Residual stress measured in a layered ceramic

B. Ekbote, P. Kwon, M. B. Prime, “Micromechanics-based Design and Processing of Efficient Meso-scale Heat Exchanger,” 21st Annual Technical Conference of American Society for Composites, Sept. 17-20, 2006, Dearborn , MI. preprint (pdf) (LA-UR-06-5711)  

3-Layer Ceramic Specimen: 3-Layered disk Alumina about 0.59 mm thick 50/50 Zirconia/Alumina about 0.84 mm thick Zirconia about 0.94 mm thick About 19 mm diameter Tested two specimens	Cross-section of sample
Cut slot using grinding wheel: 1.07 mm thick diamond wheel 153 mm diameter Spinning at 3600 RPM 1 µm removed each pass of the wheel while bathed in coolant Strain readings taken at depth increments of 25 µm Strain gauge is mounted opposite the cut
Strain Data First Test: The first specimen was cut from the Zirconia side. Data was taken only to a depth of 26% of the specimen thickness, 0.635-mm, because the clamp failed and the specimen cracked
Strain Data Second Test : Clamping was improved, The second specimen was cut from the Alumina side to about 89% of the specimen thickness.
Finite Element Model for Coefficients : 3D finite element model used to calculate coefficients necessary for data reduction Color coded by hoop stress, discontinuities in stress are evident at layer interfaces
Stresses: Saw tooth profile typical of cooled, layered materials Different stress in each layer depending on thermal expansion coefficient Superimpose bending to restore moment equilibrium (this is what causes specimen curvature) These results are similar to those from elastic-only cooling of –1200 °C (± 30%)