AEROSTRUCTURAL SAFETY FACTOR CRITERIA USING DETERMINISTIC RELIABILITY

The primary function of most metallic structures is to sustain operational loads with no detrimental deformation. The current practice of specifying a universal ultimate safety factor, or reliability, biases the operation margin by the selection of material. By expressing the deterministic safety factor in probabilistic tolerance limits, the included three safety design factors are specified independently by loads, materials, and stress criteria. The minimum limit of the stress safety design factor was determined to be the ultimate-to-yield stress ratio. This ratio was combined with estimated modeling and complexity uncertainty factors to redefine the conventional safety factor. The metallic structural safety with the modified conventional safety factor and the loads and material safety design factors was expressed by a safety index and reliability. Although the resulting reliability varies with material selection, the suggested criteria provide a uniformly efficient and safe operational structure.