bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of Combustion Chamber Leakage for the Maintenance of Four Stroke Marine Diesel Engines
Authors: Mollah M. A. Hossain 
Published: November 2020

Abstract
Maintenance is becoming increasingly an important element in the upkeep of the modern complex equipment. There are a number of approaches to the maintenance of the equipment such as the break down maintenance and preventive maintenance. Marine diesel engines require proper maintenance to ensure their efficient, safe and trouble-free operation. The preventive maintenance task that is most useful for reducing the overall maintenance, is also known as on-condition maintenance, condition-directed maintenance, or predictive maintenance. This is done by measuring some parameter over time where it has been established that parameter correlates well with the incipient failure conditions. This paper contains the studies of the evaluation of combustion chamber leakage of four stroke marine diesel engines by using a diagnostic device. It describes the methodology to develop the performance limits of the combustion chamber leakage of marine diesel engine and the method of evaluating the condition of diesel engines. The results of model tests of the diagnostic device, Pneumatic Indicator, are also reported. The proposed methodology allows performing the evaluation of the technical condition of a cylinder piston group of marine engines both qualitative and quantitative. Thus the maintenance and repairing works may be performed according to the real condition of the engine, which is extremely useful in decreasing the overall maintenance cost.
Mechanical Noise Identification Using Time-Frequency Representations
Authors: Pan Min-chun 
Published: November 2020

Abstract
Three computation schemes of time-frequency representations (TFRs) have been developed and implemented to identify different components of mechanical noise originated from the transmission system of electrical vehicles.
This study explores the close relationships between three TFRs, i.e. the spectrogram based on windowed Fourier transform (WFT), the Wigner-Ville distribution (WVD), and the smoothed WVD (SWVD). One main purpose is to pursue the efficiency of computing the SWVD of a dynamic signature. The revised scheme can tremendously reduce the computation time to a scale of around 1/90, compared with the original scheme.
To assess the validation of these TFR schemes, firstly, four synthetic signals are designed and processed. Secondly, the developed TFRs are applied to distinguish different spectral components of transmission noise, and identify their sources. This study takes an electrical scooter with a continuous velocity transmission (CVT) system as a test bench. The CVT-belt noise, helical-gear whine noise, and fan noise can be clearly identified via the processing of the TFRs. These obtained conclusions can be used as references for machine element modification to improve annoying noise.
A Time-Frequency Envelope Estimation Method for Detection of Bearing-Localized Defects
Authors: Nikolaou Nikolaos G. , Antoniadis Ioannis A. 
Published: November 2020

Abstract
This paper proposes a new method for the estimation of the envelope of signals resulting from rolling element bearing-localized defects, based on the use of a shifted Morlet wavelet family. Using a time-frequency representation of the signal, the method is designed in a way that can exploit the underlying physical concepts of the modulation mechanism, present in the vibration response of bearings with localized defects. Systematic selection criteria for the automated choice of the critical parameters that characterize the Morlet wavelet family are used. The method is evaluated by using actual vibration signals measured from bearings with defects at different locations.
A New Sparse Solver for Kinematics Simulation of Multibody Systems in Natural Coordinates Based on Tearing Methods
Authors: Funes Francisco Javier , Jiménez José Manuel , Rodríguez José Ignacio , de Jalón Javier García 
Published: November 2020

Abstract
This paper presents a new method for the factorization of the sparse system of linear equations arising from the kinematic simulation of multibody systems using natural coordinates. A special reordering of the jacobian matrix of the mechanism constraint equations will be described. This reordering depends only on the topology of the mechanism. In open-chain systems the matrix can be reordered to a block triangular form. For closed-loop systems this matrix can take a bordered block triangular form, with very few columns in the border. A modification of the Harwell’s implementation of the P5 algorithm from Erisman et al. [1] is used for reordering the rows and columns of the matrix. A new method of factorization is described. This method reduces the number of floating-point operations and the fill-ins. An efficient way for solving the least-squares problem arising from over-determined systems is explained.
Contact Dynamics of Reconfigurable Space Systems With Numerical Verification Method
Authors: Takahashi Takashi , Matunaga Saburo 
Published: November 2020

Abstract
In order to analyze dynamics of space systems, such as cluster satellite systems and the capturing process of damaged satellites, it is necessary to consider such space systems as reconfigurable multibody systems. In this paper, we discuss the numerical computation of the dynamics of the ground experiment system to simulate the capturing and berthing process of a satellite by a dual-manipulator on the flat floor as an example. We have previously discussed the efficient dynamics algorithm for reconfigurable multibody system with topological changes. However, the contact dynamics, which is one of the most difficult issues in our study, remains to be discussed. We introduce two types of the linear complementarity problem (LCP) concerned with contact dynamics. The difference between the two types of LCP is whether impacts can be considered. Dynamic systems with impacts and friction are non-conservation systems; moreover the LCP is not always solvable. Therefore we must check if the solutions of the numerical computation are correct, or how accurate they are. In this paper, we derive the method of numerical computation with guaranteed accuracy of the LCP for contact dynamics.
Improved “Order-N” Performance Algorithm for the Simulation of Constrained Multi-Rigid-Body Dynamic Systems
Authors: Anderson Kurt S. 
Published: November 2020

Abstract
This paper presents an algorithm for the efficient numerical analysis and simulation of modest to heavily constrained multi-rigid-body dynamic systems. The algorithm can accommodate the spatial motion of general multi-rigid-body systems containing arbitrarily many closed loops in O(n + m) operations overall for systems containing n generalized coordinates, and m independent algebraic constraints. The presented approach does not suffer from the performance (speed) penalty encountered by most other of the so-called “O(n)” state-space formulations, when dealing with constraints which tend to actually show O(n + m + nm + nm2 + m3) performance. Additionally, these latter formulations may require additional constraint violation stablization procedures (e.g. Baumgarte’s method, coordinate partitioning, etc.) which can contribute significant additional computation. The presented method suffers less from this difficulty because the loop closure constraints at both the velocity and acceleration level are directly embedded within the formulation. Due to these characteristics, the presented algorithm should offer superior computing performance relative to other methods in situations involving both large n and m.
Velocity Transformation Matrix of a Revolute-Spherical Massless Link
Authors: Yoo Wan-Suk , Sohn Jeong-Hyun , Lim O-kaung , Hong Keum-Shik 
Published: November 2020

Abstract
Since the contribution of lightweight components in the total energy of a system is small, the inertia effects are sometimes ignored via replacing them to massless links. A massless link, which is sometimes called as a composite joint, connects two adjacent bodies keeping the relative degrees of freedoms. For a revolute-spherical massless link, one edge is connected to an adjacent body with a revolute joint and the other edge is linked to another body with a spherical joint. Using velocity transformation technique, it is possible to combine the generality of Cartesian coordinates in modeling and the efficiency of relative coordinates in simulation. In this paper, velocity transformation matrix of a revolute-spherical massless link is formulated and implemented as a joint module in a vehicle dynamic analysis program. Numerical examples are presented to verify the formulation.
On the Modeling of Shells in Multibody Dynamics
Authors: Bauchau Olivier A. , Choi Jou-Young , Bottasso Carlo L. 
Published: November 2020

Abstract
Energy preserving/decaying schemes are presented for the simulation of the nonlinear multibody systems involving shell components. The proposed schemes are designed to meet four specific requirements: unconditional nonlinear stability of the scheme, a rigorous treatment of both geometric and material non-linearities, exact satisfaction of the constraints, and the presence of high frequency numerical dissipation. The kinematic nonlinearities associated with arbitrarily large displacements and rotations of shells are treated in a rigorous manner, and the material nonlinearities can be handled when the constitutive laws stem from the existence of a strain energy density function. The efficiency and robustness of the proposed approach is illustrated with specific numerical examples that also demonstrate the need for integration schemes possessing high frequency numerical dissipation.
Study on Derivation and Application of Mean Axis for Deformable Beam by Means of the Absolute Nodal Coordinate Multibody Dynamics Formulation
Authors: Takahashi Yoshitaka , Shimizu Nobuyuki 
Published: November 2020

Abstract
There are three basic finite element formulations which are used in the dynamics analysis of flexible beams undergoing large rotation and deformation. These are the floating frame of reference approach, the finite segment method and the large rotation vector approach. Recently, the absolute nodal coordinate formulation was proposed by A.A.Shabana et al. In this formulation, elastic forces are lead by approximating the slope of the beam at an arbitrary point on the neutral axis of the beam in terms of the slope of the simple support axis of the beam.
In this paper, we propose the mean axis of the planar Bernoulli-Euler beam for the absolute nodal coordinate approach. The origin and the orientation of this axis are selected so as to minimize the total deformation of the concerned beam. And the selected axis can be simply described by the nodal coordinates of the beam element. Using the mean axis instead of the simple support axis, the elastic forces of the beam element may be more precisely calculated. Finally, we show numerical examples to demonstrate effectiveness of this approach.
Absorbed Power As an Indicator of Health Risk Associated With Whole-Body Vibration Exposure
Authors: Xie X. Y. , Bhat R. B. , Boileau P.-E. 
Published: November 2020

Abstract
The human body behaves like a vibrating physical system having mass, elastic and damping properties. In order to study the biodynamic behavior of the body, it is common practice to model the body as a lumped single or a multiple-degree-of-freedom (MDOF) system. Standards have been developed using the frequency-weighted root-mean-square (rms) acceleration input to the body as the primary measure of whole-body vibration exposure. In this paper, absorbed power during exposure to vertical whole-body vibration is considered as a potential indicator of the physical stress affecting comfort and health. A four-degree-of-freedom biodynamic model is chosen to represent the body and the absorbed power for the different body segments and the total body is computed. On the basis of the model and of the guidance provided in ISO 2631-1:1997 relating vibration exposure with health risk, computations are carried out to define a health guidance caution zone based on absorbed power.
Experimental Validation of a Dynamic Model for Flexible Link Mechanisms
Authors: Caracciolo R. , Gasparetto A. , Trevisani A. 
Published: November 2020

Abstract
This paper presents an experimental validation of a finite element approach for the dynamic analysis of flexible multi-body planar mechanisms. The mathematical model employed accounts for mechanism geometric and inertial non-linearities and considers coupling effects among rigid-body and elastic motion. A flexible five-bar linkage actuated by two electric motors is employed as a test case. Experimentally determined link absolute deformations are compared with the numerical results obtained simulating the system dynamic behavior through the mathematical model. The experimental and numerical results are in good agreement especially after the very first transient period.
Comparison Between Flexible Multibody Tracked Vehicle Simulation and Experimental Data
Authors: Nakanishi Toshikazu , Isogai Koji 
Published: November 2020

Abstract
In this investigation, a comparison between planar multibody tracked vehicle simulation and experimentally obtained acceleration data is presented. On the simulation, rigid and flexible bodies are used and its results are compared. The data of flexible body are obtained by experimental modal test. From the modal test five modes are selected and used for the simulation. A method to determine the contact stiffness is presented. The calculation results show that using flexible body simulation, it is possible to get relatively good agreement with experimental acceleration data. Even using flexible body, to improve the closeness of the calculated and experimental results, one has to carefully select the contact parameters.
Closed Form Solutions to the Equation of Motion Avoiding Mass Matrix Inversion and Eigenvectors Decomposition
Authors: Reaud Karine , Vallee Claude , Fortune Danielle 
Published: November 2020

Abstract
Solutions of the vibrations equations are generally obtained, in the linear case, by methods involving either matrix exponential computation or matrix eigendecomposition. However, these methods lead to a loss of symmetry because of the necessary inversion of the mass matrix. In doing so, one can introduce ill-conditioned matrices and, thus, compute eigenvectors with poor accuracy. In order to avoid these inconveniences, our method, which is an extension of Le Verrier-Souriau algorithm, provides solutions to the vibrations equations without inverting the mass matrix or computing eigenvectors. Moreover, we can solve damping systems even when the damping matrix has no specific properties such as the Basile property.
Identification of Multi-Body Dynamics by External Force/Torque Measurements
Authors: Grotjahn Martin , Heimann Bodo 
Published: November 2020

Abstract
Analytical simplification and regrouping rules are presented which lead to a formulation of the base force/torque equations of tree-structured multi-body system which is linear with respect to a dynamic parameter vector of minimal dimension. The rules depend only on the kinematic parameters. They can be easily implemented in standard computer algebra programs. Furthermore, a new approach is presented for identification of the system’s dynamics by external force/torque measurements. It does not require optimized trajectories for parameter excitation. The method is applied to the identification of a 6-d.o.f. standard industrial robot by base force/torque measurements. A comparison to results of a conventional identification approach shows the efficiency of the presented identification method.
Lund’s Contribution to Rotor Stability: The Indispensable and Fundamental Basis of Modern Compressor Design
Authors: Gunter Edgar J. 
Published: November 2020

Abstract
In the early design of compressors and turbines, it was of importance to locate the rotor critical speeds so as to insure that a turbo rotor would not be operating at a critical speed. As compressor and turbine design became more sophisticated, a more detailed analysis of the rotor damped critical speeds and rotor log decrements was necessary. With compressors and turbines operating at higher speeds, under high power levels, and at multiples of the first critical speed, the problem of stability or self-excited whirling is of paramount importance. The onset of self-excited motion may lead to large amplitudes of motion with possible destructions of the rotor or the inability of the compressor to operate at peak power levels. Encountering this phenomenon with a compressor on an off-shore oil platform can mean millions of dollars of lost production. Self-excited whirling can be caused by fluid-film bearings, seals, Alford-type cross-coupling forces, or internal shaft friction, to name a few of the excitation mechanisms.
The problem of computing the approximate values of the rotor log decrement under full speed and loading conditions requires the solution of a complex eigenvalue problem. The computation of the rotor complex roots is an order of magnitude more difficult than the problem of undamped critical speed calculations. J. W. Lund presented the first practical numerical procedure for computing turbo-rotor log decrements. The mathematical transfer matrix method pioneered by Lund has allowed industry to develop and stabilize a vast array of rotating machinery leading to the savings to industry of millions of dollars. Without the procedures of Lund, for example, it would not have been possible to resolve stability problems encountered with both the hydrogen and oxygen space shuttle pumps. This paper briefly presents some of the attributes of the Lund stability procedure and its unique characteristics.
Some Unusual Cases of Rotor Instability
Authors: Olsson Karl-Olof 
Published: November 2020

Abstract
In the paper presented here three peculiar cases of rotor instability are presented. The first is a tilting-pad bearing used as an intershaft bearing in a two-spool gas turbine. It was initially chosen for its good stability properties. However, in a deeper study it was found that those benefits are greatly reduced when both inner shaft and outer bearing are rotating. The second case comprises a turbine which showed a very strange performance with vibrations alternating between heavy and mild amplitudes. The periods were a couple of minutes long. After a more elaborate instrumentation was installed it was found that vibrations were synchronous and that the rotor experienced continuos changes of vibrations interrupted by sudden changes of amplitude. This revealed that non-linearity and thermal effects coupled to the rotor vibrations must be incorporated to understand the behavior. Many hypotheses were tested and the one coming closest to explaining the case was one incorporating thermal bending caused by heat conduction through an annulus partly filled with oil. The third case is a simple one of more pure curiosity, where a rotor was provided with a substantial amount of inner damping, and just according to the school book showed dynamic instability.
Jorgen W. Lund: Theories Versus Tests
Authors: Tonnesen Jorgen 
Published: November 2020

Abstract
The contribution of the late Professor Jorgen W. Lund in the field of rotor dynamics and fluid film bearings is presented in a condensed form with the emphasis on the experimental work and results that confirm and support many of Dr. Lund’s theories and analyses. Included are subjects of rotor balancing by the influence method, unbalance response of a flexible rotor, damped critical speeds of flexible rotors and fluid film bearing’s static, dynamic and thermal properties.
Rotordynamics Involving Axial Rubbing Against a Disk
Authors: Childs Dara W. , Siddiqui Nameer A. 
Published: November 2020

Abstract
Test results are presented involving axial rubbing of a test rotor with an overhung disk to investigate test results cited by Den Hartog [1]. Point rubbing was introduced via a rod on the inside (motor-drive side) and outside faces of the overhung disk for multiple operating conditions (running speeds below and above the critical speed) and multiple shaft configurations. For supercritical running speeds, no change in the response spectrum was observed. For subcritical running speeds, a slight increase of response at twice running speed was observed.
“Face” axial rubbing was introduced by forcing a contact between the outside face of the disk and a flat surface. Rubbing at running speeds below the critical speed produced: (i) a small backwards component at the running speed frequency, (ii) a large backward-whirl component at twice running speed, and (iii) a very large, twice-running-speed, forward-whirl component. Rubbing at running speeds well above the critical speed produced a subsynchronous forward component near the critical speed. The large twice-running-speed results due to rubbing at the outside face were comparable to Den Hartog’s. However, point rubbing on the inside face did not produce the subsynchronous backward-whirl response cited by Den Hartog.
Analysis of a nonslipping kinematic whirl condition (comparable to classical dry friction whipping) for the face of an overhung disk against a stationary surface predicts reverse asynchronous whirl; however, testing over a wide range of parameters failed to produce this response. None of the present test results produced the types of very high vibration levels and grave consequences that have been produced in test rigs for conventional, radial dry-friction whirl and whip.
Modal Estimation of Gyroscopic Effect in Rotordynamic Systems
Authors: Sawicki Jerzy T. 
Published: November 2020

Abstract
A new approach for uncoupling the equations of motion typical for rotordynamical systems is presented. The method does not neglect the speed dependent effects, like gyroscopic effects, and can be particularly valuable in the controller design of actively controlled rotors. In the presence of hysteretic type of damping, the resulting uncoupled gyroscopic systems come with an equivalent viscous damping, equivalent in a sense of the same natural frequency and decay rate. The approach is illustrated through the example of technical interest. The generated results demonstrate that the developed approach is correct and straightforward.
Modeling and Stability Analysis of Turboprop Engine Installations
Authors: Alkhatib Rabih , Golnaraghi Farid 
Published: November 2020

Abstract
In this paper a simple formulation of dynamic model of a turboprop installations has been presented incorporating aerodynamic forces. A four-bladed propeller-engine is simplified to have six rigid-body degrees of freedom. The engine is connected to the nacelle through resilient elements in order to reduce vibration transmission from the engine to the airplane structure. The aerodynamic forces acting on the propeller are modeled utilizing quasi-steady airfoil theory by considering their effect as reaction forces. Using the formulated dynamic model, an analysis of the stability of the engine-mount is conducted by deriving a second order eigenvalue problem. The system natural frequencies are found to be dependent on the rotational speed. At lower speeds, the aerodynamic forces have a stabilizing effect on the system. At higher rotational frequencies, the engine reaches a speed after which the system becomes unstable. The use of soft resilient mounts maximizes the vibration isolation but lowers instability threshold speed.