Brittle Creep Damage as the Seismic Signature of Dyke Propagations within Basaltic Volcanoes

Taking nickel-based single crystal superalloy DD6 as the research object, different degrees of creep damage were prefabricated by creep interruption tests, and then the creep damage was repaired by the restoration heat treatment system of solid solution heat treatment and two-stage aging heat treatment. The results show that with the creep time increasing, the alloy underwent microstructure evolution including γ′ phase coarsening, N-type rafting and de-rafting. After the restoration heat treatment, the coarse rafted γ′ phase of creep damaged specimens dissolved, precipitated, grew up, and became cubic again. Except for the specimens with creep interruption of 100 h, the γ′ phase can basically achieve the same arrangement as the γ′ phase of the original sample. The comparison of the secondary creep test shows that the steady-state creep stage of the test piece after the restoration heat treatment is relatively increased, and the total creep life can reach the same level as the primary creep life. The high temperature creep properties of the tested alloy are basically recovered, and the restoration heat treatment effect is good.

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Non-linear creep damage model of sandstone under freeze-thaw cycle

Journal of Central South University ◽

10.1007/s11771-021-4656-3 ◽

2021 ◽

Vol 28 (3) ◽

pp. 954-967

Author(s):

Jie-lin Li ◽

Long-yin Zhu ◽

Ke-ping Zhou ◽

Hui Chen ◽

Le Gao ◽

...

Keyword(s):

Damage Model ◽

Creep Damage ◽

Freeze Thaw ◽

Thaw Cycle ◽

Linear Creep ◽

Non Linear ◽

Freeze Thaw Cycle ◽

Creep Damage Model

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Atomic Diffusion Induced Damage of Ni-Base Super Alloy at Elevated Temperature

Volume 9: Mechanics of Solids, Structures and Fluids; NDE, Diagnosis, and Prognosis ◽

10.1115/imece2016-67592 ◽

2016 ◽

Author(s):

Motoki Takahashi ◽

Ken Suzuki ◽

Hideo Miura

Keyword(s):

Power Plants ◽

Creep Damage ◽

Rotor Blades ◽

Atomic Scale ◽

Atomic Diffusion ◽

Kernel Average Misorientation ◽

Damage Process ◽

Creep Loading ◽

Ebsd Method ◽

Base Superalloy

Ni-base superalloys consisting of binary phases such as cuboidal γ’ (Ni3Al) precipitates orderly dispersed in the γ matrix (Ni-rich matrix) have been generally used for rotor blades in energy power plants. However, fine dispersed γ’ precipitates are coarsened perpendicularly to the applied load direction during high temperature creep loading. As this phenomenon called “Rafting” proceeds, the strengthened micro texture disappears and then, cracks starts to grow rapidly along the boundaries of the layered texture. Thus, it is very important to evaluate the change of the crystallinity of the alloy in detail for explicating the atomic scale damage process. In this study, the change of the micro-texture of the Ni-base superalloy (CM247LC) was observed by using EBSD method. The change in the crystallinity was evaluated using both Kernel Average Misorientation (KAM) and image quality (IQ) values. The KAM value indicates the dislocation density and the IQ value shows the order of atom arrangement in the observed area. As a result, KAM value showed no significant change with increasing the creep damage. On the other hand, the IQ value monotonically shifted to lower values and the average IQ value gradually decreased as the creep loading time increased. Decreasing IQ value without change in KAM value implies that the density of point defects such as vacancies mainly increased under creep loading and ordered Ll2 structure became disordered. Therefore, the creep damage of this alloy is mainly dominated by not the accumulation of dislocations, but the increase in the disorder of atom arrangement in the micro texture caused by the diffusion of component elements.

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An improved nonlinear damage model of rocks considering initial damage and damage evolution

International Journal of Damage Mechanics ◽

10.1177/1056789520909531 ◽

2020 ◽

Vol 29 (7) ◽

pp. 1117-1137 ◽

Cited By ~ 3

Author(s):

Wenlin Feng ◽

Chunsheng Qiao ◽

Shuangjian Niu ◽

Zhao Yang ◽

Tan Wang

Keyword(s):

Damage Evolution ◽

Least Squares Method ◽

Damage Model ◽

Creep Damage ◽

Secondary Creep ◽

Nonlinear Creep ◽

Creep Failure ◽

Initial Damage ◽

Nonlinear Damage Model ◽

Creep Damage Model

The experimental results show that the creep properties of the rocks are affected by the initial damage, and the damage evolution also has a significant impact on the time-dependent properties of the rocks during the creep. However, the effects of the initial damage and the damage evolution are seldom considered in the current study of the rocks' creep models. In this paper, a new nonlinear creep damage model is proposed based on the multistage creep test results of the sandstones with different damage degrees. The new nonlinear creep damage model is improved based on the Nishihara model. The influences of the initial damage and the damage evolution on the components in the Nishihara model are considered. The creep damage model can not only describe the changes in three creep stages, namely, the primary creep, the secondary creep, and the tertiary creep, but also reflect the influence of the initial damage and the damage evolution on creep failure. The nonlinear least squares method is used to determine the parameters in the nonlinear creep damage model. The consistency between the experimental data and the predicted results indicates the applicability of the nonlinear damage model to accurately predict the creep deformation of the rocks with initial damage.

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Residual Stresses in Overlapping Friction Taper Stud Welds

Materials Science Forum ◽

10.4028/www.scientific.net/msf.652.111 ◽

2010 ◽

Vol 652 ◽

pp. 111-115 ◽

Cited By ~ 3

Author(s):

D.G. Hattingh ◽

Axel Steuwer ◽

M. Neil James ◽

I.N. Wedderburn

Keyword(s):

Solid State ◽

Neutron Diffraction ◽

Residual Stresses ◽

Creep Damage ◽

Local Damage ◽

Planar Defects ◽

Repair Technique ◽

Damage Repair ◽

Stud Welding ◽

Residual Strains

This paper presents microstructural, hardness and residual strain information for solid-state welds in creep-resistant Cr-Mo steel, made using the new local damage repair technique offered by friction taper stud welding (FTSW). The technique is suitable for making single welds to repair, for example, localised creep damage but can also be extended to deal with planar defects through the use of overlapping welds. Neutron diffraction was used to measure residual strains at a number of positions along a series of 5 overlapping FTS welds.

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Finite Element Analysis of Creep Damage Behavior Near the Cavity on Bimaterial Interface

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.324-325.951 ◽

2006 ◽

Vol 324-325 ◽

pp. 951-954 ◽

Cited By ~ 1

Author(s):

Qing Min Yu ◽

Zhu Feng Yue ◽

Yong Shou Liu

Keyword(s):

Finite Element ◽

Elastic Moduli ◽

Elastic Stress ◽

Creep Damage ◽

Ductile Material ◽

Bimaterial Interface ◽

Modulus Ratio ◽

Element Analysis ◽

Damage Law ◽

The Difference

Fracture along an interface between materials plays a major role in failure of material. In this investigation, finite element calculations with Kachanov–Rabotnov damage law were carried out to study the creep damage distribution near the interface cavity in bimaterial specimens. The specimens with central hole were divided into three types. The material parameters of K-R law used in this paper were chosen for a brittle material and ductile material. All calculations were performed under four load cases. Due to the difference between elastic moduli of the bounded materials, the elastic stress field as a function of the Young’s modulus ratio (R=E1/E2) was determined. At the same time, the influence of model type on elastic stress distribution near the cavity was considered. Under the same conditions, the material with larger modulus is subjected to larger stress. The creep damage calculations show that the location of the maximum damage is different for each model. The distributions of creep damage for all three models are dependent on the material properties and load cases.

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