Asymptotic analysis of an elastic rod with rounded ends

We derive a one-dimensional model for an elastic shuttle, that is, a thin rod with rounded ends and small fixed terminals, by means of an asymptotic procedure of dimension reduction. In the model, deformation of the shuttle is described by a system of ordinary differential equations with variable degenerating coefficients, and the number of the required boundary conditions at the end points of the one-dimensional image of the rod depends on the roundness exponent m is an element of(0,1). Error estimates are obtained in the case m is an element of(0,1/4) by using an anisotropic weighted Korn inequality, which was derived in an earlier paper by the authors. We also briefly discuss boundary layer effects, which can be neglected in the case m is an element of(0,1/4) but play a crucial role in the formulation of the limit problem for m >= 1/4.Peer reviewe

Spectra of Two-Dimensional Models for Thin Plates with Sharp Edges

We investigate the spectrum of the two-dimensional model for a thin plate with a sharp edge. The model yields an elliptic $3\times3$ Agmon–Douglis–Nirenberg system on a planar domain with coefficients degenerating at the boundary. We prove that in the case of a degeneration rate $\alpha<2$, the spectrum is discrete, but, for $\alpha\geq2$, there appears a nontrivial essential spectrum. A first result for the degenerating scalar fourth order plate equation is due to Mikhlin. We also study the positive definiteness of the quadratic energy form and the necessity to impose stable boundary conditions. These results differ from the ones that Mikhlin published.Delft Institute of Applied MathematicsElectrical Engineering, Mathematics and Computer Scienc