Investigation of Reduction in Buckling Capacity of Cylindrical Shells Under External Pressure Due to Partially Cut Ring Stiffeners

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Snehankush Chikode ◽  
Nilesh Raykar
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Cylindrical Shells ◽  
External Pressure ◽  
Geometrical Parameters ◽  
Section Shape ◽  
Clear Guideline ◽  
Section Viii ◽  
Special Circumstances ◽  
Division 2

Circumferential ring stiffeners are commonly used to improve the buckling strength of cylindrical shells. Under special circumstances, stiffener ring needs to be partially cut in order to avoid interference with vessel attachments or surrounding structures. No clear guideline is available in rule-based method to deal with such case. This paper investigates the extent of reduction in buckling capacity for a range of cylindrical shell geometries with stiffener rings having different cross sections and different extents of circumferential cut. Finite-element (FE)-based analysis as per ASME Section VIII, Division 2, Part 5 has been employed to determine the permissible external pressure in each of the cases. Effects of ring cross section and extent of circumferential cut of stiffening ring on the maximum permissible external pressure have been presented. A total of 63 combinations of shell-stiffening ring configurations of different L/D, D/t ratios, cross section shape, and extent of cut have been investigated. Geometrical parameters for these combinations under study are so chosen that normal working range in industries is covered. The results obtained provide guidelines to design shells with partially cut stiffening rings.

Limit Pressures of Cylindrical and Spherical Shells

2000 ◽  
Vol 123 (3) ◽  
pp. 288-292 ◽  
Author(s):  
Arturs Kalnins ◽  
Dean P. Updike
Keyword(s):  
Geometric Parameter ◽  
Cylindrical Shells ◽  
Length Effect ◽  
Spherical Shells ◽  
Simply Supported ◽  
Limit Pressure ◽  
Section Viii ◽  
Division 2

Tresca limit pressures for long cylindrical shells and complete spherical shells subjected to arbitrary pressure, and several approximations to the exact limit pressures for limited pressure ranges, are derived. The results are compared with those in Section III-Subsection NB and in Section VIII-Division 2 of the ASME B&PV Code. It is found that in Section VIII-Division 2 the formulas agree with the derived limit pressures and their approximations, but that in Section III-Subsection NB the formula for spherical shells is different from the derived approximation to the limit pressure. The length effect on the limit pressure is investigated for cylindrical shells with simply supported ends. A geometric parameter that expresses the length effect is determined. A formula and its limit of validity are derived for an assessment of the length effect on the limit pressures.

Estimation of Nusselt Number in Microchannels of Arbitrary Cross-Section With Constant Axial Heat Flux

2008 ◽  
Author(s):  
Ehsan Sadeghi ◽  
Majid Bahrami ◽  
Ned Djilali
Keyword(s):  
Heat Flux ◽  
Nusselt Number ◽  
Cross Section ◽  
Cross Sections ◽  
Numerical Solutions ◽  
Arbitrary Cross Section ◽  
Geometrical Parameters ◽  
Thermal Systems ◽  
Cross Sectional ◽  
Axial Heat

In many practical instances such as basic design, parametric study, and optimization analysis of thermal systems, it is often very convenient to have closed form relations to obtain the trends and a reasonable estimate of the Nusselt number. However, finding exact solutions for many practical singly-connected cross-sections, such as trapezoidal microchannels, is complex. In the present study, the square root of cross-sectional area is proposed as the characteristic length scale for Nusselt number. Using analytical solutions of rectangular, elliptical, and triangular ducts, a compact model for estimation of Nusselt number of fully-developed, laminar flow in microchannels of arbitrary cross-sections with “H1” boundary condition (constant axial wall heat flux with constant peripheral wall temperature) is developed. The proposed model is only a function of geometrical parameters of the cross-section, i.e., area, perimeter, and polar moment of inertia. The present model is verified against analytical and numerical solutions for a wide variety of cross-sections with a maximum difference on the order of 9%.

A Study of the Conservatism in ASME BPVC Section VIII Division 2 Opening Design for External Pressure

2019 ◽  
Author(s):  
Barry Millet ◽  
Kaveh Ebrahimi ◽  
James Lu ◽  
Kenneth Kirkpatrick ◽  
Bryan Mosher
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Pressure Vessel ◽  
External Pressure ◽  
The Other ◽  
Finite Element Analyses ◽  
Division 1 ◽  
Section Viii ◽  
Allowable Compressive Stress ◽  
Division 2

Abstract In the ASME Boiler and Pressure Vessel Code, nozzle reinforcement rules for nozzles attached to shells under external pressure differ from the rules for internal pressure. ASME BPVC Section I, Section VIII Division 1 and Section VIII Division 2 (Pre-2007 Edition) reinforcement rules for external pressure are less stringent than those for internal pressure. The reinforcement rules for external pressure published since the 2007 Edition of ASME BPVC Section VIII Division 2 are more stringent than those for internal pressure. The previous rule only required reinforcement for external pressure to be one-half of the reinforcement required for internal pressure. In the current BPVC Code the required reinforcement is inversely proportional to the allowable compressive stress for the shell under external pressure. Therefore as the allowable drops, the required reinforcement increases. Understandably, the rules for external pressure differ in these two Divisions, but the amount of required reinforcement can be significantly larger. This paper will examine the possible conservatism in the current Division 2 rules as compared to the other Divisions of the BPVC Code and the EN 13445-3. The paper will review the background of each method and provide finite element analyses of several selected nozzles and geometries.

Numerical Modelling of Metal Foams with Weaire-Phelan Cell

2013 ◽  
Vol 334-335 ◽  
pp. 122-126 ◽  
Author(s):  
Sid Ali Kaoua ◽  
Haddad Meriem ◽  
Dahmoun Djaffar ◽  
Azzaz Mohammed
Keyword(s):  
Finite Element ◽  
Cross Section ◽  
Cross Sections ◽  
Metal Foam ◽  
Metallic Foam ◽  
Geometrical Parameters ◽  
The Finite Element Method ◽  
Geometrical Characteristics ◽  
Structural Network ◽  
Regular Network

The mechanical properties of open-cell metal foam structures are investigated using the finite element method. The foam structure is modelled by a regular network of anisotropic Weaire-Phelan cells in which the strands are modelled as 3D finite element beams. We consider four types of strand cross sections: (i) circular, (ii) square, (iii) triangular and (iv) Plateau border shape. The numerical results obtained with our proposed mathematical model are checked against the experimental results obtained on real Nickel metallic foam and an excellent agreement is found. In addition, we conducted a parametric analysis to study the effect of some geometrical characteristics on the elasticity of the metal foam. Among these geometrical parameters, the shape, the dimensions of strand cross section, the inertia, the alignment of strands and the structural network irregularities are investigated, discussed and documented.

Cross Section Optimization of Plane Truss among Different Spans

2014 ◽  
Vol 679 ◽  
pp. 1-5 ◽  
Author(s):  
Sumayah Abdulsalam Mustafa ◽  
Mohd Zulham Affandi bin Mohd Zahid ◽  
Md.Hadli bin Abu Hassan
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Element Analysis ◽  
Cross Sectional ◽  
Analysis And Design ◽  
Cross Section Shape ◽  
Design Variables ◽  
Section Shape ◽  
Steel Sections ◽  
Research Show

Cross sectional areas optimization is to be implemented to study the influence of the cross section shape on the optimum truss weight. By the aid of analysis and design engines with advanced finite element analysis that is the steel design software STAAD. Four rolled steel sections (angle, tube, channel, and pipe) which are used in industrial roof trusses are applied for comparison. Many previous studies, use the areas of cross sections as design variables without highlight to the shape of cross section at the start of the process, consequently the result area will be adequate if the designer choose the effective shape than others. Results of this research show that the chosen cross section shape has a significant impact on the optimum truss weight for same geometry of truss type under the same circumstances of loading and supports.

Buckling of Externally Pressurised Prolate Ellipsoidal Domes

2006 ◽  
Author(s):  
P. Smith ◽  
J. Blachut
Keyword(s):  
Experimental Study ◽  
Test Procedure ◽  
External Pressure ◽  
Design Codes ◽  
Numerical Predictions ◽  
Current Design ◽  
Section Viii ◽  
Base Radius ◽  
Division 2 ◽  
Prolate Ellipsoidal

Details are given of a numerical and experimental study into buckling of steel ellipsoidal domes loaded by static external pressure. A range of geometries and thicknesses of domes is examined, as is the influence of different boundary conditions. Shells are examined on the basis of having the same mass. The main focus of the study is on prolate domes, i.e., those taller than a hemisphere of the same base radius. Numerical predictions are confirmed by pressurising six laboratory scale prolate domes to destruction. Details are given of the manufacture and test procedure for the domes. The adverse effects of variations in shape, and wall thickness are discussed, and FE predictions are made for geometrically imperfect domes. Correlation between the two sets of results is good. Numerical and experimentally obtained results are related to the current design codes: ASME Boiler & Pressure Vessel Code, Section VIII, Division 2 (described hereon as ASME VIII), PD5500, and ECCS recommendations [1–3], which at present make no provision for prolate domes. Suggestions are made for the possible inclusion of such domes into the standards.

Parametric Study of Reinforced Concrete Column Cross-Section for Strength and Ductility

2008 ◽  
Vol 400-402 ◽  
pp. 269-274 ◽  
Author(s):  
Naveed Anwar ◽  
Mohammad Qaasim
Keyword(s):  
Reinforced Concrete ◽  
Cross Section ◽  
Cross Sections ◽  
Strain Curve ◽  
Concrete Column ◽  
Loading Conditions ◽  
Reinforced Concrete Column ◽  
Section Shape ◽  
And Performance ◽  
Strength And Ductility

Several parameters and corresponding performance of reinforced concrete column cross-sections of different shapes (square, rectangular, circular, T-shape, I-shape, cross-shape, L-shape and C-shape) under various loading conditions have been studied in order to determine the suitable and optimum cross-sections for strength and ductility. In each cross-section shape, parameters include compressive strength of concrete (f’c), tensile strength of steel (fy), steel ratio (As/Ag), and angle of bending. In order to demonstrate the behavior and performance of the sections in terms of strength and ductility, CSISectionBuilder software was used to define the stress-strain curve for concrete and steel and then compute the moment-curvature relationship for each section. Considering different sections, the number of parameters in every section and various loading conditions, a total of around 1,800 sections were analyzed. The comparison procedures started within each section shape, and then across different sections in order to determine the most suitable cross-section for strength and ductility. Results of the study are deemed very useful in the system selection and preliminary design of important structures such as buildings with complicated geometry and high architectural demand including bridge piers and hydraulic structures.

Nonlinear Thermo-Mechanical Stability Analysis of Eccentrically Spiral Stiffened Sandwich Functionally Graded Cylindrical Shells Subjected to External Pressure

2019 ◽  
Vol 11 (05) ◽  
pp. 1950045 ◽  
Author(s):  
Vu Hoai Nam ◽  
Nguyen Thi Phuong ◽  
Cao Van Doan ◽  
Nguyen Thoi Trung
Keyword(s):  
Mechanical Stability ◽  
Thermal Environment ◽  
Cylindrical Shells ◽  
Geometrical Nonlinearity ◽  
External Pressure ◽  
Functionally Graded ◽  
Geometrical Parameters ◽  
Nonlinear Buckling ◽  
Circular Cylindrical Shells ◽  
The Galerkin Method

A new analytical approach to investigate the nonlinear buckling and postbuckling of the sandwich functionally graded circular cylindrical shells reinforced by ring and stringer or spiral stiffeners subjected to external pressure is presented in this paper. By employing the Donnell shell theory, the geometrical nonlinearity in Von Kármán sense and developed Lekhnitskii’s smeared stiffener technique, the governing equations of sandwich functionally graded circular cylindrical shells are derived. Resulting equations are solved by applying the Galerkin method to obtain the explicit expression of critical buckling external pressure load and postbuckling load–deflection curve. Effects of spiral stiffeners, thermal environment, external pressure, and geometrical parameters on nonlinear buckling behavior of sandwich functionally graded circular cylindrical shells are shown in numerical results.

Optimal Design of an Isotropic Porous-Cellular Cylindrical Shell

2006 ◽  
Author(s):  
Krzysztof Magnucki ◽  
Marek Malinowski ◽  
Jerzy Lewinski
Keyword(s):  
Cylindrical Shell ◽  
Cross Section ◽  
Optimization Problem ◽  
Cylindrical Shells ◽  
External Pressure ◽  
Total Potential Energy ◽  
Shell Wall ◽  
Combined Load ◽  
Porosity Parameter ◽  
Total Potential

The paper outlines the effects on an isotropic porous-cellular cylindrical shell when subjected to a combined load: of axial force and external pressure. Metal porosity varies across the thickness of the shell wall. A dimensionless porosity parameter is introduced to compensate for this. Nonlinear hypothesis of deformation of the flat cross section of the shell wall is formulated. A system of five differential equations is defined on the basis of the theorem of the minimum of total potential energy. This system of equations is then analytically solved with Galerkin’s method. Critical loads for a family of porous shells are numerically determined based on the analytical solution. The optimization problem considers two criteria: minimum of mass and maximum of critical load on the shell. Optimal porosity variability for the cylindrical shell is determined numerically. An optimal dimensionless porosity parameter is then defined. Moreover, a comparative analysis for selected cylindrical shells with the use of FEM is performed. Results of the calculation are shown in respective figures. Finally, the results of the investigation for porous cylindrical shells are compared to the corresponding results for isotropic homogeneous shells.

Eleocharis compressa × Eleocharis erythropoda, a new natural hybrid spike rush from Ontario

1994 ◽  
Vol 72 (6) ◽  
pp. 837-842 ◽  
Author(s):  
P. M. Catling
Keyword(s):  
Surface Roughness ◽  
Cross Section ◽  
Cross Sections ◽  
Roughness Length ◽  
Putative Hybrid ◽  
Natural Hybrid ◽  
Surface Roughness Length ◽  
Hybrid Plants ◽  
Section Shape ◽  
Spike Rush

Partially sterile plants from eastern Ontario are identified as Eleocharis compressa × Eleocharis erythropoda on the basis of intermediacy in perianth bristle length, tubercle shape, achene surface roughness, length of rhizome internodes, culm cross-section shape, and length of terminal lobes of scales. Both putative parents occurred with the hybrid plants. The hybrid plants had tardily deciduous scales and either bifid or trifid styles. They superficially resemble E. erythropoda most closely but differ markedly in their scaly rhizomes with shorter internodes 3.8 – 7 mm long. They are most readily distinguished from E. compressa by their elliptic or broadly rectangular culm cross sections and some perianth bristles exceeding 0.5 mm in length. This putative hybrid involves taxa in different subseries that would normally be regarded as too distantly related to permit hybridization. Key words: Eleocharis compressa, Eleocharis erythropoda, Cyperaceae, hybrid, taxonomy, classification.

Sign in / Sign up

Export Citation Format

Share Document