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ADDITIONAL TECHNICAL PAPERS

Periodic Antiplane Cracks in Graded Coatings Under Static or Transient Loading

[+] Author and Article Information
B. L. Wang, Y.-W. Mai

Centre for Advanced Materials Technology (CAMT), School of Aerospace, Mechanical and Mechatronic Engineering J07, The University of Sydney, Sydney NSW 2006, Australia

J. Appl. Mech 73(1), 134-142 (Mar 08, 2005) (9 pages) doi:10.1115/1.2043190 History: Received September 17, 2004; Revised March 08, 2005

A periodic array of cracks in a functionally graded coating bonded to a homogeneous substrate is considered. The medium is subjected to transient or static mechanical loads. The problem is formulated in terms of a singular integral equation with the crack face displacement as the unknown variable. In addition to the time-varied stresses and stress intensity factors for various parameters of the problem, the effect of periodic cracking on the relaxation of the transient stress on the coating surface is discussed. Also included is the influence of the material gradient (material nonhomogeneity) on the crack tip intensity factors and stresses. Solutions for a single graded layer and a graded coating bonded to an infinite substrate are given.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

Grahic Jump Location
Figure 1

Periodic array of cracks in a graded coating bonded to a semi-infinite homogeneous substrate; h is the coating thickness; crack tips are located at y=b and y=d. 2c is the crack spacing. If b is larger than zero the cracks are embedded in the strip. For edge cracks, b equals zero.

Grahic Jump Location
Figure 2

Normalized transient stress intensity factor for surface cracks in a graded layer; k0=τ0πd, t0=hρ0∕μ0, μ(h)∕μ(0)=1∕3, b=0, d=0.25h

Grahic Jump Location
Figure 3

Same as Fig. 2; μ(h)∕μ(0)=1

Grahic Jump Location
Figure 4

Same as Fig. 2; μ(h)∕μ(0)=3

Grahic Jump Location
Figure 5

Normalized peak and steady values of the stress intensity factor for surface cracks in a graded layer; k0=τ0πd, b=0, d=0.25h

Grahic Jump Location
Figure 6

Normalized transient stress σ at the point A: (x,y)=(c,0) in a periodically cracked graded layer; t0=hρ0∕μ0, μ(h)∕μ(0)=1∕3, b=0, d=0.25h

Grahic Jump Location
Figure 7

Same as Fig. 6; μ(h)∕μ(0)=1

Grahic Jump Location
Figure 8

Same as Fig. 6; μ(h)∕μ(0)=3

Grahic Jump Location
Figure 9

Normalized peak values of the stress σxz at the point A: (x,y)=(c,0) in a periodically cracked graded layer

Grahic Jump Location
Figure 10

Normalized steady values of the stress σxz at the point A: (x,y)=(c,0) in a periodically cracked graded layer

Grahic Jump Location
Figure 11

Normalized transient stress intensity factor for periodic cracks in a coating/substrate system; k0=τ0πh, t0=hρ0∕μ0, μ(h)∕μ(0)=1, b=0, d=h

Grahic Jump Location
Figure 12

Normalized transient stress at the point A: (x,y)=(c,0) in a coating/substrate system; t0=hρ0∕μ0, μ(h)∕μ(0)=1, b=0, d=h

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