Brembo copper sealing washers vs aluminum (aluminium)?

I think it was the plates used int he construction of the Titanic that failed due to brittle fracture when it hit the iceberg. The cold water made the steel approach the glass transition point where the fracture was brittle and not ductile. The same problem occured with the Liberty ships built in WW2.
 
Hi Scrumpy.

I don't think the glass transition point had much to do with it. The ship wasn't made of glass, and steel doesn't behave like glass. The transition point in a glass context refers to the change from an amorphous to crystalline structure. Steel (at normal temperatures) is always in a cristalline state and has no amorphous state or transition point.

Current metalurgical opinion seems to be that the steel of the hull plates was perfectly OK to temperatures well below Zero Celcius. But the wrought iron rivets in the bow section were sub-standard. Rivets recovered from the wreck were tested and showed very high slag and sulphur levels, and were barely up to the job of holding the hull plates together under normal contitions. A collision with a big lump like an iceberg pushed them beyond their capability.

The damaged area of the bow is still buried in the mud of the ocean floor, so hasn't been examined in any detail. But sonar images below the mud show that there were several parallel longitudinal fractures. The most plausible explanation for that fracture pattern is that a few rows of hull plates unzipped along rivet lines.

My interpretation of the inconclusive evidence is that the rivets failed.

Cheers,
Cam

Just wondering: Is the deviation from aluminium washers to the sinking of the Titanic considered as a thread hijack?


 
Cam,
Thanks for the correction, My memory is clearly not as good as it was and I have confused the transition from the ductile to britle failure mechanism with the glass transition temperature. Extract below refers to the Liberty ships, as you point out the Titanic was rivetted.

The grade of steel used to make Liberty ships suffered from embrittlement, in which materials become brittle. Ships operating in the North Atlantic were often exposed to temperatures below a critical temperature, which changed the failure mechanism from ductile to brittle. Because the hulls were welded together, the cracks could propagate across very large distances; this would not have been possible in riveted ships.
 
Studies into Liberty ship failure were required reading when I was an engineering student. Interesting stuff. Cracks most often started from the corners of hatch openings, which were stress concentrators. Absolutely correct about the welded construction allowing cracks to propogate right around the hull. If they had used riveted plates, any crack would most likely stop at a rivet hole or plate edge long enough to allow them to get to port.

In the years since then, steel quality has improved a lot, as well as the understanding of its failure modes and the effects of stress concentrators. Ships and aircraft tend not to fall apart so much these days.

Cheers,
Cam
 
Dellortoman said:
Hi Scrumpy.

SNIP

Cheers,
Cam

Just wondering: Is the deviation from aluminium washers to the sinking of the Titanic considered as a thread hijack?
Click to expand...

naah, pretty much par for the course, still relates to metallurgy, at least it is interesting......... ;)

Paul LeClair
 
stevepm2011 said:
Aluminium banjo bolts + aluminium banjo + aluminium washer + aluminium cylinder should be no problem ?
Click to expand...

The only interaction to be concerned with there would be whatever the brake hose ends are made of.

I am partial to steel banjo bolts, myself, where my personal safety is at issue, don't think I could bring myself to trust aluminum banjo bolts, but that is just me.
 
Just as an aside:

I had a couple of early 70's Jags in the past.
They had aluminium washers on the banjo bolts throughout the fuel system.
Never had a problem with them.....just with everything else.
 
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