Recent Developments in Japanese Flaw Assessment Methods of WES 2805

2008 ◽  
Author(s):  
Yukito Hagihara ◽  
Masayoshi Kurihara ◽  
Hitoshi Yoshinari ◽  
Takashi Miyata
Keyword(s):  
Welded Joints ◽  
Large Scale ◽  
Welded Joint ◽  
Estimation Method ◽  
Assessment Methods ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Design Curve ◽  
Load Carrying ◽  
Recent Developments

The standard for the method of assessment for flaws in the welded joints of WES 2805 was first published in 1976 and was revised in 1980 and 1997. A further revision has been carried out by the technical committee of FTS in the Japan Welding Engineering Society and the revision was completed in 2007. The standard of WES 2805 is based on a CTOD (crack tip opening displacement) design curve approach for brittle fracture, and is used for the assessment of the significance of flaws in a stress concentrated region, where large scale yielding takes place. Main topics for the recent developments for flaw assessment methods are described in this paper. These are the interaction criterion of multiple flaws, fatigue crack growth laws, determination of equivalent crack length and strain due to stress concentration, estimation method of the critical CTOD from Charpy energy and proposal of partial safety factors. In order to examine the effectiveness of the standard, extensive 2-D and 3-D FE analyses are performed for various welded joints such as a load-carrying fillet welded joint, a non-load-carrying fillet welded joint and a box welded joint. Some of them are introduced in this paper. Their analytical results indicate that the present CTOD design curve method gives a reasonable evaluation.

scholarly journals Analysis on Fracture Toughness of the L360QS/N08825 Bimetallic Composite Pipe Welded Joint

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Bin Wang ◽  
Hongxia Lan ◽  
Bobo Lei
Keyword(s):  
Electron Microscopy ◽  
Fracture Toughness ◽  
Large Scale ◽  
Welded Joint ◽  
Fracture Morphology ◽  
Dislocation Slip ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Bimetallic Composite ◽  
Composite Pipe

The fracture toughness of the weld and heat-affected zone (HAZ) of the L360QS/N08825 composite pipe welded joint was evaluated by a crack tip opening displacement (CTOD) test. The fracture morphology, microstructure, and inclusion near fracture zones were observed by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive spectroscopy (EDS). The grain size and grain orientation of the crack propagation zone in the weld were investigated by electron back-scattered diffraction (EBSD). The results revealed that the average CTOD values of the weld and HAZ samples were relatively high, and a greater dispersion of CTOD values of the HAZ samples is due to the pop-in phenomenon in the P–V curve. The fracture surfaces of the weld and HAZ samples showed the characteristics of ductile fracture to a certain extent, whereas the fracture of the CTOD sample with the pop-in phenomenon exhibited a quasicleavage feature. High-density dislocation and a large number of inclusions were observed in the near fracture zone of the weld and HAZ samples. The stress concentration, caused by hindering the dislocation slip, was the main reason for microcrack formation. The existence of large-size grains and large-scale small-angle grain boundary in the weld implies that the cracks propagate toward the weld.

Experimental Study on CTOD Fracture Toughness of Welded Joints of Low Temperature Steel

2011 ◽  
Vol 328-330 ◽  
pp. 1272-1276 ◽  
Author(s):  
Zong Tao Fang ◽  
Bo Sun ◽  
Chun Run Li
Keyword(s):  
Fracture Toughness ◽  
Low Temperature ◽  
Welded Joints ◽  
Welding Process ◽  
Offshore Platform ◽  
Fracture Toughness Test ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Welding Procedure ◽  
Crack Tip Opening

According to BS7448 fracture toughness test standard, crack tip opening displacement (CTOD) for ASTM A333 Gr.6 low temperature steel which is used in offshore platform were carried out in low temperature (0°C, -29°C). Three point bending tests were conducted on the specimens, the dimension of which is B×2B (B is the thickness) and notch direction is NP. The final value of CTOD was calculated by P-V curves of both the welds and HAZ (heat affected zone). And the experimental results were analyzed and discussed in the paper. The low temperature steel welded joints show good low temperature toughness, the selected welding procedure is applied to construction of pipelines.The CTOD value of HAZ is larger than weld metal and weld is the weakest position in the whole structure. The experiment results provide an important basis for the choice of welding method and welding process parameters, ECA assessment and construction of offshore platform.

Review of Tensile Strain Capacity Prediction Models for Strain-Based Design of Pipelines

2019 ◽  
Author(s):  
Dong-Yeob Park ◽  
James A. Gianetto
Keyword(s):  
Fracture Toughness ◽  
Large Scale ◽  
Prediction Models ◽  
Failure Criteria ◽  
Small Scale ◽  
Aging Effects ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Strain Capacity ◽  
Critical Issues

Abstract In this paper, three tenile strain capacity (TSC) prediction models developed for strain-based design (SBD) of girth-welded pipelines were reviewed, together with a brief introduction of technical backgrounds of their development. Most TSC models rely on small-scale mechanical and fracture toughness measurements to estimate the TSC of pipelines. Hence, we surveyed published experimental and computational data to examine the transferability of small-scale fracture toughness measurements to large-scale pipe fractures. Lastly, some gaps and issues that were found from the review are proposed for improvement of TSC models for SBD. The critical issues found with current TSC models and SBD are (a) differences in strain measurement for full-scale pipe tests/simulations, (b) multiple crack tip opening displacement (CTOD) definitions, (c) no application of J-integral as a toughness parameter, (d) no consensus on failure criteria, and (e) inconsideration of thermal and natural strain aging effects.

Production of High-Strength and High-Toughness Steel for Offshore Structures

2003 ◽  
Author(s):  
Yoshihide Nagai ◽  
Hidenori Fukami ◽  
Hajime Inoue ◽  
Takao Nakashima ◽  
Akihiko Kojima ◽  
...  
Keyword(s):  
Welded Joints ◽  
Mass Production ◽  
Fine Particles ◽  
High Strength ◽  
Offshore Structures ◽  
Bearing Steel ◽  
Steel Plates ◽  
Carbon Equivalent ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement

By the utilization of new fine particles, steels refining the heat affected zone (HAZ) structure have been developed. This has made possible the mass-production of offshore structural steels which have high-strength of 460–500N/mm2 in yield strength (YS) and excellent crack-tip opening displacement (CTOD) properties. These newly developed steels for offshore structures have been mass-production to over 45,000 tons. The new particles are dispersed finely in the developed steels and show a strong pinning effect. The newly developed steels also use the intragranular ferrite (IGF) like titanium oxide bearing steel (TiO steel). In mass-production heats, γ grain size is restricted below 200 μm under conditions of 1400°C for 60 seconds. The improvement of HAZ toughness and the utilization of the thermo-mechanical control process (TMCP) has restrained the increase in carbon equivalent (Ceq,PCM) far as possible. By application of these technologies, it has been possible to mass-produce steels with high-strength, excellent CTOD properties and good weldability. As for steel plates of YS500N/mm2, the production of steel plates up to 70mm in thickness was carried out. The properties of welded joints for the 70mm-thick plates of YS500N/mm2 steel have been evaluated under heat input in 0.7kJ/mm of flux-cored are welding (FCAW) and 3.5kJ/mm of sub-merged arc welding (SAW). They have shown excellent CTOD and Charpy impact properties at welded joints; and have moreover indicated good weldability when PCM has been restricted to 0.22% or lower.

scholarly journals Multivariate Analysis to Relate CTOD Values with Material Properties in Steel Welded Joints for the Offshore Wind Power Industry

Energies ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 4001 ◽  
Author(s):  
Presno Vélez ◽  
Sánchez ◽  
Menéndez Fernández ◽  
Fernández Muñiz
Keyword(s):  
Multivariate Analysis ◽  
Welded Joints ◽  
Material Properties ◽  
Crack Tip ◽  
Offshore Structures ◽  
Offshore Wind ◽  
Multivariate Techniques ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Wide Range

The increasingly mechanical requirements of offshore structures have established the relevance of fracture mechanics-based quality control in welded joints. For this purpose, crack tip opening displacement (CTOD) at a given distance from the crack tip has been considered one of the most suited parameters for modeling and control of crack growth, and it is broadly used at the industrial level. We have modeled, through multivariate analysis techniques, the relationships among CTOD values and other material properties (such as hardness, chemical composition, toughness, and microstructural morphology) in high-thickness offshore steel welded joints. In order to create this model, hundreds of tests were done on 72 real samples, which were welded with a wide range of real industrial parameters. The obtained results were processed and evaluated with different multivariate techniques, and we established the significance of all the chosen explanatory variables and the good predictive capability of the CTOD tests within the limits of the experimental variation. By establishing the use of this model, significant savings can be achieved in the manufacturing of wind generators, as CTOD tests are more expensive and complex than the proposed alternatives. Additionally, this model allows for some technical conclusions.

Study on CTOD Fracture Toughness of Welded Joint of X80 Marine Drilling Riser

2011 ◽  
Vol 228-229 ◽  
pp. 1163-1168 ◽  
Author(s):  
Peng Wang ◽  
Mei Juan Hu ◽  
En Dang
Keyword(s):  
Heat Treatment ◽  
Welded Joint ◽  
Center Line ◽  
Crack Tip Opening Displacement ◽  
Treatment Technology ◽  
Opening Displacement ◽  
Three Point Bending ◽  
Heat Treatment Technology ◽  
Crack Tip Opening ◽  
Made In

This document demonstrates CTOD (crack tip opening displacement) tests at0°Cof welded joint in X80 marine drilling riser in accordance with the BS 7448 standard. The three point bending specimens are made in the weld center line and heat affected zone for the butt-welded joint in Φ533×25.4mm X80 marine drilling riser respectively according to the requirement of the standard. The CTOD testing results are discussed in detail, which can provide the basic to evaluate and optimize the welding and heat treatment technology of marine drilling riser.

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