PAST RESEARCH PROJECTS

Dynamic Scratch Resistance of Nano-engineered Concrete for Sustainable Applications in Railway and Civil Construction

Crumbed rubber concrete represents an alternative to recycle tire rubber waste, thereby alleviating pressure to landfill sites. In this project, crumbed-rubber concrete is considered to extend the lifetime of railway ties via reduced wear. Our goal is to understand the tribological behavior at the microscopic scale as a function of intrinsic and extrinsic parameters. The knowledge gained will boost the design of high-performance railroad materials.

Funding Source: Birmingham-Illinois BRIDGE.

Publications:

Ange-Therese Akono, Jiaxin Chen, S. Kaewunruen, Friction and Fracture Characteristics of Engineered Crumb-Rubber Concrete at Microscopic Lengthscale, Journal of Construction and Building Materials, Vol. 30, pp. 735-745, (2018).

Multi-scale and Multi-Physics Modeling of Na-PS Geopolymer Cement Composites

Inorganic polysialates are novel lightweight ceramic-like materials that are twice stronger than cement with a carbon footprint five times smaller. Our research goal is to accelerate the discovery of enhanced-performance polysialate composites by simulating various alumino-silicate systems at extreme scales using a deterministic approach. The end goal is a set of optimized design parameters in a vast and complicated state space along with a first-principles understanding of inorganic polysialate composites.

Funding Source: National Center for Supercomputing Applications, Blue Waters.

Ductile-to-Brittle Transition In Scratch Testing

Scratch testing is a standard rock mechanics testing method with relevance in rock excavation, oilwell drilling, and unconventional resources extraction applications. By application of Bazant’s size effect law, we show that the ductile-to-brittle transition is governed by the depth at the microscopic scale and by the blade with and width-to-depth ratio at the macroscopic scale.

Publications:

Scratch Test as a Fracture Process

The scratch test consists in pushing a hard probe across the surface of a softer material. Dating pack to the pre-Hellenic area and the Mohs scale, the scratch test is one of the oldest mechanics-of-materials tests; however, the underlying mechanics are not fully understood. The research objective is to formulate a fracture mechanics model to correlate the forces and depth measurements during scratch testing to intrinsic material fracture characteristics.

Funding Source: MIT Energy Material Initiative, Schlumberger, Shell, Total

Publications

  • Ange-Therese Akono, Franz-Josef Ulm, Scratch test model for the determination of fracture toughness, Engineering Fracture Mechanics, Vol. 78, pp. 334-342, (2011)
  • Ange-Therese Akono, Franz-Josef Ulm, An improved technique for characterizing the fracture toughness via scratch test experiments, Wear, Vol. 313, pp. 117-124, (2014).
  • Ange-Therese Akono, Franz-Josef Ulm, Rate-dependent toughness in soft materials via microscopic scratch testing. In A. Bajaj, P. Zavattieri, M. Koslowski, & T. Siegmund (Eds.). Proceedings of the Society of Engineering Science 51st Annual Technical Meeting, October 1-3, 2014, West Lafayette: Purdue University Libraries Scholarly Publishing Services, (2014).
  • Ange-Therese Akono, Franz-Josef Ulm, Fracture scaling relations of axisymmetric shape, Journal of the Mechanics and Physics of Solids, Vol. 60, pages 379-390, (2012).
  • Akono, Ange-Therese; Reis, Pedro Miguel; Randall, Nicholas Xavier; Ulm, Franz-Josef, Scratch test as a fracture process: from soft to hard materials, American Physical Society, APS March Meeting 2012 Proceedings, February 27-March 2, (2012).
  • Ange-Therese Akono, Nicholas X. Randall, Franz-Josef Ulm, Experimental determination of the fracture toughness via micro scratch tests: application to polymers, ceramics and metals, Journal of Materials Research, Vol. 27, pp. 485-493, (2012).
  • Ange-Therese Akono, Pedro Miguel Reis and Franz-Josef Ulm, Scratching as a Fracture Process: From Butter to Steel, Physical Review Letters, Vol.106, pp. 204302, (2011)