(mini-) Earthquake!

Ladies and gentlemen, the Biax is now fully operational! We can now make earthquakes in our lab!

The main cause for the delay was this pesky guy below. The chassis is the component that handles the flow of all that data coming from the rig (10 strain gauges, 2 load cells, an LVDT measuring displacement, and anywhere from 1 to 4 transducers measuring the seismic signal) and going to the computer (for immediate feedback) and to the RAID (for short-term storage). Although the data all come in as basic voltage signals, the rate of data streaming for the different components varies, making it difficult, for some reason, to get the optimal combination of cards and cords for the chassis. While I was away, Heather worked with the manufacturer to get us the right combination. The card on the far left gets the signal from the BNC, the card protruding gets the high speed signal from the transducers, and the wide middle card is a built-in RAID. 

It took a little while to get here, but we now are able to load up the sample and, by monitoring the voltage on the LVDT, watch it creep along until we hear the "Crack" and "Pop" of little earthquakes. Success! Now we get to start systematically varying things to be able to predict the onset of the earthquakes and, in particular, try to understand the transitional period that is believed to occur between the creeping and the earthquake. 

soldering up a storm

Now, in order for the confining pressure and pore fluid pressure intensifiers to respond and "stop on a dime", if you will, the hydraulics have to have something to push against. So we needed to rig up pipes that will carry compressed air from the air compressor in the room next door. In addition, there needs to be a reservoir of air on the ready in case a large volume is needed. Thus the big yellow buoy-looking thing on the left. So, armed with about 50 feet of 3/4" copper tubing, tube cutters, miscellaneous tees and elbows, solder, and a blowtorch (!!), we got to work. 

Often times that meant one of us jumping up on top of the rig itself and soldering into the existing pipes in the wall/ceiling. This was my first time soldering pipes, so I can't say I was very meticulous at the job. I road home on the subway just filthy, completely covered with a thin layer of hydraulic fluid and probably bits of wall insulation and flux. But I have to say, it was pretty darn fun!
Check out our handiwork below.

"Triax this is Houston, do you read?"

Ted and Heather got a lot of work done on the Triaxial apparatus while I was away. For one thing, they got the pressure vessel all lined up and then set up these two blue mini-versions of the vessel, called intensifiers, that control the confining pressure and the pore fluid pressure (so, one controls the pressure outside the sample and the other, inside). We'll use kerosene for the confining liquid. There's also that row of seven things sitting atop the mini-vessels. I don't know what they do yet but I'm excited to find out.

In addition, there are now big hoses going to and from the vessel and intensifiers and a burly hydraulic fluid pump. The pump is so powerful and loud that it sits in its own insulated doghouse outside the lab, otherwise it would drive us all crazy.

And one very exciting development is that they rewired the old control panel that will be used to communicate with the Triax. Since the rig will get up to very high pressures during experiments, you really don't want to be standing next to it while it is running. Rather, you want to be safely around the corner at this groovy old school station, complete with analogue Heise pressure gauges (on the blue wall panel) and all the digital readings you require.

Research Trip: Edinburgh

For the last 30 days I was in Edinburgh on a research exchange visit. It was an absolutely wonderful time to be visiting Scotland. The days were brisk, but not that cold and somehow I managed to avoid most of the rain. 

The visit was funded by a branch of the European Science Foundation, called MicroDICE. Their purpose is to promote the exchange of science and techniques between Universities and countries, especially if it is concerning the microstructures of Ice. 

I was visiting Jane Blackford, who is in the Materials Science department of the University of Edinburgh.  Here's Jane with the fields of outer Edinburgh below her. Whenever we weren't in the lab, we tried to sneak out to the surrounding hills for a hike or to the local climbing gym for a route or two.

Our research goal was to measure the "dihedral angle" of sulfuric acid and ice, that is, the wetting angle that a liquid acid solution makes in the corners of ice grains, which is determined by the surface energies. Sulfuric acid has been found in polar ice packs and is thought to exist on icy moons in the outer solar system. The reason for measuring the angle is because if the angle is very large (>60 degrees), sulfuric acid would be stuck and confined to the corners of grains, but if the angle is small (<60 degrees) it could travel through interconnected veins of liquid. Traveling liquid acid could really influence the physical properties of ice, so it is an important characteristic to measure. We sprayed a solution of ~5%acid into liquid nitrogen so that it would flash freeze into droplets that we collected and put into these little aluminum containers (right). Then we let the samples "cook" at various temperatures that were below the freezing temperature of ice yet above the freezing temperature for the liquid acid solution. We let them sit like that for about a week and then we quenched them in liquid nitrogen to capture that microstructure.  Then it was off to the Biology department to visit Chris Jeffree and his scanning electron microscope that is specially equipped to handle frozen samples (below).

Chris was an absolute wizard with the SEM and managed to take hundreds of images of dihedral angles. I am now in the process of measuring all those angles, first by hand and then electronically. Publication coming soon!

working on the triax

Now that the biaxial apparatus is ready to run (we're just hammering out some bugs with our National Instrument gear), our attention has turned to the triaxial rig. It applies a confining pressure using either gas or a solid medium. The pressure inside the vessel can really build and if it blows, it could be deadly, so this behemoth sits in its own room in the back of the lab. Our first task was to rotate the steel cylindrical vessel 90 degrees so that it can connect to new gas tubing and then check the integrity and alignment of the vessel. The vessel and attached top plate together weigh almost 1000 lbs, so taking things apart is no small feat. Ted rigged up a pulley system to a beam in the ceiling and we carefully lowered the two parts, which immediately began to swing out on us.

Eventually we got the parts under control, rotated, and back up in place. Next week while I am away, Ted and Heather will make sure the vessel is perfectly centered. They will use a tool that precisely measures the location of the inside wall of the vessel with a needle. Using the machine hydraulics they will raise the needle up the inner length of the vessel. If there is any tilt to the vessel wall, the tool will indicate that and they can shove little wedges of wood or thin steel around the top plate to center it.

a library grows at lamont

Today we cleared some counter space and pulled out all the old dusty reference books out of boxes. Need to know anything about metals, alloys, pressure vessels, analog to digital conversion?....we've got it covered! And nice bookends, don't you think? 

a gaggle of strain gauges

Today we moved another big step closer to running an experiment by connecting strain gauges to the sample. Ted affixed various kinds of gauges along the business edge of the sample in order to measure strain that is parallel, perpendicular, and at 45 degrees to the frictional surface. The gauges are then soldered to a rainbow of wires that lead to that little green breakout box. Coming from the box are wired connectors that will plug into individual signal conditioners.

Each of 10 signal conditioners below are used to zero-out and amplify the response from the gauges and will then send a voltage output to the computer.

We were getting a little interference from the rainbow of wires and the output connections in the back were hard to reach, so Ted reconfigured it as below, with the strain wires now hiding safely inside the silver mesh tube. Although it looks a bit hectic this way, it works really well.

And "how on earth do we plug all those things into the computer?" you may ask. Well they first get connected to this BNC box. Then the BNC box is connected to a thing called a chassis (more on that later) that is, in turn, connected to a card in the back of the PC.

a clean, well-lighted place to talk about rocks

Big addition to the lab yesterday: the facilities folks found us a table! I don't know where they found it, but it's new-ish, relatively clean, and can be wheeled around the lab easily. Today I came in to find a cute little plant in the middle of it. Now we have a place to sit around and plan the next step. Since our housecleaning is generally finished, it is time to start rehabilitating the testing machinery. First on the list is that rig in the center back. It is called a "biaxial" friction apparatus because it applies stress on the top and on one side, but there is no confining pressure.

a little calibrating

Today was a very productive day. While Ted worked on the strain gauges (they each have to be glued onto the side of the sample and then soldered to wires), I calibrated the LVDT. The box on the left provides an excitation voltage to the LVDT, which is a cylinder with a hollow in the middle. Using that little Schaevitz tool in the foreground, I systematically inserted a core piece into the hollow of the LVDT a half millimeter at a time. With each increment, the LVDT puts out a different voltage, which is measured by the box on the right. I make a plot of distance versus voltage that tells us the calibration factor for our experiments. 

Meanwhile, Heather checked the gauges and put a protective coating on the load cells. We use homemade load cells here, which is unusual I think. We will put one on the side of the sample to measure the horizontal load and one on the top to measure the vertical.

a little outreach

This weekend I volunteered at the Maker Faire in Queens. The event is a big collection of folks interested in science, engineering, do-it-yourself home projects, crafts...the list goes on and on.

Next to the home-still biodiesel guy was Dr. Buckner from Science for Citizens talking about dinosaur teeth and a mastodon fossil that was found here in New York.

Science-Cheerleaders were there, along with Gen-Space (a DIY science lab in Brooklyn), to help kids and adults do some hands-on science experiments.

The project was to extract the DNA from strawberries using everyday household items. Here's a primer on how you can do it at your home!  That's me in the lab coat below.

I also brought some of the rock and mineral samples from the lab for kids to play with.

off-site adventure

This week Heather and I attended a conference for the Southern California Earthquake Center (SCEC), held annually in Palm Springs. I got a gorgeous view of the Grand Canyon during the flight over.

Heather and her colleague presented a poster about earthquakes in the US "triggered" by the 9.0 Tohoku-Oki earthquake.

In between talks and posters, I was able to sneak away to our hotel room to catch up on my journal reading and enjoy the unusually mild Palm Springs weather.

meet the new barista!

Over there behind the chair, next to the presses is a refrigerator. You'll just have to trust me on this.

Today we installed a little coffee station on top of that fridge. Since the campus is far far away from any Starbucks (the horror!!), we need to supply our own. Come 3:00 I am always in serious need of some java. Now we're set. Yay!

Resistors 101

So what do you know about resistors? I thought I knew a lot. I knew that they were the little nubby balls connected to two wires and soldered to a circuit board. I knew that they were the squiggly lines on a circuit diagram and are used to control the current in the system. What I didn't know was just how many different kinds (shapes, sizes, range of values) of these things were available. Now I know this all too well.

Today's project was to consolidate the lab's various collections of resistors. Specifically, we were taking the ones in these green metal drawers and putting them with those of matching resistance in these little plastic drawers.

 

Which often meant reading the teeny tiny numbers on each individual resistor in the drawer. I learned that not only do we have resistors for every value from 10 ohms to 10 megaohms, we also have multiple brands and sizes for each.

These three different resistors offer the same resistance but have different size beads (RN55, RN60, and RN65, in case you are curious).

Success!

baby steps

My first very small contribution to the lab was to clear off a section of the countertop and designate it the paperwork station. That way we have some clean space to sit and plan, make lists, etc. Seems like a very small change, but oh so important for my mental state.

An Introduction to the lab

So here is our rock mechanics lab. The thing is, the old lab used to be really big and full of lots of stuff. Lots and lots of stuff. They even had some stuff stored over in another building. Before they hired my boss, the University split this old lab into two smaller labs. With her "start up" fund, my boss had the floors and walls redone and new shelves and counter space installed.

When it was time to move back all the old equipment--including the stuff from that other building--there just wasn't enough room. So it was all piled up everywhere. I wish I took a picture of the way it looked a month ago when I first arrived. We have already done a lot of work finding new homes for things. But these pictures will give you the general idea.

 Above is the view from the front. This doesn't even look that bad. The blue and green metal cabinets behind the tool box and the mini drawers above the yellow box on the left are recent installations.

 Here is a view from the back of the lab. That lathe in the foreground is actually up on rollers and may or may not be fully operational. 

 Along the desktop. That section down at the end will eventually be a soldering station. Currently it is just known as the area where I throw the soldering irons (5 so far) when I find them in various parts of the lab.

 This is one of the back rooms, where the high pressure rig is kept. This is what the whole lab looked like one month ago.

And here is the other small back room. That big gray block in the middle is concrete that is connected to the building and the underlying foundation. It will be a great place to do creep experiments or other tests in which you want to reduce any outside vibrations. Right now we just use this as the room where we put the junkiest of the junk that we don't want to deal with any time soon.