Nonlinear Finite Element Analysis of a Toroidal Shell With Ring-Stiffened Ribs

2010 ◽  
Author(s):  
Qing-Hai Du ◽  
Wei-Cheng Cui ◽  
Zheng-Quan Wan
Keyword(s):  
Finite Element ◽  
Cylindrical Shell ◽  
Circular Cylindrical Shell ◽  
Structural Characteristics ◽  
External Pressure ◽  
Nonlinear Finite Element ◽  
Toroidal Shell ◽  
Shells Of Revolution ◽  
Element Analysis ◽  
Stiffened Cylindrical Shell

The toroidal shell is a special type of shells of revolution, which is hardly solved by analytical method. To show the nonlinear structural characteristics of a circular toroidal shell with ring-stiffened ribs due to external pressure, both material nonlinear and geometric nonlinear Finite Element Analyses (FEA) have been presented in this paper, especially for the stability to the type of pressure hull. In the presented Finite Element Method (FEM), the elastic-plastic stress-strain relations have been adopted, and the initial deflection of toroidal shell created by manufacture was also taken into account. The analytic results eventually indicate that by nonlinear FEA such a new type of ring-stiffened circular toroidal shell could be used to a main pressure hull as the traditional ring-stiffened circular cylindrical shell, which could obtain kinds of performance in underwater engineering, such as better stability and more reserve buoyancy to the classical ring-stiffened cylindrical shell.

scholarly journals Study on the characteristics of pipe buckling strength under pure bending and external stress using nonlinear finite element analysis

2021 ◽  
Vol 12 (2) ◽  
pp. 110-116
Author(s):  
Hartono Yudo ◽  
Wilma Amiruddin ◽  
Ari Wibawa Budi Santosa ◽  
Ocid Mursid ◽  
Tri Admono
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Bending Moment ◽  
Nonlinear Finite Element Analysis ◽  
External Pressure ◽  
Diameter Ratio ◽  
Nonlinear Finite Element ◽  
Pure Bending ◽  
Element Analysis ◽  
Buckling Strength

Buckling and collapse are important failure modes for laying and operating conditions in a subsea position. The pipe will be subjected to various kinds of loads, i.e., bending moment, external pressure, and tension. Nonlinear finite element analysis was used to analyze the buckling strength of the pipe under pure bending and external pressure. The buckling of elastic and elasto-plastic materials was also studied in this work. The buckling strength due to external pressure had decreased and become constant on the long pipe when the length-to-diameter ratio (L/D) was increased. The non-dimensional parameter (β), which is proportionate to (D/t) (σy/E), is used to study the yielding influence on the buckling strength of pipe under combined bending and external pressure loading. The interaction curves of the buckling strength of pipe were obtained, with various the diameter-to-thickness ratio (D/t) under combination loads of external pressure and bending moment. For straight pipes L/D = 2.5 to 40, D = 1000 to 4000 mm, and D/t = 50 to 200 were set. The curved pipes D/t = 200, L/D =2.5 to 30 have been investigated by changing the radius of curvature-to-diameter ratio (R/D) from 50 to ∞, for each one. With decreasing R/D, the buckling strength under external pressure decreases slightly. This is in contrast to the bending of a curved pipe. When the value of R/D was decreased, the flexibility of the pipe was increased. However, the buckling strength of the pipe during bending was decreased due to the oval deformation at the cross-section.

Nonlinear Finite Element Analysis of Collapse Loads of Cylindrical Shells Subjected to Combined Thermal Loads and External Pressures

2007 ◽  
Author(s):  
Takuya Sato ◽  
Toshiyuki Hirosawa ◽  
Shunji Kataoka
Keyword(s):  
Finite Element ◽  
Cylindrical Shells ◽  
Design Procedure ◽  
External Pressure ◽  
Nonlinear Finite Element ◽  
Plastic Behavior ◽  
Thermal Loads ◽  
Collapse Load ◽  
Element Analysis ◽  
External Pressures

The inner tube of the double-tube reactors used in some chemical process units must be designed to resist buckling. When the inner tube is operated at a higher temperature and at a lower pressure and outer tube is operated at a lower temperature and at a higher pressure, the inner tube will be subjected to combined thermal loads and external pressure. ASME Code Sec. VIII Div. 1 provides a design procedure for shells, based on a B-chart, to ensure against buckling under external pressure, however, additional consideration should be made where plastic deformation may occur due to very large longitudinal thermal loads. In this study, nonlinear finite element analyses were performed to investigate the collapse of thick-walled cylindrical shells subjected to combined thermal loads and high external pressures. Two nonlinearities, a material nonlinearity (elastic-plastic behavior) and a geometric nonlinearity (large deformation), were considered in these analyses. The effects of initial imperfection in the shells (out-of-roundness) as well as of thermal loads were studied. The results showed that the longitudinal thermal loads reduce the plastic collapse load especially when the thermal loads are tensile. It was also shown that the loading sequence has a large effect on the collapse load especially when the thermal stress was larger.

Reduced-Order Nonlinear Modal Equations of Circular Cylindrical Shells Based on the Finite-Element Method

2004 ◽  
Author(s):  
Yukinori Kobayashi ◽  
Tomoaki Furukawa ◽  
Gen Yamada
Keyword(s):  
Finite Element ◽  
Circular Cylindrical Shell ◽  
Equations Of Motion ◽  
Cylindrical Shells ◽  
Nonlinear Finite Element ◽  
Element Analysis ◽  
Reduced Order ◽  
Finite Element Equation ◽  
Displacement Vectors ◽  
Circular Cylindrical Shells

This paper presents a procedure to derive reduced-order nonlinear modal equations of circular cylindrical shells. Modal analysis is applied to the nonlinear finite element equation by using base vectors obtained by the finite element analysis. Reduced-order modal equations are derived by transforming the equations of motion from the physical coordinates to the modal coordinates. Base vectors for the transformation consist of dominant linear eigenmodes and nonlinear displacement vectors derived approximately from the nonlinear finite element equation. Asymmetry of the deformation of the circular cylindrical shell with respect to its neutral surface is taken into consideration to determine the base vectors. Numerical results show good agreement with those presented in other papers.

The Effect of Nozzles and Nozzle Loadings on Shell Buckling

2015 ◽  
Author(s):  
Edward Clarke ◽  
Robert Frith
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Cylindrical Shell ◽  
Vessel Diameter ◽  
External Pressure ◽  
Element Analysis ◽  
Shell Buckling ◽  
Industry Practice ◽  
Overall Buckling ◽  
The Impact

This paper investigates the effect of nozzles and nozzle loadings on the overall buckling capacity of a vessel subject to external pressure designed to ASME VIII Div 1. ASME VIII Div 1 provides a well-established design-by-rule (DBR) approach for vessels subject to external pressure, but this takes no consideration for the presence of openings or nozzles. There are empirical rules regarding nozzle reinforcement for external pressure, but these do not directly consider the buckling capacity of the overall vessel. This paper therefore assesses the impact of nozzles on the buckling capacity of a cylindrical shell, where the nozzle is reinforced as per code requirements. The effect of reduced reinforcement is also analyzed. Subsequently the effect of nozzle loads is also assessed. Nozzles are loaded with ‘allowable’ loads, determined using finite element analysis in accordance with industry practice and code principles. The buckling capacities are assessed using ASME VIII Div 2 Part 5 methods, using a parametric study with over 500 models. Variables considered are vessel diameter, vessel length, nozzle diameter, and both integral and pad-reinforced nozzles are used.

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