Fracture-mechanics-based evaluation of failure limit on pre-cracked and hydrided Zircaloy-4 cladding tube under biaxial stress states

ABSTRACT

To better understand the failure limit of fuel cladding during the pellet-cladding mechanical interaction (PCMI) phase of a reactivity-initiated accident (RIA), pre-cracked and hydrided cladding samples with base metal final heat-treatment status of cold worked (CW) and recrystallized (RX) were tested under biaxial stress conditions (strain ratios (ε_z/ε_θ) of 0 and 0.5). Displacement-controlled biaxial-expansion-due-to-compression (biaxial-EDC) tests were performed to obtain the hoop strain at failure (failure strain) of the samples. The conversion of the failure strains to J-integrals at failure (J_IC) by finite-element analysis involving data of stress-relieved (SR) cladding specimens from our previous study revealed that the failure limit in the dimension of J_IC unifies the effects of pre-crack depth. About 30–50% reduction in the J_IC value was observed as the strain ratio increased from 0 to 0.5 irrespective of the annealing type, pre-crack depth, and hydrogen content. The rate of fractional decreases of J_IC with increase of hydrogen content is in the order of CW>SR>RX, which are essentially independent of strain ratio for the CW and SR samples. The results were incorporated into the failure prediction model of the JAEA’s fuel performance code in the form of a correction factor that considers the biaxial loading effect.     

Synthesis and properties of thermoplastic expandable microspheres: The relation between crosslinking density and expandable property

A set of thermoplastic expandable microspheres was investigated with respect to their crosslinking density and expandable property. The crosslinking efficiencies of dipentaerythritol hexaacrylate in a set of thermoplastic expandable microspheres were measured. As expandable properties, expansion curves were measured by using a thermomechanical analyzer, and they also were shown by measuring the change of thickness of the coated compound consisting of ethylene–vinyl acetate copolymer resin emulsion and CaCO₃ with thermoplastic microspheres on paper. In view of the expansion ratio and heat resistance, as crosslinking density, a swelling ratio of about 20–25 is needed to achieve optimum expansion without collapse and rupture of microspheres. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 505–512, 2004     

Active coordinated operation of a distribution network system for many connections of distributed generators

Recently, the total number of distributed generators (DGs) such as photovoltaic generation system and wind turbine generation system connected to an actual distribution network has increased drastically. The distribution network connected to many distributed generators must be operated keeping reliability of power supply, power quality, and loss minimization. In order to accomplish active distribution network operation to take advantage of many connections of DGs, a new coordinated operation of distribution system with many connections of DGs is necessary. In this paper, the authors propose a coordinated operation of distribution network system connected to many DGs by using newly proposed sectionalizing switch control, sending voltage control, and computation of available DG connection capability. In order to check the validity of the proposed coordinated operation of distribution system, numerical simulations using the proposed coordinated distribution system operation are carried out in a practical distribution network model. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(3): 46–57, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20655     

High-speed grooving with applying MQL

The performance of minimum quantity lubrication (MQL) in high-speed cutting was evaluated in grooving 0.45%C carbon steel with a carbide tool coated with TiC/TiCN/TiN triple coating layers. MQL with supplying vegetable oil at a small and constant rate of 7 ml/h reduced the corner and flank wears more effectively than a solution type of cutting fluid at high cutting speeds of 4 and 5 m/s. In MQL grooving, the wears decreased drastically with increasing the pressure of air supply. This suggested that the air supply took an important role in transporting the oil mist to the interface between the flank wear land and machined surface. Then, a controlled oil mist direction (COD) tool was devised and its performance was proved to be high at a reduced rate of oil supply.     

Cu-segregation at the Q/α-Al interface in Al–Mg–Si–Cu alloy

Cu segregation was detected at the Q^′/α-Al interface in an Al–Mg–Si–Cu alloy by energy-filtered transmission electron microscopy. By contrast, in a Cu-free Al–Mg–Si alloy no segregation was observed at the interface between the matrix and Type-C precipitate.     

Electrophysiological characteristics of submucosal neurones in the proximal colon of guinea-pigs: comparisons with caecum and descending colon

A systematic examination has been made of the active and passive electrophysiological properties and synaptic inputs of forty-four randomly impaled submucosal neurones in the proximal colon of the guinea-pig to compare these characteristics directly with those of submucosal neurones in the caecum (n = 70) and descending colon (n = 45). Within each of the three electrophysiological classes of submucosal neurones identified (S, S/AH and AH), no statistically significant regional differences were found with respect to the resting membrane potential, membrane time constant or input resistance between neurones of the proximal colon, descending colon and caecum. Of submucosal neurones from the proximal colon, forty-three of forty-four (98%) received fast excitatory synaptic potentials (fast EPSPs); thirty-nine (91%) were S neurones and the others were S/AH neurones; only one of the forty-four cells (2%) was an AH neurone. An idazoxan-sensitive slow inhibitory postsynaptic potential (slow IPSP) was induced in thirty of forty-three S and S/AH neurones (70%) of the proximal colon, compared with sixty-one of sixty-six caecal neurones (92%) and twelve of forty-one neurones (29%) in the descending colon. The mean (+/- S.E.M.) amplitude of the slow IPSP in proximal colonic neurones was 17 +/- 1 mV (range, 6-30 mV; n = 30), compared with the significantly larger synaptic response (25 +/- 1 mV; range, 7-38 mV; n = 66; P < 0.05) recorded in the caecum; the mean slow IPSP amplitude in the descending colon was significantly smaller (12 +/- 2 mV; range, 5-27 mV; n = 12; P < 0.05) than that in the caecum. In the proximal colon and caecum, only those neurones with a slow IPSP had a hyperpolarizing response to noradrenaline, whereas about 50% of those neurons of the descending colon that lacked a slow IPSP were hyperpolarized by noradrenaline, acting via alpha 2-adrenoceptors. Thus, the electrophysiological characteristics of the submucosal neurones of the proximal colon more closely resemble those of the caecum than those of the descending colon, of which many do not have a functional noradrenergic synaptic input. Furthermore, the results confirm that there are fundamental regional differences in the guinea-pig large intestine with respect to the synaptic organization of submucosal neurones of particular electrophysiological classes.     

Control of molecular packing structure of a derivative of vanadyl-phthalocyanine using pore wall of porous alumina and/or magnetic field

We filled one-dimensional alumina pores with a molten derivative of vanadyl-phthalocyanine (VOPcHt) and evaluated the effect of the surface of pore wall on the molecular packing structure of VOPcHt. We also evaluated the effect of a magnetic field of 5.0 T on the packing structure of VOPcHt that was solidified on a flat substrate. X-ray diffraction measurements revealed that both the surface effect as well as the magnetic field controlled the packing structure of VOPcHt. When both the pore wall and the magnetic field existed, the surface effect was dominant in the control of the packing structure. These results provide practical methods to fabricate nanostructures of organic molecules with a controlled molecular packing structure.     

Syntheses and electronic behaviors of net-worked,alternating hafnium-organic moiety hybrid copolymers

Hafnium-organic moiety hybrid copolymers were prepared by reacting hafnium n-butoxide with organic diols. ESR spectral examinations of copolymers and ab-initio calculations of copolymer models suggest that an electron transfer from organic group to hafnium atom takes place.     

Dynamic mechanical properties of paper containing a polyacrylamide dry‐strength resin additive and its distribution within a fiber wall: Effect of the application method

Laboratory handsheets made from lightly beaten hardwood kraft pulp containing various amounts of cationic‐type polyacrylamide (PAM) dry‐strength resin were prepared by both internal and external application methods. We performed the internal application by adding a dilute aqueous PAM solution to a pulp fiber suspension, whereas we performed the external application by dipping a dry paper (handsheet) into an aqueous PAM solution and further squeezing it out with or without the standard wet press. Attenuated total reflection/Fourier transform infrared analysis combined with a gradual etching method was used to clarify the difference in the depth profiles of PAM within a fiber wall between these application methods. For the internal application method, PAM existed, on the whole, mainly close to the fiber surface and slightly distributed from the fiber surface toward the center of the fiber wall. On the other hand, for the external application method, PAM existed mainly on the fiber surface and around the fiber‐to‐fiber bonds. Dynamic mechanical properties of the papers containing PAM were measured at temperatures ranging from 100 to 300°C and at the various frequencies. In case of addition by the internal method, no characteristic viscoelasticity of PAM appeared. On the other hand, external method addition at the nearly same retention level of PAM gave the characteristic viscoelasticity. These findings suggest following things: when cationic‐type PAM dry‐strength resin was applied by the internal method, the PAM distributes within the fiber wall in a molecularly dispersed state. The induced state of PAM within the fiber wall, with no existence of a phase of PAM, led to the disappearance of the viscoelasticity of the PAM. On the other hand, the external application method brought about the PAM distribution around the fiber‐to‐fiber bonds and over the fiber surface. The induced state of PAM, the existence of a kind of PAM phase, led to the appearance of the viscoelasticity of the PAM itself. Dynamic mechanical analysis may be a good method for examining whether PAM is molecularly distributed or making aggregates in paper and other polymer composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Drying Characteristics In Superheated Steam Drying at Reduced Pressure

The superheated steam drying at reduced pressure is performed, and the effects of operational conditions such as drying pressure and temperature on the drying characteristics are examined. In order to obtain the basic guideline for the design of the superheated steam dryer at reduced pressure, the heat flux to sample was calculated and the optimal conditions were estimated.

After the sample temperature reached at the boiling point, the temperature was maintained at the boiling point and the drying rate became almost constant. Once the sample was dried out, the temperature suddenly increased up to the drying gas temperature. From the calculation of combined heat flux, the followings were found. The contribution of radiative heat transfer to the combined heat flux became larger as the drying pressure was lower. The combined heat flux had a maximum value against the drying pressure. The optimum drying pressure, which gave the maximum heat flux, became lower as the drying gas temperature decreased. It was found that reduction in the drying pressure is effective for the enhancement in drying performance.