Thin Cylindrical Rod Research Articles

Non-contact mechanical Q-factor measurement system based on electromagnetic acoustic transducer

The mechanical quality factor (Q-factor), which is the reciprocal of the vibration loss constant, is one of the most important parameters in vibration engineering; however, there are no methods for its precise measurement. Q-factor databases are thus commonly used. This study proposes a completely non-contact measurement system for the Q-factor that combines non-contact excitation (achieved using an electromagnetic acoustic transducer) with non-contact support (achieved using near-field ultrasonic levitation based on two Langevin transducers). The proposed method was used to measure the Q-factor for a stainless steel (SUS304) sample (thin cylindrical rod with a diameter of 1.5 mm and a length of 80 mm)and a duralumin (A2017). The 5 times average Q-factor was 2010 with standard deviation of 50 for stainless steel (SUS304), and 49,000 with standard deviation of 3900 for duralumin (A2017). The proposed method also allowed for the measurement of Young’s modulus, resulting in 217.17 ± 0.34 GPa for stainless steel (SUS304), and 71.39 ± 0.20 GPa for duralumin (A2017).

Gasdynamic and Acoustic Characteristics of a Subsonic Jet-Edge Rod Generator of Acoustic Radiation

The design of a subsonic jet-edge rod generator of the Hartmann-type oscillator and a scheme of measuring its acoustic parameters are presented. In this generator, unlike the Hartmann oscillator, not a cylindrical gas jet but an annular gas jet, moving along the thin cylindrical rod positioned at the axis of the generator nozzle, is used. A parametric investigation of the gasdynamic and acoustic processes arising in the tubular cavity of such a generator as a result of the interaction of a subsonic gas jet with this cavity has been performed with consideration for the nonstationary structure of the gas flow in the generator cavity. Recommendations on the choice of the design of a jet-edge rod generator of acoustic radiation with regard for its practical application are given.

Research on Attenuation of Shock Induced Stress Wave in Multi-Layered Thin Cylindrical Rods

The attenuation of stress wave induced by impact load in multi-layered thin cylindrical rods has been investigated and analyzed. Firstly, based on stress wave propagation theory, the one dimension solution of the response of stress wave in three-layered media has been given. Secondly, a three-layered thin cylindrical rod has been established through FEM, and the propagation and attenuation of stress wave in it has been analyzed. The analytical and numerical results showed that the stress wave attenuation could be achieved by using multi-layered media.

Stabilization of an X-Y inverted pendulum using adaptive gain scheduling PID controllers

An X − Y inverted pendulum, also known as a spherical or a two-dimensional inverted pendulum consists of a thin cylindrical rod attached to a base through a universal joint. The control objective is to place the pendulum in the upright position while keeping the base at some desired reference trajectory. This paper presents an adaptive gain scheduling method in designing PID controllers for the stabilization of an X − Y inverted pendulum. The variations in PID gains depend upon the transient and the steady-state part of the response. The performance of the proposed scheme has been compared with the conventional PID scheme given in the literature. The effectiveness of the proposed scheme under the effect of disturbance, noise and friction in the inverted pendulum system has also been studied. Simulation results show that the proposed controllers provide better performance than the conventional PID controllers in terms of various performance specifications.

Scalar boundary value problems on junctions of thin rods and plates

We derive asymptotic formulas for the solutions of the mixed boundary value problem for the Poisson equation on the union of a thin cylindrical plate and several thin cylindrical rods. One of the ends of each rod is set into a hole in the plate and the other one is supplied with the Dirichlet condition. The Neumann conditions are imposed on the whole remaining part of the boundary. Elements of the junction are assumed to have contrasting properties so that the small parameter, i.e. the relative thickness, appears in the differential equation, too, while the asymptotic structures crucially depend on the contrastness ratio. Asymptotic error estimates are derived in anisotropic weighted Sobolev norms.

Three dimensional considerations in thermal-hydraulics of helical cruciform fuel rods for LWR power uprates

In order to increase the power density of current and new light water reactor designs, the helical cruciform fuel (HCF) rods have been proposed. The HCF rod is equivalent to a thin cylindrical rod, with 4 fuel containing vanes, wrapped around it. The HCF rods increase the surface area to volume ratio of the fuel and enhance the inter-subchannel mixing due to their helical shape. The rods do not need supporting grids, as they are packed to periodically contact their neighbors along the flow direction, enabling a higher power density in the core. The HCF rods were reported to have the potential to uprate existing PWRs by 45% and BWRs by 20%. In order to quantify the mixing behavior of the HCF rods based on their twist pitch, experiments were previously performed at atmospheric pressures with single phase water in a 4 by 4 HCF and cylindrical rod bundles. In this paper, the experimental results on pressure drop and mixing are benchmarked with computational fluid dynamic (CFD) using steady state the Reynolds average Navier–Stokes (RANS) turbulence model. The sensitivity of the CFD approach to computational domain, mesh size, mesh shape and RANS turbulence models are examined against the experimental conditions. Due to the refined radial velocity profile from the HCF rods twist, the turbulence models showed little sensitivity to the domain. Based on the CFD simulations, the total pressure drops under the PWR and BWR conditions are expected to be about 10% higher than the values previously reported solely from an empirical correlation based on the experimental data. The impact of 3D conduction in the HCF rods is shown to be negligible under steady state but significant under transient conditions.

Torsion instability of soft solid cylinders

The application of pure torsion to a long and thin cylindrical rod is known to provoke a twisting instability, evolving from an initial kink to a knot. In the torsional parallel-plate rheometry of stubby cylinders, the geometrical constraints impose zero displacement of the axis of the cylinder, preventing the occurrence of such twisting instability. Under these experimental conditions, wrinkles occur on the cylinder's surface at a given critical angle of torsion. Here we investigate this subclass of elastic instability--which we call torsion instability--of soft cylinders subject to a combined finite axial stretch and torsion, by applying the theory of incremental elastic deformation superimposed on finite strains. We formulate the incremental boundary elastic problem in the Stroh differential form, and use the surface impedance method to build a robust numerical procedure for deriving the marginal stability curves. We present the results for a Mooney-Rivlin material and study the influence of the material parameters on the elastic bifurcation.

Natural Convection Heat Transfer in a Horizontal Porous Enclosure with High Porosity

Heat transfer characteristics near the critical Rayleigh number for the onset of natural convection of horizontal anisotropic porous fluid layer heated from below with thin cylindrical rods inserted with high porosity above 0.822 to unity were studied by an analysis and an experiment. The critical Rayleight number Rac and dependence of Nusselt number on the Rayleight number were analysed by linear stability theory and series expansion method on the basis of Darcy flow assumption. Critical Rayleight number, increased with decrease in the porosity, was higher for the experiment than for the analysis but the difference was decreased with decrease in Darcy number. Experimental Nusselt number was considerably decreased with decrease in the porosity near unity although Rac is rather same as the case of Benard convection without cylindrical rods. The experimental Nusselt number can be expressed by one correlation curve when Nusselt number is plotted against Ra/Rac Darcy number of the present experiment was rather large to satisfy Darcy flow assumption. Experiment shows that Darcy flow assumption will be satisfied for Darcy number ?2×10-3.

Rate-dependent losses modeling for magnetostrictive actuators

Abstract The present paper tackles the magnetic field diffusion analysis in thin cylindrical rods of materials showing hysteresis effects and employed in commercial actuators. The problem is formulated in terms of magnetic vector potential. By this formulation the used magnetic constitutive relationship assumes magnetic induction as input. Since almost all of the hysteresis models that can be employed (like the Preisach model) to describe the B–H characteristic assume H as input field, the inversion of the hysteresis operator at each step is required. The alternative approach is to assume B as input field, by using an approximate version of the Preisach hysteresis operator as constitutive relation in a finite element eddy current model. This approach is quite new and sensibly reduces the computational effort, since it avoids the inversion of the hysteresis operator at each time step. The numerical results are provided and compared to experimental data on a commercial Terfenol-D actuator.

Propagation of sound in a thin cylindrical rod immersed in a fluid

Propagation of sound in a thin cylindrical rod immersed in a fluid

Lateral capillary forces measured by torsion microbalance.

The forces of capillary interaction between two thin cylindrical rods or two spherical particles placed at a liquid/air interface and immersed partially in the liquid are measured by a sensitive torsion microbalance. Cylindrical rods of radii 50, 165, and 365 \ensuremath{\mu}m are used. The spheres have radius 600 \ensuremath{\mu}m; they are modeling the lateral interaction between colloidal particles trapped in a thin liquid film. The measured forces range in magnitude between ${10}^{\ensuremath{-}4}$ and ${10}^{\ensuremath{-}9}\mathrm{N}$ depending on the particle size and the interparticle distance. The experimental data agree well with the theory of capillary immersion forces.

Resolution of the discrepancy between temperature indicated interface and radiographically determined interface in a vertical Bridgman furnace

The melt-solid interface position was measured during the Bridgman growth of germanium both by X-ray imaging and by temperature measurements. X-ray imaging displayed an interface location through a change in image intensity representing the difference in density between liquid and solid germanium. The temperature measurements were obtained with thermocouples inserted into a centerline capillary tube in the germanium sample and translated to varying positions. The temperature profile indicated an interface location at the change in slope of temperature representing the difference in thermal conductivity between liquid and solid germanium. Comparisons between these measurement techniques showed a 3 mm difference in position of the interface. The position measured via radiography was lower (i.e. colder) than that measured by the temperature profile. The measured temperature was expected to be lower due to conduction of heat along the thermocouples but a spatial shift of the gradient discontinuity was not anticipated. The temperature field of the ampoule, growth material and measurement thermocouples was analyzed via numerical analysis. It was found that both the lower temperature and the spatial shift of the discontinuity in temperature gradient were a result of an end effect in the thermocouples. This end effect is caused by the low heat flux to the thermocouples which causes the temperature gradient at the tip of the thermocouples to be significantly lower than the temperature gradient of the environment. With this insight, a simple extension was made to the heat equation for a thin cylindrical rod in a temperature gradient. This analytical solution provided a good fit to both the numerical solution and the radiography data. This work provides a new insight into temperature measurement in a high gradient region.

A New Method for Measuring the Low-Temperature Dielectric Property of a Low-Loss Material with a Superconducting Resonant Cavity

A superconducting 6.5 GHz cylindrical TE011 mode cavity was used to measure the small dielectric loss of polytetrafluoroethylene at liquid helium temperature. First, the Q value and the resonance frequency of the unperturbed niobium cavity was measured by the decrement method. Then a thin cylindrical rod sample, suspended from the magnetic loop, was inserted into it through the coupling port. By the use of a gate valve and a vacuum by-pass the sample can be drawn out and reassembled without introducing air into the cavity. From the decrease of the Q value and the shift of the resonance frequency, the complex dielectric constant was obtained (ε'/ε0=1.9 and ε''/ε0=4.4×10-6 at 1.3 K). Loss tangent tan δ was estimated as 2.4×10-6.

An improved crystal-mounting technique for X-ray diffraction work

The usual goniometer head is often not suitable for use on a four-circle diffractometer because it obstructs the incident of reflected X-ray beams. A range of settings of the circles may be made impossible because of collisions between the goniometer head and the collimator. To overcome this difficulty the crystal is first orientated on the usual goniometer head, using photographic or diffractometric equipment, and then transferred to a support consisting of a single thin cylindrical rod. The apparatus for this purpose consists of two collinear axles provided with standard goniometer head bases. The crystal is mounted on a glass fibre and a method is described by which the fibre and crystal may be transferred from one head to the other without change of orientation relative to the common axis of the axles.

Some results on the frequencies of nonhomogeneous rods

In this paper we consider the transverse vibrations of a thin cylindrical rod of variable density and constant f lexural r igidity which is clamped at both ends. In Section I we prove two results on the principal frequency of these rods. These theorems are analogous to theorems on the principal frequency of nonhomogeneous strings. Theorem 1 corresponds to a result of Beesack [1] and Theorem 2 to a result of Krein [2]. In Section I I we consider nonhomogeneous clamped rods with equimeasurable density and we prove an inequality for the min imum of the nth frequency (n =2~). This Theorem 3 should be compared with a much stronger statement on the extrema of the frequencies of equimeasurable strings. We rely heavily upon results of Beesack [1, 3]. Notation and methods are similar to those used in our paper on nonhomogeneous strings [4].