Nonlinear Flutter in Fan Stator Vanes With Time Dependent Fixity

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
R. Srivastava ◽  
J. Panovsky ◽  
R. Kielb ◽  
L. Virgin ◽  
K. Ekici
Keyword(s):  
Natural Frequency ◽  
High Speed ◽  
External Source ◽  
High Amplitude ◽  
Time Dependent ◽  
Turbofan Engines ◽  
Lower Natural Frequency ◽  
High Speeds ◽  
Stator Vane

A new mechanism for fan stator vane failure in turbofan engines at high speed and high loading has been identified and reported in this paper. Highly destructive vane failures have been encountered at Honeywell in a development fan with composite stator vanes. Measured data indicated nonlinear high amplitude vibratory response in fan stator vanes on the stall side of the fan map at high speeds. Analysis showed that under certain steady loading, vane fixity at the hub could change, significantly reducing the vane natural frequency. At this lower natural frequency, the vane was found to be aeroelastically unstable, and calculated response exhibited characteristics similar to those observed during failure. An engine test conducted to validate the role of hub fixity in vane failures showed the failure to be a self-excited phenomenon and not driven by an external source of excitation. It was also shown that failures occur in vanes that are not rigidly fixed, validating the role of hub fixity in vane failures. Test results along with analysis confirm the role of time dependent hub fixity leading to the highly destructive flutter responsible for vane failures.

Non-Linear Flutter in Fan Stator Vanes With Time Dependent Fixity

2010 ◽  
Author(s):  
R. Srivastava ◽  
J. Panovsky ◽  
R. Kielb ◽  
L. Virgin ◽  
K. Ekici
Keyword(s):  
Natural Frequency ◽  
High Speed ◽  
External Source ◽  
High Amplitude ◽  
Time Dependent ◽  
Test Results ◽  
Turbofan Engines ◽  
Lower Natural Frequency ◽  
Stator Vane

A new mechanism for fan stator vane failure in turbofan engines at high speed and high loading has been identified and reported in this paper. Highly destructive vane failures have been encountered at Honeywell in one of the development fans with composite stator vanes. Measured data indicated nonlinear high amplitude vibratory response in fan stator vanes on stall side of the fan map at high speeds. Analysis showed that under certain vane steady loading vane fixity at hub could change, significantly reducing the vane natural frequency. At lower natural frequency the vane was found to be aeroelastically unstable and calculated response exhibited behavior observed during failure. An engine test was conducted to validate the role of hub fixity in vane failures. Test results showed failure to be a self-excited phenomenon and not driven by an external source of excitation. It was also shown that failures occur in vanes that are not rigidly fixed, validating the role of hub fixity in vane failures. Test results along with the analysis confirm the role of time dependent hub fixity leading to the highly destructive flutter responsible for vane failures.

A Statistical Study of Process Variables to Optimize a High Speed Curtain Coater: Part I

TAPPI Journal ◽  
2009 ◽  
Vol 8 (1) ◽  
pp. 20-26 ◽  
Author(s):  
PEEYUSH TRIPATHI ◽  
MARGARET JOYCE ◽  
PAUL D. FLEMING ◽  
MASAHIRO SUGIHARA
Keyword(s):  
Boundary Layer ◽  
Experimental Design ◽  
High Speed ◽  
Statistical Study ◽  
Process Variables ◽  
High Speeds ◽  
The Stability ◽  
Air Removal ◽  
Removal System

Using an experimental design approach, researchers altered process parameters and material prop-erties to stabilize the curtain of a pilot curtain coater at high speeds. Part I of this paper identifies the four significant variables that influence curtain stability. The boundary layer air removal system was critical to the stability of the curtain and base sheet roughness was found to be very important. A shear thinning coating rheology and higher curtain heights improved the curtain stability at high speeds. The sizing of the base sheet affected coverage and cur-tain stability because of its effect on base sheet wettability. The role of surfactant was inconclusive. Part II of this paper will report on further optimization of curtain stability with these four variables using a D-optimal partial-facto-rial design.

Theoretical and Experimental Studies on Squeeze Film Stabilizers for Flexible Rotor-Bearing Systems Using Newtonian and Viscoelastic Lubricants

1990 ◽  
Vol 112 (4) ◽  
pp. 473-482 ◽  
Author(s):  
B. Halder ◽  
A. Mukherjee ◽  
R. Karmakar
Keyword(s):  
High Speed ◽  
Experimental Studies ◽  
Squeeze Film ◽  
Experimental Investigations ◽  
Flexible Rotor ◽  
Stability Range ◽  
High Speeds ◽  
Flexible Rotors ◽  
Rotor Bearing

A combination of a squeeze film damper and a plane journal bearing is studied as a stabilizing scheme. The damper is made to play the role of a stabilizer to postpone the instability threshold speeds of flexible rotors. Both Newtonian and viscoelastic fluids are used in the rotor-bearing system. Dynamics of the system is theoretically analyzed using bond graphs. Analysis reveals that the use of a Newtonian fluid in the stabilizer largely improves the high speed stability range. However, viscoelastic stabilizing fluid has a detrimental effect on highly flexible rotors. Experimental investigations, conducted on a flexible rotor (natural frequency, 30 Hz), confirm the theoretical findings. In addition, experiments indicate that though the use of viscoelastic stabilizing fluids leads to instability in flexible rotors, the growth of large amplitude whirl is postponed to very high speeds.

Dynamics of Spindle-Bearing Systems at High Speeds Including Cutting Load Effects

1998 ◽  
Vol 120 (2) ◽  
pp. 387-394 ◽  
Author(s):  
Bert R. Jorgensen ◽  
Yung C. Shin
Keyword(s):  
Natural Frequency ◽  
High Speed ◽  
Dynamic Models ◽  
Complex Geometry ◽  
Beam Theory ◽  
Coupled System ◽  
Influence Coefficient ◽  
High Speeds ◽  
Spindle Bearing ◽  
Influence Coefficient Method

Increased use of high speed machining creates the need to predict spindle-bearing performance at high speeds. Previous spindle-bearing models simplify either spindle or bearing dynamics to the extent of prohibiting a detailed analysis of a spindle with high speed motion. At high speeds, centrifugal loading in the bearing causes stiffness softening, creating a change in natural frequency. Therefore, spindle modeling requires a comprehensive representation of the dynamics of shafts with complex geometry rotating at high speeds and supported by non-linear bearings. This paper presents a coupled system of spindle and bearing dynamic models with numerical solution. Spindle dynamics are modeled using the influence coefficient method of discrete lumped masses, based on Timoshenko beam theory. Both linear and rotational bearing stiffness are included in the spindle model through solution of the angular-contact bearing model. The parameters of cutting loads, tool mass, and rotational speed are analyzed, and all are shown to affect the natural frequency. The computer model is both rapid and robust, and shows excellent agreement with experimental analysis.

Analysis of the Effect the Modal-Parameter on the Milling Stability

2013 ◽  
Vol 372 ◽  
pp. 459-462
Author(s):  
Ming Chang Tsai ◽  
Te Ching Hsiao ◽  
Shyh Chour Huang
Keyword(s):  
Natural Frequency ◽  
High Precision ◽  
High Speed ◽  
Damping Ratio ◽  
Chatter Stability ◽  
Modal Parameter ◽  
High Speeds ◽  
Stability Lobe ◽  
The Stability ◽  
Chatter Stability Lobes

In the past few years, it has become a tendency to develop machinery of high speeds and high precision. In order to meet the need for high-speed manufacturing of high precision components, the machine tools structure must be very stiff and have high cutting stability levels. Should the process of the firsthand milling be unstable, the effects include cutting tool breakages, decrease in surface accuracy and could even shorten the machine tolls lifespan. Thus, in the manufacturing of milling, chattering often causes problems for the manufacturer. To prevent cases of milling chattering, there is a need to use a chatter stability lobe to predict the chatter stability and to analyze the effect the modal-parameter has on the stability of milling. This research paper uses the Zero-Order Analytical Method (ZOA) to analyze and compare the effects modal-parameter (natural frequency, damping ratio, modal stiffness) has on the stability of the milling system. The results show that level of stiffness and the damping ratio influences the vertical shape of the chatter stability lobes while the natural frequency affects the lateral shape of the lobes.

scholarly journals Energetic advantages of burst-and-coast swimming of fish at high speeds

1982 ◽  
Vol 97 (1) ◽  
pp. 169-178 ◽  
Author(s):  
J. J. Videler ◽  
D. Weihs
Keyword(s):  
Theoretical Model ◽  
High Speed ◽  
Muscle Fibres ◽  
Glycogen Depletion ◽  
Free Swimming ◽  
Kinematic Data ◽  
High Speeds ◽  
Optimal Values ◽  
Swimming Style

A theoretical model describes how an intermittent swimming style can be energetically advantageous over continuous swimming at high average velocities. Kinematic data are collected from high-speed cine pictures of free swimming cod and saithe at high velocities in a burst-and-coast style. These data suggest that fish make use of the advantages shown by choosing initial and final burst velocities close to predicted optimal values. The limiting role of rapid glycogen depletion in fast white anaerobic muscle fibres is discussed.

RED CUT COBALT

Alloy Digest ◽  
1980 ◽  
Vol 29 (8) ◽  
Keyword(s):  
Fracture Toughness ◽  
Cast Iron ◽  
High Speed ◽  
Elevated Temperatures ◽  
High Speed Steel ◽  
Heat Treating ◽  
High Speeds ◽  
Red Hardness ◽  
Nonferrous Alloys ◽  
Cutting Point

Abstract RED CUT COBALT steel is made by adding 5% cobalt to the conventional 18% tungsten -4% chromium-1% vanadium high-speed steel. Cobalt increases hot or red hardness and thus enables the tool to maintain a higher hardness at elevated temperatures. This steel is best adapted for hogging cuts or where the temperature of the cutting point of the tool in increased greatly. It is well adapted for tools to be used for reaming cast-iron engine cylinders, turning alloy steel or cast iron and cutting nonferrous alloys at high speeds. This datasheet provides information on composition, physical properties, and hardness as well as fracture toughness. It also includes information on forming, heat treating, and machining. Filing Code: TS-367. Producer or source: Teledyne Vasco.

CPM REX 25

Alloy Digest ◽  
1980 ◽  
Vol 29 (7) ◽  
Keyword(s):  
Heat Treatment ◽  
High Speed ◽  
High Speed Steel ◽  
High Hardness ◽  
Heat Treating ◽  
High Speeds ◽  
Aisi Type ◽  
Tool Performance ◽  
End Mills ◽  
Machining Operations

Abstract CPM REX 25 is a super high-speed steel made without cobalt. It is comparable to AISI Type T15 cobalt-containing high-speed steel in response to heat treatment, properties, and tool performance. CPM REX 25 is recommended for machining operations requiring heavy cuts, high speeds and feeds, and difficult-to-machine materials of high hardness and abrasion resistance. Typical applications are boring tools, drills, gear cutters, punches, form tools, end mills and broaches. This datasheet provides information on composition, physical properties, hardness, and elasticity as well as fracture toughness. It also includes information on forming, heat treating, machining, and surface treatment. Filing Code: TS-365. Producer or source: Crucible Materials Corporation.

LANDSLIDE RISK MANAGEMENT IN THE COASTAL ZONE OF THE KUIBYSHEV RESERVOIR DUE THE DESIGN OF HIGH-SPEED LINE "MOSCOW-KAZAN"

2017 ◽  
Author(s):  
Nikolai Petrov ◽  
Nikolai Petrov ◽  
Inna Nikonorova ◽  
Inna Nikonorova ◽  
Vladimir Mashin ◽  
...  
Keyword(s):  
High Speed ◽  
Computational Models ◽  
Stable State ◽  
Landslide Risk ◽  
Kuibyshev Reservoir ◽  
Stepped Surface ◽  
The Stability ◽  
Landslide Slope ◽  
The Village

High-speed railway "Moscow-Kazan" by the draft crosses the Volga (Kuibyshev reservoir) in Chuvashia region 500 m below the village of New Kushnikovo. The crossing plot is a right-bank landslide slope with a stepped surface. Its height is 80 m; the slope steepness -15-16o. The authors should assess the risk of landslides and recommend anti-landslide measures to ensure the safety of the future bridge. For this landslide factors have been analyzed, slope stability assessment has been performed and recommendations have been suggested. The role of the following factors have been analyzed: 1) hydrologic - erosion and abrasion reservoir and runoff role; 2) lithologyc (the presence of Urzhum and Northern Dvina horizons of plastically deformable rocks, displacement areas); 3) hydrogeological (the role of perched, ground and interstratal water); 4) geomorphological (presence of the elemental composition of sliding systems and their structure in the relief); 5) exogeodynamic (cycles and stages of landslide systems development, mechanisms and relationship between landslide tiers of different generations and blocks contained in tiers). As a result 6-7 computational models at each of the three engineering-geological sections were made. The stability was evaluated by the method “of the leaning slope”. It is proved that the slope is in a very stable state and requires the following measures: 1) unloading (truncation) of active heads blocks of landslide tiers) and the edge of the plateau, 2) regulation of the surface and groundwater flow, 3) concrete dam, if necessary.

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