Research on Safety Assessment Method for Pressure Pipe With Incomplete Welding Defects Under Complicated Loadings

2010 ◽  
Author(s):  
Zhijiang Jin ◽  
Xianping Wan ◽  
Chenghang Jiang
Keyword(s):  
Internal Pressure ◽  
Safety Assessment ◽  
Limit Load ◽  
Assessment Method ◽  
Curved Surface ◽  
Assessment Procedure ◽  
Plastic Limit ◽  
Pressure Pipe ◽  
Welding Defects ◽  
Plastic Limit Load

Since most pressure pipe materials have good toughness, the failure mode of pipe is usually the plastic failure controlled by limit load. The incomplete welding defect is very common in the pipe, and its existence will reduce the load-carrying capacity of pipes. The pipe with incomplete welding defects can be continued using only after passing the appropriate safety assessment, so the research on safety assessment procedure for pressure pipe with incomplete welding defects under combined bending, torsion and internal pressure loadings has a great theoretical and practical engineering value. By using theoretical analyzing method of plastic limit load, the plastic limit load of pressure pipe with different defect size or pipe diameter ratio are calculated in this paper, then safety assessment curved surface and its express equation are obtained by fitting calculation data. Finally a safety assessment procedure is developed for pressure pipes under combined bending, torsion and internal pressure loadings according to the curved surface.

Plastic limit load analysis for pressure pipe with incomplete welding defects based on the extended Net Section Collapse Criteria

2010 ◽  
Vol 11 (6) ◽  
pp. 440-448 ◽  
Author(s):  
Zhi-jiang Jin ◽  
Cheng-hang Jiang ◽  
Xian-ping Wan ◽  
Po Chen ◽  
Xiao-fang Wang
Keyword(s):  
Limit Load ◽  
Plastic Limit ◽  
Pressure Pipe ◽  
Welding Defects ◽  
Plastic Limit Load ◽  
Load Analysis

Shakedown and Limit Analysis of Kinematic Hardening Piping Elbows Under Internal Pressure and Bending Moments

2021 ◽  
Author(s):  
Heng Peng ◽  
Yinghua Liu
Keyword(s):  
Yield Strength ◽  
Internal Pressure ◽  
Limit Analysis ◽  
Kinematic Hardening ◽  
Limit Load ◽  
Bending Moments ◽  
Plastic Limit ◽  
Plastic Limit Load ◽  
Interaction Curves ◽  
Shakedown Limit

Abstract In this paper, the Stress Compensation Method (SCM) adopting an elastic-perfectly-plastic (EPP) material is further extended to account for limited kinematic hardening (KH) material model based on the extended Melan's static shakedown theorem using a two-surface model defined by two hardening parameters, namely the initial yield strength and the ultimate yield strength. Numerical analysis of a cylindrical pipe is performed to validate the outcomes of the extended SCM. The results agree well with ones from literature. Then the extended SCM is applied to the shakedown and limit analysis of KH piping elbows subjected to internal pressure and cyclic bending moments. Various loading combinations are investigated to generate the shakedown limit and the plastic limit load interaction curves. The effects of material hardening, elbow angle and loading conditions on the shakedown limit and the plastic limit load interaction curves are presented and analysed. The present method is incorporated in the commercial finite element simulation software and can be considered as a general computational tool for shakedown analysis of KH engineering structures. The obtained results provide a useful information for the structural design and integrity assessment of practical piping elbows.

Determination of Transition From Thin Shell to Thick Shell Theory for Torispherical Heads With Head Dish Radius to Thickness Ratios Under 20

2020 ◽  
Author(s):  
Barry Millet ◽  
Kaveh Ebrahimi
Keyword(s):  
Internal Pressure ◽  
Transition Point ◽  
Limit Load ◽  
Thick Wall ◽  
Ratio Test ◽  
Thin Wall ◽  
Plastic Limit ◽  
Element Analysis ◽  
Perfectly Plastic ◽  
Plastic Limit Load

Abstract This paper will clarify the point of transition where the behavior of the dish of a torispherical head goes from thin wall theory (collapse failure and membrane) to thick wall (burst failure) as the head dish radius to thickness ratios (L/t) gets smaller. There are several stated ratio limits for this transition. Three separate Welding Research Bulletins WRC 364 New Design Curves for Torispherical Heads[1], WRC 444 Buckling Criteria for Torispherical Heads Under Internal Pressure [3] and, WRC 501 Design of Torispherical and Ellipsoidal Heads Subjected to Internal Pressure[4] each provide a different definition of the transition point, that being 16.67, 15 and 20 respectively. This paper will review the actual test performed for L/t ratios from 20 down to 15 (which is the lowest ratio test run) and provide the results of a numerical desktop study in lieu of actual testing. Linear elastic, elastic perfectly plastic limit load and elastic plastic limit load finite element analysis will be parametrically run across many L/t ratios and the knuckle radius will be varied across the runs. The results will be reviewed to check through wall behavior to find the transition point of thin to thick wall behavior. These will also be compared against the existing ASME BVP Section VIII Division 2 [5] formulas.

scholarly journals Plastic limit load of ellipsoidal pressure vessel head with nozzle under internal pressure loading

2013 ◽  
Vol 18 (4) ◽  
pp. 1263-1274 ◽  
Author(s):  
V.N. Skopinsky ◽  
N.A. Berkov ◽  
A.B. Smetankin
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Limit Load ◽  
Rate Of Change ◽  
Pressure Loading ◽  
Plastic Limit ◽  
Elastic Plastic ◽  
Limit Pressure ◽  
Plastic Limit Load ◽  
Plastic Limit Pressure

Abstract A new method and numerical procedure for determining the plastic limit load in an ellipsoid-cylinder intersection using the elastic-plastic finite element analysis are presented. The proposed method is based on the maximum criterion of the rate of change of the relative plastic work. For the elastic-plastic analysis of the nozzle connections the 2D finite element method and plasticity theory with strain hardening are used. The results of the comparison of the plastic limit pressure obtained on the basis of different known criteria and the proposed criterion are presented. A parametric study of ellipsoidal heads with a nozzle under internal pressure loading was performed. The effects of nondimensional geometric parameters of shell intersection on the plastic limit pressure are discussed.

Analysis and Experiments on the Plastic Limit Load of Elbows under Combined Pressure and In-Plane Closing Bending Moment

2013 ◽  
Vol 774-776 ◽  
pp. 1090-1097 ◽  
Author(s):  
Zhi Xiang Duan ◽  
Kun Shi
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Safety Assessment ◽  
Bending Moment ◽  
Limit Load ◽  
Experimental Results ◽  
Plastic Limit ◽  
Element Analysis ◽  
Limit Pressure ◽  
Plastic Limit Load

This paper discusses the plastic limit load of elbows without defects and with local thinned area (LTA) in the extrados under combined pressure and in-plane closing bending moment. Finite element analysis (FEA) and experiments have been used. The results of FEA show that, for the elbows without defects, when the ratio of pressure to the limit pressure (P/PL) is smaller than 0.469, the limit moment of elbows increases with the increasing pressure; when the ratio (P/PL) is bigger than 0.469, the limit moment of elbow decreases with the increasing pressure. For the elbows with LTA, the FEA results show that with different LTA the variation of the limit load of elbows to the pressure is different. Perhaps, the limit moment of elbows always decreases with the increasing pressure. It is also likely that the limit moment of elbows increases with the increasing pressure and then decreases with the increasing pressure. The results of FEA are consistent with the experimental results. By fitting the results of FEA, the safety assessment figure for elbows under combined pressure and in-plane closing bending moment is drawn.

Limit Load Solutions for Pipes With Through-Wall Crack Under Single and Combined Loading Based on Finite Element Analyses

2006 ◽  
Vol 129 (3) ◽  
pp. 468-473 ◽  
Author(s):  
Nam-Su Huh ◽  
Yun-Jae Kim ◽  
Young-Jin Kim
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Limit Analysis ◽  
Limit Load ◽  
Combined Loading ◽  
Thickness Effect ◽  
Plastic Behavior ◽  
Plastic Limit ◽  
Integrity Assessment ◽  
Plastic Limit Load

The present paper provides plastic limit load solutions for axial and circumferential through-wall cracked pipes based on detailed three-dimensional (3D) finite element (FE) limit analysis using elastic-perfectly plastic behavior. As a loading condition, axial tension, global bending moment, internal pressure, combined tension and bending, and combined internal pressure and bending are considered for circumferential through-wall cracked pipes, while only internal pressure is considered for axial through-wall cracked pipes. In particular, more emphasis is given for through-wall cracked pipes subject to combined loading. Comparisons with existing solutions show a large discrepancy in short through-wall crack (both axial and circumferential) for internal pressure. In the case of combined loading, the FE limit analyses results show the thickness effect on limit load solutions. Furthermore, the plastic limit load solution for circumferential through-wall cracked pipes under bending is applied to derive plastic η and γ factor of testing circumferential through-wall cracked pipes to estimate fracture toughness. Being based on detailed 3D FE limit analysis, the present solutions are believed to be meaningful for structural integrity assessment of through-wall cracked pipes.

A Study on the Effect of Non-Idealized Crack on a 90° Elbow by Using Finite Element Analysis

2018 ◽  
Author(s):  
Jae-Hee Kim ◽  
Min-Kyu Kim ◽  
Ye-Rin Choi ◽  
Doo-Ho Cho ◽  
Moon Ki Kim ◽  
...  
Keyword(s):  
Finite Element ◽  
Numerical Study ◽  
Limit Load ◽  
Element Model ◽  
Assessment Method ◽  
Accurate Solution ◽  
Fe Model ◽  
Plastic Limit ◽  
Element Analysis ◽  
Plastic Limit Load

The present paper proposed the modified limit load solution related to code case N-513-4 which is currently actively researched. To apply to assessment method for an elbow in code case N-513-4, the crack should be postulated as the idealized circumferential through-wall crack (TWC). For this reason, it could be led to overestimate the results due to the assumption of real crack shape. Then, the many research which is related to an accurate solution for a straight pipe by considering realistic crack has been investigated. However, the accurate solution for the elbow with non-idealized TWC is still lacked. Therefore, based on three-dimensional finite element model, the effect of non-idealized circumferential TWC on plastic limit load was investigated under internal pressure. To do this, the finite element (FE) model and analysis procedure employed in the present numerical study were validated by comparing the present finite element analyses result with existing solutions for idealized TWC in the elbow. Then, the correction factor for calculating plastic limit load was newly proposed as a tabulated form by considering practical ranges of geometry.

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