Cylindrical Bar Research Articles

Non-uniform impact excitation of a cylindrical bar

An experimental and numerical study of a non-uniform impact excitation of a circular bar is reported. In experiments, nine strikers with different contact area were accelerated against a circular bar. Axial surface strain of the impacted bar was measured at several distances from the impinged end to include the near and the far fields. The same experimental conditions were solved numerically using a commercial finite element code. It was demonstrated that the far-field response is insensitive to both the size and the form of the striker's colliding end. The distance at which such insensitivity is set is estimated to be approximately one and a half bar diameters.

Effect of axial restraint in composite bars under nonlinear inelastic uniform torsion by BEM

In this paper, the effect of axial restraint in the elastic–plastic uniform torsion analysis of cylindrical bars taking into account the effect of geometric nonlinearity is presented employing the boundary element method. The bar is axially elastically supported at the centroids of its end cross sections, treating the cases of free axial boundary conditions (vanishing axial force), restrained axial shortening or given axial force as special ones. The cross section of the bar is an arbitrary doubly symmetric composite one, consisting of materials in contact, each of which can surround a finite number of inclusions, while the case of a homogeneous cross section is treated as a special one. The stress–strain relationships for the materials are assumed to be elastic–plastic-strain hardening. The incremental torque–rotation relationship is computed based on the finite displacement (finite rotation) theory, that is the transverse displacement components are expressed so as to be valid for large rotations and the longitudinal normal strain includes the second-order geometrically nonlinear term, often described as the “Wagner strain”. The proposed formulation does not stand on the assumption of a thin-walled structure and therefore the cross section’s torsional rigidity is evaluated exactly without using the so-called Saint-Venant’s torsional constant. The torsional rigidity of the cross section is evaluated directly employing the primary warping function of the cross section depending on both its shape and the progress of the plastic region. A boundary value problem with respect to the aforementioned function is formulated and solved employing a BEM approach. The developed procedure retains most of the advantages of a BEM solution over a pure domain discretization method, although it requires domain discretization, which is used only to evaluate integrals. The significant increase of the torsional rigidity of the bar and the arising axial force due to the axial restraint are concluded.

Nonlinear inelastic uniform torsion of composite bars by BEM

In this paper the elastic–plastic uniform torsion analysis of composite cylindrical bars of arbitrary cross-section consisting of materials in contact, each of which can surround a finite number of inclusions, taking into account the effect of geometric nonlinearity is presented employing the boundary element method. The stress–strain relationships for the materials are assumed to be elastic–plastic–strain hardening. The incremental torque–rotation relationship is computed based on the finite displacement (finite rotation) theory, that is the transverse displacement components are expressed so as to be valid for large rotations and the longitudinal normal strain includes the second-order geometric nonlinear term often described as the “Wagner strain”. The proposed formulation does not stand on the assumption of a thin-walled structure and therefore the cross-section’s torsional rigidity is evaluated exactly without using the so-called Saint Venant’s torsional constant. The torsional rigidity of the cross-section is evaluated directly employing the primary warping function of the cross-section depending on both its shape and the progress of the plastic region. A boundary value problem with respect to the aforementioned function is formulated and solved employing a BEM approach. The influence of the second Piola–Kirchhoff normal stress component to the plastic/elastic moment ratio in uniform inelastic torsion is demonstrated.

Strain-Concentration Factor of Circumferentially V-Notched Cylindrical Bars Under Static Tension

AbstractThe FEM is used to study the effects of notch opening angle (β) and notch radius on the new strain-concentration factor (SNCF) for circumferentially V-notched cylindrical bars under static tension. The new SNCF has been defined under the triaxial stress state at the net section. Nevertheless, the conventional SNCF has been defined under uniaxial stress state. The new SNCF () is constant in the elastic deformation. The range where this elastic value remains constant increases with increasing β and increasing notch radius (ρo). The effect of the notch opening angle on the elastic decreases with increasing ρo. Particularly, the elastic of β = 120° is the minimum for all notch radii employed. The new SNCF increases from its elastic value to a peak value and then decreases with plastic deformation for notches with β = 120°. This peak value is the maximum . Nevertheless, for the notches with β < 120° becomes nearly constant or slightly decreasing after the first peak for ρo = 0.5 and 1mm. After that it increases to the maximum SNCF and then slightly decreases for further plastic deformation. The variations in with the ratio of tensile load to that at yielding at the notch root (P/PY) are nearly independent of stress-strain curve up to general yielding.

LNG차량용 연료탱크의 지지시스템 구조해석에 관한 연구

Recently the LNG(liquified natural gas) public buses have been introduced to prevent the air pollution in metropolitan areas. As the LNG temperature in fuel tank is as low as -162℃, the thermal and structural effects of tank components need to be studied for safe introduction in the market. Especially the support system of LNG fuel tank in vehicle, which has connected with inside and outside of tanks, should put attention to reduce the structural stress due to cryogenic temperature and to restrict the heat flux from ambient. There are two supporting systems in the tank, that one is connected between inside and outside tanks by welding, and the other is the inserted support system which is a cylindrical SUS bar inserted in a hole of the supporting plate. In this study the temperature distribution and thermal stress of the inserted support system were evaluated by using the utility program as ANSYS. The results showed that the rate of heat transfer to inner tank through this support system was quite small due to limited contact of support bar with plate, but the thermal stress of support plate was obtained beyond the limited tensile value of SUS304. The cautious design for the support plate part, therefore, should be given to make the safe support system of LNG vehicle fuel tank.

Numerical simulation of heat transfer of latent functionally thermal fluid in tubes with coaxially inserted cylindrical bars in laminar

The heat transfer of latent functionally thermal fluid in three kinds of tubes with coaxially inserted cylindrical bars is numerically researched using equivalent specific heat model, and the flow fields are analyzed with field synergy field. It is found that in the tubes with coaxially inserted cylindrical bars, the heat transfer effects of functionally thermal fluid become more and more pronounced with the Ste decreasing. This is similar to be case of functionally thermal fluid flowing in smooth straight tubes. Compared with the results receiving from smooth straight tubes, the heat transfer of functional thermal fluid in tubes with coaxially inserted cylindrical bars has been significantly enhanced. And this effect becomes more apparent as the diameter of coaxially inserted cylindrical bars increases meanwhile, however, energy consuming of the tubes shows the same trend.

Pendellösung phenomenon in two-dimensional sonic crystals

The phenomenon of "Pendelösung" oscillations, which is well known in X-ray diffraction [P.P. Ewald, Phys. Z. 14, 465 (1913); Ann. Phys. 54, 519 (1917); Rev. Mod. Phys. 37, 189 (1965)] is predicted here and experimentally verified for the case of two-dimensional sonic crystals made of hexagonal arrays of fluidlike cylindrical bars embedded in water. The dependence of diffraction intensity is studied as a function of layer thickness; i.e., of the layer number N. Nearly periodic oscillations have been observed at specific frequencies and the oscillation period is also a function of the frequency. The periodic behaviour is evidence of the exchange of energy between two modes in the sonic crystal. [Work supported by MEC of Spain.]

Development of an aspheric 22-diopter 50-mm diameter magnifier

To develop in an interdisciplinary approach between ophthalmology and design areas an ergonomic +22-diopter 50-mm aspheric hand magnifier for low vision. An aluminum cylinder was cut, processed using a lathe and carved to produce a ring that accommodated a 50-mm aspheric lens, with an external depression not to slide from the holder's fingers. A cylindrical steel bar was cut, processed using a lathe and carved in order to form an externally turned ring to be screwed into the internal thread of the aluminum ring, to maintain the lens in a steady position. Both rings were submitted to electrostatic painting with a dull black electrostatic Epoxi ink, except the lower border of the external ring, to indicate the correct side of the magnifier to face the material to be read. A 22-diopter 50-mm diameter aspheric lens magnifier with a black ring to be hold at its external circular depression was obtained in order to safely search the adequate reading focus with an inferior aluminum colored ring to face the object to be read and allow a less distorted reading. This is the first Brazilian high-magnification great-diameter magnifier for low vision that permits basically the focusing on an entire word, not only syllables, in order to allow a faster and more comfortable reading. By an interdisciplinary approach a 22-diopter 50-mm aspheric lens magnifier was developed with image and ergonomic characteristics such as to permit comfortable and adequate reading performance in cases of low vision.

Estimation of heat generation at the interface of cylindrical bars during friction process

In this study, an inverse algorithm based on the conjugate gradient method and the discrepancy principle is applied to estimate the unknown time-dependent heat generation at the interface of cylindrical bars during friction process from the knowledge of temperature measurements taken within the bar. It is assumed that no prior information is available on the functional form of the unknown heat generation; hence the procedure is classified as the function estimation in inverse calculation. The temperature data obtained from the direct problem are used to simulate the temperature measurements, and the effect of the errors in these measurements upon the precision of the estimated results is also considered. Results show that an excellent estimation on the time-dependent heat generation can be obtained for the test case considered in this study. The current methodology can be applied to the prediction of heat generation in continuous-drive friction welding or in breaking systems.

Thermal performance of a premixed impinging circular flame jet array with induced-swirl

An array of three identical premixed butane–air-fired impinging circular flames with induced-swirl operating at low-pressure and low-Reynolds-number was developed. A swirling motion was imparted successfully to the flame by forcing the butane/air mixture through a specially designed burner assembly before ignition. The burner assembly consisting of a conical base and a nozzle tube into which a cylindrical bar fabricated with three spiral channels was inserted. Its thermal performance was compared with that of a similar impinging flame jet system without induced-swirl. Effects of varying the Reynolds number and the equivalence ratio of the butane/air mixture and the nozzle-to-plate distance on the thermal performance of each of these two impinging flame jet systems were studied. Experiments were conducted with different combinations of Reynolds number, equivalence ratio and nozzle-to-plate distance. In the present investigation, the Reynolds number ranged from 500 to 2500, the equivalence ratio ranged from 1.0 to 1.8 and the nozzle-to-plate distance ranged from 20 mm to 30 mm. To facilitate comparison, flame shapes of both impinging flame jet systems were also visualized by a high speed digital camera system. The comparison showed that the array of three small-scale, low-pressure and low-Reynolds-number premixed butane–air-fired impinging circular flame jets could enhance its thermal performance, with respect to heat transfer characteristics and blow-out limits, by incorporating an induced-swirl. The performance enhancement increased with increasing Reynolds number or equivalence ratio, but decreased with increasing nozzle-to-plate distance.

A simple, small and low cost permanent magnet design to produce homogeneous magnetic fields

A new portable, pocket-size NMR probe based on a novel permanent magnet arrangement is presented. It is based on a Halbach-type magnet design which mimics the field of a spherical dipole by using cylindrical bar and ring magnets. The magnet system is made up of only three individual magnets, and most field calculations and optimisations can be performed analytically. A prototype system has been built using a set of small, off the shelf commercially available permanent magnets. Proton linewidths of 50 ppm FWHM could be achieved at a field strength of 1 T. Calculations show that with custom-sized permanent magnets, linewidths of less than 1 ppm can be achieved over sample volumes of up to 1 mm 3, which would in theory enable chemical shift resolved proton spectroscopy on mass-limited samples. But even with the achieved linewidth of 50 ppm, this can be a useful portable sensor for small amounts of liquid samples with restricted molecular mobility, like gels, polymers or high viscosity liquids.

Wave Absorber by Using Cylindrical Bars with Magnetic Loss Covers Arranged Metallic Mesh for Improving ETC Environment

The wave absorber composed of cylindrical bars arranged periodically and metallic mesh for improving visibility is proposed for ETC, and characteristics of reflectivity and shielding effect are evaluated analytically and experimentally. As a result, reflectivity of -10dB and shielding effect of -25dB are obtained for circularly polarized wave when the gap between cylindrical bars is 30mm. Therefore, realization of proposed wave absorber for installing between ETC lanes can be clarified.

Nonlinear inelastic uniform torsion of bars by BEM

In this paper the elastic–plastic uniform torsion analysis of simply or multiply connected cylindrical bars of arbitrary cross-section taking into account the effect of geometric nonlinearity is presented employing the boundary element method. The stress–strain relationship for the material is assumed to be elastic–plastic–strain hardening. The incremental torque–rotation relationship is computed based on the finite displacement (finite rotation) theory, that is the transverse displacement components are expressed so as to be valid for large rotations and the longitudinal normal strain includes the second-order geometric nonlinear term often described as the “Wagner strain”. The proposed formulation does not stand on the assumption of a thin-walled structure and therefore the cross-section’s torsional rigidity is evaluated exactly without using the so-called Saint-Venant’s torsional constant. The torsional rigidity of the cross-section is evaluated directly employing the primary warping function of the cross-section depending on both its shape and the progress of the plastic region. A boundary value problem with respect to the aforementioned function is formulated and solved employing a BEM approach. The influence of the second Piola–Kirchhoff normal stress component to the plastic/elastic moment ratio in uniform inelastic torsion is demonstrated. The developed procedure retains most of the advantages of a BEM solution over a pure domain discretization method, although it requires domain discretization, which is used only to evaluate integrals.

Studies on High-Lift LP Turbine Airfoils of Aero Engines (Understanding of Boundary Layer Transitional Behaviour on Time-Space Diagram under the High Lift and Ultra High Lift Conditions)

This paper details experimental studies on the flow field around a linear cascade of low-pressure turbine airfoils whose solidity is changeable. Highly loaded low-pressure turbine (LPT) blades are one of the key paths to successful future aero-engines, however these blades are usually accompanied with separation bubble, eventually leading to the increase in aerodynamic performance. The purpose of this study is therefore to clarify any favorable effects of incoming wakes upon the aerodynamic loss of high-lift or ultra high-lift rotor blade cascade through the measurements of wake-affected boundary layers including separation bubble under low Reynolds number conditions. Cylindrical bars on the timing belts work as wake generator to emulate upstream stator wakes that impact the rotor blade. Hot-wire probe measurement is conducted over the blade suction surface to understand to what extent and how the incoming wakes affect the boundary layers containing separation bubble. Time-dependent transitional behaviors due to the wake passing are examined through the detailed inspection of several composite maps of flow properties displayed on time-space diagrams.

Viscoelastic impact between a cylindrical striker and a long cylindrical bar

Viscoelastic impact between a cylindrical striker and a long cylindrical bar

Studies on High-Lift LP Turbine Airfoils of Aero Engines (Understanding of Time-Averaged Behaviour of Separated Boundary Layer under the Influence of Incoming Wakes)

This paper details experimental studies on the flow field around a low-pressure linear turbine cascade whose solidity is changeable. Highly loaded low-pressure turbine (LPT) blades or ultrahigh lift airfoils are one of the key paths to successful future aero-engines, however those blades are usually accompanied with separation bubble, eventually leading to the increase in aero dynamic loss. The purpose of this study is to clarify the effect of incoming wakes upon the aerodynamic loss of the rotor blade cascade, through the measurements of wake-affected boundary layers upon including separation bubble for low Reynolds number conditions and/or low solidity conditions. Cylindrical bars on the timing belts work as wake generator to emulate upstream stator wakes that impact the rotor blade. Hot-wire probe measurement is conducted over the blade suction surface to understand to what extent and how the incoming wakes affect the boundary layers containing separation bubble. In particular, from the viewpoint of providing database for blade designing, this paper focuses on time-averaged characteristics of the separated boundary layer influenced by the wake passing.

직하형 Back Light Unit에 사용하는 변형 막대프리즘의 1차원 배열로 구성한 새로운 BLU 필름

A new sheet of back light unit(BLU) to reduce the number of sheets and enhance the optical performances of direct back light unit(BLU) in a liquid crystal display is proposed and designed. In order to improve the straightness and spatial uniformity of brightness of the BLU, we design the new sheet with linear arrays of complicated bar prism by using the fusion of cylindrical lens and bar prism. Then, we investigate and analyze various optical performances of a BLU including the new sheet through an illumination optical system design program. From these results, we determine the optimum geometrical structure of the sheet. Under the optimum condition, the luminance efficiency and spatial uniformity of luminance of the BLU are 53.5% and 83.5% respectively. And the vertical and horizontal widths of the angular luminance distribution are and respectively. Finally we have fabricated a new BLU sheet according to this design shape by using an ordinary resins.

Green’s function for KI determination of axisymmetric elastic solids containing external circular crack

A new Green’s function is derived to determine the mode-I stress intensity factor for axisymmetric solids containing external circular crack. The formulated boundary integral equation is applied to a finite cylindrical bar with an external crack, and the obtained solution is compared with existing published results, indicating good agreement. The proposed method compared with the finite element method or the conventional application of the boundary element method provides the following main advantages: (a) it does not require discretization of the crack surface, (b) it does not require multi-region modeling and (c) it reduces the 3-D discretization of the solid to 1-D resulting in substantially reduced effort.

Modelling of the plastic flow of trip-aided multiphase steel based on an incremental mean-field approach

An incremental mean-field model is developed for the prediction of transformation induced plasticity (TRIP) in multiphase steel. The partitioning of strain between softer and harder constituents is computed based on an elastic-plastic Mori–Tanaka approach that accounts for the progressive transformation of austenite into martensite. The latter transformation is predicted using an energy-balance criterion that is formulated at the level of individual austenite grains. The model has been tested against experimental data. Macroscopic stress-strain curves and rate of martensite formation have been measured on sheet samples subjected to various loading modes: uniaxial tension, simple shear, and (in-plane) uniaxial compression. These experiments were performed at 20 °C and the uniaxial tensile test was repeated at −30 °C. The mean-field model produces fair predictions of the macroscopic hardening resulting from TRIP on the condition that a sufficient proportion of the load is carried by the very hard martensite inclusions. Such prediction implies that one accounts for the stress heterogeneity across the ferrite-based matrix. At the same time, the model reproduces the elastic lattice strains and the plastic elongation which are measured within the phases by neutron diffraction and by image correlation in a scanning electron microscope, respectively. The model can be used in finite element simulations of forming processes which is illustrated in a study of necking of a cylindrical bar under uniaxial tension.

The initial values method for buckling of nonlocal bars with application in nanotechnology

In this work, the buckling of a bar is investigated by using the method of initial values within the framework of nonlocal elasticity. The principal matrix required for the applicability of the method of initial values is presented. The critical loads for bars with various kind of supports are found. As is well known that nanotechnology is the engineering of functional systems at the molecular scale. Carbon nanotubes are molecular-scale tubes which are figured as hollow cylindrical bars of graphitic carbon at molecular scale with outstanding properties. They are among the stiffest and strongest fibers known, and have remarkable electronic properties and many other unique characteristics. They are widely used in nanotechnological applications. The results are used to display that nonlocal effects could be significant in buckling of carbon nanotubes.