Design Of Shells Research Articles

Reinforcement design and buckling analysis of toroidal shell with openings

This paper focuses on the wall reinforcement design of toroidal shells with openings. Five 304 stainless steel test models were manufactured, and geometric measurements, three-dimensional scanning, and hydrostatic tests were carried out. The scanning models were established according to the measured geometrical imperfections. Linear buckling analysis (LBA), geometrically and materially nonlinear analysis (GMNA), and geometrically and materially nonlinear analysis with imperfections (GMNIA) were used for numerical simulations. The test results were in good agreement with the numerical analysis results, and an effective finite element method was obtained. Finally, 51 numerical simulations were established to study the influence of the size, number, and shape of openings on the buckling load performance of the toroidal shell with openings.

ПРОЕКТИРОВАНИЕ МНОГОСТЕНОЧНЫХ КОМПОЗИТНЫХ ОБОЛОЧЕК

This paper investigates a problem of optimal design of a multi-walled cylindrical shell under axial compressive loads. The multi-walled shell consists of two load-carrying layers connected by a set of composite walls. The main structural element of the load-carrying layer is a monolayer comprising parallel-laid fibers that are interconnected by a polymer binder – a matrix. The wall represents a unidirectional composite made from the same material as the load- carrying layers. Both strength and stability constraints are taken into account during mathematical modeling. The critical load corresponding to a general form of buckling is determined by a classical formula for an orthotropic shell with “reduced” stiffnesses. The critical load corresponding to a local form of buckling is calculated using the well-known formula for a smooth orthotropic plate. The target function is the mass of the structure. The solution to the problem of optimal design of a multi-walled structure is proved to be unique. The conditions ensuring the existence of the problem solution are formulated. The example of evaluating the efficiency of reinforcing elements in a shell structure is given. The presented research results can find application in design problems for modern composite structures in rocket and space industry.

РЕЗЕРВ АНАЛИТИЧЕСКИХ ПОВЕРХНОСТЕЙ ДЛЯ АРХИТЕКТУРЫ И СТРОИТЕЛЬСТВА

After a period of relative calm in the construction and design of thin-walled large-span shells and network multilayer shell structures, which, according to the world's leading architects, began in the 1980 s, the time has come for the expanded use of spatial structures in the architecture of public and industrial buildings. Less commonly, shells are used in small-sized housing construction: ecological villages, noospheric and bionic architecture. The entire 20th century did not stop research on the development of analytical and numerical methods for analyzing shells for strength and stability, for the creation of new building materials. Geometers have created and studied more than 600 analytical surfaces that can be mistaken for the mid-surfaces of civil and mechanical engineering shells. As a result, by the beginning of the 21st century, architects and engineers had all the necessary tools to continue the traditions of the "golden age of shells". The analysis of problems with the use of new forms in parametric architecture, carried out in the article, showed that more than ten classes of surfaces from their classification have not yet found application in architecture and mechanical engineering. It is assumed that the number of applied classes of surfaces will not expand, and new ideas for the shaping of shells will be based on the use of already well-known surfaces, namely, surfaces of revolution, transfer, umbrella, minimal, ruled and wavy surfaces. Mainly, shell structures will be designed taking into account environmental, energy-saving requirements and transforming structures.

Optimisation of crack groove depth of QT450 rear axles' main reducer shell bearing seats based on numerical analysis

This paper studies the fracture splitting of shell bearing seat, and determines the optimised range for prefabricated crack groove depth. Firstly, crack initiation during the fracture splitting process of shell bearing seat is numerically simulated. Secondly, the fracture-split force of different crack groove depths is determined. Finally, plastic deformation and out-of-roundness of the shell bearing seat at different crack groove depths are investigated. The results show that the crack initiation point of the reducer shell bearing seat is located near the middle of the crack tip and the position is slightly closer to the flat end face side. Plastic areas with different crack groove depths produced at the root of the crack tip are butterfly-shaped distribution and the out-of-roundness of bearing hole is small. This shows that fracture-splitting technology is suitable for shell bearing seat. The result provides rationality for the design of reducer shell bearing seat cracking equipment and prefabricated crack groove parameters. [Submitted 7 November 2018; Accepted 27 July 2019]

On-Surface Bottom-Up Construction of COF Nanoshells towards Photocatalytic H2 Production.

The rational design of an outer shell is of great significance to promote the photocatalytic efficiency of core-shell structured photocatalysts. Herein, a covalent organic framework (COF) nanoshell was designed and deposited on the cadmium sulfide (CdS) core surface. A typical COF material, TPPA, featuring exceptional stability, was synthesized through interfacial polymerization using 1, 3, 5-triformylphloroglucinol (TP) and p-phenylenediamine (PA) as monomers. The nanoshell endows the CdS@TPPA nanosphere with ordered channels for unimpeded light-harvesting and fast diffusion of reactants/products and well-defined modular building blocks for spatially charge separation. Moreover, the heterojunction formed between CdS and TPPA can further facilitate the effective charge separation at the interface via lower exciton binding energy compared with that of pristine TPPA. By modulating the thickness of TPPA nanoshell, the CdS@TPPA nanosphere photocatalyst with the nanoshell thickness of about 8 ± 1 nm exhibits the highest photocatalytic H2 evolution of 194.1 μmol h−1 (24.3 mmol g−1 h−1, 8 mg), which is superior to most of the reported COF-based photocatalysts. The framework nanoshell in this work may stimulate the thinking about how to design advanced shell architecture in the core-shell structured photocatalysts to achieve coordinated charge and molecule transport.

Optimisation of crack groove depth of QT450 rear axles' main reducer shell bearing seats based on numerical analysis

This paper studies the fracture splitting of shell bearing seat, and determines the optimised range for prefabricated crack groove depth. Firstly, crack initiation during the fracture splitting process of shell bearing seat is numerically simulated. Secondly, the fracture-split force of different crack groove depths is determined. Finally, plastic deformation and out-of-roundness of the shell bearing seat at different crack groove depths are investigated. The results show that the crack initiation point of the reducer shell bearing seat is located near the middle of the crack tip and the position is slightly closer to the flat end face side. Plastic areas with different crack groove depths produced at the root of the crack tip are butterfly-shaped distribution and the out-of-roundness of bearing hole is small. This shows that fracture-splitting technology is suitable for shell bearing seat. The result provides rationality for the design of reducer shell bearing seat cracking equipment and prefabricated crack groove parameters. [Submitted 7 November 2018; Accepted 27 July 2019]

Development of a prototype hydrogen vehicle

Developing technology, new technologies, and changing world standards have led researchers to search for new energy sources. In addition to countries such as America, Germany, and Japan, most automobile manufacturers have been able to adapt to changing standards, have done major researches on alternative energy vehicles, and have started to market their products. In this study, a prototype hydrogen vehicle was developed for TÜBİTAK Efficiency Challenge Electric Vehicle Organization. Design criteria were determined within the limits of the competition rule book. A computer-aided design (CAD) program was used in the vehicle shell and mechanical part designs. Vehicle flow analysis was carried out with the help of computational fluid dynamics (CFD) program. Laboratory condition long-term performance test of the fuel cell has been carried out and whether the fuel cell power was sufficient for the vehicle.

Fluid-Structure Interaction on The Design of Fully Assembled Shell Eco-Marathon (SEM) Prototype Car

To achieve high fuel efficiency, vehicles designs are inclined to choose lightweight materials and structures. However, these structures are generally weak, and structural integrity is a common concern. The purpose of this paper is to carry out fluid-structure interaction (FSI) study in one-way coupling analysis on a Shell Eco Marathon (SEM) prototype car which travels in a low-speed range to analyse its structural response. A new set of economical materials is proposed and analysed with the concern on self-fabrication process. The Flax fibre composite is introduced as a part of the proposed material set due to its environmental and economic advantages. The study herein is purely a numerical simulation work as a first approach to design a sustainable SEM prototype car. The fully assembled SEM prototype car was analysed with the proposed materials with ANSYS Workbench in the coupling of the fluid (ANSYS Fluent) and structural solver (ANSYS Mechanical) in a one-way FSI. Even with a thin shell design, the proposed material only experiences minimum deformations. The simulations also reveal that the maximum von-Mises stress experienced, after considered the safety factor, is still several order lower than the yield strength. This study has confirmed that the car design has fulfilled its structural requirements to operate at the design speed.

The Influence of Hard Hat Design Features on Head Acceleration Attenuation.

This study evaluated the performance of 6 commercially available hard hat designs-differentiated by shell design, number of suspension points, and suspension tightening system-in regard to their ability to attenuate accelerations during vertical impacts to the head. Tests were conducted with impactor materials of steel, wood, and lead shot (resembling commonly seen materials in a construction site), weighing 1.8 and 3.6kg and dropped from 1.83m onto a Hybrid III head/neck assembly. All hard hats appreciably reduced head acceleration to the unprotected condition. However, neither the addition of extra suspension points nor variations in suspension tightening mechanism appreciably influenced performance. Therefore, these results indicate that additional features available in current hard hat designs do not improve protective capacity as related to head acceleration metrics.

Design of New Fin Baffle Shell and Tube Heat Exchanger for Heating of Biodiesel Fuel Based on Simulation

Design of New Fin Baffle Shell and Tube Heat Exchanger for Heating of Biodiesel Fuel Based on Simulation

Mimetic-core-shell design on molecularly imprinted membranes providing an antifouling and high-selective surface

Selective separation of CFX achieved by CIMs with mimetic-core–shell design. • Mimetic-core–shell design was developed on ciprofloxacin-imprinted membranes. • Enhanced antifouling property was achieved by β-cyclodextrin/PVDF envelope. • Selectivity was provided by imprinted sites based on thiol-ene click reaction. • Visual simulation was employed for an in-depth investigation of mechanisms. Molecularly imprinted membranes (MIMs) developed from membrane separation technology and molecularly imprinting technology have shown great advantages in water treatment, drug extraction and biochemical separation. Inspired by superiority of core–shell structure onto nanomaterials, the mimetic-core–shell design on MIMs would possess both properties of substrate (core) and molecularly imprinted polymers (shell). In this work, a mimetic-core–shell structure was carried out on ciprofloxacin-imprinted membranes (CIMs) for the supplement of antifouling and high-selective surface. (i) Antifouling performance was enhanced based on β-cyclodextrin by forming the supramolecular envelope system with the substrate. (ii) Selectivity was provided by CFX-imprinted sites on the embedded secondary platform (polydopamine). As a result, impressive rebinding selectivity ( α CFX/NFX = 3.47, α CFX/EFX = 3.91 and α CFX/OFX = 5.42) and permselectivity ( β NFX/CFX = 1.57, β EFX/CFX = 1.68 and β OFX/CFX = 1.83) with stable regeneration performance were achieved on optimal CIMs (M4-CIMs). The structure-performance relationship of CIMs were explored by chemical and morphology analyzation. Visual-simulative method was included for a detail and in-depth investigation of sites formation and selective recognition mechanisms. Importantly, results from dead-end filtration of semi-practical samples reveals the potential availability of mimetic-core–shell CIMs for selective separation applications.

Melting performance enhancement of PCM based thermal energy storage system using multiple tubes and modified shell designs

In this paper, experimental and numerical investigations are performed for heat transfer enhancement in a horizontal Latent Thermal Energy Storage System using multiple heat transfer tubes and modified shell designs. Stearic acid is used as phase change material and it is placed in the annulus of steel shell and copper tubes carrying water as the heat transfer fluid (HTF). A single Y-fin HTF tube, used as Base Case, is split up into 2 – 5 tubes with different arrangements while ensuring constant mass of the PCM. The vertical double tube and triple tube V-configuration improve the average heat transfer rates by 33.6% and 23.7%, respectively, as compared to the Base Case. The corresponding complete melting times is also reduced by 27.7% and 21.7%. Additionally, elliptic and triangular shell design modifications are proposed for double and triple tube arrangements, respectively. Both configurations increase the average heat transfer rate by 85% which results in reduction of the complete PCM melting time by 50% with respect to Base Case of Y-fins single tube arrangement. In comparison to the Base Case, an increase in HTF temperature of 5.6% improves the average Nusselt number by more than 37% for both the cases. Additionally, the correlations for melting Fourier number and average Nusselt number are also developed.

Stress-strain state of a three-layer cylindrical shell under internal axisymmetric pulse load

The problem of dynamic deformation of a three-layer cylindrical shell under non-stationary loads in the case of rigid clamping of the shell ends is considered. The article presents the results of assessing the stress-strain state of a three-layer cylindrical shell, taking into account its structural feature, the ratio of the sheathing thickness and the physical and mechanical characteristics of a one-piece polymer filler. Calculations were performed by software complex Nastran. The values of displacements and stresses were calculated by the algorithm of direct transient dynamic process. The step duration of the time interval was 0.0000025 s, and the total number of steps was 200. The choice of the type of three-dimensional finite element was due to obtaining more detailed and accurate calculation results. The finite element model included 19000 three-dimensional finite elements and numbered 20800 nodes.
 The influence of geometrical parameters of shell layers with different physical and mechanical properties of one-piece filler on the stress-strain state under axisymmetric internal impulse load is investigated. Numerical results on the dynamics of the three-layer structure, obtained by the finite element method, allow to characterize the stress-strain state of the three-layer elastic structure of the cylindrical type at any time in the studied time interval. Optimization of the shell design is recommended. Changing the ratio of the thickness of the internal and external shells of the shell significantly affects the stress-strain state of the shell and its performance. Increasing the thickness of the internal layer of the shell significantly contributes to the increase of the latter. Comparison of the given results with materials of other similar researches and positions, testify to objectivity of the made approach.

An isogeometric framework for the optimal design of variable stiffness shells undergoing large deformations

The optimal design of the postbuckling response of variable angle tow composite structures is an important consideration for future lightweight, high-performing structures. Based on this premise, a new optimisation tool is presented for shell-type structures. The starting point is an isogeometric framework which uses NURBS interpolation functions to provide a smooth description of the deformed shapes, thereby reducing the number of degrees of freedom with respect to standard finite elements. The stiffness variation is obtained by exploiting the same NURBS interpolation to describe lamination parameters, employed as intermediate optimisation variables. This choice allows the design space to be thoroughly explored with relatively few design variables in a smooth optimisation space. Therefore, the optimisation strategy is divided into two stages. Firstly, the optimal distribution of lamination parameters is determined using a gradient based algorithm. Afterwards, an actual distribution of fibre orientation is retrieved. The viability of the tool is tested firstly onto a cylindrical panel under compressive loading. Then, the postbuckling optimisation of a composite wingbox is given. For both structures, the optimised postbuckling response is compared with those of the corresponding quasi-isotropic baselines showing significant improvements.

Exergy analysis of Shell and helical coil heat exchanger and design optimization

In this study, experimental investigations and exergy analysis on shell and helically coiled tube heat exchanger are carried out for free convection heat transfer. The measured data are totally optimised utilizing thermodynamics rules in which exergy study is performed to investigate the thermal performance of the helical system under different operating conditions. The experimental set-up of apparatus are designed and made for cold water and hot water as a working fluid of both the shell side and helical coil side, respectively. The effects of several parameters such as geometry and operational conditions on the exergy destruction and dimensionless exergy destruction are investigated. The counter flow direction is considered under the steady state flow condition, and the critical Reynolds number was more than 4000 in this study. The main objective of this work was to clarify the effect of the volume flow rates and inlet temperatures of hot water and cold water in the shell and helical coil on exergy efficiency and pressure drop. Results showed that the exergy destruction and dimensionless exergy destruction decrease with the increase of coil pitch and Dean number. In contrast, the exergy destruction and dimensionless exergy destruction are obviously increased with the hot water flow rates or cold water flow rates. These exergy characteristics are also augmented with the values of hot water inlet temperatures and cold water inlet temperatures. The pressure drop is considerably increased with the increase of Dean number and reduced with the increase of coil diameter. While, the exergy efficiency steadily increases with the decrease of the cold water flow rates and with the increase of Dean number.

Design, Fabrication and Testing of Shell and Tube Heat Exchanger Integrated with Vacuum Tubes Solar Water Heater

Heat exchanger is a device used to accomplish the transfer of heat from one fluid to another. There are a wide variety of applications regarding shell and tube heat exchangers in the fields of petroleum and industrial applications, due to its enhanced heat transfer characteristics. This project was designed to establish an insight of detailed design and performance of the shell and tube heat exchanger based on energy and mass conservation laws. Solar water heating system techniques were used to provide the system with necessary hot water. One of these techniques was to evacuate tube solar heating system which can be considered as a more efficient way to supply this system with hot water. To enhance the system performance, proper material selection for shell and tubes structure and flow pipe network based on their availability in the local markets was brought into consideration as well. Furthermore, the implemented design was examined under Medina climatic conditions for its cost-effectiveness, simplicity, execution and sustainability. It was found that the heat exchanger efficacy, performance and the vacuum tube efficiency were in highly acceptable ranges and cost effective. In addition, the vacuum tube solar water heating was found to be a clean and safe source of renewable energy. Finally, a comprehensive analysis of the system effectiveness was conducted and the outlet temperature determined for the system varied between 44 to 50ºC for the heat exchanger whereas the vacuum tube exit temperature was elevated up to 84 to 90ºC. The efficiency of the solar collector was found to be 61.84%.

Geometry and classification of carved Monge surfaces

There are more and more needs of new forms in the world architecture. The thin shells theory and the surfaces theory give enough materials to scientifics and designers. This article is devoted to the geometric investigation of carved Monge surfaces. The geometry of these surfaces is inner and outer. For this, the coefficients of their fundamental forms are found and allow the classification of these surfaces. The kinetic method is used for their geometric investigation and classification. The parametric definitions of these multitude forms of carved Monge surfaces allow the 3D plotting of these surfaces by mean of the software MathCAD. The results obtained by this investigation are their vector, implicite, explicite and parametric definitions, the mathematic modelling of their inner and outer geometry, their 3D plotting and their classification. This variety of carved Monge surfaces can be used as the median surface of thin elastic shells design from them. The geometry these elastic shells, because their thin is the one of the carved Monge surfaces. The multitude of the designed thin elastic shells are expressive, durable and cover large spans. The multitude of their forms can find applications in the architecture of civil and industrial buildings and also in mechanical engineering.

Heinz Isler’s twin shell roof in Deitingen – preservation of a ‘timeless wing beat’

The Swiss shell pioneer Heinz Isler (1926–2009) fundamentally challenged established shell design methods by introducing original methods of form finding based on gravity. He realised elegant and pure shell forms in reinforced concrete, incarnating the perfect match of structural efficiency and form. With his shells, he gained acclamation of structural engineers and architects, and of the public. Heinz Isler’s more than 1400 built concrete shells are mostly located in Switzerland. The twin shell roof for the motorway rest area in Deitingen, Switzerland, and recent maintenance works to preserve this monument of structural art are described. After more than 50 years of use, the good condition and unaltered technical performance of the shells speak for Isler's excellent engineering work. The principle that well-designed structures are more durable is confirmed once again. Due to the non-invasive maintenance works carried out in 2016, the substance and aesthetics of the shells, which are one of the most successful and boldest engineering designs by Heinz Isler, are preserved for the shells to serve as a landmark on the motorway for decades.

Constrained Force Density Method optimisation for compression-only shell structures

The Force Density Method is a powerful tool for the design of efficient long-spanning shells and gridshells, as it can generate structural forms that utilise membrane action. However, force density distributions are defined by the user, which does not lead to the most effective structure with regards to material usage, or in enabling the control of member lengths. This paper presents a Constrained Force Density Method (CFDM) optimisation, that assembles the force density distribution for the user, and allows constraints on forces, force densities, lengths and the spatial movements of vertices. The focus is on shell and gridshell type structures, with compression-only internal force states. The optimisation algorithm’s objective function combines the minimisation of the total volume of material in the structure and control of the member lengths. Described is a computational implementation that efficiently solves the constrained non-linear programming problem, by exploiting symmetry, fast solvers, and analytical gradient functions. Results of three practical case studies show that the CFDM can lead to material savings of between 21% to 66% when compared to uniform force density distributions, while providing full control on the lengths of the structural elements and the spatial movement of vertices. It opens up possibilities in engineering design, enabling the exploration of many new lightweight structural forms, and offering many sustainability, fabrication and construction advantages.

Heat exchanger network synthesis with detailed exchanger designs: Part 1. A discretized differential algebraic equation model for shell and tube heat exchanger design

AbstractA new method for the detailed design of shell and tube heat exchangers is presented through the formulation of coupled differential heat equations, along with algebraic equations for design variables. Heat exchanger design components (tube passes, baffles, and shells) are used to discretize the differential equations and are solved simultaneously with the algebraic design equations. The coupled differential algebraic equation (DAE) system is suitable for numerical optimization as it replaces the nonsmooth log mean temperature difference (LMTD) term. Discrete decisions regarding the number of shells, fluid allocation, tube sizes, and number of baffles are determined by solving an LMTD‐based method iteratively. The resulting heat exchanger topology is then used to discretize the detailed DAE model, which is solved as a nonlinear programming model to obtain the detailed exchanger design by minimizing an economic objective function through varying the tube length. The DAE model also provides the stream temperature profiles inside the exchanger simultaneously with the detailed design. It is observed that the DAE model results are almost equal to the LMTD‐based design model for one‐shell heat exchangers with constant stream properties but shows significant differences when streams properties are allowed to vary with temperature or the number of shells are increased. The accuracy of the solutions and the required computational costs show that the model is well suited for solving heat exchanger network synthesis problems combined with detailed exchanger designs, which is demonstrated in Part 2 of the paper.