Moment Of Inertia Ratio Research Articles

Effect assessment for the interaction between shaking table and eccentric load

Electro-hydraulic shaking table is an essential experimental apparatus to evaluate structural performance under actual vibration condition. The control-structure interaction (CSI) between shaking table and eccentric load has lately received considerable attention for causing the accuracy degradation of shaking table test. At present, the research gap of the influence of the eccentricity of load on the CSI makes it challenging to find the CSI effects. And an effect assessment is yet to be proposed to evaluate the CSI effects, which has impeded the development of test technology. To overcome those theoretical bottlenecks, in this research, an analytical transfer function matrix of shaking table and eccentric load is established to analyze the CSI effects. The analysis is conducted under such conditions as different mass ratio (MR), moment of inertia ratio (IR), and eccentric distance ratio (ER) conditions. Through the analysis, the role of the ER is identified, the sensitivities of the MR, IR, and ER to the transfer function matrix are revealed, and the CSI effects are found. Furthermore, a novelty effect assessment is proposed to appraise whether the CSI effects can be ignored in shaking table test. And the visualization expression of the effect assessment is obtained for convenient application.

Three-dimensional CT for the diagnosis and management of bipartite scaphoids: a report of four cases in three patients

We investigated the role of three-dimensional (3-D) CT in the diagnosis and management of four bipartite scaphoids in three patients. We computed the volume ratio, moment of inertia ratio and direction vector from the centroid of the scaphoid to the os centrale carpi. We found that the os centrale carpi was always smaller than the scaphoid and showed an elongated shape in the scaphoid longitudinal axis. Its position was always posterior compared with the scaphoid anteroposterior axis. The main morphological feature of bipartite scaphoids was the continuity of the scaphoid from its proximal to distal aspect along the longitudinal axis. These criteria from 3-D imaging should be considered useful in the diagnosis of bipartite scaphoid as it allows differentiation from nonunion. 3-D single-photon emission computed tomography (SPECT)/CT was helpful in the surgical decision-making when the patient was symptomatic. 3-D imaging was also used for the preoperative simulation and planning of bone fusion as it simplifies surgery and makes it more accurate. Here we provide clear criteria for diagnosing bipartite scaphoids and for the planning when surgery is deemed necessary.

Rotating characteristics and stability analysis of unsymmetrical magnetically suspended motor

The rotating characteristic and the stability analysis of unsymmetrical magnetically suspended motor (MSM) are investigated in the article. Firstly, the dynamic functions of unsymmetrical MSM with different moment of inertia ratios and suspension span ratios are developed. Based on the equation of radial rotation, the open-loop pole and the frequency response are analyzed, so relationships among critical whirling frequency, moment of inertia ratio and suspension span ratio are established. Moreover, relationships among rotating characteristic, moment of inertia ratio and suspension span ratio are investigated, and then the rotation stability criterion of unsymmetrical MSM based on dual-frequency bode diagram is developed. Finally, the results prove that the proposed rotation analysis method is a potential way to analyze rotating characteristic of unsymmetrical MSM.

Modification of the Euler Load for the Stiffened Compressive Members and Determination of the Optimal Stiffening for the Maximum Buckling Load

The potential of buckling in compressive members has been considered as a disadvantage when using steel members in the construction industry. In spite of the progress made in this regard, buckling is still considered as a challenge in the analysis and design of compressive steel structural members. Such a challenging phenomenon can be controlled by strengthening of compressive members. Stiffened compressive members can control the weakness of steel members in the global buckling. In this paper, elastic buckling behavior of three-segment symmetric steel members with pinned ends is investigated. The differential stability equation for non-prismatic three-segment members is solved numerically. Critical load parameter for stiffened members is calculated considering different stiffened length and moment of inertia ratios. Based on a wide range of the calculated data, the buckling load could be accounted as a safe measure to be used in the design formulas. Evaluation of the effects of various parameters on the buckling load shows that the desired buckling load value can be achieved by a partially stiffened member. By constant increase of a member’s weight, the shorter the length of the variation in the cross-section, the higher moment of inertia is essential in the stiffened segment; and the maximum critical load parameter is achieved by a stiffened length ratio between 0.4 and 0.6.

The Eu:CROPIS Mass Property Campaign: Trimming a Spin-Stabilized Compact Satellite for a Long-Term Artificial Gravity Experiment

Eu:CROPIS (Euglena Combined Regenerative Organic Food Production in Space) is the first mission of DLR’s compact satellite program. The launch of Eu:CROPIS took place on December 3rd in 2018 on-board the Falcon 9 SSO-A mission. The satellite’s primary payload Eu:CROPIS features a biological experiment in the context of closed loop coupled life support systems. The Eu:CROPIS satellite mission uses spin stabilization along its Z -axis to provide defined acceleration levels for the primary and secondary payloads to simulate either a Moon or Mars gravity environment. For the payload performance, it is vital to achieve a minimum deviation between spacecraft Z -axis and the major moment of inertia (MoI) axis to minimize the offset of the envisaged acceleration levels. Specific moment of inertia ratios between the spin- and minor axes had to be maintained to allow the attitude control system to keep the satellite at a stable rotation despite environmental disturbances. This paper presents the adaptive and flexible trimming strategy applied during the flight model production, as well as the mass property measurement acceptance campaign and the respective results.

Comparison of Feed Drives with a Process Oriented Design Methodology

The paper points out a novel design methodology for electromechanical linear axis. It is based on common process parameters and an automated iterative solution algorithm. For the first time ever, different types of electromechanical linear axes can be compared. Furthermore, an optimum solution aiming a low moment of inertia ratio is the result of the design process. Using the example of a machining center, simulation and experimental results are shown. The performance of the process-oriented design methodology relating to additional design objectives is shown in this context.

Wake Topology of a Cylinder Undergoing Vortex-Induced Vibrations With Elliptic Trajectories

Wake vortex shedding topology of a cylinder undergoing vortex-induced vibrations (VIV) is investigated experimentally. Vibration measurements and flow visualization are utilized to study the connection between the cylinder response and the wake topology. The experiments were performed for two different orientations of the elliptic trajectories relative to the incoming flow at a fixed Reynolds number, moment of inertia ratio, mass ratio, and reduced velocity. Similar to the classical 2P regime, two counter-rotating vortex pairs are produced per oscillating cycle for both cases of elliptic trajectories examined here. However, significant changes in wake vortex dynamics are observed along the cylinder span. These changes include merging of vortices, which leads to shedding patterns similar to 2S and P + S modes downstream of the vortex formation region. The observed changes in vortex dynamics are accompanied by splitting of spanwise vortex filament and are attributed primarily to the changes in the local amplitude of vibrations along the span of the pivoted cylinder. It is shown that, being dependent on both the local amplitude of vibrations and vortex dynamics, the observed wake topology cannot be captured by the classical map of shedding regimes developed for VIV of one degree-of-freedom (DOF) cylinders.

Analysis of Mode II Crack in Bilayered Composite Beam

Analysis of Mode II Crack in Bilayered Composite Beam Mode II crack problem in cantilever bilayered composite beams is considered. Two configurations are analyzed. In the first configuration the crack arms have equal heights while in the second one the arms have different heights. The modulus of elasticity and the shear modulus of the beam un-cracked part in the former case and the moment of inertia in the latter are derived as functions of the two layers characteristics. The expressions for the strain energy release rate, G are obtained on the basis of the simple beam theory according to the hypotheses of linear elastic fracture mechanics. The validity of these expressions is established by comparison with a known solution. Parametrical investigations for the influence of the moduli of elasticity ratio as well as the moments of inertia ratio on the strain energy release rate are also performed. The present article is a part of comprehensive investigation in Fracture mechanics of composite beams.

LOCAL STABILITY OF WEB OF TAPERED BEAM SUBJECTED TO PURE BENDING

This paper deals with a theoretical and a numerical analysis of local stability of web of tapered beams subjected to a pure bending moment. A standard FEM code COSMOS/M has been used for a numerical estimation of a critical load multiplier. It has been assumed that the critical stress of the web of tapered beam could be calculated in an analogous way as for uniform member just with an additional correction factor αb.w. A large number of simulations carried out within a wide range of the ratios of second moments of area allowed to determine the proper values of that factor. In the paper there was investigated the influence of steel grade, relative slenderness and beam's ends cross‐section moments of inertia ratio to the local stability of web of the tapered beam subjected to pure bending. Santrauka Straipsnyje aprašyti teoriniai ir skaitmeniniai grynai lenkiamu trapeciniu siju sieneles vietinio pastovumo tyrimai. Kritinis apkrovos daugiklis gautas baigtiniu elementu metodo programa COSMOS/M. Atlikus teorinius tyrimus nustatyta, kad trapecines sijos sieneles vietini pastovuma galima apskaičiuoti kaip pastovaus skerspjūvio sijai naudojant papildoma koeficienta . Atlikus skaitinius eksperimentus kintant sijos galu skerspjūvio inercijos momentu santykiui, gautos tikslios šio koeficiento reikšmes. Straipsnyje nagrineta plieno klases, sijos sieneles salyginio liaunio ir sijos galu skerspjūvio inercijos momentu santykio itaka grynai lenkiamai trapecinei sijai.

Nonlinear buckling analysis of simple geometrically imperfect frames

In this paper, the effect of geometrical imperfections due to joint angle deviations of a simple rectangular frame is thoroughly discussed. It has been found that the deviation from the right angle of the joint with respect to the center-lines of the two members of the frame affects significantly the buckling strength of the frame. It is also shown that such geometrical imperfections do not always decrease the strength of such structures but sometimes, even though loading imperfections exist, they act on the favorable side regarding its strength. The influence of various geometric parameters such as slenderness ratio as well as length and moment of inertia ratio of the members on the critical load of the imperfect frame is thoroughly discussed and representative case studies are presented.

Genetic effects for femoral biomechanics, structure, and density in C57BL/6J and C3H/HeJ inbred mouse strains.

Genome-wide QTL analysis for bone density, structure, and biomechanical phenotypes was performed in 999 (B6xC3H)F2 mice. Multivariate phenotypes were also derived to test for pleiotropic QTL effects. Highly significant QTLs were detected with pleiotropic effects on many of these phenotypes, and QTLs with unique effects on specific phenotypes were found as well. The inbred C57BL/6J (B6) and C3H/HeJ (C3H) mouse strains were previously shown to segregate quantitative trait loci (QTLs) for femoral bone density. The 999 s filial (F2) mouse progeny were further phenotyped for measures of femoral biomechanics (load to failure, Fu; work to failure, U; stiffness, S), structure (polar moment of inertia, Ip; moment of inertia ratio, Ir), and more specific femoral midshaft bone density measures (cortical and total vBMD). Two novel multivariate phenotypes were computed using principal component analysis, thus aiding in the exploration of pleiotropic effects of the QTLs detected. Results of a genome-wide analysis provided strong evidence of pleiotropic QTL effects on chromosome 4, with six of the seven primary phenotypic measures, representing femoral biomechanics, density, and structure, producing LOD scores greater than 8. Chromosomes 1, 8, 13, and 14 were also identified as harboring QTLs that affect phenotypes in two of the three aspects of bone properties. QTLs uniquely contributing to variability in biomechanical measures were identified on chromosomes 10 and 12, whereas a QTL solely affecting structure was found on chromosome 17. Analysis of the evidence for pleiotropic effects using principal component analysis revealed pleiotropic QTLs on chromosomes 4 and 14, influencing nearly all the bone phenotypes measured and revealed QTLs on chromosomes 1, 8, 13, and 17 with pleiotropic effects restricted to either density or the structure and stiffness phenotypes. The use of multivariate phenotypes has allowed us to identify pleiotropic effects of several QTLs previously linked in studies of other mouse strains and in human studies of bone mineral density and femoral structure, which will provide important insight regarding the importance of allelic variation on the entire skeleton.

STABILITY OF AXIALLY LOADED TAPERED COLUMNS/CENTRIŠKAI GNIUŽDOMŲ TRAPECINIŲ KOLONŲ STABILUMAS

In this paper, theoretical analysis of tapered column's bearing capacity is presented. A slender axially loaded column loses stability, when it achieves critical load (1). Critical load for uniform column can be calculated using L. Euler's formula (3). But this formula is only for uniform members. When we have non-uniform member, column's moment of inertia about strong axis (Fig 3) chances according to law (4). A. N. Dinik [4] suggested a differential equation (6) for non-uniform axially loaded member. So the critical load of tapered column can be calculated as for uniform member with additional factor K using (7) formula. Factor Kdepends only on the moments of inertia ratio (5) of column ends. In this paper, critical load of tapered column was calculated using FE program COSMOS/M. A lot of simulation were carried out with a wide range of moments of inertia ratio. From these simulations factor K was calculated (Fig 4 and Table 1) for axially loaded pin-end column. By computer simulation it was determined that factor K for pin-end column can also be used for other types of column support. After determining critical load, column slenderness (10) can be calculated using column's smallest cross-section A 1. Tapered column must satisfy (12) condition. A couple of examples (Table 2) with various moments of inertia ratio was solved. Three calculation methods were used: the author's suggested (Fig 5 curve 1): using [1, 2] method as for uniform member with the smallest column's cross-section geometrical characteristics (Fig 5 curve 2); and using [1, 2] method as for uniform member with average column's cross-section geometrical characteristics (Fig 5 curve 3). From Fig 5 we see that calculation of tapered column using methods for uniform members with average cross-section geometrical characteristics is not safe.

STABILITY OF AXIALLY LOADED TAPERED COLUMNS

Summary In this paper, theoretical analysis of tapered column's bearing capacity is presented. A slender axially loaded column loses stability, when it achieves critical load (1). Critical load for uniform column can be calculated using L. Euler's formula (3). But this formula is only for uniform members. When we have non-uniform member, column's moment of inertia about strong axis (Fig 3) chances according to law (4). A. N. Dinik [4] suggested a differential equation (6) for non-uniform axially loaded member. So the critical load of tapered column can be calculated as for uniform member with additional factor K using (7) formula. Factor K depends only on the moments of inertia ratio (5) of column ends. In this paper, critical load of tapered column was calculated using FE program COSMOS/M. A lot of simulation were carried out with a wide range of moments of inertia ratio. From these simulations factor K was calculated (Fig 4 and Table 1) for axially loaded pin-end column. By computer simulation it was de...

Verification of the effectiveness of TMDs using wind tunnel section model tests

Abstract Wind tunnel tests for the Hoga Kusten Bridge, now under construction in Sweden, have suggested that the bridge will experience large torsional motions for the particular case of snow accumulated in the railings. The designers of the bridge proposed the use of tuned mass dampers (TMDs) to reduce these motions, thus ensuring the safety of the bridge for wind speeds above approximately 40 m/s. The effectiveness of the TMDs was tested in a wind tunnel at the Danish Maritime Institute (DMI) through section model tests, with the aim of optimizing the TMD design. Tests have shown the TMDs to be highly effective, reducing the RMS torsional motions of the deck by a factor of almost 10. Tests varying many parameters of the TMD design were conducted to optimize the TMD design; the greatest improvement in bridge deck performance was achieved by increasing the TMD mass moment of inertia ratio either by increasing the distance from the TMDs to the bridge centreline or by increasing the moving mass of the TMD.

On the Development of Control Laws for an Orbiting Tethered Antenna / Reflector System Test Scale Model

Tethered systems can be used to change the geometry and inertial characteristics of space structural systems to meet the gravity gradient stability requirements. The control law design for an orbiting shallow spherical shell (antenna/reflector) system connected by a massive and flexible tether to a subsatellite is investigated in this article. The subsatellite is nominally deployed below the antenna along the yaw axis at a sufficient distance to provide a favorable composite moment of inertia ratio for gravitational stabilization. It is assumed that the tether would be deployed through the end of a rigid boom attached to the shell apex. The tension control strategy is used for stationkeeping and deployment and the control gains are obtained based on the structural data for a future proposed real space antenna/reflector. In order to prove the feasibility of this concept, a test scale model for an in-orbit experiment is also studied. The scale model should be small enough so that it could be accommodated within the volume and size limitations of the space shuttle cargo bay. Since the or bital angular velocity (determined by the orbital altitude of the space shuttle), tether diameter, etc. may not be directly scaled, the control gains will be adjusted to fit the requirements for the scale model. Furthermore, during the deployment, the real control gains will be adjusted to the change of the length of the tether and the deployed tether mass. Therefore, the control law gains for the pro posed in-orbit experiment scale model would be synthesized in a piece-wise adaptive manner. Nu merical results are presented both for the real antenna as well as for the proposed in-orbit (test) scale model.

Nonlinear sway-buckling of geometrically imperfect rectangular frames

By using as model an unbraced rectangular frame, the effect of geometric imperfections due to right angle deviations is thoroughly discussed. It is found that the value of the angle between the center lines of the two members is of decisive importance for the response of the frame. There is a critical angle for which the response of the frame changes from buckling to unbuckled states exhibiting a monotonically rising equilibrium path. It is shown that this critical angle depends on the column slenderness ratio as well as on the length and moment of inertia ratio of the two members. Moreover, formulas for direct evaluation of the critical angle as well as of the load-carrying capacity of the frame are established.

The Effects of Initial Curvature and Other Parameters on the Nonlinear Buckling of Simple Frames*

ABSTRACT In this investigation a nonlinear variational analysis is performed on a simple two-bar frame with initially crooked bars that is subjected to an eccentrically applied load at its joint. The influence of crookedness may be detrimental or beneficial, depending on the manner of design of the frame. It is also found that for some critical value of crookedness, the frame does not buckle elastically. Moreover, it is shown that for some characteristic values of the length ratio and moment of inertia ratio of the two bars, the load-carrying capacity of the frame becomes maximum. Finally, the combined effect of the aforementioned parameters is discussed

The moon: Composition determined by nebular processes

The bulk composition of the Moon was determined by the conditions in the solar nebula during its formation, and may be quantitatively estimated from the premise that the terrestrial planets were formed by cosmochemical processes similar to those recorded in the chondrites. The calculations are based on the Ganapathy-Anders 7-component model using trace element indicators, but incorportate improved geophysical data and petrological constraints. A model Moon with 40 ppb U, a core 2% by weight (1.8% metal with ∼35% Ni and 0.2% FeS) and Mg/(Fe2++Mg)Δ∼0.75 meets the trace element restrictions, and has acceptable density, heat flow and moment of inertia ratio. The high Ni content of the core permits low-Ti mare basalts to equilibrate with metal, yet still retain substantial Ni. The silicate resembles the Taylor-Jakes composition (and in some respects the waif Ganapathy-Anders Model 2a), but has lower SiO2. Minor modifications of the model composition (U=30–35 ppb) yield a 50% melt approximating Apollo 15 green glass and a residuum of olivine plus 3 to 4% spinel; the low SiO2, favors spinel formation, and, contrary to expectation, Cr is not depleted in the liquid. There may no longer be any inconsistency between the cosmochemical approach and arguments based on experimental petrology.

Nonlinear sway-buckling of an eccentrically loaded frame of two timoshenko-bars

A variational method for investigating the nonlinear lateral stability is applied to a rectangular, geometrically perfect, two-bar frame which is loaded eccentrically to the center line of one of the bars. The frame loses its stability through a limit point. The individual, and primarily the coupling effects on the nonlinear sway-buckling load are fully assessed for a variety of parameters such as transverse shear deformation, cross-sectional shape, loading eccentricity, slenderness ratio and moment of inertia ratio of the two bars. The conclusions presented herein give a better insight into the actual response of the frame.

Vibration Frequencies for a Uniform Beam With One End Elastically Supported and Carrying a Mass at the Other End

In this paper the author obtains the frequency equation for the normal modes of vibration of uniform beams with linear translational and rotational springs at one end and having a concentrated mass at the other free end. The eigenfrequencies for the fundamental mode are given for a wide range of values of mass ratio, mass moment of inertia ratios, and stiffness ratios.