Research Papers

Sensitive Material Behavior: Theoretical Model and Experiment for Compression Collapse of Gold Particles at Submicron Scale

[+] Author and Article Information
J. Q. Hu, Y. N. Cui

Applied Mechanics Laboratory,
School of Aerospace,
Tsinghua University,
Beijing 100084, China

Z. L. Liu

Applied Mechanics Laboratory,
School of Aerospace,
Tsinghua University,
Beijing 100084, China
e-mail: liuzhanli@tsinghua.edu.cn

Z. J. Wang, Z. W. Shan

Center for Advancing Materials Performance
from the Nanoscale (CAMP-Nano)
& Hysitron Applied
Research Center in China (HARCC),
State Key Laboratory for
Mechanical Behavior of Materials,
Xi'an Jiaotong University,
Xi'an 710049, China

Z. Zhuang

Applied Mechanics Laboratory,
School of Aerospace,
Tsinghua University,
Beijing 100084, China
e-mail: zhuangz@tsinghua.edu.cn

1Corresponding authors.

Contributed by the Applied Mechanics Division of ASME for publication in the JOURNAL OF APPLIED MECHANICS. Manuscript received May 14, 2014; final manuscript received June 23, 2014; accepted manuscript posted June 27, 2014; published online July 3, 2014. Editor: Yonggang Huang.

J. Appl. Mech 81(9), 091007 (Jul 03, 2014) (9 pages) Paper No: JAM-14-1214; doi: 10.1115/1.4027916 History: Received May 14, 2014; Revised June 23, 2014; Accepted June 27, 2014

Recent in situ TEM experiments observed that single crystalline gold particles with diameter ranging from 300 to 700 nm suddenly collapse, accompanying numerous dislocations escaping from the free surface during a flat punch pushing toward the particle. This collapse is catastrophic for the microdevices in service. In this work, we numerically and theoretically analyze the collapse mechanisms of this kind of “sensitive material.” First, by carrying out molecular dynamics (MD) simulations and finite element (FEM) analysis, we conclude that the strong strain burst in the collapse is derived from the robust emissions of plentiful pile-up dislocations in a particular area. Then, on the basis of numerical analyses, a theoretical model based on the virtual work principle is developed to predict the load–displacement curve during the indentation and reveal the energy dissipation and transformation before the particle collapse. Furthermore, a micromechanics-based dislocation pile-up model is established to quantitatively interpret the mechanism of particle collapse. Based on these studies, we propose the dislocation avalanche at the microscale depends not only on the peak stress but also on the stress gradients. The research is helpful for the design of reliable microdevices.

Copyright © 2014 by ASME
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Fig. 1

Process design for compression in situ experiment of gold particle in TEM [28]: (a) silicon wedge substrate; (b) a thin SiO2 layer is deposited; (c) thin Au film is deposited on the surface of the thin SiO2 layer; and (d) Au particles are formed after high-temperature annealing and for in situ TEM compression test

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Fig. 2

(a) Compressive force versus displacement of Au particle with diameter 300 nm; (b) TEM images during the burst process; and (c)–(f) experiment data and TEM images for particles with diameter 400 nm and 500 nm, respectively. Experimental data from Wang et al. [28].

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Fig. 3

(a) Compressive force versus displacement results of two simulations and experiment in 500 nm diameter particle; (b) Mises stress distribution in 500 nm diameter particle for ideally elastic–plastic model

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Fig. 4

(a) MD model of gold hemisphere particle compression; (b) dislocation structures under different compressive displacement and radius ratio, blue atoms with CSD > 7 while red atoms with CSD from 3 to 7

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Fig. 5

(a) Shear stress distribution along the radius in a section plane of the hemisphere; (b) two regions divided by dislocation densities

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Fig. 6

The theoretical load–displacement curve is compared with the experiment data and FEM result of the particle with diameter 500 nm

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Fig. 7

Three distinct energy forms versus displacement from theoretical model

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Fig. 8

(a) Two coordinate systems in a gold hemisphere. (b) Local resolved shear stress distribution along O1A.

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Fig. 9

(a) Linear stress distribution along a slip direction. (b) Plot of the normalized dislocation distribution as a function of location.

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Fig. 10

Stress distribution along the slip direction under different compressive displacement in sample with diameter 500 nm

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Fig. 11

Configuration of dislocations on a slip plane and the emission process at critical state at the collapse point




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