Micro/ nano-scale evaluation
Research materials: Additive manufactured Inconel 718 and 316L SS, NiMoW and NiCoCr alloys, Shape memory alloys (SMAs), Single element metals and aluminum alloys, etc.
It has been observed that the mechanical properties of materials are very different from those of their bulk counterparts. While the microstructural effects of each individual grains are often averaged in bulk samples, such effects are greatly amplified as the characteristic dimension of the materials becomes comparable with its grain size. However, characterization of materials at small-scale has been challenging due to the inherent difficulties associated with handling and gripping of the samples, reproducibility of samples and results, and to accurately evaluate its responses.
Therefore, we have utilized various techniques in fabrication of the micro/ nano-scale samples, and developed various testing techniques to measure the intrinsic mechanical properties exhibited by the micro/ nano-scale samples. The experimental results were then analyzed based on our knowledge of mechanics and materials.
Experiments utilizing the micro-tensile tester:
We utilized a custom-built micro-tensile tester which has a stroke of up to 600 μm with a displacement resolution of 10 nm and a load resolution 9.7 μN. Freestanding thin films of different materials were sputter-deposited and fabricated through micro-electromechanical system (MEMS) processes into the shape of a rectangular/ dogbone samples with thicknesses of a few microns down to a few hundred nanometers. The films were evaluated under a variety of mechanical programs which includes the standard uniaxial tensile tests, fatigue tests, creep tests, repeated stress relaxation tests, etc.
Experiments utilizing the nanoindenter:
The nanoindenter is used as a load cell and actuator simultaneously to conduct both tensile and compression tests on micro/ nano-scale samples fabricated through a series of MEMS processes, femto-second laser and focused ion beam (FIB) milling. The material can be precisely fabricated into desirable shapes to conduct micropillar compression tests, micro-tensile and torsion tests, microcantilever beam deflection test, membrane deflection tests, nanoindentation tests, and combinatorial studies at both room and elevated temperatures.
It has been observed that the mechanical properties of materials are very different from those of their bulk counterparts. While the microstructural effects of each individual grains are often averaged in bulk samples, such effects are greatly amplified as the characteristic dimension of the materials becomes comparable with its grain size. However, characterization of materials at small-scale has been challenging due to the inherent difficulties associated with handling and gripping of the samples, reproducibility of samples and results, and to accurately evaluate its responses.
Therefore, we have utilized various techniques in fabrication of the micro/ nano-scale samples, and developed various testing techniques to measure the intrinsic mechanical properties exhibited by the micro/ nano-scale samples. The experimental results were then analyzed based on our knowledge of mechanics and materials.
Experiments utilizing the micro-tensile tester:
We utilized a custom-built micro-tensile tester which has a stroke of up to 600 μm with a displacement resolution of 10 nm and a load resolution 9.7 μN. Freestanding thin films of different materials were sputter-deposited and fabricated through micro-electromechanical system (MEMS) processes into the shape of a rectangular/ dogbone samples with thicknesses of a few microns down to a few hundred nanometers. The films were evaluated under a variety of mechanical programs which includes the standard uniaxial tensile tests, fatigue tests, creep tests, repeated stress relaxation tests, etc.
Experiments utilizing the nanoindenter:
The nanoindenter is used as a load cell and actuator simultaneously to conduct both tensile and compression tests on micro/ nano-scale samples fabricated through a series of MEMS processes, femto-second laser and focused ion beam (FIB) milling. The material can be precisely fabricated into desirable shapes to conduct micropillar compression tests, micro-tensile and torsion tests, microcantilever beam deflection test, membrane deflection tests, nanoindentation tests, and combinatorial studies at both room and elevated temperatures.
Read more in our publications:
[1] Lee, Z. F., Ryu, H., Kim, J. Y., Kim, H., Choi, J. H., Oh, I., Sim, G. D. (2024). High-throughput membrane deflection characterization of shape memory alloy thin films. Materials Science and Engineering: A, 892, 146028.
[2] Oh, I., Kim, H., Son, H., Nam, S., Choi, H., & Sim, G. D. (2023). Combinatorial experiments for discovering Al-C thin films with high strength and ductility. International Journal of Plasticity, 161, 103515.
[3] Kim, H., Choi, J. H., Park, Y., Choi, S., & Sim, G. D. (2023). Mechanical characterization of thin films via constant strain rate membrane deflection experiments. Journal of the Mechanics and Physics of Solids, 173, 105209.
[4] Choi, J. H., Kim, H., Kim, J. Y., Lim, K. H., Lee, B. C., & Sim, G. D. (2022). Micro-cantilever bending tests for understanding size effect in gradient elasticity. Materials & Design, 214, 110398.
[5] Sim, G. D., Xie, K. Y., Hemker, K. J., & El-Awady, J. A. (2019). Effect of temperature on the transition in deformation modes in Mg single crystals. Acta Materialia, 178, 241-248.
[1] Lee, Z. F., Ryu, H., Kim, J. Y., Kim, H., Choi, J. H., Oh, I., Sim, G. D. (2024). High-throughput membrane deflection characterization of shape memory alloy thin films. Materials Science and Engineering: A, 892, 146028.
[2] Oh, I., Kim, H., Son, H., Nam, S., Choi, H., & Sim, G. D. (2023). Combinatorial experiments for discovering Al-C thin films with high strength and ductility. International Journal of Plasticity, 161, 103515.
[3] Kim, H., Choi, J. H., Park, Y., Choi, S., & Sim, G. D. (2023). Mechanical characterization of thin films via constant strain rate membrane deflection experiments. Journal of the Mechanics and Physics of Solids, 173, 105209.
[4] Choi, J. H., Kim, H., Kim, J. Y., Lim, K. H., Lee, B. C., & Sim, G. D. (2022). Micro-cantilever bending tests for understanding size effect in gradient elasticity. Materials & Design, 214, 110398.
[5] Sim, G. D., Xie, K. Y., Hemker, K. J., & El-Awady, J. A. (2019). Effect of temperature on the transition in deformation modes in Mg single crystals. Acta Materialia, 178, 241-248.
Updated on 2024.04.19
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