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Time-Resolved Nano/Microscale Mechanical Characterization

The problems of extreme mechanics generally involve the complex constitutive responses of the material brought into play by the crossing and the interaction of multiple time scales or length scales. The material characterization under extreme loading conditions becomes complex because of the interaction between multi-field coupling, multiscale non-linearities, high temperature, high strain rate deformation, and their coupled influences. These challenges call for breakthroughs in experimental and measurement techniques and new approaches, criteria, and specific instruments.


Manufacturing defect-free materials for such structures also require information at different stages of manufacturing. The processes, operating conditions and control parameters, and post-processing (e.g., heat treatment) can all impact the end product. Additive manufacturing (AM) offers a unique method of microstructure control with high design freedom, enabling innovative, complex designs tailored for specific purposes. AM-based alloys and composites contain defects - such as inclusions, porosity, voids, cracks, un-melted particles, and lack of fusion. Porosity, grain size, and surface roughness correlate with laser or electron beam power and velocity. Inclusions such as oxides, nitrides, hydrides, carbides, or a combination, can serve as stress concentrators and the locus for catastrophic part failure. However, the Process-Structure-Property-Performance relationship is largely unknown for AM, highlighting the need for developing fundamental understanding through integrating experiments with modeling and simulation. 


Here, We focus on developing ultrafast spectroscopic experimental methods to characterize nano/micro-scale material properties, including elastic and inelastic behavior of materials, failure analysis, phase transformation, crushing, and dynamic spall under complex and extreme loading conditions. We use state-of-the-art in-situ mechanical characterization methods to develop new and innovative ultrafast spectroscopy, imaging, and tomography technique to measure real-time nano/microscale dynamic thermo-mechanical properties. Here the focus is on understanding the mechanisms involving the interaction of deformation, temperature state with the microstructural features, and their effect on overall thermo-mechanical behavior.
​The long-term goals of this proposed project are:

  • Develop affordable lab-based, nano/microscale Measurement, and Characterization Methods

  • Establish advanced test facilities for highly complex and extreme loading scenarios

  • Generate local coupled constitutive/failure/damage models based on the real-time response of fields of interest (as opposed to post-failure microscopy, sectioning, and imaging)

  1. Olokun, A. M., Li, B., Prakash, C., Men, Z., Dlott, Dana D., Tomar, V., 2019, Examination of Local Microscale-Microsecond Temperature Rise in HMX-HTPB Energetic Material Under Impact Loading, JOM, Vol. 71 (10), pages 3531-3535. (link)

  2. Prakash, C., Gunduz, I. E., and Tomar, V., 2019, Simulation-Guided Experimental Interface Shock Viscosity Measurement in an Energetic Material, Modelling and Simulation in Materials Science and Engineering, Vol. 27 (8), 085003. (link)

  3. Prakash, C., Gunduz, I. E., Oskay, C., and Tomar, V., 2018, Effect of interface chemistry and strain rate on particle-matrix delamination in an energetic material, Engineering Fracture Mechanics, Vol. 191, pages 46-64. (link)

  4. Prakash, C., Olokun, A. M., Gunduz, I. E., and Tomar, V., 2019, Intelligent Hypervelocity Impact Mechanical Raman Spectroscopy Measurements Based on Machine Learning, AIAA SciTech Forum.

  5. Zhang, Y., Prakash, C., and Tomar, V., 2018, Crack Tip Stress Measurement at High Temperature in IN-617 Using Nano-indentation and Nano-mechanical Raman Spectroscopy, Fracture, Fatigue, Failure and Damage Evolution, Volume 6, pages 51-56.(link)

  6. Olokun, A., Prakash, C., Gunduz, I. E., and Tomar, V., 2018, Interface Chemistry Dependent Mechanical Properties in Energetic Material using Nano-scale Impact Experiment, Dynamic Behavior of Materials, Volume 1, pages 147-152.(link)

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