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Tourist submersible visting the Titanic is missing 101
- Thread starter JohnRBaker
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Murph 9000
Computer
I can't tell if the hull monitoring system was intended to provide an alarm for imminent failure, or if it was intended to track the cumulative damage and let them know when the hull had reached the end of its useful life, or maybe both. Either approach seems quite high risk because it's a new and unproven technology for this application.
How did they set the thresholds for it?
Could they even reliably correlate the sounds with the scale of the damage?
How did they set the thresholds for it?
Could they even reliably correlate the sounds with the scale of the damage?
1 second is like a geologic time scale. It's a few milliseconds.
--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."
--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."
Alistair_Heaton
Mechanical
I think there is a similar system installed in helicopters to condition monitor blades and other composite structures.
Some over pressure is inevitable. as the inertia of the water inward at some velocity will not be cushioned by anything when it hits the water traveling inward on the opposite side.waross said:
if this was a spherical collapse it would be possible to calculate the over pressure. The unknown shape of the collapse volume and the unknown impact of the disintegration (or not) of the submarine parts makes any attempt to determine the maximum pressure attained at the minimum volume point of the collapse a fools errand.
I can not see much of the energy of the collapse being available to blow off the end caps, More likely the differential pressure would drive them inward upon loss of support of the cylinder. I wounder if we will eventually find they are bent out of shape.
LittleInch
Petroleum
Somewhere I read that one of the ends was basically filled with carbon fibre debris.
The forces and speed of disintegration is difficult to comprehend but given the rigidity of the end caps and the forces on them you would imagine that once the shell tube had given way, the ends would be thrust together at frightening speed and basically crush everything in between into minute fragments.
Then after the milliseconds of destruction, the parts would gently descend to the sea bed which was apparently some 2-300m away other than the metallic ends which would tumble away.
That patent doesn't really say anything much to me as it doesn't really relate the acoustic signals heard to the strength of the material or any determination of fatigue loading. I'm struggling to understand how measuring what sounds to me like damage to the structure gives you any idea of whether it will fail or give you sufficient notice of failure before collapse. There is a sentence about a sudden burst of noise followed by reduced levels leading to an alarm, but given it takes minutes if not hours for the sub to reduce the pressure and loading on the vessel does it actually do any good? Alarms are only of any use if they allow time to reduce the load / pressure and take action before failure / collapse / burst etc. Its these sorts of questions which the normal procedures and checks would ask which clearly were thought of as old fashioned and a barrier to innovation and development. IMHO.
What this thing really needed was a full depth scan and monitoring of the structure to find laminations, cracks and other defects and monitor changes between each dive. Not just a "well it made the same noise last time and nothing bad happened" which appears to me to be the basis of the patent.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
The forces and speed of disintegration is difficult to comprehend but given the rigidity of the end caps and the forces on them you would imagine that once the shell tube had given way, the ends would be thrust together at frightening speed and basically crush everything in between into minute fragments.
Then after the milliseconds of destruction, the parts would gently descend to the sea bed which was apparently some 2-300m away other than the metallic ends which would tumble away.
That patent doesn't really say anything much to me as it doesn't really relate the acoustic signals heard to the strength of the material or any determination of fatigue loading. I'm struggling to understand how measuring what sounds to me like damage to the structure gives you any idea of whether it will fail or give you sufficient notice of failure before collapse. There is a sentence about a sudden burst of noise followed by reduced levels leading to an alarm, but given it takes minutes if not hours for the sub to reduce the pressure and loading on the vessel does it actually do any good? Alarms are only of any use if they allow time to reduce the load / pressure and take action before failure / collapse / burst etc. Its these sorts of questions which the normal procedures and checks would ask which clearly were thought of as old fashioned and a barrier to innovation and development. IMHO.
What this thing really needed was a full depth scan and monitoring of the structure to find laminations, cracks and other defects and monitor changes between each dive. Not just a "well it made the same noise last time and nothing bad happened" which appears to me to be the basis of the patent.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
GregLocock
Automotive
The general field of using accelerometers or mics to monitor structural degradation is called, slightly confusingly, acoustic emissions (AE).
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376
The collapse of the bubble is followed by an equal opposite outward pressure wave, so some separation and scattering of debries is certainly possible.
--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."
--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."
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5
- #309
I reaaly wonder if John Hart_smith predicted this outcome in 2000, see attached file. In particular look at Figure 2. If this structure has been designed using failure envelopes developed using derivatives of the Tsai-Hill or Tsai-Wu ply-by-ply analytical methods, then this issue must be considered in any investigation. Let me explain. These approaches input unidirectional tensile and compression strengths in the fibre and transverse directions and from that test data they generate an elliptical stress-based ply failure envelope. Again, refer to Figure 2 of Hart-Smith's paper.
The problem is that any change in the material strength properties (Hart-Smith uses the example of a weak transverse tensile strength, but a similar outcome could be generated by reducing the transverse allowable tensile strength) will result in a predicted substantial INCREASE in the compression-compression strength as the failure criteria equations redraw the elliptical failure envelope through the adjusted data points. How can a change in the transverse tensile properties result in such a predicted modification of the compression-compression strength? There is absolutely no physical explanation for such a radical prediction. I personally asked Stephen Tsai at an ICCOM conference in Beijing how he could explain this and his reply was "The mathematics said it does". I am sorry, but I am an old dog. Unless I can understand the physics behind the mathematics, it is nothing more than mathematical gymnastics. The coincidence with reality is purely fantasy.
In fact in the attached paper, Hart-Smith asks if the reader would be prepared to participate in the underwater certification tests of submarines designed on the basis of these failure analyses.
I am al;so aware that Mike Hinton (google) et al investigated the veracity of composite failure theories and although, relying on the memory of a 75 year old white guy, the failure theories discussed performed badly.
Now, I have no idea of what failure criteria were used to design the composite shell. I am simply throwing the possible explanation out for discussion. I just hope that five people didn't die just because the mathematics said so.
As a rider, I have fifty years experience in composites and adhesive bonding, including courses in damage tolerance and failure forensics.You won't find too many junior engineers with the wisdom of having kicked most of the stones along the path to knowledge. If you really want to employ the young uninhibited creative engineers to expand the essesnce of your technology, you really must accept the risks that are inherent in your choice.
Regards
Blakmax
The problem is that any change in the material strength properties (Hart-Smith uses the example of a weak transverse tensile strength, but a similar outcome could be generated by reducing the transverse allowable tensile strength) will result in a predicted substantial INCREASE in the compression-compression strength as the failure criteria equations redraw the elliptical failure envelope through the adjusted data points. How can a change in the transverse tensile properties result in such a predicted modification of the compression-compression strength? There is absolutely no physical explanation for such a radical prediction. I personally asked Stephen Tsai at an ICCOM conference in Beijing how he could explain this and his reply was "The mathematics said it does". I am sorry, but I am an old dog. Unless I can understand the physics behind the mathematics, it is nothing more than mathematical gymnastics. The coincidence with reality is purely fantasy.
In fact in the attached paper, Hart-Smith asks if the reader would be prepared to participate in the underwater certification tests of submarines designed on the basis of these failure analyses.
I am al;so aware that Mike Hinton (google) et al investigated the veracity of composite failure theories and although, relying on the memory of a 75 year old white guy, the failure theories discussed performed badly.
Now, I have no idea of what failure criteria were used to design the composite shell. I am simply throwing the possible explanation out for discussion. I just hope that five people didn't die just because the mathematics said so.
As a rider, I have fifty years experience in composites and adhesive bonding, including courses in damage tolerance and failure forensics.You won't find too many junior engineers with the wisdom of having kicked most of the stones along the path to knowledge. If you really want to employ the young uninhibited creative engineers to expand the essesnce of your technology, you really must accept the risks that are inherent in your choice.
Regards
Blakmax
Alistair_Heaton
Mechanical
Just so there is no confusion there will not be any bio matter recovered. So recovering the wreckage is pointless.
It's slightly worry the number of people out there that seem to think its a possibility.
It's slightly worry the number of people out there that seem to think its a possibility.
LittleInch
Petroleum
My understanding is that apart from the metallic end caps and bits attached outside the pressure envelope like the legs, everything else just basically disintegrated. I don't believe any of the carbon fibre shell remains in any reasonable sized fragments which are worth looking at or will tell you anything about the flaws int he material.
I think there is a good reason why no photos have yet emerged of the wreck site.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
I think there is a good reason why no photos have yet emerged of the wreck site.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
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Alistair_Heaton
Mechanical
Yes yes and yes but your into enthalpy entropy tables. But it's unlikely without an external input of energy. The vaporisation temp goes up with pressure. So I could see it in theory but not in real life.
Especially in this case surrounding water is a collosal heat sink at 5 degs.
And the next stage it breaks down to O2 and H2 .
Especially in this case surrounding water is a collosal heat sink at 5 degs.
And the next stage it breaks down to O2 and H2 .
The problem I have is I don't routinely witness (even on video) deep-water implosions, and so have no intuitive grasp of how things would work.
From a practical standpoint, the sub imploded at some distance above the bottom. Anything surviving that was heavy would sink to the bottom in more or less that location. Anything fairly light that survived would pop to the surface. Stuff at more or less neutral buoyancy could drift long distances with any current before ever surfacing or hitting the bottom. I would suspect that would include much of the carbon fiber and any tissue remains.
It has been mentioned above and elsewhere about the diesel effect heating the air. They did have bottled oxygen onboard as well, and it occurs to me that if those bottles ruptured, there could be a considerable amount of combustion taking place very quickly in a very confined area. Rupture of that cylinder would also heat the cylinder itself, for that matter.
It's not obvious to me if that cylinder would bust into splinters or flatten like a can or what, but I would think that would have some effect on how the remains of the cylinder and anything inside looked after the event.
From a practical standpoint, the sub imploded at some distance above the bottom. Anything surviving that was heavy would sink to the bottom in more or less that location. Anything fairly light that survived would pop to the surface. Stuff at more or less neutral buoyancy could drift long distances with any current before ever surfacing or hitting the bottom. I would suspect that would include much of the carbon fiber and any tissue remains.
It has been mentioned above and elsewhere about the diesel effect heating the air. They did have bottled oxygen onboard as well, and it occurs to me that if those bottles ruptured, there could be a considerable amount of combustion taking place very quickly in a very confined area. Rupture of that cylinder would also heat the cylinder itself, for that matter.
It's not obvious to me if that cylinder would bust into splinters or flatten like a can or what, but I would think that would have some effect on how the remains of the cylinder and anything inside looked after the event.
Reverse_Bias
Electrical
Do we even know which way the tube imploded? I've been picturing it the long way since there is more surface area along that axis. I guess it's possible it pancaked and the end caps collapsed together like symbols. Also, doesn't carbon fiber float?
There are videos on Youtube of implosions of rail cars, 55 gallon drums, etc. But all of those are thin-walled ductile structures, so they stay as one piece and crinkle or flatten or whatever. But thick-walled carbon fiber with end caps, it's not all obvious how that would actually fail.
Dissimilar materials: metal, carbon fiber, plastic window, eventually will fail under those temps and pressures.
The entire pressure container should have been of steel.
Chris, CSWP
SolidWorks
ctophers home
The entire pressure container should have been of steel.
Chris, CSWP
SolidWorks
ctophers home
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