Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 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.

2
The categories of this paper are: math
16
The categories of this paper are: stat
23
The categories of this paper are: solv-int
8
The categories of this paper are: hep-ex
10
The categories of this paper are: q-bio
15
The categories of this paper are: nucl-ex
32
The categories of this paper are: atom-ph
5
The categories of this paper are: gr-qc
21
The categories of this paper are: adap-org
14
The categories of this paper are: math-ph
9
The categories of this paper are: nlin
31
The categories of this paper are: ao-sci
33
The categories of this paper are: plasm-ph
26
The categories of this paper are: bayes-an
1
The categories of this paper are: cs
30
The categories of this paper are: q-alg