Optimum pressure vessel design based on fracture mechanics and reliability criteria

Spacecra€t s t ructural systems and subsystems a r e subjected to a number of qualification tes ts in which the proof loads a r e chosen a t some level above the simulated loads expected during the space mission. f racture as prime failure mechanism, and alluwing for time effects due to cyclic and sustained loadings, this paper t rea ts an optimization method in which the statist ical variability of loads and mater ia l properties a r e taken into account, and in which the proof load level i s used as an additional design variable. function while the total expected cost due to coupon testing for mater ia l characterization, due to failure during proof testing, and due to mission degradation i s a constraint. Numerical results indicate that for a given expected cost constraint , substantial weight savings and improvements of reliability can be realiz-ed by proof testing. Assuming In the optimization process, the s t ructural weight i s the objective vi JPL Technical Memorandum 33-470