scholarly journals Numerical fatigue analysis of the turbine components under low cycle fatigue (LCF) conditions

2006 ◽  
Vol 127 (4) ◽  
pp. 54-60
Author(s):  
Lucjan WITEK
Keyword(s):  
Low Cycle Fatigue ◽  
High Stress ◽  
Time History ◽  
Fatigue Analysis ◽  
Cycle Fatigue ◽  
Linear Finite Element ◽  
Turbine Disc ◽  
Static Calculation ◽  
Critical Components ◽  
Total Damage

This paper presents results of the stress and fatigue analysis of the turbine disc and blade. A non-linear finite element method was utilized to determine the stress state of the turbine components under operational condition. A critical, high stress zones were found at the several region of turbine. Results obtained from the preliminary static calculation were next used into total fatigue life (S-N) analysis performed for the load time history equivalents to 1-hours work of engine under operating flight. In this analysis, the number of hours to the total damage of the critical components of turbine subjected to low cycle fatigue was estimated.

High-Cycle Fatigue of Fan Blades Accounting for Fluid-Structure Interaction

2012 ◽  
Author(s):  
Priyanka Dhopade ◽  
Andrew J. Neely ◽  
John Young ◽  
Krishna Shankar
Keyword(s):  
Gas Turbines ◽  
High Cycle Fatigue ◽  
Low Cycle Fatigue ◽  
High Stress ◽  
Experimental Studies ◽  
Peak Stress ◽  
Coupled System ◽  
Fatigue Analysis ◽  
Cycle Fatigue ◽  
Fully Coupled

Gas turbine engine components are subject to both low-cycle fatigue (LCF) and high-cycle fatigue (HCF) loads. To improve engine reliability, durability, and maintainability, it is necessary to understand the interaction of LCF and HCF in these components, which can adversely affect the overall life of the engine. The LCF loads result from the aircraft flight profile and are typically high stress, nominally rotational and aerodynamic loads. HCF loads are a consequence of high frequency vibrations, such as the fluctuating loads on blades as they rotate through the wakes from the upstream stator vanes. This paper demonstrates the importance of a fully coupled FSI analysis in conjunction with a fatigue analysis to predict the effect of representative fluctuating loads on the fatigue life of blisk fan blades. The fully-coupled FSI analysis is compared to the partially coupled FSI analysis and it is found that the former better predicts the the structural response of the titanium alloy blade to the wake impingement from the upstream stator. This results in a non-linear stress history compared to the linear response of the partially coupled system which also under-predicts the peak stress by 24%. The fatigue analysis shows the blade will fail near the root with a maximum damage of 1.079(10−17) using Miner’s rule to calculate cumulative damage. The implications of this research can influence future experimental studies that aim to generate meaningful fatigue data, which will assist in the management of safe operation of gas turbines.

Low-Cycle Fatigue Behaviour of Gas Turbine Alloys

1974 ◽  
Vol 188 (1) ◽  
pp. 321-328 ◽  
Author(s):  
W. J. Evans ◽  
G. P. Tilly
Keyword(s):  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
High Stress ◽  
Cyclic Creep ◽  
Fatigue Curve ◽  
Fatigue Behaviour ◽  
Material Surface ◽  
Tension Stress ◽  
Cycle Fatigue ◽  
Stress Tests

The low-cycle fatigue characteristics of an 11 per cent chromium steel, two nickel alloys and two titanium alloys have been studied in the range 20° to 500°C. For repeated-tension stress tests on all the materials, there was a sharp break in the stress-endurance curve between 103 and 104 cycles. The high stress failures were attributed to cyclic creep contributing to the development of internal cavities. At lower stresses, failures occurred through the growth of fatigue cracks initiated at the material surface. The whole fatigue curve could be represented by an expression developed from linear damage assumptions. Data for different temperatures and types of stress concentration were correlated by expressing stress as a fraction of the static strength. Repeated-tensile strain cycling data were represented on a stress-endurance diagram and it was shown that they correlated with push-pull stress cycles at high stresses and repeated-tension at low stresses. In general, the compressive phase tended to accentuate cyclic creep so that ductile failures occurred at proportionally lower stresses. Changes in frequency from 1 to 100 cycle/min were shown to have no significant effect on low-cycle fatigue behaviour.

Turbine Blade Life Prediction Using Fluid-Thermal-Structural Interaction Modelling

2015 ◽  
Author(s):  
I. A. Ubulom ◽  
K. Shankar ◽  
A. J. Neely
Keyword(s):  
Life Prediction ◽  
Low Cycle Fatigue ◽  
Experimental Testing ◽  
Fluid Structure Interaction ◽  
High Stress ◽  
Time History ◽  
Life Assessment ◽  
Fluid Structure ◽  
Operational Conditions ◽  
Structure Interaction

The stringent structural requirements posed on aircraft engines, especially the high pressure turbine blades, result from the diversity of the extreme operational conditions they are subjected to. The accurate life assessment of the blades under these conditions therefore demands accurate analytical tools and techniques, and also an elaborate understanding of the operational conditions. Given the drive to reduce cost related to experimental testing, numerical approaches are often adopted to aid in the initial design stages. With recent advancement in numerical modelling, the simultaneous integration of the various numerical codes of fluid flow and structural analysis (otherwise known as fluid-structure interaction) is projected to provide reliable input into fatigue life prediction programs. This study adopts the numerical method of fluid-structure interaction to investigate the fatigue properties of the Aachen turbine test case. A load-time history obtained for the high stress monitor position is superimposed on that from a quasi-static FE solution, and used as input into a fatigue estimation tool. The low cycle fatigue (LCF) is estimated using the Basquin-Coffin-Manson correlation with corrections for mean stress and multi-axial fatigue effects. An FFT analysis of the fluctuating aerodynamic loads show signals with significant high frequency content. There is noticeable increased energy signal at the rotor inlet as compared to stator inlet. The stator inlet signals, however, are characterized by multiple resonances of frequency with lower energy content. By avoiding the resonances, the fatigue analysis predicts a safe design with a safety factor level of 3 for the rotor.

A Revisit of Material and Structural Failures

2015 ◽  
Author(s):  
Sheldon Wang
Keyword(s):  
Low Cycle Fatigue ◽  
High Stress ◽  
Engineering Practice ◽  
Material Failure ◽  
Cycle Fatigue ◽  
Structural Failure ◽  
Column Buckling ◽  
Typical Material ◽  
Structural Failures ◽  
To Come

In this paper, we revisit the issues related to material and structural failures. In particular, we employ a similar bridging function between the typical structural failure, the so-called column buckling, and the typical material failure under compression, to link the low stress high cycle and the high stress low cycle fatigue. A part of the intention of this paper is to come up with simple formulas as guidelines in engineering practice for both material and structural failures in both static and dynamic situations.

Shear Strength of a Thermal Barrier Coating Parallel to the Bond Coat

1998 ◽  
Vol 120 (1) ◽  
pp. 26-32 ◽  
Author(s):  
T. A. Cruse ◽  
R. C. Dommarco ◽  
P. C. Basti´as
Keyword(s):  
Shear Strength ◽  
Thermal Barrier Coating ◽  
Bond Coat ◽  
Low Cycle Fatigue ◽  
High Stress ◽  
Test Method ◽  
Thermal Barrier ◽  
Cycle Fatigue ◽  
Air Plasma ◽  
Barrier Coating

The static and low cycle fatigue strength of an air plasma sprayed (APS) partially stabilized zirconia thermal barrier coating (TBC) is experimentally evaluated. The shear testing utilized the Iosipescu shear test arrangement. Testing was performed parallel to the TBC-substrate interface. The TBC testing required an innovative use of steel extensions with the TBC bonded between the steel extensions to form the standard losipescu specimen shape. The test method appears to have been successful. Fracture of the TBC was initiated in shear, although unconstrained specimen fractures propagated at the TBC-bond coat interface. The use of side grooves on the TBC was successful in keeping the failure in the gage section and did not appear to affect the shear strength values that were measured. Low cycle fatigue failures were obtained at high stress levels approaching the ultimate strength of the TBC. The static and fatigue strengths do not appear to be markedly different from tensile properties for comparable TBC material.

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