The Effect of Plasticity on Process-Zone Predictions of DHC Initiation at a Flaw in CANDU Reactor Zr-Nb Pressure Tubes

2002 ◽  
Author(s):  
Douglas A. Scarth ◽  
Ted Smith
Keyword(s):  
Zirconium Alloy ◽  
Process Zone ◽  
Matrix Material ◽  
Zone Model ◽  
Hydrogen Atoms ◽  
Alloy Matrix ◽  
Model Calculations ◽  
Alloy Material ◽  
Crack Growth Mechanism ◽  
Service Inspection

Delayed Hydride Cracking (DHC) in Zr-2.5 Nb alloy material is of interest to the CANDU industry in the context of the potential to initiate DHC at a blunt flaw in a CANDU reactor pressure tube. The material is susceptible to DHC when there is diffusion of hydrogen atoms to the flaw, precipitation of hydride platelets, and development of a hydrided region at the flaw tip. The hydrided region could then fracture to the extent that a crack forms, and is able to grow by the DHC crack growth mechanism. A procedure for evaluating DHC initiation at a blunt flaw that takes into account the effect of flaw geometry has been developed. This methodology can, in principle, be applied to any flaw that is found during in-service inspection. The methodology is based on representing the stress relaxation due to hydride formation, and crack initiation, by a process zone. The authors have presented predictions of DHC initiation on the basis of elastic conditions in the surrounding zirconium alloy matrix material outside of the process zone in papers presented at the 1999, 2000 and 2001 ASME PVP Conferences. In the present paper, the effects of plasticity in the surrounding zirconium alloy matrix material have been incorporated into a simple theoretical process-zone model for DHC initiation, as well as into an engineering process-zone model that is suitable for evaluation of in-service flaws. The resulting process-zone model calculations and comparisons with DHC initiation experiments demonstrate that DHC initiation predictions can be overly-conservative if plasticity is not taken into account.

Developments in Flaw Evaluation for CANDU Reactor Zr-Nb Pressure Tubes

2000 ◽  
Vol 123 (1) ◽  
pp. 41-48 ◽  
Author(s):  
Douglas A. Scarth ◽  
Ted Smith
Keyword(s):  
Process Zone ◽  
Peak Stress ◽  
Evaluation Procedure ◽  
Engineering Model ◽  
Hydrogen Atoms ◽  
Engineering Applications ◽  
Alloy Material ◽  
Crack Growth Mechanism ◽  
Service Inspection ◽  
Reactor Pressure

Delayed hydride cracking (DHC) in Zr-2.5Nb alloy material is of interest to the CANDU (CANada Deuterium Uranium) industry in the context of the potential to initiate DHC at a blunt flaw in a CANDU reactor pressure tube. The material is susceptible to DHC when there is diffusion of hydrogen atoms to the flaw, precipitation of hydride platelets, and development of a hydrided region at the flaw root. The hydrided region can then fracture to the extent that a crack forms, and is able to grow by the DHC crack growth mechanism. The existing CANDU blunt flaw DHC evaluation procedure is based on a threshold peak flaw-tip stress for DHC initiation that is independent of flaw geometry. Work is underway to improve the existing blunt flaw DHC evaluation procedure by developing a methodology that takes into account the effect of flaw geometry parameters. This methodology can, in principle, be applied to any flaw that is found during in-service inspection. The methodology is based on representing the stress relaxation due to hydride formation, and crack initiation, by a process zone. This approach has been used successfully in other engineering applications. A description of how the process-zone methodology can be used to quantify the effect of flaw geometry on the threshold peak stress for DHC initiation is provided. A model that is suitable for actual engineering applications is described, and the engineering model illustrates the dependency of the threshold peak stress for DHC initiation on flaw geometry. Agreement between engineering model predictions and experimental results is reasonable. Various aspects of the DHC initiation problem that are being addressed, in addition to flaw geometry, are described.

Validation of Weight Function Based Process-Zone Model for Evaluation of Delayed Hydride Cracking Initiation in Zr-2.5Nb Pressure Tubes

2016 ◽  
Author(s):  
Steven X. Xu ◽  
Dennis Kawa ◽  
Jun Cui ◽  
Heather Chaput
Keyword(s):  
Weight Function ◽  
Process Zone ◽  
Matrix Material ◽  
Pressure Tube ◽  
Zone Model ◽  
Hydrogen Atoms ◽  
Fuel Bundle ◽  
Pressure Tubes ◽  
Delayed Hydride Cracking ◽  
Hydride Cracking

In-service flaws in cold-worked Zr-2.5 Nb pressure tubes in CANDU(1) reactors are susceptible to a phenomenon known as delayed hydride cracking (DHC). The material is susceptible to DHC when there is diffusion of hydrogen atoms to a service-induced flaw, precipitation of hydrides on appropriately oriented crystallographic planes in the zirconium alloy matrix material, and development of a hydrided region at the flaw tip. The hydrided region could then fracture to the extent that a crack forms and DHC is said to have initiated. Examples of in-service flaws are fuel bundle scratches, crevice corrosion marks, fuel bundle bearing pad fretting flaws, and debris fretting flaws. These flaws are volumetric in nature. Evaluation of DHC initiation from the flaw is a requirement of Canadian Standards Association (CSA) Standard N285.8. This paper describes the validation of the weight function based process-zone model for evaluation of pressure tube flaws for DHC initiation. Validation was performed by comparing the predicted threshold load levels for DHC initiation with the results from DHC initiation experiments on small notched specimens. The notches in the specimens simulate axial in-service flaws in the pressure tube. The validation was performed for both un-irradiated and pre-irradiated pressure tube material.

Multi-length scale micromorphic process zone model

2009 ◽  
Vol 44 (3) ◽  
pp. 433-445 ◽  
Author(s):  
Franck Vernerey ◽  
Wing Kam Liu ◽  
Brian Moran ◽  
Gregory Olson
Keyword(s):  
Process Zone ◽  
Zone Model ◽  
Length Scale

A Review on Role of Aluminum Matrix Materials, Failure Causes and Optimization Techniques

2021 ◽  
Vol 6 (3) ◽  
pp. 1-11
Author(s):  
Tilahun Y ◽  
◽  
Mesfin G ◽  
Keyword(s):  
Failure Modes ◽  
Matrix Material ◽  
Aluminum Matrix ◽  
Ductile Failure ◽  
Failure Surface ◽  
Optimization Techniques ◽  
Alloy Matrix ◽  
Modes Of Failure ◽  
Causes Of Failure

Aluminum is a metal matrix material which is widely used in different industrial as well as engineering applications.it has a great advantage due to its remarkable properties like less density, formability, and light in weight, recyclability and other properties. but, failure of aluminum matrix materials are the main problems in aluminum industries now a days.in this review role of aluminum and its alloys as matrix materials, their failure modes, causes of failure and optimization techniques to minimize this failure modes and causes of failure are discussed. Sources are reviewed which are from 2005 to recent one. Consequently, most modes of failure, causes of failure and most optimization techniques of aluminum and its alloy matrix materials are found. most modes of failure are mechanical related like fatigue failure, surface cracking, ductile failure, porosity formation, and stress related like stress corrosion cracking, surface weakness due to repeated stresses and other factors are summarized.in causes of failure mostly like corrosion formation, wear formation and poor mechanical properties are discussed.

Physical and Mechanical Properties of Composites with Aluminum Alloy Matrix Designed for Metal Forming

2013 ◽  
Vol 212 ◽  
pp. 59-62 ◽  
Author(s):  
Jerzy Myalski ◽  
Jakub Wieczorek ◽  
Adam Płachta
Keyword(s):  
Mechanical Properties ◽  
Metal Forming ◽  
Matrix Material ◽  
Physical And Mechanical Properties ◽  
Mechanical Mixing ◽  
Alloy Matrix ◽  
Segregation Process ◽  
The Matrix ◽  
Glass Carbon ◽  
Properties Of Composites

The change of matrix and usage of the aluminum alloys designed for the metal forming in making the composite suspension allows to extend the processing possibility of this type of materials. The possibility of the metal forming of the composites obtained by mechanical mixing will extend the range of composite materials usage. Applying of the metal forming e.g. matrix forging, embossing, pressing or rolling, will allow to remove the incoherence of the structure created while casting and removing casting failures. In order to avoid the appearance of the casting failures the homogenization conditions need to be changed. Inserting the particles into the matrix influences on the shortening of the composite solidification. The type of the applied particles influenced the sedimentation process and reinforcement agglomeration in the structure of the composite. Opposite to the composites reinforced with one-phase particles applying the fasess mixture (glassy carbon and silicon carbide) triggered significant limitation in the segregation process while casting solidification. Inserting the particles into the AW-AlCu2SiMn matrix lowers the mechanical properties tension and impact value strength. The most beneficial mechanical properties were gained in case of heterofasess composites reinforced with the particle mixture of SiC and glass carbon. The chemical composition of the matrix material (AW-AlCu2SiMn) allows to increase additionally mechanical characteristics by the precipitation hardening reached through heat casting forming.

scholarly journals Effect of Reactive SPS on the Microstructure and Properties of a Dual-Phase Ni-Al Intermetallic Compound and Ni-Al-TiB2 Composite

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5668
Author(s):  
Paweł Hyjek ◽  
Iwona Sulima ◽  
Piotr Malczewski ◽  
Krzysztof Bryła ◽  
Lucyna Jaworska
Keyword(s):  
Intermetallic Compound ◽  
Tribological Properties ◽  
Matrix Material ◽  
Dual Phase ◽  
Compression Tests ◽  
Two Phase ◽  
Alloy Matrix ◽  
Plastic Properties ◽  
Mechanical And Tribological Properties ◽  
The Matrix

As part of the tests, a two-phase NiAl/Ni3Al alloy and a composite based on this alloy with 4 vol% addition of TiB2 were produced by the reactive FAST/SPS (Field Assisted Sintering Technology/Spark Plasma Sintering) sintering method. The sintering process was carried out at 1273 K for 30 s under an argon atmosphere. The effect of reactive SPS on the density, microstructure, and mechanical and tribological properties of a dual-phase Ni-Al intermetallic compound and Ni-Al-TiB2 composite was investigated. Products obtained were characterized by a high degree of sintering (over 99% of the theoretical density). The microstructure of sinters was characterized by a large diversity, mainly in regard to the structure of the dual-phase alloy (matrix). Compression tests showed satisfactory plastic properties of the manufactured materials, especially at high temperature (1073 K). For both materials at room temperature, the compressive strength was over 3 GPa. The stress–strain curves were observed to assume a different course for the matrix material and composite material, including differences in the maximum plastic flow stress depending on the test temperature. The brittle-to-ductile transition temperature was determined to be above 873 K. The research has revealed differences in the physical, mechanical and tribological properties of the produced sinters. However, the differences favourable for the composite were mostly the result of the addition of TiB2 ceramic particles uniformly distributed on grain boundaries.

scholarly journals Model Calculations of Solar Wind Expansion Including an Enhanced Fraction of Ionizing Electrons

1980 ◽  
Vol 91 ◽  
pp. 159-162
Author(s):  
E. F. Petelski ◽  
H. J. Fahr ◽  
H. W. Ripken
Keyword(s):  
Solar Wind ◽  
Impact Ionization ◽  
Hydrogen Atoms ◽  
Interstellar Gas ◽  
Model Calculations ◽  
Neutral Gas ◽  
Continuity Equations ◽  
Velocity Effect ◽  
Collective Interactions ◽  
Ionization Velocity

Collective interactions of the solar wind and newly ionized interstellar gas cause turbulent electron heating to ionizing energies analogous to laboratory experiments on the critical ionization velocity effect. Implications for solar wind and interstellar gas dynamics are calculated by simultaneously solving continuity equations for solar wind protons, interstellar hydrogen atoms, and energetic electrons. Electron impact ionization is shown to be practically as important as photoionization, giving rise to a stronger deceleration and heating of the distant solar wind, a weaker terminating shock, a smaller stand-off distance of the helio pause, and implying higher densities of the outer solar wind and the interstellar neutral gas.

Resistance Butt Welding of Zirconium Alloy Material

2008 ◽  
Vol 23 (8) ◽  
pp. 844-851 ◽  
Author(s):  
D. S. Setty ◽  
Reddy P. Ravinder ◽  
A. L. N. Murthy
Keyword(s):  
Zirconium Alloy ◽  
Butt Welding ◽  
Alloy Material

Numerical Investigation on Impact Energy Absorption of Single-Walled Carbon Nanotube Reinforced Composites

2012 ◽  
Author(s):  
Lingyu Sun ◽  
Jian Zhang ◽  
Dingxin Leng
Keyword(s):  
Numerical Investigation ◽  
Energy Absorption ◽  
Impact Energy ◽  
Metal Matrix ◽  
Failure Modes ◽  
Volume Fraction ◽  
Matrix Material ◽  
Reinforced Composites ◽  
Alloy Matrix ◽  
The Impact

With the exceptional mechanical properties, carbon nanotubes (CNTs) are considered to be attractive candidate reinforcements for composite materials and to have potential applications in improving the energy absorption capability of matrix material. However, it is still difficult to reveal the micro-mechanisms of the impact energy absorption of CNT-reinforced composites by experiments, hence, the numerical investigation is helpful. In this paper, a unit cell of single-walled CNTs (SWCNTs) embedded in metal matrix is modeled by nano-scale finite element method. Under impact loads, the failure modes of a single SWCNT and the SWCNT in matrix are predicted, respectively, and several possible energy absorption mechanisms are explained and compared. The investigation shows that, the metal matrix restraints the radial expansion of the SWCNT and therefore improves its crush buckling resistance, and makes it absorb more energy before collapse. The specific energy absorption of SWCNTs-reinforce composites increases with the increasing volume fraction of SWCNTs in both matrixes, and ascends more quickly in magnesium alloy than in aluminum alloy matrix.

On a ferroelastic mechanism governing the toughness of metastable tetragonal-prime ( t ′) yttria-stabilized zirconia

2007 ◽  
Vol 463 (2081) ◽  
pp. 1393-1408 ◽  
Author(s):  
C Mercer ◽  
J.R Williams ◽  
D.R Clarke ◽  
A.G Evans
Keyword(s):  
Gas Turbines ◽  
Process Zone ◽  
Yttria Stabilized Zirconia ◽  
Cubic Phase ◽  
Zone Model ◽  
Toughening Mechanism ◽  
Stabilized Zirconia ◽  
Prior Literature ◽  
Reasonable Choice ◽  
Individual Grains

This article investigates the toughness of yttria-stabilized zirconia (YSZ) with the tetragonal-prime ( t ′) structure. Such materials are used as durable thermal barriers in gas turbines. Their durability has been attributed to high toughness, relative to materials in the cubic phase field. Based on prior literature, a ferroelastic toughening mechanism is hypothesized and this assertion is examined by characterizing the material in the wake of an indentation-induced crack. Assessment by transmission electron microscopy, Raman spectroscopy and optical interferometry has affirmed the existence of a process zone, approximately 3 μm in width, containing a high density of nano-scale domains, with equal proportions of all three crystallographic variants. Outside the zone, individual grains contain a single variant (no domains) implying that the toughening mechanism is controlled by domain nucleation (rather than the motion of pre-existing twin boundaries). The viability of the ferroelastic toughening mechanism is assessed using a process zone model that relates the observed toughening to the stress/strain hysteresis accompanying domain formation. Based on the measured process zone size, the known tetragonality of t ′-7 wt% YSZ and the enhancement in toughness relative to cubic YSZ, consistency between the model and the observed toughening is demonstrated for a reasonable choice of the coercive stress.

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