bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative analysis of chloroplast genomes of Sanguisorba species and insights into phylogenetic implications and molecular dating
Authors: Zhang Guo‐Jian , Zhang Zhi‐Ping , Li Qin‐Qin
Published: November 2022

Sanguisorba is a small genus which consists of about 15 species widely distributed in North America and Eurasia. Previous studies on Sanguisorba are useful for understanding its phylogeny and chloroplast (cp) genome evolution, however, the cp genome resources of Sanguisorba are still limited, and the phylogeny and molecular dating for Sanguisorba and its relatives still need to be further explored. Here, we report four cp genomes of Sanguisorba and conduct comparative analysis of these four Sanguisorba cp genomes plus five previously published ones. The nine cp genomes have a typical quadripartite structure with a total length of 154 282–155 730 bp and their gene content, gene structure and gene order are relatively conserved. Analysis of single copy (SC)/inverted repeat (IR) boundaries shows only very slight boundary differences among the Sanguisorba cp genomes. Eight variation hotspots were screened as excellent candidate markers for future studies in Sanguisorba. Phylogenetic analysis indicated that Sanguisorba is monophyletic and a member of Agrimonieae subtribe Sanguisorbinae. Within Sanguisorba, S. filiformis is the sister group of the six other taxa in the present sampling. Estimation of divergence times indicates that the subtribes Agrimoniinae and Sanguisorbinae diverged at the transition between the Oligocene and the Miocene, and divergent times of Agrimonieae genera ranged from the late Miocene to the Middle Pleistocene. This study enriches the available cp genome resources of Sanguisorba, and it is of great significance to further study of the phylogeny and evolution of Sanguisorba and its relatives.
ZmEREB92 interacts with ZmMYC2 to activate maize terpenoid phytoalexin biosynthesis upon Fusarium graminearum infection through jasmonic acid/ethylene signaling
Authors: Fu Jingye , Wang Liping , Pei Wenzheng , Yan Jie , He Linqian , Ma Ben , Wang Chang , Zhu Chenying , Chen Gang , Shen Qinqin , Wang Qiang
Published: November 2022

Maize (Zea mays) terpenoid phytoalexins (MTPs) induced by multiple fungi display extensive antimicrobial activities, yet how maize precisely regulates MTP accumulation upon pathogen infection remains elusive.

In this study, pretreatment with jasmonic acid (JA)/ethylene (ET)‐related inhibitors significantly reduced Fusarium graminearum‐induced MTP accumulation and resulted in enhanced susceptibility to F. graminearum, indicating the involvement of JA/ET in MTP regulatory network.

ZmEREB92 positively regulated MTP biosynthetic gene (MBG) expression by correlation analysis. Knockout of ZmEREB92 significantly compromised maize resistance to F. graminearum with delayed induction of MBGs and attenuated MTP accumulation. The activation of ZmEREB92 on MBGs is dependent on the interaction with ZmMYC2, which directly binds to MBG promoters. ZmJAZ14 interacts both with ZmEREB92 and with ZmMYC2 in a competitive manner to negatively regulate MBG expression.

Altogether, our findings illustrate the regulatory mechanism for JA/ET‐mediated MTP accumulation upon F. graminearum infection with the involvement of ZmEREB92, ZmMYC2, and ZmJAZ14, which provides new insights into maize disease responses.
Parental environmental effects are common and strong, but unpredictable, in Arabidopsis thaliana
Authors: Latzel Vít , Fischer Markus , Groot Maartje , Gutzat Ruben , Lampei Christian , Ouborg Joop , Parepa Madalin , Schmid Karl , Vergeer Philippine , Zhang Yuanye , Bossdorf Oliver
Published: November 2022

The phenotypes of plants can be influenced by the environmental conditions experienced by their parents. However, there is still much uncertainty about how common and how predictable such parental environmental effects really are.

We carried out a comprehensive experimental test for parental effects, subjecting plants of multiple Arabidopsis thaliana genotypes to 24 different biotic or abiotic stresses, or combinations thereof, and comparing their offspring phenotypes in a common environment.

The majority of environmental stresses caused significant parental effects, with −35% to +38% changes in offspring fitness. The expression of parental effects was strongly genotype‐dependent, and multiple environmental stresses often acted nonadditively when combined. The direction and magnitude of parental effects were unrelated to the direct effects on the parents: Some environmental stresses did not affect the parents but caused substantial effects on offspring, while for others, the situation was reversed.

Our study demonstrates that parental environmental effects are common and often strong in A. thaliana, but they are genotype‐dependent, act nonadditively, and are difficult to predict. We should thus be cautious with generalizing from simple studies with single plant genotypes and/or only few individual environmental stresses. A thorough and general understanding of parental effects requires large multifactorial experiments.
An Integrative Social Identity Model of Populist Leadership
Authors: Uysal Mete Sefa , Jurstakova Klara , Uluşahin Yasemin
Published: November 2022

In recent years, the questions of what populism is and how populist leaders mobilize their followers have been the subject of extensive debate. While the social psychology literature holds unique theoretical tools that can be used to explain leader‐follower dynamics, these have not yet been applied to understand populism and populist leadership. In this paper, we aim to discuss populism as a social‐psychological concept and provide a comprehensive approach to examine the interactions between populist leaders and followers by using the identity leadership model (see New Psychology of Leadership, Haslam et al., 2020). Accordingly, we propose an integrative model in which we suggest that populism should be treated as a social‐psychological concept based on (i) strong ingroup identification; (ii) interactive leadership processes that open spaces to followers for enacting their ingroup identity that end up with mobilization against vertical (e.g., elites) and horizontal (e.g., minorities, refugees, opponents) outgroups; (iii) leader's ingroup prototypicality and identity entrepreneurship that is boosted by using shared grievances, narratives of collective victimhood, and the destabilization of mainstream opponent leaders. Furthermore, by discussing real‐world examples and recent studies, we aim to show how the content of what it means to be ‘us’ and what is seen as moral to ‘us’ can be shaped by populist leaders for mobilization.
Getting a grip: On causation, agency, and the meaning of “manipulation”
Authors: van Aken Erik
Published: November 2022

In the philosophy of causation, manipulationist literature is broadly divided into agency and interventionist accounts. The division between these accounts is partially due to a dispute regarding the meaning of “manipulation”, which specifically questions, “Must one analyse manipulation by appealing to human agency?” This paper attempts to clarify the notion of manipulation and defends the thesis that agency theoristsandinterventionists analyse manipulation by appealing to human agency. However, following Collingwood's work, I argue that there are two ways to interpret “human agency”. With an extended notion of agency in place, I reveal a pathway towards a consensus between the agency and interventionist accounts. Further, I highlight the alleged discrepancies between agency and interventionist accounts, including the issues of scope and objectivity, and suggest additional pathways towards a consensus.
FAITH, SCIENCE, AND NONRELIGIOUS IDENTITY FORMATION AMONG MALE KENYAN YOUTH
Authors: Muriithi Ndereba Kevin
Published: November 2022

The faith and science dialogue has received scholarly attention in the recent past. Within the African landscape at large, the underlying assumption has been that Africans are religious. However, there has been a rising cohort of Africans who are increasingly identified as nonreligious or atheist or agnostic. This research presents a qualitative analysis of the sociocultural factors that affect or influence these minority identities within a pluralistic African context, exploring their emergence and diversities within the African context, with a specific focus on 20 male Kenyan youth who are identified as nonreligious. This research utilized purposive sampling within nonreligious groups and networks. Second, this research aims at exploring how nonreligious identities are constructed, particularly given the concomitant issues surrounding emerging adulthood and new media. This builds up on the theories around youth and identity formation, while foregrounding science and belief as a central theme of study.
Tonic extracellular glutamate and ischaemia: glutamate antiporter system xc− regulates anoxic depolarization in hippocampus
Authors: Heit Bradley S. , Chu Alex , Sane Abhay , Featherstone David E. , Park Thomas J. , Larson John
Published: November 2022

In stroke, the sudden deprivation of oxygen to neurons triggers a profuse release of glutamate that induces anoxic depolarization (AD) and leads to rapid cell death. Importantly, the latency of the glutamate‐driven AD event largely dictates subsequent tissue damage. Although the contribution of synaptic glutamate during ischaemia is well‐studied, the role of tonic (ambient) glutamate has received far less scrutiny. The majority of tonic, non‐synaptic glutamate in the brain is governed by the cystine/glutamate antiporter, system xc−. Employing hippocampal slice electrophysiology, we showed that transgenic mice lacking a functional system xc− display longer latencies to AD and altered depolarizing waves compared to wild‐type mice after total oxygen deprivation. Experiments which pharmacologically inhibited system xc−, as well as those manipulating tonic glutamate levels and those antagonizing glutamate receptors, revealed that the antiporter's putative effect on ambient glutamate precipitates the ischaemic cascade. As such, the current study yields novel insight into the pathogenesis of acute stroke and may direct future therapeutic interventions.

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Key points

Ischaemic stroke remains the leading cause of adult disability in the world, but efforts to reduce stroke severity have been plagued by failed translational attempts to mitigate glutamate excitotoxicity.

Elucidating the ischaemic cascade, which within minutes leads to irreversible tissue damage induced by anoxic depolarization, must be a principal focus.

Data presented here show that tonic, extrasynaptic glutamate supplied by system xc− synergizes with ischaemia‐induced synaptic glutamate release to propagate AD and exacerbate depolarizing waves.

Exploiting the role of system xc− and its obligate release of ambient glutamate could, therefore, be a novel therapeutic direction to attenuate the deleterious effects of acute stroke.
Mist Flow in Through-Tool Minimum Quantity Lubrication Drilling: Two-Phase Flow Simulation and Experimental Observation
Authors: Raval Jay K. , Tai Bruce L.
Published: November 2022

Through-tool minimum quantity lubrication (MQL) drilling has been used in industry for decades, but little information is available on the coolant channel design and the effect on fluid distribution due to the inability of in-situ measurement. This study utilizes an Euler–Lagrange computational fluid dynamics (CFD) model to uncover the two-phase flow behavior in MQL drilling. Air is the primary phase modeled as a compressible and turbulent flow. The lubricant droplets are simulated as discrete particles with a proper size distribution. Two-way coupling and droplet-wall interactions are both considered. The results show that the primary phase can reach velocities in the transonic region and is dependent on the helical path of the channel. In addition, most of the lubricant droplets (>95%) impact the channel wall to form fluid film instead of following the air stream. In the cutting zone, droplets can hardly reach the cutting edges in both circular and triangular channel shapes. Finally, a custom-made drilling testbed, along with a transparent work-material simulant, is used to observe and qualitatively validate these results.
Molecular Simulation of Methane Adsorption Behavior on Coal: Effects of Maturity and Moisture Content
Authors: Miao Yanan , Luan Guoliang , Zhao Chaojie , Li Yong
Published: November 2022

The adsorption behaviors of multiphase fluids in coal are vital for estimating their transfer and flow mechanisms. In this study, taking the classical coal structures as instances, the impacts of maturities and moisture contents of coal on the methane adsorption capacities and thermodynamic properties were analyzed and determined by molecular simulations. Specifically, the simulated pressures were varied from 0 to 16 MPa, and three temperatures (298 K, 323 K, and 348 K) were considered. In addition, the competitive adsorption capacities of water/methane molecules were evaluated and the critical value of moisture content affecting the isosteric adsorption heat of methane was determined. Furthermore, a quantitative relationship between the gas adsorption amount and adsorption equilibrium pressure under a three-phase “solid–gas–liquid” action was established. The simulated results showed that taking the intermediate-rank coals as examples, the absolute adsorption capacities of methane molecules on different moist coals reduced by 28.3%, 35.1%, 46.9%, and 62.3%, respectively (at uniform pressure–temperature status) in comparison to their dry status. In addition, when the moisture content was lower than 1.4 wt%, the average isosteric adsorption heat remained almost stable. However, when the moisture content exceeded 1.4 wt%, the average isosteric adsorption heat increased sharply with the increase in the water content. Finally, linear function formulas yielded a good fitting accuracy range for the low- and intermediate-rank coals; in comparison, for the high-rank coal, an exponential function formula obtained a better fitting accuracy than a linear one.
Atomization Characteristics of Low-Volatility Heavy Fuel for Low-Pressure Direct Injection Aviation Piston Engines
Authors: Liu Rui , Huang Kaisheng , Qiao Yuan , Ji Haocheng , Wu Hao
Published: November 2022

Due to safety and convenience, aviation heavy fuel (AHF) is quite suitable for use as an energy source in aviation piston engines for small aerial drones, although its atomization is an important issue. The purpose of this article is to present the atomization mechanism of AHF during low-pressure direct injection (LPDI) and the results of the investigation of the mixing process and flow state of fuel–air two-phase flows. In this study, experimental data were obtained for parameters of fuel spray, which verified the improved calculation model of LPDI that considered the primary atomization of AHF inside the premixing chamber. The influences of injection pressure, ambient pressure, and AHF temperature on the spray characteristics were compared and analyzed. Increasing the injection pressure reduced the spray cone angle and increased the spray area. The penetration distance increased, and the Sauter mean diameter (SMD) of the fuel droplets decreased. Increasing the ambient pressure had significant effects on penetration distance and SMD. The spray area decreased, and the spray cone angle showed small variations. Increasing the AHF temperature had small effects on the penetration distance, and the SMD obviously decreased with increasing fuel temperature. The spray cone angle increased slightly, and the spray area decreased. The results showed that low-volatility AHF for safe and stable engine combustion could be achieved with air-assisted LPDI. In addition, the efficient atomization of AHF can be effectively implemented through the combined adjustment of injection control and physical and chemical parameters.
Influence of Multiaxial Far Field Loadings on the Fatigue Crack-Growth Behaviour by Using Corner-Crack and Cruciform Specimen
Authors: Conrad F. , Kontermann C. , Blug A. , Bertz A. , Carl D. , Oechsner M.
Published: November 2022

By means of fracture mechanics evaluation concepts, the most accurate possible estimation of the crack growth behaviour of complex and highly loaded structures is to be aimed for a more efficient use of components, a more precise planning of inspection intervals and for the realization of advanced design approaches. Standard fracture mechanics specimen used in materials testing are globally subjected to purely uniaxial loading. In contrast, the technical components usually experience multi-axial stresses due to the external loads and to their complex geometry. The influence of multi-axial far-field loads on the crack propagation rate and the crack closure behaviour is unclear and controversially discussed in literature. In this context, the crack propagation behaviour of uniaxially loaded corner-crack specimens and multiaxially loaded cruciform specimens is systematically studied in this investigation. Here, the multiaxiality condition is characterized by the so-called T-stress and systematically varied within the tests. The results so far show no significant influence of the far-field multiaxiality or the T-stress on the crack propagation behaviour. However, the evaluation of the crack closure behaviour indicates that an engineering approach for thin-walled structures leads to a non-conservative estimation.
A Dedicated Model Reduction Method for Turbo-Machines Using a Critical Speed Subspace
Authors: D’Alessandro Francesco , Festjens Hugo , Chevallier Gael , Cogan Scott , Benamara Tariq , Sainvitu Caroline
Published: November 2022

Finite element models representing industrial scale turbo-machines have reached today a very large number of degrees of freedom. The large size of these models requires the use of reduced order modelling to make the simulations computationally affordable. However, the physical characteristics (i.e. modes shapes and natural frequencies) of a rotating machine depend on the rotating speed of the system and classical modal reduction approaches are not efficient in this case. A classical modal basis does not allow to decompose the unbalance response of a rotating system into independent components because the normal modes are evaluated for a constant rotating speed. They are thus invariant and insensitive to the rotating speed variation. In this work a method is proposed to evaluate a reduction basis composed only by the modes excited when the system runs through its own critical speeds. This method produces an essential basis of modes which is optimal for the identification of the main components of the unbalance response of a rotating system. The development of this reduction basis is firstly formulated mathematically. Then, the ‘critical speed basis’ is employed to reduce a real finite element model of about 100 DOFs and it is compared with a classical modal basis. Finally, the efficiency of the proposed reduction method is tested in a non-linear framework.
Effect of System Mode and Structural Damping Perturbation on the Mistuned Forced Response and Aerodynamic Damping of Embedded Compressor Rotors
Authors: Hegde Shreyas , Inge Jonathan D. , Kielb Robert
Published: November 2022

This paper is a continuation of previous papers by the authors that focuses on predicting the mistuned embedded rotor blade forced response. The compressor under consideration is a part of a 3.5stage rig located at Purdue University. Previously, the current authors have discussed the impact of sideband travelling wave forcing functions on the mistuned response and pinned down the reason for a constant underprediction in the amplification factor. This prompted further research to determine the sensitivity of the response to a known change in the system mode. In the first section of the current paper, the authors perturb the system modes frequencies in a probabilistic manner and compute the influence of the system mode on the mistuning amplification factor. The second part of this study involves determining the impact of a perturbation in the structural damping on the mistuned response. The study is also extended to an aerodynamic dynamic analysis wherein the impact of a perturbation in system mode frequency and structural damping is determined both individually and as a combined influence. Finally, a brief investigation of system eigenvalues and eigenvectors is conducted to understand the impact of mistuning on aerodynamic damping suppression. This analysis is joined with a broad examination of the relationship between damping and the extent of mistuning. The key conclusions from this paper are: 1) The mistuned forced response was highly sensitive to the system mode input, i.e., although the input was probabilistic, the output was deterministic. 2) Since the aerodynamic damping dominates in the case study, a change in the structural damping parameter has minimal effect on the mistuned response, particularly the mistuning amplification factor. 3) The results of the flutter analysis show that a perturbation in the system mode frequency stabilizes the system much faster than a perturbation in the structural damping, and the latter has minimal influence on the eigenvalues of the solution. 4) Under the application of mistuning, compression of the damping components of the complex eigenvalues is dominant over the expansion of the frequency components and is amplified when the structural coupling is not considered. 5) In cases of both random and near alternate blade mistuning, the relationship between mistuning and damping is positive up to a point, after which further increasing mistuning begins to reduce system damping.
Fracture Mechanics-Based Structural Integrity Assessment of Aero-Engine Turbine Disks Under Overspeed Conditions
Authors: Zhu Jiangchao , Madia Mauro , Schurig Michael , Schlums Hartmut , Zerbst Uwe
Published: November 2022

Aero-engine turbine disks are safety-relevant components which are operated under high thermal and mechanical stress conditions. The actual part qualification and certification procedures make use of spin-tests conducted on production-similar disks. While these tests provide, on the one hand, a reliable definition of the critical conditions for real components, on the other hand they represent a relevant cost item for engine manufacturers. The aim of this work is to present part of a fracture mechanics-based procedure under development which aims at replacing the tests on production-similar disks with lab tests on fracture mechanics specimens. In particular, the rim-peeling failure mode is considered as case study. A semi-circular surface crack is modelled at the most stressed region at the diaphragm of a turbine disk, with the crack plane perpendicular to the radial direction. The crack is therefore subjected to a biaxial stress state and grows under increasing rotational speed until it triggers the rim-peeling failure. The finite element simulation of the cracked disk considers the real thermal and mechanical loading conditions. In order to design a lab representative specimen, beside the crack driving force, expressed in terms of J-integral, also the constraint to plastic deformation e.g., stress triaxiality, at the crack-tip must be similar for the same crack in the specimen and in the disk. This has been achieved and as expected, both the highest J-integral and constraint factor are calculated at the same location along the crack front for both disk and specimen. The results of the structural integrity assessment in the form of a Failure Assessment Diagram (FAD) show good agreement between designed specimen and disk both in terms of expected failure mode and value of the critical speed. Probabilistic aspects are also considered in the calculations.
Quantification of the Impact of the Crack Shape Constraint Assumption Onto Predicted Remaining Useful Life
Authors: Loghin Adrian
Published: November 2022

Today, different LEFM based reduced order modeling and 3D FEA based crack propagation life assessment tools are available to the end user. For a benchmark problem where solutions from different tools are compared, numerical variability can be observed [1]. One source of variability is related to the crack shape definition since reduced order models make use of elliptical representations during crack propagation modeling procedure while a 3D FEA based simulation can eliminate this shape constraint. Using a classical corner crack at a hole geometry, the impact of the crack front shape assumption on the computed remaining useful life is addressed. The same 3D FEA based explicit crack growth software application is used to obtain the two solutions and therefore limiting other sources of error in this comparison. The accuracy of the mode I stress intensity factor solution for initial crack and convergence of the fatigue crack growth solutions are also addressed since numerical error accumulation can impact the conclusion reached in the study.
Morton Effect Calculation and Analysis of Shop Test Results for Single-Shaft Multistage Centrifugal Compressors
Authors: Takahashi Naohiko , Magara Yohei , Hemmi Makoto , Sato Motoki
Published: November 2022

In the manufacturing process of single-shaft multistage centrifugal compressors for process gases, factory tests are conducted to confirm that the lateral vibration satisfies the allowable limits. One of the problems that must be taken care of during the test is the increase in vibration due to the Morton Effect. The Morton Effect is a thermal bending vibration caused by the non-uniformity of the oil film temperature of the bearing, and many troubles have been reported in overhung rotors. However, there are few reports of the Morton Effect in single-shaft multistage compressors. This is thought to be because even if the Morton Effect did occur, it was often only a minor problem. Although it is a minor problem, it is necessary to predict and evaluate the Morton Effect in order to prevent a prolonged test process and costly countermeasures. In this study, a calculation method for the Morton Effect has been developed for a single-shaft multistage centrifugal compressor, and an evaluation index for the Morton Effect is proposed. The developed method is verified and the validity of the proposed evaluation index of the Morton Effect is checked using cases of increased vibration that occurred in factory tests.
Condition Monitoring Insight Using Bayesian Inference and Rotor Dynamics Modelling for Rotating Machinery
Authors: Nelson Greg , Palmer Iain
Published: November 2022

Rotor dynamics modelling can be used to predict vibration levels for given inputs, such as unbalance levels and location, which may be of interest for condition monitoring or diagnosis. However, given measured vibration, using rotor dynamics models to find the corresponding root cause inputs is not straightforward.

In the method presented in this paper, Gaussian Process models are developed as surrogates for the rotor dynamics finite element models, and are used with Bayesian Inference to determine the probability distributions of model inputs for a given vibration response. This method allows parameters describing the machine condition, such as unbalance location and magnitude, and bearing clearances, to be determined as well as the confidence in these predictions.

The method is demonstrated by simulating the vibration response of a compressor rotor, adding noise to it, and then using the technique to accurately infer useful information such as the unbalance magnitude and location, and the clearance in each bearing.

This technique can be applied as a risk-based approach to condition monitoring of rotating machinery. Further development of this approach as part of a digital twin which uses in-service measurements would provide operators with insight into the likelihood of different root causes of vibration, and the corresponding machine condition.
Short-Time Creep Deformation of the Coarse-Grained Nickel-Base Alloy 247 and Its Implications on the High-Cycle Fatigue Behavior
Authors: Jordan Oliver , Lion Philipp , Beck Tilmann
Published: November 2022

Cast polycrystalline nickel-base superalloys are typically used for critical high temperature aerospace and automotive components, such as turbine blades or turbocharger wheels. These high temperature components can undergo creep damage caused by, e.g., centrifugal forces on the turbine rotor blades, as well as high-cycle fatigue (HCF) from, for instance, vibrations of the rotor blade. Therefore, both, creep resistance and fatigue strength, are important mechanical properties of these materials. The study presented here addresses the introduction of creep damage and its influence on the high-cycle fatigue behavior. For this purpose, fatigue specimens of coarse-grained Alloy 247 LC CC blade root material were pre-stressed on a pneumatic creep test rig to achieve creep-induced microstructural damage. The isothermal 900°C short-time creep investigations below 1000 h test duration were performed at different tensile stresses which result in different strain rates. After the creep tests, scanning electron- and light microscopy investigations of metallographic cross-sections of selected specimens were performed to determine the creep-induced grain boundary damage such as pore count, pore size, and coarsening of the γ′ structure. This was followed by uniaxial, stress-controlled isothermal 850°C high-cycle fatigue tests on undamaged and pre-damaged specimens at a frequency of 10 Hz and a load ratio of R = −1. Subsequently, fractographic and cross-section investigations, which provide information on the fatigue cracking, the failure initiating defects, and the pore morphology were performed. The results of this study show that the degree of creep induced porosity is a dominant structural parameter for the HCF behavior of the investigated nickel-base superalloy.
Feasibility Analysis of the Rotor Elastic Support With Piezoelectric Damping
Authors: Hu Yu , Li Lin , Wu Yaguang , Fan Yu
Published: November 2022

The squirrel cage is a widely-used elastic support in aeroengine. The combination of the squirrel cage and damping structures, such as squeeze film dampers, can effectively suppress rotor vibration. The squeeze film damper, although providing significant damping, requires a specific auxiliary lubricant supply system, which occupies space and brings additional weight. Piezoelectric materials have the advantages of light weight, high energy density, and wide bandwidth. The electromechanical coupling effect ensures that they can be used as energy transducers, and the corresponding piezoelectric damping has attracted extensive attention. In this study, we propose an elastic support-piezoelectric damper system for rotors by integrating the piezoelectric damping to the squirrel cage. The purpose of this study is to demonstrate the feasibility of the piezoelectric squirrel cage to suppress the vibration of the low pressure rotor of aero-engine from both the aspects of vibration and strength. To do that, the finite element model of a dummy rotor with elastic support-piezoelectric damper system is established first. The polarization direction and the network topology are optimized to reduce the amount of circuit impedance under the premise of ensuring the modal electromechanical coupling factor. An in-house code to simulate the dynamic performance of the rotor with the elastic support-piezoelectric damper system is developed in ANSYS/MATLAB environment. To reduce the computational cost, the following acceleration techniques are adopted: 1) the specific modal synthesis method dedicated to piezoelectric structures is implemented to reduce the dimension of the governing equations; 2) the equivalent linearization method is carried out to transfer the synchronized switch damping (SSD) with nonlinear nature to a frequency-dependent impedance, thus the time-consuming nonlinear solver is avoided. The unbalance response of the rotor is analyzed numerically. The damping effects of two promising piezoelectric damping technologies, i.e. the resonant damping and the SSD, are compared and discussed. Results show that the SSD network can reduce the vibration level of the rotor significantly with good robustness; the number of the SSD control circuit is only the half of the number of squirrel cage bars; the failure strength margin is sufficient.
Aerodynamic Damping of Composite UHBR Fans Under the Consideration of Acoustic Intake Reflections
Authors: Gößling Jan , Seume Joerg R. , Flüh Jan Peter , Paletta Nicola , Eggers Torben , Friedrichs Jens , Natale Nunzio
Published: November 2022

Steadily rising regulations and demands on aeroengines require the continuous reduction of CO2 emissions. Among other factors, particularly the weight reduction of the engine as well as synergetic engine-airframe integration are of major concern. Both lead to the application of shorter and more sensitive intakes as well as new materials, such as fiber composites. Fiber composites generally have a considerably lower density but a similar stiffness compared to common fan blade materials resulting in a reduction of the engines’ weight. A further difference from conventional materials is the anisotropic behavior of the stiffness, imposed by the ply orientation. In this paper, the impact of the use of fiber composites for the scaled rotor of an ultra-high bypass ratio (UHBR) fan on the aeroelasticity is investigated numerically. In order to influence the eigenfrequency and mode shape, the ply orientation of the blade lay-up is varied. The influence on the resulting aerodynamic damping is analyzed numerically, using a harmonic balance approach. For an accurate prediction, the aeroacoustic reflection at the intake highlight plane is incorporated in the numerical model and its impact is quantified for different intake lengths. The results are compared to a titanium alloy blade design (Ti-6Al-4V) and show the capability of varying the eigenfrequency with a coupled change in twist-to-plunge ratio due to lay-up variations. This change of the structural dynamics of the rotor blade influences the aerodynamic damping. Additionally, acoustic reflections are found to affect the stability, depending on the lay-up, operating condition, and intake length. A lay-up was found, which stabilizes the fan blade for all investigated conditions operating with a typical short ultra-high bypass ratio (UHBR) intake. A special lay-up generates negative aerodynamic damping of −6.6% (logarithmic decrement) when operated close to stall. This fulfills the present project’s particular need to measure flutter in a wind tunnel.
A Probabilistic Model for Forging Flaw Crack Nucleation Processes for Heavy Duty Gas Turbine Rotor Operations
Authors: Radaelli Francesco , Amann Christian , Aydin Ali , Varfolomeev Igor , Gumbsch Peter , Kadau Kai
Published: November 2022

We present a probabilistic model for quantifying the number of load cycles for nucleation of forging flaws — for a 3.5NiCrMoV high strength low alloy rotor steel — into a crack under gas turbine operating conditions. The model correlates low cycle fatigue data, ultrasonic testing indication data, flaw morphology, and type with the nucleation process. This paper is the third of a series of publications presenting this modeling approach progressively. It focuses on the effect of temperature variation on the nucleation life of forging flaws. We quantified the number of cycles to crack nucleation was for specimens that included forging flaws at elevated temperatures. Flaws of different sizes and shapes are effectively described at respective temperature and stress levels by either an ellipsoidal finite element model or an analytical area-based model. A local probabilistic low-cycle fatigue model analyzes the resulting stress distributions accounting for statistical size effects. Via Maximum Likelihood Estimation of these probabilistic low cycle fatigue results, a probabilistic model for crack nucleation of forging flaws is obtained. This proposed probabilistic model is based on experimental data for realistic heavy duty gas turbine rotor temperature and stress conditions. It can be utilized in the energy sector for component life time quantification. Our suggested approach can support component assessment under flexible gas turbines operation conditions driven by increased availability of intermittent renewable energy sources.
The Impact of Mistuning and Material Damping on Bladed Disks of Similar Geometries
Authors: Nix Jarred A. , Rodriguez Andres M. , Kauffman Jeffrey L.
Published: November 2022

As advances in turbomachinery manufacturing have continued to improve, integrally bladed rotors or blisks have become more prevalent due to the aerodynamic improvements that can be derived from those designs. Despite increases in efficiency, these blisks are prone to significantly higher vibrations due to the removal of friction damping that naturally occurs at the interfaces between each blade and the disk. Mistuning is characterized by a lack of symmetry due to the inevitable imperfections and non-homogeneity that arise across blades from manufacturing inaccuracies and use. Here we report on the frequency response functions of multiple tuned and mistuned academic blisks. The various blisks also exhibit different damping levels based on the material and thickness. These blisks were tested experimentally to determine how the different damping would affect the system response.
Stability Analysis of an Industrial Blade Accounting for a Blade-Tip/Casing Nonlinear Interface
Authors: Colaïtis Yann , Batailly Alain
Published: November 2022

This paper investigates the local stability analysis of periodic solutions corresponding to the nonlinear vibration response of an industrial compressor blade, NASA rotor 37, on which are applied different types of nonlinearities. These solutions are obtained using a harmonic balance method-based approach presented in a previous paper. It accounts for unilateral contact and dry friction of the rotating blade against a rigid casing through a regularized penalty law. A Lanczos filtering technique is also employed to mitigate spurious oscillations related to the Gibbs phenomenon thus enhancing the robustness of the solver. In addition, a component mode synthesis technique is used to reduce the dimension of the numerical model. Stability assessment of the computed solutions relies on Floquet theory. It is performed through the computation of the monodromy matrix as well as Hill’s method. Both methodologies are applied and thoroughly compared as the severity of the nonlinearity is gradually increased from a cubic spring to 3D contact conditions on a deformed casing. While the presented results underline the applicability of both stability assessment methodologies for all types of nonlinearities, they also put forward the much higher computational effort required when computing the monodromy matrix. Indeed, it is shown that Hill’s method yields converged results for significantly lower values of both the number of retained harmonics and the considered number of time steps thus making it a far more efficient method when dealing with industrial models. It is also underlined that the presented results are in excellent agreement with reference solution points obtained with time domain solution methods. Specific implementation tweaks that were found to be of critical importance in order to efficiently assess the stability of computed solutions are also detailed in order to provide a comprehensive view of the challenges inherent to such numerical developments.
Probabilistic Assessment of Gas Turbine Compressor Blade HCF Life
Authors: Meng Zhiqiang , Krishnababu Senthil , Jackson Simon , Sjödin Björn
Published: November 2022

This paper uses a novel and practical probabilistic approach to assess the risk of a compressor blade HCF failure in the gas turbine. For a specific design case, the tip timing tests for a newly designed gas turbine compressor blade successfully passed HCF design criteria during engine operation when operated over a wide speed range. However, on a later test high amplitude responses were seen under a VGV configuration which was different from that used during normal operation.

Firstly, the gas turbine operational data and blade bench test data are used by the probabilistic assessment to identify the characteristics of the HCF problem. The resonance counting is carried out by the Monte Carlo simulations. The simulation indicates that the HCF endurance limit for the alternating stress is required to be satisfied for this blade.

Secondly, the material test data, blade tip timing data and finite element (FE) results are used to build a HCF endurance stress probabilistic model, following which the probability of blade HCF failure was estimated. The Monte Carlo simulations are used for the probabilistic model. The simulation results show that the probability of HCF failure per blade and the risk of HCF failure for any blade of the stage are very small and acceptable.
Experimental Modal Analysis of a Full-Scale Rotating Fan
Authors: Jorajuria Corentin , Gibert Claude , Thouverez Fabrice , Esteves Cécile
Published: November 2022

Experimental modal analysis of a full-scale aeronautic fan is performed at design rotating speed and under vacuum conditions. The composite woven fan is excited through embedded piezoelectric actuators and the dynamic response of the system is measured with strain gauges. Presented experiments achieve high quality data measurements of forced responses thanks to a strict control of experimental conditions, an extended instrumentation of the fan and a careful testing method. The study focuses on the two first bending mode families with nodal diameters. The modal testing of the system is performed using frequency stepped sine excitations over a close range around investigated resonances and using travelling wave excitations allowing to investigate specific nodal diameter modes in each family. The forced response measurements are used to estimate the frequency response functions of the rotating fan under different experimental parameters. In particular, the first mode family exhibits a higher modal density which is challenging for modal parameters estimations. Used frequency domain modal identification techniques are presented and adapted to the fitting of frequency response functions. At the end, these techniques are applied to investigate sensitivity of extracted natural frequencies and modal damping ratios with respect to different parameters such as rotational speed, excitation level and nodal diameter content of the excitation pattern.
Research on the Nonlinear Behavior of the Turbine Rotor Assembled by Rabbet Joints
Authors: Han Zhuoluo , Li Yifeng , Wang Yongfeng , Hong Jie
Published: November 2022

Double-stage turbine rotor assembled by rabbet joints is widely used in aero-engine, the mechanical properties of which depends highly on the compression state of the joints’ contact interfaces. The accumulated damages during operation lead to the deterioration of the contact state, which could cause the sliding or partial separation on the interface, and will affect the dynamic characteristics of the rotor system. In this paper, the static mechanical properties, mainly angular stiffness, were studied using the static contact Finite Element Analysis (FEA) method to reveal the nonlinear variation in different conditions. One dynamic model of the rotor with rabbet joints was built based on the Lagrange equations, which was numerically solved by the Runge-Kutta method for the dynamic response of the rotor with nonlinear stiffness. The results show that the rabbet joints stiffness nonlinearity will decrease the critical speed of the flexural mode and cause amplitude sudden jump phenomena during acceleration or deceleration. Moreover, the chaotic motion and impact dynamic response may appear in the vicinity of the flexural mode critical speed. The axial preload is an essential influencing factor affecting the nonlinear response characteristics of the flexural mode, and an adequate preload will minimize or prevent the effects of stiffness nonlinearity during operation.
Efficient Forced Response Analysis for Asymmetric Vane Spacing
Authors: Geihe Benedict , Frey Christian , Ashcroft Graham
Published: November 2022

In the context of forced response analysis, we present a computationally efficient method to capture the effect of inflow distortions caused by intentional variation of cyclic vane spacing. Applying such configurations is a typical mitigation strategy when unforeseen critical blade vibrations occur due to synchronous excitation by wakes of an upstream row. Altering the circumferential distance in a section-wise pattern effectively distributes the fluctuations among several engine order frequencies, thereby reducing their amplitudes. The rotationally asymmetric configurations initially call for multi-passage simulations. We show that the circumferential spectrum can be well approximated using single passage results only, without significant additional costs. Our approach is based on an analytically computed Fourier transform of a synthesis functional. For validation, we consider a turbine test case with transonic and subsonic operating points. We determine the reduction in amplitude of dominant inflow modes for an explicitly constructed instance with asymmetric vane spacing and compare our analytical predictions to full-wheel simulations. Furthermore we assess the impact on aerodynamic excitation of downstream rotor blades using both a frequency and a time domain solver.
Measured and Predicted Temperature Differentials Within a Rotor at a Tilting-Pad-Journal Bearing Associated With the Morton Effect
Authors: Kulhanek Chris D. , Cunningham Seth , Delgado Hector A. , Moore Jeff , Hollingsworth Justin R.
Published: November 2022

The current work shows the implementation of a high-speed turbomachinery test rig to measure vibration and internal shaft temperature differentials at a journal bearing for a rotor system designed to induce the Morton effect rotordynamic phenomenon. The vibration and shaft temperature measurements are compared to predictions using an analytical code described by Tong and Palazzolo [6,7]. An existing high-speed test rig was adapted, including a new rotor with six equally-spaced RTDs embedded at the journal bearing centerline. The rotor configuration included an overhung rotor design with a 58 mm (2.3 inch) diameter, 5-pad tilting-pad journal bearing. The in-rotor temperature measurements were conditioned using a custom on-board amplifier and extracted with a high-speed commercial slip ring. Test conditions included various levels of unbalance, bearing oil inlet temperature, and operating speed. Test measurements show that the temperature differential across the shaft is dependent upon operating speed, as well as vibration amplitude. Operating conditions included rotational speeds up to 19.5 krpm and vibration levels approaching the magnitude of the bearing clearance. Testing near the rotor first lateral natural frequency (or critical speed) with a high level of initial unbalance resulted in the highest temperature differentials across the shaft of approximately 11 °C (20 °F) plus. Vibration measurements show hysteresis in the synchronous vibration response in the Bode and polar plots. This measured vibration hysteresis is consistent with the rotor hot spot or temperature differential changing the unbalance level of the rotor. Overall, both the test measurements and predictions show notable temperature differentials and hysteresis behavior in the vibration response that are believed to be associated with the Morton Effect. These conditions are considered precursors to the spiral vibration or fully developed synchronous instability typically associated with the Morton Effect.