bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rotor Whirl Forces Induced by the Tip Clearance Effect in Axial Flow Compressors
Authors: Ehrich Fredric 
Published: March 2021

Abstract
It is now widely recognized that destabilizing forces, tending to generate forward rotor whirl, are generated in axial flow turbines as a result of the non-uniform torque induced by the non-uniform tip-clearance in a deflected rotor — the so called Thomas/Alford force (Thomas, 1958 and Alford, 1965). It is also recognized that there will be a similar effect in axial flow compressors, but qualitative considerations cannot definitively establish the magnitude or even the direction of the induced whirling forces — that is, if they will tend to forward or backward whirl.
Applying a “parallel compressor” model to simulate the operation of a compressor rotor deflected radially in its clearance, it is possible to derive a quantitative estimate of the proportionality factor β which relates the Thomas/Alford force in axial flow compressors (i.e., the tangential force generated by a radial deflection of the rotor) to the torque level in the compressor. The analysis makes use of experimental data from the GE Aircraft Engines Low Speed Research Compressor facility comparing the performance of three different axial flow compressors, each with four stages (typical of a mid-block of an aircraft gas turbine compressor) at two different clearances (expressed as a percent of blade length) — CL/L = 1.4% and CL/L = 2.8%.
It is found that the value of β is in the range of +0.27 to −0.71 in the vicinity of the stages’ nominal operating line and +0.08 to −1.25 in the vicinity of the stages’ operation at peak efficiency. The value of β reaches a level of between −1.16 and −3.36 as the compressor is operated near its stalled condition. The final result bears a very strong resemblance to the correlation obtained by improvising a normalization of the experimental data of Vance and Laudadio (1984) and a generic relationship to the analytic results of Colding-Jorgensen (1990).
Improved Rotordynamic Unbalance Response Calculations Using the Polynomial Method
Authors: Murphy Brian T. 
Published: March 2021

Abstract
For rotordynamic calculations the conventional transfer matrix (CTM) method is known for its ease of application and speed of execution. This is true for eigenvalue analyses as well as forced response calculations. In 1983, Murphy and Vance significantly improved the conventional transfer matrix method for eigenvalues by developing Polynomial Transfer Matrix (PTM) method. For eigenvalue calculations this resulted in one to two orders of magnitude increase in calculation speed, and eigenvalues could be found without missing any modes. This paper extends the polynomial method to forced response calculations. The polynomial method “compiles” a polynomial representation of a rotor bearing system. Responses at many frequency increments can then be computed with amazing rapidity. Similar to the case of eigenvalue calculations, an automatic dynamic condensation feature helps the PTM attain nearly a tenfold increase in speed over the CTM method. This paper details the polynomial method applied to forced response calculations. Two example calculations are presented to compare the PTM to the CTM method and finite element method. All computations were carried out on an IBM-PC compatible computer.
A Theoretical and Experimental Investigation of a Gas Operated Bearing Damper for Turbomachinery: Part I — Theoretical Model and Predictions
Authors: Sundararajan Padmanabhan , Vance John M. 
Published: March 2021

Abstract
This is the first (Part I) of two papers describing recent results of a research program directed at developing a vibration damper suitable for high temperature turbomachinery applications. It is expected that such dampers will replace squeeze-film dampers that use oil as the working fluid and have limitations at higher temperatures. A novel gas operated bearing damper has been analytically and experimentally evaluated for its damping characteristics. Theory that is based on the isentropic assumptions predicts the damper performance characteristics reasonably well. A maximum damping level of 13.2 lb-s/in at a frequency of 100 hz was measured with a single actuator of the gas damper and, since many such actuators can be placed circumferentially around the squirrel cage, considerable damping levels can be realized. The study also shows that significantly higher damping levels can be achieved by modifying the current design.
Part I describes the theoretical model that has been developed based on isentropic assumptions. This model is an improved version of the previous theory [1,2] and includes the supply groove effects, dynamic area changes of the inlet feeding holes and the effects of flow choking on damper behavior. The governing equations are derived and theoretical predictions using these equations have been made for the three hardwares that were experimentally investigated (see Part II).
Asymmetrical Rolling and Self Excited Vibrations in a Hot Roughing Mill
Authors: Jafari A. A. , Tieu A. K. , Basu A. 
Published: March 2021

Abstract
This paper discusses the simulation of self excited torsional vibration of rolling mill drives and vertical vibration of a Horizontal Mill taking into account asymmetrical rolling. The influence of the mass, rigidity and damping of the hot steel slab have been considered in the simulation of asymmetrical self excited vibrations.
Isotropic Control of Rotor Bearing System
Authors: Kim Cheol-Soon , Lee Chong-Won 
Published: March 2021

Abstract
A new rotor control scheme, the isotropic control of anisotropic rotor bearing system in complex state space, is proposed, which utilizes the concepts on the eigenstructure of the isotropic rotor system. Then the control scheme is applied to an active magnetic bearing system and the control performance is investigated in relation to control energy, transient response, and unbalance response. In particular, it is shown that the proposed method is efficient for control of unbalance response.
An Integrated Approach Toward the Dynamic Analysis of High-Speed Spindles: Part II — Dynamics Under Moving End Load
Authors: Chen C. H. , Wang K. W. 
Published: March 2021

Abstract
This paper presents an integrated study of a rotor/bearing structure, with specific interests toward high speed spindle systems under rotating end loads. Considering the coupling between the rotating shaft and the nonlinear bearings, an iterative method is developed to derive the system equilibrium configuration for given operating conditions. With moving end loads, structural instability caused by high rotational speed is analyzed. The critical speeds and unstable speed regions are discussed. Machining chatter instability lobes are also derived using the spindle model. It is shown that significant errors will occur in predicting spindle characteristics and stability if the speed and load effects on the shaft/bearing dynamics are neglected.
Transfer Function Analysis of Non-Uniformly Distributed Parameter Systems
Authors: Yang Bingen , Fang Houfei 
Published: March 2021

Abstract
This paper studies a transfer function formulation for general one-dimensional, non-uniformly distributed systems subject to arbitrary boundary conditions and external disturbances. The purpose is to provide an useful alternative for modeling and analysis of distributed parameter systems. In the development, the system equations of the non-uniform system are cast into a state space form in the Laplace transform domain. The system response and distributed transfer functions are derived in term of the fundamental matrix of the state space equation. Two approximate methods for evaluating the fundamental matrix are proposed. With the transfer function formulation, various dynamics and control problems for the non-uniformly distributed system can be conveniently addressed. The transfer function analysis is also applied to constrained/combined non-uniformly distributed systems.
Design Optimization of Aircraft Engine-Mount Systems
Authors: Ashrafiuon Hashem 
Published: March 2021

Abstract
Design optimization of aircraft engine-mount systems for vibration isolation is presented. The engine is modeled as a rigid body connected to a flexible base representing the nacelle. The base is modeled with mass and stiffness matrices and structural damping using finite element modeling. The mounts are modeled as three-dimensional springs with hysteresis damping. The objective is to select the stiffness coefficients and orientation angles of the individual mounts to minimize the transmitted forces from the engine to the base. Meanwhile, the mounts have to be stiff enough not allowing engine deflection to exceed its limits under static and low frequency loadings. It is shown that with an optimal system the transmitted forces may be reduced significantly particularly when mount orientation angles are also treated as design variables. The optimization problems are solved using a Constraint Variable Metric approach. The closed form derivatives of the engine vibrational amplitudes with respect to design variables are derived in order to achieve a more effective optimization search technique.
Development of a Recursive Frequency Based Filter With Application to Chatter Control
Authors: Ousterhout Karl B. 
Published: March 2021

Abstract
In most machining processes, large amounts of energy are needed to accomplish the machining operation. When this energy is transmitted through a structure that has minimal damping characteristics, such as a lathe or a milling machine, self sustained oscillations (chatter) can develop. When chatter develops, it can be viewed as a basic performance limitation of the machine tool. In order to suppress the chatter, a real-time controller using digital signal processing techniques has been implemented. This paper discusses a novel way of computing the transfer function of the machine tool-work piece combination and illustrates how a real-time active chatter controller could be designed and integrated into existing machine tools to overcome this performance limitation. Currently, experimental verification of the analytical work is being pursued.
Semiactive Control of Structural Vibrations
Authors: Patten W. N. , Wu H. C. , Yan W. , Sack R. L. , Kuo C. C. , Shen K. 
Published: March 2021

Abstract
Structural control can be used to mitigate dynamic structural response and prevent structures from reaching their limit states. Typical active vibration systems utilize large electric motors, and expensive hydraulic pumping equipment to provide force inputs to a structure during a dynamic event. The work here explores the effectiveness of low power, inexpensive semi-active control hardware to provide vibration attenuation, for structures. While there are a number of electro-mechanical devices that might provide semi-active control forces, the investigation here analyzed the use of an automatically adjustable hydraulic actuator (i.e., a shock absorber). The variation in damping characteristics is accomplished by using variable orificing. While semi-active hydraulic actuators are a relatively cheap means of providing smart damping for a structure, the development of effective closed loop control strategies for these devices is not a completely resolved issue. The paper develops a dynamic model of a semi-active actuator. Two inner loop controllers are then suggested, for the operation of the actuator. The control of a simple structure is then simulated. The paper closes with a comparison of the performances between a semi-active (clipped optimal) control and active control of a three story structure that is subject to an earthquake.
Balancing of High Speed Flexible Overhung Rotor: A Case Study
Authors: Kamala V. 
Published: March 2021

Abstract
This paper presents a case study of balancing a high speed overhung flexible rotor system. The system had several speeds, below the operating speed, where the amplitude of vibration was high. Mode shapes were obtained by measuring amplitude of 1X component and its phase at various locations & balancing was carried out by adding weights in a single plane.
Development of a Houde Damper Using Magnetic Damping
Authors: Kobayashi H. , Aida S. 
Published: March 2021

Abstract
This paper presents experimental results that demonstrate the vibration suppression effectiveness of a Houde damper, a type of dynamic absorber that contains an auxiliary mass and a damping element. The damper that was developed uses an eddy current brake consisting of a pair of permanent magnets and a copper plate which acts as a conductor. A vibration test using a straight piping model was used to show that the Houde damper is effective not only in reducing small amplitude vibrations, but large amplitude vibrations as well. Analytical calculations were used to establish that the precise tuning required for effective vibration suppression using a conventional dynamic absorber (that is, a passively tuned mass damper) is not necessary for the Houde damper.
Reduction of Precision Spindle Vibration by Radial Shear-Layer Damping
Authors: Huang E. E. , Lieu D. K. 
Published: March 2021

Abstract
A damping technique is proposed as a simple method for reducing non-repeatable radial runout (NRR) in magnetic disk file assemblies. Using finite element methods, the behavior of a typical system is investigated using eigenvalue and steady state response analyses to assess the benefits and shortcomings of the proposed technique. Simple impact response experiments are then performed to verify the analytical results. It is seen both in the numerical analysis and experimentation that the overall magnitudes of the radial response can be reduced using the proposed technique, and topics for continued investigation of the subject are discussed.
Free Vibration of Rectangular Membranes With Linearly Varying Tension and Light Flexural Rigidity
Authors: Gorman D. J. 
Published: March 2021

Abstract
The proposal to utilize tensioned rectangular membranes as antennae in interspace communication has resulted in the focus of considerable attention on the free vibration of membranes with complicated in-plane loadings. In this paper the problem of analizing the vibration of a rectangular membrane with linear variation in tension in one direction is examined. This tension variation occurs due to gravitational forces when the membranes are tested experimentally in vibration laboratories. The Rayleigh-Ritz energy method is employed to obtain analytical results. Convergence is found to be rapid. Mode shapes are compared with those of known classical solutions when no tension variation is permitted. Generation of the eigenvalue matrix is demonstrated to be a very simple task.
Measurement of Static and Dynamic Properties of a Tilting Pad Bearing and Comparison With Theory
Authors: Bonner Thomas , Vohr John H. 
Published: March 2021

Abstract
Measurements were made of the static and dynamic properties of a seven inch diameter, four-pad, tilting pad bearing with both centrally pivoted and 60% offset pads. Data was recorded at 1500, 1800 and 3000 RPM and covered a range of Sommerfeld numbers from .055 to .625. Dynamic properties were measured by applying unbalance weights of various magnitudes to the rotor and measuring the synchronous response amplitudes and phase angles. Good agreement was obtained between measured properties and those predicted using linearized stiffness and damping coefficients obtained from isoviscous lubrication theory.
Symmetric Model Correction of Mechanical Systems
Authors: Lam Marca , Inman Daniel J. , Kress Andreas 
Published: March 2021

Abstract
This work examines the model updating problem for simple nonconservative proportionally damped systems. Model correction, also called model updating, refers to the practice of adjusting an analytical model until the model agrees with measured modal data. The specific case examined here assumes that natural frequencies and modal damping ratios are available from vibration tests and that the measured data disagrees in part with the modal data predicted by an analytical model. Most model correction schemes tend to produce updated damping and stiffness matrices which are asymmetric. The simple method presented here focuses on retaining the desired symmetry in the updated model.
Fractal Dimensions in Elastic-Plastic Beam Dynamics
Authors: Symonds P. S. , Lee Jae-Yeong 
Published: March 2021

Abstract
The final midpoint displacement of a two-degree-of-freedom beam model subjected to a short pulse of transverse loading may be either in the direction of the initial impulse or in the opposite (“negative”) direction, when moderately small plastic deformations occur. In the range where chaotic vibrations occur, the result depends with great sensitivity on the impulse magnitude. Considering a pulse of duration 0.5 × 10−3 sec, 100 calculations have been made for pulse forces P starting at 2500 N and increasing by increments of 2.0, 10−2, 10−4, and 10−6 N. It is found that the proportion and distribution of negative final displacements remain, on average, the same, independent of the size of the force increment. A fractal dimension representing a self-similarity property is calculated for the four choices of the force increment, and is found to be approximately 0.78 in each case. A correlation fractal dimension is also computed for undamped responses.
A Case Study on Concurrent Design
Authors: Guo Wei , Cha Jianzhong , Xue Qiang , Si Liming 
Published: March 2021

Abstract
Based on the methodology and theory proposed in (Cha and Guo, 1993) for automated concurrent design process, this paper presents a concrete engineering case practice to illustrate how to establish a descriptive model and a cognitive model for concurrent design process, as well as how to develop a computable model for the computer system to implement the automated concurrent design process. Also, a special emphasis is given to the aspects of management, control and coordination on concurrent design process, which is considered as key techniques for automated concurrent design system.
Issues in Product Life Cycle Engineering Analysis
Authors: Lee David E. , Melkanoff Michel A. 
Published: March 2021

Abstract
Traditional engineering analysis of product designs has focused primarily on a product’s operational performance without considering costs of manufacturing and other stages downstream from design. In contrast, life cycle analysis of a product during its initial development can play a crucial role in determining the product’s overall life cycle cost and useful life span. This paper examines product life cycle engineering analysis - measurement of product operational performance in a life cycle context. Life cycle engineering analysis is thus considered both as an extension of traditional engineering analysis methods and as a subset of a total product life cycle analysis. The issues critical to life cycle engineering analysis are defined and include product life cycle data modeling and analysis, analysis tools and their performance regimes, performance tradeoff measurement and problems of life cycle engineering analysis in an organizational context. Recommendations are provided for future research directions into life cycle engineering analysis in the context of integration architectures for concurrent engineering.
Hierarchical Selection in Gas Turbine Maintenance Management
Authors: Chen Wei , Allen Janet K. , Mistree Farrokh 
Published: March 2021

Abstract
A concurrent approach to hierarchical selection of design concepts for maintenance management is introduced. The interactions amongst selection problems in maintenance are taken into account concurrently by formulating an entire hierarchy as a single coupled Decision Support Problem (DSP). Using this method it is possible to model interactions among different concepts rather than creating a model in which these decisions are made sequentially, hence this approach can form a basis for concurrent engineering. We illustrate our approach by formulating and solving a gas turbine axial compressor fouling maintenance problem as a coupled selection-selection DSP. The filter for fouling prevention and the washing media for fouling treatment are selected simultaneously while interactions between the two selections are considered. Our focus in this paper is on explaining our approach rather than the results per se.
A General Multi-Body Dynamic Model to Predict the Behavior of Roller Chain Drives at Moderate and High Speeds
Authors: Kim Mahn Shik , Johnson Glen E. 
Published: March 2021

Abstract
An advanced model in which most important factors of the roller chain drive are considered is developed. Most importantly, for the first time the series of elastic collisions and rebounds that occur as the chain links engage the sprocket is modeled here. Equations of motion are derived in a form very efficient for numerical solution by applying Kane’s method. The equations of motion are programmed and used to simulate responses of dynamic roller chain drives.
The dynamic behavior of roller chain drives at moderate and high speeds is studied. Comprehensive observations about the engagement process are presented and discussed. The influence of impact due to collision is investigated. The effects of the center distance and the operation speed on the dynamic behavior of the roller chain are studied, with special attention to the trajectory of the roller chain, the phase between disengagement and engagement, and the transverse vibration.
Abstraction As a Configuration Design Methodology
Authors: Snavely Gary L. , Papalambros Panos Y. 
Published: March 2021

Abstract
Configuration design can be thought of as a process of generating artifacts by assembling pre-defined components. This paper introduces a method for reducing the size of configuration problems by abstracting components to higher levels of abstraction. At higher abstraction levels, less important detail is temporarily ignored, and each component represents a family of lower-level components. Configuration is then performed at the highest level, explicitly enumerating all configurations at that level. Any complete configuration at the highest level is recursively instantiated to lower levels. At the same time, any incomplete configuration at the highest level is eliminated, thereby eliminating all possible lower-level instantiations of that configuration. In this manner, all configurations of components at the lowest level of abstraction are implicitly enumerated.
FRODO: Constraint-Based Object-Modeling for Preliminary Design
Authors: Kolb Mark A. , Bailey Michael W. 
Published: March 2021

Abstract
Computer support of design analysis tasks is a key element in improving the productivity of design engineers. This undertaking is particularly difficult for preliminary design, where products are constantly evolving and therefore the required analyses change. Furthermore, because preliminary design requires quick turnaround, engineers must often rely on special-purpose analysis codes developed in-house by the engineers themselves. Thus, a computer tool for integrating such codes to support multi-disciplinary design must provide flexibility. The work presented here attempts to meet this requirement by combining object-oriented modeling with constraint propagation. Object-oriented techniques are intended to provide the modeling flexibility needed for preliminary design, while constraint propagation is a flexible means for integrating and performing mathematical analyses. The utility of this approach is demonstrated by its application to aircraft engine preliminary design. Current work in coupling the modeling software to a generic optimization package is also discussed.