StM FIE Pictures

[howtobrew]

Here is a fracture surface of an StM FIE blade that Purple Fencer sent me a couple weeks ago. A quantitive analysis shows that the composition is consistent for the C300 Maraging Steel as required by the FIE.

In this picture, the fracture origin is clearly visible at the inclusion on the left, where it grew by fatigue crack growth. The fatigue cracks are visible as striations or beach sand ripple marks moving left to right in the second picture. It grew to that roughly round shape that takes up most of the center of the first picture, then grew rapidly into a ductile region to the right. the rest of the fracture surface (off screen) is all ductile fracture, ie. fast fracture. (the cobwebby looking surface)

The inclusion is an aluminum silicate with other stuff thrown in: potassium, calcium, sodium, magnesium, chlorine. Typical for inclusion. I don't have a high opinion of the cleanliness of Ukrainian steel. I used to work on the Space Station project with the Russians (and Peton Welding Institute in Kiev), and I learned firsthand that their system did not allow for Quality accountability between material supplier and material user. You had to take it on faith with huge engineering margins. To make a long anecdote short, they had a US-designed equipment test failure which they blamed on our design. During a long telecon it was discovered that they did not even know the (actual) material strength of the aluminum alloy they had used, they had to rely strictly on official engineering margins. They were not allowed to test anything to avoid blame of another state agency. Well it turned out that they had chosen to use an alloy with half of the inherent strength of the one we had specified. Of course this anecdote has nothing to do specifically with maraging steel blades, but from what I learned of their infrastructure 15 years ago, I doubt the general state of their metal cleanliness and adherence to international specifications has changed a lot.

[tiger fencer]

In the first picture is that a cross section of the blade?

[Mergs]

As usual, great pics and a fantastic explaination. Textbook illustrations of fatigue and ductile fracture (it might be noted that the 'cobwebby' look is a result of the cup/cone nature of ductile failure).

I understand your comments about the Russians and ISS. I've worked with them on a couple of 'ventures' and talk about SCARY! And to think that they have the kind of record in space they do. Hmmmm. If they can do it........
Too bad NASA suffers from an extreme case of NIH (not invented here) and is trying to reinvent the wheel, over and over again. Ok, enough soapbox.

Anyway, thanks from an old materials guy that doesn't get to do it anymore.

[howtobrew]

Yes, the first picture is the fracture surface across the blade, you are looking at the top of the V of an epee blade. It broke roughly perpendicular to the length about a foot from the end.

(Yeh, I wasn't sure if cup-and-cone was actually descriptive for anyone who hadn't had Materials Science 201)

The Russian space program seemed to have a motto of: if you build one and it works, you're done." I saw flight hardware that really/actually/truly looked like it was build in the Junior High School machine shop with a spot welder.

[Mergs]

Actually, I was suprised that I even remembered that description!!

As for Russian design philosophy, you have to admire the fact that they spend the time and materials on the REALLY important stuff and boiler plate the rest. The MIG-25 that defected in the '70s was a great example of that. titanium where it made sense and carbon steel in other places. Hell, they even fly leather in their spacecraft!

And their basic aerodynamic theory of 'if you put a big enough engine behind it, anything will fly!' is also time proven.

[howtobrew]

hahaha, I forgot about the leather! You want to know what the MIR space Station was like? MOLD CITY. The leather was rotting from the humidity, and body dust. The US astronauts said that was the hardest thing to deal with, the fact that everything was moldy, because they didn't have requierments to prevent materials that supported mold growth. We learned a lot from MIR to be sure...

[Mergs]

And WE learned alot from Skylab, too! And let the SOB burn up. P's me off to realize that we had more volume in Skylab than all of ISS.