scholarly journals Effects of manufacturing plastic prestrains found on calendered and UOE pipes and pressure vessels on structural integrity assessments regarding fatigue crack growth and LBB

2018 ◽  
Vol 13 ◽  
pp. 1915-1923 ◽  
Author(s):  
Rodrygo Figueiredo Moço ◽  
Fábio Gonçalves Cavalcante ◽  
Gustavo Henrique Bolognesi Donato
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Structural Integrity ◽  
Pressure Vessels ◽  
Integrity Assessments

Structural Integrity Assessment of Doel 3 and Tihange 2 RPVs: Fatigue Crack Growth Analysis of Hydrogen Flakes

2017 ◽  
Author(s):  
Valéry Lacroix ◽  
Pierre Dulieu
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Nuclear Power ◽  
Power Plants ◽  
Structural Integrity ◽  
Pressure Vessels ◽  
Simplified Approach ◽  
Integrity Assessment ◽  
The Core

During the 2012 outages at Doel 3 and Tihange 2 Nuclear Power Plants, a large number of quasi-laminar indications were detected, mainly in the lower and upper core shells of the Reactor Pressure Vessels (RPVs). The observed indications could subsequently be attributed to hydrogen flaking induced during the component manufacturing process. As a consequence, both units remained core unloaded pending the elaboration of an extensive Safety Case demonstrating that they can be safely operated. The Structural Integrity Assessment of the RPVs, through the Flaw Acceptability Assessment, aimed at demonstrating that the identified indications do not jeopardize the integrity of the reactor vessel in all operating modes, transients and accident conditions. This demonstration has been done on the basis of a specific methodology inspired by the ASME B&PV Code Section XI procedure but adapted to the nature and the number of indications found in the Doel 3 and Tihange 2 RPVs. As requested by Article IWB-3610(a) of ASME B&PV Code Section XI, one of the parts that have to be addressed through the Flaw Acceptability Assessment is the Fatigue Crack Growth (FCG) Analysis of the flaws in the core shells until the end-of-service lifetime of the RPVs. Due to the large number of flaws in the core shells, a specific methodology has been developed in order not to perform the FCG Analysis of each flaw separately. The paper describes this simplified approach aiming at distributing the flaws according to their inclination and at defining envelope flaws covering the actual flaws to carry out FCG Analysis. Furthermore, the paper highlights and quantifies the conservatisms of this analysis leading finally to demonstrate that the FCG of hydrogen flakes is not a concern in Doel 3 and Tihange 2 RPVs.

Pre-Strain Effects on Mixed-Mode Fatigue Crack Propagation Behaviour of the P355NL1 Pressure Vessels Steel

2018 ◽  
Author(s):  
João Ferreira ◽  
José A. F. O. Correia ◽  
Grzegorz Lesiuk ◽  
Sergio Blasón González ◽  
Maria Cristina R. Gonzalez ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Mixed Mode ◽  
Pressure Vessels ◽  
Mode I ◽  
Pure Mode

Pressure vessels and piping are commonly subjected to plastic deformation during manufacturing or installation. This pre-deformation history, usually called pre-strain, may have a significant influence on the resistance against fatigue crack growth of the material. Several studies have been performed to investigate the pre-strain effects on the pure mode I fatigue crack propagation, but less on mixed-mode (I+II) fatigue crack propagation conditions. The present study aims at investigating the effect of tensile plastic pre-strain on fatigue crack growth behavior (da/dN vs. ΔK) of the P355NL1 pressure vessel steel. For that purpose, fatigue crack propagation tests were conducted on specimens with two distinct degrees of pre-strain: 0% and 6%, under mixed mode (I+II) conditions using CTS specimens. Moreover, for comparison purposes, CT specimens were tested under pure mode I conditions for pre-strains of 0% and 3%. Contrary to the majority of previous studies, that applied plastic deformation directly on the machined specimen, in this work the pre-straining operation was carried out prior to the machining of the specimens with the objective to minimize residual stress effects and distortions. Results revealed that, for the P355NL1 steel, the tensile pre-strain increased fatigue crack initiation angle and reduced fatigue crack growth rates in the Paris region for mixed mode conditions. The pre-straining procedure had a clear impact on the Paris law constants, increasing the coefficient and decreasing the exponent. In the low ΔK region, results indicate that pre-strain causes a decrease in ΔKth.

Fatigue Crack Growth Properties of 16MnR and 316L Steels at High Temperature

2005 ◽  
Author(s):  
Zengliang Gao ◽  
Weiming Sun ◽  
Weiya Jin ◽  
Ying Wang ◽  
Fang Zhang
Keyword(s):  
Fatigue Crack ◽  
High Temperature ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Rates ◽  
Fatigue Cracks ◽  
Pressure Vessels ◽  
Effect Of Temperature ◽  
Growth Properties ◽  
Crack Growth Rates

Fatigue failures often take place in high temperature pressure vessels and equipment because of fluctuation of pressure and temperature. Fatigue crack growth properties of materials at high temperatures are very important for safety assessment of high temperature equipment. A series of fatigue crack growth tests were carried out, and fatigue crack growth rates were determined at 25∼500°C for typical steels 316L and 16MnR. The laws of fatigue crack growth of two materials at different temperatures and the effect of temperature on fatigue crack growth rates were studied. The results show that the crack growth rates increase with temperature for 316L steel. Both the exponent n and constant C for Paris law change with temperature. The fatigue cracks of 16MnR propagate at 150 °C and 300 °C more slowly than at room temperature and 425 °C. The fatigue crack growth rate at 425 °C is the highest for temperature range of 25–425 °C.

Fatigue Growth Prediction of Internal Surface Cracks in Pressure Vessels

1998 ◽  
Vol 120 (1) ◽  
pp. 17-23 ◽  
Author(s):  
X. B. Lin ◽  
R. A. Smith
Keyword(s):  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Front ◽  
Internal Surface ◽  
Pressure Vessels ◽  
Surface Cracks ◽  
Elliptical Shape ◽  
Set Of Points

Fatigue crack growth was numerically simulated for various internal surface cracks with initially either semi-elliptical or irregular crack fronts. The simulation was directly based on a series of three-dimensional finite element analyses from which the stress intensity factors along the front of growing cracks were estimated. The fatigue crack growth law obtained from small laboratory specimens was incrementally integrated at a set of points along the crack front, and a new crack front was then re-established according to the local advances at this set of points by using a cubic spline curve. This method enabled the crack shape to be predicted without having to make the usual assumption of semi-elliptical shape. Fatigue analysis results are presented and discussed for fatigue shape developments and deviations from the semi-elliptical shape, aspect ratio changes, stress intensity factor variations during crack growth, and fatigue life predictions. Some of the results were also compared with those obtained by two simplified methods based on one and two degree-of-freedom models, respectively.

Structural Integrity Analyses for a Preemptive Weld Overlay in a Pressurizer Surge Nozzle

2013 ◽  
Author(s):  
Ru-Feng Liu ◽  
Chin-Cheng Huang
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Structural Integrity ◽  
Piping System ◽  
Weld Overlay ◽  
Asme Code ◽  
Overlay Welding ◽  
Usage Analysis ◽  
Weld Distortion

This paper is to present the structural integrity analyses for a preemptive weld overlay in a pressurizer surge nozzle. Based on ASME Code Case N-504-3 and MRP-169, the full structural weld overlay sizing calculation, residual stress improvement analysis, shrinkage evaluation, fatigue crack growth analysis and fatigue usage analysis were performed. After weld overlay installation, the welded nozzle structure has to be analyzed to measure the improvement in residual stresses around the inner surface of the original weld. The residual compressive stress distribution is thus addressed to be resistant to subsequent stress corrosion, the initiation of cracking, and the further crack growth. To ensure the structural integrity of the attached piping system, the weld induced displacement is measured and transformed to temperature gradient to simulate the shrinkage after overlay welding and to analyze the post-weld distortion and stress situations. Based on the further comparisons of fatigue crack growth with all of system operating cycles, two surface cracks in the original weld are conservatively postulated. Additionally, both the stress limits and cumulative fatigue usages of the nozzle with weld overlay are evaluated to meet the design requirements of ASME Code Section III. The present analysis results confirm the effectiveness of the procedure for analyzing the structural integrity of a nozzle with weld overlay.

The Potential for Non-Conservative Results From the Probabilistic Fracture Mechanics Analyses Is Assessed Based on the Collected Observation of Fatigue Cracks in Offshore Steel Structures

2017 ◽  
Author(s):  
Ole Tom Vårdal
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Structural Integrity ◽  
Fatigue Cracks ◽  
Steel Structures ◽  
Lessons Learned ◽  
Probabilistic Methods ◽  
Growth Potential

In structural integrity management, it is essential to know the fatigue crack growth potential. The lessons learned from use of refined fatigue analyses, fracture mechanics and probabilistic methods for platforms in-service are presented. For ageing offshore units of semi-submersible design, the inspection history of more than 20 000 NDT inspections and detection of close to 1000 fatigue cracks, are used in this study. These experience data are used to assess the potential for Non-conservative estimate for the fatigue crack growth potential.

Fracture and Fatigue Tolerant Steel Pressure Vessels for Gaseous Hydrogen

2010 ◽  
Author(s):  
Kevin A. Nibur ◽  
Chris San Marchi ◽  
Brian P. Somerday
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Rates ◽  
Maximum Load ◽  
Pressure Vessels ◽  
Hydrogen Gas ◽  
R Ratio ◽  
History Of ◽  
Crack Growth Rates

Fatigue crack growth rates and rising displacement fracture thresholds have been measured for a 4130X steel in 45 MPa hydrogen gas. The ratio of minimum to maximum load (R-ratio) and cyclic frequency was varied to assess the effects of these variables on fatigue crack growth rates. Decreasing frequency and increasing R were both found to increase crack growth rate, however, these variables are not independent of each other. Changing frequency from 0.1 Hz to 1 Hz reduced crack growth rates at R = 0.5, but had no effect at R = 0.1. When applied to a design life calculation for a steel pressure vessel consistent with a typical hydrogen trailer tube, the measured fatigue and fracture data predicted a re-inspection interval of nearly 29 years, consistent with the excellent service history of such vessels which have been in use for many years.

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