Strength of the ALVIN hulls
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Results are presented of pressure tests, measurements and analyses of the strength of the three pressure hulls constructed for the deep submergence vehicle ALVIN. Comparison of stress distribution as measured in various tests and predicted theoretically is made. Failure of the hull can occur by buckling or by yielding over an appreciable fraction of shell thickness or by yielding at a stress concentration. A DTMB analysis predicts collapse of the three hulls No. 1, 2, and 3 at 7040, 7160, and 6720 psi respectively. No. 1 hull has been tested to 4400 psi. From strain measurements, isolated yielding at the inside surface of hull No. 2 (presently in ALVIN) will occur at a pressure of 5800 psi. However, yielding through the entire section would not occur until near the predicted collapse pressure. The maximum Mises equivalent stress at the test pressure of 3300 psi is 62,000 psi. The comparable material yield strength 125,000 psi is used with hull No. 2. the strength of the plexiglas viewing ports, the electrical lead-throughs and the hull release mechanism are referenced but not discussed.