Steel Cylindrical Shells Research Articles

Numerical and Experimental Investigation of SS304L Cylindrical Shell with Cutout Under Uniaxial Cyclic Loading

This study examined the behavior of steel cylindrical shells under strain-controlled loading and axial cyclic loading. Experimental tests were carried out by an INSTRON 8802 servo-hydraulic. Under strain-controlled loading, the softening hysteresis curve is observed in shells. Because of buckling made in the compression area, the softening is intensified. Moreover, the effect of cutout on the behavior of hysteresis curves of steel cylindrical shells was also examined under this type of loading. The results show that cutout accelerates the softening behavior in steel cylindrical shells. Numerical analysis was performed by ABAQUS using hardening models. The accuracy of these models was compared with experimental results. Linear kinematic hardening model cannot simulate the softening behavior of the shell, but the model of nonlinear isotropic and kinematic hardening can simulate the softening behavior of the shell well. The residual plastic strain is obtained close to the experimental results with this model.

Student experiment for measure of target strength

The target strength is a measurement of the reflection coefficient of a sonar target. Its value and feature is very important to detection and identification in active sonar, especially for fish by fishery acoustic students. A steel cylindrical shell is used as the target, whose outer diameter 194 mm, inner diameter 184 mm, length 500 mm, and both end closed covers with thickness 4 mm. A broadband transducer is selected to directionally project sound wave and a hydrophone receives the reflection wave from the target. The transducer and receiver are located at 5 m and 4 m from the target with the same depth 5 m in the water. When single frequency pulses are transmitted with signal interval frequency 50 Hz, the target strength is calculated by amplitude ratio of target echo and incidence wave at different frequencies. The result is compared with theoretical value for an infinite elastic cylindrical shell and finite length elastic cylindrical shell. This experiment will give a strategic guidance to understand what target strength is, how to understand it, and why we need it. [Work supported by National Natural Science Foundation of China (Grant No. 41374147).]

05.16: Stability behavior of graded dented cylindrical steel shells under the action of combined external and axial pressure

ABSTRACTThin‐walled cylindrical steel shells such as silos, tanks and other containers are used in various applications of engineering. For economic reasons, large fluid storage steel tanks are made with varying thickness in height. Cylindrical steel shells with stepwise variable wall thickness are the most prevalent structural components in petrochemical and oil industry. However, during the construction procedure and service life, these reservoirs may be exposed to some geometrical imperfections in the form of dents. These shells are subjected to peripheral pressure loading and when a large liquid storage is discharged, an internal suction will be applied to its wall and head, causing external pressure on the wall and axial compression on the head. These structures are prone to fail by buckling under external pressure and axial compression. Previous studies show that the stability behavior of cylindrical shells under pressure load is strongly dependent on the nature and magnitude of the imperfections. Despite many studies on the buckling behavior of thin‐walled cylindrical steel shells of constant thickness, so far only a few investigations have been undertaken to examine instability behavior of these structures with thickness variation under the action of combined external pressure and axial compression, considering the dent imperfections. In this study, the effects of vertical and horizontal dents on the buckling and post‐buckling behavior of dented graded cylindrical steel shells with two and three layers under the action of a combination of peripheral and axial pressure are investigated. The models are designed in practical dimensions, with some horizontal and vertical dents in different positions. In the present study, non‐linear buckling and post‐buckling solutions of thin‐walled cylindrical steel shell with varying thickness are obtained by using ABAQUS, which is a general‐purpose finite element program designed specifically for advanced structural analysis.

Empirical equations to estimate non-linear collapse of medium-length cylindrical shells with circular cutouts

This paper examines the load bearing capacity of medium-length steel cylindrical shells with a circular cutout under the action of axial compression. Numerical simulations were performed for a radius-to-thickness ratio (R/t) ranging from 100 to 500, and an imperfection parameter (α) of between 1 and 4. Structural steel and the behavior of perfect plastic material were considered within the scope of the study. The investigation includes the influence of the cutout size and number, radius-to-thickness ratio. The paper also contains a comparison between theoretical predictions, ABAQUS® FE results and experimental data for axially compressed cylinders. A reasonable correlation was obtained between numerical predictions and experimental tests. Details relating to the experimental procedure and FE model are provided. A parametric study was conducted to propose empirical equations, estimating the limit load of cylindrical shells as a function of geometry (R/t, α and cutout number) and material properties (E, v and σy). Empirical formulas were produced, fitting a surface plot using the Least Square method, for both the perfect shell structure (reference shell load) and the limit load reduction factor (ϕ). All variables in the empirical formula were normalized. A stochastic error analysis was used as a tool to measure how the results of proposed equations approach the FE predictions. Finally, based on experimental and numerical results, formulas are presented to calculate the limit load of medium-length shells with and without circular cutouts having a discrepancy not exceeding ±10% regarding error analysis.

Effect of tempering temperature on expansion and fracture mechanism of 40CrMnSiB steel cylinder shell

The study on the fracture mechanism of steel cylindrical shells under different heat treatment conditions was helpful to understand the dynamic response of metal shell under high strain-rate loading. Therefore, the effect of tempering temperature on the expansion and fracture of metal cylinder shells and the regular pattern of fragmentation mass, size distribution fragments was analyzed by using a high speed photography technique and the recovery experiment of static explosion in well. The results revealed that fracture behavior changed from tensile-shear fracture to shear fracture occurring in a 40CrMnSiB steel cylinder shell internally filled with CL-20 based high explosives with the increasing of tempering temperature, and the different tempering temperature conditions on shell have a marked impact on behavior of fragments mass and size distribution. The radial expansion displacement of 40CrMnSiB steel cylinder shells tempered at 500 °C and 600 °C was increased by 39.43% and 21.46%, respectively, compared with that of the shell tempered at 350 °C. Besides, the fragmentation degree of 40CrMnSiB steel shell decreases and the total number of fragments reduces gradually with increasing tempering temperature, but the fragments numbers which mass was more than 1.0g increase from 105 to 159 gradually, which was increased by 77.4%, which could be helpful to improve the understanding of influence of material properties on the deformation, expansion and fragmentation of warhead, also could provide a constructive guidance for selecting heat treatment technology of warhead material.

Three-dimensional multiscale simulation on fracture behaviors of cylindrical shells subjected to inner pressure and surface laser irradiation

Multiscale numerical simulation has important advantages in analyzing the partial fracture problems of shell structures subjected to the coupled thermo-mechanical effects. The multiscale time–space model of a cylindrical shell subjected to inner pressure and surface laser irradiation by coupling the three-dimensional discrete element method (DEM) and the shell finite element method was established. By simulating the crack-bifurcation extending behaviors of the aluminum alloy cylindrical shell and comparing the fracture behaviors and the calculation time by the multiscale time–space model with those by the multiscale space model of the overlapping element/node, the multiscale time–space model not only satisfies the requirement of simulation accuracy, but also enhances the calculation efficiency greatly under the condition of stable simulation. The multiscale time–space model was applied to the simulations in the fracture behaviors of the aluminum alloy and the 30CrMnSiA steel cylindrical shells under four modes of action. The failure modes of cylindrical shells under different modes of action are directly related to the radius of the laser spot, the power density of the laser, and the extensibility of material. At the same time, the damage evolution process of the cylindrical shells under four modes of action was analyzed through the crack ratio in the mesoscopic DEM elements. The multiscale time–space model provides a reliable analytical way to the complex partial fracture mechanical problems of large-scale cylindrical shell structures subjected to inner pressure and surface laser irradiation. PACS. 02.70.Dh, 02.70.Ns, 42.62.Cf, 46.50.+a, 61.82.Bg, 62.20.mm, 07.05.Tp, 83.60.Uv

Structural integrity of a wind loaded cylindrical steel shell structure

The structural integrity and life assessment can be considered as a mandatory request in the civil engineering designing and manufacturing process.The paper is presenting the procedure for determination of crack acceptability based on fracture toughness with failure assessment methods (FAD-1 and FAD-2) which is applied to a cylindrical steel shell structure with welded joints which is having the wind as a main load.The assessment is using BS7910/2013. Thus were assessed common types of flaws met at steel shell cylindrical structure elements using failure assessment diagrams – level 1 – FAD-1. The results are presenting the acceptability level for each type of flaw with comparative graphs, determining also the critical dimension of the flaw.For each flaw was calculated the failure assessment diagram (FAD-2). Different comparisons between group of flaws were done, revealing the critical crack like flaw. Also the critical value of flaw dimensions were calculated for each flaw type. The methodology establishes clear rules for assessment of structural elements with cracks, determining the initial flaws, assessed flaws and critical values of the cracks.Based on the detailed procedures described in the paper, on conclusions to the assessment done on each type of flaw, the assessment methods can be applied very easy in current design practice with different material characteristics

Field Study and Evaluation of Buckling Behaviour of Steel Tanks under Geometric Imperfections

Shells are among the most frequent structural components which are used in construction and industrial projects. Shell structures are composed of shell bearing elements and mainly used in oil and gas tanks, offshore marine platforms, silos, funnels, cooling towers, ship and aircraft body, etc. Despite the frequent use of steel cylindrical shells, their construction and assembling process has caused main problems. In these structures, there is no possibility for the integrated construction due to their large shell extent and they are built using a number of welded curved panel parts; hence, some geometrical imperfections emerge. Most of these imperfections are caused by the process of welding, transportation, inappropriate rolling, as well as installation and implementation problems. These imperfections have a direct impact on the structural behavior of shells during the buckling and external compressive load. Since in most shell tanks during operation, there is high possibility for the suction (vacuum) state, compressive forces in their thin wall cause buckling and failure. In this research, the imperfections made in steel cylindrical tanks being constructed in one of the refinery site are introduced and evaluated using a field study. Relying on the statistical inference, they are classified and then, by studying the effective factors and origin in their generation, the common imperfections are identified. Later, the impact of common imperfections on the buckling behavior is experimentally evaluated under uniform external pressure. Then, nonlinear numerical analysis of the test specimens is performed. Finally, experimental results, finite element and analytical relations are compared.

К ВОПРОСУ ОБ УСТОЙЧИВОСТИ МЕТАЛЛИЧЕСКОЙ ЦИЛИНДРИЧЕСКОЙ ОБОЛОЧКИ ИЗ СБОРНЫХ ЭЛЕМЕНТОВ

К ВОПРОСУ ОБ УСТОЙЧИВОСТИ МЕТАЛЛИЧЕСКОЙ ЦИЛИНДРИЧЕСКОЙ ОБОЛОЧКИ ИЗ СБОРНЫХ ЭЛЕМЕНТОВ

Experimental and Numerical Investigation of Elephant Foot Buckling and Retrofitting of Cylindrical Shells by FRP

AbstractLarge and small cylindrical shells have long been used as tanks and silos to store materials such as oil and its derivatives. The radius-to-thickness ratio of these shells is 500∶2000; as a result, buckling collapse of these thin-walled structures is of major concern for designers. The present study examined inelastic buckling behavior of cylindrical shells near the base, known as elephant foot buckling. This form of buckling occurs under high internal pressure exerted simultaneously with axial compression. The buckling of cylindrical shells subjected to combined axial loads and internal pressure was experimentally studied and tested and a new method of strengthening steel cylindrical shells using fiber-reinforced polymer (FRP) composite materials is presented. The proposed method was studied by numerical methods using a nonlinear algorithm, and the results were evaluated for resistance to buckling of cylindrical shells. The results provide effective and useful information for use in retrofitting ...

Buckling behavior of axially compressed cylindrical shells: Comparison of theoretical and experimental data

This paper examines the buckling of short mild steel cylindrical shells subjected to axial compression. Cylinders were joined together using Metal Inert Gas (MIG) welding process with radius-to-thickness ratio, R/t, ranging from 25 to 100. The axial length of the specimens were assumed to be 111.8mm. Past result on axially compressed cylinder machined using Computer Numerically Controlled (CNC) machining is compared with fresh experimental results on MIG manufactured axially compressed cylinder. The paper contains a comparison between theoretical predictions, ABAQUS FE results and experimental data for axially compressed cylinder. Details about material testing and collapse test are provided. As compared to the CNC machined specimen, results indicates that there is a good agreement between theoretical prediction, ABAQUS FE results and experimental data for MIG manufactured cylinder with radius-to-thickness ratio, R/t ranging from 25 to 100, with difference ranging between −7% and +2%.

Influence of Door Opening and Collar Stiffener on the Buckling Capacity of Cylindrical Wind Tower

This study analyzes the buckling capacity of steel cylindrical shells that exhibit the lower segment of 2MW, 3MW and 5MW wind towers. Four cases of steel cylindrical shells are modeled: shell with neither door opening nor collar stiffener; shell with door opening but without collar stiffener; shell without door opening but with collar stiffener; and shell with both door opening and collar stiffener. Buckling capacity is analyzed numerically using finite element analysis and parametrically using Eurocode 3: Design of Steel Structures and Guideline for the Certification of Offshore Wind Turbines. In finite element analysis, buckling capacity is calculated linearly using eigenvalue analysis and non-linearly using static Riks. Results show that steel cylindrical shell with discontinuity or modification in geometry such as door opening and collar stiffener indicates local buckling. Furthermore, a 35% decline of critical (bifurcation) buckling capacity is observed when linear buckling analysis is compared to nonlinear buckling analysis. Linear buckling analysis provides a good starting point in solving buckling collapse load, but non-linear analysis delivers a more accurate assessment due to the consideration of influences in material and geometrical nonlinearity.

Pyroeffects on magneto-electro-elastic sensor bonded on mild steel cylindrical shell

Magneto-electro-elastic (MEE) materials under thermal environment exhibits pyroelectric and pyromagnetic coefficients resulting in pyroeffects such as pyroelectric and pyromagnetic. The pyroeffects on the behavior of multiphase MEE sensor bonded on top surface of a mild steel cylindrical shell under thermal environment is presented in this paper. The study aims to investigate how samples having different volume fractions of the multiphase MEE sensor behave due to pyroeffects using semi-analytical finite element method. This is studied at an optimal location on a mild steel cylindrical shell, where the maximum electric and magnetic potentials are induced due to these pyroeffects under different boundary conditions. It is assumed that sensor and shell is perfectively bonded to each other. The maximum pyroeffects on electric and magnetic potentials are observed when volume fraction is vf = 0.2. Additionally, the boundary conditions significantly influence the pyroeffects on electric and magnetic potentials.

Numerical and experimental study on buckling and postbuckling behavior of cracked cylindrical shells

The effect of crack on load-bearing capacity and buckling behavior of cylindrical shells is an essential consideration in their design. In this paper, experimental and numerical buckling analysis of steel cylindrical shells of various lengths and diameters with cracks have been studied using the finite element method, and the effect of crack position, crack orientation and the crack length-to-cylindrical shell perimeter (λ = a/(2πr)) and shell length-to-diameter (L/D) ratios on the buckling and post-buckling behavior of cylindrical shells has been investigated. For several specimens, buckling test was performed using an INSTRON 8802 servo hydraulic machine, and the results of experimental tests were compared to numerical results. A very good correlation was observed between numerical simulation and experimental results. Finally, based on the experimental and numerical results, sensitivity of the buckling load to the shell length, crack length and orientation has also been investigated.

Numerical methods for the design of cylindrical steel shells with unreinforced or reinforced cutouts

The effectiveness of the numerical methods GMNIA and MNA/LBA proposed in EN1993-1.6 for the design of steel shells is studied for cylindrical steel shells with an unreinforced or reinforced rectangular cutout chamfered elliptically at the four ends and for the corresponding shells without cutout. Moreover, another design method proposed in the literature and denoted here as MNA/GNA, which is based on a modified slenderness, is also evaluated. GMNIA is considered as the most reliable analysis type, provided that a judicious choice of shape and amplitude of initial imperfections is made. Thus, GMNIA results are used as basis for comparison, except for shells without cutout where the EN1993-1.6 normative strengths could serve the same purpose as well. For shells without cutout it is found that the modified slenderness gives similar results to the corresponding results of the conventional slenderness definition. In the case of unreinforced cutout the modified slenderness gives better results, thus the use of MNA/GNA is recommended. However, in the case of reinforced cutout the GMNIA results are approximated better by employing the conventional slenderness, thus MNA/LBA is more appropriate.

Predicting the buckling Capacity of Steel Cylindrical Shells with Rectangular Stringers under Axial Loading by using Artificial Neural Networks

A parametric study was carried out in order to investigate the buckling capacity of the vertically stiffened cylindrical shells. To this end ANSYS software was used. Cylindrical steel shells with different yield stresses, diameter-to-thickness ratios (D/t) and number of stiffeners were modeled and their buckling capacities were calculated by displacement control nonlinear static analysis. Radial basis function (RBF) neural networks were used to predict the buckling capacity of shells. Herein 70 percent of the results of numerical analyses were used to train the neural network and the remainders were used to test and validate the results of neural networks. Results of this study showed that RBF neural networks are useful tools to predict the buckling capacity of vertically stiffened cylindrical shells. It was also shown that buckling capacities of stiffened shells exponentially vary by distance of adjacent stiffeners (unstiffened length).

Deformation- and temperature-related processes that occur upon the collapse of a thick cylindrical shell made of steel 20

An experiment has been performed on the collapse of a thick steel cylindrical shell into a continuous cylinder under the action of a sliding detonation wave. The process of the collapse has been recorded via X-ray photography, and it has been found that the time of collapse in one section is equal to 30 μs. The average degree of deformation is 77% and the rate of deformation is 104 s−1. The structure of steel 20 in the transverse section of the cylinder consists of three zones. In the outer zone, the initial ferrite-pearlite structure changes under the effect of compressive shock wave and localized shears. The shock wave leads to the formation of a high-pressure ɛ phase and twins. Upon the subsequent inertial collapse of the shell, substantial shear deformations arise in the surface layer, which are localized in directions located at angles of 60° to the cylindrical surface. The structure of the middle zone changes under the action of severe plastic deformation, which occurs predominantly in the radial direction. The deformation leads to the appearance of an internal pressure and to an increase in the temperature. As a result of the action of three factors (pressure, temperature, and deformation), the temperature of the formation of austenite decreases by several hundred kelvins. In the free ferrite, an α → γ transformation occurs and quenching takes place following a subsequent sharp decrease in pressure (barothermic quenching). The pearlitic regions suffer plastic deformation. The microhardness of the steel with this structure is equal to the microhardness of quenched steel. The structure of the third, i.e., central, zone, changes under the action of a significant increase in temperature caused by the further increase in the degree of deformation. The complete transformation of ferrite into austenite occurs at the center of this zone, which means that the temperature in this zone reaches 850–900°C or greater. The microhardness decreases to values typical of annealed steel.

Ultimate Flexural Strength of Cylindrical Steel Shell for Wind Tower

In this study, an experimental study was performed to evaluate the concrete breakout strength of cast-in-place(CIP) anchors in cracked concrete under static shear loading. The CIP anchors involved in this study were 30mm in diameter with an edge distance of 150mm and an embedment length of 240mm. The experiment was carried out for two specimens in uncracked concrete and three specimens in cracked concrete orthogonal and parallel to the direction of shear loading, respectively. Compared to the uncracked concrete specimen, cracked specimen orthogonal to the direction of shear loading showed no reduction in the concrete breakout strength and that parallel to the load direction about 91% strength which corresponds to 84% of uncracked concrete strength defined in ACI 318-11. Therefore, the experimental results showed smaller decrease in the shear resistance of CIP anchors in cracked concrete than that specified in ACI code which account for 71% strength of uncracked concrete in cracked concrete.

Ultimate Flexural Strength of Cylindrical Steel Shell for Wind Tower

풍력발전 타워용 원형단면 강재 쉘에 대하여 재료 및 기하학적 비선형 유한요소법으로 극한휨강도 해석을 수행하였다. 쉘의 기하학적 초기변형, 반경 대 두께비, 적용 강종 등이 극한휨강도에 미치는 영향을 분석하였으며, Eurocode 3와 AISI 설계기준에 의한 설계휨강도와 유한요소해석으로 구한 극한휨강도를 비교하였다. 비선형 FE 해석에는 DNV-RP-C202에 제시된 쉘의 좌굴모드와 유로코드에 규정된 진원도 허용오차 및 용접에 의한 변형을 기하학적 초기 결함으로 고려하였다. 원통형 쉘의 반경 대 두께비는 60~210 범위를 고려하였으며 SM520과 HSB800 강재로 제작된 것으로 가정하였다. Ultimate flexural buckling strength of cylindrical steel shells for the wind turbine tower structure was investigated by applying the geometrically and materially nonlinear finite element method. The effects of initial imperfection, radius to thickness ratio, and type of steel on the ultimate flexural strength of cylindrical shell were analyzed. The flexural strengths of cylindrical shells obtained by FEA were compared with design flexural strengths specified in Eurocode 3 and AISI. The shell buckling modes recommended in DNV-RP-C202 and the out-of-roundness tolerance and welding induced imperfections specified in Eurocode 3 were used in the nonlinear FE analysis as initial geometrical imperfections. The radius to thickness ratios of cylindrical shell in the range of 60 to 210 were considered and shells are assumed to be made of SM520 or HSB800 steel.

Influence of Cutout Position on Buckling of Large-Scale Thin-Walled Cylindrical Shell of Desulphurizing Tower with Welding Induced Imperfection under Wind Loading

Not only the geometrical imperfection induced by welding but also cutouts will influence the buckling of large-scale thin-walled steel cylindrical shell under wind loading. Based on the practical cylindrical shells of a desulphurizing absorption tower, in consideration of the correlation between welding induced imperfection and circular cutouts, the influence of cutout position on buckling of cylinder under wind loading is investigated by nonlinear finite element method. The results indicate that the buckling capacity varies slightly when the cutout position moves along meridional direction in the neighboring region of welding imperfection. The buckling capacity varies significantly when the cutout position moves circumferentially as the cutout is located in the welding imperfection. The buckling capacity reaches the minimum value as the cutout is located in the buckle center of cylindrical shells without cutout.