Hollow Cylindrical Tube Research Articles

Cylindrical Bidirectional Strain Sensors Based on Fiber Bragg Grating.

To realize continuous real-time monitoring of the large-scale internal strain field of coal and rock mass, a bidirectional strain sensor based on FBGs encapsulated using a hollow cylindrical steel tube was designed. The sensor’s structural parameters were optimized through unidirectional loading, and the strain change laws of the sensor were analyzed under unidirectional and bidirectional loading conditions, in which the stress-strain fitting curves of the sensor and the relationships of the strain in the vertical and horizontal directions were obtained under different lateral pressure loading conditions. A similar theoretical model was established to verify the accuracy of the linear relationship between the surrounding rock stress and the strain measured by the sensor system.

MR-Tracked Deflectable Stylet for Gynecologic Brachytherapy.

Brachytherapy is a radiation based treatment that is implemented by precisely placing focused radiation sources into tumors. In advanced interstitial cervical cancer bracytherapy treatment, this is performed by placing a metallic rod ("stylet") inside a hollow cylindrical tube ("catheter") and advancing the pair to the desired target. The stylet is removed once the target is reached, followed by the insertion of radiation sources into the catheter. However, manually advancing an initially straight stylet into the tumor with millimeter spatial accuracy has been a long-standing challenge, which requires multiple insertions and retractions, due to the unforeseen stylet deflection caused by the stiff muscle tissue that is traversed. In this paper, we develop a novel tendon-actuated deflectable stylet equipped with MR active-tracking coils that may enhance brachytherapy treatment outcomes by allowing accurate stylet trajectory control. Herein we present the design concept and fabrication method, followed by the kinematic and mechanics models of the deflectable stylet. The hardware and theoretical models are extensively validated via benchtop and MRI-guided characterization. At insertion depths of 60 mm, benchtop phantom targeting tests provided a targeting error of 1. 23 ± 0. 47 mm, and porcine tissue targeting tests provided a targeting error of 1. 65 ± 0. 64 mm, after only a single insertion. MR-guided experiments indicate that the stylet can be safely and accurately located within the MRI environment.

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Acoustic radiation characteristics of piezoelectric shells with internal and external axial stepped-thickness configurations

Using stepped-thickness variations, this work aims at amplifying the strength of the focused acoustic field generated inside a hollow piezoelectric cylindrical tube transducer without increasing the driving power. This requires a full understanding of the vibration and acoustic radiation characteristics of various configurations of piezoelectric tube transducers with internal and external axial stepped-thickness variations. A uniform-thickness cylindrical shell is machined at specific regions to acquire a stepped-thickness cylindrical shell with thin-walled regions. The design procedure includes determining the location and number of these thin regions. ANSYS software is used to determine the frequencies and mode shapes of various configurations of these shells. However, stress concentration, as an important design consideration, is also scrutinized at the step regions to avoid exceeding the material fatigue limit. An optimum design configuration for the stepped-thickness transducer is identified. Stronger acoustic fields are obtained using geometrical variations without any increase in the driving power. The simulations are validated experimentally with reasonable agreement.

Numerical, theoretical, and experimental studies on the energy absorption of the thin-walled structures with bio-inspired constituent element

Nowadays, more bio-inspired structures were proposed and adapted in structural designs to improve their energy absorbing performance. In this paper, a bio-inspired constituent element (BCE) consisting of a hollow cylindrical tube with four panels was studied. Quasi-static tests were conducted to evaluate its energy-absorbing performance using specimens with a thin-walled square tube. A FE model was developed and validated in favorable agreement with the experimental data. Using the FE model, a parametric study of the energy absorbing capability and deformed pattern of the BCE was conducted. The specific energy absorption (SEA) of the BCE is higher than that of traditional angle elements and significantly affected by the wall thickness, radius of cylindrical tube and number of intersecting panels. Finally, analytical (or theoretical) formulae for estimating the mean crushing force of the BCE was derived and correlated favorably with the experimental data.

Estimation of the Time-Varying High-Intensity Heat Flux for a Two-Layer Hollow Cylinder

Gun barrels are subjected to time-varying high-intensity heat flux under multiple firing, which may damage the material and limit the overall performance of the gun. In order to monitor the thermal state of a gun barrel, an inverse method coupling the finite difference method with the sequential function specification method was developed to estimate the unknown time-varying heat flux imposed on the inner wall of a gun barrel. A two-layer hollow cylindrical tube was assumed with the convection heat transfer boundary condition on the outer wall of the tube. A direct heat transfer model was developed, and was used to estimate the temporal distribution of boundary heat flux in approximately real time based on the measured transient temperature at some positions on the outer wall of the gun barrel. Numerical tests were performed to verify the effectiveness and reliability of this method by investigating the influence of temperature measurement noises and future time step selection. The results show that the proposed method has high precision and efficiency in extracting the time-varying heat flux under one-shot and three-shot firing conditions. When there is a measurement noise, this method has good anti-illness characteristics and can achieve better results by appropriately selecting the value of a future time step.

Effects of wall thickness and material property on inverse heat conduction analysis of a hollow cylindrical tube

In this study, we examined the effects of a hollow cylindrical tube’s thickness and material properties on estimated time delay and waveform distortion in a one-dimensional inverse heat transfer analysis model using the thermal resistance method and an input estimation algorithm. Results indicated a persistent time delay for various heat flux amounts applied to different tube thicknesses. As the tube thickness increased, the numerically determined temperature data also experienced a time delay, which affected the inverse heat transfer response curve. Results also indicated that the transient heat flux waveform estimated for different material properties showed higher levels of distortion for materials having relatively low thermal conductivity. These materials also exhibited greater time delays. To address these issues, we applied a Fourier number (a dimensionless number representing the tube’s thickness and material properties) and proposed an equation to calculate sharpness, which can subsequently be used to predict probable time delays and heat flux waveform distortion. In conclusion, a correction is required when a low Fourier number is used in inverse heat transfer analysis.

Inverse heat conduction modeling to predict heat flux in a hollow cylindrical tube having irregular cross-sections

This study presents the development process of a three-dimensional analysis model for conducting inverse heat transfer analysis of gun barrels with varying cross-sections. In addition, it predicts heat flux in real barrels by using temperature measurements from gun firing experiments. Type-A and type-B guns are used for the experiments. Temperature is measured by independent firings of 1, 5, 10, 20, and 30 rounds for a type-A gun and by consecutive firings of 1, 5, and 7 rounds for a type-B gun. The surface temperature measurements of the gun barrels thus obtained are utilized to predict heat flux, and the effect of firing is examined by comparing the heat flux between different points on the barrels. From the heat flux results for the two types of guns, it is clear that the heat flux increases with increasing number of rounds. On the other hand, the mean value of heat flux shows that the heat flux tends to decrease toward the end of the barrel.

Three-dimensional inverse heat conduction modeling of a multi-layered hollow cylindrical tube using input estimation algorithm and thermal resistance network

High-temperature gas flow can cause melt, crack, erosion, and wear of tubes. In order to reduce these side effects, the inner wall of a hollow cylindrical tube is generally coated with a resistive material, for example, a steel pipe coated with a chrome layer. In addition, it is important to know heat flux applied to the tube wall and temperature distribution in the tube wall for appropriate design of the hollow cylindrical tube. In this study, three-dimensional inverse heat conduction modeling of a multi-layered hollow cylindrical tube was conducted. The thermal resistance network (TRN) scheme was employed to solve the heat conduction in the tube. The temperature distribution in the tube was estimated from a measured temperature on the outer wall of the tube by Kalman filter. At the same time, unknown heat flux on the inner wall of the tube was calculated by the recursive least squares algorithm.

Cavity Ring-Down Absorption of O2 in Air as a Temperature Sensor for an Open and a Cryogenic Optical Cavity.

The A-band of oxygen has been measured at low resolution at temperatures between 90 K and 373 K using the phase shift cavity ring down (PS-CRD) technique. For temperatures between 90 K and 295 K, the PS-CRD technique presented here involves an optical cavity attached to a cryostat. The static cell and mirrors of the optical cavity are all inside a vacuum chamber at the same temperature of the cryostat. The temperature of the cell can be changed between 77 K and 295 K. For temperatures above 295 K, a hollow glass cylindrical tube without windows has been inserted inside an optical cavity to measure the temperature of air flowing through the tube. The cavity consists of two highly reflective mirrors which are mounted parallel to each other and separated by a distance of 93 cm. In this experiment, air is passed through a heated tube. The temperature of the air flowing through the tube is determined by measuring the intensity of the oxygen absorption as a function of the wavenumber. The A-band of oxygen is measured between 298 K and 373 K, with several air flow rates. To obtain the temperature, the energy of the lower rotational state for seven selected rotational transitions is linearly fitted to a logarithmic function that contains the relative intensity of the rotational transition, the initial and final rotational quantum numbers, and the energy of the transition. Accuracy of the temperature measurement is determined by comparing the calculated temperature from the spectra with the temperature obtained from a calibrated thermocouple inserted at the center of the tube. This flowing air temperature sensor will be used to measure the temperatures of cooling air at the input (cold air) and output (hot air) after cooling the blades of a laboratory gas turbine. The results could contribute to improvements in turbine blade cooling design.

Prediction of time-varying heat flux along a hollow cylindrical tube wall using recursive input estimation algorithm and thermal resistance network method

In this study, a model using the thermal resistance network method and the recursive input estimation algorithm was developed to analyze two-dimensional inverse heat conduction problems. The recursive input estimation algorithm consisted of the Kalman filter and the real-time least squares. A two-layered hollow cylindrical tube was assumed with the convection heat transfer boundary condition at the outer wall of the tube. Using the model developed in this study, an unknown time-varying heat flux at the inner wall of the tube was predicted from the known temperatures at some positions on the outer wall of the tube in the longitudinal direction. In the process of predicting the unknown heat flux, the temperature distribution in the two-layered hollow cylindrical tube wall was also obtained. The present model was able to accurately predict the unknown time-varying heat flux profiles of square waves or sinusoidal-like waves with and without spatial variations in the longitudinal direction.

Inverse heat transfer analysis of multi-layered tube using thermal resistance network and Kalman filter

In this study, a hollow cylindrical tube with a coating layer on its inner wall was considered. The thermal resistance network method was employed to solve the heat conduction in the tube. Unknown heat flux on the inner wall of the tube was estimated from measured temperature on the outer wall of the tube by the recursive input estimation algorithm consisting of the Kalman filter and real-time least squares. Assuming various operating conditions, the performance of the model developed in this study was evaluated.

Wave tailoring by precompression in confined granular systems.

We present a granular system whose response under an impact load can be varied from rapidly decaying to almost constant amplitude waves by an external regulator. The system consists of a granular chain of larger spheres surrounded by small spheres, confined in a hollow cylindrical tube and supporting wave propagation along the axis of the cylinder. We demonstrate using numerical simulations that the response can be controlled by applying radial precompression. These observations are then complemented by an asymptotic analysis, which shows that the decay in the leading wave is due to energy leakage to the oscillating small beads in the tail of the wave. This system has potential applications in systems requiring tuning of elastic waves.

A new formulation to study in-plane vibration of curved carbon nanotubes conveying viscous fluid

Shortly after the discovery of carbon nanotubes (CNTs), the existence of differently shaped CNTs other than straight ones was predicted theoretically. Recently photomicrographic images show that CNTs are not actually straight but have significant curvature. This aspect was mostly neglected in previous studies on CNTs’ dynamic behavior. In this paper a new formulation governing the in-plane motion of curved CNTs conveying viscous fluid is derived to study their in-plane free vibration. In this formulation the fluid is considered to be viscous and the size effects of nanotubes are also taken into consideration through nonlocal elasticity theory. In this study CNT is modeled as a hollow cylindrical tube and the moving fluid inside is modeled as a plug flow characterized by its mass density, viscosity, and mean velocity. The new formulation is used to study the vibration and instability characteristics of curved and wavy carbon nanotubes. Using finite element analysis it is shown that the nonlocal parameter, the viscosity of fluid, and also the curvature have considerable effects on the natural frequency and critical flow velocity of carbon nanotubes. Also the effect of boundary conditions on natural frequency and critical flow velocity is studied.

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Introduction The fabrication methods and functionalization of lipid tubes are described. The fabrication methods of lipid tubes were classified into three categories, i.e. self-assembly of lipid molecules, microfluidic way to form tubes and stretching of giant v esicles using an electric field. The functionalization of lipid tubes was summarized as metallization and deposition of inor ganic silica onto tube surface, encapsulation of nanoparticles into hollow cylindrical tube of tubular microstructures, and embedding nanoparticles into the wall of lipid tubes to form functional nanocomposites or nanostructures. The applications of these nano- and microstructures are also given. This review gives a brief overview of the interesting field of lipid tubes. Conclusion The fabrication of tubular microstructures demonstrated the precise self-assembly property of lipid molecules. To explore a new universal fabrication method for lipid tubes is still a direction of this field. Templating technology using lipid tubular microstructures is a promising route to make diverse nanostructures. Duo to the high biocompatibility of lipid tubes, they can be designed as drug carriers to encapsulate hydrophilic molecules inside the tube or hydrophobic molecules within the lipid bilay er for drug delivery in biomedical research.

Macroscopic effective mechanical properties of porous dry concrete

Abstract The pores and voids within concrete have a great influence on the macroscopic elastic modulus, strength and other mechanical properties of concrete. The present study determines the macroscopic mechanical properties of porous dry concrete composed of hollow void inclusions embedded in a concrete matrix. Based on a three-phase sphere model, the effective bulk modulus of a concrete composite with a hollow sphere in concrete matrix is obtained. The investigation on the influence of porosity on the effective shear modulus of porous dry concrete is carried out by using a hollow cylindrical tube model. Based on the assumption that the material is isotropic, homogeneous and elastic, the effective Young's modulus and Poisson's ratio of porous concrete composites are derived. A comparison between the elastic modulus and Poisson's ratio derived from the present model and those from open literature indicates a good agreement. Furthermore, on the basis of the developed simplified analytical model, the quantitative effect of porosity on the macroscopic effective tensile and shear strengths of porous concrete in dry state are studied. Besides, their corresponding effective peak strains when porous dry concrete reaches its macroscopic effective tensile/shear strengths are also investigated and discussed. Also a comparison between the available tensile strength and two classical solutions is made to verify the rationality and accuracy of the present approach. The consistent results indicate that the proposed approach can predict the effective mechanical properties of porous dry concrete well, and the formulas are simple and convenient to use.

Pre-Strained Piezoelectric PVDF Nanofiber Array Fabricated by Near-Field Electrospining on Cylindrical Process for Flexible Energy Conversion

In this study, near-field electrospining on hollow cylindrical (NFES) process was used to fabricate permanent piezoelectricity of polyvinylidene fluoride (PVDF) piezoelectric nanofibers. With in situ electric poling, mechanical stretching and heating during NFES process, the pre-strained piezoelectric PVDF nanofibers with high stretchability and energy conversion efficiency can be applied at low-frequency ambient vibration to convert mechanical energies into electrical signals. By adjusting rotating velocity of the hollow cylindrical glass tube on X-Y stage, electric field, baking temperature and carbon nanotube (CNT) concentration in PVDF solution, the crystalline of β phase, polarization intensity and morphology of piezoelectric fiber can be controlled. XRD (X-ray diffraction) observation of PVDF fibers was characterized. With electric field 0.5×107 V/m (needle-to-tube distance 2 mm and DC voltage 5 kV), rotating velocity 400 r.p.m, baking temperature 80 °C and 0.03 wt% CNT in NFES process, it reveals a high diffraction peak at 2θ=20.8° of piezoelectric crystal β-phase structure. Then the array nanofibers were transferred onto a parallel copper electrode by using flexible insulation epoxy/PI film to provide packaging protection. When the sensor was tested under 5 Hz vibration frequency, the maximum induced voltage was 29.4 mVp-p.

Development of surgical protocol for implantation of tracheal prostheses in sheep

This article documents experiments performed in ewes to design an artificial larynx. The artificial larynx is composed of a hollow, porous tube that elongates the trachea and is capped with a valve that acts as a laryngeal sphincter. Through an industrial collaboration, our team developed a porous biomaterial that can be colonized by cervical tissues. This biomaterial has been used in animals to replace part of the trachea, but it is meant to eventually substitute for laryngeal cartilage. The tracheal prosthesis is a hollow cylindrical tube composed of titanium microbeads. We performed a study in large animals to establish an optimal surgical protocol for tracheal replacement in humans. The study included 11 sheep (n = 11) and compared 5 methods of implantation. We successfully established an optimal three-step surgical protocol to make the porous-titanium tracheal prosthesis functional: (1) large lumen endoprosthetics, (2) colonization by the peripheral tissues, and (3) endoprosthetic epithelialization. This study is the first step in developing an artificial larynx because it successfully identifies a biomaterial capable of extending the trachea to allow it to open at the junction of the upper aerodigestive tracts.

Dynamic Characterization of Candle Flame

The present work focuses on studying the flickering of a candle placed in a hollow cylindrical glass tube. Variations in flame area and intensity have been studied as the oscillating parameters of the flame with a camera and a Photomultiplier tube (PMT), and results have been found to be indicative of the presence of some well defined peaks in the amplitude spectrum of the flame intensity. Tests have been carried out with a range of candle diameters for the same glass tube giving similar results. Fluctuations in fractal dimension of the flame structure have also been studied in the course of the work. The time series data generated by processing camera images and also the PMT voltage output has been studied for existence of periodicity in the signal recorded. The correlation dimension has been determined for a number of experiments to characterize the dynamics of the signal.

Numerical Study of a Novel Built-In Energy-Absorbing Component for Adaptive Steering Columns

The steering-wheel—steering-column assemblies fitted in automobiles must have a high energy absorption performance in order to minimize occupant chest injuries in the event of a collision. This paper proposes a novel built-in energy-absorbing (EA) component which causes the impact load transmitted to the occupant to vary in accordance with the crash severity and the occupant mass. A finite element (FE) model of the steering-column system is constructed on the basis of realistic product computer-aided design data, and a series of LS-DYNA simulations are performed to examine the dynamic responses of the steering wheel and steering column in body block impact tests performed using body blocks of different weights. The validity of the FE model is confirmed by comparing the numerical results for the torso force profile over the duration of the impact with the experimental results obtained in two standard body block tests. The validated model is then used to examine the energy absorption performance of the proposed EA device consisting of a hollow cylindrical tube patterned with an array of circular openings. The simulations focus specifically on the effects of the total hole-opening area, the cylinder thickness, and the cylinder material on the torso force profile over the duration of the impact. It is shown that, given an appropriate specification of the design parameters, the proposed EA device satisfies the peak load requirement specified in the FMVSS 203 standard and absorbs 163 J and 235 J of the impact kinetic energy for body block weights of 24 kgf and 34 kgf respectively.