Probabilistic High-Cycle Fretting Fatigue Assessment of Gas Turbine Engine Components (original) (raw)
Related papers
Volume 6: Structures and Dynamics, Parts A and B, 2010
This paper reports the results of an investigation focused on identifying the necessary steps required to develop a probabilistic fracture mechanics-based methodology for treating high-cycle fretting fatigue in military engine disks. The current methodology based on finite-element method (FEM) modeling, analytical contact stress analysis, and probabilistic fracture mechanics for analyzing low-cycle fretting fatigue is highlighted first. Incorporation of highfrequency vibratory stress cycles into a composite mission profile containing mostly low-cycle stresses requires the use of the Campbell diagram and the need to identify the mode shape, frequency, and forcing function for blade excitation induced by stator wake, flutter or rotating stall. Forced response computation methods for addressing these phenomena in the literature are reviewed to assess their applicability for integration with a contact stress analysis and a probabilistic fracture mechanics life-prediction code. This overview identifies (1) a promising path for combining vibratory stress computation, FEM structural modeling, contact stress analysis, and probabilistic fracture mechanics for treating high-cycle fretting fatigue at the attachment region of engine disks, and (2) a new approach for treating high-cycle fretting fatigue due to vibratory stresses separately from low-cycle fretting fatigue at various positions of a fan-speed profile.
In this work an attempt is made to simulate the life of a rotating element subjected to the phenomenon of fatigue fretting using finite element analysis. A numerical model is being proposed to analyse the fretting failure phenomenon. The model explores the physics of the problem with a view to capture micro slip at the interface between the root and the disc. Some of the parameters that affect fretting are dissimilar material component types, kinds of fit, geometry of the mating part etc. The effect of these parameters on the extent of fretting is being analysed using the commercial finite element tool ANSYS. This will enable one to gauge failure criterion of the part to be designed under different cyclic loading conditions subjected to fatigue fretting failure. It is found out from the present analysis that the bottom tooth of the fir tree structure experiences the maximum stress induced at the interface. Also the stress increases non-linearly as the speed increases. As the flank angle is increased, the fatigue life at higher speeds decreases. Also the equivalent stress decreases as the number of teeth increases. Original Research Article
International Journal of Computer Applications in Technology, 2007
Thermal stress, wear and material damage produce effects of high-cycle fatigue failures in aircraft engines. The loading configuration on turbine blades of aircraft engines consists of an axial load. The axial load is the centrifugal force combined with the tensile and compressive loads, caused by the natural vibrations of the blades themselves. Low-cycle fatigue and high-cycle fatigue loading tests simulate these flight loads experienced by engine components. The objective of this study is to illustrate the most important features of high-cycle fatigue to pass the final controls for the assurance of quality of turbine blades in aircraft engines. A finite element model, useful to predict the results of experimental tests, is also presented.
EFFECTS OF TRANSIENT LOAD ON GAS TURBINE BLADE STRESS AND FATIGUE LIFE CHARACTERISTIC
International J. of Multidispl.Research&Advcs. in Engg.(IJMRAE), 2018
The turbine blade is the most important component in the jet engine gas turbine. The common fatigue failures of the blade include the thermo-mechanical fatigue. Firstly, the finite element simulation of the blade is carried out in the working condition including the centrifugal load and mechanical load. The aim of this work was to develop and implement methods for the resource calculation of the jet turbine blade in which fatigue zone were detected during the load. The approach is based on a directstep simulation of the load point based on the finite-element method (FEM).According to the simulation results of the thermos-mechanical load, the stress distribution of the blade body is reasonable in the working condition load; the stress level on the blade suction surface is higher than the pressure surface; in the blade body, the maximum Von Mises stress is 126 MPa, and the location of the minimum fatigue life is close to the blade shroud. Above simulation results is very useful for the structural design and fatigue experiment. Secondly, the stress and thermo-mechanical fatigue life characteristic are both analyzed with ANSYS software. Through the transient structure stress analysis, the stress-time history in the blade body is obtained; through the thermo-mechanical fatigue analysis, the fatigue zone of the blade first appears in the middle of the blade exhaust side. Based on these virtual results. These results are significant for the blade fatigue failure in the future.
Multiaxial high-cycle fatigue criteria and life prediction: Application to gas turbine blade
International Journal of Fatigue, 2016
A recent work conducted by the authors [Maktouf, W., Saï, K., 2015. An investigation of premature fatigue failures of gas turbine blade. Engineering Failure Analysis, 47, 89-101.] demonstrated that the root cause of the premature blade failure was caused by high-cycle fatigue (HCF) mechanism initiated at a localized carbon-rich area inducing grain boundary brittleness. The blade was subject to multiaxial cyclic loadings during its service life and any attempt to assess component fatigue strength leads to the question of choosing an appropriate fatigue design criterion. In this paper several multiaxial fatigue models are applied as post-processing step of the Finite Element Analysis (FEA) output results and the estimated fatigue lifetimes were assessed under different loading conditions. The material fatigue parameters, required as an input to the selected fatigue models were determined through a series of bending and torsion tests on specimens made of aged Inconel 718. A numerical post-processing algorithm was developed for Fatemi-Socie fatigue criterion and included as additional post-computation model in the used computer aided fatigue damage evaluation tool. The authors point out that the majority of the multiaxial fatigue studies available in the literature are conducted mainly for correlating the experimental laboratory results on specimens while they have been used in the frame of this study to investigate their application to an industrial case.
Fatigue & Fracture of Engineering Materials & Structures, 2016
paper presents an assessment of the performance of a set of multi-axial high-cycle fatigue criteria on the basis of a series of fretting fatigue experiments. We carried out tests on a creep-resistant chromium steel material used for steam-turbine blades. The first type of experiment employed the classical cylinder-on-flat geometry with flat dog-bone specimens. The second set of experiments adopted dovetail geometry. Various loads were applied in order to capture a wide range of contact slip amplitudes. A set of eight plain multi-axial fatigue criteria was applied to the numerically simulated stress response in the contacts during a single load cycle. Methods, which originated in the so-called theory of critical distances, were used for correcting the results in order to take the stress gradient effect into account. A simple factor based on slip amplitudes is introduced in order to consider the surface damage and is calibrated for the McDiarmid method. This criterion provided the best estimates of the most probable cracking sites.
Volume 10B: Structures and Dynamics, 2020
A method of fluid-structure interaction coupling is implemented for a forced-response, vibration-induced fatigue life estimation of a high-pressure turbine blade. Two simulations approaches; a two-way (fully-coupled) and one-way (uncoupled) methods are implemented to investigate the influence of fluidsolid coupling on a turbine blade structural response. The fatigue analysis is performed using the frequency domain spectral moments estimated from the response power spectral density of the two simulation cases. The method is demonstrated in light of the time-domain method of the rainflow cycle counting method with mean stress correction. Correspondingly, the mean stress and multiaxiality effects are also accounted for in the frequency domain spectral approach. In the mean stress case, a multiplication coefficient is derived based on the Morrow equation, while the case of multiaxiality is based on a criterion which reduces the triaxial stress state to an equivalent uniaxial stress usin...
Fatigue Life Estimation Procedure for a Turbine Blade Under Transient Loads
Fatigue analysis and consequent life prediction of turbomachine blading requires the stress load history of the blade. A blade designed for safe operation at particular constant rotor speeds may, however, incur damaging stresses during start-up and shut-down operations. During such operations the blade experiences momentary resonant stresses while passing through the criticals, which may lie in the speed range through which the rotor is accelerated. Fatigue due to these transient influences may accumulate to lead to failure. In this paper a technique for fatigue damage assessment during variable-speed operations is presented. Transient resonant stresses for a blade with nonlinear damping have been determined using a numerical procedure. A fatigue damage assessment procedure is described. The fatigue failure surface is generated on the S-N-mean stress axes and Miner's Rule is employed to estimate the accumulation of fatigue.
Gas turbine and aero engine components are cost intensive due to the complexity of design, fabrication and the exotic alloys used. Rotor system includes elastic shaft with distributed mass. Bladed disksare typically designed to have identical blades there are always random deviations among the blades caused by manufacturing tolerances, wear, and other causes. Even though mistuning is typically small, mistuned bladed disks can have drastically larger forced response levels than the ideal, tuned design. The attendant increase in stresses can lead to premature HCF of the blades. Even Foreign Object Damage during operation can significantly reduce the life of the critical parts like compressor and fan blade airfoils. The severity of Foreign Object Damage induced notches can vary significantly, depending on their geometry and location on the aerofoil. HCF caused by large resonance stresses is one of the main problems in turbine blade design. Fatigue analysis is done for the notched rotating blade, the alternating stress, fatigue stress concentration factor and life of the rotating blade is found for the known stress concentration factor. Failure analysis of the rotating blade is carried to give the information to maintenance engineer for critical usage of turbine blades.