Reliability analysis for low cycle fatigue life of the aeronautical engine turbine disc structure under random environment

The low cycle fatigue life (LCFL) of the aeronautical engine turbine disc structure is related to the stress-strain level of the disc applied by cyclic load and the life characteristic of the material. The randomness of the basic variables, such as applied load, working temperature, geometrical dimensions and material properties, has significant effect on the statistical properties of the stress and the strain of the disc structure. In most cases, due to the complicated relationship between the LCFL and the basic random variables, it is very difficult to derive the statistical properties of the LCFL analytically, and to analyze the reliability directly. By use of the finite element analysis as a numerical experiment tool, a simulation method is presented to obtain the probability density distributions of the stress level and the strain level at the dangerous points in the turbine disc structure. On the basis of the Linear Damage Accumulation (LDA) law and the simulated probability density distributions of the stress and the strain, two models are presented for the reliability of the LCFL, and the randomness in the life characteristic of the material is taken into consideration in the presented models. The load-life interference and the equivalent probability transformation are developed to construct the third reliability model for the LCFL of the turbine disc as well. The aeronautical engine turbine disc is then introduced to illustrate the feasibility of three reliability models. The calculation results show that the reliability results of models 1 and 2 are in good agreement, which are different from that of model 3. By keeping agreement in the reliability results of three models, we discover an alternative method to identify the damage strength parameter in the LDA law. (c) 2004 Elsevier B.V. All rights reserved.