On art,science, beauty and the experimentalist

Comments are made on the concepts of beauty and art, and their relationship with physical phenomena. Experimental physicists have means at their disposal to produce objects of art just as the painter uses oil and the sculptor uses marble to produce objects of art. Several new photographs of “log-art” or artistic science are shown.     

An error associated with graphical parametric operations

In grid and moiré analyses, patterns developed in a deformed body are sometimes superposed to obtain the difference of their parameters, as when it is desired to obtain velocities by superimposing two isothetic patterns. In this operation, an inherent difficulty develops because, as a consequence of the deformation, not all points can be matched. An error follows which is analyzed here. Means to avoid or to compute the error are suggested.     

Optimization of geometric discontinuities in stress fields

The ideal boundary of a discontinuity is defined as that boundary along which there is no stress concentration. Photoelastically an isochromatic coincides with the ideal boundary. This property is used to develop experimentally ideal boundaries for some cases of technological interest. The concept of ‘coefficient of efficiency’ is introduced to evaluate the degree of optimization. The procedure to idealize boundaries is illustrated for the two cases of the circular tube and of the perforated rectangular plate, with prescribed functional restraints and a particular criterion for failure. An ideal design of the inside boundary of the tube is developed which decreases its maximum stress by 25 percent, at the time it also decreases its weight by 10 percent. The efficiency coefficient is increased from 0.59 to 0.95. Tests with a brittle material show an increase in strength of 20 percent. An ideal design of the boundary of the hole in the plate reduces the maximum stresses by 26 percent and increases the coefficient of efficiency from 0.54 to 0.90.