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Showing papers on "Rotary inertia published in 1991"


Journal ArticleDOI
TL;DR: In this article, an analytical study was conducted to determine the fundamental frequencies and critical buckling loads for laminated anisotropic circular cylindrical shell panels, including the effects of transverse shear deformation and rotary inertia, by using the Galerkin technique.

70 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present a method for the complete shaking force and moment balancing of 17 types of eight-bar linkages only with revolute pairs due to both linear and rotary inertia, but external loads.

45 citations


Proceedings ArticleDOI
09 Apr 1991
TL;DR: With the modified output, flexible beams can be easily controlled using quite simple control strategies such as PD control.
Abstract: A modified output consisting of the reflected tip position is analyzed. It is shown that, for an arbitrary beam, the transfer function from the base torque to the derivative of the modified output is passive when the hub inertia is very large compared to the beam inertia. In addition, it is shown that for a uniform beam, the same result also holds when the hub inertia is very small compared to the beam inertia. With the modified output, flexible beams can be easily controlled using quite simple control strategies such as PD control. >

37 citations


Journal ArticleDOI
TL;DR: In this paper, the problem of determining the optimal dimensions of the undercut so that the frequencies of modes 2 and 3 of transverse motion are harmonically related with that of the fundamental (mode 1) was addressed.
Abstract: Beams used in certain percussion instruments with definite pitch such as marimba, xylophone, and vibraphone are undercut in order to bring the frequencies of the first few overtones into a harmonic relationship with the fundamental frequency. This paper addresses the problem of determining the optimal dimensions of the undercut so that the frequencies of modes 2 and 3 of transverse motion are harmonically related with that of the fundamental (mode 1). The undercut is assumed to have a parabolic shape described by two variable parameters related to its depth and width. The rest of the beam on each side of the undercut is assumed to be uniform. Seven pairs of optimal undercut parameters are found that bring the frequencies of the first three transverse modes into the harmonic (integer) ratios 1:3:6, 1:4:8–9, and 1:5:10–13. Calculations performed with and without taking into account the effects of rotary inertia and shear stress are compared against measurements taken from a set of experimental beams. The comparison shows that including the effects of rotary inertia and shear stress results in a better prediction of the optimal parameters of the undercut.

33 citations


Journal ArticleDOI
TL;DR: In this paper, the free and forced vibrations of a uniform beam elastically restrained against rotation at one end and against translation at the other end, and carrying a lumped mass with rotary inertia and external loading at an arbitrary intermediate point, are analyzed.

30 citations


Journal ArticleDOI
TL;DR: In this paper, a three-nodal, C 0 Timoshenko beam finite element model is applied to analyze the natural whirl speeds of a rotating shaft with different end conditions.

27 citations


Journal ArticleDOI
TL;DR: In this article, the eigenfrequencies of flexural vibration of a homogeneous rotor model were investigated, including shear, rotary inertia and the gyroscopic effect.
Abstract: This paper deals with the eigenfrequencies of flexural vibration of a homogeneous rotor model which includes shear, rotary inertia and the gyroscopic effect A formula for the critical speeds of this rotor has also been found It appears that the effect of these factors is smaller when the critical speed increases and the ratio of slenderness of a rotor decreases

18 citations


Journal ArticleDOI
TL;DR: In this article, a rotating Rayleigh beam, defined by adding the effect of the rotary inertia and the gyroscopic effects to the Bernoulli-Eider beam, has been formulated and its dynamic stiffness matrix is presented.
Abstract: The dynamic stiffness method has been applied to the evaluation of the natural frequencies of rotating systems. To this purpose, a rotating “Rayleigh beam,” defined by adding the effect of the rotary inertia and the gyroscopic effects to the Bernoulli-Eider beam, has been formulated and its dynamic stiffness matrix is presented in this paper. The effects due to the presence of concentrated disks, as well as of elastic, isotropic supports, have been included in the formulation. The usual matrix assembly procedure is used in order to obtain the global dynamic stiffness matrix of the system. The natural frequencies of the system are determined by utilizing an iterative root searching technique. Numerical results, obtained for a rotor system taken from the literature on this subject, are presented. Presented at the 45th Annual Meeting in Denver, Colorado May 7–10, 1990

12 citations


Journal ArticleDOI
TL;DR: The digital simulation studies examine the interaction between the flexible and the rigid body motions of the robot arm, investigate the improvement in the accuracy of the model by considering the flexibility of all rather than some of the links, assess the significance of the rotary inertia and shear deformation, and illustrate the advantages of using advanced composites in the structural design of robotic manipulators.
Abstract: A dynamic model for a two degree-of-freedom planar robot arm is derived in this study. The links of the arm, connected to prismatic and revolute joints, are considered to be flexible. They are assumed to be fabricated from either aluminum or laminated composite materials. The model is derived based on the Timoshenko beam theory in order to account for the rotary inertia and shear deformation. These effects are significant in modeling flexible links connected to prismatic joints. The deflections of the links are approximated by using a shear-deformable beam finite element. Hamilton's principle is implemented to derive the equations describing the combined rigid and flexible motions of the arm. The resulting equations are coupled and highly nonlinear. In view of the large number of equations involved and their geometric nonlinearity (topological and quadratic), the solution of the equations of motion is obtained numerically by using a stiff integrator. The digital simulation studies examine the interaction between the flexible and the rigid body motions of the robot arm, investigate the improvement in the accuracy of the model by considering the flexibility of all rather than some of the links of the arm, assess the significance of the rotary inertia and shear deformation, and illustrate the advantages of using advanced composites in the structural design of robotic manipulators.

11 citations


Proceedings ArticleDOI
01 Jan 1991
TL;DR: In this paper, a numerical integration routine is derived from a set of unified single step integration algorithms using a weighted satisfaction of the equilibrium equation governing the large deflection random response of laminated composite plates.
Abstract: A numerical integration routine is derived from a set of unified single step integration algorithms using a weighted satisfaction of the equilibrium equation governing the large deflection random response of laminated composite plates. The equilibrium equation is derived using a constant matrix large deflection finite-element formulation. In-plane inertia terms are considered in the formulation, however, rotary inertia terms are assumed negligible. Probability density, spectral density and autocorrelation functions of the maximum displacement and strain responses are presented for three acoustic excitation levels. Classical thin plate boundary conditions and pseudo white noise excitation are used in this investigation.

10 citations


Patent
Hidese Wataru1
31 Jul 1991
TL;DR: In this article, the rotary head of a pick and place head was reduced in size to reduce the rotational inertia of the rotating inertial mass of the head and reduce the vibration at the time of indexing.
Abstract: An electrical component placing apparatus having a rotary head is required to be further accelerated to place an electrical component. In order to accelerate the operation of the placing apparatus, the indexing speed of the rotary head must be accelerated. However, since the rotary head is heavy, its rotating inertial is large. Thus, when the indexing speed of the rotary head is accelerated, a vibration at the time of stopping indexing of the rotary head is increased as well. Therefore, mistakes of picking up the electrical component by the pick and place head and placing the electrical component on the substrate occur. This invention reduces the outer diameter of a rotor for indexing a pick and place head smaller than the diameter of a guide for guiding the indexing of a pick and place head, disposes a bracket for supporting the pick and place head along the wall surface of the rotor and reduces the rotating diameter of the pick and place head smaller than the diameter of the guide. With the arrangement described above, the rotary head is reduced in size to largely reduce its weight and to reduce the rotary inertia of the rotary head. Therefore, the rotary inertia of the rotary head is reduced, and the vibration of the pick and place head at the time of indexing is reduced. Consequently, the rotary head can be indexed at a high speed, thereby placing the electrical component on the substrate at a high speed.

Journal ArticleDOI
TL;DR: In this paper, the effects of transverse shear and rotary inertia included in the deformation of a cylindrical shell are modeled as a rigid body which rides on a gun.

Patent
15 Aug 1991
TL;DR: In this article, a method for inertia welding axially symmetric articles while controlling the gripping force applied to the rotating component is described, which is particularly useful in welding high strength superalloy articles, where extremely high axial forces are required to produce an adequate weld joint.
Abstract: A method for inertia welding axially symmetric articles while controlling the gripping force applied to the rotating component is described. A spacer inserted into the rotating headstock creates an alternative path for the axial force in excess of that required for causing gripping of the rotating component, and thus minimizes distortion of the inertia welded article. This is particularly useful in welding high strength superalloy articles, where extremely high axial forces are required to produce an adequate weld joint.

Journal ArticleDOI
TL;DR: In this article, a simple and computationally efficient numerical approach is employed for free vibrations of complicated shaped layered shells of revolution, where each layer of the shell is assumed to be constructed from an orthotropic material.

Journal ArticleDOI
TL;DR: In this paper, the free vibrations of continuous beams with singularities in inertia and stiffness distribution are obtained using Galerkin's approach using simple closed-form mathematical expressions for the mode shapes of vibrations.
Abstract: The free vibrations of continuous beams with singularities in inertia and stiffness distribution are presented in this paper. Simple closed-form mathematical expressions for the mode shapes of vibrations are obtained using Galerkin's approach. Several numerical examples of structures with known exact solutions are presented to show the accuracy of the method. Also, examples of a simple beam with intermediate elastic translational and rotational supports carrying point and rotational mass, a two-span continuous beam with variable moment of inertia and mass distribution and a single-span beam with fixed end and overhanging cantilever are presented to show the applicability of the method

Journal ArticleDOI
TL;DR: In this article, a finite element formulation with use of a two-noded shear flexible element with four degrees of freedom (DOF) node is adopted to study the effects of shear deformation and rotary inertia on two-dimensional panel flutter.



Journal Article
TL;DR: In this article, the root-mean-square value of the velocity field and Tz is the measured average zero up-crossing period for the random fluid velocity were defined for irregular wave flows.
Abstract: where CTu is root-mean-square value of the velocity field and Tz is the measured average zero up-crossing period for the random fluid velocity. This definition of KCr is consistent with the definition presented by Moe (1990) for irregular wave flows. In addition, a statistical frequency parameter, [3\" similar to the [3 defined in sinusoidal experiments, is defined based on Tz and is related to KCr and Rer by:

Book ChapterDOI
01 Jan 1991
TL;DR: It is shown that a 10:1 reduction in fundamental frequency and substantial change in mode shape results from variations in payload through a practical range and Implications to plant and control design are discussed including sensor placement and accommodation of dynamic changes.
Abstract: The “Exact” and pole/zero transfer functions are developed for a flexible beam-like single structural link with actuator on one end and payload on the other. This model represents a broader class of actuator hub and payload mass properties than is found in prior literature. The dependence of dynamics on the hub and payload are studied and graphs are provided to facilitate estimation of poles and zeroes for any similar plant. It is shown that a 10:1 reduction in fundamental frequency and substantial change in mode shape results from variations in payload through a practical range. Payload rotary inertia is shown to cause a qualitative change in mode shape resulting in loss of observability/controllability in some cases. Implications to plant and control design are discussed including sensor placement and accommodation of dynamic changes. Analytical results are compared to those measured on an experimental beam and show very good agreement in modal frequency and shape.

Book ChapterDOI
01 Jan 1991
TL;DR: A quick and automatic algorithm for evaluation of modal characteristics for unsymmetric turbine blades is developed and employs a special beam element with fifteen degrees of freedom, and uses a large-deflection small-strain Euler-Bernoulli beam formulation.
Abstract: A quick and automatic algorithm for evaluation of modal characteristics for unsymmetric turbine blades is developed. Unlike conventional procedures, only a few geometric and material properties are needed in the present approach as input for a finite-element program by which the modal analysis is carried out. A cubic spline interpolation method is generated to prescribe the profile of airfoils so that related section properties are computed by means of numerical integrations. The finite element analysis, in this study, employs a special beam element with fifteen degrees of freedom, and uses a large-deflection small-strain Euler-Bernoulli beam formulation. Coriolis acceleration, centrifugal forces, warping effects, and rotary inertia are considered in the dynamic analysis. The effect on natural frequencies and modal shapes as changes to blade geometric and stiffness characteristics are analyzed. The method developed in this study can be utilized in the computer-aided design (CAD) for such blades.

Patent
28 Mar 1991
TL;DR: In this paper, the magnetic resistance element was used to increase the density of a track by detecting the rotational displacement between a multiplolar vertical magnetizing body and the actuator centering on the rotary shaft of the rotor actuator.
Abstract: PURPOSE:To increase the density of a track by providing a magnetic resistance element for detecting the rotational displacement between a multiplolar vertical magnetizing body the actuator centering on the rotary shaft of the rotary actuator. CONSTITUTION:A device is provided with the magnetic head 4 on the edge of a swing arm 5 and the multiploar magnetizing body 6' on the edge of the tail part 5a of the swing arm 5. The magnetization is performed not holizontal but vertical. In addition, the device is provided with the magnetic resistance element 8 on a position facing the multipolar magnetizing body 6' of an unit body 9 and a voice coil motor 10 for rotating the swing arm 5. An encoder is constituted of the multipolar magnetizing body 6' and the magnetic resistance element 8. Thus, the radius of the encoder can be enlarged without increasing a rotary inertia, the polar pitch of the magnetizing body 6' can be shortened, and the tracking density can be increased.

01 Jan 1991
TL;DR: In this article, a general procedure to derive a dynamic model for a revolute flexible robot arm, which takes into consideration the rotary inertia and shear deformation effects, is presented.
Abstract: High-precision assembly tasks are often performed by compact industrial robots with small work envelopes. The end-effector positional accuracy of compact robots can be accurately predicted by considering the links of the robot arm as short beams. In this study, a general procedure to derive a dynamic model for a revolute flexible robot arm, which takes into consideration the rotary inertia and shear deformation effects, is presented. Only the last link of the arm is considered to be flexible and assumed to be fabricated from laminated composite materials. Hamilton’s principle is used to derive the equations of motion. A displacement finite element model based on the Timoshenko beam theory is implemented to approximate the solution. The digital simulation studies predict the deflections at the end effector and examine the combined effects of rotary inertia and shear deformation. Furthermore, the improvement in the dynamic response of the robot arm resulting from the fabrication of the manipulator from laminated composite materials is demonstrated.


Proceedings ArticleDOI
31 Oct 1991
TL;DR: In this article, a method based upon the theory of small damped oscillations of a system about its equilibrium position is used to measure the moment of inertia of human lower leg.
Abstract: The present investigation involves the validation of a technique for the determination of the moment of inertia of human lower leg and of the damping coefficient of the knee joint. A method based upon the theory of small damped oscillations of a system about its equilibrium position is used to measure the moment of inertia of human lower leg. This method, in contrast with the others, is simple and does not require highly sophisticated instrumentation. The validation of this method is performed using a cylinder of known moment of inertia and the small oscillation apparatus (SOA). The results obtained were highly reproducible, however, the average difference between the known moment of inertia and that measured was less than 15%.