Journal of Dental Research, Vol 68, 1223-1230, Copyright © 1989 by International & American Associations for Dental Research Online Journals
Effect of visco-elastic behavior on stress development in a metal-ceramic system
P. H. Dehoff and K. J. Anusavice
Department of Mechanical Engineering and Engineering Science, University of North Carolina, Charlotte 28223.
We developed an analytical model to calculate transient stress and gap
displacement during cooling of a porcelainized semicircular arch with a
gapped diametral segment. Constant cooling rates were assumed after the
specimens were slowly cooled (with power terminated to the furnace) from
the porcelain firing temperature. The analytical model incorporates linear
visco-elasticity and structural relaxation effects. We calculated transient
and residual gap displacements and stresses for a semicircular arch
specimen (composed of an experimental opaque porcelain and a Ni-Cr-Be
alloy) for six thickness ratios at a cooling rate of 3 degrees C/min.
Residual gap displacements were measured for metal-porcelain arch specimens
of six thickness ratios. Compared with measured values, calculations based
on the visco-elastic theory overestimated gap closure for porcelain/metal
thickness ratios below 1.5, and underestimated gap closure at thickness
ratios above 1.5.
