Turbine Disk Research Articles

A direct approach to the evaluation of structural shakedown limit considering limited kinematic hardening and non-isothermal effect

This paper presents a novel direct method for the structural shakedown analysis considering limited kinematic hardening and non-isothermal effect. The Melan's static shakedown theorem is extended to consider limited kinematic hardening material and implemented into the Linear Matching Method (LMM) shakedown module. Instead of using a specific kinematic hardening rule and an explicit back stress field, the general nonlinear hardening laws are considered by using a two-surface hardening model. A two-stage procedure is developed in the extended LMM algorithm, which can generate the limited hardening shakedown envelope and the unlimited hardening curve efficiently and accurately. Also, the material non-isothermal effect is considered during the computation process of the shakedown limit by proposing a temperature-dependent hardening factor, in place of a constant and fictitious one. To validate the extended LMM method, a numerical test on a thin cylinder pipe with temperature-independent material properties is performed, and the results match well with ones from literature. Then, a numerical study on a typical aero-engine turbine disk is conducted to investigate the influence of temperature-dependent material properties and operating conditions. Several shakedown curves considering kinematic hardening effect are derived and adequately discussed. As a result, the extended LMM shakedown module is proven to be a robust, efficient and versatile tool for practical industrial problems.

Status and development of powder metallurgy nickel-based disk superalloys

AbstractNickel-based superalloys are crucial materials for the development of aero-engine components, since their excellent properties can meet the demands of turbine disks. For the formation of such alloys, powder metallurgy is considered as the ideal method, due to the resultant uniform composition and structure, fine grain, high yield strength, and good fatigue performance. This paper provides a critical review of the development of powder metallurgy nickel-based disk superalloys, their composition, as well as the evolution of the nickel-based superalloys' microstructure in the past few decades. Moreover, the influence of various elements on the material properties and the three major defects of powder metallurgy superalloys are reviewed. The analysis indicates that these defects may be directly or indirectly caused by the quality of the powder. Therefore, the innovative powder techniques of electrode induction melting gas atomization and spark plasma discharge spheroidization are presented, in order to prepare ceramic-free and superfine nickel-based superalloy powders. The powders prepared by electrode induction melting gas atomization and spark plasma discharge spheroidization have been found to be beneficial in improving the properties of powder metallurgy nickel-based disk superalloys.

Rekayasa Alat Pembuat Disk Runner Dengan Sistim Jig Dan Fixture

Electrical energy at this time is needed in daily life so that the demand for power from the community is so large. PLN in this case as a provider of electric current is very overwhelmed to meet customer demand. For this reason, alternative energy producers called renewable energy are sought, one of which is a micro hydro plant. In West Sumatra alone, PLTMH has considerable potential to reach 500 MW (Source: PLN West Sumatra Regional Research and Development), so that West Sumatra itself has been designated a green energy barn by the Ministry of Energy and Mineral Resources (Source: Ministry of Energy and Mineral Resources). This is a promising prospect to be developed so that PLTMH equipment can be made with the mastery of appropriate technology. Based on the survey that has been done generally making microhydro turbines is still doing manual work with simple production equipment and very low production volume. The delay in making this generator is in the runner which has a disk component as a holder where the blade will produce rotation. Part made has a specific contour shape and repetitive work. Making disk runners through six workmanship sequences using different CAD applications, tools and places. Jig and Fixture is a technological tool that is suitable for manufacturing micro hydro turbine disk runners where the material holder is on the dividing plate while the torch weld cutter is hung on the guide for the cutting process. These assistive tools designed can eliminate the work process. This mobile device can cut circles with a diameter of 200 mm-300 mm, a blade of as many as 28 pieces with the same distance, shape profile and accuracy and meet the ergonomic aspects for the operator.

Dynamic surrogate modeling approach for probabilistic creep-fatigue life evaluation of turbine disks

To improve the modeling accuracy and simulation efficiency of probabilistic creep-fatigue life evaluation, a decomposed collaborative time-variant Kriging surrogate model (DCTKS) is proposed by absorbing the strengths of extremum selection technique and Kriging model into decomposed collaborative strategy. The probabilistic creep-fatigue life evaluation of a typical turbine disk is considered as one case to evaluate the proposed DCTKS method with respect to fluctuation of transient loads, nonlinearity of material properties and variability of models. In respect of this study, we find that the probabilistic creep-fatigue life of the turbine disk under the reliability degree of 0.998 7 is 946 cycles, and the transient fluctuating loads (body temperature and rotor speed) are the main factors of influencing creep-fatigue life. Through the comparison of methods (DCTKS, Monte Carlo simulation method, Kriging surrogate method, decomposed collaborative response surface method), the proposed DCTKS is demonstrated to possess the computational advantages in efficiency and accuracy for probabilistic creep-fatigue life evaluation.

Effect of Hot Extrusion on the Flow Behaviour of a Nickel-Based P/M Superalloy

This research investigated the effect of hot extrusion on the flow behaviour of nickel-based superalloy FGH4096 by hot compression experiments in the temperature range from 1020 to 1110 °C and strain rates ranging from 0.1 to 0.001 s-1. The influence of the hot extrusion on the initial microstructures, work hardening rate, strain rate sensitivity, and activation energy of deformation were discussed. The results show that the extruded microstructure is constituted by the fine dynamic recrystallisation of grains. The true strain-true stress curves show that the as-HIPed and as-HEXed FGH4096 superalloy present double flow stress peaks and discontinuous flow softening. The as-HEXed FGH4096 is easily dynamically softened at high temperatures and high strain rates compared with as-HIPed microstructures. As for the work hardening rate, the as-HEXed FGH4096 exhibits higher θ values than that of as-HIPed. It is beneficial to the homogenous deformation and grain refinement during subsequent turbine disk forging. Comparing to as-HIPed FGH4096, the highest strain rate sensitivity value of as-HEXed is 0.306 at 1110 °C. The isothermal superplastic forging of a P/M turbine disk may be carried out at this temperature. The deformation activation energy value of the as-HIPed FGH4096 is lower which means that dislocation sliding and climbing can be easily initiated in the as-HIPed alloy.

Study of Mechanical Properties Stability in the Production of Turbine Disks for Gas Compressor Units

A statistical analysis of the baseline strength characteristics of the EI698-VD alloy disks of high-pressure turbines of the NK family engines operating as a part of gas compressor units is performed. The results of the assessment of mechanical properties stability in the disk production during the period 1998–2015 are presented.

Reliability assessment for system-level turbine disc structure using LRPIM-based surrogate model considering multi-failure modes correlation

This paper presents a probabilistic analysis framework for the reliability evaluation of turbine disc considering the correlation of multi-failure modes. A system-level zone division method is first applied to decompose the whole structure into different serial zones. Due to the same input random variables, there is correlation between failure modes. Thus, a mathematical copula function method is introduced to quantify the correlation between failure modes after reliability calculation of separate zones, during which process, dependent random variables are transformed to independent ones using Nataf transformation method. Meanwhile, to guarantee the accuracy and efficiency of calculation, adaptive surrogate model based on local radial point interpolation method (LRPIM) is established in each zone. Two main failure modes, i.e., low cycle fatigue and creep-fatigue are considered during the reliability analysis on a turbine disc. The results reveal that the reliability of the turbine disc changes with the correlation between failure modes. Also, sensitivity analysis shows that rotating speed and maximum temperature are two dominant factors affecting the turbined disc's reliability. Finally, the comparisons among three methods including the proposed method, the zone-based method without considering correlation and Monte Carlo (MC) method based on physics of failure (POF) of correlation are conducted. It is demonstrated that the proposed method in this study is more efficient and accurate for evaluating structural reliability with multi-failure modes coupling. Moreover, the proposed method provides an available prospect for reliability-based design optimization of multiple failure structure, contributing to enhance reliability in mechanical design.

AK-ARBIS: An improved AK-MCS based on the adaptive radial-based importance sampling for small failure probability

The pivotal problem in reliability analysis is how to use a smaller number of model evaluations to get more accurate failure probabilities. To achieve this aim, an iterative method based on the Monte Carlo simulation and the adaptive Kriging (AK) model (abbreviated as AK-MCS) has been proposed in 2011 by Echard et al. But for small failure probability, the number of the candidate points is extremely large for convergent solution. These points need to be evaluated by the current Kriging model to select the best next sample for updating the Kriging model in AK-MCS method, and the large candidate points will make the adaptive updating process of Kriging model much more time-consuming. Therefore, to improve the applicability of the AK-MCS method for small failure probability, the adaptive radial-based importance sampling (ARBIS) is employed to reduce the number of candidate points in the AK-MCS method, and an ARBIS combined with AK model method (abbreviated as AK-ARBIS) is proposed. The idea of the ARBIS is adaptively to find the optimal β-sphere, i.e., the largest sphere of the safe domain, and then samples inside the optimal β-sphere is directly recognized as safety and do not need to call the true limit state function to judge their states (safe or failed). During the adaptive process of finding the optimal β-sphere, the Kriging model is ceaselessly updated layer after layer based on the U learning scheme in each sampling pool which only contains the samples between the current spherical rings. The updating process of Kriging model stops until the optimal β-sphere is adaptively found and the convergent condition is satisfied. By finding the optimal β-sphere, the total number of candidate samples is reduced which only includes the samples outside the optimal β-sphere. Besides, the whole candidate sampling pool is partitioned into several sub-candidate sampling pool sequentially. The proposed method not only inherits the advantage of the AK-MCS but also reduces the reliability analysis time of the AK-MCS from two aspects. One is the size reduction of the candidate sampling pool, the other is the reduction of the actual limit state function evaluations because the sampling points locating inside the adaptively searched optimal β-sphere do not need to participate in the training process. By analyzing a highly nonlinear numerical case, a non-linear oscillator system, a simplified wing box structural model, an aero-engine turbine disk and a planar ten-bar structure, the effectiveness and the accuracy of the proposed AK-ARBIS method for estimating the small failure probability are verified.

Stress-strain calculation and fatigue life assessment of V-shaped notches of turbine disk alloys

For local stress-strain behavior modeling at the notch root, both the Neuber's rule and equivalent strain energy density (ESED) method are commonly utilized in engineering practice, in which the former overestimates notch elasto-plastic responses while the latter gives conservative predictions. In this work, a correction coefficient related to the effective Poisson's ratio veff is proposed to quantify the weight of dissipated heat energy term with the modified ESED model. Notch-root strains predicted by the proposed model are compared with nonlinear FE calculations of GH4169 and TC4 V-shaped notched-bars, in which the proposed solution provides good agreement with FE results for both cases. Then, consulting the idea of local stress-strain approaches, a fatigue lifing model is derived assuming that the notched specimens fail once reach the critical total strain energy as same as that of smooth ones. Results indicated that prediction accuracy of local equivalent strains at notch roots is improved, and yields better life predictions than the Ellyin's model for the two alloys.

The Physical Modelling of High Speed Broaching of the Heat-Resistant Steels for Studies Surface Layer Quality

Abstract The main idea of the work is to create a physical model of high speed broaching heat-resistant materials is used to study the parameters of the surface layer quality. Modelling is a method of mediated cognition, in which the object under study is in some correspondence with the model, and the object-model is capable in some way or another to replace the original at some stages of the cognitive process. Physical modelling is primarily distinguished by the fact that studies are conducted on models with physical similarity, i.e. preserving completely (or at least partially) the nature of the phenomena. The work of the broach can be likened to the work of a number of planning cutter displaced relative to each other by a small amount, which is called lifting (feed per tooth). Therefore, for experimental work, a planning cutter of a special geometric was designed and manufactured – a physical model of a broach, in which geometric, mechanical and dynamic similarity is realized. The article also presents an experimental justification for the use of the created physical model in the study of the surface quality parameters of the, tab grooves of turbine and compressors disks made of heat-resistant materials.

Detection and analysis of high temperature fatigue fracture surface oxygen diffusion of GH4133B superalloy used in turbine disk of aero-engine

The chemical contents on the fatigue fracture surface of GH4133B superalloy piece suffering tension-tension fatigue and operated at high temperature 600 ºC is analyzed using an energy dispersive spectrometer, and the element content percentages at the position of carbide inclusion and that of second-phase particle in the fatigue source region are measured. It is shown that under the conditions of high temperature and air environment, the carbon element in the carbide inclusion can be easily oxidized, which results in accelerating fatigue crack nucleation and microcrack generation, reducing the fatigue crack initiation lifetime. The oxygen concentration is detected on the fatigue fracture surface along the crack propagation direction, the oxygen diffusion model is constructed, and the oxygen concentration gradient equation is derived. It is found that the oxygen content decreases gradually along the crack propagation direction, suggesting that at the crack initiation and short crack propagation stage, the alloy element reacts sufficiently with oxygen for a long time, and the oxidation accelerates the crack initiation, while at the long crack growth stage, the crack propagation rate is faster, so the alloying elements do not have adequate time for reacting with oxygen, resulting in the low oxygen content, and the oxidation has a small influence on the long crack propagation rate.

Recrystallisation behaviour and mechanical properties of a novel Re-containing nickel-base superalloy

ABSTRACTA newly developed heavily alloyed polycrystalline nickel-base superalloy containing rhenium and intended as a structural material for turbine discs in gas turbine engines has been studied. Homogenisation and heterogenisation heat treatments were developed for the as-cast superalloy, which led to improving the hot workability as compared to that of as-cast material. electron backscatter diffraction analysis of samples isothermally compressed at temperatures near the solvus temperature showed that continuous dynamic recrystallisation occurred in the superalloy leading to the formation of refined recrystallised structure. These results were used for the development of canned forging processing under quasi-isothermal conditions. The superalloy subjected to canned forging followed by aging exhibited superior high strength and high-temperature capability, while retaining reasonable ductility as compared to known disc superalloys.

Analysis of high temperature fatigue lifetime of GH4133B superalloy used in turbine disk of aero-engine

Based on the S-H cavity model theory and the thermodynamic diffusion equation, the high temperature fatigue lifetime equation is deduced, and the influence of stress amplitude and mean stress on fatigue lifetime is quantitatively analyzed. At high temperature of 650°C, according to the test data of fatigue lifetime of GH4133B superalloy under different stress ratios or alternatively at various maximum stress levels, the nonlinear regression analysis method is applied to identify the material parameters in the fatigue lifetime equation, and a 3D Nf-σm-σa curve surface is plotted. The comparison between theoretic fatigue lifetime Nfp and test one Nft indicates that the fatigue lifetime equation derived from the microstructure evolution of metallic materials can accurately predict the fatigue lifetime of GH4133B superalloy under different cyclic loading parameters. Finally, a parameter γ is introduced to characterize the effect of mean stress σm and stress amplitude σa on fatigue lifetime Nf of GH4133B superalloy. It is suggested that the effect of mean stress σm on Nf is larger than that of stress amplitude σa on Nf under the condition of tensile-tensile fatigue loading.

Modal Analysis of Mistuned Turbine Blade Packet Due to Combined Blade and Lacing Wire Damage

The turbine disk blade system is a cyclic symmetric structure, initially tuned with all its blades perfectly identical in geometry and material properties; similarly interconnecting lacing wires are of equal stiffness. The cyclic symmetry of the bladed disks gets destroyed due to small differences in material properties or geometric variation between individual blades or lacing wires causing mistuning. Although mistuning is typically small, it can have a drastic effect on the dynamic response of the system. In particular, mistuning can also cause vibration localization for a few blades and the associated concentration of vibration energy can lead to an increase in blade amplitude and stress levels. Numerical simulations are performed with the characteristic equations of the simplified continuum model. Two different damage severity indices are included in the model to study the combined effect of cracked blades and damaged lacing wires on the natural frequencies of grouped blades. This study highlights the characteristic changes in the sub modal frequencies under combined damage in a stand still position. Although the major cause of mistuning is blade damage, lacing wire damage is more frequent and often acts as a precursor to blade damage and thus the present study focuses on mistuning due to combined damage.

A Modified Model for Nonlinear Fatigue Damage Accumulation of Turbine Disc Considering the Load Interaction Effect

Fatigue damage accumulation theory is one of the core contents in structure fatigue strength design and life prediction. Among them, the nonlinear damage model can overcome the shortcomings of the linear damage model, which takes the loading sequence effect into account. Besides, the loading interaction cannot be ignored for its profound influence in damage accumulation behavior. In the paper, some commonly-used methods of the linear and nonlinear fatigue damage accumulation theory are investigated. In particular, a modified nonlinear fatigue damage accumulation model which considers the effects of loading sequences as well as loading interactions on fatigue life is developed, and a load interaction parameter is obtained by analyzing damage models which assumes that the load logarithm ratio between adjacent stress levels can characterize this phenomenon. Finally, the modified model is employed to predict the fatigue life of high pressure turbine disc. Moreover, comparison is made between the experimental data as well as the predicted lives using the Miner’s rule, the Ye’s model, and the modified model.

Surrogate-based optimization with improved support vector regression for non-circular vent hole on aero-engine turbine disk

This paper investigates a structural optimization for the non-circular vent hole on an aero-engine turbine disk. A novel optimization approach, namely SO-ISVR (the surrogate-based optimization using an improved support vector regression), for the vent hole design is developed. ISVR (the improved support vector regression) is proposed to extract some ignored valuable information from the existing training data by using the least squares method, so as to improve the performance of SVR (support vector regression). To validate the advantages of SO-ISVR, another two optimization approaches are also developed. They are SO-SVR (the surrogate-based optimization using SVR) and FEMO (the finite element method based optimization). The results show that ISVR is suitable and valuable in engineering optimization. Compared to the initial scheme, the maximum von Mises stress of the optimal scheme obtained by SO-ISVR is reduced from 1189.488 MPa to 948.530 MPa. Further comparative study for SO-ISVR, SO-SVR, and FEMO demonstrates that SO-ISVR possesses some advantages in both computational efficiency and optimization effect.

Tensile Deformation and Fracture Behaviors of a Nickel-Based Superalloy via In Situ Digital Image Correlation and Synchrotron Radiation X-ray Tomography.

Nickel-based superalloys have become key materials for turbine disks and other aerospace components due to their excellent mechanical properties at high temperatures. Mechanical properties of nickel-based superalloys are closely related to their microstructures. Various heat treatment processes were conducted to obtain the desired microstructures of a nickel-based superalloy in this study. The effect of the initial microstructures on the tensile deformation and fracture behaviors was investigated via in situ digital image correlation (DIC) and synchrotron radiation X-ray tomography (SRXT). The results showed that the size and volume fraction of γ″ and γ′ phases increased with the aging time. The yield strength and the ultimate tensile strength increased due to the precipitation strengthening at the expense of ductility. The surface strain analysis showed severely inhomogeneous deformation. The local strains at the edge of specimens were corresponded to higher void densities. The fracture of carbides occurred owing to the stress concentration, which was caused by the dislocation accumulation. The fracture mode was dimple coalescence ductile fracture.

Toward the integration of lattice structure-based topology optimization and additive manufacturing for the design of turbomachinery components

Used in several industrial fields to create innovative designs, topology optimization is a method to design a structure characterized by maximum stiffness properties and reduced weights. By integrating topology optimization with additive layer manufacturing and, at the same time, by using innovative materials such as lattice structures, it is possible to realize complex three-dimensional geometries unthinkable using traditional subtractive techniques. Surprisingly, the extraordinary potential of topology optimization method (especially when coupled with additive manufacturing and lattice structures) has not yet been extensively developed to study rotating machines. Based on the above considerations, the applicability of topology optimization, additive manufacturing, and lattice structures to the fields of turbomachinery and rotordynamics is here explored. Such techniques are applied to a turbine disk to optimize its performance in terms of resonance and mass reduction. The obtained results are quite encouraging since this approach allows improving existing turbomachinery components’ performance when compared with traditional one.

Prediction Method and Verification of Fatigue Life for a Turbine Disk with Bolt Hole

In order to improve the fatigue life prediction accuracy of FGH96 material for turbine engine at higher stress gradient notch, such as bolt holes, the new mean stress formula is used in this paper, the effect of stress gradient and size effect are considered at the same time, Fatigue test of FGH96 material inter-stage disc simulation test piece is done, and the parameters in the life prediction equation of the model are fitted. Further study on fatigue test of FGH96 material turbine pin bolt hole simulation unit is done, and test results is compared with the forecast results. The result shows that, the improved fatigue life prediction method has higher accuracy, and the validity of the method is proved.

Influence of rotation speed on the steady cooling effects in the turbine disc cavity

The flow and heat transfer characteristics in the counter-rotating turbine disc cavity is numerically simulated using the rng k-ε turbulence model, and the influence of rotation speed on the steady flow and the cooling effects is further investigated. The results indicate that the influence of rotation speed in low speed range on the upstream disc surface heat transfer depends on the relative driving action of rotating radial force and intake inertial force on the flow near the upstream disc. With respect to the downstream disc, the convective heat transfer coefficient on the disc surface in the lower radius region decreases while the one in the higher radius region increases with the increase of rotation speed.