Investigation of stresses during dynamic behavior of polymeric films used for Braille

Abstract

In recent years publications for the blind people using Braille writing began to be produced on polymeric films. This has the advantage with respect to previous technologies, because such publications have longer time period till the time when their quality degrades and they become unacceptable for use. Plotting isoclinics for bending vibrations of a polymeric film using photo-elastic coatings is analyzed. The numerical procedure is based on the technique of conjugate approximation with smoothing. Improved smoothing procedure for two dimensional Lagrange quadratic elements is proposed. Composite isoclinic patterns with isoclinics for various directions of the vector of polarization in a plane polariscope are obtained. A single Braille element of the polymeric film on the basis of the plane strain problem is investigated. Nodal stresses are calculated by using the procedure of conjugate approximation. Equivalent stresses are represented by intensity of the image. Special experimental setup was created. Three samples were investigated: the first two samples were made from transparent polymeric film with Braille elements, the third sample was made from transparent polymeric film with Braille elements formed by the method of thermal shaping. The level of stresses is estimated in the static status of the sample and after rotations by various angles. For precise estimation of the stress fields photo‑elastic images for a number of different values of the angle of rotation are required. Thus in this paper stresses in transparent polymeric films and Braille elements in them are investigated. The obtained results are used in the process of forming Braille elements in polymeric films.