Structural Integrity Estimates of Steam Generator Tubes Containing Wear-Type Defects

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Yoon-Suk Chang ◽  
Jong-Min Kim ◽  
Nam-Su Huh ◽  
Young-Jin Kim ◽  
Seong-Sik Hwang ◽  
...  
Keyword(s):  
Steam Generator ◽  
Structural Integrity ◽  
Equivalent Stress ◽  
Three Dimensional ◽  
Plastic Instability ◽  
Failure Behavior ◽  
Dimensional Finite Element ◽  
Tapered Angle ◽  
Three Dimensional Finite Element ◽  
Steam Generator Tubes

It is requested that steam generator tubes with defects exceeding 40% of wall thickness in depth should be plugged to sustain all postulated loads with appropriate margin. This critical defect size has been determined based on a concept of plastic instability, however, which is known to be too conservative for some locations and types of defects. The application of this concept may even cause premature retirement of steam generator tubes. In reality, a reliable structural integrity estimation for steam generator tubes containing a defect has received increasing attention. Although several guidelines have been developed and used for assessing defect containing tubes, most of these guidelines are focused on stress corrosion cracking or wall-thinning phenomena. Because some of steam generator tubes fail due to fretting and so on, specific integrity estimation schemes for relevant defects are required. In this paper, more than a hundred three-dimensional finite element analyses of steam generator tubes under internal pressure condition are carried out to simulate the failure behavior of steam generator tubes with specific defect configurations: elliptical wear-type, tapered wedge-type, and flat wear-type defects. After investigating the effect of key parameters such as defect depth, defect length, and wrap or tapered angle on equivalent stress across the ligament thickness, burst pressure estimation equations are proposed in relation to material strengths. Predicted burst pressures agreeded well with the corresponding experimental data, so the proposed equations can be used to assess the structural integrity of steam generator tubes with wear-type defects.

Failure Pressure Estimates of Steam Generator Tubes Containing Wear-Type Defects

2006 ◽  
Author(s):  
Yoon-Suk Chang ◽  
Jong-Min Kim ◽  
Nam-Su Huh ◽  
Young-Jin Kim ◽  
Seong-Sik Hwang ◽  
...  
Keyword(s):  
Steam Generator ◽  
Equivalent Stress ◽  
Three Dimensional ◽  
Plastic Instability ◽  
Failure Behavior ◽  
Dimensional Finite Element ◽  
Estimation Scheme ◽  
Wrap Angle ◽  
Three Dimensional Finite Element ◽  
Steam Generator Tubes

It is commonly requested that steam generator tubes with defects exceeding 40% of wall thickness in depth should be plugged to sustain all postulated loads with appropriate margin. The critical defect dimensions have been determined based on the concept of plastic instability. This criterion, however, is known to be too conservative for some locations and types of defects. In this context, the accurate failure estimation for steam generator tubes with a defect draws increasing attention. Although several guidelines have been developed and are used for assessing the integrity of defected tubes, most of these guidelines are related to stress corrosion cracking or wall-thinning phenomena. As some of steam generator tubes are also failed due to fretting and so on, alternative failure estimation schemes for relevant defects are required. In this paper, three-dimensional finite element (FE) analyses are carried out under internal pressure condition to simulate the failure behavior of steam generator tubes with different defect configurations; elliptical wastage type, wear scar type and rectangular wastage type defects. Maximum pressures based on material strengths are obtained from more than a hundred FE results to predict the failure of the steam generator tube. After investigating the effect of key parameters such as wastage depth, wastage length and wrap angle, simplified failure estimation equations are proposed in relation to the equivalent stress at the deepest point in wastage region. Comparison of failure pressures predicted according to the proposed estimation scheme with some corresponding burst test data shows good agreement, which provides a confidence in the use of the proposed equations to assess the integrity of steam generator tubes with wear-type defects.

Fatigue Assessment of Dented Rigid Risers

2019 ◽  
Author(s):  
Elvis J. O. Santander ◽  
Bianca Pinheiro ◽  
Carlos Magluta ◽  
Ney Roitman
Keyword(s):  
Stress Concentration ◽  
Structural Integrity ◽  
Three Dimensional ◽  
Element Model ◽  
Oil Fields ◽  
Dimensional Finite Element ◽  
Concentration Factors ◽  
Stress Concentration Factors ◽  
Three Dimensional Finite Element ◽  
Remaining Fatigue Life

Abstract In the development of oil fields, submarine pipelines are used in various applications. These pipelines and risers are subject to accidents that may occur during operation, such as shocks between risers or shocks between a riser and an anchor, rock, or any equipment or heavy object, which may cause mechanical failure, such as dents. The objective of this work is to study of the effect of the introduction of plain dents on the structural integrity of rigid risers under fully reversed bending. A three dimensional finite element model was developed to estimate the stress concentration on dented risers under bending. Several numerical simulations were carried out to evaluate stress concentration factors (SCFs) for varying dimensions of dents and risers, in a parametric study. These SCFs can be used in the prediction of the remaining fatigue life of dented rigid risers.

Equivalent Stress Analysis of Piercing Process in Diescher’s Mill Using Finite Element Method

2013 ◽  
Vol 648 ◽  
pp. 170-173
Author(s):  
Lu Lu ◽  
Zhao Xu Wang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Equivalent Stress ◽  
Three Dimensional ◽  
Structural Evolution ◽  
Work Piece ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Distribution Of Stress ◽  
Element Method

In this paper, the simulation of the piercing process is performed by the three dimensional finite element method in Diescher’s mill. After a short description of the problem the numerical model of the process is described. The simulated results visualize dynamic evolution of equivalent stress, especially inside the work-piece. The non-uniform distribution of stress on the internal and external surface of the work-piece is a distinct characteristic of processing tube piercing. And it is the basic data for improving tool and design, predicting, damage and controlling the micro-structural evolution of processing tube piercing.

Design Optimization for Double-T Root and Rim of Turbine Blade with Three-Dimensional Finite Element Method

2012 ◽  
Vol 215-216 ◽  
pp. 239-243
Author(s):  
Ming Hui Zhang ◽  
Di Zhang ◽  
Yong Hui Xie
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Design Optimization ◽  
Turbine Blade ◽  
Equivalent Stress ◽  
Three Dimensional ◽  
Maximum Equivalent Stress ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Element Method

As the main bearing part in a turbine blade, the root carries most of the loads of the whole blade. The improvement of the root structure can be used to enhance the operation reliability of steam turbine. The research on design optimization for double-T root and rim of a turbine blade was conducted by three-dimensional finite element method. Based on the APDL (ANSYS parametric design language), a multi-variable parametric model of the double-T root and rim was established. Twelve characteristic geometrical variables of the root-rim were optimized to minimize the maximum equivalent stress. The optimal structure of the double-T root-rim is obtained through the optimization. Compared with the original structure, the equivalent stress level of the root and rim has a significant reduction. Specifically, the maximum equivalent stress of root and rim reduces by 14.25% and 13.59%, respectively.

Structural integrity—whose responsibility?

2003 ◽  
Vol 217 (1) ◽  
pp. 1-21 ◽  
Author(s):  
K J Miller
Keyword(s):  
Structural Integrity ◽  
Three Dimensional ◽  
Environmental Damage ◽  
Computer Assisted ◽  
Focused Attention ◽  
Great Cost ◽  
Design Engineers ◽  
Dimensional Finite Element ◽  
The Uk ◽  
Three Dimensional Finite Element

Structural Integrity (SI) as a single distinct subject has now come of age. It has grown, sometimes painfully, through the activities of many different engineering and scientific disciplines, numerous professional institutions, separate industrial organizations, several university engineering departments and national and international societies. An accelerated impetus has been derived from severe engineering problems and accidents, some of which are briefly reviewed. In the UK and elsewhere the numerous but separate disciplines initially involved in SI have each made valuable contributions. Engineers and scientists attempted to solve practical problems, but without accurate knowledge of the applied stress levels. They were followed by metallurgists, who focused attention on a materials microstructure. Design engineers and manufacturers were unable to incorporate defects of the order of grain size, or less, into their calculations. All were eventually assisted by two important developments. First came the rapid advances in two-and three-dimensional finite element analyses of stress distributions in complex-shaped geometries, and second, the study of cracks by elastic and then elastic-plastic fracture mechanics. When combined, these computer-assisted developments focused attention on the all-important synergistic parameter a. En-route to this improved state of affairs several alternative approaches were investigated to quantify the SI of structures, components and materials, many of these alternatives effectively delaying progress for many years, at great cost. Although the UK has made numerous positive contributions to SI investigations, sometimes due to unfortunate although avoidable accidents, of which many recent incidents are well-documented, future pitfalls and false trails have to be avoided wherever and whenever possible. To achieve this, individual discipline approaches now need to be better integrated at national and international levels. The increasing complexity of engineering components and structures intended to work at higher temperatures, in more aggressive environments, and with greater efficiency, will demand a higher degree of synthesis of effort. Society will demand nothing less Failures due to inappropriate and/or incorrect SI assessments leading to increasing costs to the nation in terms of human, animal and plant life, environmental damage to land sea and air, disruption to societal activities, not to mention the associated Government-sourced budget losses, need to be dramatically reduced. By looking at some industry-university collaborations in SI studies, it is hoped that the issues raised in this lecture will help in plotting the way forward and answering the question ‘Structural Integrity-whose responsibility?’

Stress Distribution of the Variable Dynamic Loading in the Dental Implant: A Three-Dimensional Finite Element Analysis

2017 ◽  
Vol 31 ◽  
pp. 44-52 ◽  
Author(s):  
Noureddine Djebbar ◽  
B. Serier ◽  
Bel Abbès Bachir Bouiadjra
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Dynamic Loading ◽  
Equivalent Stress ◽  
Three Dimensional ◽  
The Finite Element Method ◽  
Element Analysis ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Chewing Activity

Stable osseointegration between implant threads and the surrounding marginal bone provides the mechanical base of an implant for daily chewing activity. The contact area of implant-bone interfaces and the concentrated stresses on the marginal bones are principal concerns of implant designers. In this work we numerically analyze by the finite element method the distribution of the equivalent stress and their level in the bone the most fragile element of the dental prosthesis. Each set of the model contained a crown, framework, abutment, implant and bone, subjected to variable dynamic loading according to time.

Helical Steam Generator Tubes Containing Crack Under External Pressure: A Review of Applicability for Existing Integrity Evaluation Method

2011 ◽  
Author(s):  
Tae-Young Ryu ◽  
Han-Beom Seo ◽  
Jong-Min Kim ◽  
Jae-Boong Choi ◽  
Young-Jin Kim ◽  
...  
Keyword(s):  
Fracture Mechanics ◽  
Steam Generator ◽  
Evaluation Method ◽  
Crack Opening ◽  
Three Dimensional ◽  
External Pressure ◽  
Steam Generator Tube ◽  
Integrity Assessment ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

For integrity assessment of structure containing crack, evaluation method based on fracture mechanics such as linear-elastic and elastic-plastic fracture mechanics has been relatively common method and becoming more widespread. However, it can be used only if the crack opening or tearing is occurred. If the crack exists on the piping components subjected to internal pressure, net-section stress is occurred in the direction on crack opening no matter where crack locate. On the contrary to this, if the external pressure is applied to piping components, net-section stress is occurred opposite direction and it is expected crack opening not to be occur. The subject of this study is SMART steam generator tube which is designed as helical geometrical feature and to be pressurized outside. Three dimensional finite element analyses are carried out to investigate crack behavior under external pressure considered various crack geometries and locations. Furthermore, the possibility of failure of SMART steam generator tube under design pressure is investigated.

A Three-Dimensional Finite Element Stress Analysis and Strength Prediction of CFRP Adhesive Laminated Plates Subjected to Static and Impact Out-of-Plane Loadings

2009 ◽  
Author(s):  
Yukiya Noshita ◽  
Toshiyuki Sawa ◽  
Yuya Omiya
Keyword(s):  
Equivalent Stress ◽  
Three Dimensional ◽  
Laminated Plates ◽  
Stress Distributions ◽  
Maximum Value ◽  
Out Of Plane ◽  
Dimensional Finite Element ◽  
Von Mises Equivalent Stress ◽  
Von Mises ◽  
Three Dimensional Finite Element

Stress distributions in CFRP adhesive laminated plates subjected to static and impact out-of-plane loadings are analyzed using a three-dimensional finite-element method (FEM). For establishing an optimum design method of the laminated plates, the effects of some factors are examined. As the results, it is found that the maximum value of the von Mises equivalent stress σ eqv occurs at the edge of the CFRP’s interfaces. The maximum value of interface shear stress r i at CFRP interface decreases as the reinforced Young’s modulus and the thickness increases. However, the maximum value of σ eqv at the adhesive layer decreases as the reinforced Young’s modulus and the thickness decreases. In addition, the maximum value of r i at the CFRP’s interface of lower reinforced laminates under impact loadings shows opposite characteristics to those under static loadings. For verification of the FEM calculations, experiments were carried out to measure the strains at the interfaces and the laminates plates strengths. Concerning strain and strength prediction based on von Mises equivalent stress, fairly good agreements were found between the numerical and the experimental results. The FEM results of impacted strain are in fairly good consistent with the measured results. Discussion is made on the effects of some factors on interface stress distributions.

scholarly journals A New Technique for Intergranular Crack Formation in Alloy 600 Steam Generator Tubing

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Tae Hyun Lee ◽  
Il Soon Hwang ◽  
Han Sub Chung ◽  
Jang Yul Park
Keyword(s):  
Steam Generator ◽  
Three Dimensional ◽  
Potential Drop ◽  
Crack Size ◽  
Element Analysis ◽  
Current Test ◽  
Dimensional Finite Element ◽  
Integrity Management ◽  
A New Technique ◽  
Three Dimensional Finite Element

For the integrity management of steam generator (SG) tubes, nondestructive evaluation performed using eddy current test (ECT) is necessary in the assessment. The reliability of ECT evaluation is dependent on the accuracy of ECT for various kinds of defects. For basic calibration and qualification of these techniques, cracked SG tube specimens having mechanical and microstructural characteristics of intergranular cracks in the field are needed. To produce libraries of laboratory-degraded SG tubes with intergranular cracks, a radial denting method was explored for generating inside diameter and outside diameter axial cracks by three-dimensional finite element analysis and experimental demonstration. The technique is proven to be applicable for generating axial cracks with long and shallow geometries as opposed to the semicircular cracks typically obtained by the internal-pressurization method. In addition, a direct current potential drop method with array probes was developed for accurate monitoring and controlling of crack size and shape. By these methods, long and shallow intergranular axial cracks more typical of actual degraded SG tubes were successfully produced.

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