RESEARCH PAPERS: Armor and Personal Protection

Experimental Measure of Parameters: The Johnson–Cook Material Model of Extruded Mg–Gd–Y Series Alloy

[+] Author and Article Information
Fan Yafu, Chen Jie, Ji Wei

Yantai Branch, No. 52 Institute of China Ordnance Industry Group, Yantai 264003, Shandong, China

Wang Qu-dong

Light Alloy Net Forming National Engineering Research Center, Shanghai Jiaotong University, Shanghai 200030, China

Ning Jun-sheng

Department of Physics, Yantai University, Yantai 264005, Shandong, China

J. Appl. Mech 77(5), 051902 (Jun 30, 2010) (5 pages) doi:10.1115/1.4001291 History: Received July 31, 2009; Revised December 12, 2009; Published June 30, 2010; Online June 30, 2010

This paper introduces a method to determine the material constants for Johnson–Cook model of an as-extruded Mg–Gd–Y series alloy by quasistatic tests on Instron 1251 and Hopkinson bar experiment at room and elevated temperatures. The results indicate that the thermal softening exponent of the current magnesium alloy is as high as 3.05, which is obviously higher than that of most metal materials, such as steel and tungsten. High thermal softening exponent usually means high energy absorption efficiency, and the comparison of the dynamic stress-strain curves between ZK60 and Mg–Gd–Y series alloy indeed indicates that the energy absorption efficiency of the Mg–Gd–Y series alloy is higher than that of ZK60. Additionally, high energy absorption efficiency makes the Mg–Gd–Y series alloy exhibit more excellent antipenetration performance than that of 7A52 aluminum alloy at equal areal density condition.

Copyright © 2010 by American Society of Mechanical Engineers
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Figure 1

The quasistatic compressive stress-strain curve of the Mg–Gd–Y series alloy tested by Instron 1251 (a) and the fitting curve of the selected data points (b)

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Figure 2

Experimental points at a constant strain and different strain rates and their fitting curves shown in Cartesian coordinate (a) and in semilogarithmic coordinate (b)

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Figure 3

The fitting curve of the thermal softening exponent, m=3.05

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Figure 4

Yield stress versus temperature relationship of the experimental points and two kinds of fitting curves from formulas 8,9, respectively

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Figure 5

Stress-strain curves of two kinds of magnesium alloy Mg–Gd–Y series alloy and ZK60

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Figure 6

Damage patterns of 7A52 aluminum alloy penetrated by a steel ball at 872 m/s (a) and the current Mg–Gd–Y series alloy penetrated by a steel ball at 923 m/s (b)



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