Allie and Jessy

I would be remiss if I didn't mention our visitors from Brown University this summer. Allie and Jessy are undergraduates in the geosciences department who wanted to gain some lab experience. They worked on measuring wave speeds in partially molten ice samples. This involved lots of time in the cold room...

Working with Mike, they put together this special baby cryostat to maintain temperature around samples. Inside the cooled cylinder sat a sample of ice + ammonia and on either side of the sample were ultrasonic transducers.

They were very careful, took excellent notes, and calculated error bars. At the end of the summer they presented their (tiny) poster at an informal poster session at Lamont.

And they did such a nice job, that we will publishing their results in an upcoming special edition of Geosciences about Interiors of Icy Ocean Worlds. Stay tuned for that and for great things to come from these young researchers!

Daning says goodbye

Last year we had a visiting grad student in our lab. Daning Zhong was working on a modeling project and helping with friction experiments in the lab.

In September she had to return to China because her 1 year visit was up. At Ted's goading, we took a walk around campus for a photo shoot. 

It was really nice having her visit. She did a great job applying the Aharonov and Scholz constitutive model of friction to high homologous temperature ice friction. Stay tuned for a Zhong et al. publication coming soon!

Open House 2018

For this year's Open House, Rock Mechanics put together a new demo to try to convey the idea of strain in a sample. The first task involved getting our hands on some polarizing film.

Then Rob and Mike put together a special box to look at a sample of PMMA in polarized light. In the back is just an old computer monitor actually and that new film was placed in front. Here it is unstressed (you can see residual strain from fabrication).

Rotated to a different position.

And stressed.

Rock Mechanics at the GRC

We got the whole team together at this year's Gordon conference. What a great group!

We even had our newest member, Seth, who hasn't started yet.

Seth won the Lamont Postdoc Fellowship and will start this spring. He's going to be working on ice-till friction but will revamp and include all kinds of new gadgets and methods, like measuring acoustic emissions and using machine learning to compare lab micro-events to real ice stream events. We're super excited to have him joining us!

New grad student Kristina, who is working with Heather, also joined the conference and killed it at her poster session.

Although we're not supposed to take pictures, I snapped a super fast one of Genevieve during her opening slide. She was one of only a couple of students asked to give a talk at the conference. She did an amazing job!!

And if you've ever been to GRC, this last picture needs no introduction. The non-vegetarian amongst us all donned our little bibs and dug in. Over all another great GRC!

Regelation or Viscous Deformation?

This summer, in addition to five other interns, we also had four students through the Climate and Life program: Camille, Jeremy, Naomi, and Jennifer. They were looking at the difference between regelation (pressure melting and recrystallization) and viscous deformation, which could be mechanisms of flow at the base of glaciers under the right conditions. Mike built a frame to go with Rob's dead weight apparatus that the students assembled. They calculated the stress for each increment of weight to be added. 

They did a great job drawing the below schematic of the set up. The frame was used to apply a dead weight to the top of the ice, which was resting on top of spheres of various size and composition. The  hypothesis was that under some conditions regelation would dominate over viscous deformation and other conditions it would not. Since any melt formed would drop down below the balls due to gravity, we would be able to tell the difference. Also, in theory, regelation should be faster with spheres of higher thermal conductivity so we thought me might be able to tell the difference that way.

They printed up their motivations, methods, and results into a nice poster. Title was all their idea, and I love it!

And they did a great describing their project to the other interns and my colleagues at an informal poster session held on the last day.

With about a half hour left before the bus, they enjoyed some competitive stress concentration and particle interaction.

Also joining us in the lab this summer was Will, a local high school student. He worked on a pressure sensitive film project to quantify real area of contact changes of samples in the rig. After getting the method down on roughened teflon and PMMA, it was time to start working on ice.  Since he was looking at contact area change with time and normal stress (but zero velocity), we didn't need to use both pistons for his experiment. Working with Mike, they designed and built a special purpose cryostat with a wood frame and this green styrofoam for insulation.

The cryostat fit nicely into the apparatus, allowing it to be pre-chilled with circulating fluid and loaded with the prepared ice sample and forcing blocks. A small slot at the top allowed him to change the chilled pressure films in and out. 

With the horizontal hydraulic pistons, we applied 450 kPa normal stress at -2 degrees C and he measured the pressure on the films at 10 s, 100 s and 1000 s holds. The films were digitized and analyzed in ImageJ for %area. After lots of trouble shooting and trial and error to develop the protocol for this brand new method (for us anyway), his summer culminated in getting the below data set (Fig. b). It looks great! Well done, Will!

Summer 2018: cheese!

It's been a long while since we've posted. But with such a fun, busy summer, we had to share all our updates. Although we said goodbye to Tess and wished her success in her future adventures, we said hello to many new faces. Nine (9!!!!) summer interns joined the lab: 2 undergrads visiting us from Brown, and 7 high school interns. A lot of ice-related fun was had by all!

But before we can start working with ice, we have to learn about cheese. Rheology lab got the students learning about stress, strain, and how to run a creep experiment. The three teams were assembled.

 All cheese was measured and stresses calculated.

And the experiments started. They make sure to capture the immediate elastic response by measuring the height of the cheese as soon as they apply the weight. And then they continue taking a measurement every three minutes or so to capture the transient and steady state. One student holds the timer, one measures with the calipers and calls out the height, and one records it in excel.

This year we tried to support the weights to prevent tipping. It worked well in most cases...but not all.