Straight configurations of shearable nonlinearly elastic rods

In contact problems for elastic rods sometimes we have to look for a soluti on with some prescribed shape, in particular where some material curve has to be straight. While this question is a triviality for the Euler rod (or s implifications of it), the problem becomes much more subtle within a theory which describes planar deformations of nonlinearly elastic rods that can b end, stretch, and shear. For some selected material curve of the rod we ass ume that it is constrained to be straight by suitable external forces ortho gonal to that straight axis. It is shown that such configurations satisfy a second-order system of ordinary differential equations. In the case where this system is homogeneous a very rich structure can be observed by phase p lane analysis. Finally some applications for rods which are in contact with a straight obstacle are discussed, and interesting new effects can be deri ved.