Shell Plate Research Articles

Two Dimensional Static Mechanical Analysis of Laminated Composite Tube Using ABCDE Matrix with No Correction Factor

Accurate modeling and prediction of materials properties is of utmost importance to design engineers. In this study, newly developed two-dimensional laminate constitutive equations (LCE) were derived directly from an existing shell model without using a classical correction factor. The resulted LCEs were subsequently used for the first time to analyze a laminated composite tube (LCT) subjected to in plane-loading. This led to additional composite-shell stiffness coefficients which are not currently available in some LCEs. The strains and stresses distribution fields were computed via Matlab. The accuracy and robustness of our analytical method were proven by opposing the as-obtained results of thick and thin LCTs with that of existing theories which use a correction factor. An excellent convergence was observed. Whereas a lower convergence was observed in the case of a laminated shell plate. Results also showed that the thickness ratio χ (2χ=h/R ) considerably influences the mechanical behavior of the LCT. In fact when χ<0.1, the distribution of stresses and strains of the tube were the same for the two opposed theories. When χ>0.1, the distribution of stresses and strains were not the same, hence the contribution of our ABCDE matrix. The new mechanical couplings in our LCE could be well illustrated in a finite element package with visualization tools to observe some intricate deformations which are yet to be seen. Thus the outcome of this work will be of particularly interest to promote advanced scientific and structural engineering applications.

Ground Motion Intensity Measures for Seismic Vulnerability Assessment of Steel Storage Tanks With Unanchored Support Conditions

Abstract This paper aims to comprehensively evaluate the performance of a series of ground motion intensity measures (IMs) used in the seismic vulnerability assessment of steel storage tanks with unanchored support conditions. Sixteen well-known IMs are thus selected, which are classified into amplitude-, frequency-, and time-based categories. A comparative study is then performed on four different unanchored steel storage tanks subjected to a suite of 140 ground motion records that is comprised of seven different bins of records with different hazard levels. In this regard, the tanks are appropriately modeled based on a simplified approach, whose uplift and sliding nonlinear behaviors are properly implemented based on a three-dimensional nonlinear pushover analysis of the tanks. Four characteristics of the examined IMs including efficiency, practicality, proficiency, and sufficiency are evaluated based on a probabilistic seismic demand model of two critical failure modes of the tanks, i.e., plastic rotation of the shell-to-bottom connection and elephant's foot buckling of the shell plate. According to the comparative study, frequency-based IMs demonstrate their superior performance for all criteria compared with other groups; in particular, the average spectral acceleration gains the highest ranking. Finally, an appropriate range of the upper period considered in the average spectral acceleration IM is then proposed to optimize the efficiency of this IM for the examined tanks.

The protective mechanism of pyramid lattice on submarine subjected to undex

<p indent=0mm>The pyramid lattice sandwich shell is applied to the non-pressure hull of conventional submarine to reduce the damage when it is attacked by torpedo in close range. The design of pyramid lattice sandwich shell on conventional submarine is put forward. MSC.NASTRAN was used to study the anti-high hydrostatic performance of submarine hull after pyramid lattice sandwich shell was installed. The simulation results show that the improved submarine cabin structure is in a safe range under the designed water depth. Then MSC.DYTRAN was used to study the anti-explosion effect of the pyramid lattice sandwich shell as the outer protective structure of submarine. The results show that when the <sc>100 kg</sc> TNT charge explodes at <sc>3 m</sc> on the side of the submarine cabin, taking the damaged deformation as evaluation parameter, the anti-explosion performance of the submarine’s pressure hull mounted with pyramid lattice sandwich shell is 69.7% better than that of conventional submarine. The anti-explosion performance of the shell plate and upper deck was improved by 49.8% and 55.8%, respectively. Compared with solid plates, when the fluid-solid coupling parameter is greater than 10 and the ratio of core strength to peak pressure of shock wave is less than 0.15, the core layer can reduce the total incident impulse by more than 60%. The pyramid lattice sandwich shell used in submarine can not only meet the conditions of high hydrostatic pressure, but also greatly improve the anti-explosion performance of submarine hull structure, which has significant application value.

Numerical investigation of molten salt/SiO2 nano-fluid in the solar power plant cycle and examining different arrangements of shell and tube heat exchangers and plate heat exchangers in these cycles

BackgroundSolar towers use heliostat to direct a lot of sunlight into a receiver. When concentrated solar radiation is converted to heat, it can drive a steam turbine connected to a power generator, which generates electricity. The purpose of this research is to design and analysis of a solar power plant in the climatic condition of Jeddah, Saudi Arabia. MethodBoth TRANSYS and THERMO FLEX software are applied for such purpose. The intended power plant is composed of two sections of a solar cycle with molten salt as working fluid and a Rankine cycle with working fluid of water for power generation. COMSOL software is applied to simulate the preheater heat exchangers. ResultsThe results of this study indicated that the solar power plant generates the most electricity during June and July. The efficiency during these two months is 25% for molten salt nanofluid and 24% for molten salt. In addition, the use of molten salt nanofluid can improve the heat transfer in the solar receiver and produce more electricity in the power plant compared to the use of molten salt. Moreover, the use of two preheaters instead of one increases the efficiency of the cycle by up to 3%.

Modal Analysis of Complex Structures via a Sub-Structuring Approach

In this paper, the problems arising from determining the modal properties of large and complex structures are investigated. For this purpose, the free interface component mode synthesis method has been used. In the following, Singular-Value Decomposition (SVD) is applied as a powerful mathematical tool to determine the appropriate coordinates to participate in the coupling process. Also, the effective error resources including modal shear error and the continuous systems overlapping error and their solution are introduced. Initially, a discrete system has been employed to investigate the free interface component mode synthesis method. Eventually, the studied main samples in this research are beam, plate and cylindrical shell. It is worth noting that the application of this method on the cylindrical shell has not been observed in previous researches.

Natural Frequency Measurements of the Fluid-Elastic-Coupled Shell Plate Vibration in a Large-Sized Cylindrical Steel Tank by Microtremor Observations

AbstractNaturally occurring microtremor observations measured the natural frequencies of the fluid-elastic-coupled shell plate vibration (bulging) in a large flat-bottomed cylindrical steel tank with a capacity of 125,000-m3. Five peaks appear in the observed microtremor spectral ratios of the top or midheight of the shell plate to the bottom on the tank foundation. Comparing the spectral ratios to the solutions obtained by FEM eigenvalue analysis assuming a fixed base suggests that the five peaks are the bulging modes of (m, n)=(1, 1–5), where m and n denote the vertical order and the circumferential wavenumber, respectively. The measured non-soil-coupled natural frequencies from the spectral ratio agree fairly well with those obtained from FEM analysis. The measured natural frequencies of the fundamental mode (m = n = 1) also agree well with those projected by a simplified equation developed under the assumption of a fixed base, which is adopted in the seismic codes of the Japanese Fire Service Act. This equation should provide a reliable soil-coupled natural frequency of the fundamental mode for a tank situated on firm ground in which the storage-soil-coupled effects are presumed weak. Additionally, a simple method is presented to determine the non-soil-coupled natural frequency of the fundamental mode from the observed microtremor spectral ratios without referencing the FEM eigenvalue solutions. This simple method works very well for the tank examined.

DESAIN DAN PERHITUNGAN BODY KAPAL ATAU HULL STRUCTURE PEMBERSIH SAMPAH DI PANTAI

This garbage cleaning ship is a new building design that functions as a garbage cleaning beach with a size of a ship length of 12, 4m wide and 2m high. The design of this garbage cleaning vessel is a solution to help cleaning and transporting waste along the coast in general in accordance with the Karimun district government program.&#x0D; Based on the results of calculations on the construction design of the garbage cleaning vessel body, the body or hull of the garbage cleaning vessel, weighs 19,766 tons and is designed to lift ± 20 tons of wet garbage. This garbage cleaning vessel has a height of 0.401 m empty ship and is loaded with a load of 0.800 m. For the design of the thickness of the plate on the Deck Plate, Shell Plate and bottom plate from the calculation found the thickness of the plate 8 mm and for the transverse stability value of the ship the value of KM 2.86 m, KG 1 m, KB 0.2 m while the stability value extends the ship KM value 24 m, KG 1 m, KB 0.2 m.

On non-axisymmetric buckling modes of inhomogeneous circular plates

Unsymmetrical buckling of nonuniform circular plates with elastically restrained edge and subjected to normal pressure is studied in this paper. The asymmetric part of the solution is sought in terms of multiples of the harmonics of the angular coordinate. A numerical method is employed to obtain the lowest load value at which waves in the circumferential direction can appear. The effect of material heterogeneity and boundary on the buckling load is examined. For a plate with elastically restrained edge, the buckling pressure and mode number increase with a rise of spring stiffness. Increasing of the elasticity modulus to the plate edge leads to increasing of the buckling pressure, but the mode number does not change. If the translational flexibility coefficient is small, decreasing of the elasticity modulus to the shell (plate) edge leads to sufficient lowering of the buckling pressure.

EFFECT OF MECHANICAL ANCHORAGE IN HEAT TREATED BEAMS RETROFITTED WITH CFRP

Aim: Locally deformed beams and girders could be temporarily repaired by heat treatment but this practice causes the decrease in the load capacity of the member. Besides, fiber reinforced polymer strips could be used to gain a permanent retrofitting solution for the deformed elements. Method: In this study initially the behavior of heat treated IPE-80 beam strengthened by Carbon Fiber Reinforced Polymer (CFRP) strips bonded with epoxy is observed. This practice causes a significant increase in the load capacity but it is also being observed that epoxy scatters earlier, which does not allow the CFRP to resist much more load. Scaled steel IPE80 beams are selected and they are subjected to three-point bending test. Load-deflection behavior is recorded for each test and conclusions are derived by comparing the results. Conclusion: Preliminary laboratory experiments on shell plates shows that using anchorage by employing bolt has better results compare to those observed by using anchorage made by CFRP fabric only. This study suggests implementation of anchorages through bolts or CFRP fabrics along with epoxy bonding to retrofit the heat treated elements.

ANALYSIS OF ICE-INDUCTED STRUCTURE VIBRATION OF OFFSHORE WIND TURBINES BASED ON DEM-FEM COUPLED METHOD

The ice load is one of the most important factors that cannot be ignored for offshore wind turbines (OWTs) in cold regions. The ice-induced vibrations (IIVs) can bring serious fatigue and damage to the OWTs structure. In this paper, a coupling method of the discrete element method (DEM) and the finite element method (FEM) is adopted to establish the IIVs model of monopile-type OWTs. The breakage and failure process of level ice are simulated with the spherical DEM with bonding-breaking effect, and the finite element model of monopile-type OWTs is constructed by the beam element and triangular plate shell element. The DEM-FEM coupled method is adopted to simulate the interaction progress between monopile-type OWTs and level ice under different ice velocity and ice thickness conditions. The accuracy of ice load calculated by the DEM-FEM coupled method is verified by comparing with the empirical formula of IEC (International Electrotechnical Commission) and ISO (the International Organization for Standardization). By comparing the displacements and the acceleration of the top of the wind turbine tower and the top of the foundation, the dynamic response characteristic of the OWTs is qualitatively analyzed. The reason for the difference of dynamic characteristics in different parts of OWTs is structural model characteristic of OWTs：the lower part is a large stiffness pile foundation and the upper part is a high flexibility tower, which makes its dynamic characteristic show the characteristics of the main and subordinate structure. The characteristics of “Main-Subordinate structure” make the tower (subordinate) and pile foundation (main) show different response behaviors under complex ice load, and the vibration period and acceleration power spectrum density (PSD) of different parts of OWTs are different. This study can provide a useful reference for the OWTs anti-ice design and the fatigue analysis of OWTs in cold regions.

Vibration analysis of functionally graded stiffened shallow shells under thermo-mechanical loading

This paper presents a mathematical model to analyse free vibration characteristics of eccentrically stiffened functionally graded shallow shells taking into account the thermo-mechanical loads. The functionally graded shallow shells are simply-supported at all edges and are reinforced by transversal and longitudinal stiffeners on the internal or external surface. The formulation is based on the first-order shear deformation theory with the smeared stiffeners technique for the overall behavior of shells. The equations of motion for eccentrically-stiffened functionally graded shallow shells are obtained using the Galerkin method. The spherical, cylindrical, hyperbolic-paraboloidal shells and plate are modeled and analyzed as special cases by setting components of curvature. Results of the dynamic analysis show that if the number of stiffeners is increased natural frequencies also increases for all the shells but after 10 stiffeners increment is no significant. It is also found that the tendencies of the plate and hyperbolic-paraboloidal shells are similar to each other with the increase in the number of stiffeners and volume fraction index. The effect of volume fraction index is more discernible for spherical shell and least for hyperbolic-paraboloidal.

The Iron-Responsive Genome of the Chiton Acanthopleura granulata.

Molluscs biomineralize structures that vary in composition, form, and function, prompting questions about the genetic mechanisms responsible for their production and the evolution of these mechanisms. Chitons (Mollusca, Polyplacophora) are a promising system for studies of biomineralization because they build a range of calcified structures including shell plates and spine- or scale-like sclerites. Chitons also harden the calcified teeth of their rasp-like radula with a coat of iron (as magnetite). Here we present the genome of the West Indian fuzzy chiton Acanthopleura granulata, the first from any aculiferan mollusc. The A. granulata genome contains homologs of many genes associated with biomineralization in conchiferan molluscs. We expected chitons to lack genes previously identified from pathways conchiferans use to make biominerals like calcite and nacre because chitons do not use these materials in their shells. Surprisingly, the A. granulata genome has homologs of many of these genes, suggesting that the ancestral mollusc may have had a more diverse biomineralization toolkit than expected. The A. granulata genome has features that may be specialized for iron biomineralization, including a higher proportion of genes regulated directly by iron than other molluscs. A. granulata also produces two isoforms of soma-like ferritin: one is regulated by iron and similar in sequence to the soma-like ferritins of other molluscs, and the other is constitutively translated and is not found in other molluscs. The A. granulata genome is a resource for future studies of molluscan evolution and biomineralization.

Nonlinear vibration and dynamic instability analyses of laminated doubly curved panels in thermal environments

Nonlinear dynamic analysis for a shear deformable anisotropic laminated doubly curved panel of rectangular planform resting on elastic foundations is presented. A new panel model of arbitrary curvature and arbitrary fiber stacking sequences but constant thickness is developed and established. The governing equations are based on an extended higher order shear deformation shell theory with von Kármán-type of kinematic nonlinearity and including the anisotropic couplings. The nonlinear deformations and initial deflections of the panel are both taken into account. A two-step perturbation technique combining with the Galerkin method is employed to determine the linear and nonlinear vibration frequencies and forced responses. Nonlinear forced harmonic vibration in a Duffing oscillator for anisotropic laminated doubly curved panel is also investigated and discussed together with the effects of damping and excitation by using multiscale and Melnikov methods. The numerical results are validated for various lamination schemes through a comparison with solutions for free vibration frequencies of saddle (hyperbolic), flat plate, cylindrical and spherical shells available in the literature or obtained by the commercial finite element software. The numerical illustrations concern nonlinear vibration and dynamic response of moderately thick, anisotropic laminated doubly curved panels under different values of panel geometric parameters and mechanical excitation.

A unified power series method for vibration analysis of composite laminate conical, cylindrical shell and annular plate

In this article, the power series method is adopted to investigate the free vibration characteristics of the composite laminated conical, cylindrical shell, and annular plate with arbitrary boundary conditions by the wave based matrix. By the first-order shear deformation shell theory, the governing equation of the composite laminated structure is established. The displacement and moment variables are transformed as the power series function form. Through the introduction of the boundary conditions and the continuous condition between the adjacent segments, the total matrix of the composite structure is established. Searching the zero locations of the total matrix determinant by the bisection method, the natural frequencies of the composite laminated structure under arbitrary boundary conditions are obtained. To further verify the correctness of the solutions by the presented method, some numerical examples are established. From the comparison of the solutions by the presented method and the results in some reported literature and experimental studies, the calculation accuracy is verified. Furthermore, the effect of the geometric parameters and material constants, such are elastic restrained spring stiffness constants, the angle between the shell surface and axis, length to the radius ratios, and modulus ratios, on the free vibration characteristics of the composite laminated structure, have been discussed. The advantage of the presented method is high calculation accuracy, simple matrix assembly, and convenient replacement of boundary conditions. Furthermore, some new numerical solutions are presented in this paper to provide the basic foundation for subsequent research.

Improved quantitative risk model for integrity management of liquefied petroleum gas storage tanks: Mathematical basis, and case study

AbstractChemical, petrochemical, and refinery sectors have been facing tougher safety, environmental and mechanical integrity regulations as well as challenges associated with the need for cost reduction to improve competitiveness. Risk‐based Inspection (RBI) is a cost‐effective approach to manage operational risks by making an informed decision on inspection frequency, extent of inspections, and types of non‐destructive testing. This paper presents a comprehensive practical risk model that can simulate all components of liquefied petroleum gas (LPG) tanks, that is, roof, shell, nozzles, and bottom plates. The probability of failure (PoF) model was developed based on failure frequency data from four different sources to determine the adequate general failure frequencies, moreover, it addresses the fatigue effect due to cyclic loading. Reviewing past losses of containment incidents revealed that fires and explosion are the most likely outcomes, therefore, this risk model introduced area affected consequence of failure (CoF) simulation. The CoF model addresses all the main components of the LPG tank and deploys a practical gas dispersion model to estimate the vapor cloud explosion (VCE) and flash fire consequence affected areas. Furthermore, modified mass release equations are presented to account for the decline in the release rate with time to determine the pool fire area and leak duration. Consequence areas are determined based on serious personnel injuries and component damage from thermal radiation and explosions. To validate the risk model, a proof of concept assessment was performed on seven tanks.

A three-dimensional solution for free vibration and buckling of annular plate, conical, cylinder and cylindrical shell of FG porous-cellular materials using IGA

This study aims to present a three-dimensional (3D) numerical solution for investigating the free vibration and buckling responses of annular plate, conical and cylindrical shell made of functionally graded (FG) porous rock materials. Isogeometric analysis (IGA) is utilized in order to develop the 3D numerical solution. Furthermore, the computational package is developed using C# Programming, which is an object-oriented programming language. The distribution of porosity along the thickness direction obeys the cosine function rule, for which the top surface is porosity-free, and the bottom surface is porosity-rich. The weak form for free vibration and buckling analyses are discretized and approximated through 3D NURBS based IGA. The accuracy of the present solutions is verified by the results obtained from published data. The convergence of 3D FGP solutions is checked, and it is found that a quartic NURBS element can yield high-accuracy results with the lowest computational cost. Afterward, the numerical results showed the impact of porosity of the FGP annular plate, FGP conical, and cylindrical shell on free vibration and buckling problems.

Complex of Settlement Gorodishche-3 Belonging to Fominsky Stage of Kulaiskaya Culture

The article introduces materials of the Fominsky stage of the Kulaiskaya culture from the site in the Itkul microdistrict located in the forest-steppe Altai. It gives a detailed description of the site and its excavation. The site covered an area of 320 m². The excavation revealed a semi-dugout with a pit area of 25 m² and a corridor-type exit, a household building, and other structures. The author focuses on the moat and earthwork line and made a cultural and chronological interpretation of the complex based on ceramic and shell plate. The monument dates back to the late III – first half of the IV century and belongs to the Fominsky stage of the Kulaiskaya culture. The article contains previously unpublished photos of all the artifacts, except plain pottery. The introduction of the presented complex into scientific circulation improves the source base of ancient history studies of the forest-steppe Altai in the first half of the 1st millennium. The complex contains artifacts unpolluted with any culturally similar and chronologically close artifacts, which means that it can help identify the Fominsky stage and their cultural-markers. The matter is important not only for the archaeology of the forest-steppe Altai, but also for the neighboring territories with culturally and chronologically similar complexes in Novosibirsk and Kemerovo Regions.

Experimental investigations into cleaning mechanism of ship shell plant surface involved in dry laser cleaning by controlling laser power

In order to meet the maintenance requirements of ship shell plant, the old polyurethane paint needs to be removed from the ship shell plant. The experiment of repeated cleaning on the surface of polyurethane paint ship shell plate using pulse fiber laser is conducted by the large-scale laser cleaning system which was independently developed. The mechanism of twice repeated pulse fiber laser cleaning method was clarified. In this experiment, the effect of pulsed fiber laser power on surface roughness value was studied. The surface roughness of ship shell plate under different pulsed fiber laser power was obtained. The surface topography of two-dimensional and three-dimensional ship shell plate with different laser power was measured. The results showed that process parameters changed surface topography of ship shell plant by changing laser power. The cross-section profiles of the ship shell plate surface under different laser power are obtained. It is found that the surface height of ship shell plate decreases with the increase of pulsed fiber laser power. The relationship among the pulsed fiber laser power, the surface roughness, and the surface topography was analyzed. The surface topography of ship shell plate obtained by once pulse fiber laser cleaning was compared with that obtained by twice repeated laser cleaning. The experimental results show that twice repeated laser cleaning has a very significant cleaning effect on the removal of polyurethane paint which is on the ship shell plant. The experimental results are of practical significance to the production process of pules fiber laser cleaning for ship shell plate.

Integrity Assessment of Obsolete Thermal Storage Tank in District Heating System

The thermal storage tank in a district heating system is a component that stores excess heat during normal operation and releases the stored heat to increase the efficiency of the system, when the heat source is stopped or additional demands occur. Recently, an obsolete thermal storage tank was dismantled for the first time since it began operation 30 years ago. In this work, the corrosion integrity of the obsolete thermal storage tank was evaluated by examining its appearance, thickness thinning, corrosion products, microstructure, and mechanical properties. Samples were taken at various locations (roof, shell, bottom) of the thermal storage tank, which enabled diagnosis of the respective environmental degradations. Severe corrosion was found in the roof edge plate due to corrosion under the insulation, and exhibited thinning exceeding ~49% of the designed thickness. In this location, the ferrite-pearlite band structure disappeared and deteriorated microstructures, such as decarburization and spheroidized pearlite, were measured, which resulted in a ~27% decrease in hardness. The inner surfaces of the bottom and shell plate were well covered with a magnetite film, and the degradation of the microstructure and mechanical properties showed a permissible limit in terms of ASTM A285/A516. In addition, no particular drop in hardness was found in the weld zone of each plate.

Detection of Transient Junction Temperature Characteristics of High Power IGBT

In this paper, Insulated Gate Bipolar Transistor (IGBT), which is the most widely used full-control power electronic device, is taken as the research object. Under the special working mode of short-time intermittent pulse, with the increase of conduction current, the chip junction temperature of high-power IGBT will rise sharply and fluctuate greatly, causing the operating characteristics of the device to be greatly affected by temperature. The commonly used method of measuring the bottom plate shell temperature with thermocouples and then estimating the steady junction temperature can no longer meet the demand. Firstly, the fluctuation characteristics of junction temperature of high-power IGBT are analyzed. Then, a high-speed infrared thermal imaging device is used to carry out real-time junction temperature detection. The distribution and rising process of instantaneous junction temperature on the chip surface are obtained, which further verifies the correctness of theoretical analysis. The research has important guiding significance for IGBT application design under short-time intermittent pulse operation mode, and also has certain reference value for general operation mode.