bluuebunny/crossref_metadata_2025_split huggingface dataset:
Laboratory Testing to Evaluate Changes in Hydraulic Conductivity of Compacted Clays Caused by Freeze-Thaw: State-of-the-Art
Authors: Othman MA , Benson CH , Chamberlain EJ , Zimmie TF 
Published: March 2009

Several laboratory studies have shown that the hydraulic conductivity of compacted clay may increase up to three orders of magnitude when subjected to freeze-thaw. In this paper, methods to freeze and thaw specimens of compacted clay are reviewed and compared. Methods to measure the hydraulic conductivity of the specimens are also reviewed. Only naturally formed clay soils are considered; soil-bentonite mixtures and other amended soils are not included.
A review of testing conditions present during freeze-thaw and their effect on hydraulic conductivity is also included. Testing conditions that are addressed include availability of an external supply of water (closed vs. open system), dimensionality of freezing (one-dimensional vs. three-dimensional), rate of freezing, ultimate temperature, number of freeze-thaw cycles, and state of stress. The rate of freezing, number of freeze-thaw cycles, and state of stress appear to have the largest effect on hydraulic conductivity.
The effect of sampling disturbance on the hydraulic conductivity of compacted clay subjected to freeze-thaw is also presented. Specimens removed in Shelby tubes may be disturbed during sampling and extrusion. As a result, the effects of freeze-thaw can be masked. Collecting block specimens of thawed clay or taking core specimens of frozen clay are suggested as alternative procedures. A method to collect block specimens is presented.
Fracture Toughness and Impact Tests on Neutron Irradiated Ferritic Steels : Results and Correlations
Authors: Chatterjee S , Sriharsha HK , Viswanathan UK 
Published: March 2009

Four A533B pressure vessel steels containing 0.16 wt% copper, nickel and phosphorous ranging from 0.10 to 0.82 wt% and 0.006 to 0.02 wt% respectively, and a AISI 403 stainless steel, a typical end fitting material used in pressurised heavy water reactors, in the unirradiated condition, were evaluated by instrumented impact testing to determine the crack initiation energy (CVNi), total absorbed energy (CVN), ductilebrittle transition temperature (T41J,T0.89mm), dynamic yield strength (σyd) and dynamic initiation fracture toughness (Kid). Three of these steels were irradiated at 563K to a nominal fast fluence of 1x1019, n/cm2 (E &gt; 1 MeV) and the corresponding parameters were evaluated.
It was observed that the widely used correlation between CVN and KIC modified as (Kid/σyd)2 = 0.64[(CVN/σyd)-0.01] overpredicted the experimental Kid values by a factor of 2. However, if the CVNi was used instead of CVN, the predicted values were within ± 20%.
The irradiation induced decrease in Kid could not be correlated with increase in transition temperature. However, it could be correlated with the corresponding changes in σyd and CVNi values.
Further Microstructural Characterization of Submerged-Arc Weld Metals - II
Authors: Lawless KR , Lowe AL 
Published: March 2009

This paper presents the results of further microstructural evaluations of irradiated Mn-Mo-Ni wire/Linde 80 flux submerged-arc weld metals typically found in Babcock & Wilcox fabricated reactor vessels. Four Mn-Mo-Ni wire/Linde 80 surveillance weld metals were studied to characterize the size and distribution of micro-inclusions (&lt; 0.26 μm).
Analytical TEM was used to characterize the carbides, coarse (0.1 to 2.0 μm) inclusions, and fine (2 to 50 run) precipitates. Thin foil and extraction techniques were used to characterize particle morphology while convergent beam diffraction and energy dispersive X-ray techniques were carried out to identify the crystal structural and chemical composition. The results are compared with previously evaluated unirradiated Mn-Mo-Ni wire/Linde 80 flux submerged-arc weld metals.
Characterisation of Model Fe-Cu-Mn-Ti-N Alloys by Electron Microscopy and Positron Annihilation
Authors: Phythian WJ , de Diego N , Mace J , McElroy RJ 
Published: March 2009

It has been recognised for many years that copper plays a significant role in the embrittlement process of reactor pressure vessel (RPV) steels subjected to neutron irradiation. In developing fundamental understanding, and mechanistic models to predict embrittlement, it is important to identify the microscopic mechanisms underlying this phenomena. The purpose of this paper is to discuss recent results obtained from thermal ageing experiments on model alloys doped with copper and nitrogen. These experiments were designed to characterise the material prior to receiving irradiated samples encompassing a wide range of flux, fluence and temperature conditions.
Results will be presented from a microstructural and microchemical examination using transmission electron microscopy (TEM), field emission gun scanning transmission electron microscopy (FEGSTEM) and positron annihilation (PA). Precipitation kinetics have been followed and comparison made between microstructure and measured hardness changes. In alloys containing both titanium and nitrogen, a second form of barrier hardening centre is observed. The insight these studies give into the observed macroscopic hardness increase after irradiation or thermal ageing will be discussed. In particular the implications of a potential further mechanism for embrittlement in commercial steels will be considered.
Effects of Neutron Irradiation on the Notch Ductility of 15MnTi Steel
Authors: Aixin YJ , Han RP 
Published: March 2009

15MnTi steel as a support plate must withstand both the weight of the reactor core of about 100 tons and dynamic loads at 40°C to 50°C. In this study, the steel was embrittled by the neutron irradiation from the reactor core. The ductile-brittle transition temperature was also increased.
The specimens were taken from base plate, weld metal, and weld heat-affected zone. The specimens were irradiated in a swimming pool reactor (SPR).
The test results included impact energy (αk), reference transition temperature (RTNDT), and transition temperature increase (ΔTcv) of 15MnTi steel under the neutron exposure 1 to 2 × 1018n/cm2(E &gt; 1 MeV). The transition temperature was 6°C and 2°C for base plate and weld metal, respectively, after 1 × 1018n/cm2(E &gt; 1 MeV) at 50°C. The transition temperature increase was 40°C, 41°C, and 32°C for base plate, weld metal, and weld heat-affected zone, respectively, after about 2 × 1018n/cm2(E &gt; 1 MeV) at 50°C.
The data of transition temperature increased on 15MnTi steel after 1 to 6 × 1018n/cm2(E &gt; 1 MeV) at 50°C was summarized. An empirical equation was obtained: T = 32.7 - 1.8 lnϕt + 17.8 ln2ϕt, where ϕt is fast neutron exposure (E &gt; 1 MeV).
Tensile Properties of Neutron Irradiated 316Ti and 15-15Ti Steels
Authors: Fissolo A , Lévy V , Séran JL , Maillard A , Royer J , Rabouille O 
Published: March 2009

This paper deals with the tensile behavior of CW316Ti and CW15-15Ti Phénix fuel pin cladding. The tension tests were conducted on defueled tubes irradiated up to 115 dpa3 in the 400–640°C temperature range. Test temperature corresponds essentially to irradiation temperature. The results emphasize that, although irradiation induces a reduction of ductility, the failure always occurs with significant plastic deformation, even for the most highly irradiated cladding.
At irradiation temperatures below 560°C, the embrittlement of both steels is correlated to the swelling and thus to the occurrence of irradiation-induced voids; in this case, the failure is transgranular. In the high irradiation temperature range, a marked difference is observed between the two steels when the tests are conducted at the irradiation temperature, since the rupture is essentially intergranular on CW316Ti and transgranular on CW15-15Ti. The tensile properties of the CW15-15Ti cladding are better than those of CW316Ti because it swells less and is less prone to creep-like embrittlement.
Radiation-Induced Solute Segregation and Stress Corrosion Cracking Study of AISI 304 and AISI 304L Stainless Steels
Authors: Liu WJ , Kai JJ , Tsai CH 
Published: March 2009

Radiation induced solute segregation (RIS) of chromium, nickel, and minor elements (e.g., Si, P, S, etc.) in the vicinity of grain boundaries and its influences on intergranular stress corrosion cracking (IGSCC) of commercial purity AISI 304 and AISI 304L austenitic stainless steels were investigated in this study. High energy protons were used for producing irradiation environment.
Three millimeter TEM discs and miniature tensile specimens were irradiated at 550°C with 1 and 5 MeV H+ individually to doses of 0.01, 0.1, and 1 dpa respectively. Microstructural evolution and radiation-induced solute segregation were studied by using STEM/EDAX microscopy. Constant extension rate tensile (CERT) under various environments were performed using the irradiated miniature tensile specimens to study the relationship between solute segregation and SCC susceptibility of these materials.
Microstructural examination indicated that void swelling was observed in both 304 stainless steels irradiated specimens at the dose of 0.1 dpa and above. Precipitate analysis found that M23C6 carbides were the major precipitates in the as-received (AR) and sensitized (SAS) specimens. Irradiation enhanced precipitation(M23C6 carbides)along grain boundaries was also observed in irradiated AR specimens. It was found that in the irradiated specimens, both Cr and Fe were depleted and Ni and Si were enriched near the grain boundary areas. Proton irradiation induced the nucleation and growth of ferrite phase(bcc) was observed in AISI 304L stainless steels irradiated at 550°C. The size and density of ferrite increased with increasing fluence, and it is found that many M23C6 carbides formed along the interface of F-matrix and ferrite grains.
CERT test indicated that IGSCC accompanying with TG fracture existed in the irradiated region after 1 dpa irradiation and dimples in the unirradiated region. It is found proton irradiation induced the grain boundary etching and surface slip bands which may in turn affect the CERT results in the sense of initiating intergranular cracks.
Influence of Impurities and Alloying Elements on IASCC in Neutron Irradiated Austenitic Stainless Steels
Authors: Kodama M , Fukuya K , Kayano H 
Published: March 2009

Slow strain rate tests (SSRTs) and HNO3/Cr6+ corrosion tests of several types stainless steels irradiated to 5.3×1024n/m2 at about 573K, were conducted to evaluate the correlation between irradiation assisted stress corrosion cracking (IASCC) and radiation induced grain boundary segregation.
All the stainless steels tested failed intergranularly after neutron irradiation. Type 321 and 347 were less susceptible to IASCC than Type 304 and 316. IASCC susceptibility was mitigated by the addition of oversized elements for chromium (for example/ titanium and niobium).
Intergranular corrosion in the HNO3/Cr6+ tests was accelerated due to irradiation in commercial purity (CP) stainless steels, while high purity (HP) stainless steels were immune to corrosion. The occurrence of IASCC in both HP and CP stainless steels indicated that radiation induced impurities enrichment may not be the main contributor to IASCC.
IASCC susceptibility could be correlated to the austenite phase stability and steels of higher austenite phase stability seemed to be less susceptible to IASCC.
Evolution of Microstructure in Zirconium Alloy Core Components of Nuclear Reactors during Service
Authors: Griffiths M , Chow PCK , Coleman CE , Holt RA , Sagat S , Urbanic VF 
Published: March 2009

X-ray diffraction (XRD) and analytical electron microscopy (AEM) have been used to characterise microstructural and microchemical changes produced by neutron irradiation of Zr-2.5Nb, Zircaloy-2 and Zircaloy-4 nuclear reactor core components.
In many cases there is a clear relationship between the radiation damage microstructure and the physical properties of in-service core components. For example, the difference in delayed hydride cracking velocity between the inlet and outlet ends of Zr-2.5Nb pressure tubes in PHWR reactors can be directly correlated with variations in a-dislocation density and β-Zr phase decomposition. For the same tubes, the variation of fracture toughness has the same fluence dependence as dislocation loop density and, in addition, improvements in corrosion behaviour can be linked with decreases in the Nb concentration in the α-Zr matrix due to Nb precipitation during irradiation. For PWR and BWR reactors, the onset of “breakaway” growth in Zircaloy-4 guide tubes can be directly correlated with the appearance of basal plane dislocation loops in the microstructure.
Irradiation Growth of Zirconium Alloys
Authors: Yang JC , Ren JY 
Published: March 2009

Experimental investigation of irradiation growth on annealed Zircaloy-4 and 20% to 50% cold-worked Zr-2.5wt%Nb specimens with stress relief has been carried out. The specimens are irradiated in a heavy water reactor at 610 K to 4.2 x 1024 n/m2 (E &gt; 1.0 MeV). The growth strains increase linearly with fluence. The saturation of growth is not observed for all specimens. The difference of growth behavior between two kinds of Zircaloy-4 tube may be associated with the content of minor alloying elements and impurities that influence the microstructure evolution under irradiation.
The difference of growth strains of cold-worked Zr-2.5wt%Nb at different temperature of stress relief is related to the grain size and shape and the degree of cold work.
Modeling of Sulfide Inclusion Distributions in Relation to the Environmentally Assisted Cracking of Low-Alloy Steels in a Pressurized Water Reactor Environment
Authors: Swan DI , Chapman OJV 
Published: March 2009

Work carried out in the recent past by members of the International Cyclic Crack Growth Rate Group (ICCGRG) has demonstrated the close connection between the occurrence of environmentally assisted cracking (EAC) in low-alloy steels in a pressurized water environment and the presence of sulfide inclusions in the steel. Due to the length of time that experimental work can take, coupled with the sometimes poor repeatability of tests, work was undertaken on a computer model of “sulfide particle” distributions and their interaction with a hypothetical crack front.
The model is basically simple in concept, proceeding in the following manner. An array of randomly located spherical particles, each assumed to consist of a large number of subparticles is set up within a matrix. A crack, exposed to a water environment, is then grown through this matrix, particles intercepted by the crack dissolving; this is modeled by the spreading out of subparticles. Additional factors such as the rate of particle dissolution and rate of subparticle loss from the system are also incorporated into the model. The model is set up to calculate the number of subparticles that congregate at the crack tip. The single premise adopted is that greater than a specified number of subparticles at the crack tip is sufficient to bring about EAC.
In the work discussed here, consideration is given to the relative importance of material sulfur content and second-phase particle size. It was found that the latter had a much greater influence on subparticle numbers at the crack tip than the former. From this, it is concluded that the setting of a bounding curve in Section XI of the ASME Code for modern low sulfur steels would depend more on the occurrence of smaller sulfide particles than the lower sulfur content in such steels. Also considered was the variation of the occurrence of EAC with cycling frequency and stress intensity factor range (ΔK). From the boundaries to the EAC regime, data are obtained that can be applied to the setting of upper bounding curves for the ASME Code.
Environmentally Induced Fatigue Crack Propagation Under Variations in the Loading Conditions
Authors: Schulte K , Nowack H , Lütjering G 
Published: March 2009

In order to evaluate the influence of the environment on the crack retardation behavior under variable loading conditions, high-low block loading tests were performed in vacuum, air, and a 3.5% NaCl (sodium chloride) solution. In an additional test series, variations of the environment from vacuum in the high loading period to air or to 3.5% NaCl solution in the low loading period were performed, and vice versa. These tests, together with an extensive study of the crack surface morphology gave insight into the different fatigue mechanisms induced by the various environments at the crack tip.
A further test series was performed, where the load level was kept constant (constant-amplitude loading) and only the test environment was changed. The results show a variation of the environment from the 3.5% NaCl solution to vacuum causes a retardation in fatigue crack propagation.
Corrosion Fatigue Testing of Welded Tubular Joints Under Realistic Service Stress Histories
Authors: Dharmavasan S , Kam JCP , Dover WD 
Published: March 2009

Because of the large number of stress cycles experienced by offshore structures in the North Sea, fatigue has become a major design consideration for such structures. Extensive research and testing has therefore been carried out to study the fatigue behavior of offshore structural components, particularly the welded tubular joints.
The laboratory technology for fatigue testing of tubular joints has now progressed to the point where realistic in-service stress history can be used. Crack growth results have been obtained with the use of more realistic load histories, coupled With the effects of the environment.
This paper summarizes some of the progress in the design and simulation philosophy for fatigue testing load histories. The latest crack growth data for welded tubular joints tested under realistic fatigue stress histories, in air and in a corrosive environment, are also presented. In most cases, the crack growth can be predicted reasonably accurately with standard fracture mechanics methodology. However, some unexpected crack growth retardation behavior was also observed, and there is currently no established calculation procedure to predict this phenomenon. Therefore, further studies are required to explain this unusual crack growth feature.
Study of Methods for CTOD Testing of Weldments
Authors: Machida S , Miyata T , Toyosada M , Hagiwara Y 
Published: March 2009

Several precracking methods for crack-tip opening displacement (CTOD) testing of weldments were studied, including as local precompression, reverse bending, and high R-ratio fatigue. The precracking procedure could influence the validity of the precrack shape. However, it was found that an irregular precrack front had little effect on CTOD values of the heat-affected zone (HAZ). Results indicate that the current limitations on the fatigue precrack shape can be relaxed.
CTOD values comparable to those of the standard B × 2B specimen were obtained from the subsidiary B × B specimen with a through-thickness notch of a length-to-specimen-width ratio of 0.5. Hence, it can be possible to use B × B specimens instead of B × 2B specimens in the standard CTOD testing of weldments.
The CTOD test results for weld HAZ were strongly affected by the notch positioning in the welded joint. By analyzing the weld thermal history, HAZ microstructures were classified. Then, it was revealed that CTOD values were closely related to the maximum size of the local brittle zone (LBZ) at the crack tip.
A Deformation-Formulated Micromechanics Model of the Effective Young's Modulus and Strength of Laminated Composites Containing Local Ply Curvature
Authors: Lee J-W , Harris CE 
Published: March 2009

A mathematical model based on the Euler-Bernoulli beam theory is proposed for predicting the effective Young's moduli of piecewise isotropic composite laminates with local ply curvatures in the main load-carrying layers. Strains in corrugated layers, in-phase layers, and out-of-phase layers are predicted for various geometries and material configurations by assuming matrix layers as elastic foundations of different spring constants.
The effective Young's moduli measured from corrugated aluminum specimens and aluminum/epoxy specimens with in-phase and out-of-phase wavy patterns coincide very well with the model predictions. Moire fringe analysis of an in-phase specimen and an out-of-phase specimen are also presented, confirming the main assumption of the model related to the elastic constraint due to the matrix layers. The present model is also compared with the experimental results and other models, including the microbuckling models, published in the literature.
The results of the present study show that even a very small-scale local ply curvature produces a noticeable effect on the mechanical constitutive behavior of a laminated composite.
A Fracture Mechanics Based Model for Cumulative Damage Assessment as Part of Fatigue Life Prediction
Authors: Vormwald M , Heuler P , Seeger T 
Published: March 2009

Most fatigue life prediction concepts are based on the transfer of some characteristic material data to the component under consideration. The implicitly assumed equivalence can be limited by various factors including different surface conditions, sizes, residual stress fields, and cumulative damage-related items such as transient endurance limit and load-dependent failure mechanisms. This paper concentrates on aspects related to cumulative damage and presents a model for cumulative damage assessment. It allows prediction of crack initiation life where crack initiation means the occurrence of cracks of an engineering size (≃ 1 mm). Though formulated in terms of a cumulative damage calculation, it is based on the consideration of short crack growth behavior. The main features are: • Consideration of load sequence dependent crack opening and closing levels controlled by the elasto-plastic strain history. • Damage sum (i.e., crack length) dependent decrease of the fatigue limit. • Derivation of a crack-driving parameter based on elasto-plastic fracture mechanics.
An experimental test program including two steels and an aluminum alloy and several types of loading spectra revealed the improved accuracy of the model in comparison with previous approaches. The improvement can be attributed to the consideration of the most important aspects determining the physical process of the formation and growth of short cracks under variable amplitude loading.
Damage Evaluation in Composite Materials Using Thermographic Stress Analysis
Authors: Zhang D , Sandor BI 
Published: March 2009

Damage in composite materials initiates and propagates randomly at many sites, which makes both the monitoring and evaluation of its local and global effects difficult. The recently developed thermographic stress analysis method (TSA) provides unique opportunities for full-field damage investigation. To make quantitative analysis possible, a thermoelasticity theory for damage in anisotropic materials was developed. The TSA method associated with this theory opens new doors in investigating the microstructure-mechanics connection of multiphase materials, and in establishing quantitative prediction capabilities of microscopic behaviors and service lives.Experiments have been performed to measure the damage parameter D, the normalized effective mass density ρc/ρ, and the effective modulus Ec in glass/epoxy [0/90/0/90/0]sand [0/90]5 laminates by the TSA method. Good correlations between the effective moduli of the laminates measured by the TSA method and by an extensometer are found. A relationship between the effective modulus Ec, the undamaged material's modulus E, the number of damaging cyclic loads N, and the peak nominal stress σmax is used to describe the progressive reduction of the modulus. In light of the new thermoelasticity theory for damage, the normalized effective mass density is determined quite easily by the TSA method in comparison with conventional experimental techniques.