Computational & Experimental Materials Engineering Laboratory

Our former postdoc, Lucas Frérot, and Prof. El-Awady, along with collaborators from the Laboratoire de Tribologie et Dynamique des Systèmes at École Centrale de Lyon in France, have published a new article at ACS Nano. The work combines detailed atomistic simulations at the nanoscale, experiments, and macroscale theoretical modeling to show that the macroscopic friction response emerges from the nanoscale surface roughness and the molecular motion within the adsorbed lubricant monolayers (contact junctions). The work shows that the existence of surface roughness even at a nanoscale is enough to prevent the lubricant molecules from making contact over the whole surface, leaving the molecules on the edges of contact spots free to move. Over time, more molecules come in contact, resulting in aging.

The work is dedicated to the memory of our former colleague Prof. Mark Robbins who passed away in 2020.

Check the article out!

From Molecular to Multiasperity Contacts: How Roughness Bridges the Friction Scale Gap The tangential force required to observe slip across a whole frictional interface can increase over time under a constant load, due to any combination of creep, chemical, or structural changes of the interface. In macroscopic rate-and-state models, these frictional aging processes are lumped into an...

Better late than never!

Pictures from our group outing (the few who were in town then) in September 2022 in celebration of Dr. Markus Sudmanns' last week in office at JHU after a very successful 2.5 year postdoc in our lab! He has moved to become a Research Area Manager at RWTH Aachen University in Germany. Good luck Markus and looking forward to your future successes!

Prof. El-Awady joins a team of international scientists who published a new review paper in Nature Materials that highlights recent developments in bioinspired nanocomposites, and how engineers are using nature to design tougher, more sustainable materials. Check it out!

Hierarchically structured bioinspired nanocomposites - Nature Materials This Review discusses recent progress in bioinspired nanocomposite design, emphasizing the role of hierarchical structuring at distinct length scales to create multifunctional, lightweight and robust structural materials for diverse technological applications.

Check out our new paper in which we develop a new approach for tracking the three-dimensional (3D) surface displacements of a material undergoing in situ mechanical testing inside a scanning electron microscope (SEM). The paper is based on computer vision approaches to identify and track different features in the SEM images

Specifically, we estimate the out-of-plane intrusions/extrusions and in-plane motion of surface points from multiple views of the sample at the end of the experiment. Then, using reverse optical flow, propagate these displacements backwards in time using interim single view images. These measurements can be extended to map the 3D surface strain tensors. This approach offers an alternative to the commonly used digital image correlation (DIC) technique, which relies on tracking a speckle pattern applied to the material surface. DIC based on single views only produces in-plane two-dimensional (2D) measurements, whereas our approach enables reconstruction of the 3D surface morphology and is completely non-invasive (requires no pattern being applied to the material surface).

Three-dimensional surface displacement tracking for in-situ experiments: An alternative to digital image correlation (DIC) We develop an approach for tracking the three-dimensional (3D) surface displacements of a material undergoing in situ mechanical testing inside a scan…

Nothing beats an in-person conference where you meet old friends and make new friends. Where you are able to discuss new ideas and build on going collaborations! It was great being back at the TMS annual meeting and looking forward to more successful in-person meetings in the near future!

Prof. Jaafar El-Awady, Dr. Yejun Gu, Dylan Madisetti, and Mostafa Omar, presented at the 150th TMS annual meeting in Anaheim, CA last week.

Prof. El-Awady joins a number of collaborators in publishing a review article on microstructure-property linkages in the dynamic behaviors of magnesium alloys, which was a result of a long term collaboration funded through the Materials in Extreme Dynamic Environments (MEDE) Metals Collaborative Materials Research Group (CMRG). Check it out!

Sorry, we can’t find the page you are looking for — ScienceDirect Let’s see if we can help you out. You can perform a search at the top of this page, report a broken link to prevent other users from ending up here. Or use this opportunity to take a little break from work, reading interesting material below.

Our postdoctoral fellow Dr. Markus Sudmanns and Prof. El-Awady publish a new study in Acta Materialia on modeling dislocation plasticity in High Entropy Alloys. The study focuses on the effects of short range ordering on the evolution of plasticity in these new alloys. Check it out!

The El-Awady group on a beautiful and sunny Fall day at the Homewood campus!

Front row left to right: Junjie Yang, Juliette Mahaffey, Jing Luo, Bazah Alhooli
Back row left to right: Dylan Madisetti, Dr. Ali Rida, Dr. Chris Stiles (APL), Dr. Markus Sudmanns, Prof. Jaafar El-Awady, Mostafa Omar, Daniel Magnuson.

Available PhD position in Fall 2022 and postdoctoral fellow position in Winter 2022 at the Department of Mechanical Engineering at the Johns Hopkins University with focus on "Artificial Intelligence for Accelerated Materials Design in Hypersonic and Energy Applications". Expected qualifications: strong knowledge in machine learning and/or mechanics of materials. Additionally, the candidate should have a strong background in computer coding (e.g. Python, C, C++, etc.). Interested candidates should send questions and their updated CV listing their qualifications to Prof. El-Awady at [email protected]

In a collaboration with Prof. Somnath Ghosh's group at JHU we have published a new micro-mechanical investigation of the thermo-mechanical properties of micro-architectured tungsten coatings using both in situ micro-compression experiments inside a scanning electron microscope (SEM) as well as image-based crystal plasticity finite element method (CPFEM) simulations. These coatings have micro-patterned surfaces with a low-porosity microstructure, which gives them unique themral and sputtering resistance properties (e.g. distribute the heat flux more effectively, enhanced thermal fatigue resistance due to the relatively-free expansion and contraction of the coating during thermal cyclic loading, and overall sputtering rate due to ion bombardment of these coatings).

In our current study we show that these coatings exhibit a brittle-to-ductile transition in deformation mode. At temperatures below 573 K, catastrophic failure at high strength but low strains, which is characterized by intergranular fracture and buckling of individual columnar grains was observed and attributed to the high lattice friction and the intrinsic void/pores present along the grain boundaries. At higher temperatures, the lower lattice friction gives rise to enhanced plasticity at the tip of the pre-existing grain boundary defects and the material exhibits a continuous plastic flow with more homogeneous deformation. While the strength of the coating inevitably decreases with increasing temperature, the enhanced plastic deformation offers great defect tolerance capability that suppresses the structural instability observed at low temperatures.

Finally, the experimental and simulation observations suggest that the structural integrity of these coatings can be improved through either reducing the grain aspect ratio and/or improving the GB toughness. These generally can be tailored through changing the processing parameters during the chemical v***r deposition of these coatings.

Check out the paper!

Micro-mechanical investigation of the thermo-mechanical properties of micro-architectured tungsten coatings The thermo-mechanical response of micro-architectured tungsten coatings is characterized in the temperature range of 293 to 673 K using both in situ m…