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Steel and Composite Structures
  Volume 47, Number 3, May10 2023 , pages 355-363
DOI: https://doi.org/10.12989/scs.2023.47.3.355
 


Size-dependent strain rate sensitivity in structural steel investigated using continuous stiffness measurement nanoindentation
Ngoc-Vinh Nguyen, Chao Chang and Seung-Eock Kim

 
Abstract
    The main purpose of this study is to characterize the size-dependent strain rate sensitivity in structural steel using the continue stiffness measurement (CSM) indentation. A series of experiments, such as CSM indentation and optical microscope examination, has been performed at the room temperature at different rate conditions. The results indicated that indentation hardness, strain rate, and flow stress showed size-dependent behavior. The dependency of indentation hardness, strain rate, and flow stress on the indentation size was attributed to the transition of the dislocation nucleation rate and the dislocation behaviors during the indentation process. Since both hardness and strain rate showed the size-dependent behavior, SRS tended to depend on the indentation depth. The results indicated that the SRS was quite high over 2.0 at the indentation depth of 240 nm and quickly dropping to 0.08, finally around 0.046 at large indents. The SRS values at large indentations strongly agree with the general range reported for several types of low-carbon steel in the literature (Chatfield and Rote 1974, Nguyen et al. 2018b, Luecke et al. 2005). The results from the present study can be used in both static and dynamic analyses of structures as well as to assess and understand the deformation mechanism and the stress-state of material underneath the indenter tip during the process of the indentation testing.
 
Key Words
    dislocation; microstructure; nanoindentation; size effect; strain rate sensitivity
 
Address
Ngoc-Vinh Nguyen:1)Department of Civil and Environmental Engineering, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul 05006, South Korea
2)Department. of Civil Engineering, VNU Vietnam Japan University, My Dinh 129140, Tu Liem, Hanoi, Vietnam

Chao Chang:Department of Mechanics, School of Applied Science, Taiyuan University of Science and Technology, Taiyuan 030024, China

Seung-Eock Kim:Department of Civil and Environmental Engineering, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul 05006, South Korea
 

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