ABSTRACT
By trying to increase the luminosity or the life expectancy of an incandescent lamp, an
idea consists of a series of successive rolling up of the tungsten filament. This gives
geometrical configurations of filaments named simple, twin, or triple helical spring, etc.
In this paper, we will limit only to the case of the twin helical spring filament. Under the
combined effects of the high temperature and the stresses induced by its own weight,
the filament creeps by becoming plastically deformed in a permanent and a
continuously manner, until the rupture. The theoretical study of the behaviour of these
filaments needs the knowledge of internal loads distribution, deformations modes, and
their evolutions. The present work consists on an elastic structural analysis which must
be the first step. Since the objective is also to study the influence of the filament self
weight solicitation, the orientation with respect to gravitational direction should be taken
into account. Numerical results are obtained by finite element method. They showed a
negligible influence of the solicitations due to the variation of the temperature with
respect to those of the self weight, and a relative sensitivity to the position changes. For
the case of a vertical position, an analytical method has also been developed. Because
of some difficulties, the comparison between the numerical and analytical results could
not be carried out directly. However, the analytical approach proved to be qualitatively
useful for the analysis of numerical results.