Blade Displacement Research Articles

Dynamic Response Analysis of Large Wind Turbine Blade Based on Davenport Wind Speed Model

Fluctuating wind speed spectrum, which is closer to the actual working conditions, was simulated by davenport wind speed model, and displacement and stress distribution of blade under fluctuating wind speed were calculated by finite element analysis software. The numerical results indicate that the growth trend of vibration amplitude for whole blade at flapping direction is nonlinear along the wingspan. The max von-mises stress appears when the vibration amplitude of tip reaches the maximum, and it is mainly concentrated in the central part of the blade. The stress at trailing edge and tip is smaller than the central part. Above results provide a reference for the strength safety design of wind turbine blade.,Fluctuating wind speed spectrum, which is closer to the actual working conditions, was simulated by davenport wind speed model, and displacement and stress distribution of blade under fluctuating wind speed were calculated by finite element analysis software. The numerical results indicate that the growth trend of vibration amplitude for whole blade at flapping direction is nonlinear along the wingspan. The max von-mises stress appears when the vibration amplitude of tip reaches the maximum, and it is mainly concentrated in the central part of the blade. The stress at trailing edge and tip is smaller than the central part. Above results provide a reference for the strength safety design of wind turbine blade.

Optimal Design of Mechanism Parameters for Rolling-Cut Shear

In order to improve shearing quality, the structure of rolling-cut shear (RCS) should be designed carefully to guarantee a pure rolling condition of the top blade and the amount of scissors overlapping (ASO). This paper describes an investigation into the work mechanism of RCS. A parametric model of RCS has been established by using ADAMS software. The influences of the ASO and the horizontal displacement of the top blade (HDTB) are also discussed. The indications are that the length of crank, guide rod and link, initial phase angle, the position of gyration center for guide rod and the radius of the top blade arc are key factors to the ASO and HDTB. Moreover, those structure parameters that influence the ASO and HDTB are selected as design variables. An optimal mathematic model has been established by using two objective functions that are ASO and HDTB in the cutting process. This optimization model has been used successfully in the development of RCS 3800 to obtain reasonable mechanism dimensions for improving shearing quality. The study results provide a new idea for designing the RCS.

Strength Analysis of 2000L-B Vertical Mixer’s Blades with FEM

The torsion load of 2000L-B vertical mixer’s blade was firstly calculated by the relation between torsion input and output of planetary gear train. Then by means of finite element software ANSYS, analyses on stress and displacement of solid blade and hollow blade in mixer were carried out. As result, the stress and displacement contour maps were obtained and the maximum stress and deformation values were found. The strength checking of blade indicated that the blade had enough stability and strength margin.

Metal ductility at low stress triaxiality application to sheet trimming

The growth and coalescence of voids nucleated by decohesion or cracking of second phase particles is a common damage process for many metallic alloys. Classical damage models, based on void growth and coalescence, predict a ductility increase if the stress triaxiality is decreased. But experiments show that the material ductility decreases at very low stress triaxialities typical of sheet metal forming operations. At very low stress triaxiality no void growth is observed in metals containing second phase particles. In the present work, a new damage model for metals containing second phase particles submitted to low stress triaxiality loading is proposed. The new model is based on the observed physical damage mechanism, i.e. strain localization by reducing the inter-particle spacing during large material rotations. A two step modelling strategy has been followed to determine the ductility at low stress triaxiality. In the first step Thomason's void coalescence model is extended to large material rotations and shearing. In the second step the principles of applying this model to damage nucleated at second phase particles are described. The large material rotations observed under low stress triaxiality loading lead to large changes in the microstructure. Thus, in the second step, first appropriate representative volume and material elements are determined and then the critical damage parameters. Finally, as an example, the trimming behaviour of two aluminium sheet alloys is analyzed by the new model and the model predictions shown to be in good agreement with the experimental data, in particular for the blade displacement to crack initiation. The main outcomes of this work are: (1) a void coalescence model valid at low stress triaxiality, (2) a damage criterion valid at small stress triaxiality and large material rotations, (3) a damage variable expressed in a simple closed form for materials containing second phase particles. The damage analysis in a small fixed volume with a representative microstructure (Eulerian approach) and the damage analysis in all the material elements of the considered structure are compared in detail. In trimming (or similar processes), the major contribution to damage the material movement bringing second phase particles closer together and the void growth may be neglected. This simplifies considerable the analysis.

Finite Element Modeling of the Left Atrium to Facilitate the Design of an Endoscopic Atrial Retractor

With the worldwide prevalence of cardiovascular diseases, much attention has been focused on simulating the characteristics of the human heart to better understand and treat cardiac disorders. The purpose of this study is to build a finite element model of the left atrium (LA) that incorporates detailed anatomical features and realistic material characteristics to investigate the interaction of heart tissue and surgical instruments. This model is used to facilitate the design of an endoscopically deployable atrial retractor for use in minimally invasive, robotically assisted mitral valve repair. Magnetic resonance imaging (MRI) scans of a pressurized explanted porcine heart were taken to provide a 3D solid model of the heart geometry, while uniaxial tensile tests of porcine left atrial tissue were conducted to obtain realistic material properties for noncontractile cardiac tissue. A finite element model of the LA was constructed using ANSYS Release 9.0 software and the MRI data. The Mooney-Rivlin hyperelastic material model was chosen to characterize the passive left atrial tissue; material constants were derived from tensile test data. Finite element analysis (FEA) models of a CardioVations Port Access retractor and a prototype endoscopic retractor were constructed to simulate interaction between each instrument and the LA. These contact simulations were used to compare the quality of retraction between the two instruments and to optimize the design of the prototype retractor. Model accuracy was verified by comparing simulated cardiac wall deflections to those measured by MRI. FEA simulations revealed that peak forces of approximately 2.85 N and 2.46 N were required to retract the LA using the Port Access and prototype retractors, respectively. These forces varied nonlinearly with retractor blade displacement. Dilation of the atrial walls and rigid body motion of the chamber were approximately the same for both retractors. Finite element analysis is shown to be an effective tool for analyzing instrument/tissue interactions and for designing surgical instruments. The benefits of this approach to medical device design are significant when compared to the alternatives: constructing prototypes and evaluating them via animal or clinical trials.

Modeling Soft-Tissue Deformation Prior to Cutting for Surgical Simulation: Finite Element Analysis and Study of Cutting Parameters

This paper presents an experimental study to understand the localized soft-tissue deformation phase immediately preceding crack growth as observed during the cutting of soft tissue. Such understanding serves as a building block to enable realistic haptic display in simulation of soft tissue cutting for surgical training. Experiments were conducted for soft tissue cutting with a scalpel blade while monitoring the cutting forces and blade displacement for various cutting speeds and cutting angles. The measured force-displacement curves in all the experiments of scalpel cutting of pig liver sample having a natural bulge in thickness exhibited a characteristic pattern: repeating units formed by a segment of linear loading (deformation) followed by a segment of sudden unloading (localized crack extension in the tissue). During the deformation phase immediately preceding crack extension in the tissue, the deformation resistance of the soft tissue was characterized with the local effective modulus (LEM). By iteratively solving an inverse problem formulated with the experimental data and finite element models, this measure of effective deformation resistance was determined. Then computational experiments of model order reduction were conducted to seek the most computationally efficient model that still retained fidelity. Starting with a 3-D finite element model of the liver specimen, three levels of model order reduction were carried out with computational effort in the ratio of 1.000:0.103:0.038. We also conducted parametric studies to understand the effect of cutting speed and cutting angle on LEM. Results showed that for a given cutting speed, the deformation resistance decreased as the cutting angle was varied from 90 degrees to 45 degrees. For a given cutting angle, the deformation resistance decreased with increase in cutting speed.

B102 流体構造連成振動下におけるタービン翼列周りの流れの可視化

In the present study, the two- and three-dimensional analyses for turbine blades subjected to flow-induced vibration are compared. To consider the time-dependent motions. of blades, an arbitrary Lagrangian-Eulerian formulation is employed. A complete Navier-Stokes solver incorporating a moving mesh and analytic solutions of the motion equations for the. blade translation and rotation are applied. In the flow-induced vibration condition, the drag, lift and moment coefficients exhibited the time history coupled with the same frequency as that of non-coupling fluid forces and the blade natural frequency. The magnitude of blade fluctuation gradually increased with the reduced velocity. Although the small-scale vortices showing the three-dimensional structure were generated, there were no remarkable differences between two- and three-dimensional simulation in the reduced velocity starting flow induced vibration and the amplitude of the blade displacement.

An Investigation into Scalpel Blade Sharpness Using Cutting Experiments and Finite Element Analysis

This paper presents an investigation into the sharpness of a surgical scalpel blade. An experiment was carried out in which a surgical scalpel blade was pushed through an elastomeric substrate at a constant velocity. The force-displacement characteristics were examined by plotting the stiffness as a function of blade displacement and it was found that this curve could clearly identify the point where the material separates to form a cut. A blade sharpness measurement was defined as the energy required to initiate an opening or cut in the substrate. A finite element model was developed to examine the stress state in the substrate at the point where the opening initiates. The development of this model is described. The model was validated against the experiment and close agreement was obtained. The von-Mises stress distribution under the blade tip was plotted and it was shown that the peak stress actually occurs away from the blade tip, suggesting that material separation would initiate away from the substrate surface.

Capacitive Sensor for Active Tip Clearance Control in a Palm-Sized Gas Turbine Generator

The efficiency of a gas turbine has an inverse relationship to the clearance between the rotor blades and the casing. Recent efforts in miniaturization of micro gas turbine engines have created a new challenge in blade tip clearance measurement. This paper describes the development of a capacitive tip clearance measurement system, based on a synchronous detection of a phase-modulated signal, for a palm-sized gas turbine engine with an integral ceramic rotor piece. A surface modification of the ceramic compressor and rotor with conductive coating is utilized to create a novel configuration of a tip clearance probe. The probe capacitance varies by approximately 120 fF for a 100-/spl mu/m blade displacement. Periodic autocalibration is used to reduce the effects of temperature drift on the sensor output. The remaining measurement error drift of 1.5 fF//spl deg/C was caused by the temperature drift of the probe parasitic capacitor. The random uncertainty was between 1.9 and 6.9 /spl mu/m depending on the tip clearance gap.

Simulation of soil–blade interaction for sandy soil using advanced 3D finite element analysis

In this paper a finite element investigation of the tillage of dry sandy soil, using the hypoplastic constitutive material model, is described. In most earth moving machinery, such as bulldozers or tillage tools, the working tool is a blade. Hence for tillage systems, accurately predicting the forces acting on the blade is of prime importance in helping to enhance productivity. The initial conditions, such as blade geometry or soil type, and operating conditions, such as cutting speed and cutting depth, have been shown experimentally to have a great effect on machine productivity. Experimental studies give valuable insights but can be expensive and may be limited to certain cutting speeds and depths. Results are also highly dependent on the accuracy of the measuring devices. However with increasing computational power and the development of more sophisticated material models, finite element analysis shows more promise in analyzing the factors affecting soil–blade interaction. Most of the available finite element studies in the literature are two-dimensional or if three-dimensional (3D), are limited to a certain blade displacement depending on the element distortion limit before the solution has convergence problems. In this study, a 3D finite element analysis of soil–blade interaction was carried out based on predefined horizontal and vertical failure surfaces, to investigate the behavior of the soil–blade interface and study the effect of blade-cutting width and lateral boundary width on predicted forces. Sandy soil was considered in this study and modeled using the hypoplastic constitutive model implemented in a commercial finite code, ‘ABAQUS’. Results reveal the validity of the concept of predefined failure surfaces in simulating soil–blade interaction and the significant effect of blade-cutting width, lateral boundary width and soil swelling on cutting forces.

3D Dynamic analysis of soil–tool interaction using the finite element method

Previous experimental and finite element studies have shown the influence of both soil initial conditions and blade operating conditions on cutting forces. However, most of these finite element analyses (FEA) are limited to small blade displacements to reduce element distortion which can cause solution convergence problems. In this study a dynamic three-dimensional FEA of soil–tool interaction was carried out based on predefined failure surfaces to investigate the effect of cutting speed and angle on cutting forces over large blade displacements. Sandy soil was considered in this study and modeled using the hypoplastic constitutive model implemented in the commercial FEA package, ABAQUS. Results reveal the validity of the concept of predefined failure surfaces in simulating soil–tool interaction and the significant effect of cutting acceleration on cutting forces.

Computation of Mistuning Effects on Cascade Flutter

A computational method is described for predicting eutter of turbomachinery cascades with mistuned blades. Themethodsolves theunsteadyEuler/Navier‐Stokesequationsformultiple-bladepassageson aparallel computer usingthemessagepassinginterface. Asecond-orderimplicit schemewithdualtime-steppingand multigrid isused. Each individual blade is capable of moving with its own independent frequency and phase angle, thus modeling a cascade with mistuned blades. Flutter predictions are performed through the energy method. Both phase-angle and frequency mistuning are studied. It is found that phase-angle mistuning has little effect on stability, whereas frequencymistuningsignie cantlychanges theaerodynamicdamping.Theimportant effectoffrequencymistuning is to average out the aerodynamic damping of the tuned blade row over the whole range of interbladephase angles (IBPA). If a tuned blade row is stable over most of the IBPA range, the blades can be stabilized for the complete IBPA range through appropriate frequency mistuning. Nomenclature Ch = coefecient of aerodynamic force in h direction CW = aerodynamic work coefe cient c = blade chord length E = total energy per unit mass h = translational blade displacement p = static pressure T = e utter period t = time u, v = e ow velocity components in x and y directions ub, vb = grid velocity components in x and y directions ¯ u, ¯ v = relative velocity components (u i ub, v i vb) a = rotational blade displacement h = stream tube thickness ratio in x direction N = e utter damping coefe cient q = density r = interblade phase angle x = e utter frequency

An Integrated Time-Domain Aeroelasticity Model for the Prediction of Fan Forced Response due to Inlet Distortion

The forced response of a low aspect-ratio transonic fan due to different inlet distortions was predicted using an integrated time-domain aeroelasticity model. A time-accurate, nonlinear viscous, unsteady flow representation was coupled to a linear modal model obtained from a standard finite element formulation. The predictions were checked against the results obtained from a previous experimental program known as “Augmented Damping of Low-aspect-ratio Fans” (ADLARF). Unsteady blade surface pressures, due to inlet distortions created by screens mounted in the intake inlet duct, were measured along a streamline at 85 percent blade span. Three resonant conditions, namely 1F/3EO, 1T & 2F/8EO and 2S/8EO, were considered. Both the amplitude and the phase of the unsteady pressure fluctuations were predicted with and without the blade flexibility. The actual blade displacements and the amount of aerodynamic damping were also computed for the former case. A whole-assembly mesh with about 2,000,000 points was used in some of the computations. Although there were some uncertainties about the aerodynamic boundary conditions, the overall agreement between the experimental and predicted results was found to be reasonably good. The inclusion of the blade motion was shown to have an effect on the unsteady pressure distribution, especially for the 2F/1T case. It was concluded that a full representation of the blade forced response phenomenon should include this feature.

Flutter Analysis of Cascades Using an Euler/Navier-Stokes Solution-Adaptive Approach

In this study, cascade flutter analyses for inviscid and viscous flows are presented. In the present timedomain approach, the structural model equations for each blade as a typical section having plunging and pitching degrees of freedom are integrated in time by the explicit four-stage Runge-Kutta scheme. A solution-adaptive finite volume method with globally/rigid-deformable dynamic mesh treatments is introduced to solve the two-dimensional Euler/Navier -Stokes equations. For viscous flows, the BaldwinLomax turbulence model and two transition formulations are adopted. By comparing with the related data in two inviscid transonic-cascade-flutter problems, the reliability and suitability of the present approach are confirmed. From the time histories of blade displacements and total energy in transonic-flutter calculations, it is observed that the viscous effect has a damping influence on the aeroelastic behavior. The instantaneous meshes and vorticity contours clearly indicate the shock/boundary-layer interaction, large vortex structure, and big plunging motion in the transonic flutter, subsonic stall flutter, and supersonic bending flutter, respectively. By using the fast Fourier transformation and modal identification techniques, the aeroelastic behaviors in the inviscid transonic and viscous transonic, subsonic stall, and supersonic bending flutter problems are further investigated.

Calibration of trephine blade depth.

To assess the accuracy and precision of the Barron radial vacuum trephine as an instrument for corneal lamellar dissection. We describe a practical method to calibrate individual trephines prior to lamellar corneal procedures using the calibration microscope designed for diamond knives. We observed that one turn (360 degrees) of the trephine produced a mean blade displacement of 0.25 mm. However, individual trephines demonstrated a significant range of variability. For highly accurate trephination, it is useful to calibrate each individual trephine using the calibration microscope.

Experimental investigation of counter-rotating propfan flutter at cruise conditions

The paper presents wind tunnel experimental flutter results, at transonic relative flows, for a 0.62-m diameter composite propfan model. A blade row that fluttered was tested alone, and with a stable aft counter-rotating blade row. The major objectives of the experiment were to study the effect of the second blade row on the row in flutter, and to investigate the flutter. Results show that the second row had a stabilizing effect. Two distinct flutter modes were found. For both flutter modes: flutter boundary, frequency, nodal diameter, and blade displacement data are given. The blade displacement data, obtained with an optical method, gives an indication of the flutter mode shape at a span near the blade tip.

On the Mechanism of Dangerous Blade Vibration Due to Blade Flow Interactions on Centrifugal Compressors

Severe blade flow interactions at part-load operation conditions were investigated on a centrifugal compressor with a vaned diffuser leading to material stresses beyond the allowable values. By means of a number of measurement and analysis techniques it could be found, that a stationary periodic pressure field is produced on the circumference by the vibrating blade itself, which is induced at resonance conditions by the peripheral pressure nonuniformity due to the outlet tube. This peripheral pressure field of an integer wave number intensifies the blade resonance excitation from downstream leading to an additivity effect between wave amplitude and blade displacement. The significant role in this mechanism plays the reverse flow near the corner shroud/suction side in the impeller, occurring at part-load operation, which is controlled by the interaction of the tip angle of the vibrating blade and the flow angle at that location. It could be demonstrated that this dangerous blade vibration, in addition, is the source of a shift of the surge line toward higher mass flow, reducing the compressor operating range considerably in this operating zone.

Use of modified atmospheres to control storage rot of carrot caused by Sclerotinia sclerotiorum

The potential of silicone membranes to provide modified atmospheres for control of storage rot of carrot caused by Sclerotinia sclerotiorum (Lib.) de Bary and maintain carrot quality was assessed. Carrots were stored in five different atmospheres: high relative humidity ( HRA), unadjusted cold room atmosphere ( RA), and three atmospheres with modified CO 2 and O 2 concentrations (referred to as A, B and C). Containers fitted with silicone membranes of varying surface areas were used to maintain these atmospheres. Carrots in one-half of the containers were inoculated with S. sclerotiorum. The experiment was carried out in a cold room maintained at 1°C and was terminated after 6 months. The mean CO 2/O 2 percentages for modified atmospheres were 1.17/14.19, 1.52/12.11, 3.03/4.57, 3.81/3.73, 4.26/4.47 and 6.09/3.03% for treatments A1, B1, C1 (carrots without inoculum), A2, B2 and C2 (carrots with inoculum), respectively. All modified CO 2 and O 2 treatments provided better control of Sclerotina rot than did HRA and RA. Carrots of treatments HRA1, A1, B1 and C1 (carrots without inoculum) were kept for evaluation by a taste panel and quality assessment. Taste panel evaluation indicated that carrots from treatment C1 were superior to store-bought carrots and carrots from other treatments. Quality assessment indicated that work (defined as load versus blade displacement when carrots were cut with an Instron apparatus) was significantly greater for HRA1 as compared to the other treatments and that modulus (defined as the slope of the curve of force versus the distance travelled during the cut) was significantly higher for C1 than HRA1 and RA1.

Rotor blade aeroelasticity in forward flight with an implicit aerodynamic formulation

This paper describes a new methodology for formulating the aeroelastic stability and response problem for helicopter rotor blades. The mathematical expressions for the aerodynamic loads heed not be explicit functions of the blade displacement quantities. The methodology is combined with a finite-element model of the blade and a quasilinearization solution technique. The resulting computer program is used to study the behavior of blades with noncoincident elastic axis, aerodynamic centers, and centers of mass.

Stable lingual gestures in vowel articulation

Lingual movements monitored by lateral cineradiographic pellet tracking along with first and second formant frequencies for the articulation of /i/ and /u/ in labial, alveolar, and velar stop (əCVC/ syllables were analyzed in order to quantify both the relatively stable and more variable components of vowel-related tongue movements that occur as a function of stop coproduction. Horizontal and vertical tongue displacements varied by as much as 10 mm at tongue body locations for /i/ and 6 mm at tongue blade and anterior tongue body locations for /u/. Formant frequencies varied correspondingly. However, vertical displacement of the tongue blade for /i/ and of the posterior tongue body for /u/ were much more stable. These relatively stable displacement components suggest that the characteristic gestures for /i/ and /u/ act to create critical oral cavity apertures by tongue blade and posterior tongue body vertical displacements, respectively. The precise anterior-posterior locations of the lingual constriction are not specified in the gestures and are free to vary with consonantal coproduction. [Work supported by NIH NS-13617 and NS-13870.]