TENSILE IMPACT ON RUBBER AND NYLON
QUARTERMASTER RESEARCH AND ENGINEERING COMMAND NATICK MA
Pagination or Media Count:
A method was sought for describing the response of visco-elastic materials to loading when the velocity of strain propagation in the material is the controlling factor. A machine is described that delivers a longitudinal impact at about 150 ftsec to a yarn or strip. The impact is photographed using a high-speed stroboscope and a moving mirror. Strain-time-position data are obtained from the picture. Results are given for the impact of a rubber strip. InANOTHER EXPERIMENTAL TECHNIQUE THE FORCE AT THE FIXED END OF A NYLON YARN DURING IMPACT IS MEASURED. Tentative high-speed stress-strain curves were deduced, for the rubber from the photograph and for the nylon from another series of tests in which the acceleration of a tail mass was measured. Assuming that these curves hold during the impact with no time dependency, the strain patterns were computed by a method of characteristics given by von Karman, OSRD No. 365, 1942 OSRD No. 496, 1950 J. Appl. Phys., 21987, 1950 and compared with the experimental results. The timing and strain levels of the measured pulses are well duplicated by the calculation. However, the calculated pulses have much steeper fronts than are observed. For both rubber and nylon, in order to describe the impact response it is necessary to include a creep function as well as a dynamic stress-strain curve.
- Elastomers and Rubber