Multiscale Mechanics of Materials Lab
Welcome to the home page of the research lab of Prof. Aaron Stebner at Colorado School of Mines. We also have an "unofficial" website, a facebook page, instragram, and a twitter feed that are maintained by our group members. If you would like to download software that our group develops, check out our github.
Our group studies advanced mechanics -- such as high-rate deformation, twinning, phase transformation, and plasticity -- of advanced solid materials, such as lightweight alloys, shape memory alloys, low symmetry alloys, and functional ceramics. Most of our projects focus on understanding the connections between physical phenomena spanning multiple length scales. We are especially known for our work using in-situ diffraction experiments to develop and verify material models. We also have a lot of interest in engineering applications of advanced materials, and work to bring our scientific research to the broader engineering community in the form of improved design tools and methodologies and the development of new courses and workshops.
Our research spans multiple disciplines of science and engineering. We accept students through the Mechanical Engineering, Materials Science, and Metallurgy and Materials Engineering graduate programs.
Below is a movie of a X-ray diffraction dataset we collected at the newly revamped F2 beamline at the Cornell High Energy Synchrotron Source (movie made by Harshad Paranjape). The sample was a cubic NiTi (nearly) single crystal. In our new experiments, we are using two "High Energy Diffraction Microscopy" techniques. On the left, we used a detector placed far away from the sample (~1m). This configuration provides very high resolution for strain analysis. We then rotate the sample, and collect a 2D diffraction image every 0.1 to 0.25 degrees of rotation. As the sample rotates, the grain satisfys Bragg's law for different diffraction vectors, causing the diffraction spots to process around the detector. From these series of processions, we can reconstruct information in 3D. In the movie of the far-field measurement, we let the diffraction spots accummulate for visual clarity of this process. On the right side of the movie, we place a detector very close to the sample (~ 5mm). This allows us to fully image the microstruture, like a doctor would image your bones. As the sample is rotated, the grain(s) of the sample are imaged, and again the sequence of 2D images taken as a function of rotation may be used to reconstruct the grains and interfaces of the microstructure in 3D.
We also perform similar measurements at the 1-ID line of the Advanced Photon Source. In addition, we make high energy X-ray tomography measurements on this beam line, in collaboration with Peter Kenesei. Below are some recent results characterizing particles and voids in a magnesium AZ31b sample that was processed using Equal Angle Channel Extrusion (ECAE). The purple are precipitates, the dark red are voids/cracks, and the silver is the alloy matrix. The white line is 50 microns in size.