What I do at SNL: Part 2

People are always asking about what I actually do at my job at Sandia National Laboratories. I could claim that my work is too sensitive to discuss because it's related to national security or something, but (1) that's just not the case, (2) my research will be published in a public journal, and (3) that would stop me from talking about it (which isn't much fun). This series of posts will attempt to explain the basics of my work, but I can't promise it will be interesting or easily understood.

Last time I explained a bit about grain growth.

The Engineering: Pinning

Generally grain growth is undesirable anywhere outside of the manufacturing process. We usually strive for polycrystalline materials to have a fairly small grain size, and for the grains to stay small. This is mostly driven by the inverse relationship between grain size and material strength. There isn't a rigorous model that defines a specific mathematical relationship, but in general, the smaller the grains are, the stronger the material is.

With the goal to slow down or prevent grain growth in mind, engineers noticed that one solution is to pin the boundaries with particles of another phase. Usually the other phase is just something composed of different elements. In steel for instance, the main phase is mostly iron (with small amounts of carbon and other elements). The second phase might be really high in carbon, and only have trace amounts of anything else. The most important thing about the second phase phase particle is that it is inactive, meaning it doesn't move, grow, shrink, etc.

This drawing illustrates how pinning would work:


On the left, the curvature of the blue and red grain boundaries causes them to move as the arrows indicate. This allows them to minimize their length, and therefore is favored by the system (because it lowers the energy). However, if you introduce second phase particles, as in the right image, the boundary can only move a little bit (until it becomes completely straight) before it's pinned. It can't move anymore because any motion would have to increase its length.

In all the simulations I do, pinning is involved. This makes the system behave much differently, and as I'll explain in a future post, may or may not lead to the desired effect.

All I have to say...

Is Mexican enchilada dinner followed by swimming in the pool in the evening. What a way to live!

-Ashlee

P.S. Yes, I'm enjoying it so far, in case you're wondering. But this is the time where they try to inspire us. Because the actual Institute is supposed to be REALLY tough.

Back In Phoenix!

Well, I've finally returned to Phoenix. It's beautiful here and the pool at the hotel is very tempting (though sleep is as well). I think that I'll go swimming after the evening session tonight maybe.

The flight here was rather uneventful. I left cold and rainy Billings this morning at 10am and arrived in Phoenix at about 11:30. The only problem was that I arrived at a little airport in Mesa and not Skyharbor International, like I thought. Which meant that the hotel didn't have a shuttle.

...62 dollars and a taxi ride later I arrived at the hotel. *sighs*

In any case, I'm here now and I've registered, attended my first two sessions, got my picture taken for a book, and finally settled down a bit.

My roommate is a girl named Jade. She's very nice. She'll be getting up at 5am to go running in order to train for a marathon.

I'm going to just sleep a little longer!

Tonight we have one more session. In my down town I think I'm going to get some miscellaneous work done (applying for financial aid for graduate school, updating my resume, etc).

Hope everyone is doing well. And I'm sorry for the lack of pictures! I just don't have my camera yet. I think it's still in storage.

-Ashlee

What I do at SNL: Part 1

People are always asking about what I actually do at my job at Sandia National Laboratories. I could claim that my work is too sensitive to discuss because it's related to national security or something, but (1) that's just not the case, (2) my research will be published in a public journal, and (3) that would stop me from talking about it (which isn't much fun). This series of posts will attempt to explain the basics of my work, but I can't promise it will be interesting or easily understood.

Introduction: Grain Growth

Almost everything that's made out of metal has a polycrystalline structure. This simply means (as you might have guessed) that it's made of many separate crystalline areas. These areas' atoms are arranged in a perfect lattice, and the difference between any two areas is just the orientation of the lattice. The term grain is used to describe one crystalline area, and grain boundaries seperate them. This picture shows a few grains, and how the atoms' arrangement gives rise to the structure:

There is no difference between the red, blue, and green atoms, but it's easier to see that they are actually oriented differently when they are colored. This structure has three unique grains and three grain boundaries.

You can probably see that there is extra space between the atoms at the boundaries, and you can imagine that there would be missing bonds at the boundaries also. Because of these reasons, this structure isn't the most stable. It would be more stable if the grain boundaries disappeared and all the atoms were arranged along the same lattice. This would eliminate the extra space and maximize the number of bonds (which are favored).

Grain growth is the process that materials go through to minimize grain boundary area (or length in the 2D example above). If red atoms along the red/blue boundary were to move slightly so that they lined up with the blue atoms, they would effectively become blue atoms, and that boundary would move. Eventually all the red atoms would align with the blue atoms, the red grain would disappear, and the grain boundary itself would also disappear. (If you stop to think about it, grain growth is a misnomer: for any grain to grow, one or more other grains need to shrink. However, the average grain size increases, so the name makes sense from a statistical point of view.)

Because the atoms have to move, grain growth usually only occurs at high temperatures (meaning close to the material's melting temperature); therefore it doesn't happen in bridge metal, or a pop can. It can happen in places like a jet engine, and is used during many manufacturing processes.

At the most basic level, my job is simulating grain growth. Next time I'll explain pinning, which is a way that grown growth can can be slowed, or even stopped.

Wolfram|Alpha

Today I read about Wolfram|Alpha on a blog (Geeks Are Sexy). I didn't think I was going to be very impressed by it, but then I watched the screencast:

http://www.wolframalpha.com/screencast/introducingwolframalpha.html

This site looks like a search engine, but it's really more akin to an internet-enabled graphing calculator. They've farmed the internet for data, and built a tool to present make it extremely quick to access, view and compute using their database.

Take a look, and see what you think. Watch the screencast first, just to get an idea of what you can do, then play around on your own.

More pictures, please.

Wow. I was just looking over our blog and I realized we have a lack of pictures! So, here are some for all of you =)

Audrey - The Cookie Monster!


Audrey in a Bath (Yes, yes, those forever-embarassing naked bath pictures).


Audrey loves to giggle, but you have to know how to make that grin come to her face. She can get the whole room laughing in no time with her personality.

And here's a couple of pictures from graduation!


This one was taken in Station Square before graduation. We enjoyed a beautiful day there shopping and seeing the sights!


This is at the Pirates game that we went to. It was a ton of fun (even though they lost). For a couple of people there, it was the first 'pro' sports game that they've gone too! It's a great memory and I'm glad we could all have fun there.



Here's a picture of Grandma Judy and Papa Dean on the top of the incline. Those lights behind them are the skyscrapers of Pittsburgh.


I can't believe that we're actually done there! The whole day had an almost surreal feel about it. We definitely had some good memories, but we're really looking forward to the future.


So, we're walking away from Carnegie Mellon now. We learned a lot there and it will always be part of our lives. Will we miss it? Probably parts of it. But right now the future is so exciting that I think we'll be kept busy enough!

A Little Time at Home

Ashlee here, writing from home in Wyoming. I've been pretty busy over the last week that I've been here, though my time home has been restful as well. I've enjoyed seeing my family and catching up on things with them. I also stopped by my old highschool and saw some of my teachers there. It's always nice to chat with everyone from Sheridan My family and those teachers are the ones that built such a strong network of support for me and I owe a lot of my dreams to them and all they've done for me.

I have a lot of reading still to do before institute. And mom wants me to go through boxes of my stuff that she has stored in her garage. She wants to start transferring that stuff to Todd and I, now that we're thinking of getting a house. I guess this means I'm really growing up - I get to store my own stuff at my own place. 

Like I said, it's been a whirlwind here since I've been home. There are so many people to see and talk to and spend time with. My friend from High School, Hillary, is coming up later this week. It's going to be good to see her again too. 

One of the things I've thoroughly enjoyed while being home is being able to spend some time with my adorable niece, Audrey. She's grown up so much over the last couple of months! 

Brandon and Mallory are such good parents. I've really enjoyed seeing them and watching them play with "Moogums" (phonetic spelling). Yes, Brandon decided that Audrey's official nickname would be "Moog" and any derivative thereof. No one knows why, but it's stuck. Poor Audrey is going to be called that until she's at least 18.

Of course, Brandon also decided that I would be "Aunt Moe" instead of "Aunt Ashlee." Moe is a childhood nickname that my family had for me (since my parents had three kids they tried to nickname us after the 3 stooges. Of course, only my name stuck). 

With less than a week left at home, there's still people I want to go visit and things that I need to do. Hopefully I'll be able to get it all done though! 

I have to admit, I'm looking forward to going back to Phoenix. I heard it's nice and warm there, whereas it's cold and rainy here!