Rate sensitivity and deformation mechanism of semi-crystalline polymers during instrumented indentation |
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| Authors: | Erqiang Liu Jianguo Wu Huaying Li Haitao Liu Guanghui Zhao Lingyu Kong Jinbao Lin Gesheng Xiao You Jia |
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| Institution: | 1. College of Applied Science, Taiyuan University of Science and Technology, Taiyuan, China;2. State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang, China;3. Heavy Machinery Engineering Research Center of the Ministry of Education, Taiyuan University of Science and Technology, Taiyuan, China;4. Institute of Applied Mechanics, College of Mechanical and Vehicle Engineering, Taiyuan University of Technology, Taiyuan, China |
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| Abstract: | Instrumented indentation tests using both constant loading rate (CLR) and continuous stiffness measurement (CSM) operation modes were performed to investigate the deformation mechanism and their sensitivity to the deformation rate in semi-crystalline polymers through the quantitative analysis of load-depth loading and unloading curves. The strain rate was constant during the CSM tests, while the strain rate decreased with the increasing of loading time in CLR tests. The mechanical response mechanism of the semi-crystalline polymers to these tests was very complicated because of the combined effects of strain-hardening in the crystal phase and strain-softening in the amorphous phase. Results show that the loading index m reflects the strain-hardening or strain-softening response during indentation. When m > 2, the mechanical response was due to the strain-hardening, and when m < 2, the response was due to strain-softening. A method based on the measured contact hardness was proposed to obtain the unloading stiffness, and the other mechanical parameters could then be determined according to the unloading stiffness. |
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| Keywords: | indentation loading index rate sensitivity strain rate unloading stiffness |
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