Volume 9B: Structures and Dynamics — Fatigue, Fracture, and Life Prediction; Probabilistic Methods; Rotordynamics; Structural Mechanics and Vibration最新文献

{"title":"Experimental and Analytical Investigation of Cyclic Crack Initiation in Nickel Based Super Alloy With Stress Concentration Features","authors":"Alex Torkaman, S. Fiebiger, Nathan O’Nora, Devin O’Neal, A. Gordon","doi":"10.1115/gt2021-59608","DOIUrl":"https://doi.org/10.1115/gt2021-59608","url":null,"abstract":"\u0000 Accurate prediction of cycles to crack initiation in critical turbine components is a major issue in turbomachinery design, especially in components with highly concentrated stress such as turbine blades with cooling holes. Several viscoplastic and lifing methods have been used successfully to predict shakedown and cycles to failure, however complicating factors still exist that produce challenges for traditional methods. Therefore newer methods utilizing constitutive modeling with consideration for isotropic and polytropic hardening have been developed to better capture evolution of cyclic behavior of the material. Presence of mean stress and stress concentration factors are some of the complications that can be better accounted for using constitutive models. The present paper evaluates experimental and theoretical life of specimen made from nickel based super alloy with high stress concentration features under cyclic conditions with mean stress. The specimen geometry and loading were designed to mimic trailing edge holes in an F class IGT turbine blade. Experiments were conducted at an elevated temperature at two peak stress values to determine sensitivity to applied load at operating temperature similar to engine. Cycles to crack initiation are analytically evaluated using the well-known Manson-Coffin method with Morrow mean stress correction and two distinct methods for strain range evaluation. First method is the traditional Ramberg Osgood shakedown that has been extensively used in the industry. Second method is constitutive Chaboche based model run with linearized FEM results. Constants for Chaboche model are determined from Ramberg-Osgood constants with a method that takes into account yield surface evolution and hardening constants, in addition to rate dependent stress relaxation factor that can be used to model dwell time effects. Methods to decrease computational time with constitutive model are discussed. Analytical results are compared with the experimental data, and advantages and disadvantages of both methods including computational times are discussed.","PeriodicalId":143309,"journal":{"name":"Volume 9B: Structures and Dynamics — Fatigue, Fracture, and Life Prediction; Probabilistic Methods; Rotordynamics; Structural Mechanics and Vibration","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131072782","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Calculation of Nonlinear Systems Under Narrow Band Excitation Using Equivalent Linearization and Path Continuation","authors":"Alwin Förster, L. P. Scheidt","doi":"10.1115/gt2021-58437","DOIUrl":"https://doi.org/10.1115/gt2021-58437","url":null,"abstract":"\u0000 Turbomachines experience a wide range of different types of excitation during operation. On the structural mechanics side, periodic or even harmonic excitations are usually assumed. For this type of excitation there are a variety of methods, both for linear and nonlinear systems. Stochastic excitation, whether in the form of Gaussian white noise or narrow band excitation, is rarely considered. As in the deterministic case, the calculations of the vibrational behavior due to stochastic excitations are even more complicated by nonlinearities, which can either be unintentionally present in the system or can be used intentionally for vibration mitigation. Regardless the origin of the nonlinearity, there are some methods in the literature, which are suitable for the calculation of the vibration response of nonlinear systems under random excitation. In this paper, the method of equivalent linearization is used to determine a linear equivalent system, whose response can be calculated instead of the one of the nonlinear system. The method is applied to different multi-degree of freedom nonlinear systems that experience narrow band random excitation, including an academic turbine blade model. In order to identify multiple and possibly ambiguous solutions, an efficient procedure is shown to integrate the mentioned method into a path continuation scheme. With this approach, it is possible to track jump phenomena or the influence of parameter variations even in case of narrow band excitation. The results of the performed calculations are the stochastic moments, i.e. mean value and variance.","PeriodicalId":143309,"journal":{"name":"Volume 9B: Structures and Dynamics — Fatigue, Fracture, and Life Prediction; Probabilistic Methods; Rotordynamics; Structural Mechanics and Vibration","volume":"68 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131360754","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Structural Integrity of Serrated Leading Edge Guide Vane Blades for Noise Reduction","authors":"Cleopatra Cuciumita, N. Qin, Felix Stanley, S. Shahpar","doi":"10.1115/gt2021-58747","DOIUrl":"https://doi.org/10.1115/gt2021-58747","url":null,"abstract":"\u0000 One of the major noise sources of high bypass ratios modern turbofan engines arises from the interaction between the turbulent rotor wake, the tip-leakage and the leading edge of the downstream outlet guide vanes. Recent research has confirmed that leading edge serrations are an effective passive control for reducing noise. However, for transferring serrated leading edges to modern, environmentally friendly aero engines, the bypass outlet guide vanes must fulfil both aerodynamic and structural requirements. The current study aims at characterizing the structural behaviour when adding serrations to the leading edge of bypass outlet guide vanes designed for a configuration without classical struts.\u0000 It was found that the structural performances deteriorate with increasing number of serrations, directly related to the serrations wavelength, and with their amplitude. The buckling loading factor decreases and the total deformation increases constantly with the increase of both parameters. The presence of the troughs of the serrations introduce stress concentrators. For large enough values of either the wave length or amplitude of the serrations, the maximum von Mises stress increases significantly, and can as much as double in value. At the same time, the location of the maximum stress on the vane moves from its original position, on the leading edge of the casing fillet, to the troughs of the serrations.","PeriodicalId":143309,"journal":{"name":"Volume 9B: Structures and Dynamics — Fatigue, Fracture, and Life Prediction; Probabilistic Methods; Rotordynamics; Structural Mechanics and Vibration","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126873053","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On the Creep-Fatigue Design of Double Skin Transpiration Cooled Components Towards Hotter Turbine Cycle Temperatures","authors":"C. Skamniotis, A. Cocks","doi":"10.1115/gt2021-58836","DOIUrl":"https://doi.org/10.1115/gt2021-58836","url":null,"abstract":"\u0000 The need for better aeroengine efficiency and fuel burn savings can be addressed by increasing turbine cycle temperatures. New cooling technologies such as emerging double skin transpiration (DST) systems, are essential for preserving the integrity of metallic parts if operating temperatures are to be increased beyond current levels. Their implementation, however, requires complex architectures with detailed features such as inclined film holes that raise local stresses. Our aim is to accelerate the implementation of DST systems in turbomachines, by providing an understanding of their implications on thermal stresses and the creep-fatigue failure processes. By using geometric, temperature field and nickel alloy material property idealizations, we generate both theoretical and Finite Element (FE) solutions for the thermal stress field and the critical cyclic strain range. Theoretical stress analysis and a local approach to failure lead to life predictions that are in reasonable agreement with inelastic cycle-by-cycle FE analysis, suggesting that analytical approaches can be useful for immediately identifying the significance of the various geometric features and thermal loading parameters. Film hole locations are predicted to fail under low cycle fatigue, suggesting that optimizing hole inclination, hole shape and other important geometric features is critical.","PeriodicalId":143309,"journal":{"name":"Volume 9B: Structures and Dynamics — Fatigue, Fracture, and Life Prediction; Probabilistic Methods; Rotordynamics; Structural Mechanics and Vibration","volume":"20 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131859147","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Full-Scale Vibration Testing of Nozzle Guide Vanes","authors":"G. Macoretta, B. Monelli, P. Neri, F. Bucciarelli, D. Checcacci, Enrico Giusti","doi":"10.1115/gt2021-59356","DOIUrl":"https://doi.org/10.1115/gt2021-59356","url":null,"abstract":"\u0000 An increasing number of turboexpanders are equipped with Nozzle Guide Vane (NGV) as the first stator stage. By varying the throat area of the first stator vane the NGV enables an additional control methodology to the line-up power output allowing higher operational flexibility and higher efficiency at partial load and partial speed. The design of this component might become critical for enabling high expander availability considering its exposure to high temperature, thermal loading, and fluid induced vibrations. This is especially true also considering that the vibration frequencies of this sub-assembly are influenced by internal clearances and by the value of the friction coefficient, which leaves a relevant margin of error when using numerical methods (such as FEM) for predicting the actual structural behavior of this component. In this paper, the design of a full-scale test bench for the determination of both friction coefficients and modal behavior of a nozzle guide vane geometry is described. The bench enables us to simulate the pre-load due to aerodynamic forces on the NGV airfoil simulating the actual working conditions of bushes and bearings.","PeriodicalId":143309,"journal":{"name":"Volume 9B: Structures and Dynamics — Fatigue, Fracture, and Life Prediction; Probabilistic Methods; Rotordynamics; Structural Mechanics and Vibration","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129180858","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"System Level Analysis of Compressor Eye-Labyrinth Seal Rotordynamic Forces: A Computational Fluid Dynamics Approach","authors":"Shujan Ali, Farzam Mortazavi, A. Palazzolo","doi":"10.1115/gt2021-59725","DOIUrl":"https://doi.org/10.1115/gt2021-59725","url":null,"abstract":"\u0000 Accurate characterization of compressor rotordynamic coefficients during the design phase reduces the risk of sub-synchronous vibration (SSV) problems occurring in the field. Although rotordynamists extensively investigate discrete compressor components (such as seals and front shrouds) to tackle instability issues, integrated or system-level analysis of compressor rotordynamics is rare. In reality, the impeller, eye labyrinth seal, and the front shroud heavily influence one another; and the collective dynamic behavior of the system differs from the sum of the dynamic behavior of isolated components.\u0000 To further investigate, a CFD-based approach is taken to evaluate the dynamic behavior of the system as a whole. The geometry and operating conditions in this work are based on the recent experimental study of Song et al. (2019) on compressor seal and front shroud stiffness values. The compressor impeller is redesigned utilizing turbomachinery design software CFturbo. The commercial CFD code CFX 19.0 is used to resolve Reynolds Averaged Navier-Stokes (RANS) equations to quantify eye labyrinth seal and front cavity stiffness, damping, and added mass, while the whole compressor stage is modeled to uncover the coupled behavior of the components, and assess the stability of the whole system instead of any discrete components. The coupled system is constructed by modeling the interacting upstream and downstream components to accurately capture key rotordynamic parameters such as damping, axial pressure, and pressure distribution evolution inside the cavities. Effect of turbulence is captured utilizing the shear stress transport (SST) k-ω model. In the current work, three CFD approaches, namely quasi-steady, transient static eccentric, and transient mesh deformation technique are tested, and predictions are made on stiffness, damping, and virtual mass. Effectiveness of each CFD method is evaluated by comparison with the experimental data. CFD results provide the non-axisymmetric pressure perturbation for the shroud and seal surfaces. Furthermore, rotordynamic coefficients are derived utilizing correlations from the literature, and compared with CFD based and experimental results.","PeriodicalId":143309,"journal":{"name":"Volume 9B: Structures and Dynamics — Fatigue, Fracture, and Life Prediction; Probabilistic Methods; Rotordynamics; Structural Mechanics and Vibration","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123704095","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Reduced Order Modeling Approach to Probabilistic Creep-Damage Predictions in Finite Element Analysis","authors":"Abir Hossain, Jacqueline R. Cottingham, C. Stewart","doi":"10.1115/gt2021-58480","DOIUrl":"https://doi.org/10.1115/gt2021-58480","url":null,"abstract":"\u0000 This paper introduces a computationally efficient Reduced Order Modeling (ROM) approach for the probabilistic prediction of creep-damage failure. Component-level probabilistic simulations are needed to assess the reliability and safety of high-temperature components. Full-scale probabilistic creep-damage modeling in finite element (FE) approach is computationally expensive requiring many hundreds of simulations to replicate the uncertainty of component failure. To that end, ROM is proposed to minimize the elevated computational cost while controlling the loss of accuracy. It is proposed that full-scale probabilistic simulations can be completed in 1D at a reduced cost, the extremum conditions extracted, and those conditions applied for lower cost 2D/3D probabilistic simulations of components that capture the mean and uncertainty of failure. The probabilistic Sine-hyperbolic (Sinh) model is selected which in previous work was calibrated to alloy 304 stainless steel. The Sinh model includes probability density functions (pdfs) for test condition (stress and temperature), initial damage (i.e., microstructure), and material properties uncertainty. The Sinh model is programmed into ANSYS finite element software using the USERCREEP.F material subroutine. First, the Sinh model and FE code are subject to verification and validation to affirm the accuracy of the simulations. Numerous Monte Carlo simulations are executed in a 1D model to generate probabilistic creep deformation, damage, and rupture data. This data is analyzed and the probabilistic parameters corresponding to extreme creep response are extracted. The ROM concept is applied where only the extreme conditions are applied in the 2D probabilistic prediction of a component. The probabilistic predictions between the 1D and 2D model is compared to assess ROM for creep. The accuracy of the probabilistic prediction employing the ROM approach will potentially reduce the time and cost of simulating complex engineering systems. Future studies will introduce multi-stage Sinh, stochasticity, and spatial uncertainty for improved prediction.","PeriodicalId":143309,"journal":{"name":"Volume 9B: Structures and Dynamics — Fatigue, Fracture, and Life Prediction; Probabilistic Methods; Rotordynamics; Structural Mechanics and Vibration","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125873961","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Novel Vibration-Based Fault Detection Approach of Bolted Engineering Structures Without Reference","authors":"Quankun Li, Zengde Shao, Mingfu Liao","doi":"10.1115/gt2021-58493","DOIUrl":"https://doi.org/10.1115/gt2021-58493","url":null,"abstract":"\u0000 Because of some advantages such as low cost, detachability and reusability, bolted joints are widely applied in various open beam-like engineering structures like steel beams and train rails and closed ring-type engineering structures like steel frames and oil pipelines to keep different structural components together. However, bolted engineering structures often encounter vibration-induced joint faults like self-loosening, crack, leakage and corrosion since they are generally subjected to external dynamic loads caused by vibration environments. Joint damages would seriously affect structures’ reliability and durability, and increase maintenance costs. Therefore, fault detection of bolted engineering structures is very important and necessary. For beam-like and ring-type engineering structures with single excitation and multiple damaged bolted joints, various methods monitoring changes in nonlinear structural features have been developed. To avoid the use of structural features from benchmark structures for reference during the derivation of damage indicators, a novel vibration-based fault detection approach utilizing features from damaged structures only is proposed in this study. In the new method, the dynamic model of bolted engineering structures is simplified as a general MDOF model with nonlinear elements simulating nonlinear bolt loosening faults. By changing the value of related mass, three similar equations from the damaged structure are used to form one matrix, and then the singularity of matrix is used to detect the existence and position of faults. Results from simulations on the beam-like and ring-type models with multiple damages demonstrate that the proposed approach could be an effective tool to estimate the state of bolted engineering structures.","PeriodicalId":143309,"journal":{"name":"Volume 9B: Structures and Dynamics — Fatigue, Fracture, and Life Prediction; Probabilistic Methods; Rotordynamics; Structural Mechanics and Vibration","volume":"147 12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129907591","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dynamic Characteristics Analysis of Flexible Rotor System With Pedestal Looseness","authors":"Jie Hong, Qiyao Dai, Fayong Wu, Yanhong Ma","doi":"10.1115/gt2021-60195","DOIUrl":"https://doi.org/10.1115/gt2021-60195","url":null,"abstract":"\u0000 Due to the limitation of assembly conditions and working load environment, the design of pedestal looseness is often used in the structural design of aeroengine multi support flexible rotor, which affects the vibration response and stability of the rotor system. In this paper, a dynamic model of a flexible rotor system with pedestal looseness is established for a practical aeroengine flexible rotor system. Next, a nonlinear modal analysis process for the multi degree of freedom nonlinear rotor system is proposed. Based on this, the nonlinear modal characteristics of the flexible rotor system with pedestal looseness are analyzed. An interval prediction method of modal damping interval for stability analysis of rotor system is presented, and the influence of key characteristic parameters on modal damping and vibration stability of rotor system is explored. Finally, the vibration characteristics of the rotor system are obtained by numerical integration method. The results show that the modal characteristics of the rotor vary with the amplitude of the rotor, and have the feature of interval distribution; vibration stability mainly depends on tangential friction and additional lateral constraint; when the amplitude of the rotor is large, the backward whirling motion may occur and the vibration may be unstable. This paper will provide a theoretical method for dynamic optimization of multi support flexible rotor system, which is helpful to ensure the reliability and safety design of aeroengine.","PeriodicalId":143309,"journal":{"name":"Volume 9B: Structures and Dynamics — Fatigue, Fracture, and Life Prediction; Probabilistic Methods; Rotordynamics; Structural Mechanics and Vibration","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133353751","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rotor-Blade Interaction During Blade Resonance Drive-Through","authors":"R. Grein, Ulrich Ehehalt, C. Siewert, N. Kill","doi":"10.1115/gt2021-59160","DOIUrl":"https://doi.org/10.1115/gt2021-59160","url":null,"abstract":"\u0000 In the future energy landscape, combined cycle power plants will increasingly take the role of providing balancing power for fluctuating renewable energy sources due to their high availability and fast start-up times. This implies more frequent cycling, a larger number of speed cycles and thus new challenges for plant design and operation. One of these challenges is a potential increase of cyclic fatigue incurred by last-stage blades during start-up and coast-down. Blade vibrations might be induced by synchronous shaft vibrations when the blade resonance is excited by lateral shaft vibrations. In this paper, we report measurement results of shaft and blade vibrations observed at some Siemens Energy steam turbines. Apart from the expected increase of blade vibrations when the double rotating speed crosses the blade resonance, a distinctive dip of shaft vibrations at the low-pressure turbine bearings is observed. We argue that this phenomenon is likely related to the aforementioned interaction between blade and shaft vibrations and present a theoretical framework to describe this interaction and the observed effect.","PeriodicalId":143309,"journal":{"name":"Volume 9B: Structures and Dynamics — Fatigue, Fracture, and Life Prediction; Probabilistic Methods; Rotordynamics; Structural Mechanics and Vibration","volume":"106 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115374126","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}