scholarly journals Influence of rotatory inertia on stochastic stability of a viscoelastic rotating shaft

2008 ◽  
Vol 35 (4) ◽  
pp. 363-379
Author(s):  
Ratko Pavlovic ◽  
P. Kozic ◽  
G. Janevski
Keyword(s):  
Cross Section ◽  
Stochastic Stability ◽  
Circular Cross Section ◽  
Longitudinal Axis ◽  
Physical Parameters ◽  
Rotatory Inertia ◽  
Rotating Shaft ◽  
Axial Forces ◽  
Constant Rate ◽  
Mean And Variance

The stochastic stability problem of a viscoelastic Voigt-Kelvin balanced rotating shaft subjected to action of axial forces at the ends is studied. The shaft is of circular cross-section, it rotates at a constant rate about its longitudinal axis of symmetry. The effect of rotatory inertia of the shaft cross-section and external viscous damping are included into account. The force consists of a constant part and a time-dependent stochastic function. Closed form analytical solutions are obtained for simply supported boundary conditions. By using the direct Liapunov method almost sure asymptotic stability conditions are obtained as the function of stochastic process variance, external damping coefficient, retardation time, angular velocity, and geometric and physical parameters of the shaft. Numerical calculations are performed for the Gaussian process with a zero mean and variance ?2 as well as for harmonic process with amplitude H.

Vibration Localization in Rotating Shafts: Part II — Experiment

1995 ◽  
Author(s):  
A. Galip Ulsoy ◽  
Christophe Pierre ◽  
Suhyun Choi
Keyword(s):  
Cross Section ◽  
Circular Cross Section ◽  
Companion Paper ◽  
Rotating Shaft ◽  
Vibration Localization ◽  
State Response ◽  
Mass Unbalance ◽  
Rotating Shafts ◽  
Principal Directions ◽  
Gyroscopic Coupling

Abstract This paper presents an experimental study of vibration localization in single-span, flexible, rotating shafts. It was shown in a companion paper (Part I) that a non-circular cross-section of the rotating shaft, leading to dissimilar lateral moments of inertia, can introduce disorder. Internal coupling between the principal directions of vibration is provided by the rotational speed through the gyroscopic moments. It is experimentally demonstrated here that directional vibration localization can occur for certain appropriate combinations of disorder and coupling. The steady state response, due to mass unbalance, of a simply supported rotating shaft is considered. It is shown that disorder and gyroscopic coupling lead to directional vibration localization; i.e., larger vibration amplitudes in one of the two orthogonal principal directions of the shaft cross section.

Analysis of Axially Loaded Annular Shells With Applications to Welded Bellows

1960 ◽  
Vol 82 (3) ◽  
pp. 741-753 ◽  
Author(s):  
M. Hetenyi ◽  
R. J. Timms
Keyword(s):  
Experimental Data ◽  
General Solution ◽  
Cross Section ◽  
Circular Cross Section ◽  
Radius Of Curvature ◽  
Approximate Design ◽  
Axial Forces ◽  
The Mean ◽  
Maximum Stresses ◽  
Toroidal Shells

A method is presented for the calculation of stresses and deflections in ring-shaped shells of circular cross section, subjected to axial forces. The solution is derived without the restriction imposed for toroidal shells by previous investigators, that the radius of curvature of the cross section is to be small in comparison with the mean radius of the torus. The range of applicability of the method is extended hereby to include the slightly arched convolutions used in the construction of welded bellows. By a rational reduction of the general solution approximate design formulas are obtained for the maximum stresses and deflections in bellows under axial forces and the calculated values are compared with experimental data.

Finite Extension of an Elastic Strand With a Central Core

1978 ◽  
Vol 45 (4) ◽  
pp. 852-858 ◽  
Author(s):  
N. C. Huang
Keyword(s):  
Cross Section ◽  
Circular Cross Section ◽  
Single Layer ◽  
Finite Extension ◽  
Contact Forces ◽  
Central Core ◽  
The Core ◽  
Axial Forces ◽  
Helical Angle ◽  
Curved Rods

This paper deals with the finite extension of an elastic strand with a central core surrounded by a single layer of helical wires subjected to axial forces and twisting moments. The central core is considered as a straight rod of circular cross section and the helical wires are regarded as slender curved rods with circular cross section. The theory of slender curved rods is used in the analysis. Geometrical nonlinearities due to the reductions in helical angle and cross section of the core and wires are included. It is found that as a result of the contact between the central core and helical wires, a separation between helical wires can occur during the extension of the strand. Stresses in the core and wires as well as the contact forces between the core and wires are analyzed for strands with various helical angles subjected to different axial forces. Examples are presented for the finite extension of strands with fixed ends and strands with free ends.

Aerodynamics Analysis on Unsymmetrical Fuselage Models

2013 ◽  
Vol 315 ◽  
pp. 273-277
Author(s):  
Mohd Ridh bin Abu Bakar ◽  
Bambang Basuno ◽  
Sulaiman Hasan
Keyword(s):  
Cross Section ◽  
Strong Influence ◽  
Lift Coefficient ◽  
Circular Cross Section ◽  
Longitudinal Axis ◽  
Pitching Moment ◽  
Moment Coefficient ◽  
Symmetrical Body ◽  
Semi Empirical ◽  
Plat Form

The large commercial passengers airplanes are mostly designed to have symmetrical body with respect to the longitudinal axis. However for small passengers airplanes or for the airplane designed as UAV plat form is normally having an unsymmetrical fuselage. The aerodynamics characteristics fuselage may give a strong influence to the overall aerodynamics characteristics of the airplane. The present work investigates the aerodynamics characteristics of the unsymmetrical fuselage with respect to the longitudinal axis. The fuselage assumed to have circular cross section and the coordinate of the fuselage are created by using the same equation which had been used in defining the coordinate of cambered airfoil NACA series four digits. The fuselage had been set to have the same maximum thickness 15 % of the fuselage length and different fuselage models are obtained through varying the position as well as the value of the maximum camber line. The semi empirical aerodynamic method for estimating the fuselage lift coefficient CL, drag coefficient CDand the fuselage pitching moment coefficient CMsuch as given by DATCOM are well established. However when it came to the unsymmetrical fuselage, this approach can not be adopted easily. The required of angle attack at zero lift of the corresponding unsymmetrical fuselage is difficult to define. The result for particular cambered fuselage indicates that the aerodynamics characteristics strongly influenced by how the fuselages camber lines look likes.

Vibration Localization in Rotating Shafts: Part I — Theory

1995 ◽  
Author(s):  
A. Galip Ulsoy ◽  
Christophe Pierre ◽  
Suhyun Choi
Keyword(s):  
Cross Section ◽  
Rotational Speed ◽  
Theoretical Study ◽  
Circular Cross Section ◽  
Rotating Shaft ◽  
Vibration Localization ◽  
Rotating Shafts ◽  
Principal Directions ◽  
Internal Coupling ◽  
Perturbation Solutions

Abstract This paper presents a theoretical study of vibration localization in single-span, flexible, rotating shafts. A non-circular cross-section of the rotating shaft, leading to dissimilar lateral moments of inertia, can introduce disorder. Internal coupling between the principal directions of vibration is provided by the rotational speed through the gyroscopic moments. It is shown, using both exact and perturbation solutions, that directional vibration localization can occur for certain appropriate combinations of disorder and coupling.

scholarly journals Modeling and Dynamical Behavior of Rotating Composite Shafts with SMA Wires

2014 ◽  
Vol 2014 ◽  
pp. 1-16 ◽  
Author(s):  
Yongsheng Ren ◽  
Qiyi Dai ◽  
Ruijun An ◽  
Youfeng Zhu
Keyword(s):  
Differential Equations ◽  
Natural Frequencies ◽  
Equations Of Motion ◽  
Dynamical Behavior ◽  
Circular Cross Section ◽  
Longitudinal Axis ◽  
Initial Strain ◽  
Marginal Effect ◽  
Rotating Shaft ◽  
Speed Increase

A dynamical model is developed for the rotating composite shaft with shape-memory alloy (SMA) wires embedded in. The rotating shaft is represented as a thin-walled composite of circular cross-section with SMA wires embedded parallel to shaft’s longitudinal axis. A thermomechanical constitutive equation of SMA proposed by Brinson is employed and the recovery stress of the constrained SMA wires is derived. The equations of motion are derived based on the variational-asymptotical method (VAM) and Hamilton’s principle. The partial differential equations of motion are reduced to the ordinary differential equations of motion by using the Galerkin method. The model incorporates the transverse shear, rotary inertia, and anisotropy of composite material. Numerical results of natural frequencies and critical speeds are obtained. It is shown that the natural frequencies of the nonrotating shaft and the critical rotating speed increase as SMA wire fraction and initial strain increase and the increase in natural frequencies becomes more significant as SMA wire fraction increases. The initial strain of SMA wires appears to have marginal effect on dynamical behaviors of the shaft. The actuation performance of SMA wires is found to be closely related to the ply-angle.

SAF file: It's really three dimensional file

2018 ◽  
Vol 14 (1) ◽  
pp. 1
Author(s):  
Prof. Dr. Jamal Aziz Mehdi
Keyword(s):  
Cross Section ◽  
Root Canal ◽  
Three Dimensional ◽  
Circular Cross Section ◽  
Circular Motion ◽  
Root Canal Treatment ◽  
Metal Core ◽  
Rotating Blade

The biological objectives of root canal treatment have not changed over the recentdecades, but the methods to attain these goals have been greatly modified. Theintroduction of NiTi rotary files represents a major leap in the development ofendodontic instruments, with a wide variety of sophisticated instruments presentlyavailable (1, 2).Whatever their modification or improvement, all of these instruments have onething in common: they consist of a metal core with some type of rotating blade thatmachines the canal with a circular motion using flutes to carry the dentin chips anddebris coronally. Consequently, all rotary NiTi files will machine the root canal to acylindrical bore with a circular cross-section if the clinician applies them in a strictboring manner

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