Abstract

Residual stresses due to thermal expansion mismatch for refractory particles on high purity silica glass were studied. Finite element analysis was used to determine the stresses around ZrO₂, Cr₃O₄, SiC and graphite particles in contact with a SiO₂ substrate. Results were obtained for both fully and half submerged particles. Results were compared to existing analytical models for fully submerged particles where applicable. Effects of particle aspect ratio for elongated particles were studied. ZrO₂, Cr₃O₄ and SiC were modeled as isotropic materials. All exhibited tensile radial stresses, with ZrO₂ displaying the highest stress levels. The stresses at the SiO₂ surface reached a maximum a short distance from the particle/matrix interface. Peak radial stress increased with increasing particle aspect ratio. Maximum tensile stress for elongated particles was located at the tip of the particle, corresponding to fracture origins noted for these particles. Graphite particles were modeled as anisotropic structures and the stresses were determined for different crystalline orientations. Unlike the other refractories, the maximum tensile stress for a graphite particle in one of its possible orientations was located at the edge of the particle. This corresponds to fracture origins noted on silica glass with graphite particle surface flaws. The stress field results are discussed in a fracture mechanics framework, and the effect of residual stress on material reliability is presented.

© 1997 Optical Society of America