Modelling the Complex Manufacturing History of a Pipework Joint and Assessment of Its Through Life Creep-Fatigue Damage Using Finite Element Based Methods

2010 ◽  
Author(s):  
D. P. Bray ◽  
R. J. Dennis ◽  
R. A. W. Bradford
Keyword(s):  
Finite Element ◽  
Fatigue Damage ◽  
Structural Integrity ◽  
Element Model ◽  
General Purpose ◽  
Element Analysis ◽  
Integrity Assessment ◽  
Creep Fatigue ◽  
History Of ◽  
Manufacturing History

The work reported in this paper investigates the complex manufacture and through-life operation of a pipework joint in a UK AGR boiler. Residual stresses resulting from the fabrication process can be a key driver for creep and creep-fatigue damage. The calculation of creep-fatigue damage for assessment purposes is typically undertaken within the framework of an appropriate assessment code (such as British Energy’s R5). The standard assessment approach usually requires the undertaking of elastic finite element analysis followed by Neuber construction to convert elastic stress ranges into elastic-plastic stress and strain ranges prior to the calculation of creep-fatigue damage. A combination of explicit and implicit finite element methods are employed in order to simulate a range of manufacturing processes which influence the material state for a branched pipework joint. The solution is effectively obtained within one finite element model, with re-meshing performed where necessary. This solution then feeds into a finite element based structural integrity assessment. The methods utilise the principles outlined in the British Energy R5 assessment code but utilise the inelastic strains calculated directly from analysis. The methods are based around the general purpose finite-element code Abaqus enhanced by the use of user-defined subroutines CREEP and UVARM. This paper describes analyses performed to simulate the complex manufacturing history of a branched pipework component, and to estimate its subsequent in service creep-fatigue damage using finite element based methods.

An Evaluation of Creep-Fatigue Damage for the Prototype Process Heat Exchanger of the NHDD Plant

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Hyeong-Yeon Lee ◽  
Kee-Nam Song ◽  
Yong-Wan Kim ◽  
Sung-Deok Hong ◽  
Hong-Yune Park
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
High Temperature ◽  
Fatigue Damage ◽  
Inlet Temperature ◽  
Alloy 617 ◽  
Element Analysis ◽  
Creep Fatigue ◽  
Process Heat ◽  
Very High

A process heat exchanger (PHE) transfers the heat generated from a nuclear reactor to a sulfur-iodine hydrogen production system in the Nuclear Hydrogen Development and Demonstration, and was subjected to very high temperature up to 950°C. An evaluation of creep-fatigue damage, for a prototype PHE, has been carried out from finite element analysis with the full three dimensional model of the PHE. The inlet temperature in the primary side of the PHE was 950°C with an internal pressure of 7 MPa, while the inlet temperature in the secondary side of the PHE is 500°C with internal pressure of 4 MPa. The candidate materials of the PHE were Alloy 617 and Hastelloy X. In this study, only the Alloy 617 was considered because the high temperature design code is available only for Alloy 617. Using the full 3D finite element analysis on the PHE model, creep-fatigue damage evaluation at very high temperature was carried out, according to the ASME Draft Code Case for Alloy 617, and technical issues in the Draft Code Case were raised.

Overview of EASICS Weldment Assessment Route Development Through Inelastic Analysis

2020 ◽  
Author(s):  
S. May ◽  
S. Bate ◽  
M. Chevalier ◽  
D. Dean
Keyword(s):  
Nuclear Reactor ◽  
Structural Integrity ◽  
Element Analysis ◽  
Validation Data ◽  
Integrity Assessment ◽  
Inelastic Analysis ◽  
Inelastic Material ◽  
Creep Fatigue ◽  
Material Mismatch

Abstract Structural integrity assessment of weldments within metal structures is key to substantiate any nuclear reactor design. The assessment of weldments should consider the localised strain enhancement due to weldment geometry and material mismatch. For high temperature plant designs (operating within the creep regime), R5 Volume 2/3 Appendix A4 provides a procedure for the assessment of creep-fatigue initiation in austenitic and ferritic steel weldments, which accounts for the associated strain enhancement using a Weld Strain Enhancement Factor (WSEF). The current austenitic Type 1 WSEFs in R5 Volume 2/3 have been defined by data attained primarily for plate butt weldments under applied bending loads, and this factor is used for all butt weldments. It has been proposed that the weld strain enhancement may be dependent on loading, geometric and material mismatch conditions, and that adopting a single factor in an assessment may introduce varying levels of conservatism, which are unquantified. This work has included reviewing the current R5 Type 1 WSEF against existing validation data, previous inelastic Finite Element Analysis (FEA) studies and the use of inelastic material models in the FEA of weldments subject to cyclic loading.

Different Structural Integrity Assessment Methods for Pipe Containing Circumferential Through-Thickness Crack

2011 ◽  
Author(s):  
Huifeng Jiang ◽  
Xuedong Chen ◽  
Zhichao Fan
Keyword(s):  
Fracture Toughness ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Structural Integrity ◽  
Load Ratio ◽  
Limit Load ◽  
Element Analysis ◽  
Integrity Assessment ◽  
Significant Difference ◽  
Calculated Load

Heretofore, several kinds of codes are applicable to the structural integrity assessment for pipe containing defects, i.e. API 579, R6 and BS 7910 etc. In this paper, different methods from API 579-1/ASME FFS-1: 2007 and R6-2000 were employed to assess the integrity of pipe containing a circumferential through-thickness crack. However, there was a significant difference between the calculated load ratios by these two codes, although the calculated fracture ratios were very close. To verify these results, elastic-plastic finite element analysis was carried out to calculate the limit load and the load ratio. Additionally, the experimental results and our previous engineering experience were also referred to. The final results imply that the larger load ratio obtained from R6-2000 rather than API 579 code is more reasonable for the pipe with good fracture toughness.

Structural Integrity Assessment Criteria and Service Life Prediction of Cold Wrinklebends

2012 ◽  
Author(s):  
Xian-Kui Zhu ◽  
Brian N. Leis
Keyword(s):  
Finite Element ◽  
Service Life ◽  
Structural Integrity ◽  
Pipeline Steel ◽  
Three Dimensional ◽  
Computation Time ◽  
Element Analysis ◽  
Integrity Assessment ◽  
Fea Model ◽  
Hardening Models

Three-dimensional elastic-plastic finite element analysis (FEA) is performed in this paper to simulate the complicated stresses and deformation of wrinklebends in a pipeline from its bending formation to operation under cyclic loading. Three plastic hardening models (isotropic, kinematic and combined isotropic/kinematic) are discussed and used in FEA of wrinklebend response that considers strain hardening and Bauschinger effects. The FEA simulation is carried out first for an elbow held at constant pressure while subject to cyclic bending, which serves as a benchmark case. The results show that the three hardening models lead to very different outcomes. Comparable FEA simulations are then developed for wrinklebends under cyclic pressure. Detailed parametric analysis is considered, including finite-element type, element sensitivity, computation time, and material input data. Based on those results viable nonlinear FEA model is developed as the basis to quantify wrinklebend response under service-like conditions. Based on the FEA results, fatigue damage is quantified using the Smith, Watson and Topper (SWT) parameter, and thereafter a damage criterion is proposed to predict the fatigue life of a wrinklebend under the pressure cycles of 72%–10% of SMYS for typical X42 pipeline steel. The results show that the wrinkle aspect ratio H/L is a key parameter to control the service life of a wrinklebend.

New Data on the Capacity of X-Joints Under Tension and Implications for Codes

2008 ◽  
Author(s):  
Adrian F. Dier ◽  
Philip Smedley ◽  
Gunnar Solland ◽  
Hege Bang
Keyword(s):  
Finite Element ◽  
Structural Integrity ◽  
Hot Spot ◽  
Case Scenario ◽  
Element Analysis ◽  
Worst Case ◽  
Numerical Work ◽  
Hot Spot Stress ◽  
Integrity Assessment ◽  
Existing Structures

This paper reviews available static strength data and presents results of finite element analyses on first crack loads and ultimate loads of X-joints in tension. A critique of existing guidance for such joints is given. An examination of hot spot stress for such joints is presented, together with new capacity formulations based on test data. The new formulations are verified with reference to new data from a finite element analysis. The new capacity formulations will be of interest to regulatory authorities, to designers of new offshore installations and to engineers carrying out assessments of existing structures. It is also expected that the formulations will be considered by code drafting committees, e.g. for API RP2A, ISO 19902 and NORSOK, during code revisions. The paper demonstrates that present guidance is unduly conservative in two respects: (1) high γ joints (i.e. thin-walled chords) in the range 0.7 ≤ β ≤ 0.9 joints (i.e. moderately high brace/chord diameter ratios), and (2) joints with β = 1.0 having low γ. However, it is shown that present guidance may be optimistic for low γ joints with β < 0.9. The new capacity formulations proposed in this paper correct these deficiencies. As one example, the new formulations give an increase of 60% in capacity compared to existing guidance for a joint with β = 1.0 and γ = 10, not untypical of many joints in service. In the near term, the paper may be most appreciated by those involved with structural integrity assessment studies. There have been some recent examples where existing guidance has indicated that some primary structural joints are under-strength. This has prompted extensive numerical work to prove the adequacy of the joints. A worst case scenario would be the implementation of unnecessary offshore strengthening work.

scholarly journals Numerical Analysis of Eccentrically Loaded Cold-Formed Plain Channel Columns

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
A. P. Nivethitha ◽  
G. Vani ◽  
P. Jayabalan
Keyword(s):  
Finite Element ◽  
Parametric Study ◽  
Ultimate Load ◽  
Element Model ◽  
Free Edge ◽  
General Purpose ◽  
Element Analysis ◽  
Finite Element Software ◽  
Axially Loaded ◽  
The Finite Element Model

Finite element analysis of pinned cold-formed plain channel columns of different width-to-thickness ratios is presented in this paper. The study is focused not only on axially loaded columns, but also on eccentrically loaded columns. The general purpose finite element software ABAQUS 6.12 was used, and the force controlled loading was adopted. Geometric and material nonlinearities were incorporated in the finite element model. The ultimate loads are compared with the direct strength method (DSM) for axially loaded columns. Also, a parametric study is done by varying the length of the column and width of the unstiffened element. It is observed that the results correlate better with the DSM values for columns having unstiffened elements of lower bf/t ratios. The change in ultimate load is studied only in ABAQUS, as the position of load moves towards the free edge and the supported edge of the unstiffened element. A parametric study is done by varying the nonuniform compression factor for the columns. It is observed that the ultimate load increases as the position of load moves towards the supported edge and it is influenced by the bf/t ratio of the unstiffened element.

Finite Element Simulation of a Circumferential Through-Thickness Crack in a Cylinder

2014 ◽  
Author(s):  
Sutham Arun ◽  
Andrew H. Sherry ◽  
Mike C. Smith ◽  
Mohammad Sheikh
Keyword(s):  
Finite Element ◽  
Large Scale ◽  
Structural Integrity ◽  
Mouth Opening ◽  
Element Model ◽  
Crack Mouth Opening Displacement ◽  
Opening Displacement ◽  
Integrity Assessment ◽  
Final Extent ◽  
Welded Pipe

This paper presents the results of a structural integrity assessment of a large-scale test undertaken as part of the EU programme STYLE on a repair welded pipe containing a circumferential through-thickness crack. The pipe was manufactured from two Esshete 1250 stainless steel pipes joined by a girth weld containing a deep repair. A through-thickness circumferential pre-crack was introduced to the centre of the repair prior to testing in four-point bend. The assessment used a finite element model created in Abaqus, with the weld residual stress introduced by an iterative technique. Linear elastic fracture mechanics was used to evaluate the stress intensity factor KI for the defect and elastic-plastic analyses were performed to characterise the crack driving force J along the crack front. The predicted crack mouth opening displacement as a function of load was compared with the test results and the derived variation in J used to predict crack initiation and growth. The results predicted the global behaviour of the test to within approximately 7% at final load, and the position of maximum crack growth. However, the final extent of crack extension is under-predicted. Reasons for this underprediction are suggested.

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