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Research Papers

Optical Microscopy-Aided Indentation Tests

[+] Author and Article Information
D. A. Doman1

Department of Mechanical Engineering, Dalhousie University, 1360 Barrington Street, Halifax (Nova Scotia) B3J 1ZJ, Canadadarrel.doman@dal.ca

R. Bauer

Department of Mechanical Engineering, Dalhousie University, 1360 Barrington Street, Halifax (Nova Scotia) B3J 1ZJ, Canadarobert.bauer@dal.ca

A. Warkentin

Department of Mechanical Engineering, Dalhousie University, 1360 Barrington Street, Halifax (Nova Scotia) B3J 1ZJ, Canadaandrew.warkentin@dal.ca

1

Corresponding author.

J. Eng. Mater. Technol 130(1), 011008 (Jan 17, 2008) (6 pages) doi:10.1115/1.2806252 History: Received October 13, 2006; Revised August 13, 2007; Published January 17, 2008

The contact characteristics of ceramic-metallic interactions are of critical importance in the design of high-speed ceramic rolling contact bearings. This type of interaction is not described well by traditional indentation tests since small displacements and barely discernable indentations are encountered. In this work, an optical microscopy system is described that is used to measure small indenter displacements accurately. Images of the indenter are taken throughout the test and processed using sophisticated edge detection algorithms to accurately determine the position of the center of the indenter. Thus, the indenter displacements on the order of 1μm can be measured independent of any structural flexibility present in the test apparatus. Experimental indentation tests using an alumina indenter mounted on a stainless steel post were performed and processed with the optical system. The results were compared to existing analytical models for fully elastic and elastoplastic cases as well as a finite element model developed using a Johnson–Cook plasticity material model. The comparison shows that the analytical models do not predict the experimental results well, whereas the finite element model agrees very well. Subsequent analysis of the finite element model shows that the size of the contact zone and pressure distributions, both very important in the design of bearings, can be more accurately described than the traditional analytical treatments.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of indentation regimes

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Figure 2

Illustration of displacement error due to deformation of the stylus

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Figure 3

Schematic of indentation setup

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Figure 4

Image of (a) the backlit indenter and (b) edge detection algorithm

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Figure 5

No load measured versus commanded displacement

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Figure 6

Three-dimensional quarter model of the spherical indentation test

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Figure 7

Comparison of analytical and FE models to experimental indentation test data

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Figure 8

Plot of effective stress distribution within the specimen at 5.2μm displacement

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Figure 9

Contact zone pressure distribution plot of finite element and analytical solutions

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