SOLDERLESS WRAPPED CONNECTIONS 



PART II 



559 



Fig. 1 — Photograph of photooLastic modol and solderless wrapped connection. 



nique using photoelastic bakelite. Fig. 1 shows one of the photoelastic 

 models as compared with the metal solderless wrapped connection that 

 it simulates. While the ratios of the wire diameter to the terminal di- 

 mensions are different in the model from those in the connection, consid- 

 erable information can be obtained about strains in the terminals and 

 wires from the photoelastic model. 



The wrapping gun described in the previous paper puts a tension on 

 the wire. To simulate the tension, the photoelastic model is placed in a 

 chuck, one end of the wire is anchored to the chuck and an appropriate 

 weight is applied to the other end of the wire. The specimen is then 

 rotated by the chuck and a definite number of turns of copper wire 

 are wound around the specimen. The extra wire is then clipped off and 

 it is found that the wire tightly adheres to the terminal in the manner 

 of a metal solderless wrapped connection. The specimen is then polished 

 on the two ends up to the end wires and is put into the polariscope of a 

 photoelastic analyzer. For obtaining the isochromatic lines, i.e., the 

 lines occurring when the ordinary and extraordinary rays differ in path 

 length by a half wavelength or some multiple of a half wavelength, 

 the elements of the polariscope, as shown by Fig. 2, contain a quarter- 

 wave plate before and after the specimen. These have the effect of 

 making the plane wave from the polarizer circularly polarized and elimi- 

 nate the isoclinic lines which mark the directions of the slow and fast 

 axes of the material. Fig. 3 shows the isochromatic lines for a square 



