bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of counting chamber type on CASA outcomes of equine semen analysis
Authors: HOOGEWIJS M. K. , DE VLIEGHER S. P. , GOVAERE J. L. , DE SCHAUWER C. , DE KRUIF A. , VAN SOOM A.
Published: December 2011

Reasons for performing study: Sperm motility is considered to be one of the key features of semen analysis. Assessment of motility is frequently performed using computer‐assisted sperm analysis (CASA). Nevertheless, no uniform standards are present to analyse a semen sample using CASA.

Objectives: We hypothesised that the type of counting chamber used might influence the results of analysis and aimed to study the effect of chamber type on estimated concentration and motility of an equine semen sample assessed using CASA.

Methods: Commonly used disposable Leja chambers of different depths were compared with disposable and reusable ISAS chambers, a Makler chamber and a World Health Organization (WHO) motility slide. Motility parameters and concentrations obtained with CASA using these different chambers were analysed. The NucleoCounter was used as gold standard for determining concentration.

Results: Concentration and motility parameters were significantly influenced by the chamber type used. Using the NucleoCounter as the gold standard for determining concentration, the correlation coefficients were low for all of the various chambers evaluated, with the exception of the 12 µm deep Leja chamber. Filling a chamber by capillary forces resulted in a lower observed concentration and reduced motility parameters. All chambers evaluated in this study resulted in significant lower progressive motility than the WHO prepared slide, with the exception of the Makler chamber, which resulted in a slight, but statistically significant, increase in progressive motility estimates.

Conclusions and potential relevance: Computer‐assisted sperm analysis can only provide a rough estimate of sperm concentration and overestimation is likely when drop‐filled slides with a coverslip are used. Motility estimates using CASA are highly influenced by the counting chamber; therefore, a complete description of the chamber type used should be provided in semen reports and in scientific articles.
The impact of pre‐treatment weight‐loss expectations on weight loss, weight regain, and attrition in people who are overweight and obese: A systematic review of the literature
Authors: Crawford Rochelle , Glover Lesley
Published: December 2011

Purpose. Research exploring the relationships between initial weight‐loss expectations with actual outcome in terms of weight loss, weight regain, and attrition/attendance suggests contradictory findings. The purpose of this review was to collate research exploring the impact of weight‐loss expectations on weight loss, weight regain, and attendance/attrition. It was hoped this would further the current understanding of the relationship between expectations and outcome.

Methods. PsychInfo, Medline, and Web of Science were systematically searched and 13 relevant papers were identified. To be included for review, studies had to assess and analyse weight‐related expectations; distinguish between higher and lower expectations; include participants who were aged over 18 and attempting to lose weight; be published within a peer‐reviewed journal between 1990 and 2010. Findings were analysed qualitatively.

Results. Findings were largely unclear. The relationship between expectations and weight loss appears to change with time, whilst the findings from studies looking at weight regain suggest that there is no association. The relationship between expectations with attendance/attrition is also unclear.

Conclusions. Through reviewing literature regarding the relationships between expectations with various outcomes, a number of discrepancies emerged. Exploration of these discrepancies enabled an understanding to be developed of the complex relationship between expectations and weight‐loss treatment outcome. The importance of the terminology used and the ways in which expectations are assessed is discussed and future areas of research are suggested.
Fast reduction of peripheral blood endothelial progenitor cells in healthy humans exposed to acute systemic hypoxia
Authors: Colombo Elena , Marconi Claudio , Taddeo Adriano , Cappelletti Monica , Villa Maria Luisa , Marzorati Mauro , Porcelli Simone , Vezzoli Alessandra , Bella Silvia Della
Published: December 2011

Non‐technical summary  The endothelium is a thin layer of cells lining the interior surface of the entire circulatory system. Endothelial progenitor cells (EPCs) have a crucial role in maintaining the integrity of the endothelium, as they are recruited from the bone marrow to sites of endothelial injury where they contribute to blood vessel formation and repair. The factors regulating EPC mobilization and trafficking remain incompletely understood. We evaluated the time‐course effects of a single 4 h bout of severe hypoxic breathing (simulating 4100 m altitude) followed by 4 h restoration in room air. We show that hypoxia alone induces a rapid disappearance of EPCs from blood, probably sustained by a prompt cell marginalization followed by a late increase in EPC apoptosis. These observations may broaden our understanding of the mechanisms operated by EPCs to maintain endothelial homeostasis and may help to elucidate the potential role of EPCs in regenerative medicine.
M channel enhancers and physiological M channel block
Authors: Linley John E. , Pettinger Louisa , Huang Dongyang , Gamper Nikita
Published: December 2011

Non‐technical summary  Specific membrane proteins called ‘M channels’ control the excitability of peripheral pain‐sensing nerves. In certain disease conditions (e.g. inflammation), M channels become inhibited, and this contributes to the increased excitability of these nerves and, ultimately, to pain sensation. Recently, chemical compounds that enhance M channel activity have been discovered and were suggested as prospective analgesics. However, it was previously unknown whether these M channel enhancers could augment the activity of M channels that are inhibited in inflammatory conditions. We tested four compounds that possess M channel enhancer activity in various conditions mimicking inflammation. Our conclusions suggest that while the overall effect of the enhancers is reduced when M channels are inhibited, the remaining enhancement is sufficient to ‘recover’ M channel activity from inflammation‐induced inhibition. Our results support pharmacological targeting of M channels in peripheral nerves as a strategy against inflammatory pain.
Creep Crack Initiation and Propagation: Fracture Mechanics and Local Approach
Authors: Bensussan P. , Maas E. , Pelloux R. , Pineau A.
Published: December 2011

Both the initiation and the propagation of macroscopic creep cracks have been studied in 316-L austenitic stainless steel, and, for comparison purposes, in 2219-T851 aluminum alloy. These alloys are, respectively, creep-ductile and creep-brittle. This difference in behavior is explained in terms of fracture mechanics concepts applied to creeping solids. The inability of fracture mechanics in providing unique correlations with K, C*, etc. . . for all the stages of both creep crack initiation and propagation is pointed out. Life prediction schemes using local rather than global fracture criteria are presented. A model based on creep ductility exhaustion concepts and the stress fields obtained by fracture mechanics is shown to provide good predictions for 316-L. Finite element analysis coupled to continuum damage mechanics is found to describe creep crack initiation in 2219-T851.
Constitutive Modeling of 17-12 Mo SPH Stainless Steel Behavior at High Temperature
Authors: Blanchard P. , Lemoine P.
Published: December 2011

A systematic comparison of the detailed behaviors predicted by current constitutive models under various loadings and the actual behavior of austenitic steels under the same lodings was carried out. This comparison leads us to reject these models and to propose a new model whose predictions seem more realistic for these loadings: the unified multilayers model in which the material is represented by a composite of layers of various hardnesses. The details of the model are given in the paper.
The Effect of Flaw Shape on the Fracture Propensity of Nozzle Corner Flaws
Authors: Friedman E. , Jones D. P.
Published: December 2011

Three-dimensional finite element models were formulated to evaluate the distribution of the elastic stress intensity factor around the periphery of cracklike flaws postulated to exist at the corners of nozzles intersecting cylindrical shells. The effect of the assumed shape of the nozzle corner flaw on the distribution of the stress intensity factor along the crack front was determined in order to indicate where initiation of crack growth is most likely to occur and what shape the crack is most likely to take subsequent to stable crack growth. This is important because of the uncertainty associated with the flaw shape and its effect on crack growth in the nozzle corner region. Stress intensity factors computed from the nozzle corner flaw models were also compared with solutions evaluated using 1) a simplified procedure similar to that given in Section XI of the ASME Boiler and Pressure Vessel Code that makes use of the stresses calculated in the absence of the flaw, 2) the method recommended specifically for nozzle corner flaws in Section III of the ASME Code, and 3) a previously published empirical formula. The results of this paper confirm the adequacy of the simplified procedure for the analysis of nozzle corner flaws of different shapes.
Stress Analysis of Pressure Vessels With Uniformly Spaced Lugs
Authors: Mirza S. , Gupgupoglu K.
Published: December 2011

Stresses and displacements in circular cylindrical shells having square and rectangular lugs have been studied in this paper. The analysis presented here is based on finite element technique using 17-node doubly curved shell elements. Numerical computations have been performed for the case of longitudinal moments applied at discrete points around the circumference of the vessel. Four identical lugs uniformly spaced around a parallel have been considered. Results have been generated for several cases with different lug sizes and t/a ratios.
An Effective Method of Analyzing Rocking Motion for Unanchored Cylindrical Tanks Including Uplift
Authors: Ishida K. , Kobayashi N.
Published: December 2011

In order to calculate the rocking response of the unanchored cylindrical tank, including the bottom uplift due to seismic loading, a simple but effective method is developed. Firstly, an analysis model for the rocking response is presented; tank wall and liquid content are replaced with a mass-spring system, and the nonlinearity associated with the partial uplift of bottom plate is considered as the rotational spring of a bilinear type. The reliability of this analysis was illustrated by comparing the calculation results of resonance frequencies and rotation angles of tank models with the results of vibration tests. Secondly, a simple calculation method for obtaining the rocking responses of tanks from a few graphs without troublesome calculations is proposed. And lastly, some examples of applying the calculation for full-scale tanks are shown. It is clarified that the bottom plates of tall tanks with a capacity of a few thousand kiloliters are most likely to be uplifted by seismic loading.
Plastic Work Interaction Damage Rule Applied to Narrow-Band Gaussian Random Stress Situations
Authors: Lambert R. G.
Published: December 2011

Fatigue life estimates that use a structural material’s constant amplitude stress life data values and a linear cumulative damage rule are always nonconservative for stress histories containing numerous subcycles and only a few large-amplitude cycles. Conservative fatigue life estimates were previously achieved by others with a plastic work interaction damage rule using the material’s overstrain fatigue life parameter values. Verification fatigue tests were run on laboratory specimens of 1020 steel using four selected variable amplitude stress wave form profiles. This paper extends the application of the plastic work interaction damage rule to narrowband Gaussian random stress situations. The derived stress life mathematical expression is of a power law form. The predicted fatigue life is more accurate than that predicted using a conventional linear damage rule.
Suspension Bounce Response of Canadian MAGLEV Vehicle Under Guideway Excitations—Part I: Deterministic Analysis
Authors: Kotb M. , Sankar T. S. , Samaha M.
Published: December 2011

The dynamic bounce response of the Canadian designed high speed magnetically levitated vehicle is investigated when subjected to purely periodic excitations from the guideways. The equations of motion of the system are derived, on the basis of a realistic linear mathematical model, using d’Alembert’s principle of force and moment analysis. Solutions for the system responses in the time and frequency domain are obtained using numerical techniques. Although the main emphasis of this study is focused on the bounce response of the vehicle body as a measure of the ride quality of the vehicle, the vehicle pitching response as well as the bounce responses of the levitation magnets are also given appropriate attention.
Inplane Vibrations of Circular Rings With a Radially Variable Thickness
Authors: Lecoanet H. , Piranda J.
Published: December 2011

This paper gives some results on inplane vibrations of circular ring with a radially variable thickness. The problem is solved with the Galerkin method [1] making use of the eigenfunctions of a constant thickness ring. Good agreement is obtained between the approximate results and those of the exact calculus or experimental data.
Dynamics of a Deploying Orbiting Beam-Type Appendage Undergoing Librations
Authors: Lips K. W. , Modi V. J.
Published: December 2011

Vibration characteristics associated with a deploying spacecraft appendage in an arbitrary orbit are investigated numerically. In the beginning a rather general formulation of the problem is presented which accounts for the shifting center of mass, appendage offset, arbitrary variation of flexural rigidity along the appendage length, deployment acceleration, satellite librations, etc. The governing nonlinear, nonautonomous, and coupled equations are not amenable to any closed form solution. To gain some appreciation as to the character of the motion, the linearized equations are solved in a quasisteady fashion using the assumed mode procedure over a range of system parameters. Effects of pure flexure, spin, deployment, and orbital motion are isolated and their relative importance established. Although the deployment rate tends to introduce instability, it is the deployment related Coriolis loading which may lead to excessive displacements, particularly if the deployment time is too long. The information should prove particularly useful during the attitude acquisition phase when interactions between the control system, structural flexibility, and vehicle dynamics are particularly significant.
An Analysis of Elevator Rope Vibration in Tall Buildings
Authors: Blodgett R. E. , Majumdar A. K.
Published: December 2011

This paper addresses the problem of elevator compensation rope vibration in tall buildings. An analysis is made of the vibrations of a hanging rope, whose weight per unit length is not negligible, excited by an oscillation at the upper end and having a weight suspended from the lower end. The effect of introducing a damper at the upper end in order to limit the vibration is also examined.
The Effect of Approach Flow Direction on the Flow-Induced Vibrations of a Triangular Tube Array
Authors: Yeung H. C. , Weaver D. S.
Published: December 2011

Water tunnel experiments were conducted on an equilateral triangular array of tubes with a pitch ratio of 1.5. Eight tests were run with different array orientations so that the effects of incident flow direction on crossflow induced vibrations could be studied. Small amplitude vorticity response was observed for all orientations except the parallel triangular array. A Strouhal number of 0.57 based on pitch velocity and independent of incident flow directions was found. The fluidelastic threshold for the normal triangular array was found to be about twice that of the parallel triangular array. However, the stability threshold for the normal triangular array was found to be quite sensitive to incident flow direction suggesting that advantage of this higher threshold should not be taken in the design of heat exchangers.
Balancing of Flexible Rotors by the Complex Modal Method
Authors: Saito S. , Azuma T.
Published: December 2011

A new calculation method of the modal unbalance response for general flexible rotors in fluid film bearings has been developed by introducing the concept of modal exciting force vector into the usual complex modal method, and the physical meaning of the damping ratio at a critical speed is discussed. Next, application of this method, that correction weights can be determined in only one trial operation, is reported, and positions to measure vibration and to correct unbalance weight are discussed on the basis of the right eigenvector and the exciting factor mode, respectively. Lastly, it is shown by experiments that the proposed balancing method is of use for actual rotors.
What Research is Needed in Reliability and Failure Prevention in the Field of Anti-Earthquake Design of Industrial Facilities
Authors: Shibata Heki
Published: December 2011

This short article deals with the research needs of reliability and failure prevention in the field of anti-earthquake design of industrial facilities like nuclear power stations, oil refineries, and petro-chemical industries. The discussion will start from the current design flow and will look for the reliability concept in the flow. We usually put design margins everywhere in the design flow. And this design margin can be directly converted into the reliability failure, if we have appropriate data. The author examines the design parameters and tries to find what type of data is needed for this purpose. Next step is data collection of modes of failure which were observed in past destructive earthquakes. These data lead us to design checking points. Unless we have exact knowledge of how equipment, piping, vessels, and other installation failed, we can not design them nor evaluate failure probability of these items. The failure prevention procedure of such plants under destructive earthquake conditions has not been well established. In the case of earthquake engineering, this subject should involve failure prevention, failure detection during earthquake, and post-earthquake inspection after the event. One of the roles of reliability analysis in this field is evaluation of the overall probability of occurrence of plant disasters, like the Three Mile Island accident, under a certain level of destructive earthquakes. The author quickly reviews what data are needed for this purpose and what data are currently unavailable. The example will be taken fron nuclear power station study.
Single-Loaded Elastic Beams on Nonlinear Continuous Foundations
Authors: Kurajian G. M. , Na T. Y.
Published: December 2011

This paper is an extension of a recently published work [1] by the authors in that the mathematical formulations and accompanying solutions in the initial work are now further investigated and applied beyond the basic case in [1]. This study deals with the determination of the values of deformation and internal loads in “semi-infinitely long” elastic beams on nonlinear continuous foundations subjected to a concentrated load or a couple load, each placed either at the beam end or at a finite distance from the end. The analyst/designer will find useful the solutions presented for each of the loading cases treated, and for a representative range of foundation characteristics. Selected tables and curves are included.
Determination of Stress Concentration Around an Oblique Hole by a Finite-Element Technique
Authors: Li Hua-Ping , Ellyin F.
Published: December 2011

A plate weakened by an oblique penetration of a circular cylindrical hole has been investigated. The stress concentration around the hole is determined by a finite-element method. The results are compared with experimental data and other analytical works. Parametric studies of effects of angle of inclination, plate thickness, and width are performed. The maximum stress concentration factor (SCF) obtained from the finite-element analysis is higher than experimental results, and this deviation increases with the increase of angle of skewness. The major reason for this difference is attributed to the shear-action between layers parallel to the plate surface which cannot be directly included in the two-dimensional elements. An empirical formula is derived which accounts for the shear-action and renders the finite-element predictions in line with experimentally observed data.
The Application of Complex Variable Theory to Reinforcing Ring Design
Authors: Holland M. , Keavey M. A.
Published: December 2011

The complex variable method is applied to the analysis of a traditional constant-depth reinforcing ring as used on a pressurized single discontinuous bend (Fig. 1). It is shown that there is a “cross-over” point where complex variable theory and bending strain energy theory take over one from the other. This condition occurs when ring depth divided by the cylinders’ mean radius is approximately equal to 0.3. This criterion is of special interest since it falls within the range of factors used in industrial designs, i.e., the Mackenzie and Beattie bend [1] has a ratio of 0.29. Limitations of the complex variable theory are investigated with a detailed theoretical and experimental study of an internally pressurized prismatic elliptic cylinder having a circular bore (Fig. 2). Three bore sizes are investigated to gain knowledge of the convergent/divergent characteristics of the theory. For the largest bore size, numerical results show a definite divergence.
Investigation of Thermal Effects on Weapon System Components
Authors: Labra J. J.
Published: December 2011

A three-dimensional stress analysis of a 30-mm machine gun component on the Harrier Aircraft was conducted to investigate the cause of observed fractures. The analysis was made using a general purpose finite element computer program and a laboratory environmental test chamber. Based on this study, the probable cause of failure was identified and, as a result, the component manufacturer is considering possible design changes to alleviate this problem in further production. The study clearly demonstrates that computer-based technology can be successfully used in investigating causes of failure in complex structural components.
The Study of Dynamic Fracture Propagation Using a Special Finite Element Technique
Authors: Chan K. W. , Loo F. T. C.
Published: December 2011

An efficient finite element method has been developed for the computation of time-dependent stress intensity factors for cracks of Mode I deformation infinite bodies. Quarter point elements are used near the crack tip to approximate the theoretical singularity. Problems considered herein are: the stationary crack subjected to transient loading conditions, and the rapidly propagating crack. The advantages inherent in this method with regard to accuracy and savings in computational costs are discussed.
Contact Pattern Measurement by Means of Ultrasonic Waves: Art of Present and Some Improvements of its Performance
Authors: Ito Yoshimi , Itoh Shuzo
Published: December 2011

To understand the contact characteristics of a joint surface, it is necessary and indispensable to measure the contact pressure. There have, however, been very few contributions to the method of measuring the contact pressure when comparing it with other methods to detect the properties of engineering surfaces. The contact pressure measurement by means of ultrasonic waves (ultrasonic contact pressure measurement) is surely an effective method as ascertained by earlier works, and thus in this paper some improvements of its performance by using a focus type transducer have been reported, also referring to its art of the present. The measurement using a focus type transducer shows a fairly good characteristic as compared with that using a conventional transducer, especially from the aspect of the resolution ability of the contact pattern.
Suspension Bounce Response of Canadian MAGLEV Vehicle Under Guideway Excitations—Part 2: Stochastic Modeling and Analysis
Authors: Kotb M. , Sankar T. S. , Samaha M.
Published: December 2011

The investigation of Part I is extended to the case when the Canadian MAGLEV vehicle is subjected to a combination of periodic as well as dominant random disturbances from the guideways. Appropriate mathematical modeling of the input process is presented in terms of spectral density function which is further modeled as the output of a second order linear filter under a white noise input for easy analysis. The combined filter-vehicle stochastic equations are solved numerically and the suspension bounce acceleration behavior for different system parameters is presented.
A Computer Simulation of a True Position Feature Pattern Gage
Authors: O’Leary J. R.
Published: December 2011

Described in this paper is an approximate technique for the simulation of a mechanical feature pattern gage (a go/no-go gage). The procedure involves the unconstrained minimization of a judiciously constructed response function. The formulation of this function as well as the development of the associated algorithm are presented. Moreover, the technique is demonstrated on an assortment of sample problems.
Determination of AGMA Geometry Factor J for Slotted External Spur Gears
Authors: Singh Y. P.
Published: December 2011

This paper presents a direct method for determining the geometry factor J for slotted external spur gears. The location of maximum stressed point on the tooth profile where the stress parabola is tangent to the fillet curve has been determined by solving the resulting nonlinear equations using the sophisticated Newton-Raphson method. The semi-graphical procedure given in AGMA Standard [1] is not convenient for determining the geometry factory J of large gears used in grinding mill and kiln drives in the mining industry. Listing of the computer program and input-output point out for a typical application are presented.
Dynamic Stability of a Vibrating Hammer
Authors: Inoue J. , Miyaura S.
Published: December 2011

This paper deals with the stability of motion of an elastically suspended vibrating hammer that impacts upon an energy absorbing surface referring to the dynamical interaction between a vibrating hammer and a motor. Assuming an ideal source [1] of energy is characteristic of a motor, then the force mrω2 cosωt appears to be the vertical component of the inertia force of the mass m. The mass m is located the distance r from the axis 0 and rotates by frequency ω. Hence the basic equation of a vibrating system takes the form of a linear system. Fu [2] has investigated the regions of stability of the system as the linear system. In the case of practical use, however, a limited power source called a “nonideal source of energy” is the characteristic of a motor. Accordingly, it follows that the motion of an oscillating system with a nonideal source of energy may be formulated as a nonlinear system. The local stability of the sytem desired by a nonlinear equation is presented in our paper. Finally, the results of the regions of stability are compared with those studied in Fu.
An Efficient Technique for the Approximate Analysis of Vibro-Impact
Authors: Miller R. K. , Fatemi B.
Published: December 2011

An approximate solution procedure is presented for a class of steady vibro-impact problems consisting of adjacent structures separated by a gap and subjected to harmonic base excitation. The procedure is based on a weighted mean-square linearization technique, and is capable of substantial reduction of computational effort over that required for an exact numerical simulation. As an illustration of the general approach, a detailed analysis of an example problem is presented, together with a comparison of results with an exact solution. It is shown for the example problem that the level of accuracy of the approximate solution is adequate for many applications.
An Analytical and Experimental Study of the Acoustical Noise Produced by Machine Links
Authors: Dubowsky S. , Morris T. L.
Published: December 2011

Noise from high-speed machine systems is an important engineering design problem. This study investigates a recently developed analytical technique for calculating the noise generated by linkage-type machines based both on recently developed analytical methods for modeling the dynamic response of machines and on classical acoustical theory. This acoustical-dynamic modeling method is applied to an experimental system with elastic elements and clearance connections; the analytically predicted acoustical fields are compared to the measured noise. The results show excellent correlation between the experimental and analytical noise fields and support the validity of this modeling method.
Determination of Vibration Amplitudes and Stresses Using the Holography Interference Techniques and Finite Element Method
Authors: Fu Z. F.
Published: December 2011

A new method which combines the holography interference technique with the finite element method for determining the distribution of vibration amplitudes and stresses of gas turbine compressor blades is presented in this paper. In comparison with the ordinary electrical strain gage method, the present method has the advantage that there is no limitation to the number of measuring points and good results can be obtained even at high order modes.
Structural Damping by Slip in Joints
Authors: Je´ze´quel L.
Published: December 2011

The analysis of slip in riveted or bolted joints during harmonic excitation has been the subject of much research. However, in the case of plates the slip is induced by in-plane forces which do not appear in the classical linear plate theory. The aim of this study is to present a general formulation of this problem on the basis of Von Ka´rma´n’s equations and to propose a method of solution in the case of forced vibrations. It is based on the Krylov-Bogoliubov linearization method and on the notion of nonlinear modes. Its application in the case of circular plates revealed structural damping which justifies the use of linear hysteretic model.
A New Model of Local Elastic Deflections in Grinding
Authors: Saini D. P.
Published: December 2011

Mathematical models describing the deflection behavior of the wheel-work contact presented so far are based on the assumption that contact deflections are a direct function of the normal force on the wheel or the grains during grinding. This paper presents experimental results showing the evidence of a new mechanism of contact deflections due to the rotation of grain as a result of the tangential force component. In this perspective, a new model which considers the deflections due to both the normal and the tangential force is proposed and developed with the assumption of elasto-plastic deformation of the workpiece material around the grain during cutting. The model is shown to be consistent with experimental deflections obtained from single grain cutting on mild steel and EN25 steel specimens.
A Method for Recognizing Structural Nonlinearities in Steady-State Harmonic Testing
Authors: Kirshenboim J. , Ewins D. J.
Published: December 2011

A method for recognizing the extent of the nonlinearity of data acquired by the steady-state harmonic excitation methods is developed. The level of the nonlinearity is defined by a single parameter—the J factor—in the range 1–0 (1 for perfect linearity). An example of the application of the J factor is given.
The Use of Signal Analysis and Identification Methods for Correction of Unbalance Computations
Authors: Braun S. , Shulman D.
Published: December 2011

This paper describes a scheme for the correction of mass unbalance computations for the effect of torque disturbances. A general approach is dealt with, showing how to assess the disturbance of variables in monitoring schemes. Also described is a method to rank the disturbances according to their importance. The scheme makes use of conditioned signals, and mainly the multiple coherence function. An example dealing with a combustion engine test stand is given.
On the Critical Speed of Continuous Shaft-Disk Systems
Authors: O¨zgu¨ven H. Nevzat
Published: December 2011

The critical speed of a shaft-disk system can be approximately determined from a single degree-of-freedom model. The errors in the critical speed predictions obtained from such a model are investigated. The percentage errors are plotted against disk to shaft mass ratio for different bearings and various disk locations.
Study of Damped Critical Speeds and Damping Ratios of Flexible Rotors
Authors: Saito Shinobu , Someya Tsuneo
Published: December 2011

Influences of bearing damping on critical speeds of flexible rotors are investigated. First, the damped critical speed and the damping ratio of a uniform shaft supported at both ends are examined. It is shown that there exists an optimum bearing damping that gives the maximum damping ratio for each order of critical speed, and that with increasing support stiffness the optimum damping increases but the maximum damping ratio decreases. The meaning of critical speed map is discussed on the basis of the attainable maximum damping ratio. Next, the critical speed characteristics of a uniform shaft supported by three or four bearings are examined. Especially, for the case of 3-bearing-support, the relationship between the maximum damping ratio or the optimum bearing damping and the support stiffness is discussed. Finally, experiments to verify the existence of the optimum bearing damping are carried out for two cases of support stiffness using a test rotor supported by ball bearings and oil film damper bearings. The test results reveal that for each support stiffness there exists an optimum bearing damping, under which the vibration amplitude at the critical speed becomes minimum.
Finite Element and Modal Analyses of Rotor-Bearing Systems Under Stochastic Loading Conditions
Authors: Hashish E. , Sankar T. S.
Published: December 2011

A flexible rotor bearing system is represented in detail utilizing the state of the art finite element technique. The mathematical model takes into account the gyroscopic moments, rotary inertia, shear deformation, internal viscous damping, hysteretic damping, linear as well as nonlinear stiffness, and damping for the finite bearing and the bearing support flexibility. Using a simple Timoshenko element and recognizing an analogy between the motion planes, a procedure is given that requires a construction of only three symmetric 4×4 matrices. As an application, the different effects of the bearing lining flexibility and the bearing support flexibility on the rotor stability behavior is studied and discussed. The necessary relation for general modal analysis is simply restated and integrated into the conventional spectral approach, thus developing a simple procedure for the calculation of the stochastic response of a general rotor dynamic system. An application to a light rotor bearing featuring a general spatial support and subjected to random disturbances is illustrated.
Detection of a Misaligned Disk Coupling Using Spectrum Analysis
Authors: Dewell D. L. , Mitchell L. D.
Published: December 2011

This paper contains the development of the expected vibration frequencies for a misaligned metallic-disk flexible coupling based on the analysis of the structural vibrations produced by misalignment. Further, experimental results obtained through real-time spectrum analysis showing that all the theoretically predicted vibration frequencies are produced by a misaligned metallic-disk flexible coupling, but the 2× and 4× running speed components show the largest changes as misalignment increases.
Vibration Modes of Packeted Bladed Disks
Authors: Ewins D. J. , Imregun M.
Published: December 2011

This paper presents the results of investigating the vibrational behavior of turbine blades when grouped into packets. Two methods of analysis based on substructuring via receptance coupling have been developed and used with success to predict the natural frequencies of a 30-bladed disk with various packeting arrangements. A series of experiments have been conducted on a special testpiece to confirm these predictions. It is found that, unlike its continuously shrouded counterpart, the packeted bladed disk has modes which are always complex in shape, containing several nodal diameter components, a feature which can be predicted from the modal interference diagrams introduced in this work.
Stagger Angle Dependence of Inertial and Elastic Coupling in Bladed Disks
Authors: Crawley E. F. , Mokadam D. R.
Published: December 2011

The natural frequencies and mode shapes of nonrotating blade-disk-shaft systems have been experimentally and analytically investigated. Two mechanisms of blade motion coupling by the disk and shaft were investigated: inertial coupling by the rigid body motion of the disk on a flexible shaft; and out-of-plane elastic coupling due to disk flexure. A Ritz analysis was carried out which identifies the non-dimensional frequency and mass ratios which govern the blade-disk-shaft coupling. The mass ratios depend directly on the effective blade stagger angle. Estimates of these parameters were made for three typical rotors. Two experiments were performed which model these typical rotors. A single set of well-tuned flat blades was mounted on two different disks, one flexible and one rigid, which were in turn mounted on a flexible shaft. The blade-disk attachments were designed to allow for variations in the blade stagger angles. Experimental results show excellent agreement with simple analytical models derived by Ritz analysis. Data are reported in terms of nondimensional parameters. The results clearly show the strong dependence of the system coupling on the blade stagger angle and the blade-disk frequency and mass ratios.
Model Development and Statistical Investigation of Turbine Blade Mistuning
Authors: Griffin J. H. , Hoosac T. M.
Published: December 2011

This paper discusses the development of an efficient algorithm which calculates the individual blade response of a bladed turbine disk, the subsequent statistical investigation to establish mistuning dependencies, and procedures which reduce the increase in blade amplitudes caused by mistuning.
Resonant Vibration Levels of a Mistuned Bladed Disk
Authors: Ewins D. J. , Han Z. S.
Published: December 2011

Using a simplified but representative model for a mistuned bladed disk, a series of case studies has been made to examine in detail the influence of various parameters on the resonant response levels of each blade on the disk. Although confined to a specific model of a 33-bladed disk, and thus not attempting to generalize its results, the study examines systematically the importance of individual blade mistune, precision of individual blade data, position in an arrangement, and type of arrangement. It is found that mistuning always causes a deterioration in the vibration environment in that the maximum response is always increased, although the extent of this worsening varies over quite a wide range. In this study, a blade with an extreme of mistune is always found to suffer the highest response levels.
Coupling Technique of Rotor-Fuselage Dynamic Analysis
Authors: Tang D. M. , Wang M. Q.
Published: December 2011

In this paper is introduced a method of dynamic analysis of the helicopter rotor coupled with fuselage in the rotating plane. The method has been used to determine the inplane rotor-fuselage dynamic properties of a light helicopter with fiberglass-reinforced plastics rotor blades. This paper makes particular reference to the effect of anisotropic dynamic stiffness of the rotor shaft end of fuselage on the natural dynamic characteristics.
Optimal Design of an Off-Road Motorcycle Suspension
Authors: van Vliet M. , Sankar S.
Published: December 2011

In this paper an optimal design is proposed which can be used by the suspension designer to maximize the performance of a given motorcycle suspension. The subject matter is developed by presenting an analytical model of the suspension. A digital simulation is performed in both the frequency and time domains. A set of performance criteria is established based on the results obtained in both the time and frequency domains. Objective functions are formulated based on the performance criteria and the range of input values. A numerical optimization technique is used to calculate the optimal parameters. The results are plotted and presented in tables. The optimized results are verified by experiment and conclusions are drawn.
A Coupled Structural-Acoustic Finite Element Model for Vehicle Interior Noise Analysis
Authors: Sung S. H. , Nefske D. J.
Published: December 2011

An analytical method is developed for predicting vehicle interior noise and identifying noise sources. In this method, the finite element models representing the vehicle structure and its enclosed acoustic cavity are coupled mathematically. A modal formulation is employed to solve for the interior acoustic response, and an analysis is developed to identify the structural and acoustic modal participation as well as the boundary panel participation in producing the response. As an example application, a coupled model of an automotive vehicle is presented and experimentally evaluated. The modal and panel participations are identified from the results.
The Influence of Surface Compliance on the Production of Sound by a Turbulent Boundary Layer
Authors: Howe M. S.
Published: December 2011

The theory of aerodynamic sound in the form developed by Ffowcs-Williams and Hawkings [15] is applied to investigate the production of sound by turbulent boundary layer flow over a thin, flexible plate. Conventional theories of bounday layer noise attribute the radiation to the boundary layer quadrupoles and their (passive) images in the plate, and neglect the interaction of turbulence with the finite amplitude motion of the plate caused by the wall pressure fluctuations. This interaction generates sound whose intensity is characteristic of aerodynamic sources of dipole type. In (underwater) situations involving the high fluid loading of steel plates, it is shown that the intensity of the dipole noise may be comparable to that produced by the quadrupoles. The dipoles dominate the radiation from more compliant surfaces, of the type commonly used in experiments on compliant wall drag reduction, and it is suggested that the injudicious deployment of compliant wall coatings may result in the production of unacceptably high levels of aerodynamic noise.
An Electret Loudspeaker for Active Acoustic Systems
Authors: Guicking D. , Albrecht M.
Published: December 2011

A push-pull electret loudspeaker has been developed which can be used for an active acoustic wall lining.
Application of the BIE Method to Sound Radiation Problems Using an Isoparametric Element
Authors: Seybert A. F. , Soenarko B. , Rizzo F. J. , Shippy D. J.
Published: December 2011

This paper discusses the application of the Boundary Integral Equation method for the numerical solution of radiation problems governed by Helmholtz’s equation. In particular, we introduce an isoparametric element formulation in which both the surface geometry and the acoustic variables on the surface of the radiating body are represented by quadratic shape functions within the local coordinate system. A general result for the surface velocity potential is derived. This result includes the case where the surface may have a nonunique normal (e.g., at the edge of a body). The Boundary Integral Equation Method is used to obtain numerical solutions for three radiation problems involving spherical and cubical geometry. The numerical results are compared with exact analytical solutions. The problem of nonuniqueness of the solution at certain frequencies equal to the eigenfrequencies of the corresponding (but physically unrelated) interior problem is illustrated.
Vortex Shedding: The Source of Noise and Vibration in Idling Circular Saws
Authors: Leu M. C. , Mote C. D.
Published: December 2011

Vortices separating from the edges of cutting teeth were shown to be the dominant source of pressure fluctuation and hence noise in circular saws. Measurement of pressure on the surfaces of the blade and teeth showed: (1) strong periodicity of the pressure on the tooth lateral surfaces, (2) a 180 degree phase difference between the pressure variations on both tooth lateral surfaces, and (3) pressure variations dominantly occurring on the tooth surfaces rather than the blade surfaces. The presence of an afterbody, downstream of the blade and tooth edges of flow separation, was found necessary for significant aerodynamic excitation of the blade and generation of noise by the flow.
On a Broader Definition of Machine Failure
Authors: Sevart J. B.
Published: December 2011

The purpose of this paper is to direct the attention of machine designers to a concept of “failure” which is far more inclusive than mechanical failures. For all machines used by man there are three general criteria that must be simultaneously met. These are function, affordability, and the human element. Failure of a design in any one of these criteria can result in a defective design and can have an adverse impact on society. The paper challenges the designer to prevent these failures and presents basic concepts for doing so.
Probabilistic Design Criteria for Cylinders and Spheres Under Thermal Stresses
Authors: Smith C. O.
Published: December 2011

Cylinders and spheres are often used to contain hot or cold fluids. A temperature gradient across the vessel wall results in thermal stresses. This paper presents equations for means and standard deviations of thermal stresses developed in cylinders and spheres. Inherent in these equations are the facts that: (a) design variables are generally characterized by spectra of values, and (b) a small, but finite probability of failure must be recognized in any design. By coupling the stresses due to a thermal gradient as calculated by the equations in the paper with the strength available in a material, reliability (or the alternative probability of failure) can be calculated. Conversely, for a specified reliability the appropriate size or heat flux can be determined. Appropriate illustrations of application of these equations are provided by tables and figures. The difficulty of relying on a factor of safety is demonstrated.
Allocation of Spring Tolerances
Authors: Rao A. C.
Published: December 2011

A rational method for allocating the tolerances on wire and coil sizes of helical springs is presented. Allocation of the tolerances on breadth, thickness, and length of a flat spring is also considered. Example problems are included and interesting conclusions are drawn.
Differentiating Rotor Response Due to Radial Rubbing
Authors: Beatty R. F.
Published: December 2011

Among the factors leading to destructive instability of rotors in high-speed, high-performance turbomachinery is excessive rubbing between rotating and stationary parts. Although in many designs this is intentional, such as tight-fitting turbine tip seals, uncontrolled contact can be disastrous. This paper proposes a mathematical rationale of rubbing identification; defines the limits between benign contact and the initiation of a destructive instability based on harmonic spectral data; correlates the results with industry experience, published findings, and extensive laboratory tests; and details the response format of diagnostic data in actual cases. This detection methodology aids in making practical testing decisions based on a reliable indication of the operating condition. Criteria are presented to infer rubbing related to simple unbalanced response and to differentiate it from bearing deadband effects.