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.

Analysis on Fracture Toughness of the L415MS/N08825 Bimetallic Composite Pipe Welded Joint

2016 ◽  
Vol 850 ◽  
pp. 1010-1015
Author(s):  
Bin Wang ◽  
Bo Bo Lei ◽  
Liang Wang ◽  
Ming Xu
Keyword(s):  
Fracture Toughness ◽  
Fracture Surface ◽  
Room Temperature ◽  
Welded Joint ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
X Ray ◽  
Bimetallic Composite ◽  
Composite Pipe ◽  
Crack Tip Opening

Crack tip opening displacement (CTOD) tests were conducted on the weld and heat affected zone (HAZ) of L415MS/N08825 bimetallic composite pipe welded joint according to BS7448, ISO12135(2002) and ISO15653(2010) standards at room temperature. The fracture toughness of weld and HAZ were studied and analyzed. The fracture surface and inclusions were characterized using scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDS), respectively. The results showed that the average CTOD value of the weld was less than HAZ, CTOD values of HAZ exhibited larger discrete, which was mainly caused by Pop-in effect in P-V curve of HAZ samples. CTOD value of sample with Pop-in effect dropped several times than sample without Pop-in effect. The fracture surfaces of the weld and HAZ showed tough fracture to a certain extent, and the fracture surface of HAZ sample with Pop-in effect exhibited significant quasi-cleavage feature.

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.

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.

Impact of Metallic Foam’s Microstructure to its Mechanical Property

2013 ◽  
Vol 634-638 ◽  
pp. 2808-2812
Author(s):  
Zhu Feng Sun ◽  
Ling Yun Xie
Keyword(s):  
Fracture Toughness ◽  
Cell Structure ◽  
Crack Tip ◽  
Metallic Foam ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Metal Material ◽  
Loading Mode ◽  
Foam Metal ◽  
Material Fracture

Explored the influence of pore structure of foam metal material on mechanical behavior of fracture. Discuss fracture toughness of several different micro geometric structure of foam metal material with finite element method. The author's calculations showed, microstructure and loading mode has an important effect on the fracture toughness of the foam metal material. due to ignoring the effects of cell structure on the mechanical properties of materials, the classic fracture toughness criterion -crack tip opening displacement (COD) is incomplete, it would be more efficient to take opening displacement change rate of the crack-tip as the parameter to characteristic the metallic foam material fracture toughness.

Analysis on Critical CTOD of Long-Term Used Penstock

2017 ◽  
Vol 741 ◽  
pp. 57-62
Author(s):  
Fumito Kawamura ◽  
Masazumi Miura ◽  
Ryuichiro Ebara ◽  
Keiji Yanase
Keyword(s):  
Fracture Toughness ◽  
Structural Integrity ◽  
Steel Structures ◽  
Chemical Compositions ◽  
Structural Components ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Critical Crack ◽  
Crack Tip Opening

Many studies have been conducted to characterize the fracture toughness of structural steels and their welded joints. However, most studies focus on newly developed steels, and the number of studies on the fracture toughness of long-term used steels in structural components is rather limited. Furthermore, a lack of data on the fracture toughness causes difficulties in evaluating the structural integrity of existing steel structures. In this study, CTOD tests were performed to characterize the fracture toughness of penstock that has been in service for 50 years. By measuring the critical crack tip opening displacement in conjunction with analysis for chemical compositions, the characteristics of fracture toughness were investigated.

Experimental Study of Crack Propagation at the PCB/Underfill Interface due to Thermal Aging

2020 ◽  
Author(s):  
Pradeep Lall ◽  
Padmanava Choudhury ◽  
Jaimal Williamson
Keyword(s):  
Fracture Toughness ◽  
High Temperature ◽  
Flip Chip ◽  
Operating Time ◽  
Image Correlation ◽  
Beam Specimen ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Substrate Interface ◽  
2D Digital Image Correlation

Abstract Flip-Chip Ball Grid Arrays (FCBGAs) are finding applications in automotive underhood electronics for enablement of safety-critical functions. Underfills needed to reinforce flip-chip interconnects in FCBGAs need to operate reliably under sustained high temperature operation. Underfill-to-substrate interface is one of the primary failure locations under wide thermal excursions and usually a precursor to flip-chip joint failure. In order to assess the reliability in the end application, there is need for understanding the damage progression of the underfill-to-substrate interface as a function of operating time and operating temperature. In this study, the Substrate-UF interface was exposed to high temperature and the interfacial fracture toughness quantified. A three-point composite beam specimen of PCB/Underfill was fabricated to study the interface and thermally aged for periods of 10 days, 30 days, 60 days at temperatures ranging from 100°C to 150°C. Quasi-static bending was used to observe and determine interfacial delamination of the sample specimen. A 2D-Digital Image Correlation (DIC) method was also employed to understand the Crack tip opening displacement (CTOD), crack initiation and the fracture toughness, CTOD were compared with the aging schedule and temperature.

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