The stochastic Finite-Element-Method (FEM) is a suitable tool to assess the reliability of lifetime prediction models for complex components. Due to its demands on the number of FE analysis it has been rarely used on FE models of real components under realistic operational conditions. In the following a response surface approach is suggested that minimizes the number of FE calculations. Based on a first order method the sensitivity of the failure probability with respect to the random input quantities is evaluated. Subsequently a response surface of higher order, weighting the important and unimportant input uncertainties appropriately, is used to assess the reliability of the lifetime prediction. The method is used to analyze the reliability of typical rotor disks concerning failure due to creep rupture and low cycle fatigue (LCF) during static and transient operation.

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