Experimental stress analysis of model of emergency forebody release device used in deep diving research submarines Alvin, Sea Cliff and Turtle

Abstract

Tests were conducted on a full-scale model of the emergency forebody release used in the deep-diving submarines ALVIN, SEA CLIFF and TURTLE. The model was machined from metal to the same dimensional tolerances as the prototype. Resistance strain gages, attached to the model, permitted measurement of forces on component parts of the device. Of primary concern was the bending stress which might be set up in the release operating shaft when the submarine is submerged in an inclined position. Tests were arranged to simulate three possible conditions of loading of the release device at a 30 degree vehicle list angle: case (1) righting moment of inclined forebody resisted by release components only; case (2) righting moment resisted by release with assistance from lower guides; and (3) righting moment resisted by couple set up by release and rubber support ring. Test results show that shaft bending stresses (for ALVIN) are high (200,000 psi) for the case (1) condition, lower (400,000 - 90,000 psi) for case (2) and essentially zero for case (3). The conclusion is that the present forebody release design is adequate for all submarine attitudes encountered in normal operation, provided the vehicle has been assembled so that contact between sphere and rubber ring is assured at all times.