New cases of propagation of singularities along characteristic boundaries for model problems of shell theory

We continue a previous work [1] on propagation of singularities for model p roblems of thin shell theory in the parabolic and hyperbolic cases. The sin gularities along the characteristic boundaries are considered using extensi ons of the solutions out of the domain, adapted to either free or fixed bou ndaries. The corresponding transport equations are given except for the cas e of a characteristic fixed boundary for a hyperbolic shell, where the phen omenon is non local, but depends on the whole domain. (C) 2001 Academie des sciences/Editions scientifiques et medicales Elsevier SAS.