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28TH INTERNATIONAL CONGRESS OF THE AERONAUTICAL SCIENCES ENERGY-BASED METHOD FOR GAS TURBINE ENGINE DISK BURST SPEED CALCULATION Anton N. Servetnik Central Institute of Aviation Motors, Moscow, Russia servetnik@ciam.ru Keywords: spin disk testing, burst speed, fracture criterion, strain energy density Abstract U* - critical value of strain energy density U*aver - critical value of strain energy density FE modeling of burst speed tests of gas turbine obtained at average values of monotonic tensile engine (GTE) disks using stress-strain tests properties confirmed by tensile tests of U*min - critical value of strain energy density specimen was carried out. Stress strain state obtained at minimal values of monotonic tensile (SSS) of disk during loading was determined tests using the MSC. Software and ANSYS n100% - rotor speed at maximum engine regime commercial FE method software. Incremental nburst - burst speed reduced to n100% theory of plasticity with isotropic hardening was nKB - burst margin used to determine the distribution of plastic ΔR - radial elongation of disk strains of disks during loading. It was shown a R, r - radius strong sensitivity of the burst speed to the r* - radius of disk cylindrical section choice of the yield function. Burst speed test results of various disk configurations and thermo-mechanical loadings were compared 1. Introduction with three-dimensional elastic-plastic FEM In recent years the GTE development and analysis results using energy-based fracture certification efforts actively have been engaging criteria. the calculations which have made it possible to Nomenclature assess a load-carrying capability of disk (burst speed) that is made from material having the ij - strain tensor components most unfavorable mechanical properties instead pl - plastic strain of the experimental disk strength validation. ij - stress tensor components Many methods have been developed to assess 1 - first principal stress the burst speed of disks. The limit equilibrium 2 - second principal stress method is the traditional method to assess disk 3 - third principal stress load-carrying capability during designing [1].  - engineering circumferential stress This method is based on the assumption that r - engineering radial stress fracture occurs over meridian or cylindrical disk B - ultimate strength sections (r = r*) when: eqv - equivalent stress U - strain energy density   (r )   B (r ) , (1) Uaver - average strain energy density obtained at calculations made by average values of  r (r * )   B (r * ) . (2) mechanical material properties Umin - minimal strain energy density obtained The condition (1) means that circumferential at calculations made by minimum values of stresses are equal to ultimate strength of mechanical material properties 1 ANTON SERVETNIK material in all the points of meridian disk function. Different yield surfaces with the use of section. The condition (2) means that radial Hosford model [5] have been investigated to stresses are equal to ultimate strength over find the best suited surface shape. In this work cylindrical section at radius r*. Criteria (1) and incremental theory of plasticity with isotropic (2) should be used simultaneously. When hardening was used to determine the determining the burst speed by this method, distribution of plastic strains of disks during simple calculative schemes are used that don’t loading. take into account influence of stress concentration, 3D SSS, effect of mating parts Following the technique proposed, the and real thermal field of disk. The distinction calculations have been made on two aviation between calculative values and experimental GTE disks (fig.1 and fig.2). data comes to 20% in some cases. Use of FEM in calculations makes it

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