How Does Aluminum Cut Steel?, page 2
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reply posted on 20-11-2007 @ 04:03 PM by Griff
This could possibly be the answer folks depending on whether the steel was high strength or regular structural steel.

Structural steel Ultimate strength = 400 MPa
High strength steel Ultimate strength = 760 MPa

Aluminum alloy Ultimate strength = 455 MPa

Source:
en.wikipedia.org...

Note that this is tensile strength.

Shear could be different.

In general: ductile materials fail in shear (ex. aluminum), whereas brittle materials (ex. cast iron) fail in tension. See tensile strength.


en.wikipedia.org...

Actually, the steel would be under shear while the plane is under compression. Still looking to see if I can find easy numbers to verify.

But, I believe that since aluminum fails in shear that the Ultimate strength of aluminum would be in shear and since steel fails in tension first, the ultimate strength is in tension. So, the shear strength of steel could be higher. Still looking into it. It's been a while since I've had materials science.



From another thread that I just posted on.



reply posted on 20-11-2007 @ 04:58 PM by tep200377
reply to post by ULTIMA1




For ONCE read the OP title, and stop saying things you CANT back up! You do this every god damn time. You say things like a 8 year old boy that doesnt care if his wrong or right.

The OP title: HOW does aluminium cut steel?
My example: HOW does water cut steel?

The PRINCIPLE is JUST THE SAME!

Its pure mathematics, but it seems you only understand what you want to understand. And you just wont understand regular textbook principles like this..


reply posted on 20-11-2007 @ 09:23 PM by dionysius9
reply to post by ULTIMA1





Uh, no. The instant the pressure is relieved, the metal turns hard again.

And pressure doesn't heat metal. Bending it can warm it up a little, but a pair of scissors cutting through an aluminum can doesn't heat up the aluminum. What it does is create a highly focused pressure point allowing that point to become liquid. The area that is called "liquid" is microscopic, and immediately returns to a solid metal once the pressure is reduced back below the threshold of phase change.


As for aluminum looking bright yellow and flowing like a liquid, it just doesn't happen. All metals have a physical property called emissivity. It is a measurement of how much blackbody radiation they emit relative to temperature.

The color and behavior of that material seen flowing out of the WTC is entirely consistent with a metal consisting of at least 90% iron being heated to 2,750 F. As you all know, no hydrocarbon fuel can reach this temperature in a 21% oxygen atmosphere.


Blackbody radiation theory (which is well understood in physics) dictates that if a material has this emission spectrum (bright yellow) its temperature must be around 2750 F. This clearly presents a problem, because no common-sense answer is available to explain the existence of material at this temperature.


To get something this hot, you must provide an exothermic oxidation-reduction reaction capable of those temperatures. In other words, you need a fuel which can combine with oxygen and result in something very very hot. All burnable fuels that fall under the category of hydrocarbons (diesel fuel, gas, jet fuel, wood, plastic, paper, etc) will only reach a maximum of 1800 F in a 21% O2 atmosphere. If you want it even hotter, you gotta up the oxygen concentration and/or change what type of fuel you're burning.

If you take Iron III Oxide and let it combine with Aluminum, the oxygen on the Fe2O3 gets ripped off by the Al in a chemical reaction. In a sense, the rust is "burning" the aluminum. This chemical reaction allows a maximum temperature of about 4,500 F. This is the chemical combination in "Thermite". VERY hot.


If thermite was used in the WTC, then that would explain the source of oxidizer which would be needed to keep the hot spots hot weeks afterward.

If you take a candle and cover it, the flame goes out because it quickly uses up all the oxygen near it. At the bottom of the rubble pile in the WTC, burning materials would have done the same thing. They would have used up all the oxygen, and gone out like a candle flame before too long. But explaining how there could be so much heat down there so many weeks later is difficult, unless you add an oxygen source which can supply heat-creating chemical reactions the oxidizer they need to keep going, producing heat.


reply posted on 20-11-2007 @ 11:59 PM by Stillresearchn911
reply to post by Griff



More importantly though, as commercial vehicles have certain "limiters" on them to prevent them from say going to fast. Dont these commercial jets have any kind of "limiters" on them to prevent some maniac pilot from flying the # out of his 757/767?? I figured this would be hard information to find, so Im sure one of the pilots here might know.


reply posted on 21-11-2007 @ 12:56 AM by Kamikaze905
Originally posted by Stillresearchn911
reply to
post by Griff

Dont these commercial jets have any kind of "limiters" on them to prevent some maniac pilot from flying the # out of his 757/767??


Exept from the "clacker" . a aural overspeed-warning there's nothing preventing the pilots from flying the aircraft into bits and pieces.

The so called 9/11 internet investigators are talking about a software limitation that prevents the aircraft from doing this and that, fact is: there's no such thing on any Boeing in manual flight.
There are several layers of speed-protection depending on the level of automation in use, but all it takes to disconnect it is a push of a button.
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