Steel Cylindrical Shells Research Articles

Effect of Carbon-Coating on Internal Resistance and Performance of Lithium Iron Phosphate Batteries

In this paper, the LiFePO4 material was modified by carbon coating using polyvinyl alcohol (PVA) and Ketjen black as the composite carbon sources. Firstly, the structure, electron and ion transport properties of LiFePO4 and carbon-coated LiFePO4 were calculated by first-principles and density functional theory. The calculation results show that after carbon coating, the coating system will change from semiconductor properties to conductor properties, and its electronic conductivity will be significantly improved. Then, different proportions of Ketjen black and PVA (polyvinyl alcohol) were mixed to prepare a composite carbon source, which was then coated with carbon on the surface of the LiFePO4 cathode material. The prepared LiFePO4/C samples were characterized by XRD, SEM, physical properties and electrochemical properties. The 14500 cylindrical steel shell battery was prepared by using lithium iron phosphate materials coated with different carbon sources. By testing the internal resistance, rate performance and cycle performance of the battery, the effect of carbon coating on the internal resistance of the battery and the electrochemical performance of the full battery was studied and analyzed. The experimental results show that when Ketjen Black:PVA = 2:1, the synthesized LiFePO4/C cathode material exhibits the best rate performance and cycle stability. The compaction density of the pole piece is reduced, the internal resistance of the battery is reduced, and the electrochemical performance of the battery is improved.

Analysis of the stress-strain state when knurling riffles in a steel cylindrical shell

Obtaining shells with riffling inner surface is a complex and urgent task, therefore, a new riffling method has been developed, which is characterized by high efficiency and low metal consumption of the structure relative to existing ones. At the same time, there are practically no works devoted to the assessment and study of stresses, deformations, and material damage when knurling by local form change. The paper analyzes the intensity of deformations, average stresses and the risk of destruction when knurling the inner surface of the shell during local shaping using tools that have different-shaped lead-in parts of the wedge protrusions. A comparative analysis of the stress-strain state is performed for various methods of knurling in one direction – local shaping and reduction through a conical matrix. The study was carried out in order to determine the most appropriate method of knurling in terms of obtaining the favorable stress-strain state. The stress-strain state when knurling of the opposite direction in the zone of their intersection in the process of forming a mesh of riffles by local shaping is also considered. To solve the problem, computer simulation was carried out in the DEFORM program with subsequent interpretation of the results.The work was carried out within the framework of the grant of the Government of the Tula region in the field of science and technology No. DS/167.

Experiments on welded shells with section alteration under axial and peripheral pressure

This research elaborates the interactive response of thin steel cylindrical shells under axial and uniform peripheral pressure. The method of the research was mainly experimental, which was evaluated against theoretical analyses of other studies and design standards. The geometric variable was applied as thickness variation in a stepwise manner whilst designing the specimens; this is seen in cylindrical shells employed as storage structures such as silos. The axial loading was applied as a constant pre-loading to all specimens, which followed by applying uniform pressure that increased until the initial buckling, global buckling (hereafter called buckling in this paper), and collapse of the specimens were observed.The results underscored the significance of the slenderness on the capacity of the shells with varying thicknesses. For shells with lower slenderness values of the bottom strake(s), a more stable post-buckling response was identified. These specimens experienced somewhat symmetric formation of the buckling lobes compared to the specimens with a single strake. The capacity rise was also evaluated against the mass gain, and for some specimens, an insignificant mass gain led to a remarkable capacity gain.

Dynamic fragmentation in steel cylindrical shells

The paper describes an experimental study of the influence of the composition and mechanical properties (ultimate and yield strength, reduction of area, impact toughness, and the fraction of fibrous fracture) of brittle, quasi-brittle, and ductile steels on the parameters of dynamic fragmentation and fracture mechanisms. The experiment showed that simple exponential functions could be used to describe cumulative mass distributions of shell fragments from the materials under study. The exponent of these functions is the reciprocal characteristic mass (1/μ) and it decreases as the fraction of fibrous fracture of shell fragments increases. It serves as a dynamic fracture criterion that is sensitive to changes in the composition and mechanical properties of the material. The relations between the fragmentation parameter 1/μ and mechanical properties and composition of shell materials were obtained. Reaching the critical value of the fragmentation criterion (1/μc) leads to changing the fracture mechanism from “ductile” to “brittle” mode which arises in a material with ∼40% of fibrous fracture at the fracture surface of impact specimens and ∼50% of shear fracture of fragments.The authors studied the structure and features of ductile and brittle fracture surfaces of shell fragments, compared the statistical distributions widely used to describe the fragmentation process (Mott, Weibull, and Grady-Odintsov) and the dependencies of their parameters on material properties. The study did not reveal any advantages of the parameters of these distributions over the 1/μ parameter of the exponential function. The analysis of the literature data on the fragmentation of shells of different steels showed that they did not contradict the obtained results, and the usage of simple exponential distributions makes it possible to reveal the physical meaning of parameters of statistical distributions. Several common patterns of fragmentation of solids are discussed.

On the Optimal Design of Steel Shells with Technological Constraints

This paper is concerned with determining the optimum conditions of steel cylindrical shells with technological limitations and one behavioral constraint, related to a specific constitutive law for limiting load-carrying capacity. The optimum structural design in the plastic range of circular cylindrical full shells composed of rings of variable thickness is given. A numerical procedure for determining the optimal dimensions of shell rings is given. A shell collapse mechanism is assumed in the kinematic part, which satisfies requirements. Within the optimum conditions, the power of the dissipation energy of rings assuming the hexagon Hodge condition of plasticity are derived. A series of numerical solutions and results of optimal structural designs for a shell that is simply supported at the ends are presented. In one example of optimally calculated shells, the length X1 of one ring was varied.

Elastic-plastic Buckling Analysis of Q690 High Strength Steel Tubes Under Global Bending

In recent years, high-strength steel has been used extensively for infrastructures because of its many advantages, such as its ductility and strain-hardening properties, which are inferior to those of ordinary structural steel, and the small dimensions of the structural elements, which lead to greater freedom and elegance in design, resulting in lighter structures. In practice, imperfections such as residual stresses due to the welding process and pre-buckling mode imperfections are inevitable in cylindrical structures made of high-strength steel. A small imperfection amplitude can lead to a disproportionate reduction in buckling strength. Therefore, imperfection sensitivity should be considered when studying the buckling behaviour of the shell. The influence of the combined residual stress and pre-buckling mode imperfection on the buckling behaviour of Q690 high strength steel cylindrical shell under global bending has not yet been investigated and described for all dimensions. In this paper, the combined imperfections influences on the buckling behaviour of high-strength steel cylindrical shell in global bending in the elastic-plastic range are investigated. Using the ABAQUS fine elements software, perfect cylinders with a constant length to thickness ratio equal to 7 and a radius to thickness ratio in the range 10≤ r/t ≤700 were considered to perform the linear bifurcation analysis (LBA) and the geometric nonlinear analysis (GNA). The non-linear analysis with imperfections (GNIA) and the geometric and material non-linear analysis with imperfections (GMNIA) were then performed considering imperfection amplitudes between 0.01 and 2 to derive the critical buckling loads known as bifurcation point for the models with different aspect ratio. The influences of the combined imperfections show that moderately and very thin cylinders are very sensitive to the increase of the pre-buckling mode imperfection amplitude and their buckling strength is insensitive to plasticity. For thick cylinders, the effect of plasticity is more consistent, while the buckling strength is not significantly affected by the increase in pre-buckling mode imperfection amplitude. The main objective is to predict the buckling sensitivity of cylinders under the influence of combined residual stress and pre-buckling mode imperfection. The obtained results, comments and conclusions intend to allow for safer.

Prediction of Nine Quasi-Isotropic Thin Steel Cylindrical Shells Axial Buckling Capacity Under Bending (Plasticity) and Axial Compression (Linear Elasticity)

Prediction of Nine Quasi-Isotropic Thin Steel Cylindrical Shells Axial Buckling Capacity Under Bending (Plasticity) and Axial Compression (Linear Elasticity)

Investigation on the technology of soft recovery of fragment produced by metal cylindrical shell subjected to explosive loading

According to the requirements on the soft recovery of fragments of expanding cylindrical metal shells under explosion loading, this paper presents a recovery device combining low density polyurethane foam and water medium through theoretical analysis and numerical simulation. Compared to traditional recovery device designed with a single material, the combined recovery device can reduce the amplitude of impact pressure, which is produced by the initial interaction of low impedance polyurethane foam with high speed fragments, by about 1/3 compared to the impact pressure produced by water, and maintain the high decay rate of fragment speed. It can also make full use of the advantages of high density of water medium when the fragment speed is less than 0.5 km/s, which can reduce the decay thickness of the recovery device based on single polyurethane foam. Based on the device, the recovery experiment of expansion and fracture of 304 stainless steel cylindrical shell under explosive loading is carried out. Through the measurement of the wall velocity of the recovery tank and the appearance inspection after the experiment, it is implied that the wall and bottom of the recovery tank are in good condition and can be reused. According to the statistics of the recovered fragments, the recovery rate of the fragments is more than 85%, and the internal and external interfaces of fragments are highly recognizable, the turning blade lines on the surface of the fragments are clearly visible, and several non-penetrating cracks are visible, which verified that the impact damage of the recovery device to the fragments is significantly reduced. Acording to the fracture and surface information of the fragments, the approximate position of the fragments in the metal cylindrical shell is inferred.. Finally, the statistical results of the average thickness and mass distribution of the recovered fragments are given.

Corrosion rate measurement for steel sheets of a fuel tank shell being in service

Abstract Some corrosion progress trends specific for cylindrical steel shells of typical above-ground fuel tanks are first identified experimentally and then quantitatively compared with one another. The inference is based on many random thickness measurements related to the selected corrosively weakened coating sheets and carried out at various moments of the tanks in question service time. It is shown in detail that in this type of structures, due to the manner of their use and, particularly, the material stored inside, the corrosion process is in general significantly accelerated over time. For this reason, a nonlinear formal model describing the simulated corrosion development anticipated for the future fuel tank service time seems to be the best choice in forecasting its remaining time to failure.

Aging Behavior of Lithium Titanate Battery under High-Rate Discharging Cycle

The high-rate discharging performance of a lithium titanate battery is one of its main properties. In conditions that require ultra-high-rate discharging, a lithium titanate battery can be discharged continuously at a current of 50 C (50 times of its maximum capacity) or higher. In this paper, we take cylindrical steel shell lithium titanate cells as the research object and perform aging cycles at 66 C on these cells. The ultra-high-rate discharging cycles cause a rapid high-power capacity fading while the available capacity at normal current rate is not affected. The capacity at 66 C decreases to 80% of initial value in 10 cycles. This paper also analyzes the aging process of a lithium titanate battery at high-rate discharging with incremental capacity (IC) analysis, and presents the aging behavior of lithium titanate battery qualitatively, which is inconsistent with existing research. We attribute the aging mechanism of ultra-high-rate discharging cycles to the decrease of ionic mobility and increase of polarization resistance. Mechanical damage is observed in the CT scan of an aged cell, which we presume to be the result of rapid strain of cathode material.

Buckling behaviors of thin-walled cylindrical shells under localized axial compression loads, Part 1: Experimental study

Thin-walled cylindrical shell structure not only shows the highly efficient load carrying capacity but also is vulnerable to buckling instability failure. In practical application, these structures are usually subjected to localized axial compression load, which is a common but complex non-uniform loading case. Until now, the buckling behaviors of thin-walled cylindrical shells under this kind of compression loading condition are still unclear, and there are also few relevant investigations. In order to fill this research gap, in the first part of this series paper the experimental studies on the buckling behaviors of thin-walled cylindrical shells under localized axial compression loads were performed for the first time. The buckling tests of twenty-one steel cylindrical shells were carried out in this paper and some key experimental details were given. The strain curve, axial load–displacement curve, critical buckling load as well as the buckling modes of cylindrical shells under localized axial compression load were systematically discussed. Test results indicated that the localized axial compression load plays a pivotal role in the buckling behaviors of thin-walled cylindrical shell, not matter from the point of view of load carrying capacity, load–displacement curve or buckling mode. The experimental results obtained from this work can be served as a benchmark for related research in this field of buckling analysis of thin-walled cylindrical shells.

A solution to the problem of stability of thin-walled steel cylindrical shells

Introduction. It is necessary to improve methods of analysis of the limit states, occurring when a thin-walled shell is in the elastoplastic domain, to use these cylindrical shells as elements of heavily loaded products of construction and machine building industries. Materials and methods. The problem of stability of a circular thin-walled cylindrical shell, made of steel 45 GOST 1050-2013, that takes the load induced by pure compression and axial torsion, has been studied. Besides, experimental and theoretical components of the problem have been analyzed. Experimental facility SN-EVM was applied to perform an experiment test and analyze its findings in terms of different versions of the theory of plasticity used to solve shell stability problems beyond the elastic limit. The co-authors emphasize the unavailability of any definition of the criterion of stability loss under combined loading based on experimental dependences that were identified earlier. The results of the experiment were compared with the results of the theoretical study. The analysis of the shell stability in the case of complex subcritical loading are based on the A.A. Ilyushin theory of stability, in which plasticity functions are taken according to V.G. Zubchaninov’s approximations. Results. The problem was solved using the software programme, developed by the co-authors. The software solves the bifurcation problem of a cylindrical shell with regard for the complex nature of deformations at the moment of stability loss in the case of exposure to complex subcritical loading, commensurable processes and the trajectory that has the form of circular arcs. It has been shown that the proposed method of analysis and approximations describe the real stress-strain state of shells that feature low flexibility in respect of a complex pattern of deformation and characterize a stable state of the material beyond the elastic limit. Conclusions. The theoretical strength and deformability analysis of a cylindrical shell and its experimental studies demonstrate sufficient convergence which proves their reliability. This conclusion will allow to improve the process of design of structural elements made of materials that have complex mechanical properties.

Testing of thin-walled cylindrical shells made of steel 45 in solving the problem of stability

The theory of shell stability beyond the elastic limit is considered when studying the issue of testing, diagnostics and quality control of materials made of steel shells of round cylindrical cross-section. Since, depending on the history of the loading process of an elastic-plastic system, its final deformation corresponding to the same external load is different, by studying the inelastic stability problems should proceed from the analysis of simple combined loading processes that lead to different critical deformations. Not only the question of the loading history, which leads to the minimum value of critical loads, but also the question of choosing and implementing such a loading history of a given system, which gives it the maximum value of the stability limit and the load-bearing capacity of the material, is solved. Innovative methods are proposed for solving the problem of shell stability in tests of complex loading of steel cylindrical shells by internal pressure, compression and torsion in the direction of structural mechanics and mechanics of deformable solids, implemented on an experimental complex. The obtained results allow us to determine the loss of stability of the material beyond the elastic limit with a sufficient degree of accuracy for a given cross-section and the loading trajectory of a cylindrical thin-walled shell made of steel 45, while the correctness of the obtained results is justified experimentally.

Numerical and Experimental Investigation on Post-buckling Behavior of Stiffened Cylindrical Shells with Cutout subject to Uniform Axial Compression

In this paper, post buckling behavior of thin steel and aluminum cylindrical shells with rectangular cutouts under axial loading was studied experimentally and also using the finite element method. Riks method is used for analyzing the cylindrical shells. The effect of longitudinal and circumferential stiffeners (ribs and stringer) was studied on the buckling load and the post buckling behavior as the stiffeners used individually and in combination with each other. It was shown that by adding stringer, the buckling load improves and the rib has a positive effect on the post buckling behavior of the structure. Some tests were performed by ZwickRoell tensile/compression testing machine and it was carried out for both types of steel and aluminum shells with and without stiffeners. Comparing the experimental results with the FEA results shows good agreement. Nonlinear analysis of cylindrical steel and aluminum shells with cutout have demonstrated that, in some cases, a local buckling called snap-back can be seen in the load-displacement path. Snap-back which is a decrease in the amount of both load and displacement indicates this local buckling. This phenomenon is because of appearing mode shapes sequentially during the numerical buckling analysis of shells. Although these local buckling happened, the structure is still endured the higher loads.

Assessment and design considerations for single layer cylindrical lattice shells subjected to seismic loading

This paper examines the main considerations related to the seismic design and assessment of single layer steel cylindrical lattice shells, and offers recommendations for their practical application. Geometric configurations covering a wide range of rise to span ratios are considered within the investigation. An insight into the relative influence of seismic loading on shell design, in comparison to gravity conditions, is firstly provided through the use of digital parametric engineering procedures. This is followed by linear elastic response assessments which are used to propose a simplified procedure for estimating the internal seismic forces for the purpose of member sizing in early design stages. Suitable approaches for pushover analysis are then discussed and used to identify inherent plastic mechanisms. The results of incremental nonlinear dynamic analysis, using a suite of fourteen records, are also employed in order to validate the findings and to further assess the ultimate response under realistic seismic loading conditions. Based on the findings, representative ranges for behaviour factors and displacement modification coefficients are derived alongside discussions on their implementation within codified seismic design procedures. Apart from providing recommendations for simplified design approaches, the assessments presented in this paper can also be used to support detailed performance based guidelines as well as for informing geometry and size optimisation strategies.

The effect of different retrofitting techniques on the axial load carrying capacity of damaged cylindrical shells

Load-carrying and deformation capacity of the steel cylindrical shells decreases greatly due to the local damages. This paper investigates the remedial effects of two different retrofitting techniques, namely the application of steel casing and CFRP sheets, on the axial load carrying capacity of damaged cylindrical shells. For this purpose, a series of specimens, including the undamaged, damaged but non-retrofitted, and damaged-retrofitted samples, were tested experimentally and results were compared. Experiments showed that both adopted techniques were capable of improving the load-carrying behavior of damaged specimens. Following the laboratory tests, a numerical study was conducted on the effect of different influencing parameters by focusing on the strengthening technique with steel casing. The main purpose of these analyses was to determine the influence of different parameters and their appropriate value for maximum efficacy. The considered parameters included the diameter to thickness ratio, damage width to wall thickness ratio, damage thickness to wall thickness ratio, casing length to damage width ratio, casing thickness to wall thickness ratio, and damage angle around the circumference. Finally, a practical recommendation was provided on the selection of appropriate parameters for this strengthening technique.

Collapse behavior simulation of cylindrical steel shell under landslide impact

ANSYS/LS-DYNA dynamic analysis software was adopted to establish a model of a grid structure impacted by a landslide load, with the dynamic effects of impact loads and contact collision theory considered based on Hamilton’s principle. The case analysis in this study can provide guidance for anti-slump design in similar projects.

Practical approach to plastic collapse of conical shells under axial compression

Steel cylindrical shell structures such as silos and tanks are very sensitive to geometric imperfections and prone to a plastic instability failure known as elephant's foot (EF) buckling. This type of buckling arises under axial compression. The aim of this paper is to explore the plastic collapse response in conical shells with low semi-vertex angle values under compression. In a first step, the initial geometric imperfection shapes that dictate which plastic mechanisms arise were identified using finite element (FE) models. In a second step, a parametric study reported two plastic collapse mechanisms and showed that the elephant's foot plastic collapse mechanism is the most likely to appear in compressed conical shells with low d/t values, followed by the Yoshimura collapse mechanism, more common with larger d/t values. Finally, a practical model in which the parameters have been adjusted from numerical models has been derived for the elephant's foot plastic mechanism. This model provides the load-deformation behaviour of compressed conical shells at the post-collapse region. The load vs. end-shortening curves provided by the model have been validated through comparison with curves given by the FE models. The good agreement between the results proves the efficiency of the practical model to predict the collapse response of conical shells.

Reaction of Cylindrical 09G2S and 10KhSND Steel Shells with Longitudinal and Annular Welded Joints to Explosive Loading

Large explosion-proof chambers are manufactured using cylindrical shells made of sheet metal by rolling and welding with addition of longitudinal and circumferential seams. In this case, one should make a choice of steel with increased strength or ductility. In this regard, this work presents the results of a study of the reaction of such 09G2S and 10KhSND steel shells to dynamic loading.

Buckling Behavior of Sulfate-Corroded Thin-Walled Cylindrical Steel Shells Reinforced with CFRP

In this study, the buckling behavior of thin-walled cylindrical tanks exposed to sulfuric acid corrosion was investigated, and the buckling performance losses were recovered by reinforcing with Carbon fiber reinforced polymer (CFRP). Experiments were planned for three groups: Control samples without corrosion, full CFRP models and variable CFRP application group. The experiments were performed with 12 models of 800 × 400 × 0.45-mm dimensions. The prepared solutions were applied to the sealed test models as full and ½-filled and then exposed to sulfuric acid solution for 24 h, after which the experiments were performed. The mass losses were determined from the weights of the cylindrical samples, which were discharged after 24 h. After the corrosion, CFRP was applied to the cylinder, at ½ height of the cylinder and at 10 cm from its midpoint. The prepared model samples were placed in the test apparatus and sealed. In the experiments, vacuum was made using the vacuum pump, and data were recorded using the load cell. Deformations were measured by strain gauges and LVDT and transferred to the computer using a data collection device (datalogger). After data collection, vacuum-displacement plots were made. We aimed to recover a material that has undergone acid corrosion. The main goal of this work is to use the theoretical model, which is evaluated for limited geometrical ratios and for the perfect models, for the prediction of buckling behavior of sulfuric acid corroded thin-walled steel shells. We observed that the samples exposed to corrosion recovered 20–60% of their lost strength by CFRP application.