On the Divergence Mechanisms Analysis of a Vibrating Blade subjected to Repetitive Rubs with an Abradable Coating

2021 ◽  
pp. 1-29
Author(s):  
Fabien Goldspiegel ◽  
Gérald Portemont ◽  
Julien Berthe
Keyword(s):  
Structural Integrity ◽  
Vertical Motion ◽  
Rotating Cylinder ◽  
Vibration Modes ◽  
Abradable Coating ◽  
Synchronization Mechanisms ◽  
Set Up ◽  
Being Moved ◽  
Blade Coating

Abstract Aeronautical compressor fans currently operate with minimal blade-casing clearance. This therefore makes the occurrence of rub events very likely. Under specific circumstances, the blade undergoes excessive amplification of contact-induced oscillations, called hereafter divergence, which can be critical for the structural integrity of the engine. This paper proposes an investigation of the mechanisms responsible for the blade divergence. Experiments are conducted on a fully instrumented laboratory set-up, consisting of a single flat blade being moved towards a rotating cylinder to initiate interactions, while monitoring the vibrations and the evolution of wear on the abradable coating. Two synchronization mechanisms have been identified as facilitating the divergence: (i) the inherent set-up synchronization between the vibration modes related to the horizontal and vertical motion of the blade; (ii) the preferential blade-coating interactions in the vicinity of periodically distributed irregularities of the abradable coating which act as a source of excitation of the vibrations.

scholarly journals Conjectural Bifurcation Analysis of an Aircraft Engine Blade Undergoing 3D Unilateral Contact Constraints

2014 ◽  
Author(s):  
Alain Batailly ◽  
Mathias Legrand
Keyword(s):  
Spline Interpolation ◽  
Sudden Change ◽  
Aircraft Engine ◽  
Rotational Frequency ◽  
Compressor Blade ◽  
Structural Behaviour ◽  
Mode Decomposition ◽  
Abradable Coating ◽  
Set Up ◽  
Pressure Compressor

Prediction of rotor/stator interaction phenomena between a blade-tip and the surrounding abradable coating deposited on the casing has seen recent promising numerical developments that revealed consistency with several experimental set-up. In particular, the location of critical rotational frequencies, damaged blade areas as well as the wear pattern along the casing circumference were accurately predicted for an interaction scenario involving a low-pressure compressor blade and the surrounding abradable coating deposited on a perfectly rigid casing. The structural behaviour of the blade in the vicinity of a critical rotational frequency however remains unclear as brutal amplitude variations observed experimentally could not be numerically captured without assuming contact loss or an improbable drastic and sudden change of the abradable coating mechanical properties during the interaction. In this paper, attention is paid to the structural behaviour of a high-pressure compressor blade at the neighbourhood of a critical rotational frequency. The interaction scenarios for two close rotational frequencies: Ωc and Ωc* are analyzed using empirical mode decomposition based on an adjusted B-spline interpolation of the time responses. The obtained results are compared to the interaction scenario dictated by the abradable coating removal history and the location of contact areas. The unstable nature of the blade vibratory response when the rotational frequency exceeds a critical rotational frequency is underlined and a plausible scenario arises for explaining a sudden and significant decrease of the blade amplitude of vibration without contact separation.

Analysis of the Leakage-Flow-Induced Vibration of a Slip Joint in a Jet Pump of a Boiling Water Reactor

2019 ◽  
Vol 390 ◽  
pp. 23-31 ◽  
Author(s):  
J. Cruz Castro ◽  
E. Hernández Palafox ◽  
I.A. Alarcón Sánchez ◽  
Luis H. Hernández-Gómez ◽  
Pablo Ruiz-López ◽  
...  
Keyword(s):  
Structural Integrity ◽  
Natural Frequencies ◽  
Excitation Frequency ◽  
Vibration Modes ◽  
The Finite Element Method ◽  
Jet Pump ◽  
Flow Induced Vibration ◽  
Ansys Fluent ◽  
Pump Assembly ◽  
Fourth Mode

The purpose of this analysis is to evaluate the structural integrity of the jet pump assembly of a BWR during the performance of its operational and safety functions. The natural frequencies and vibration modes of the jet pump assembly immersed in water were determined. It was observed that the fourth mode shape was torsional, and its associated resonance frequency was 41.82 Hz. Also, the vibration induced by the flow in the leakage of the slip joint was analyzed with an axisymmetric model. The gap of the slip joint was varied from 0.2 mm until 0.65bmm. A gap between 0.6 and 0.64, would cause flow-induced vibration because this excitation frequency matches with the fourth natural frequency of the jet pump assembly. The above was carried out using computational fluid dynamics, as well as the finite element method, with ANSYS Structural and ANSYS Fluent codes.

Sloshing Characteristics of Single Deck Floating Roofs in Aboveground Storage Tanks: Natural Periods and Vibration Modes

2009 ◽  
Author(s):  
Shoichi Yoshida ◽  
Kazuyoshi Sekine ◽  
Katsuki Iwata
Keyword(s):  
Structural Integrity ◽  
Oil Refining ◽  
Vibration Modes ◽  
Storage Tanks ◽  
Severe Damage ◽  
Element Analysis ◽  
Linear Elastic ◽  
Oil Storage ◽  
Hydrodynamic Coupling ◽  
Roof Design

The floating roofs are widely used to prevent evaporation of content in large oil storage tanks. The 2003 Tokachi-Oki earthquake caused severe damage to the floating roofs due to liquid sloshing. The structural integrity of the floating roofs for the sloshing is urgent issue to establish in the petrochemical and oil refining industries. This paper presents the sloshing characteristics of the single deck floating roofs in cylindrical storage tanks. The hydrodynamic coupling of fluid and floating roof is taken into consideration in the axisymmetric finite element analysis. It is assumed that the fluid is incompressible and inviscid, and the floating roof is linear elastic while the sidewall and the bottom are rigid. The basic vibration characteristics, natural periods and vibration modes, of the floating roof due to the sloshing are investigated. These will give engineers important information on the floating roof design.

Humans Jumping on Flexible Structures: Effect of Structural Properties

Volume 2 ◽  
2004 ◽  
Author(s):  
ShiPing Yao ◽  
Robert E. Harrison ◽  
Jan R. Wright ◽  
Aleksandar Pavic ◽  
Paul Reynolds
Keyword(s):  
Structural Integrity ◽  
Damping Ratio ◽  
Flexible Structures ◽  
Vertical Motion ◽  
Drop Out ◽  
Mass Ratio ◽  
Test Rig ◽  
Near Resonance ◽  
The Subject ◽  
Force Drop

The behaviour of humans jumping on flexible structures has become a matter of some importance for both structural integrity and also human tolerance. The issue is of great interest for stadia, footbridge and floor structures. A test rig has been developed for exploring the forces, accelerations and displacements that occur when a human subject jumps on a flexible structure where motion can be perceived. In tests reported earlier, it was found that the human is able to generate near resonant response of the structure but it was extremely difficult, if not impossible, to jump at or very near to the natural frequency of the structure when the structural vertical motion is significant. Also, the force developed by the subject was found to drop significantly near resonance. In this paper, the effect of the subject-to-structure mass ratio and the damping ratio of the structure on the ability of the subject to jump near resonance, and on the force drop out, is presented. It is shown that as the structure becomes more massive and more highly damped it moves less for nominally the same jumping excitation. In this situation, it becomes easier to jump near resonance and the degree of force drop out reduces, though it is still significant.

Analysis of Non-Uniformly Degraded Pipe Sections

2003 ◽  
Author(s):  
Amy J. Smith ◽  
Keshab K. Dwivedy
Keyword(s):  
Wall Thickness ◽  
Nuclear Power ◽  
Power Plants ◽  
Structural Integrity ◽  
Operating Cycle ◽  
Moment Capacity ◽  
Asme Code ◽  
Uniform Cross Section ◽  
Uniform Wall ◽  
Set Up

The management of flow assisted corrosion (FAC) has been a part of the maintenance of piping in nuclear power plants for more than 15 years. Programs have been set up to identify vulnerable locations, perform inspections, characterize the degraded configurations, and evaluate the structural integrity of the degraded sections. The section of the pipe is repaired or replaced if the structural integrity cannot be established for the projected degraded section at the next outage. During the past 15 years, significant improvements have been made to every aspect of the program including structural integrity evaluation. Simplified methods and rules are established in ASME Section XI code and in several code cases for verifying structural integrity. The evaluation of structural integrity is performed during the plant outage prior to a decision for repair or replacement. Any improvement in structural integrity evaluation to extend the life of a component by one additional operating cycle can help in performance of repair/replacement of component in a planned manner. Simplified methods and rules provided in the code can be easily used for analysis of pipe sections with degraded area with uniform wall thickness and for non-uniformly degraded sections, provided the degraded portions are modeled with uniform wall thickness equal to the lowest thickness of the section. The representation of a non-uniformly degraded section in this manner is necessarily conservative. The purpose of this paper is to develop methodology to analyze the non-uniformly degraded sections subjected to pressure and moment loading by modeling it in a manner that accounts for the non-uniform cross-section. The formulation developed here is more realistic than the code methodology and is still conservative. The results are presented in form of charts comparing the limit moment capacity of the degraded sections calculated by the formulation in this paper with that using ASME code formulation. The paper concludes that the proposed formulation can be used to supplement the ASME Code method to extend the remaining life of FAC degraded components.

Mura di Roma dalla Porta Latina all'Appia

2008 ◽  
Vol 76 ◽  
pp. 99-154
Author(s):  
Lucos Cozza
Keyword(s):  
Structural Integrity ◽  
Direct Link ◽  
Construction Techniques ◽  
Set Up ◽  
The Individual ◽  
Coats Of Arms

The stretch of the Aurelianic Walls from the Porta Latina to the Porta Appia comprises twelve towers linked bv curtain walls with covered walkways. The surviving state of the monument is described in detail. The individual phases (from AD 275 to the present) are distinguished through the analysis of their construction techniques, archive drawings and photographs of vanished sections, papal coats of arms, and inscriptions (in pencil or graffito) recording more recent events. When the entire circuit was doubled in height during the Honorian phase (AD 401–3), the floors of the towers were built at a considerably higher level than the rampart walkways, so as to exploit fully the type of siege machinery(halhstae)located in the towers' upper chambers. The Honorian loopholes, for the use of archers, reveal a long and complex history: undergoing modifications during construction, they were subsequently blocked to prevent the illegal traffic of goods (and the avoidance of customs dues), and were finally reopened and modified once again for the defence of papal Rome. The modern restorations of 1930–67 are examined critically. The need for immediate restoration and sustained maintenance to guarantee the monument's structural integrity is now clear. It is to be hoped that a direct link (with visitor access) will be provided with the ‘Museo delle Mura’, which was set up in the neighbouring Porta Appia in 1970.

JSME Construction Standard for Superconducting Magnet of Fusion Facility: “General View of the Code”

2009 ◽  
Author(s):  
Yuji Nakasone ◽  
Yukio Takahashi ◽  
Arata Nishimura ◽  
Tetsuya Suzuki ◽  
Hirosada Irie ◽  
...  
Keyword(s):  
Structural Design ◽  
Radiation Effects ◽  
Structural Integrity ◽  
Superconducting Magnets ◽  
Fusion Energy ◽  
Superconducting Magnet ◽  
General View ◽  
Deformation Control ◽  
Roles And Responsibilities ◽  
Set Up

The Japan Society of Mechanical Engineers (JSME) has set up and published the construction standard for superconducting magnet structures to be used in nuclear fusion facilities. The present target of the standard is tokamak-type fusion energy facilities, especially the International Thermonuclear Experimental Reactor called ITER for short. The standard contains rules for structural materials including cryogenic materials, structural design considering magnetic forces, manufacture including welding and installation, nondestructive testing, pressure proof tests and leak tests of toroidal field magnet structures. The standard covers requirements for structural integrity, deformation control, and leak tightness of all the components of the superconducting magnets and their supports except for superconducting strands and electrical insulators. The standard does not cover deterioration which may occur in service as a result of corrosion, radiation effects, or instability of material. The standard consists of seven articles and twelve mandatory and non-mandatory appendices to the articles; i.e., (1) Scope, roles and responsibilities, (2) Materials, (3) Structural design, (4) Fabrication and installation, (5) Non-destructive examination, (6), Pressure and leak testing, and (7) Terms used in general requirement. The present paper describes the general view of the standard. The detailed descriptions of the standard are described by the other papers in this session CS-21, being divided into four categories; i.e., (1) quality assurance, (2) materials, (3) structural design and replacement, and (4) welding, bonding and examination.

Paper 9: A Rotating Cylinder Viscometer for Measurement at Elevated Temperature and Pressure

1965 ◽  
Vol 180 (10) ◽  
pp. 153-162
Author(s):  
J. Wonham
Keyword(s):  
High Pressures ◽  
Rotating Cylinder ◽  
Wide Range ◽  
New Instrument ◽  
Temperature And Pressure ◽  
Major Alteration ◽  
Set Up ◽  
The Many ◽  
High Degree ◽  
Cylinder Viscometer

This paper records some of the recent experimental methods used to determine the viscosity of water. In drawing attention to the many techniques used (most relying upon calibration of the instrument by a fluid of known viscosity), the conclusion may be drawn that an absolute instrument is required which will produce results over a wide range of temperature and pressure. It has long been known that the rotating cylinder viscometer is capable of a high degree of accuracy, but technical considerations have, in the past, restrained most workers from pursuing this method at high pressures. Progress in the development of the rotating cylinder instrument for these conditions is described and specific problems encountered with this method are discussed. This work is a continuation of the design studies of Kjelland-Fosterud (1)† and Whitelaw (2) who both gave considerable thought to the problems associated with this type of instrument. The first instrument to be tested by the author was based on Whitelaw's design but it was found that certain aspects of this instrument required major alteration. A new instrument was set up and has been found suitable for accurate viscosity determination.

scholarly journals TEACHING PARAMETRICISM AS A STANDARD SKILL FOR ARCHITECTURE

2018 ◽  
Vol 42 (1) ◽  
pp. 34-39 ◽  
Author(s):  
Arne RIEKSTINS
Keyword(s):  
Programming Languages ◽  
Architectural Design ◽  
Structural Integrity ◽  
Parametric Design ◽  
Visual Programming ◽  
Young Generation ◽  
Form Finding ◽  
Cad Cam ◽  
Internal Relations ◽  
Set Up

The traditional need for coding to create parametric design has become quite obsolete with the advent of powerful visual programming languages for most becoming architects of the current young generation that are studying all around the world. Parametricism might become one of the standard skills for applicants seeking for a position at architectural design practices. It raises a question – how to implement the parametric knowledge into the workflow of a classical architectural designing approach, and rethinking the way we present these concepts at university level education of architecture. Additional knowledge of subjects is necessary, for example, about the structural integrity, material tolerance, fabrication optimization, sustainability issues etc. just to name the most frequent areas where lies the highest potential of making mistakes when these new systems are in use. Meanwhile the CAD/CAM paradigm that let architects design straight for fabrication brings new challenge for construction practice. Parametricism is an excellent platform of research for form finding, as there is very little amount of time needed to recreate significantly different design proposals by changing the variables, as soon as the bigger system of internal relations is set up.

Experimental and Numerical Investigations on VIV Response of a Pipe in Shear Flow

2020 ◽  
Author(s):  
Dipanjan Karanjai ◽  
S. Nallayarasu ◽  
S. K. Bhattacharya
Keyword(s):  
Axial Strain ◽  
Experimental Studies ◽  
Maximum Velocity ◽  
Rotating Cylinder ◽  
Offshore Structures ◽  
Sheared Flow ◽  
Shear Current ◽  
Steel Tank ◽  
Marine Applications ◽  
Set Up

Abstract The vortex induced vibration of slender cylindrical structures is common in offshore structures and marine applications such as risers, towing cables, etc. The VIV response of such slender elements in steady uniform current has been investigated in the past using numerical and experimental studies. Though few numerical studies exist for varying current (sheared flow), experimental studies are limited. Hence, the experimental studies are an essential part of VIV investigation, especially for sheared flow. The experiments were conducted using a specially fabricated circular steel tank of diameter 2.4 m with a central hinge to rotate the pipe horizontally in a water pool of depth 0.7 m. Shear current is simulated by rotating the pipe about the hinge. A pipe of diameter 25 mm (= D) and length 1 m (= L) was fixed at one end of the rotating cable support, and the other end was passed over a pulley inside a rotating cylinder. The rotating cylinder is provided with a pulley at the top to tension the pipe. A shear current with a maximum velocity of 1.3 m/s and a minimum velocity of 0.1 m/s is generated using the set up. The VIV response of the pipe was measured using electrical resistance-type strain gauges pasted along the length. The measured axial strain was used to obtain transverse displacements, which was used to determine the response frequency, amplitudes, and forces. The Strouhal number was calculated. The VIV response and the fluid force coefficients obtained from the experiments were compared with Shear7 results.

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