The fibers are wound like thread on a spool not wound like a laceration. Please, fix the pronunciation. Btw, I read somewhere that Boeing engineers suggested they have 45° cross directional laminate layers so if a layer failed, the cross directional would help it survive.
Thanks for the video! Could you please share about how to calculate C2, C3, C4 parameters (Characteristic elastic-plastic buckling resistance factor ) using GMNIA calculations as per Eurocode 1993 1-6? Because, it is not clearly mentioned in the Eurocode.
@dr-ing, Ronald, can you please run your numbers with just the hemispheres without the interface rings? My thinking is, the interface rings and bolted connection gave rigidity to each other ... What would each behavior like if the bolts were not a factor? - would they oval in shape??? For context, in one of the reports, they mentioned "ovaling" and I think this is more yiur wheelhouse than mine... Could each section withstand the psi without the bolted connectors ... I have considered the "cylinder-piston pressure from the ends, trying to buckling the carbon fiber hull and therefore the bolts are "useless "... But, ovaling is mention in the report and i am thinking, some point during the implosion (the carbon fiber buckled) and this sudden "release of pressure " created a huge "over pressure " and the interface rings and the end domes "ovaled (during that event)... Because the report identifies the "oval", this means the section that ovaled is now plastic (revealed by the fact that it is in the report as oval shape)...
@@hnrwagner allow me to make a video reply on my channel and that way people can see where to come for the answer and hopefully subscribe to your channel also. I have to find the section in the report where it describes ''oval" and also discuss my position for and against this in reference to before or after the implosion... I have a mechanical engineer who I will mention that is leaning towards before... I am not leaning that direction and simply, I think the bolts and interface would have failed many trips prior (unless they have more data to the contrary - for example your modeling)... Again, I will do a video within a few minutes and post in about two hours. Thank you and goodnight (Germany time now is around 9:30p.m.)
from my experience plasticity has a small influence on the structure until lambda < 1.73, that is also stated in certain design codes, but only of high imperfection amplitudes. if lambda < 1 then is has an obvious influence.
the CEO of Oceangate refused to build a successful test model. Regardless of known dangers, Oceangate built the full scale vehicle, and immediately began selling expensive tickets for an "Explorer's Club" adventure.
I assume it will be impossible to exactly replicate the Titan implosion due to the fibers being sanded down, and thereby changing the strength properties of the carbon fiber hull. We can't know in hindsight exactly where those fibers were sanded down, and exactly by how much. And then the resin or glue was apparently unevenly applied by hand, which will also be impossible to replicate. It's like trying to replicate a kid's carved bark boat. The piece of bark will never be exactly the same, and the carving by hand will never be exactly the same.
It might be a good idea to put the language of the video to English. RU-vid's auto translation thinks the language is German, so the subtitles are not working.
Interesting analysis. I don't know if you said it but apparently the titanium domes were downgraded from titanium grade 5 to titanium grade 3. Stockton Rush did that to save money.
The fiber placed hull looks better but is it “obviously” better quality. The fiber is placed without tension. It is autoclave cured 5 times thru the thickness. During the autoclave cycle the thickness is compacted, reducing the diameter and causing wrinkles.The wrinkles on the outside of the hull are numerous as is seen in a picture in this video. Recently it was shown the wrinkles go deep into each 1” layer. The wrinkles were ground smooth before the next layer, cutting several plies in the process. This not only reduces the compressive strength, it severely affects the local stiffness. Whereas the geometric middle surface is nearly exactly cylindrical, the local stiffness deviations causes the stiffness middle surface to be wavy in the wrinkle regions, which are very numerous. So the buckling capability will be reduced.I would have scrapped this hull after the first autoclave cure. Without the autoclave, it would have looked like Swiss cheese. The filament wound hull is wound with tension in the hoop direction and develops about 1 psi interface pressure with the mandrel per ply. That adds up to 400 psi, but won’t be that high due to compaction. If the mandrel is stiff enough, the positive hoop tension will be maintained to the end. They don’t autoclave composite pressure vessels. I saw someone try it and it did just what this one did and failed prematurely. I’ll put my money on this one to out perform the pretty one. There’s not much difference in the hand and machine placed axial plies.
It would be interesting to model the wrinkles in your buckling model. Geometrically, the hull was made on a nearly perfect cylinder, so the hull deviates very little from a circular cylinder. The thickness is also constant. The wrinkles could significantly warp the structural middle surface and degrade the buckling load. I don’t think even delams would have much affect because of high inter-laminar compression and friction.
I love how you recognize the crash site, but the failure mode from the animation doesnt match it at all. The window didnt collapse inward. It got thrown outwards by the hull tearing on its join to the front titanium ring.
Interesting. I wonder about your hexagonal structure and if it was inside of a cfrp cylinder, providing some reinforcing of the cylinder, how it might change the modelling. Keeping the internal volume the same as the Titan, with the same wall thickness of the cfrp cylinder or better. My intuition says it should help considerably, but I realise intuition can be wrong.
@@hnrwagner Ok, I get that, sorry I didn't mean to demean or belittle your design. It was just a suggestion, If I could do the modelling myself I wouldn't have bothered you.
Very interesting. As stated in the Q and A period, where the ends of the shell mated (by bonding) with the end hemispheres, there is a combination load that must be accounted for. In the center of the shell, hoop stress should be the driving load for design, but at either end a bending load is introduced when the shell and end caps don't strain identically. The longitudinal fibers pick up this load. In the design of the shell, hoop stress should be evaluated against compression allowables, and checked for buckling. Only the circumferential fibers can be used in those calculations. Buckling under hoop stress would be evaluated by assuming that the successive circumferential plies are all concentric. However, they are not concentric after the first few plies, they are budged outward, and some of those plies were actually sanded off during fabrication. Therefore, in the as-build condition, structural calculations would have to include post buckling analysis, with knockdowns inluded for the prosity, resin starved conditions, disbonds and contamination in the layup. Watching the video where the end rings were bonded to the shell made me want to pull my hair out. But, that said, I suspect that the sheared flanges on the rings were secondary to the implosion, which is consistent with your FE illustration. I agree with you that the strain gages warned the operators that the shell was degrading, which they rationalized away. They would have been of no use in alerting the operator that an implosion was imminent. I'm suggesting that the shell failure was due to buckling. When the shell wall started to buckle, total collapse would have progressed instantaneously. I haven't heard anyone suggest that "cracks" in the composite might have allowed water to seep in, which, upon expansion due to freezing, would have extended the defect with eact freeze/thaw cycle. With the state of the debris recovered being so poor, I'm not sure the NTSB guys would be able to find evidence of it. Love your work. Thanks.
I would love to know how the proper interface of the titanium rings with the cfrp cylinder would look like, unfortunately I have no expertise in this area
@@hnrwagner Sorry, I didn't mean the CAD as a solid, I meant the laminate definition, i.e, is it modelled with solid or shell elements? Shell elements can't account for transverse deformation/shear with Kirchoff-Love, and given the thickness of the cylinder, these will have been significant. Typically, in Ansys, I would model this using either solsh190 elements to account for Mindlin-Reissner, or with solid elements with full 3d elasticity.
Very Interesting, is it possible to share the CAD or at least the datasheet you used to construct the model as I am intending to simulate it in Ansys and why not compare the results with the one you got
Times codes: 0:00 - Intro 4:45 - Titan Digital Twin 7:38 - Manufacturing of the Titanium Aft Dome 8:50 - Analysis of the Titanium Hemisphere 14:02 - Manufacturing of the Titanium Front Dome 15:20 - The CFRP Cylinder and its manufacturing 17:48 - Cross-section details of the CFRP 18:59 - Analysis of the CFRP Cylinder 19:33 - CAD model of the TITAN 20:09 - Analysis of the CFRP Cylinder 2 21:52 - Design of the CFRP Cylinder 2 27:10 - How the TITAN looks like according to ASME Design Code 27:55 - This TITAN sub would never implode ;) 28:30 - Summary of Dives to the Titanic 29:15 - Fatigue failure estimate 30:36 - TITAN debris underwater cam 32:18 - Pressure gradient vs. Human Body 33:40 - How much energy the Implosion released 35:20 - Acoustic Sensors 37:19 - NTSB Reports 39:40 - Interface Rings to CFRP Cylinder 41:45 - Implosion Simulation 42:38 - Interface Ring failure 44:00 - Q&A Session 46:00 - Realistic implosion simulation with Imperfections 53:31 - Strain gages Analysis 55:30 - More questions regarding imperfections 58:31 - Q&A Session end 1:00:41 - updated Implosion Simulation - CFRP Cylinder Fracture 1:00:41 - updated Implosion Simulation - Acrylic Viewport Failure 1:00:41 - updated Implosion Simulation - Adhesive Interface Failure
Why did the Sub collapse in a few milliseconds?Why not in about 0,2 seconds?The time the watercolumn falls about 2 meter(ca. the height of the sub)with the normal 1g when the sub breaks. Or is because the water is pressed to a smaller volume at about 300bar and releases the enegy like a air-rifle? But water in 3000 meter is only comprimated to about 1,5% more density whereras air would have 300 times more density at this pressure
Now that images and footage of the wreckage have been made public, and indicate that the failure occurred near the front of the vessel towards the bottom of the titanium ring, pushing the remaining contents towards the back titanium dome, would you consider crafting a new simulation to reflect the new data?
If this had happened upon dissension and they saw nothing, felt nothing, knew nothing that’s one thing but even though they felt nothing and saw nothing….. they knew what was coming hence the attempt to resurface, from the moment of attempting to resurface til the implosion had to be the most frightening moments any human being had experienced, the fear energy in them all would’ve been strong enough to push and electric subway car! They knew!
