Damage characterisation of fibre metal laminates under interlaminar shear load

Transverse composite plies are part of the fibre metal laminate Glare^®4B and were investigated under interlaminar shear load. Double-notched shear (DNS) tests were performed and deformation and damage were in situ observed by Scanning Electron Microscopy (SEM) equipped with a loading apparatus. Interlaminar shear strength as well as shear stress values corresponding to the onset of the fibre/matrix-debonding were determined.Although a cross-ply lay-up within the laminate has been interlaminar shear loaded, damage and failure could only be found within the transverse plies. Over their thickness, fibre/matrix-debonding proved to be pronounced near the ply boundaries of the transverse plies, where exceptionally high shear strains could be found. Nevertheless, single fibre/matrix-debonding phenomena were also observed within the centre area of these transverse plies. Although interlaminar shear strain within latter regions is reduced, single events of fibre/matrix-debonding could be attributed to local high stress concentrations due to the fibre arrangement and to small inter fibre distances.     

Thermal diffusivity and porosity of solid materials by the electromagnetic ultrasonic technique. Part 3—simultaneous measurement of ultrasonic velocity and thermal diffusivity

The objective of this study is to evaluate simultaneously the time dependence of the thermal diffusivity of carbon-carbon composites (C/C composites) and their porosity during heat treatment using the electromagnetic ultrasonic technique. This paper describes two kinds of experiments conducted to confirm the principle for simultaneous measurement of both the ultrasonic velocity (used to evaluate the porosity) and the thermal diffusivity at room temperature. For each material, the samples used in both experiments were identical. The ultrasonic velocity of type 304 stainless steel and its thermal diffusivity were 5.85 km/s and 3.8 mm²/s with precisions of ±1.6 and ±8 percent, respectively. The ultrasonic velocity of a two-dimensional woven C/C composite and its thermal diffusivity were 2.86 km/s and 4.8 mm²/s with precisions of ±5.0 and ±8 percent, respectively. The results appear to indicate that the electromagnetic ultrasonic technique can measure the ultrasonic velocity and the thermal diffusivity simultaneously and that it is also applicable to C/C composites. © 1997 Scripta Technica, Inc. Heat Trans Jpn Res, 25(5): 308–322, 1996     

Response Threshold Models for Binary Ranking and Sorting

The present paper provides two response models: one for binary ranking and the other for sorting. The former is a behavior of choosing, in a random order, only those comparison stimuli which are judged to be very similar to a standard stimulus, and the latter is that of selecting stimuli which are judged very similar to each other to form them into clusters. The key assumption of these models is that the subject perceives any two stimuli as very similar to each other when their dissimilarity, which varies over time, is below response thresholds that are associated with those stimuli. Maximum likelihood estimation procedures are used for the estimation of parameters of these models. The proposed models are applied, for illustrative purposes, to the similarity data collected by the binary ranking and sorting methods. We discuss some advantages of the binary ranking method to be used for collecting similarity data and a practical limitation of our response model for sorting.

     

Multiple cracking of a coating layer and its influence on fibre strength

Multiple cracking of a coating layer and its influence on the tensile strength of the coated fibre in the case of strong interfacial bonding were simulated by means of a Monte Carlo method. Within the range where the coating layer was weak, it was found that the weaker the coating layer, the larger became the number of cracks and consequently the smaller became the crack spacing, resulting in higher strength of the fibre. When the strength of the layer was high, however, the crack spacing became large, resulting in a low strength of the fibre comparable to the strength for the case of single cracking. The strength value of the fibre calculated for average crack spacing gave an upper bound, and that calculated for single cracking a lower bound, for the actual fibre strength.     

A simple facility to measure the scalar neutron spectrum in an assembly

An inexpensive, simple and safe facility was constructed to measure the neutron spectrum in an assembly, by setting a neutron source outside the assembly. A normalization technique for the neutron spectrum and error analyses are mentioned. The error of the calculated spectrometer efficiency is cancelled at the final spectrum normalization. The error caused by the present method is within acceptable levels.     

Inhibitory effect of nicotinamide to paraquat toxicity and the reaction site on complex I

The inhibitory effect and mechanism of action of nicotinamide to paraquat toxicity were studied in male Sprague-Dawley rats. Proteins of submitochondrial particles (SMP), especially of mol. wt. 25-30 kDa, in rat lungs were destroyed by paraquat radicals, and aggregated protein bands approximately 100 kDa were observed by polyacrylamide electrophoresis. The competitive inhibition effects were observed of nicotinamide on NADH oxidation by paraquat via SMP in rat lungs and the Ki was 9.3 mM. The inhibitory effects of nicotinamide on lipid peroxidation by paraquat with rat lung and liver SMP were verified. The times of occurrence of dyspnea and death in rats after paraquat exposure were delayed by nicotinamide administration. The activity of NADH: ubiquinone reaction of NADH:ubiquinone oxidoreductase (complex I) in rat lung was reduced 24 h after paraquat exposure, and was protected by nicotinamide. The activity of NADH:ferricyanide reaction of complex I was, however, reduced by administration not only of paraquat but also nicotinamide. These results imply that nicotinamide is inhibitory to paraquat toxicity. Nicotinamide, paraquat, and ferricyanide may react at overlapping sites on complex I.     

Status of ion sources at National Institute of Radiological Sciences

The National Institute of Radiological Sciences (NIRS) maintains various ion accelerators in order to study the effects of radiation of the human body and medical uses of radiation. Two electrostatic tandem accelerators and three cyclotrons delivered by commercial companies have offered various life science tools; these include proton-induced x-ray emission analysis (PIXE), micro beam irradiation, neutron exposure, and radioisotope tracers and probes. A duoplasmatron, a multicusp ion source, a penning ion source (PIG), and an electron cyclotron resonance ion source (ECRIS) are in operation for these purposes. The Heavy-Ion Medical Accelerator in Chiba (HIMAC) is an accelerator complex for heavy-ion radiotherapy, fully developed by NIRS. HIMAC is utilized not only for daily treatment with the carbon beam but also for fundamental experiments. Several ECRISs and a PIG at HIMAC satisfy various research and clinical requirements.     

Microstructural and Thermoelectric Characteristics of Zinc Oxide-Based Thermoelectric Materials Fabricated Using a Spark Plasma Sintering Process

M-doped zinc oxide (ZnO) (M=Al and/or Ni) thermoelectric materials were fully densified at a temperature lower than 1000°C using a spark plasma sintering technique and their microstructural evolution and thermoelectric characteristics were investigated. The addition of Al₂O₃ reduced the surface evaporation of pure ZnO and suppressed grain growth by the formation of a secondary phase. The addition of NiO promoted the formation of a solid solution with the ZnO crystal structure and caused severe grain growth. The co-addition of Al₂O₃ and NiO produced a homogeneous microstructure with a good grain boundary distribution. The microstructural characteristics induced by the co-addition of Al₂O₃ and NiO have a major role in increasing the electrical conductivity and decreasing the thermal conductivity, resulting from an increase in carrier concentration and the phonon scattering effect, respectively, and therefore improving the thermoelectric properties. The ZnO specimen, which was sintered at 1000°C with the co-addition of Al₂O₃ and NiO, exhibited a ZT value of 0.6 × 10⁻³ K⁻¹, electrical conductivity of 1.7 × 10⁻⁴Ω⁻¹·m⁻¹, the thermal conductivity of 5.16 W·(m·K)⁻¹, and Seebeck coefficient of −425.4 μV/K at 900°C. The ZT value obtained respects the 30% increase compared with the previously reported value, 0.4 × 10⁻³ K⁻¹, in the literature.