2014 年 80 巻 814 号 p. TRANS0141
In this paper, a prediction method of the maximum principal strain of a core/shielding wire contained in a coaxial cable, which is related to the life-cycle of the wire, is proposed. If the central axis of a wire is assumed to be twisted around a virtual cylindrical surface when a coaxial cable is straight and a virtual toroidal surface when the cable is bent, the shape of the wire can be described by the first and the second fundamental form of their surfaces in the differential geometry. The potential energy of the wire, which is bent, twisted, expanded, and/or contracted, is also formulated based on the differential geometry. Friction of the wire against the virtual surface is modeled as a virtual spring in the circumferential direction of the surface and its elastic energy is included in the total potential energy of the wire. Then, the stable shape of the wire can be computed by minimizing its total potential energy under geometric constraints. After that, the maximum principal strain is estimated from the shape of the wire. As a result of simulation, it was founded that a core wire is broken by bending fatigue before the shielding wire is if they have the same radius and rigidity.
