Timeline for A city to last ten million years: Construction
Current License: CC BY-SA 3.0
11 events
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| S Jan 19, 2018 at 19:22 | history | suggested | Gryphon | CC BY-SA 3.0 |
Fixed spelling and grammar
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| Jan 19, 2018 at 19:06 | review | Suggested edits | |||
| S Jan 19, 2018 at 19:22 | |||||
| Mar 22, 2015 at 10:29 | comment | added | hyde | @Mark While I was not aware of terminology "fatigue limit", that's kinda what I'm counting on here. Even accounting for aging effects like atom migration, erosion and reforming of surface oxide layer, etc, the chosen material should remain strong/tough enough that no "fatigue limits" if any type are exceeded. Then we should be able to estimate how many atom layers are lost per year, and multiply that by desired minimum lifetime. | |
| Mar 22, 2015 at 7:52 | comment | added | Mark | Fatigue life is strongly dependent on load. In the lab I worked at, the low-cycle fatigue machine could break a sample in a few tens of cycles, while at the other end of the spectrum, steel (but not aluminum) that is never loaded above the fatigue limit has an infinite life, or at least one so high that traditional techniques can't find it. | |
| Mar 22, 2015 at 6:51 | comment | added | hyde | A cylinder of ordinary car can easily go through, roughly (500 Mm / 50 km/h * 60 minutes * 2000 rpm) 1,2e12 thermal cycles without needing to be retooled (feel free to re-check my math, I did it only once). 10 million years is just about 3e9 day-night thermal cycles. Migration of atoms is certainly a possible issue, but not something that couldn't be accounted for, and actually taken advantage of (for example to help maintain perfect composition of the eroding oxidation layer at the surface over time). | |
| Mar 22, 2015 at 6:23 | comment | added | Mark | I've got a materials-testing background. Over a timescale of millions of years, you're going to encounter effects that are generally ignored as being smaller than the rounding errors in current test procedures. I'd expect effects like metal fatigue from day-night thermal cycling or migration of individual atoms within an alloy to become significant on those scales. | |
| Mar 22, 2015 at 6:08 | history | edited | hyde | CC BY-SA 3.0 |
added 49 characters in body
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| Mar 22, 2015 at 6:07 | comment | added | hyde | @Mark I am no material engineer, so I can't give exact figures, but since this angle, extrapolate from current materials, wasn't covered by other answers, I felt it was valuable answer. But perhaps I delete it then. | |
| Mar 22, 2015 at 6:06 | comment | added | hyde | @Mark This is "material like we do today, except implemented with use future technological improvement". That isn't unobtainium, at worst it is handwavium. And of course we have "hints" of what could last 10 million years, as we need to know how often the parts made from current materials needs to be replaced before chemicals start to spill from factories and planes start to drop from the sky (more often than these things happen today). Scaling down the wear to "normal weather conditions" and larger material thicknesses shouldn't be too hard. | |
| Mar 22, 2015 at 5:54 | comment | added | Mark | "Make it out of unobtanium" isn't a very good answer. Ten million years is enough time to carve the Grand Canyon or raise the Cascade volcanoes. We don't even have hints of what a material that could last ten million years without being eroded or corroded would be like. | |
| Mar 21, 2015 at 8:13 | history | answered | hyde | CC BY-SA 3.0 |