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Research Papers: Contact Mechanics

Material Property Identification and Sensitivity Analysis Using Micro-Indentation

[+] Author and Article Information
Long Ge

Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL 32611ccdel@ufl.edu

Nam H. Kim1

Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL 32611nkim@ufl.edu

Gerald R. Bourne

Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL 32611grb@ufl.edu

W. Gregory Sawyer

Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL 32611wgsawyer@ufl.edu

1

Corresponding author.

J. Tribol 131(3), 031402 (Jun 01, 2009) (7 pages) doi:10.1115/1.3142902 History: Received August 13, 2008; Revised April 26, 2009; Published June 01, 2009

Mechanical properties of materials in small-scale applications, such as thin coatings, are often different from those of bulk materials due to the difference in the manufacturing process. Indentation has been a convenient tool to study the mechanical properties in such applications. In this paper, a numerical technique is proposed that can identify the mechanical properties using optimization and evaluate the robustness of identified material properties using sensitivity analysis. First, two response surfaces are constructed for loading and unloading curves from the indentation experiment of a gold film on the silicon substrate. Unessential coefficients of the response surface are then removed based on the test statistics. Unlike the traditional methods of identification, the tip geometry of the indenter is included because its uncertainty significantly affects the results. In order to validate the accuracy and stability of the method, the sensitivity of the identified material properties with respect to each coefficient is analyzed. It turns out that the plastic hardening parameter is the most sensitive to the experimental data. In addition, all material parameters are sensitive to the coefficients of higher-order bases. However, their effects are diminished because the magnitudes of these coefficients are small.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Elastoplastic material behaviors of aluminum alloys

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Figure 2

Finite element model of axisymmetric indentation with a conical tip

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Figure 3

Indentation response of aluminum alloys by finite element analysis and experiment (18)

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Figure 4

Equivalent stress contour plot for AL 7075 after unloading (unit: MPa)

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Figure 5

Effective plastic strain near the indenter tip

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Figure 6

The tip geometry of the indenter from SEM and its approximations with a sphere

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Figure 7

Indentation force versus indentation depth with initial estimation of material properties

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Figure 8

Force distribution in the loading and unloading steps

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Figure 9

Force and depth comparisons of experimental, initial design, and optimized results

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Figure 10

Comparison of the force-displacement curve with the identified material properties (with and without varying tip radius)

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