that damage. Often the operator says "it just happened."

 

[mrfailure]

Pretty big leap to diagnose the block being dropped from just 3 pictures. I cannot even make out directions of fracture propagation (typical if this is a gray iron casting). For this one, you really need to have an experienced failure analyst conduct a structured investigation.

 

[TugboatEng]

This picture tells a lot. The engine has been in service. A defect leading to this severe of a break would have happened immediately.

There is a second crack. What is the likelihood of two such failures happening simultaneously on an engine that is running? Any one of them would have caused serious issue.

The damage is on a corner, much more likely to strike first.

There are no beach marks/corrosion so the failure likely happened abruptly.

I suppose a starter or air compressor mounted in that location could break the block, that does happen. But, I don't think it's likely in this case because of the presence of the second crack. There was a lot of displacement of material for that to happen. Heavy duty engines typically mount the starter in the bell housing so that's unlikely to break the block.

MrFailure is right, everything I say is speculation. These are just my initial observations.

 

[mrfailure]

A defect leading to this severe of a break would have happened immediately.

Not if the defect leads to progressive failures. For example, fatigue damage from a defect happens over time.

There is a second crack. What is the likelihood of two such failures happening simultaneously on an engine that is running?

Quite a bit actually, especially if both cracks initiated and propagated from the same cause. For example, vibrations can cause multiple fatigue cracks at the same time. Also, the presence of one crack as it is growing (e.g. the fracture) can change the dynamics of loading, allowing a second crack to initiate and propagate.

The damage is on a corner, much more likely to strike first.

Stress risers associated with corners make them great locations for any crack to initiate.

There are no beach marks/corrosion so the failure likely happened abruptly.

Not always true. Some materials like gray cast iron do not exhibit these features. Gray iron failures in fact are difficult to diagnose fracture mode for that very reason, so other methods have to be employed to identify likely mode.

There is not enough information in the pictures to identify fracture mode at this point. You can look for evidence to determine if the block had been dropped by looking for distortion or impact damage in the area it may have been dropped on.

 

[TugboatEng]

You can look for evidence to determine if the block had been dropped by looking for distortion or impact damage in the area it may have been dropped on.

Yes, you can see the distortion as the crack in the picture is "open".

 

[mrfailure]

That's a fair point. I'm looking at that area radiating out from the bolt hole as a potential impact area. Makes me wonder whether this could have been from an impact at this location subsequent to (and caused by) the fracture.