Why don't railroads need expansion joints?

The title of this video - which might change since I'm writing this up just a day after it was posted to YouTube - is a bit misleading. The actual question in the title - why don't railroads need expansion joints - is only answered in the last half minute or so of the video and is answered more thoroughly in a Practical Engineering video that I'll post after a jump.

The bulk of the video is spent explaining how railroad welds using thermite work. The video explains the nuances far better than other thermite videos I've posted before, explaining why the rails must be aligned and peaked, why the rails must be preheated (including a nice demonstration of heat treating), how the crystal structure changes as a result of the weld, and eventually why the rails don't need expansion joints.

This is the second of at least three thermite videos from Dr Derek. I thought I'd posted the first video to both blogs, but I can't seem to find it, so it'll likely show up next week.

What does it mean to be a metallographer?

Sprechen sie deutsch?

Ja, aber nur ein bisschen.

In case you don't speak German, the ZEISS folks have provided handy captions so Toni can take us on a bit of a tour to show what a metallographer does.

I will say that there are some metallographers in the world who don't necessarily use exclusively ZEISS microscopes, though, in spite of what this video shows.

What is the NEW Silver Play Button REALLY made of?!

The video description doesn't remotely need that ?! at the end.

That being said, the process that the youtubers here go through to find out what specific elements are in the 'silver' play button is fascinating. The (?) Energy Dispersive X-ray Spectrometer is something that's new to me.

I'm particularly fascinated by the results at 5:39 showing the elemental makeup at various depths of the 'button.'

Yeah, all that's interesting, but what's the 'gold' play button award made of? And what's beyond the gold button?

Engineering the Strongest Foam in the World

I'm not sure I would want the metal of my boat to look like the Swiss-cheese-ish piece of metal in the video still above. It just wouldn't instill confidence from me and - I would imagine - my fellow passengers.

Still, the decrease of weight without subsequent decrease in metal strength is a fairly perfect pursuit for research, particularly as it's being undertaken by Nikhil Gupta at NYU Polytechnic.

Check out either of the two articles that cover the same content as the above video and start getting ready not to worry about the 'holes' in your boat.

• A metal composite that will (literally) float your boat
• One of the strongest, lightest metals ever made is less dense than water

MaterialsScience2000

I love seeing the crystal grains develop as the acid etches the metal surface. It's just gorgeous.

The eight-and-a-half-minute video above shows the preparation of a few different samples, some of which show crystals large enough to be seen by the human eye as well as a few samples that have been etched through natural processes over time.

MaterialsScience2000 has ten total videos posted, and many of them are worth a watch, including a thorough explanation of the tests being preformed. Check out these, too...