Probabilistic structural analysis methods for select space propulsion system structural components (PSAM)

Abstract

The purpose of doing probabilistic structural analysis is to provide the designer with a more realistic ability to assess the importance of uncertainty in the response of a high performance structure. The objective of this five-year contract effort (NASA Contrast NAS3-24389) on Probabilistic Structural Analysis Methods (PSAM) is the development of several modular structural analysis packages capable of predicting the probabilistic response distribution for key structural variables such as stress, displacement, natural frequencies, buckling loads, transient responses, etc. The structural analysis packages include stochastic modeling of loads, material properties, geometry (e.g. tolerances), and boundary conditions. The structural analysis solution is in terms of the cumulative distribution function (CDF) and confidence bounds. Two methods of probability modeling are included in the analysis packages. One of these is the well established Monte Carlo simulation method; the other is a fast probability integration (FPI) algorithm which will be discussed in the paper. PSAM tools can be used to estimate structural safety and reliability, while providing the engineer with information on the confidence that should be given to the predicted behavior. Perhaps most critically, the PSAM results provide information to the designer on those variables for which the design is most sensitive.