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In the summary they state: All the reported experimental zinc electroplasticity (EP) data were developed at current densities orders of magnitude higher than t
by magicalhippo 2y ago
In the summary they state:
All the reported experimental zinc electroplasticity (EP) data were developed at current densities orders of magnitude higher than those possibly present in the Arecibo Telescope but measured in laboratory experimental periods that were orders of magnitude shorter than the telescope's socket zinc service.
There are no reported experimental data concerning low-current, long-term EP, which the committee has lumped together under the term "LEP", affecting zinc's creep mechanisms over decades.
The timing and patterns of the Arecibo Telescope's socket failures make the LEP hypothesis the only one that the committee could find that could potentially explain the failure patterns observed.
Accelerated aging is, as far as I know, pretty much standard in the industry. Nobody can wait 20 years to find out if a certain material is good enough or not.
However, the real failure seems to be the lack of urgency when they signs started to show up:
Upon reflection, the unusually large and progressive cable pullouts of key structural cables that could be seen during visual inspection several months and years before the M4N failure should have raised the highest alarm level, requiring urgent action. The lack of documented concern from the contracted engineers about the inconsequentiality of the cable pullouts or the safety factors between Hurricane Maria in 2017 and the failure is alarming.
- nick3443 2y agoSounds like it was a blind spot for the engineers due to the normally bulletproof service history of zinc spelter cable terminations in structures.
- potato3732842 2y ago>normally bulletproof service history of zinc spelter cable terminations in structures. They're relatively new, they're relatively expensive (which saves them from being used in the worst of the applications) and like most things inherent to steel cable and whatnot they tend to get employed in situations where safety factors are generous. Don't count your chickens before they hatch.
- nick3443 2y agoI am not an expert, I read this in the report: The long-term zinc creep failure of the Arecibo Telescope sockets and the subsequent cable pullout has never been documented elsewhere despite a century of zinc-filled cable spelter sockets use. 17 The type, size, length, and fittings of the cables used in the Arecibo Telescope (whether the original cables constructed in the 1960s or the auxiliary cables installed in the 1990s) were catalog-selected items, not at all unusual, with decades of proven performance. Exten-sive structural modeling of the Arecibo Telescope, independently confirmed by laser cable sag surveys, validated that under all static and cyclic loading conditions, the cable loads barely exceed half the nominal cable strength. While PLC can occur at stresses well below yield, such a creep failure has never been reported in spelter socket zinc.
- hinkley 2y agoI think we might need to send some microbiologists to do their own forensics. You have a mechanical failure that can’t be seen in the labs and isn’t reproducible at other sites. Suggests something environmental. Like when natural fiber army gear starts dissolving in the jungles of Vietnam. Could be direct action, or a side effect of a chemical in plant or animal detritus. Like pigeon poop on car paint.
- madaxe_again 2y agoThe paper posits that it’s due to low frequency electromagnetic induction in the tethers from the observatory operations, which is a pretty unique environmental factor.
- hinkley 2y agoOooh. Active galvanic action will ruin your day.
- madaxe_again 2y agoNot galvanic action, apparently, but rather a sort of phase creep within the zinc as a result of putting some of it in an excitation state. They aren’t sure though, as there hasn’t been much research on the topic.
- deskr 2y ago> The lack of documented concern from the contracted engineers about the inconsequentiality of the cable pullouts or the safety factors between Hurricane Maria in 2017 and the failure is alarming. This is crazy. Basically cables were pulling out for months and years and no one raised the alarm? In many industries that could be a criminal or career ending malpractice. Are the "contracted engineers" liable?
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- magicalhippo 2y agoIn chapter 5 they go into how the ownership was transferred to the University of Central Florida (UCF) at the start of 2018, after the hurricanes in 2017. It seems unlikely that UCF had adequate time and resources to review and understand the Arecibo Telescope's original 1963 design, the 1974 upgrade, the structural inspection and maintenance records produced for nearly 50 years, [...] and the key factors, such as the wire breaks and cable pullout of the sockets and their significance on the strength and integrity of the structure. The measured cable pullout may have appeared "normal" to [the UCF staff] and was not on their radar as signs of structural distress. The lack of concern may be because a small cable pullout was present from the beginning, and no one in authority had previously raised an alarm But yeah, seems weird no-one of the contractors tried to raise an alarm.
- hinkley 2y agoI bet there’s a r/MaliciousCompliance in Spanish out there somewhere about how UCF cancelled existing maintenance contracts and hired new companies to keep an eye on the equipment, and did it so rudely that the old company didn’t hand over important warnings like this. Discontinuity could explain problems like this readily.
- renewiltord 2y ago[flagged]
- mkesper 2y agoAnd further: The reliance by the consultants (before and after the first cable failure in 2020) on a perceived allowable pullout of one-sixth of the cable diameter, which should only be seen at loading at 80 percent of ultimate cable strength, does not align with the AASHTO M 277 standard guidance. The committee, therefore, disagrees with the suggestion made in the Thornton Tomasetti, Inc. (TT) 2022 report, Arecibo Telescope Collapse: Forensic Investigation,13 to use the D/6 limit as a threshold for slip monitoring.
- Iolaum 2y agoI would be curious if there are any accounts/reports of people working there - especially engineers - that could verify the claims of no alarm being raised when the first structural failures started showing up. It is often the case that people on the ground report such things but when "reports" are written for the higher ups, facts get "massaged" according to expectations.
- 77pt77 2y agoBearers of bad news get shot. Everyone working in large corporations knows this.
- lazystar 2y agobeing a bearer of bad news is a sign that you are not disagreeing and committing.
- photon_rancher 2y agoI was on the suspended section about a year before collapse - everyone could tell it was about to fail. Visible stress in rusty beams, old cables, and failing concrete. I think it just came down to underfunding at the end of the day - there was no money available to ask for even if the alarms were louder. And for most applications it was obsoleted by the larger new telescope in china, so there was no large push to turn that ship around from the wider scientific community.
- thimkerbell 2y ago[flagged]
- magicalhippo 2y agoI think absolutely not, for several reasons. First off, the report mentions this failure of the zinc filled sockets never been reported elsewhere before. Secondly, even if it had, the report mentions that written documentation of inspections and so on was spotty and inconsistent. That said, if the failure mode had been published before, and inspections and maintenance was written down in a consistent and detailed manner, then perhaps an LLM-based tool could have linked the two. I'm thinking of a RAG-like search thing that compared inspection reports with published documents. Alternatively just assisting a human in finding relevant published reports.
- _yb2s 2y agoAs a sailor that uses similar fittings in sailboat rigging… the idea of not treating a cable pullout from a terminal as an emergency is absurd. If that happened on a sailboat rig I’d assume it had a remaining strength of zero and will fall in seconds or less- and take the most rapid possible action to keep the structure from coming down by deloading the shroud and rigging an emergency replacement.