LIFE PREDICTION OF A GAS TURBINE DISC USING THE FINITE ELEMENT METHOD

Abstract. In this paper, an FE detailed study of a gas turbine test disc, subjected to similar conditions as in the rim-spinning test, is presented. Finite element analysis were derived from a plain disc (without cracks) and for a geometry with two types of cracks, both at the notch root of the blade insert and located in the corner and in the centre (central crack). A crack aspect ratio of (a/c)=1 was assumed. Fracture mechanics parameters, J integral and K were used in the assessment, and these were computed with the linear elastic and elastic plastic finite element method. Using a crack propagation program with appropriate fatigue creep crack growth rate data, previously obtained in specimens for the nickel base superalloy IN718 at 600ºC, fatigue life predictions were made. The predicted life results were checked against experimental data obtained in real test discs, and very good agreement was found. The FE method, based on experimental fatigue data obtained in small laboratory specimens, have shown a great potential for development, and may be able to reduce the enormous costs involved in the testing of real size components and replace tests made in test components. Resumo. Neste artigo apresenta-se um estudo de propagação de fissuras realizado num disco de turbina de teste, em condições semelhantes às de ensaio, recorrendo ao método do dos elementos finitos para obter os parâmetros da mecânica da fractura. Fez-se uma análise detalhada de tensões e simulou-se