Comparison Between Analytical and Finite Element Calculation for Pressurized Container

2014 ◽  
Author(s):  
Otto Theodor Iancu ◽  
Frank Otremba ◽  
Christian Sklorz
Keyword(s):  
Finite Element ◽  
Plastic Material ◽  
Numerical Procedure ◽  
Material Model ◽  
Pressure Vessels ◽  
Wall Material ◽  
Stress Deviator ◽  
Plastic Collapse ◽  
Collapse Load ◽  
Element Analysis

The prediction of the plastic collapse load of cylindrical pressure vessels is very often made by using expensive Finite Element Computations. The calculation of the collapse load requires an elastic-plastic material model and the consideration of non-linear geometry effects. The plastic collapse load causes overalls structural instability and cannot be determined directly from a finite element analysis. The ASME (2007) code recommends that the collapse load should be the load for which the numerical solution does not converge. This load can be only determined approximately if a expensive nonlinear analysis consisting of a very large number of sub steps is done. The last load sub step leading to a convergent solution will be taken as the critical load for the structure. In the instability regime no standard finite element solution can be found because of the lack of convergence of the numerical procedure. Other methods for the calculation of the allowable pressure proposed by the ASME code are the elastic stress analysis and the limit load analysis. In the present paper the plastic collapse load for a cylindrical pressure vessel is determined by an analytical method based on a linear elastic perfectly plastic material model. When plasticity occurs the material is considered as incompressible and the tensor of plastic strains is parallel to the stress deviator tensor. In that case the finite stress-strain relationships of Henkel can be used for calculating the pressure for which plastic flow occurs at the inside of the vessel wall or in the case of full plasticity in the wall. The analytical results are fully confirmed by finite element predictions both for axisymmetric and high costs three dimensional models. The analytical model can be used for fast predictions of the allowable load for the design of a large variety of pressure vessels under safety considerations. The accuracy of the predicted collapse load largely depends on the quality of the temperature dependent wall material data used both in the analytical and numerical calculations.

Determination of the Plastic Collapse Load for Wire-Wound Pressure Vessels

2009 ◽  
Author(s):  
J. M. Alegre ◽  
P. M. Bravo ◽  
I. I. Cuesta
Keyword(s):  
Plastic Material ◽  
Continuous Process ◽  
Circumferential Stress ◽  
Numerical Procedure ◽  
Pressure Vessels ◽  
Plastic Collapse ◽  
Layer By Layer ◽  
Collapse Load ◽  
Wide Range ◽  
The Wire

This paper is focused on determining the plastic collapse load of vessels which consist of an inner cylinder prestressed by a surrounding winding. This winding consists of a wire helically wound edge-to-edge in pretension in a number of layers around the outside of the inner cylinder. As a consequence, compression stresses are introduced in the cylinder, and the fatigue life of the vessel can be greatly increased. The ASME code, Section VIII - Division 3, provides the analytical equations for the stress calculation in wire-wound vessels under linear-elastic conditions (ASME, 2007). However, to obtain the plastic collapse load of the vessel, finite element method should be used. In this way, the main aim of this paper is to present a numerical procedure for the FE simulation of wire-wound vessels. For this simulation, it must be taken into account that the wire winding is a continuous process where every new layer is coiled around all previous deformed layers. Hence, a layer-by-layer numerical procedure which takes into account this continuous process during winding has been developed. Some examples are given to demonstrate the applicability of the procedure. Once the numerical procedure was validated, it was used to obtain (i) the maximum circumferential stress after winding, (ii) the initial plastic load, and (iii) the plastic collapse load. To obtain the plastic collapse load, an elastic perfectly-plastic material behaviour has been considered. Finally, the numerical results obtained for the plastic collapse load were obtained as a function of several ratios over a wide range, which take into account the cylinder thickness, the wire-wound thickness, the wire-wound pretension and the yield limit of the material.

Elastic and elastic-plastic finite element analysis of hollow tubes with axisymmetric internal projections under combined axial and pressure loading

2001 ◽  
Vol 36 (4) ◽  
pp. 373-390 ◽  
Author(s):  
S. J Hardy ◽  
M. K Pipelzadeh ◽  
A. R Gowhari-Anaraki
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Internal Pressure ◽  
Plastic Material ◽  
Axial Loading ◽  
Material Model ◽  
Pressure Loading ◽  
Element Analysis ◽  
Elastic Plastic ◽  
Applied Loading

This paper discusses the behaviour of hollow tubes with axisymmetric internal projections subjected to combined axial and internal pressure loading. Predictions from an extensive elastic and elastic-plastic finite element analysis are presented for a typical geometry and a range of loading combinations, using a simplified bilinear elastic-perfectly plastic material model. The axial loading case, previously analysed, is extended to cover the additional effect of internal pressure. All the predicted stress and strain data are found to depend on the applied loading conditions. The results are normalized with respect to material properties and can therefore be applied to geometrically similar components made from other materials, which can be represented by the same material models.

A Practical Analysis Framework for Assessment of Printed Circuit Heat Exchangers in High Temperature Nuclear Service

2021 ◽  
Author(s):  
Avinash Shaw ◽  
Heramb Mahajan ◽  
Tasnim Hassan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
High Temperature ◽  
Heat Exchangers ◽  
Plastic Material ◽  
Material Model ◽  
Analysis Framework ◽  
Element Analysis ◽  
Printed Circuit ◽  
Analysis Technique

Abstract Printed Circuit Heat Exchangers (PCHEs) have high thermal efficiency because of the numerous minuscule channels. These minuscule channels result in a high thermal exchange area per unit volume, making PCHE a top contender for an intermediate heat exchanger in high-temperature reactors. Thousands of minuscule channels make finite element analysis of the PCHE computationally infeasible. A two-dimensional analysis is usually performed for the PCHE core, which cannot simulate the local channel level responses reasonably because of the absence of global constraint influence. At present, there is no analysis technique available in the ASME Code or literature that is computationally efficient and suitable for engineers to estimate PCHE local responses. A novel but practical two-step analysis framework is proposed for performing PCHE analysis. In the first step, the channeled core is replaced by orthotropic solids with similar stiffness to simulate the global thermomechanical elastic responses of the PCHE. In the second step, local submodel analysis with detailed channel geometry and loading is performed using the elastic-perfectly plastic material model. The proposed two-step analysis technique provides a unique capability to estimate the channel corner responses to be used for PCHE performance assessment. This study first developed a methodology for calculating the elastic orthotropic properties of the PCHE core. Next, the two-step analysis is performed for a realistic size PCHE core, and different issues observed in the results are scrutinized and resolved. Finally, a practical finite element analysis framework for PCHEs in high-temperature nuclear service is recommended.

NONLINEAR FINITE ELEMENT ANALYSIS OF FRP STRENGTHENED RC BEAMS

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Prabin Pathak ◽  
Y. X. Zhang
Keyword(s):  
Finite Element ◽  
Plastic Material ◽  
Experimental Studies ◽  
Material Model ◽  
Element Model ◽  
Steel Reinforcement ◽  
Elastic Model ◽  
Fe Model ◽  
Rc Beams ◽  
Element Analysis

A simple, accurate and efficient finite element model is developed in ANSYS for numerical modelling of the nonlinear structural behavior of FRP strengthened RC beams under static loading in this paper. Geometric nonlinearity and material non-linear properties of concrete and steel rebar are accounted for this model. Concrete and steel reinforcement are modelled using Solid 65 element and Link 180 element, and FRP and adhesive are modelled using Shell 181element and Solid 45 element. Concrete is modelled using Nitereka and Neal’s model for compression, and isotropic and linear elastic model before cracking with strength gradually reducing to zero after cracking for tension. For steel reinforcement, the elastic perfectly plastic material model is used. FRPs are assumed to be linearly elastic until rupture and epoxy is assumed to be linearly elastic. The new FE model is validated by comparing the computed results with those obtained from experimental studies.

Study on Plastic Collapse Load of Steel Elliptical Heads Under Internal Pressure

2013 ◽  
Author(s):  
Liang Sun ◽  
Guide Deng ◽  
Jiufeng Zhao
Keyword(s):  
Internal Pressure ◽  
Major Axis ◽  
Pressure Vessels ◽  
Outer Diameter ◽  
Maximum Relative Error ◽  
Plastic Collapse ◽  
Collapse Load ◽  
Element Analysis ◽  
Integrity Assessment ◽  
Perfectly Plastic

A general formula for plastic collapse load of elliptical heads under internal pressure is useful in plastic collapse design and integrity assessment of pressure vessels. Plastic collapse load of steel elliptical heads with different shapes and thickness was computed by finite element analysis using elastic-perfectly plastic constitutive model, and a formula with maximum relative error less than 6% was derived from the numerical results. The formula is a function of the yield strength of materials, the ratio of major axis Di to minor axis 2hi and that of outer diameter Do to inner diameter Di, and is applicable to steel elliptical heads with Di/2hi within 1–2.6 and Do/Di within 1.001–1.300.

Fitness for Service Assessment on Local Metal Loss Near a Discontinuity Using Elastic-Plastic Stress Analysis

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Zhanghai (John) Wang ◽  
Samuel Rodriguez
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Plastic Material ◽  
Material Model ◽  
Metal Loss ◽  
Technical Approach ◽  
Element Analysis ◽  
Elastic Plastic ◽  
Structural Discontinuity ◽  
Elastic Plastic Material

In fitness for service (FFS) assessments, one issue that people often encounter is a corroded area near a structural discontinuity. In this case, the formula-based sections of the FFS standard are incapable of evaluating the component without resorting to finite element analysis (FEA). In this paper, an FEA-based technical approach for evaluating FFS assessments using an elastic-plastic material model and reformed criteria is proposed.

Some factors affecting the loosening failure of bolted joints under vibration using finite element analysis

2017 ◽  
Vol 232 (21) ◽  
pp. 3942-3953 ◽  
Author(s):  
Hao Gong ◽  
Jianhua Liu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Vibration Frequency ◽  
Plastic Material ◽  
Material Model ◽  
Element Model ◽  
Bolted Joints ◽  
Vibration Parameter ◽  
Element Analysis ◽  
Loosening Rate

Finite element analysis has been regarded as an effective research method for analyzing the loosening failure of bolted joints under vibration. However, there exist some factors, which influence the accuracy and reliability of loosening results, thus determining the explanations of the loosening mechanism. In this study, a 3D finite element model of a typical bolted joint was built to investigate the effects of several different factors on the loosening under transverse vibration loading. These influencing factors include preload generation, vibration parameter, and material model. Based on the simulation results, it was found that applying the method of pretension element to generate preload instead of the actual method of torque was reliable and efficient. For the vibration parameter, it showed that the decrease rate in preload was higher for a larger vibration amplitude. But once the bearing surface reached complete slip, the loosening rate would keep constant. This was because the thread surface at that time reached a sticking state. Vibration frequency was proved to have no effect on the loosening behavior. This result demonstrated that the quasi-static assumption for vibration frequency was reasonable. Additionally, it also indicated that plastic material models only affected the preload loss in the initial several vibration cycles and had no influence on the loosening rate of preload after several vibration cycles. Finally, experiments were conducted to confirm qualitatively the results obtained based on finite element analysis.

Elastic—plastic finite element analysis of short flat bars with projections part 2: Axial loading

1996 ◽  
Vol 31 (1) ◽  
pp. 25-33 ◽  
Author(s):  
S J Hardy ◽  
M K Pipelzadeh
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Plastic Material ◽  
Axial Loading ◽  
Material Model ◽  
Shear Loading ◽  
Element Analysis ◽  
Elastic Plastic ◽  
Elastic Plastic Material ◽  
Stress Concentration Factors

This paper describes the results of a study of the elastic–plastic behaviour of short flat bars with projections subjected to monotonic and cyclic axial loading using finite element analysis. The results are complementary to similar results for (a) shear loading and (b) combined axial and shear loading. Six geometries are considered and elastic–plastic stress and strain data for both local and remote restraints are presented. These geometries and associated restraints result in elastic stress concentration factors in the range 1.69–4.96. A simple bilinear elastic–plastic material model is assumed and the results are normalized with respect to material properties so that they can be applied to geometrically similar components made from other materials which can be represented by the same material models.

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