Fatigue, creep and fracture evaluation
Research materials: Single element metals, NiMoW alloy, Shape memory alloys (SMAs), Additive manufactured Inconel 718 and 316L SS, etc.
Mechanical structures and systems we encounter in our daily life are all subjected to repeated cycles of stress loading, whether it be the overhead bridge that our vehicles drives over every day, or the smartphones that we carelessly flip to close before inserting into our pockets. Hence, it is not persuasive at all to claim that a material is "good" just because it demonstrated high strength or elasticity under monotonic loading, deeming it to be applicable in various structural applications.
The study of fatigue deals with understanding the changes towards material behaviors when subjected to consistent loading cycles before they eventually loses their functionality and fail. Although as consumers we often hope that whatever products we purchased must be of perfection and worthy of our money spent, materials used to manufacture the parts and components will often contains a certain degree of defects. Under repeated loadings, defects like minor voids present in the material itself will act as stress concentration sites and promote the initiation of crack growth. After some point, these unnoticable defects would have reach a critcal size where now its presence could not be neglected. The study of fracture then deals with the understanding of how these defects would eventually lead to failure of the component, and to prevent this catastrophic failure by early prediction and maintenance of the system.
Therefore, it is of our equal importance to not just investigate the mechanical performance of a material under monotonic loading, but also to investigate their time-dependent behaviors and under repeated loading cycles. We are capable to perform fatigue tests, fracture tests, creep tests and repeated stress relaxation tests for samples of bulk, meso , and micro/ nano-scales with the custom-built mechanical testers in our lab.
Mechanical structures and systems we encounter in our daily life are all subjected to repeated cycles of stress loading, whether it be the overhead bridge that our vehicles drives over every day, or the smartphones that we carelessly flip to close before inserting into our pockets. Hence, it is not persuasive at all to claim that a material is "good" just because it demonstrated high strength or elasticity under monotonic loading, deeming it to be applicable in various structural applications.
The study of fatigue deals with understanding the changes towards material behaviors when subjected to consistent loading cycles before they eventually loses their functionality and fail. Although as consumers we often hope that whatever products we purchased must be of perfection and worthy of our money spent, materials used to manufacture the parts and components will often contains a certain degree of defects. Under repeated loadings, defects like minor voids present in the material itself will act as stress concentration sites and promote the initiation of crack growth. After some point, these unnoticable defects would have reach a critcal size where now its presence could not be neglected. The study of fracture then deals with the understanding of how these defects would eventually lead to failure of the component, and to prevent this catastrophic failure by early prediction and maintenance of the system.
Therefore, it is of our equal importance to not just investigate the mechanical performance of a material under monotonic loading, but also to investigate their time-dependent behaviors and under repeated loading cycles. We are capable to perform fatigue tests, fracture tests, creep tests and repeated stress relaxation tests for samples of bulk, meso , and micro/ nano-scales with the custom-built mechanical testers in our lab.
Read more in our publications:
[1] Lavenstein, S., Crawford, B., Sim, G. D., Shade, P. A., Woodward, C., & El-Awady, J. A. (2018). High frequency in situ fatigue response of Ni-base superalloy René-N5 microcrystals. Acta Materialia, 144, 154-163.
[2] Lee, Y. S., Sim, G. D., Bae, J. S., Kim, J. Y., & Lee, S. B. (2017). Tensile and fatigue behavior of polymer supported silver thin films at elevated temperatures. Materials Letters, 193, 81-84.
[3] Sim, G. D., Lee, Y. S., Lee, S. B., & Vlassak, J. J. (2013). Effects of stretching and cycling on the fatigue behavior of polymer-supported Ag thin films. Materials Science and Engineering: A, 575, 86-93.
[4] Sim, G. D., Hwangbo, Y., Kim, H. H., Lee, S. B., & Vlassak, J. J. (2012). Fatigue of polymer-supported Ag thin films. Scripta Materialia, 66(11), 915-918.
[1] Lavenstein, S., Crawford, B., Sim, G. D., Shade, P. A., Woodward, C., & El-Awady, J. A. (2018). High frequency in situ fatigue response of Ni-base superalloy René-N5 microcrystals. Acta Materialia, 144, 154-163.
[2] Lee, Y. S., Sim, G. D., Bae, J. S., Kim, J. Y., & Lee, S. B. (2017). Tensile and fatigue behavior of polymer supported silver thin films at elevated temperatures. Materials Letters, 193, 81-84.
[3] Sim, G. D., Lee, Y. S., Lee, S. B., & Vlassak, J. J. (2013). Effects of stretching and cycling on the fatigue behavior of polymer-supported Ag thin films. Materials Science and Engineering: A, 575, 86-93.
[4] Sim, G. D., Hwangbo, Y., Kim, H. H., Lee, S. B., & Vlassak, J. J. (2012). Fatigue of polymer-supported Ag thin films. Scripta Materialia, 66(11), 915-918.
Updated on 2024.05.14
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