Computational Models to Predict the Structural Reliability of Aerospace Systems

Three case studies are presented in which computational-based methodologies have been used to assess structural reliability in the aerospace industry. The studies involve hot section turbine disks of a helicopter engine, fan blades of a commercial airline engine and bearings in an auxiliary power unit. In all cases, the results of the computational models were used to support the certification process for design and application changes. The statistical variation in design and usage parameters including geometry, materials, speed, temperature and other environmental factors are considered. The response surface approach was used to construct a durability performance function. This performance function is used with the first order reliability method (FORM) to determine the probability of failure and the sensitivity of the failure to the design and usage parameters. A hybrid combination of perturbation analysis and Monte Carlo simulation is used to incorporate time dependent random variables. System reliability is used to determine the system probability of failure, and the sensitivity of the system durability to the design and usage parameters.