Assessment of Overlapped Internal and External Volumetric Flaws in p-M Diagram

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Shinji Konosu ◽  
Hikaru Miyata
Keyword(s):  
Finite Element ◽  
Cross Section ◽  
Pressure Vessel ◽  
Effective Cross Section ◽  
Finite Element Analyses ◽  
Diagram Method ◽  
Reference Stress ◽  
Common Problems ◽  
Good Agreement

Assessment of overlapped internal and external volumetric flaws is one of the most common problems related to pressure vessel and piping components. Under the current fitness for service rules, such as those provided in ASME, BS, and so on, the procedures for the assessment of these flaws have not yet been defined. In this paper, a reference stress, incorporating the decrease in the effective cross section as a function of flaw depth and flaw angle in a cylinder, has been proposed in order to assess the flaws using the simple p-M (pressure-moment) diagram method. Numerous finite element analyses for a cylinder with overlapped internal and external flaws were conducted to verify the proposed procedure. There is good agreement among them.

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.

Reference Stress Based Assessment for Creep-Fatigue Life Under Multiaxial Condition

2014 ◽  
Author(s):  
Kenji Tokuda ◽  
Kimiaki Yoshida ◽  
Masataka Yatomi
Keyword(s):  
Fatigue Life ◽  
Creep Condition ◽  
Assessment Method ◽  
Life Assessment ◽  
Finite Element Analyses ◽  
Reference Stress ◽  
Creep Fatigue ◽  
Creep Fatigue Crack ◽  
Novel Model ◽  
Good Agreement

The reference stress method has been developed to assess the service life for many components under creep condition. However, in order to use the reference stress as a representative stress to assess the creep fatigue life, some modifications are needed. The σd approach based on reference stress, used in RCC-MR, is one of the most common method to assess creep fatigue crack incubation. The aim of this paper is to develop a novel model based on reference stress and the σd approach to estimate the life subjected to creep-fatigue interaction under multiaxial condition for defect free structures. Three kinds of circumferentially notched bar specimens were used in order to examine the creep-fatigue interaction under multiaxial conditions. Finite element analyses were conducted to develop a simplified life assessment method and to calculate the creep fatigue damage in the test specimens. The predicted creep fatigue lives are in good agreement with the experimental results using notched bar specimens of 316H stainless steel.

The Effect of Joint Flexibility on the Torsion of a Vehicle Body

1982 ◽  
Vol 196 (1) ◽  
pp. 191-197 ◽  
Author(s):  
P W Sharman
Keyword(s):  
Finite Element ◽  
Cross Section ◽  
Theoretical Estimate ◽  
Element Model ◽  
Vehicle Body ◽  
Finite Element Analyses ◽  
Joint Flexibility ◽  
Theoretical Predictions ◽  
Plane Frame ◽  
Beam Type

Experiments on thin fabricated box members in a tee joint configuration revealed deformations which could not be correlated with beam-type models, even when spring elements were introduced at the joint. The behaviour was also observed in finite element analyses of the joints. Part of the cab structure of a heavy goods vehicle which formed a plane frame with fabricated members of closed cross-section was tested in torsion and the stiffness compared with theoretical predictions. The application of classical beam and torsional theory gave a result which was approximately ten times the experimental value. A further theoretical estimate, which included the joint flexibility as predicted by a finite element model of the localized region at the joint, gave an improved result which was 26 per cent higher than the experimental value.

Using Isochronous Method to Calculate Creep Damage in Pressure Vessel Components: Part 2

2017 ◽  
Author(s):  
Chithranjan Nadarajah ◽  
Benjamin F. Hantz ◽  
Sujay Krishnamurthy
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Pressure Vessel ◽  
Closed Form Solution ◽  
Creep Damage ◽  
Form Solution ◽  
Creep Model ◽  
Stress Strain ◽  
Element Analysis ◽  
Good Agreement

This paper is Part 2 of two papers illustrating how isochronous stress strain curves can be used to calculate creep stresses and damage for pressure vessel components. Part 1 [1], illustrated the use of isochronous stress strain curves to obtain creep stresses and damages on two simple example problems which were solved using closed form solution. In Part 2, the isochronous method is implemented in finite element analysis to determine creep stresses and damages on pressure vessel components. Various different pressure vessel components are studied using this method and the results obtained using this method is compared time explicit Omega creep model. The results obtained from the isochronous method is found to be in good agreement with the time explicit Omega creep model.

Dynamic Analysis of Tapered Plates Based on Higher Order Beam Theory

2014 ◽  
Vol 919-921 ◽  
pp. 79-82
Author(s):  
S.M. Ibrahim ◽  
Y.A. Al-Salloum ◽  
H. Abbas
Keyword(s):  
Finite Element ◽  
Cross Section ◽  
Beam Theory ◽  
Longitudinal Axis ◽  
Vibration Modes ◽  
Bending Vibration ◽  
3D Finite Element ◽  
Different Types ◽  
Tapered Plates ◽  
Good Agreement

Modal solutions of plates with uniformly varying cross section using unified beam theory are presented. The results are given in the form of Euler-Bernoulli, Timoshenko and quasi 3D solutions. Numerical results for cantilever and CFCF supported rectangular planform plates are presented. Different types of modes, i.e. axial, bending and torsional modes are observed. The frequency values are in good agreement with 3D finite element results as well as published literature. Due to uniform taper in plate cross section, bending vibration modes become asymmetric along the longitudinal axis of the structure. Further, it can also be noticed that the vibration behavior of thick tapered plates is characterized by the appearance of significant number of axial and torsional modes at lower frequency values.

Homogenization of multi-turn coil with elliptic cross-section using complex permeability

2019 ◽  
Vol 38 (3) ◽  
pp. 999-1008 ◽  
Author(s):  
Shogo Fujita ◽  
Hajime Igarashi
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Finite Elements ◽  
Cross Section ◽  
Fe Analysis ◽  
Complex Permeability ◽  
Elliptic Cross Section ◽  
Content Type ◽  
Elliptic Cross ◽  
Good Agreement

Purpose The tensor complex permeability of a multi-turn coil with elliptic cross-section is analytically expressed. In field analysis, a multi-turn coil can be modeled by the uniform material that has the present tensor complex permeability. It is shown that the frequency characteristic of the present tensor complex permeability is in good agreement with that evaluated by finite element method applied to a unit cell of the multi-turn coil region. Design/methodology/approach The authors introduce a new method to evaluate the complex permeability of a multi-turn rectangular coil. To obtain the complex permeability of a rectangular coil in a closed form, it is approximated as an elliptic coil. Because the rectangular coil has different complex permeabilities in the vertical and horizontal directions, the complex permeability have to be defined in a tensor form. It suffices to discretize the coil region into rather coarse finite elements without considering the skin depth in contrast to the conventional finite element method. Findings The proposed method is shown to give the impedance of multi-turn coils which is in good agreement with results obtained by the conventional finite element (FE) analysis. By extending the proposed approach, the authors can easily perform 3D FE analysis without difficulty in discretization of the coil region with fairly fine finite elements. Moreover, they found that the approximation of rectangular coils as the elliptic coils is valid for analysis of quasi-static fields using this homogenization method. Originality/value The novelty of this study is in the approximation of the rectangular coils with elliptic coils, and the complex permeability for them is formulated here in a closed form. The proposed formula includes that for the round coils. Using the present method, the authors analyze the rectangular coils without fine discretization.

Design of a 33-Knot Aluminum Catamaran Ferry

2000 ◽  
Vol 37 (02) ◽  
pp. 88-99
Author(s):  
R. G. Latorre ◽  
P. D. Herrington
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
High Speed ◽  
Frame Structure ◽  
Test Results ◽  
Finite Element Analyses ◽  
The Finite Element Method ◽  
Floating Frame ◽  
Good Agreement ◽  
Panel Design

This paper presents the results of an investigation on the suitability of using hull panels with alternating fixed and floating frames for a 30–40 knot aluminum catamaran ferry. A prototype 4.6 m × 1.8 m bottom hull panel with alternating frames is analyzed numerically and physically tested. The corresponding finite-element analyses and test results are in good agreement. The results show that the floating frame hull panel design is a feasible structure for an aluminum catamaran. The floating frame structure was then used for a 33-knot, 250-passenger aluminum catamaran ferry designed to meet the ABS High Speed Craft rules. A midship section of the catamaran hull was analyzed using the finite-element method. Catamaran weight estimates, heave and pitch motions, and powering estimates are also provided. The results show that the alternating floating frame structure was within the ABS rules stress allowables.

SCALED BOUNDARY FINITE ELEMENT METHOD FOR SEMI-INFINITE RESERVOIR WITH UNIFORM CROSS SECTION

2012 ◽  
Vol 09 (01) ◽  
pp. 1240006 ◽  
Author(s):  
SHANGMING LI
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Cross Section ◽  
Uniform Cross Section ◽  
Vertical Ground ◽  
Part Modeling ◽  
Infinite Reservoir ◽  
Scaled Boundary Finite Element ◽  
Good Agreement ◽  
Element Method

A unified scaled boundary finite element method (SBFEM) in the frequency domain was proposed for a semi-infinite reservoir with uniform cross section subjected to horizontal and vertical ground excitations, and a methodology was presented to solve the unified SBFEM through decomposing the unified SBFEM into two parts; one part modeling the reservoir subjected to horizontal excitations and the other part modeling the whole reservoir subjected to vertical excitations. The accuracy of the unified SBFEM and its solving methodology was validated through analyzing numerical examples. The SBFEM solutions were in good agreement with analytical or other numerical method's solutions.

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