16 research outputs found
Thermomechanical surface instability at the origin of surface fissure patterns on heated circular MDF samples
When a flat sample of medium density fibreboard (MDF) is exposed to radiant
heat in an inert atmosphere, primary crack patterns suddenly start to appear
over the entire surface before pyrolysis and any charring occurs. Contrary to
common belief that crack formation is due to drying and shrinkage, it was
demonstrated for square samples that this results from thermomechanical
instability.
In the present paper, new experimental data are presented for circular
samples of the same MDF material. The sample was exposed to radiant heating at
20 or 50 kW/m2, and completely different crack patterns with independent
Eigenmodes were observed at the two heat fluxes. We show that the two patterns
can be reproduced with a full 3-D thermomechanical surface instability model of
a hot layer adhered to an elastic colder foundation in an axisymmetric domain.
Analytical and numerical solutions of a simplified 2-D formulation of the same
problem provide excellent qualitative agreement between observed and calculated
patterns.
Previous data for square samples together with the results reported in the
present paper for circular samples confirm the validity of the model for
qualitative predictions, and indicate that further refinements can be made to
improve its quantitative predictive capability.Comment: 9 pages, 13 figures. New title and abstract, added experimental and
simulation details and figures, conclusions unchanged. Matches the version
published in Fire And Material
Microscopic images of dorsal surface of <i>C</i>. <i>albicans</i>-infected tongues 48 hours after AM-CAPPJ exposure.
<p>(1) HE-stained; (2) PAS-stained; (A) non-treated group; (B) plasma-treated; (C) Nystatin-treated; (D) Scores (median values and ranges) attributed to the inflammatory alterations and tissue invasion 48 hours after exposure to AM-CAPPJ.</p
Microscopic images of dorsal surface of <i>C</i>. <i>albicans</i>-infected tongues 24 hours after AM-CAPPJ exposure.
<p>(1) HE-stained; (2) PAS-stained; (A) candidiasis induced and non-treated group; (B) plasma jet-treated; (C) nystatin-treated; (D) Scores (median values and ranges) attributed to the inflammatory alterations (column 1) and tissue invasion (column 2) 24 hours after exposure to AM-CAPPJ.</p
Number of viable cells in <i>C</i>. <i>albicans</i> ATCC 18804 biofilms (median and range) exposed or not to AM-CAPPJ (n = 9).
<p><b>* p<0.05</b>.</p
Typical current and voltage waveforms for 2.0 slm of He flow and 1.5 cm distance to the target.
<p>Typical current and voltage waveforms for 2.0 slm of He flow and 1.5 cm distance to the target.</p
Counts of colony forming units in miceâ tongues 24 hours after the treatment with nystatin or AM-CAPPJ.
<p>Counts of colony forming units in miceâ tongues 24 hours after the treatment with nystatin or AM-CAPPJ.</p