Determination of the Interaction Between Primary and Secondary Stresses Using an Idealised Model

2012 ◽  
Author(s):  
Graeme Horne ◽  
David J. Smith
Keyword(s):  
Residual Stress ◽  
Structural Integrity ◽  
New Approach ◽  
Integrity Assessment ◽  
Primary Stress ◽  
Reference Stress ◽  
Idealised Model ◽  
The Uk

When conducting an assessment of the integrity of a structure the user is directed to classify the stresses as either primary stress or secondary stress. Residual stresses are usually classified as secondary stresses unless they exhibit significant elastic follow-up. In this paper the authors have first summarised current methods and origins of the UK R6 structural integrity assessment methodology for combining primary and secondary stresses. Then, using an idealised model, a new approach has been developed to examine how fixed-displacement secondary stresses interact and redistribute; this model permits a combined reference stress to be determined directly. This combined reference stress is intrinsically linked to the effect of elastic follow-up within the structure and provides a direct measure of how the residual stress relaxes between the extremes of fixed-load and fixed-displacement conditions. The results have been compared with the existing approaches in R6 and it has been demonstrated that the R6 method can be either conservative or non-conservative, depending on the degree of elastic follow-up and residual stress redistribution.

scholarly journals Use of Elastic Follow-Up to Study the Effect of Displacement Controlled Loading on Plastic Collapse Pressures for Circumferentially Cracked Pipes

2015 ◽  
Author(s):  
Guiyi Wu ◽  
David J. Smith ◽  
Martyn J. Pavier
Keyword(s):  
Residual Stress ◽  
Long Range ◽  
Structural Integrity ◽  
Axial Displacement ◽  
Plastic Collapse ◽  
Integrity Assessment ◽  
Circumferential Crack ◽  
Displacement Condition ◽  
Global Collapse

Structural integrity assessments of pressurised pipes consider plastic collapse as a potential failure mode. This paper uses finite element analysis to explore the effect of the pipe end boundary conditions on the collapse pressure. Two end conditions are considered: a fixed axial load and a fixed axial displacement. The fixed axial displacement condition represents a long-range axial residual stress. In the R6 structural integrity assessment procedure long-range residual stress is associated with elastic follow-up. However, no guidance is given on whether the level of elastic follow-up is sufficient to justify treating long-range residual stress as a primary stress. In this paper, a method is proposed to estimate elastic follow-up of an internally pressurised pipe containing a fully circumferential crack. It is found that the elastic follow-up is related to the length of the pipe. A short pipe that contains a fully circumferential crack, subjected to a displacement induced axial stress, has a global collapse that is not modified by the fixed displacement condition. The short pipe corresponds to a small elastic follow-up factor, Z. However, as the elastic follow-up factor increases, the presence of long-range residual stress starts to make a contribution to global collapse. When elastic follow-up is significant, a long-range residual stress has the same effect on global collapse as does a mechanical stress.

Structural Integrity Assessment of Steam Generator Tubes Using a New EPRI Statistical Approach

2002 ◽  
Author(s):  
Carlos Alexandre de Jesus Miranda ◽  
Miguel Mattar Neto
Keyword(s):  
Steam Generator ◽  
Wall Thickness ◽  
Nuclear Power ◽  
Structural Integrity ◽  
Tube Wall ◽  
New Approach ◽  
Inconel 600 ◽  
Integrity Assessment ◽  
Tube Wall Thickness ◽  
Uniform Tube

A fundamental step in tube plugging management of a Steam Generator (SG), in a Nuclear Power Plant (NPP), is the tube structural integrity evaluation. The degradation of SG tubes may be considered one of the most serious problems found in PWRs operation, mainly when the tube material is the Inconel 600. The first repair criterion was based on the degradation mode where a uniform tube wall thickness corrosion thinning occurred. Thus, a requirement of a maximum depth of 40% of the tube wall thickness was imposed for any type of tube damage. A new approach considers different defects arising from different degradation modes, which comes from the in-service inspections (NDE) and how to consider the involved uncertainties. It is based on experimental results, using statistics to consider the involved uncertainties, to assess structural limits of PWR SG tubes. In any case, the obtained results, critical defect dimensions, are within the regulatory limits. In this paper this new approach will be discussed and it will be applied to two cases (two defects) using typical data of SG tubes of one Westinghouse NPP. The obtained results are compared with ‘historical’ approaches and some comments are addressed from the results and their comparison.

scholarly journals Use of a Novel Resistive Strain Sensor Approach in an Experimental and Theoretical Study Concerning Large Spherical Storage Tank Structure Behavior During Its Operational Life and Pressure Tests

Sensors ◽  
2020 ◽  
Vol 20 (2) ◽  
pp. 525
Author(s):  
Virgil Florescu ◽  
Stefan Mocanu ◽  
Laurentiu Rece ◽  
Robert Ursache ◽  
Nicolae Goga ◽  
...  
Keyword(s):  
Storage Tank ◽  
Structural Integrity ◽  
Real Life ◽  
Fem Simulation ◽  
Strain Sensor ◽  
Sensor Data ◽  
New Approach ◽  
Integrity Assessment ◽  
Operational Life ◽  
Large Spherical

This paper introduces a new method for the use of tensor-resistive sensors in large spherical storage tank equipment (over 12,000-mm diameters). We did an experiment with 19 petroleum or ammonia product sphere-shaped storage tanks with volumes of 1000 and 1800 cubic meters, respectively. The existing literature only contains experiments based on sensors for tanks with diameters no larger than 600 mm. Based on a number of resistive strain sensor measurements on large spherical pressurized vessels regarding structural integrity assessment, the present paper is focused on the comparison between "real-life" obtained sensor data versus finite element method (FEM) simulation results. The present paper is structured in three parts and examines innovative directions: the use of the classic tensor-resistive sensors in a new approach concerning large structural equipment; an original 3D modeling method with the help of the FEM; and conclusions with possible implications on the regulations, design, or maintenance as a result of the attempt of mutual validation of the new methods previously mentioned.

Comparison of R5 and ASME NH Creep-Fatigue Damage Assessment Methodologies

2013 ◽  
Author(s):  
Michael Sheridan ◽  
David Knowles ◽  
Oliver Montgomery
Keyword(s):  
Fatigue Damage ◽  
Structural Integrity ◽  
Temperature Response ◽  
Creep Damage ◽  
Basic Principles ◽  
Metallic Structures ◽  
Reference Stress ◽  
Creep Fatigue ◽  
Design Generation

The R5 volume 2/3 procedures [1] were developed by British Energy (now EDF Energy) to assess the high temperature response of uncracked metallic structures under steady state or cyclic loading. They contain the basic principles of: • Application of reference stress methods • Consideration of elastic follow up • A ductility exhaustion approach to calculate creep damage accumulation. These considerations represent a fundamental distinction from ASME BPVC Section III, Subsection NH [2]. This paper draws on literature review and experience to explain the principal differences in the limits of application, cycle construction and damage calculation between these codes/procedures focusing on creep-fatigue damage determination. The implications of the differences between the codes and standards are explored. The output of this work is aimed at two groups of structural integrity engineers; those using these codes and standards to assess existing conventional and nuclear plant, and also those looking to ASME and R5 to design Generation IV PWRs with design temperatures much elevated from those of Generation III and III+. The conclusions from this paper offer some practical guidance to structural integrity engineers which may assist in selecting the more appropriate procedure to assess creep-fatigue damage for a particular situation.

Determination of optimum tuber planting density for production of tubers in processing ware grades in the potato variety Record

1990 ◽  
Vol 114 (1) ◽  
pp. 11-18 ◽  
Author(s):  
D. C. E. Wurr ◽  
J. R. Fellows ◽  
R. A. Sutherland ◽  
E. J. Allen
Keyword(s):  
Seed Tuber ◽  
Planting Density ◽  
Potato Tubers ◽  
New Approach ◽  
Seed Tubers ◽  
Series Of Experiments ◽  
Number Of Stems ◽  
The Uk ◽  
Seed Tuber Weight

SUMMARYA series of experiments examining the influences of size and spacing of planted potato tubers (‘seed’ tubers) on tuber yields was conducted at four sites in the UK in 1982–84. A new approach to data analysis was used to estimate the optimum tuber planting density for different ware grades. The optimum density, which maximized returns, decreased with increasing seed tuber weight and ratio of seed-tuber cost to ware value and with lower than average total tuber yields. Changing the required ware grade from 40–65 mm to 40–80 mm had a minimal effect on the optimum tuber planting density.Optimum tuber planting densities were lower than in published recommendations but this disparity appeared to be accounted for by differences in the number of stems produced by each planted tuber. There was some evidence that, with lower seed-tuber weights, the optimum planting density differed with site and that at optimum economic densities small and medium seed tubers outyielded large seed tubers.

Standardisation on Measurement and Interpretation of Residual Stress Data

2019 ◽  
Author(s):  
Ali Mirzaee-Sisan ◽  
P. John Bouchard ◽  
Foroogh Hosseinzadeh
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Practice Guidelines ◽  
Structural Integrity ◽  
Good Practice ◽  
Critical Assessment ◽  
Numerical Prediction ◽  
Specific Technique ◽  
Integrity Assessment

Abstract This paper highlights many unanswered questions relating to the characterisation of residual stresses in weldments and their treatment in engineering critical assessment and fitness for service assessment codes and standards. The need for an overarching standardisation framework is identified which goes beyond developing good practice guidelines for numerical prediction or measurement using a specific technique. The framework should cover all uncertainties and possible errors in measuring, simulating and interpreting residual stress in the context of structural integrity assessment.

Structural Integrity Assessment of WWER Internals on Stress Corrosion Cracking Criterion

2009 ◽  
Author(s):  
Valentina Fedorova ◽  
Boris Margolin
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Structural Integrity ◽  
Corrosion Cracking ◽  
Intergranular Stress Corrosion ◽  
Integrity Assessment ◽  
Dose Curve ◽  
Stress Damage ◽  
Intergranular Stress Corrosion Cracking

Stress-damage dose curve (SDDC) is introduced on the basis of the analysis of experimental data on susceptibility to intergranular stress corrosion cracking (IGSCC) of irradiated stainless steels (SS). Approaches to determination of the SDDC parameters are considered. Based on SDDC calculative procedure for estimation of reactor vessel internals (RVI) lifetime by criterion of initiation crack due to IGSCC is proposed.

An Energy-Based Residual Stress Field Reconstruction Approach Using Limited Measurements

2015 ◽  
Author(s):  
H.-B. Liu ◽  
Y.-P. Li ◽  
Y.-Q. Wang ◽  
X.-J. Sheng
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Stress Field ◽  
Structural Integrity ◽  
Spline Interpolation ◽  
Residual Stress Field ◽  
Strain Compatibility ◽  
Integrity Assessment ◽  
Field Reconstruction ◽  
Initial Stress Field

To characterize the residual stress distribution is very crucial for workpiece fatigue lifetime and structural integrity assessment. An energy-based residual stress field reconstruction approach using limited measurements is proposed. Firstly, the Ferguson spline interpolation technique is employed as the stress interpolation base of the 2-order stress tensor. Then, an initial stress field can be reconstructed using the overall boundary conditions by minimizing strain energy. Further, the stress distribution is modified according to strain compatibility equation. At last, a typical stress unit from the artificial stress field constructed by FEM, was picked up as an input set to verify the validation of the developed model and algorithm numerically. It was demonstrated that the energy-based scheme was efficient and reliable to reconstruct the residual stress field from limited measurements.

Application of the Linear Matching Method to the Integrity Assessment for the High Temperature Response of Structures

2003 ◽  
Author(s):  
Haofeng Chen ◽  
Alan R. S. Ponter
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Temperature Response ◽  
Assessment Method ◽  
Life Assessment ◽  
Residual Stress Field ◽  
Matching Method ◽  
Integrity Assessment ◽  
Linear Matching Method

The paper describes a first attempt to produce a complete system of calculations that cover the entire range of assessments required in the Life Assessment method R5 based on a new programming method, the Linear Matching Method, and using shakedown and related concepts. We show that two solutions types are possible, the first assuming a constant residual stress field that provides shakedown and related limits. The second method involves the evaluation of the amplitude of the changing residual stress field. This provides the first stage for the ratchet limit and the amplitude of plastic strain. By adaptation the elastic follow-up factor corresponding to creep dwell periods may also be evaluated.

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