Velocity Fields in a Sphere Subjected to Large Deformations

This paper deals with the experimental determination of velocities of displacement in a sphere subjected to a diametral load. The maximum applied load reduced the diameter of this sphere by 27 percent. The velocities are given for each step of loading and were determined from a model made of polyurethane rubber that behaves linearly. The velocities were obtained by superposition of photographs of 500 lpi gratings embedded in the meridian plane of the sphere. The evaluation was made both point-by-point and by photographic recording of the whole field of isotachics. The errors produced as a consequence of the motion of points are evaluated and criteria are given on the best method to use and on whether corrections are necessary or not.