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RESEARCH PAPERS

# Influence of Microstructure in Partial-Slip Fretting Contacts Based Upon Two-Dimensional Crystal Plasticity Simulations

[+] Author and Article Information
C.-H. Goh, D. L. McDowell

The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405

R. W. Neu1

The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405rick.neu@me.gatech.edu

1

Corresponding author.

J. Tribol 128(4), 735-744 (Jun 12, 2006) (10 pages) doi:10.1115/1.2345414 History: Received March 14, 2006; Revised June 12, 2006

## Abstract

The role of microstructure is quite significant in fretting because the scale of plastic strain localization near the surface is on the order of key microstructure features. A dual-phase Ti-6Al-4V alloy that tends to be susceptible to fretting is considered as a model material. Fretting is simulated using a two-dimensional finite element analysis. A crystal plasticity theory with a two-dimensional planar triple slip idealization is employed to represent the hexagonal close packed structure of the $α$ phase of Ti. Modifications of the slip system strengths enable multiple phases to be considered. In this study, the effects of grain orientation distribution, grain size and geometry, as well as the phase distribution and their arrangement, are considered in simulations. Implications of the results are discussed.

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## Figures

Figure 1

Schematic of the 2D planar triple slip model for representing the primary α and the secondary (α+β) phases. Slip can most easily occur along the soft slip systems that are parallel to the third slip system (dashed lines).

Figure 2

Finite element meshes for (a) the ideal fretting model and (b) the component fretting model. P(=W∕L) and Q are the normal and tangential forces per unit length (L), respectively.

Figure 3

Schematics of the 2D planar triple slip model for various grain orientation angles: (a) θ=5deg, (b) θ=15deg, (c) θ=25deg, and (d) θ=45deg. Here, x, y represent the local coordinate system and X, Y represent the global coordinate system, respectively.

Figure 4

Distributions of ε¯p in the subsurface field of a single crystal for five grain orientation angles (θ) after the completion of three cycles with indenter in place (ideal fretting model with μ=1.5, P∕Py=1.0, and Q∕Py=0.3)

Figure 5

Plastic strain maps developed within a single crystal over the third fretting cycle for various orientation angles (θ) (ideal fretting model with μ=1.5, P∕Py=1.0, Q∕Py=0.3, and a=215μm)

Figure 6

Effects of texture on the subsurface distributions of the effective ratchetting plastic strain increment (Δεratch,effp) near the trailing edge of the contact for a contrived set of textures for μ=1.5: (a) θ=0±5deg, (b) θ=15±5deg, (c) θ=30±5deg, (d) θ=30±30deg, and (e) fully random θ (component fretting model: Rσ=0.1, P∕Py=0.28, a=514μm)

Figure 7

Distributions of ε¯p near the contact after the completion of three cycles based on crystal plasticity simulations for various sizes of square grains for the case (ideal fretting model with μ=1.5, P∕Py=1.0, and Q∕Py=0.3)

Figure 8

Schematics representing microstructures under the contact area consisting of various grain sizes and two grain shapes (ideal fretting model): (a) SQ20 I (square, 20μm), (b) SQ20 II (square, 20μm), (c) SQ40 I (square, 40μm), (d) SQ40 II (square, 40μm), (e) HEX20 (hexagonal, 20μm), and (f) HEX40 (hexagonal, 40μm).

Figure 9

Distributions of ε¯p near the contact after the completion of three cycles for various microstructures with different grain sizes and grains for the case (ideal fretting model with μ=1.5, P∕Py=1.0, and Q∕Py=0.3)

Figure 10

Schematics representing mixed models of microstructures under the contact area consisting of various grain sizes and two grain shapes (ideal fretting model): (a) SQMIX I (square grains), (b) SQMIX II (square grains), (c) HEXMIX I (hexagonal grains), and (d) HEXMIX II (hexagonal grains).

Figure 11

Four contrived phase distributions (light—primary α, dark—implicit α+β)

Figure 12

Distributions of ε¯p in the subsurface field after the completion of three cycles for four sets of nonrandom phase distributions combined with the mixed models of microstructures consisting of different grain sizes of hexagonal grains for the case of the ideal fretting model with μ=1.5, P∕Py=1.0, and Q∕Py=0.3

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