Study on the Failure Mechanism of Burn-Through During In-Service Welding on Gas Pipelines

2019 ◽  
Vol 141 (2) ◽  
Author(s):  
Wu Qian ◽  
Wang Yong ◽  
Han Tao ◽  
Wang Hongtao ◽  
Gu Shiwei ◽  
...  
Keyword(s):  
Finite Element ◽  
High Temperature ◽  
Grain Boundaries ◽  
Failure Mechanism ◽  
Exploratory Study ◽  
Initial Position ◽  
Cooling Stage ◽  
Melted Zone ◽  
Brittle Rupture ◽  
Burn Through

We conclude on the governing mechanism of burn-through and identify the area of highest risk for burn-through occurrence due to a specific combination of loading in this area. In order to investigate the mechanism of burn-through during in-service welding, an exploratory study combining both experiments and finite element simulations was presented. Combined with the theory of high-temperature failure, the initial position of burn-through and its mechanism were discussed. The results showed that burn-through was a kind of intergranular brittle rupture happened at the cooling stage of in-service welding. It started from the partially melted zone, and the cracks expanded along the weakened grain boundaries. When the cracks eventually penetrated to the inner wall, burn-through happened.

Simulation of the Effect of Sintering and Interface on the Failure Mechanism of Thermal Barrier Coatings

2015 ◽  
Vol 817 ◽  
pp. 764-771
Author(s):  
Wei Chen ◽  
Jian Guo Zhu ◽  
Gui Lan Chai
Keyword(s):  
Finite Element ◽  
Failure Mechanism ◽  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Great Influence ◽  
Element Model ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Cooling Stage ◽  
The Finite Element Model

Thermal barrier coatings (TBC) are mainly composed of four layers: top coat (TC), thermal barrier oxidation (TGO), bond coat (BC) and substrate (SUB). The finite element model is used to investigate the failure mechanism of TBC. The influences of sintering of TC and the properties of TGO/BC interface on the stress S22 were considered. The numerical results show that sintering of TC can change the tendency of the stress S22 within TC from peak to valley along the TC/TGO interface; When considering the cohesive behavior of TGO/BC interface, the TGO/BC interface may begin to crack in the heating stage, then in the swelling stage the interface crack in the TGO/BC interface may close, and in the cooling stage the interface will crack again along the TGO/BC interface. When considering TGO/BC interface and sintering of TC simultaneously, sintering of TC has great influence on the stress S22 of BC near the peak and valley of TGO/BC interface.

scholarly journals Research Progress of Failure Mechanism of Thermal Barrier Coatings at High Temperature via Finite Element Method

Coatings ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 732 ◽  
Author(s):  
Zhong-Chao Hu ◽  
Bin Liu ◽  
Liang Wang ◽  
Yu-Hang Cui ◽  
Yan-Wei Wang ◽  
...  
Keyword(s):  
Finite Element ◽  
High Temperature ◽  
Failure Mechanism ◽  
Thermal Barrier Coatings ◽  
Aircraft Engine ◽  
Research Progress ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Working Temperature ◽  
Element Simulation

In the past decades, the durability of thermal barrier coatings (TBCs) has been extensively studied. The majority of researches emphasized the problem of oxidation, corrosion, and erosion induced by foreign object damage (FOD). TBCs with low thermal conductivity are usually coated on the hot-section components of the aircraft engine. The main composition of the TBCs is top-coat, which is usually regarded as a wear-resistant and heat-insulating layer, and it will significantly improve the working temperature of the hot-section components of the aircraft engine. The application of TBCs are serviced under a complex and rigid environment. The external parts of the TBCs are subjected to high-temperature and high-pressure loading, and the inner parts of the TBCs have a large thermal stress due to the different physical properties between the adjacent layers of the TBCs. To improve the heat efficiency of the hot-section components of aircraft engines, the working temperature of the TBCs should be improved further, which will result in the failure mechanism becoming more and more complicated for TBCs; thus, the current study is focusing on reviewing the failure mechanism of the TBCs when they are serviced under the actual high temperature conditions. Finite element simulation is an important method to study the failure mechanism of the TBCs, especially under some extremely rigid environments, which the experimental method cannot realize. In this paper, the research progress of the failure mechanism of TBCs at high temperature via finite element modeling is systematically reviewed.

Lattice Imaging of Grain Boundaries in Ceramics

1977 ◽  
Vol 35 ◽  
pp. 114-115
Author(s):  
D. R. Clarke ◽  
G. Thomas
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Grain Boundaries ◽  
High Temperature Strength ◽  
Current Interest ◽  
Lattice Imaging ◽  
Special Significance ◽  
Structural Applications ◽  
Refractory Ceramics

Grain boundaries have long held a special significance to ceramicists. In part, this has been because it has been impossible until now to actually observe the boundaries themselves. Just as important, however, is the fact that the grain boundaries and their environs have a determing influence on both the mechanisms by which powder compaction occurs during fabrication, and on the overall mechanical properties of the material. One area where the grain boundary plays a particularly important role is in the high temperature strength of hot-pressed ceramics. This is a subject of current interest as extensive efforts are being made to develop ceramics, such as silicon nitride alloys, for high temperature structural applications. In this presentation we describe how the techniques of lattice fringe imaging have made it possible to study the grain boundaries in a number of refractory ceramics, and illustrate some of the findings.

Electron energy loss near edge structures of intermetallic alloys and grain boundaries in NiAl

1996 ◽  
Vol 54 ◽  
pp. 522-523
Author(s):  
G.A. Botton ◽  
C.J. Humphreys
Keyword(s):  
High Temperature ◽  
Transition Metal ◽  
Energy Loss ◽  
Grain Boundaries ◽  
Industrial Applications ◽  
Edge Structure ◽  
Structural Applications ◽  
Yield Behaviour ◽  
Late Transition ◽  
Metal Aluminides

Transition metal aluminides are of great potential interest for high temperature structural applications. Although these materials exhibit good mechanical properties at high temperature, their use in industrial applications is often limited by their intrinsic room temperature brittleness. Whilst this particular yield behaviour is directly related to the defect structure, the properties of the defects (in particular the mobility of dislocations and the slip system on which these dislocations move) are ultimately determined by the electronic structure and bonding in these materials. The lack of ductility has been attributed, at least in part, to the mixed bonding character (metallic and covalent) as inferred from ab-initio calculations. In this work, we analyse energy loss spectra and discuss the features of the near edge structure in terms of the relevant electronic states in order to compare the predictions on bonding directly with spectroscopic experiments. In this process, we compare spectra of late transition metal (TM) to early TM aluminides (FeAl and TiAl) to assess whether differences in bonding can also be detected. This information is then discussed in terms of bonding changes at grain boundaries in NiAl.

Segregation of Refractory Metals at Grain Boundaries in High-Temperature Alloys

2020 ◽  
Vol 2020 (11) ◽  
pp. 1292-1299
Author(s):  
I. M. Razumovskii ◽  
V. I. Razumovskiy ◽  
I. A. Logachev ◽  
A. O. Rodin ◽  
M. I. Razumovsky
Keyword(s):  
High Temperature ◽  
Grain Boundaries ◽  
Refractory Metals ◽  
High Temperature Alloys

Radiation-enhanced high-temperature cobalt diffusion at grain boundaries of nanostructured hardmetal

2021 ◽  
pp. 129746
Author(s):  
A.A. Zaitsev ◽  
I. Konyashin ◽  
P.A. Loginov ◽  
E.A. Levashov ◽  
A.S. Orekhov
Keyword(s):  
High Temperature ◽  
Grain Boundaries

Analysis of Pipe-Soil Interaction for a Miniature Pipejacking

2006 ◽  
Vol 22 (3) ◽  
pp. 213-220 ◽  
Author(s):  
K. J. Shou ◽  
F. W. Chang
Keyword(s):  
Finite Element ◽  
Failure Mechanism ◽  
Physical Modeling ◽  
Driving Force ◽  
Numerical Models ◽  
Surface Subsidence ◽  
Finite Element Software

AbstractIn this study, physical and numerical models were used to analyze pipe-soil interaction during pipejacking work. After calibrating with the physical modeling results, the finite element software ABAQUS [1] was used to study the pipejacking related behavior, such as surface subsidence, failure mechanism, pipe-soil interaction, etc. The results show that the driving force in the tunnelling face is very important and critical for pipejacking. Surface subsidence is mainly due to the lack of driving force, however, excessive driving force could cause the unfavorable surface heaving problem. It also suggests that the depth of the pipe is critical to determine a proper driving force to stabilize the tunnelling face.

Sign in / Sign up

Export Citation Format

Share Document