bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transient Dynamic Response of a Whip Antenna to a Simulated Nuclear Event
Authors: Corder Paul R. 
Published: March 2021

Abstract
The objective of this study was to perform analyses for the static and dynamic mechanical response of a 36 ft fiberglass whip antenna for the purpose of determining survivability under nuclear weapons effects. The static analysis was to obtain the stiffness/deflection characteristics of the antenna using material, wall-thickness, and mechanical loading history provided by the Naval Surface Warfare Center. The results of the static analysis were then to be used in a NASTRAN transient dynamic analysis. The effect of the thermal pulse associated with the blast was not directly considered in these studies.
An analytical model of the whip antenna deflected by transverse loading was developed using Castigliano’s Theorem. The resulting integrals were evaluated using Mathematica™. The diameters, wall thicknesses, and mass density resulting from the static response study were then used in the linear, transient dynamic analysis.
These studies concluded that the suggested modeling approach is suitable for the static and linear transient dynamic response analysis of a standard 36 foot fiberglass whip antenna to a 4 KT, 7 psi air blast (without thermal effects). The “Basic” model suggests a linear finite element model maximum deformation to be within 10% of the deflection of about 16 feet observed in the test video. Low-to-midrange stresses are expected at this deformation. A 1 MT, 7 psi air blast would probably, but not necessarily, fail the antenna. These studies support the conclusion that the dynamic response of a standard 36 ft whip antenna is “duration-dependent” within the range of overpressures considered.
On the Stability of Forced Radial Oscillations of an Experimental Spring Pendulum
Authors: Bayly Philip V. , Virgin Lawrence N. 
Published: March 2021

Abstract
The elastic pendulum is a 2-degree-of-freedom, nonlinear device in which the pendulum bob may slide up and down the pendulum arm subject to the restoring force of a linear spring. In this study, radial motion (motion along the arm) is excited directly. Responses to this excitation include purely radial oscillations as well as swinging motion due to a 2:1 internal resonance. Changes in the behavior of the nonlinear spring pendulum occur when, under the control of a parameter, radial oscillations become unstable and are replaced by radial plus swinging motion. This bifurcation is explored analytically, numerically and experimentally, using the basic ideas of Floquet theory. Poincaré sampling is used to reduce the problem of describing the stability of a limit cycle to the easier task of defining the stability of the fixed point of a Poincaré map.
Effect of Gravity on the Static and Dynamic Characteristics of a Single Link Component of Flexible Multibody Systems
Authors: Smart David W. , Wiens Gloria J. 
Published: March 2021

Abstract
As large space structures and the component links of robotic manipulators become increasingly more flexible, axial loadings are playing an increasingly more important role in the elastic characteristics of the systems. The research presented in this paper provides a relatively simple theoretical model based on the quasi-dynamics of a component link for flexible multibody systems. The theoretical model has shown that the axial component of gravity can play a major role in predicting accurate first and second natural frequencies and the static deflections of component links typical of flexible multibody systems. By definition, the axial loading contribution is a function of rigid body orientation, with the more significant influence occurring in the vertical positions. Furthermore, the degree of this effect is directional, depending on whether the axial loading is compressive or tensile. The results elude to a possible simple, approximation approach for modeling complex multilink systems subject to gravitational loading. In addition, the presented analysis approach has been experimentally validated where the theoretical results have been shown to agree very well with the experimental findings.
Vibration Suppression by Modulation of Elastic Modulus Using Shape Memory Alloy
Authors: Segalman Daniel J. , Parker Gordon G. , Inman Daniel J. 
Published: March 2021

Abstract
A method is proposed for suppressing the resonances that occur as an item of rotating machinery is spun-up from rest to its operating speed. This proposed method invokes “stiffness scheduling” so that the resonant frequency of the system is shifted during spin-up so as to be distant from the excitation frequency. A strategy for modulating the stiffness through the use of shape memory alloy is also presented.
Piezothermoelasticity and Control of Piezoelectric Laminates Exposed to a Steady-State Temperature Field
Authors: Tzou H. S. , Ye R. 
Published: March 2021

Abstract
Piezothermoelastic effects of distributed piezoelectric sensors and actuators are investigated. Vibration control of piezoelectric laminates subjected to a steady-state temperature field is studied. A new 3-D piezothermoelastic finite element with three internal degrees of freedom is formulated using a variational formulation. A system equation for the piezoelectric continuum exposed to combined elastic, electric, and thermal fields is formulated. Distributed sensing and control equations are derived. All these effects are studied in a case study.
Modelling Fluid Inertia Forces of Short Journal Bearings for Rotordynamic Applications
Authors: El-Shafei A. 
Published: March 2021

Abstract
It has been recently suggested that fluid inertia may play an important role in the dynamic behavior of rotors supported on journal bearings. This paper presents a model for fluid inertia forces in short cylindrical journal bearings based on an energy approximation. The inertialess velocity profiles predicted by the solution of Reynolds’ equation are inserted in the axial momentum equation multiplied by the axial velocity profile and integrated across the film thickness, to obtain the pressure in short journal bearings including the fluid inertia effect. The pressure is then integrated to obtain the fluid inertia forces. It is shown that the inertia forces thus obtained are proportional to the usual radial, centripetal, tangential and coriolis accelerations of the journal, in addition to a nonlinear radial acceleration. Moreover, it is shown that the inertia forces contribute to the stiffness and damping characteristics of the journal bearings. The inertia coefficients of the bearings are obtained in cartezian and cylindrical coordinates, for both uncavitated and cavitated bearings, and are plotted versus the eccentricity ratio. The model thus obtained is an analytical closed form model for fluid inertia forces in short journal bearings. Such a model is the most suitable for rotordynamic applications, particularly for time transient rotordynamic simulations.
An Experimental Investigation of the Dynamic Characteristics of an Axial Spline Coupling in High-Speed Rotating Machinery
Authors: Walton James F. , Ku C.-P. Roger , Lund Jorgen W. 
Published: March 2021

Abstract
This paper presents the results of the second part of an investigation of the dynamic characteristics of an axial spline coupling in high-speed rotating machinery. In the experimental method described herein, the bending moments and angular deflections transmitted across the axial spline coupling were measured while the nonrotating shaft was excited by an external shaker. The effects of external force and frequency on the angular stiffness and damping coefficients were investigated. The angular stiffness and damping coefficients were used to perform a linear steady-state rotordynamics stability analysis, and the unstable natural frequency was calculated and compared to experimental measurements. In addition, the mechanism and source of internal rotor friction instability caused by the axial spline couplings was studied.
Active Control of Machine Tool Chatter for a Boring Bar: Experimental Results
Authors: Tewani Sanjiv G. , Switzer Thad C. , Walcott Bruce L. , Rouch Keith E. , Massa Ted R. 
Published: March 2021

Abstract
A typical boring bar is a metal cutting tool with large overhang ratio, due to which it is characterized by low dynamic stiffness. Therefore, during cutting process, it is susceptible to cutting instability, known as machine tool chatter. In this paper, the use of an active dynamic absorber to actively control machine tool chatter in a boring bar is studied.
An active dynamic absorber is designed such that it can be easily assembled with a commercially available steel boring bar. A piezoelectric pusher is used as the actuator for the active dynamic absorber. The dynamic equations of the boring bar with active dynamic absorber are calculated from experimentally obtained frequency response functions of the system. Optimal control theory is applied to the dynamic equations to calculate state variable feedback parameters. The state variable feedback is implemented using a Digital Signal Processing (DSP) chip. Cutting tests were performed with this setup for different cutting conditions, and for different overhangs of the boring bar. Stable cutting operations were performed using the boring bar with active dynamic absorber, for length to diameter (L/D) ratio upto 9.
Pneumatic Vibration Isolation of a Table Traversed by a Moving Load
Authors: Vu Hung V. , Torby Bruce J. 
Published: March 2021

Abstract
The modeling and analysis of a vibration isolated table system is investigated as a preliminary study for the design of an active feedback control system. The system consists of a table, a moving load traversing on the top surface of the table, and four identical pneumatic isolators supporting the table at four corners. For each isolator, there is a spool valve and a needle valve. A mathematical model of the system is developed, which includes the governing differential equations of the rigid table and pneumatic isolators, the nonlinear saturating characteristics of the spool valve, and the flow restriction of the needle valve. The isolation table is commercially available. Using MATRIXX/SystemBuild, the time response of the table is simulated for a few representative cases. The results indicate that the table will descend and not return to the original position, for any speed of the moving load, until the load stops. The higher the speed of the load, the quicker and farther down the table will descend. The larger the opening of the needle valve is, the table oscillates more because of less damping. The table response is relatively well damped even when the needle valve is fully open. The speed of the response, which is measured by the settling time, is fastest when the needle valve is open at about 25%.
Multi-Mass Absorbers Effective in Wide Frequency Band
Authors: Einstein George , Wernerowski Krzysztof 
Published: March 2021

Abstract
One of the most efficient method of vibration control is the method of dynamic damping. Most existing theory enables a design of a dynamics damper for a one degree-of-freedom system. Here the theory is extended to allow for a design of dynamic mass dampers with viscous friction suitable for a systems with multiple degrees-of-freedom. Effective method of multi-mass absorbers in a wide angular frequency band was designed and developed.
Finally, by inspection of the frequencies for the amplitudes of vibrations of the essential masses within the vibratory system are reduced or decreased to zero. One may optimize the various designs of dynamic systems containing mass-damping elements. Detailed numerical analysis and specific calculations are performed in this publication.
Forced Vibration of Thick Viscoelastic Cylinders
Authors: Hamidzadeh H. R. , Minor G. R. 
Published: March 2021

Abstract
Harmonic forced vibration of thick viscoelastic hollow cylinders of infinite extent is considered. The cylinder is excited by stresses applied at the inner and outer boundaries. The governing equation of motion is developed by utilizing three dimensional theory of elastodynamics. The material damping is allowed using complex elastic moduli for the viscoelastic medium. Modal displacements and stresses at any point in the medium are formulated in terms of boundary stresses. Frequency responses for radial, tangential and axial displacements are computed for different circumferential and axial wave numbers. The effect of different material loss factors on the frequency responses is examined for axial and nonaxisymmetric modes. The dimensionless resonant frequencies for zero loss factor are compared with dimensionless natural frequencies available for elastic material. Comparison indicates excellent agreement between the results.
Static and Dynamic Characteristics of Spot Welded Sheet Metal Beams
Authors: Pal Kaushik , Cronin Donald L. 
Published: March 2021

Abstract
Although widely used as structural components in the auto industry, spot welded sheet metal beams manifest static and dynamic behavior that is not well characterized.
For the present study, sample beams of three representative cross-sections — hat, box and box with partition — were fabricated of sheet steel. The spacing between the spot welds that hold these sections together was varied from 25.4 mm (1 inch) to 203.2 mm (8 inch) using a 25.4 mm (1 inch) increment. The beams were subjected to static bending and static torsion tests, and bending and torsional stiffnesses were determined as functions of spot weld spacing. The beams were then vibrated, and significant lower natural frequencies were determined as functions of spot weld spacing. Mode shapes were also observed for these frequencies.
Pains were taken throughout the testing to ensure that the results obtained were of good statistical quality. Work was also done to distinguish the effect on results of beam length and end conditions from that of spot weld spacing.
As part of the study, finite element models of the beams were constructed. The results of finite element analysis (FEA) and experiment are compared and insights are offered concerning the appropriate modeling of such structures.
Dynamic Behavior of Vehicles Travelling on Bridges
Authors: Esmailzadeh Ebrahim , Ghorashi Mehrdaad 
Published: March 2021

Abstract
An investigation into the dynamic behavior of a bridge with simply supported boundary conditions, carrying a moving vehicle, is performed. The vehicle has been modelled as a two degree of freedom lumped-parameter system travelling at a uniform speed. Furthermore, the bridge is assumed to obey the Euler-Bernoulli beam theory of vibration. This analysis may well be applied to a beam with different boundary conditions, but the computer simulation results given in this paper are set for only the case of freely hinged ends. Numerical solutions for the derived differential equations of motion are obtained and their close agreement, in some extreme cases, with those reported earlier by the authors are observed. Finally, the effect of speed on the maximum dynamic deflection of bridge is shown to be of much importance and hence an estimation for the critical speed of the vehicle is presented.
A Dynamic System Model for Estimating Surface-Induced Frame Loads During Off-Road Cycling
Authors: Wilczynski Herve , Hull Maury L. 
Published: March 2021

Abstract
To facilitate the rational design analysis of off-road bicycle frames, this paper reports a dynamic model of the bicycle/rider system which estimates frame loads for bicycles traveling over rough surfaces. To develop this model, the frame loads at rider contact points were first measured experimentally as a rider coasted over a test track with randomly spaced surface irregularities in both seated and standing positions. Following this measurement, a dynamic system model was developed with the aid of the commercial software package, Dynamic Analysis and Design Software (DADS). The development process consisted of two stages. The first stage involved developing component models (e.g., seat) which could reproduce the essentials of the measured data. The second stage involved identification of parameter values for those parameters shown to most profoundly affect simulated load results. These parameters were all associated with the dynamics of the body thus emphasizing the importance of reflecting the dynamic system nature of the body in the model. Following parameter identification, simulated loads were statistically tested and were not significantly different from experimental loads. Also, maximum magnitude dynamic loads were compared to corresponding static load magnitudes and were larger for eight of the ten load components measured. With the importance of dynamic loads demonstrated and the model verified, it can now be used advantageously to generate a loading database for design analysis purposes.
On First-Order Decoupling of Equations of Motion for Constrained Dynamical Systems
Authors: Loduha Timothy A. , Ravani Bahram 
Published: March 2021

Abstract
In this paper we present a method for obtaining first-order decoupled equations of motion for multi-rigid body systems. The inherent flexibility in choosing generalized velocity components as a function of generalized coordinates is used to influence the structure of the resulting dynamical equations. Initially, we describe how a congruency transformation can be formed that represents the transformation between generalized velocity components and generalized coordinate derivatives. It is shown that the proper choice for the congruency transformation will insure generation of first-order decoupled equations of motion for holonomic systems. In the case of nonholonomic systems, or more complex dynamical systems, where the appropriate congruency transformation may be difficult to obtain, we present a constraint relaxation method based on the use of orthogonal complements. The results are illustrated using several examples. Finally, we discuss numerical implementation of congruency transformations to achieve first-order decoupled equations for simulation purposes.
A Novel Design Procedure for Reducing Vibration and Noise in Gears
Authors: Yoon K. Y. , Rao S. S. 
Published: March 2021

Abstract
A new method is proposed for reducing vibration and noise of involute gears. The method is based on the use of cubic spline curves for gear tooth profile modification. The tooth profile is constrained to assume an involute shape during the loaded operation. Thus the new gear profile assures conjugate motion at all points along the line of action. The new profile is found to result in a more uniform static transmission error compared to standard involute profile thereby contributing to the improvement of vibration and noise characteristics of the gear.
Deriving Exploded Views by Graph Transformation for Assembly Planning
Authors: Mohammad Riaz , Kroll Ehud 
Published: March 2021

Abstract
An automatic assembly planner that is integrated with a CAD system is being developed. To facilitate computer understanding of the design, a high-level representation scheme based on features and mating conditions is used and briefly explained. The focus of this paper is on automatic reasoning about relative spatial locations of product components for the purpose of establishing assembly precedence. The key element in the initial product description is a graph of planar contacts (’against’ mating conditions) between parts. This graph is transformed by a rule-based procedure into a new graph representing an exploded-view of the product. In the process of transforming the graph, the program uses rules that encode assembly process knowledge and heuristics, and performs interference checks on feature-based descriptions rather than solid models. The exploded view and the mating conditions are used to generate selected assembly sequences of the product.
Assembly Representation Within a Product Data Framework
Authors: Henson Brian W. , Baxter James E. , Juster Neal P. 
Published: March 2021

Abstract
Recent research at the University of Leeds demonstrated how a product data model can integrate the information required and used during product design and manufacture. The product data framework developed during this research structured assemblies as lists of parts and did not consider information about the relationships between components necessary to support applications such as tolerance analysis and design for assembly. This paper describes how we intend to combine research in assembly representation, functional modeling and data modeling to describe the geometric and functional relationships between components of assemblies. Focus is provided by considering both the design process and the information requirements of a design for assembly analysis.
Compliance and Dynamic Analysis of Tendon-Driven Robotic Mechanisms
Authors: Chang Sun Lai 
Published: March 2021

Abstract
The stiffness and compliance matrices of tendon-driven robotic mechanisms have been derived in this paper. Position compensation for external force/moment based on the system compliance has also been developed. Using a stretchable tendon model, dynamic equations are systematically generated. Natural frequencies and mode shapes of this class of mechanisms have been analyzed through local linearization of its dynamic equations.
Kinematic Error, Compliance, and Friction in a Harmonic Drive Gear Transmission
Authors: Tuttle Timothy D. , Seering Warren P. 
Published: March 2021

Abstract
In this experimental examination, the behavior of harmonic-drive kinematic error, compliance, and friction was characterized. In particular, kinematic error was confirmed to appear primarily at frequencies that were multiples of the wave-generator rotational velocity, and static stiffness measurements were found to yield a range of profiles that could be highly nonlinear. Additional measurements of static and dynamic friction demonstrated that energy dissipation in harmonic drives varies nonlinearly with velocity and can escalate during system resonance. Due to the inseparable interaction between harmonic-drive kinematic error, compliance and friction, transmission properties often showed significant variation with operating conditions and were difficult to characterize accurately.
Dynamics of the Generalized Slider-Crank Mechanism
Authors: Fischer Ian S. , Rahman Sahidur 
Published: March 2021

Abstract
Dual-number techniques are used to analyze the dynamics of the slider crank mechanism generalized to consider the effects of the cylinder axis being offset and non-perpendicular to the crankshaft axis, conditions which result in reciprocating machinery such as engines and compressors from manufacturing tolerances. Results for various cases are shown and the implications for the design engineer are discussed.
An Efficient Genetic Algorithm for Large Scale Built-Up Structural Optimization
Authors: Wang Shigang , Cheng Xindu , Zhou Ji , Yu Jun 
Published: March 2021

Abstract
In this paper, a new zigzag method for plate structures and a genetic algorithm (GA) of dynamic source seed spaces are developed and a combination of them is used to deal with large scale built-up structural optimization. The new GA combined with the zigzag method can work efficiently to cope with large scale structural optimization with displacement and stress constraints. Examples show that this GA is robust and can be used for many complex structural optimization problems.