Preliminary Review of the Influence of Cavitation Behavior in Creep Damage Constitutive Equations

2014 ◽  
Vol 940 ◽  
pp. 46-51 ◽  
Author(s):  
Xin Yang ◽  
Qiang Xu ◽  
Zhong Yu Lu ◽  
Simon Barrans
Keyword(s):  
Reference Value ◽  
Creep Damage ◽  
Preliminary Review ◽  
Current Application ◽  
Cavitation Damage ◽  
X Ray ◽  
Creep Cavitation ◽  
Cr Steels ◽  
Cavitation Behavior ◽  
Damage Equation

This review paper mainly consists of from two aspects: (a) the evolution of the cavitation damage equation from Dyson to current application in high Cr steels by traditional techniques; (b) quantitation analyses of cavitation behavior in brass, copper, dual phase steel from X-ray microtomtograph. Though there is a lack of experimental data for high Cr steels by X-ray microtomography currently, but (b) has provided reference value for studying creep cavitation behavior in high Cr steels. This paper will be the fundamental of development new creep damage constitutive equation through quantitation analyses of X-ray tomography.

Comparative Analysis of Creep Cavitation Damage in 0.5Cr-0.5Mo-0.3V Steel after Long-Term Creep Exposure by Metallography and Replica Testing

2017 ◽  
Vol 891 ◽  
pp. 335-340
Author(s):  
Zdeněk Kuboň ◽  
Lenka Pekařová ◽  
Jana Kosňovská ◽  
Pavel Poštulka
Keyword(s):  
Outer Surface ◽  
Creep Damage ◽  
Metallographic Analysis ◽  
Pipe Surface ◽  
Cavitation Damage ◽  
Pipe Elbow ◽  
Creep Cavitation ◽  
Term Creep ◽  
Parallel Evaluation

Complex metallographic analysis was performed on the steam pipe elbow made of 0.5Cr-0.5Mo-0.3V steel after long-term (more than 240 000 hours) of operation at elevated temperature that revealed the extensive creep damage on the outer surface of the pipe elbow. Metallographic analysis confirmed pronounced creep damage at the outer surface but, at the same time, the non-uniform nature of the cavitation. The density of cavities continuously decreased from outer to inner pipe surface in the most damaged area and rapidly waned along the circumference as well as the length of the elbow. Parallel evaluation of actual extent of the cavitation damage made by metallography and replica methods in various parts of the pipe elbow confirmed that replica method is capable to describe and quantify the cavitation damage of this steel in the same way as metallography, including evaluation of creep damage according to Nordtest NT TR 302.

Effect of X-ray CT resolution on the quality of permeability computation for granular soils: definition of a criterion based on morphological properties

Soil Research ◽  
2019 ◽  
Vol 57 (6) ◽  
pp. 589 ◽  
Author(s):  
Miriam Patricia Ortega Ramírez ◽  
Laurent Oxarango ◽  
Alfonso Gastelum Strozzi
Keyword(s):  
Volume Fraction ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Reference Value ◽  
Image Resolution ◽  
Morphological Properties ◽  
Morphological Description ◽  
Granular Soils ◽  
X Ray

In this study, the quality of soil permeability estimation based on computational fluid dynamics is discussed. Two types of three-dimensional geometries were considered: an image of Fontainebleau sand obtained from X-ray computed micro-tomography and a virtual pack of spheres. Numerical methods such as finite difference or lattice Boltzmann can conveniently use the image voxels as computational mesh elements. In this framework, the image resolution is directly associated with quality of the numerical computation. A higher resolution should promote both a better morphological description and discretisation. However, increasing the resolution may prevent the studied volume from being representative. Here, each sample was scaled and analysed at five resolutions. The dependence of soil properties with respect to the image resolution is discussed. As resolution decreased, the permeability and specific surface values tended to diverge from the reference value. This deterioration could be attributed to the shift of the pore size distribution towards badly resolved pores in the voxelised geometry. As long as granular soils are investigated, the volume fraction of pores smaller than six voxels in diameter should not exceed 50% to ensure the validity of permeability computation. In addition, based on an analysis of flow distribution, the volume fraction of pores smaller than four voxels should not exceed 25% in order to limit the flow rate occurring in badly discretised pores under 10%. For the Fontainebleau sand and virtual pack of spheres, the maximum voxel size meeting this criterion corresponded to 1/14 and 1/20 of the mean grain size respectively.

Creep damage and expected creep life for welded 9–11% Cr steels

2007 ◽  
Vol 84 (1-2) ◽  
pp. 69-74 ◽  
Author(s):  
P. Auerkari ◽  
S. Holmström ◽  
J. Veivo ◽  
J. Salonen
Keyword(s):  
Creep Damage ◽  
Creep Life ◽  
Cr Steels

scholarly journals Review of Creep Cavitation and Rupture of Low Cr Alloy and its Weldment

2013 ◽  
Vol 744 ◽  
pp. 407-411
Author(s):  
Qi Hua Xu ◽  
Qiang Xu ◽  
Yong Xin Pan ◽  
Michael Short
Keyword(s):  
High Temperature ◽  
Constitutive Equation ◽  
Damage Mechanics ◽  
Experimental Approach ◽  
Creep Damage ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
Safe Operation ◽  
Computational Approaches ◽  
Creep Cavitation

This paper presents a review of creep cavitation and rupture of low Cr alloy and its weldment, particular in the heat-affected zone (HAZ). Creep damage is one of the serious problems for the high temperature industry. One of the computational approaches is continuum damage mechanics which has been developed and applied complementary to the experimental approach and assists in the safe operation. However, the existing creep damage constitutive equations are not developed specifically for low stress. Therefore, in order to form the physical bases for the development of creep damage constitutive equation, it is necessary to critically review the creep cavitation and rupture characteristics of low Cr alloy and its weldment.

Effect of High-Temperature Corrosion on the Service Life of P91 Piping in Biomass Co-firing

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
C. P. O'Hagan ◽  
R. A. Barrett ◽  
S. B. Leen ◽  
R. F. D. Monaghan
Keyword(s):  
Tube Wall ◽  
Thermal Power ◽  
Creep Damage ◽  
High Temperature Corrosion ◽  
Corrosion Mechanism ◽  
Creep Life ◽  
Sem Images ◽  
X Ray ◽  
Superheater Tube ◽  
Wall Loss

Co-firing biomass with traditional fuels is becoming increasingly relevant to thermal power plant operators due to increasingly stringent regulations on greenhouse gas emissions. It has been found that when biomass is co-fired, an altered ash composition is formed, which leads to increased levels of corrosion of the superheater tube walls. Synthetic salt, which is representative of the ash formed in the co-firing of a 70% peat and 30% biomass mixture, has been produced and applied to samples of P91 at 540 °C for up to 28 days. This paper presents results for oxide layer thickness and loss of substrate from testing. Scanning electron microscopy (SEM) images and energy-dispersive X-ray spectroscopy (EDX) element maps are obtained and presented in order to gain an understanding of the complex corrosion mechanism which occurs. A finite-element (FE) methodology is presented which combines corrosion effects with creep damage in pressurized tubes. The effects of corrosion tube wall loss and creep damage on tube stresses and creep life are investigated.

D-112 Invited—In Situ Synchrotron X-ray Studies of Creep Damage

2007 ◽  
Vol 22 (2) ◽  
pp. 186-186
Author(s):  
A. Pyzalla ◽  
A. Isaac ◽  
F. Sket ◽  
K. Dzieciol ◽  
B. Camin ◽  
...  
Keyword(s):  
Creep Damage ◽  
X Ray
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