Double-walled Structure Research Articles

Research on Sound Insulation Performance of Poroelastic Material in Complex Structure

A finite element model of the double-wall acoustic insulation structure with a air layer and an acoustic absorbent layer made of the poroelastic materials is set up, the responses of this acoustic-vibration system are calculated by using of the direct finite element method when having a diffuse incident acoustic field acting on the incident surface, the radiant acoustic power from the another surface are achieved, then the Transmission Loss(TL) are formulated using the incident acoustic power and the radiant acoustic power. The effects of the thicknesses, elastic modulus, flow resistivity and viscous lengths of the poroelastic materials on TL are analyzed. The results show that the thicknesses and elastic modulus have a significant effects on TL, TL are enhanced with the thicknesses increasing of the poroelastic materials layers, a 4.9dB addition of TL is achieved when thickness is added from 2cm to 3cm; TL are enhanced with the reduction of the elastic modulus in considered frequency range, and TL are reduced with the declining of viscous lengths and with the addition of the flow resistivity when the frequencies are higher than 600Hz.

Cavitation damage in double-walled mercury target vessel

A liquid mercury target is operated as part of a spallation neutron source at the Japan Proton Accelerator Research Complex (J-PARC). The mercury target vessel is made of 316L stainless steel, (3 mm thick) and its beam window is damaged by cavitation due to pressure waves in mercury. To mitigate the pressure waves and the cavitation damage, a double-walled structure with a narrow channel of 2 mm was added to the beam window along with gas microbubbles injection technology. After operation of up to 670 MWh for 1670 h, the beam window of the used target vessel was cut out using an annular cutter to investigate the effect of the double-walled structure on mitigating cavitation damage. Band-like damage distribution due to cavitation was observed on the outer wall that faced the narrow channel, where the maximum pit depth was estimated to be 25 μm. Furthermore, to clarify the mechanisms possibly contributing to the band-like damage distribution, numerical simulations were conducted in terms of flow velocity, gap width, and pressure waves in the narrow channel. The results show that the distribution of accumulated saturation time of negative pressure period obtained from FEM simulation correlated well with the experimentally observed band-like damage distribution.

APPLYING BIM TO BUILT HERITAGE WITH COMPLEX SHAPES: THE ICE HOUSE OF FILARETE’S OSPEDALE MAGGIORE IN MILAN, ITALY

Abstract. This paper presents the development of a BIM model for a stratified historic structure characterized by a complex geometry: Filarete’s Ospedale Maggiore ice house, one of the few remaining historic ice houses in Milan (Fig. 1). Filarete, a well-known Renaissance architect and theorist, planned the hospital in the 15th century, but the ice house was built two centuries later with a double-storey irregular octagonal brick structure, half under and half above ground, that enclosed another circular structure called the ice room. The purpose of the double-walled structure was to store ice in the middle and store and preserve perishable food and medicine at the outer side of the ice room. During World War II, major portions of the hospital and the above-ground section of the ice house was bombed and heavily damaged. Later, in 1962, the hospital was restored and rehabilitated into a university, with the plan to conceal the ice house’s remaining structure in the courtyard, which ultimately was excavated and incorporated into a new library for the university. A team of engineers, architects, and students from Politecnico di Milano and Carleton University conducted two heritage recording surveys in 2015 and 2016 to fully document the existing condition of the ice house, resulting in an inclusive laser scanner and photogrammetric point cloud dataset. The point cloud data was consolidated and imported into two leading parametric modelling software, Autodesk Revit© and Graphisoft ArchiCAD©, with the goal to develop two BIMs in parallel in order to study and compare the software BIM workflow, parametric capabilities, attributes to capture the complex geometry with high accuracy, and the duration for parametric modelling. The comparison study of the two software revealed their workflow limitations, leading to integration of the BIM generative process with other pure modelling software such as Rhinoceros©. The integrative BIM process led to the production of a comprehensive BIM model that documented related historic data and the existing physical state of the ice house, to be used as a baseline for preventive maintenance, monitoring, and future conservation projects.

Three-Dimensional Printed Insulation For Dynamic Thermoelectric Harvesters With Encapsulated Phase Change Materials

Energy harvesting devices have demonstrated their ability to provide power autonomy to wireless sensor networks. However, the adoption of such powering solutions by the industry is challenging due to their reliance on very specific environmental conditions such as vibration at a specific frequency, direct sunlight, or a local temperature difference. Dynamic thermoelectric harvesting has been shown to expand the applicability of thermoelectric generators by creating a local spatial temperature gradient from a temporal temperature fluctuation. Here, a simple method for prototyping or short-run production of such devices is introduced. It is based on the design and 3-D printing of an insulating container, insertion of a phase change material in encapsulated form, and use of commercial thermoelectric generators. The simplicity of this dry assembly method is demonstrated. Two prototype devices with double-wall insulation structures are fabricated, using a stainless-steel and a plastic phase change material encapsulation and a commercial TEG. Performance tests under a temperature cycle between 25C show energy output of 43.6 and 32.1J from total device masses of 69 and 50g, respectively. Tests under multiple temperature cycles demonstrate the reliability and performance repeatability of such devices. The proposed method addresses the complication of requiring a wet stage during the final assembly of dynamic thermoelectric harvesters. It allows design and customization to particular size, energy, and insulation geometry requirements. This is important because it makes dynamic harvesting prototyping widely available and easy to reproduce, test, and integrate into systems with various energy requirements and size restrictions.

Synthesis and photoeletrochemical performance of AuAg@CdS double-walled nanotubes

Uniform CdS coated AuAg alloyed double-walled nanotubes were successfully fabricated by solvothermal process using Ag nanowires as the template. UV–vis-NIR extinction spectra revealed that the obtained double-walled nanotubes can present an enhanced light absorption ability compared with both pure AuAg alloyed nanotubes and CdS nanowires. Photocurrent and electrochemical impedance spectroscopy measurements indicated that such double-walled structure could significantly extend the lifetime of photo-generated carriers and increase the light-harvesting efficiency of CdS, due to the low charge transfer resistance and a high carrier transfer rate of the double-walled structure. The growth mechanism of such kind of nanotubes was also proposed.

A mobility based vibroacoustic energy transmission simulation into an enclosure through a double-wall panel.

Double-wall panels are known for their superior sound insulation properties over single wall panels as a sound barrier. The sound transmission phenomenon through a double-wall structure is a complex process involving vibroacoustic interaction between structural panels, the air-cushion in between, and the secondary acoustic domain. It is in this context a versatile and a fully coupled technique based on the finite-element-boundary element model is developed that enables estimation of sound transfer through a double-wall panel into an adjacent enclosure while satisfying the displacement compatibility across the interface. The contribution of individual components in the transmitted energy is identified through numerical simulations.

Evolution of TiO2 Nanotubular Morphology Obtained in Ethylene Glycol/Glycerol Mixture and its Photoelectrochemical Performance

The evolution of TiO2 nanotubular morphology, synthesized in a mixture of fluorinated ethylene glycol and glycerol electrolyte, was studied as a function of the anodization time. The samples were characterized by FEG-SEM, XRD, XPS, UV-Vis and EIS. The formation of single-or double-walled TiO2 nanotube structure can be efficiently controlled by the anodization time. For anodization times less than 30 minutes, a compact oxide layer is formed, followed by double-walled nanotube formation up to 120 minutes and single-walled nanotubes up to 240 minutes. XPS analyses show that the samples obtained with short anodization time have a high carbon content and oxygenated surface species compared to the longer-time anodized sample; however, binding energy peaks for Ti 2p remained invariant. The performances of TiO2 nanotubular photoelectrodes were evaluated in photoelectrochemical water splitting where TiO2 nanotubes anodized for 120 minutes presented the best performance that was related to their optimal morphology and charge transportation.

Role of Hydrophobic/Aromatic Residues on the Stability of Double-Wall β-Sheet Structures Formed by a Triblock Peptide.

Bioinspired self-assembling peptides serve as powerful building blocks in the manufacturing of nanomaterials with tailored features. Because of their ease of synthesis, biocompatibility, and tunable activity, this emerging branch of biomolecules has become very popular. The triblock peptide architecture designed by the Hartgerink group is a versatile system that allows control over its assembly and has been shown to demonstrate tunable bioactivity. Three main forces, Coulomb repulsion, hydrogen bonding and hydrophobicity act together to guide the triblock peptides' assembly into one-dimensional objects and hydrogels. It was shown previously that both the nanofiber morphology (e.g., intersheet spacing, formation of antiparallel/parallel β-sheets) and hydrogel rheology strictly depend on the choice of the core residue where the triblock peptide fibers with aromatic cores in general form shorter fibers and yield poor hydrogels with respect to the ones with aliphatic cores. However, an elaborate understanding of the molecular reasons behind these changes remained unclear. In this study, by using carefully designed computer based free energy calculations, we analyzed the influence of the core residue on the formation of double-wall fibers and single-wall β-sheets. Our results demonstrate that the aromatic substitution impairs the fiber cores and this impairment is mainly associated with a reduced hydrophobic character of the aromatic side chains. Such weakening is most obvious in tryptophan containing peptides where the fiber core absorbs a significant amount of water. We also show that the ability of tyrosine to form side chain hydrogen bonds plays an indispensable role in the fiber stability. As opposed to the impairment of the fiber cores, single-wall β-sheets with aromatic faces become more stable compared to the ones with aliphatic faces suggesting that the choice of the core residue can also affect the underlying assembly mechanism. We also provide an in-depth comparison of competing structures (zero-dimensional aggregates, short and long fibers) in the triblock peptides' assembly and show that by adjusting the length of the terminal blocks, the fiber growth can be turned on or off while keeping the nanofiber morphology intact.

Role of Outgassing of ITER Vacuum Vessel In-Wall Shielding Materials in Leak Detection of ITER Vacuum Vessel

ITER Vacuum Vessel is a torus-shaped, double wall structure. The space between the double walls of the VV is filled with In-Wall Shielding Blocks (IWS) and Water. The main purpose of IWS is to provide neutron shielding during ITER plasma operation and to reduce ripple of Toroidal Magnetic Field (TF). Although In-Wall Shield Blocks (IWS) will be submerged in water in between the walls of the ITER Vacuum Vessel (VV), Outgassing Rate (OGR) of IWS materials plays a significant role in leak detection of Vacuum Vessel of ITER. Thermal Outgassing Rate of a material critically depends on the Surface Roughness of material. During leak detection process using RGA equipped Leak detector and tracer gas Helium, there will be a spill over of mass 3 and mass 2 to mass 4 which creates a background reading. Helium background will have contribution of Hydrogen too. So it is necessary to ensure the low OGR of Hydrogen. To achieve an effective leak test it is required to obtain a background below 1 × 10-8 mbar 1 s-1 and hence the maximum Outgassing rate of IWS Materials should comply with the maximum Outgassing rate required for hydrogen i.e. 1 x 10-10 mbar 1 s-1 cm-2 at room temperature. As IWS Materials are special materials developed for ITER project, it is necessary to ensure the compliance of Outgassing rate with the requirement. There is a possibility of diffusing the gasses in material at the time of production. So, to validate the production process of materials as well as manufacturing of final product from this material, three coupons of each IWS material have been manufactured with the same technique which is being used in manufacturing of IWS blocks. Manufacturing records of these coupons have been approved by ITER-IO (International Organization). Outgassing rates of these coupons have been measured at room temperature and found in acceptable limit to obtain the required Helium Background. On the basis of these measurements, test reports have been generated and got approved by IO. This paper will describe the preparation, characteristics and cleaning procedure of samples, description of the system, Outgassing rate Measurement of these samples to ensure the accurate leak detection.

Raman imaging of millimeter-long carbon nanotubes grown by a gas flow method

Growing long carbon nanotubes (CNTs) is an important prerequisite for practical applications of CNTs. Although gas-flow-guided chemical vapor deposition can be used to produce millimeter-long CNTs, little is known regarding the associated growth mechanism. In the present work, Raman imaging was employed to characterize individual CNTs grown by the gas flow method, and Raman images of a CNT over 1.6 mm long were obtained. Two radial breathing modes were observed and the associated Raman images exhibited exactly identical distributions, indicating that the long CNT most likely had a double-walled structure, in which the CNT diameter was uniform along the whole length.

Numerical analysis of damped vibration responses for double-wall structures which have acoustic black hole effects using FEM and MSKE method(influence of boundary condition)

Numerical analysis of damped vibration responses for double-wall structures which have acoustic black hole effects using FEM and MSKE method(influence of boundary condition)

Sound Transmission Through a Double-Wall Structure Coupled with Two Trapezoidal Acoustic Cavities

This paper aims at investigating the sound transmission mechanism of a flexibly-linked finite length double-wall structure. The problem stems from the modeling of sound transmission through corrugated core sandwich panels for predicting its transmission loss. The spatial segmentation of the acoustic gap and fully structure-acoustic coupling effect between the flexural vibration of the inclined mechanical link and the two adjacent trapezoidal acoustic cavities are considered. The theoretical model of the considered vibro-acoustic system is developed by using the modal superposition method in conjunction with envelope rectangular technique. Based on the developed theoretical model, the general vibro-acoustics characteristics of the system is presented. Particularly by using the [Formula: see text] mode of the acoustic cavity and the first structural modal frequency, the ratio between the aerostatic stiffness and the structural stiffness is formulated, and a criterion is proposed to determine whether the sound insulation performance of the vibro-acoustic system is controlled mainly by the structure or the acoustic cavity. Numerical investigations reveal that with different stiffness ratio, the acoustic cavity affects the sound transmission through both the added stiffness and added mass following different mechanisms. Besides, the influence of the inclined angle of the connecting beam on sound insulation performance of the double-wall structure is also studied. The obtained results are believed to be helpful in the optimal design of corrugated core sandwich panels for sound insulation.

Experimental Study on Embankment Reinforcement by Steel Sheet Pile Structure Against Tsunami Overflow

This study proposes a new embankment reinforcement using steel sheet piles against tsunami overflow, which has been known as the main cause of the failures of the embankments by the 2011 Tohoku Earthquake Tsunami. Effectiveness of the proposed technique was discussed through a hydraulic experiment. A model of embankment was set in a horizontal open channel, and one or two steel plates are installed into the embankment from the top as vertical walls inside. Temporal variations of the shapes of the embankment and the sheet pile structures were obtained from video images. In most of the cases, the sheet pile structures started to rotate after the erosion of the landward slope of the embankment. However the rotation stopped at about 30° and 10° from the initial location with the single- and double-wall cases. Height of the embankment after overflow was less than 20% with no reinforcement, while more than 70% and 95% of the height were kept with the single- and double-wall structures, respectively. The performance of the embankment with the reinforcement was also discussed in terms of tsunami energy reduction with an additional fixed-bed experiment.

Preparation and characterization of a novel double-walled Na2(TiO)SiO4 nanotube by hydrothermal process with CTAB as an assistant

A double-walled Na2(TiO)SiO4 nanotube was prepared by an effective hydrothermal process with cetyltrimethyl ammonium bromide (CTAB) as an assistant. The precursor SiO2-TiO2 composite powder with diverse Si/Ti molar ratios was prepared by co-precipitation method using silica sol and titanyl sulfate as raw materials. Then it was added into the NaOH aqueous solution with CTAB for hydrothermal reaction. The Na2(TiO)SiO4 nanotubes were characterized by X-ray diffraction (XRD), thermogravimetric and differential scanning calorimeter (TG-DSC), transmission electron microscope (TEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance (29Si-NMR), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy and N2 adsorption-desorption. The results showed that the Na2(TiO)SiO4 nanotubes are of large specific surface area, double-wall and Q0 structure. The length of Na2(TiO)SiO4 nanotubes can be controlled by adjusting the Si/Ti molar ratios from 100 nm to several hundred nanometers. A possible formation mechanism of the novel double-walled Na2(TiO)SiO4 nanotubes was also proposed.

Self-organized double-wall oxide nanotube layers on glass-forming Ti-Zr-Si(-Nb) alloys

In this work, we report for the first time on the use of melt spun glass-forming alloys - Ti75Zr10Si15 (TZS) and Ti60Zr10Si15Nb15 (TZSN) - as substrates for the growth of anodic oxide nanotube layers. Upon their anodization in ethylene glycol based electrolytes, highly ordered nanotube layers were achieved. In comparison to TiO2 nanotube layers grown on Ti foils, under the same conditions for reference, smaller diameter nanotubes (~116nm for TZS and ~90nm for TZSN) and shorter nanotubes (~11.5μm and ~6.5μm for TZS and TZSN, respectively) were obtained for both amorphous alloys. Furthermore, TEM and STEM studies, coupled with EDX analysis, revealed a double-wall structure of the as-grown amorphous oxide nanotubes with Ti species being enriched in the inner wall, and Si species in the outer wall, whereby Zr and Nb species were homogeneously distributed.

能動騒音制御および能動振動制御による二重壁放射音の抑制

This paper presents a new active control method of sound radiated from a double-walled structure. The purpose of this study is to control of sound radiation power level using both of active noise control and active vibration control. First, modal coupling method is introduced which is required to model a vibro-acoustic coupling system. Then, optimal control laws of active noise control and active vibration control for minimizing the sound radiation power are derived in a vector form. Next, some numerical simulations are carried out to demonstrate the validity of the proposed method. As a result of the analysis, reduction of the sound power level is succeeded by feedforward control. Some numerical results show that active noise control is more effective than active vibration control for minimizing the sound power level. In addition, it is shown that by combination of the both control methods, improvement of a control performance is achieved. Furthermore, it is found that control effect rely on the relationship between placement of control sound sources and the disturbance location, while placement of control vibration source does not have significant impact on the control performance.

A new bi-tubular conical–circular structure for improving crushing behavior under axial and oblique impacts

In this study single and double wall structures for crashworthiness are investigated to introduce a novel system with better energy absorption and crushing characteristics under both axial and oblique loading. The new developed double wall structure is constructed from inner conical and outer circular tubes, incorporated with and without foam filler. Foam filled bi-tubular structure subject to direct axial and oblique impact loadings are simulated using nonlinear finite element analysis software package LS-DYNA. Numerical simulations obtained via non-linear explicit dynamic FEM are firstly validated using theoretical and experimental solutions. Next, effectiveness of the new developed bi-tubular structure has been shown by comparing with similar common thin-walled structures. Different types of structures namely bi-tubular empty and foam filled new design, empty and filled frusta as well as empty and foam filled circular tubes were considered in order to make a more insightful of capabilities of the proposed structure. A parametric study including the effect of geometrical and material properties of the structure on the crashworthiness has been carried out. Results show the possibility of amending the peak crushing load along with keeping other energy absorption characteristics unchanged or even improved. Also an improvement in absorbed energy under oblique loading by using the new developed structure is observed.

Welding technology on sector assembly of the JT-60SA vacuum vessel

Manufacturing of JT-60SA Vacuum Vessel (VV) is under the onsite sector assembly, where ten VV sectors are to be welded together into a torus. The vessel is 6.6m height and 5m major radius and a double wall structure with the thickness of 18mm and locally 30mm, and total dimensional tolerance is designed to avoid any interference due to operational displacements. In this paper, two issues are focused: the onsite sector assembly concept and sector welding technology. The assembly concept is a contrivance to fulfil high precision as a large torus VV and efficient procedure, and obtained with combination of the direct butt joint and splice plate joint. The welding technology is a method to realize the VV, and investigated on acceptable error sizes with the test pieces for the onsite manipulator welding. Correction method of sector edge is also confirmed by the mock-up. Moreover, application to the onsite sector assembly is discussed. The onsite assembly has been started by this concept with its welding technology.

In-situ structural integrity evaluation for high-power pulsed spallation neutron source – Effects of cavitation damage on structural vibration

A double-wall structure mercury target will be installed at the high-power pulsed spallation neutron source in the Japan Proton Accelerator Research Complex (J-PARC). Cavitation damage on the inner wall is an important factor governing the lifetime of the target-vessel. To monitor the structural integrity of the target vessel, displacement velocity at a point on the outer surface of the target vessel is measured using a laser Doppler vibrometer (LDV). The measured signals can be used for evaluating the damage inside the target vessel because of cyclic loading and cavitation bubble collapse caused by pulsed-beam induced pressure waves. The wavelet differential analysis (WDA) was applied to reveal the effects of the damage on vibrational cycling. To reduce the effects of noise superimposed on the vibration signals on the WDA results, analysis of variance (ANOVA) and analysis of covariance (ANCOVA), statistical methods were applied. Results from laboratory experiments, numerical simulation results with random noise added, and target vessel field data were analyzed by the WDA and the statistical methods. The analyses demonstrated that the established in-situ diagnostic technique can be used to effectively evaluate the structural response of the target vessel.

GEOMETRIC SPECIFICATION OF BEVEL WRAPPING OF DOUBLE WALLED TUBES, PREDICTION OF FAILURE FROM MATERIAL PROPERTIES

Bundy tube, is type of double-walled low-carbon steel tube manufactured by rolling a copper-coated steel strip through 720 degrees and resistance brazing the overlapped seam in a process called Bundy welding. Double wall brazed steel tubing is constructed from copper coated steel strip which is rolled twice around laterally, then furnace brazed to produce a tube of double wall structure, with a clear, scale free coppered bore, a plated external surface and a consistently uniform wall thickness. PROBLEM BY BUNDY TUBEING INDIA LIMITED Given 17 parameters namely level, pH, chemicals (KCN(Potassium cyanide), CuCN(Copper Cyanide), Rochelle Salt, carbonate) each in tank number 8 and 9 respectively with strip thickness, strip hardness, plating thickness at left, centre and right to predict the percentage of wastage in the tube production. Prediction of wastage by company: Nominal diameter(d) Wall Thickness(e), Strip thickness (f), Bevel angle (), Bevel outer angle(o), Bevel inner angle (I) , Bevel outer length (l), Circumference (cf) Data for Bundy Project (17 inputs & 1 output) Leval T 8 & 9 PH T 8 & 9 KCN T 8