Construction and evaluation of membrane analogy apparatus for torsion analysis

This research presents the design, construction, and evaluation of a membrane analogy apparatus for the torsion analysis of non-circular sections (prismatic bars). The purpose of this project was to construct and demonstrate the use of the apparatus. The degree of error obtained by the apparatus was determined by performing experiments with the following three sections: 1. Square (3" x 3") 2. Equilateral Triangle (4" side) 3. Rectangle (2" x 3") The order of error was 1 to 5 percent. Thin Plastic (Polyethylene) material (0.0015" thickness) and a rubber membrane (0.009" thickness) were used to carry out the membrane analogy experiment. Contours and graphs are presented for each section mentioned above. The apparatus is easy to construct and is inexpensive. Experiments can be performed with the apparatus without much difficulty. The percentage error due to the apparatus can be reduced to a great extent by a few alterations in the design. A large amount of error in results is due to the membrane material which is not an ideal membrane.