Wikipedia:Reference desk/Archives/Science/2018 June 5

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June 5

Terrorist Explosions and Tyres

I know that vehicle tyres are made out of quite tough rubber. But having seen numerous bomb explosions in India, I am amazed to see that while toughest of material twisted by sheer force of modern plastic explosives like RDX's action (stoutest metals like barrels of SLRs twisted to "U" shaped things). But strangely tyres of the vehicles turned upside down (or lying on their sides) - due to awesome force of the bomb which should have melted or even vaporized the rubber of both tyre and the tube inside it (most models like Ambassador still use the traditional airtube-inside-the-tyre instead of "tubeless" system which I think is today the standard in the west), but as I have seen both in media and even live, they are not even reduced to sherds but were as good as they were before the bombing, while the body of the rest of the vehicle was twisted and turned like a tin-can stepped upon by an elephant, it's armoured-plates in doors, roof and all now a part of the mess. Can someone please explain why nothing happens to the tyres ?  Jon Ascton  (talk) 04:48, 5 June 2018 (UTC)

• Your post seems to contain two incorrect preconceptions about things work (leading to the apparent paradox). I would say clearing those is not a clear "answer" though since (as is often the case) fully solving the question requires horribly complex calculations of 3D phenomena.

1. During quick combustion events (such as a bomb exploding), while the gas temperature rises a lot (by thousands of degrees), the temperature of solids nearby does not rise that much. One of the best-documented examples is the internal combustion engines, where during combustion the engine walls rise by 10 to 50°C, but that happens only within the first mm or so of metal (see for instance this classic article (paywall)). It is hard to compare with the bomb case (on the one hand there is more energy per unit of time, on the other hand it is probably not a confined medium so gas temperature may still be lower) but I very much doubt that anything would get melted or even vaporized, temperatures should stay relatively low.
2. Rupture mechanics can be deceiving; it happens that softer materials bend but do not break while harder materials resist and eventually break, depending on the exact constraint applied. If you apply the same stress (= pressure) to both metal and rubber, then what matters is the yield strength and that is going to be much smaller for rubber than for metal (this source gives about 25MPa for rubber when it is in the hundreds for most common alloys). However, if you force a certain strain (= deformation) then metals deform reversibly "only" up to 10-20% while elastomers can deform reversibly up to 700% (according to our article, I didn't check the ref).

Tigraan^{Click here to contact me} 07:25, 5 June 2018 (UTC)

...For example, whacking a car with a sledge hammer makes a big dent, but whacking a tire (aka: tyre) with same force does nothing much. 2606:A000:1126:4CA:0:98F2:CFF6:1782 (talk) 04:33, 6 June 2018 (UTC)

When there is a risk of bomb attacks, it's best to dress up like Michelin Man. Count Iblis (talk) 11:59, 6 June 2018 (UTC)

Michelin Man doesn't work as a bomb suit, as the blast goes between the tyres. Bomb suits are more like the Dendra panoply. Although the overlapping plates being staggered outwards and downwards must have made this an armour that was susceptible to anyone stabbing downwards, it's how the usual Felix suit is arranged. Andy Dingley (talk) 12:44, 6 June 2018 (UTC)

Felix suit → [1] —2606:A000:1126:4CA:0:98F2:CFF6:1782 (talk) 02:04, 7 June 2018 (UTC)

[2] Andy Dingley (talk) 17:27, 7 June 2018 (UTC)

• Tyres are damn near indestructible. This is just one problem with recycling them. They're a composite material of a soft rubber and many high tensile cords. They have an enormous resistance to blunt impacts - why they survive bombings, why they're used as fenders on tugboats. Andy Dingley (talk) 12:44, 6 June 2018 (UTC)

Etymology of Zeuctherium

Hello. What could the first half of the name Zeuctherium mean? Thanks.--Leptictidium (mt) 15:13, 5 June 2018 (UTC)

The original paper describing the fossils (from the journal Vertebrata PalAsiatica) is available online, but it's (mostly) in Chinese, and is only a scanned version so Google translate etc can't cope with it. If you can find someone who reads Chinese they might be able to identify the etymology. AndrewWTaylor (talk) 15:49, 5 June 2018 (UTC)

I would ask that in the Wiktionary Tea room. --31.0.121.29 (talk) 15:53, 5 June 2018 (UTC)

Preemptive therapy

What is the defintion of it? --31.0.121.29 (talk) 15:36, 5 June 2018 (UTC)

Basically it seems to mean "giving the treatment before the illness" - for example see here (first Google hit for the phrase), which is about its application in transplant surgery, and the prevention of rejection. AndrewWTaylor (talk) 15:52, 5 June 2018 (UTC)

That article has a great overview of the terminology for various related prophylactic approaches. DMacks (talk) 18:15, 5 June 2018 (UTC)