Plastic Limit Loads for Pipe-in-Pipes With Circumferential Through-Wall Cracks Based on Finite Element Analyses

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Se-Chang Kim ◽  
Jae-Boong Choi ◽  
Hyun-Su Kim ◽  
Nam-Su Huh ◽  
Kyunghoon Kim
Keyword(s):  
Finite Element ◽  
Extreme Environments ◽  
Three Dimensional ◽  
Bending Moment ◽  
Piping System ◽  
Plastic Limit ◽  
Limit Loads ◽  
Closed Form Solutions ◽  
Integrity Assessment ◽  
Three Dimensional Finite Element

Pipe-in-pipes (PIPs) are generally applied to the extreme environments such as deep-sea and next-generation reactors due to their functionality and robustness. Thus, it is important to estimate the fracture behaviors of PIPs for integrity assessment of this unique piping system. In this work, the plastic collapse behaviors of PIPs with circumferential through-wall cracks (TWCs) are investigated based on three-dimensional finite element (FE) limit analysis, where the crack is assumed to be located at the inner pipe of PIPs. As for loading conditions, internal pressure, axial tension, and global bending moment are considered. In particular, the bending restraint effect induced by interconnection between the inner and outer pipes of PIPs is quantified through the FE analyses considering a practical range of geometries of PIPs. Based on the FE analysis results, the tabular and closed-form solutions of the plastic limit loads of the circumferential through-wall cracked PIPs are proposed, and then, validated against numerical simulations.

Effect of Bend Angle on Plastic Limit Loads of Pipe Bends Under In-Plane Bending Moment

2016 ◽  
Author(s):  
Shunjie Li ◽  
Changyu Zhou ◽  
Jian Li ◽  
Xinting Miao
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Large Strain ◽  
Large Angle ◽  
Three Dimensional ◽  
Bending Moment ◽  
Limit Load ◽  
Bend Angle ◽  
Plastic Limit ◽  
Limit Loads

The effect of bend angle on plastic limit loads of pipe bends (elbows) under in-plane opening and closing bending moment is presented using three-dimensional large strain nonlinear finite element analyses. The results show that the presence of ovality significantly leads to the stress concentration in the middle cross section, which is the critical section of pipe bends. Meanwhile the state of stress concentration is also associated with the loading modes including the in-plane opening bending moment and the closing bending moment. Then plastic limit loads of pipe bends are further studied. It is found that plastic limit loads are decreasing with the increase of bend angles. Especially the variation of plastic limit loads of small angle pipe bends (bend angle from the 0 degree to 90 degree) is larger than that of large angle pipe bends (bend angle greater than 90 degree). Based on the finite element results, the present plastic limit load solutions are not fit for the large angle pipe bends (bend angle greater than 90 degree).

Plastic Limit Analysis of an Elbow with Various Wall-Thinning Geometries

2008 ◽  
Vol 385-387 ◽  
pp. 833-836
Author(s):  
Sang Min Lee ◽  
Young Hwan Choi ◽  
Hae Dong Chung ◽  
Yoon Suk Chang ◽  
Young Jin Kim
Keyword(s):  
Nuclear Power ◽  
Three Dimensional ◽  
Bending Moment ◽  
Limit Load ◽  
Nuclear Industry ◽  
Bend Angle ◽  
Piping System ◽  
Plastic Limit ◽  
Limit Loads ◽  
Wall Thinning

A piping system including straight pipes, elbows and tee branches in a nuclear power plant is mostly subjected to severe loading conditions with high temperature and pressure. In particular, the wall-thinning of an elbow due to flow accelerated corrosion is one of safety issues in the nuclear industry. In this respect, it is necessary to investigate the limit loads of an elbow with a wall-thinned part for evaluating integrity. In this paper, three dimensional plastic limit analyses are performed to obtain limit loads of an elbow with different bend angles as well as defect geometries under internal pressure and in-plane/out-of-plane bending moment. The limit loads are also compared with the results from limit load solutions of an uninjured elbow based on the von Mises yield criteria. Finally, the effects of significant factors, bend angle and defect shape, are quantified to estimate the exact load carrying capacity of an elbow during operation.

Plastic Limit Loads for Through-Wall Cracked Pipes Using Finite Element Limit Analysis

2006 ◽  
Vol 321-323 ◽  
pp. 724-728
Author(s):  
Nam Su Huh ◽  
Yoon Suk Chang ◽  
Young Jin Kim
Keyword(s):  
Finite Element ◽  
Limit Analysis ◽  
Structural Integrity ◽  
Three Dimensional ◽  
Limit Load ◽  
Plastic Behavior ◽  
Plastic Limit ◽  
Integrity Assessment ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic

The present paper provides plastic limit load solutions for axial and circumferential through-wall cracked pipes based on detailed three-dimensional (3-D) finite element (FE) limit analysis using elastic-perfectly plastic behavior. As a loading condition, both single and combined loadings are considered. Being based on detailed 3-D FE limit analysis, the present solutions are believed to be valuable information for structural integrity assessment of cracked pipes.

Finite Element Limit Loads for Circumferential Through-Wall Cracked Pipe Bends Under In-Plane Bending

2006 ◽  
Author(s):  
Yun-Jae Kim ◽  
Chang-Sik Oh ◽  
Young-Il Kim ◽  
Chi-Yong Park
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Small Strain ◽  
Plastic Limit ◽  
Crack Location ◽  
Perfectly Plastic ◽  
Dimensional Finite Element ◽  
Plane Bending ◽  
Elastic Perfectly Plastic ◽  
Three Dimensional Finite Element

This paper proposes plastic limit and collapse loads for circumferential through-wall cracked pipe bends under in-plane bending, based on three-dimensional finite element limit analyses. The material is assumed to be elastic-perfectly-plastic, but both the geometrically linear (small strain) and the geometrically nonlinear (large geometry change) options are employed. Regarding crack location, both extrados and intrados cracks are considered. Moreover, for practical application, closed-form approximations of plastic limit and collapse loads are proposed based on the FE results, and compared with corresponding solutions for straight pipes.

Reference Stresses for Cold-Tube-Bends Including Thickness Variation and Ovality Using Three-Dimensional Finite Element Method

2009 ◽  
Author(s):  
Khosrow Zarrabi ◽  
Felix Kumiadi Kwok
Keyword(s):  
Finite Element ◽  
Cross Section ◽  
Power Plants ◽  
Three Dimensional ◽  
Thickness Variation ◽  
Straight Tube ◽  
Boiler Tube ◽  
Integrity Assessment ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

Tube-bends are extensively used in the boilers of power plants. Tube-bends are manufactured by bending a straight tube section. During this process, the tube cross-section becomes oval and its thickness varies around the circumference of its cross-section. This study uses three-dimensional finite element analysis to establish practical and simple equations for predicting the plastic collapse pressures and the reference stresses of the oval and variable thickness boiler-tube-bends. Such equations are pertinent to the design and integrity assessment of the boiler tube-bends.

scholarly journals A hybrid analytical-numerical solution for a circular pile under lateral load in multilayered soil

2020 ◽  
Vol 14 (1) ◽  
pp. 1-14
Author(s):  
Nghiem Xuan Hien
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Differential Equations ◽  
Numerical Solution ◽  
Elastic Foundation ◽  
Three Dimensional ◽  
Bending Moment ◽  
Lateral Load ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

A hybrid analytical-numerical solution is proposed to solve the problem of a laterally loaded pile with a circular cross-section in multilayered soils. In the pile-soil model, the lateral load is located at the pile head including both lateral force and bending moment. The single pile is considered as a beam on elastic foundation while shear beams model the soil column below the pile toe. The differential equations governing pile deflections are derived based on the energy principles and variational approaches. The differential equations are solved iteratively by using the finite element method that provides results of pile deflection, rotation angle, shear force, and bending moment along the pile and equivalent stiffness of the pile-soil system. The modulus reduction equation is also developed to match the proposed results well to the three-dimensional finite element analyses. Several examples are conducted to validate the proposed method by comparing the analysis results with those of existing analytical solutions, the three-dimensional finite element solutions. Keywords: beam on elastic foundation; finite element method; pile; energy principle; lateral load.

A New Stress Intensification Factor of Pipe-In-Pipes Based on Finite Element Analyses

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Se-Chang Kim ◽  
Jae-Boong Choi ◽  
Moon Ki Kim ◽  
Hyun-Su Kim ◽  
Nam-Su Huh
Keyword(s):  
Finite Element ◽  
Bending Moment ◽  
Piping System ◽  
Finite Element Analyses ◽  
Closed Form Solutions ◽  
System A ◽  
Stress Intensification Factor ◽  
Geometric Variables ◽  
Stress Behaviors ◽  
External Forces

For the design of a transmission piping system, a stress intensification factor (SIF) is generally used for the stress calculations of piping components due to external forces, and the solutions for the single-walled piping components can be found in the existing design codes. However, it is quite difficult to obtain the reliable estimations for pipe-in-pipes (PIPs) from the existing solutions, because the PIPs show significantly different behaviors compared to the single-walled piping components due to the restraint effect induced by the outer pipe of the PIP. In this paper, the estimation schemes for the stress behaviors of the PIPs were proposed based on the detailed finite element (FE) analyses. In order to quantify the restraint effect, the FE analyses were conducted by considering various geometric variables of the PIPs under an internal pressure and a global bending moment. Based on the FE results, the tabular and closed-form solutions of the SIFs of PIPs were newly proposed. Finally, the proposed SIF estimations were validated against numerical results.

Limit Loads for Circumferential Cracked Pipe Bends under In-Plane Bending

2006 ◽  
Vol 321-323 ◽  
pp. 38-42
Author(s):  
Yun Jae Kim ◽  
Chang Sik Oh ◽  
Bo Kyu Park ◽  
Young Il Kim
Keyword(s):  
Three Dimensional ◽  
Surface Cracks ◽  
Plastic Limit ◽  
Limit Loads ◽  
Perfectly Plastic ◽  
Plastic Materials ◽  
Dimensional Finite Element ◽  
Plane Bending ◽  
Elastic Perfectly Plastic ◽  
Three Dimensional Finite Element

This paper presents limit loads for circumferential cracked pipe bends under in-plane bending, based on detailed three-dimensional finite element limit analyses. FE analyses are performed based on elastic-perfectly-plastic materials and the geometrically linear assumption. Both through-wall cracks and part-through surface cracks (having constant depths) are considered, together with different crack locations (extrados and intrados). Based on the FE results, closed-form approximations are proposed for plastic limit loads of pipe bends. It is found that limit loads of pipe bends are smaller than those of straight pipes, but are close for deep and long cracks.

Finite Element Analysis and Stress Intensification Factor Determination for Core to Jacket Joints

2009 ◽  
Author(s):  
Pishdad Mohammadi-Araz
Keyword(s):  
Finite Element ◽  
Thermal Stress ◽  
Stress Analysis ◽  
Three Dimensional ◽  
Piping System ◽  
Beam Model ◽  
Element Analysis ◽  
The Core ◽  
Stress Intensification Factor ◽  
Three Dimensional Finite Element

In this study Stress Intensification Factor (“SIF”) and stress analysis for core to jacket joints are investigated. The three-dimensional finite element shell model consists of two shells: the jacket and the core. The effect of the welded joint discontinuity is taken into account by applying a stress concentration factor. It is presumed that the core and shell are ASTM A-106 GR B [1]. The joint is modeled for different pipe-outside diameters and wall-thicknesses and SIF is calculated for different Head shapes, which are discussed further in this paper. The model is examined with different mesh types and the results are discussed. Temperature gradient in pipe wall-thickness causes thermal stress. The thermal stress, combined with operating, sustained and differential expansion stress are considered in the stress analysis of core and jacket shell. The results for different temperature gradients are compared. The imposed displacement loads caused by global temperature difference between core and the jacket are taken from a beam model run of a typical discontinuous steam jacketed piping system.

Sign in / Sign up

Export Citation Format

Share Document