Analysis of the deformation of a perforated sheet under thermal and tension load using finite element method

Two-dimensional and three-dimensional finite element methods have been used to analyze the deformation behavior of a shadow mask of perforated sheet due to thermal and tension load. The shadow mask inside the Braun tube of a TV set has numerous slits through which the electron beams are guided to land on the designed phosphor of red, green or blue. Its thermal deformation, therefore, causes mislanding of the electron beam and results in decolorization of the screen. For realistic finite element analysis, the effective thermal conductivity and the effective elastic modulus are calculated, and the shadow mask is modeled as a shell without slits. Next, transient thermal analysis of the shadow mask is performed, wherein thermal radiation is a major heat transfer mechanism. Analysis of the resulting thermal deformation follows, from which the mislanding of the electron beam is obtained. The present finite element scheme may be efficiently used for the thermal deformation design of a shadow mask and in developing prototypes of large screen flat TV.