A New Nonmetallic Inclusion Rating Method by Positive Use of Hydrogen Embrittlement Phenomenon

A new inclusions rating method using hydrogen embrittlement of a tensile test specimen is proposed. This method is essentially based on the statistics of extremes for inclusion rating where the maximum inclusion size is determined by simple tensile testing of a hydrogen-precharged (H-precharged) specimen. Tensile tests were conducted using two bearing steels (SAE52100 HV 346, HV 447, HV 559, HV 611, HV 678 and ASTM-A485-1 HV 706, HV 715) and one spring steel (SAE5160, HV 651). Fatigue tests were conducted using SAE52100 bearing steel (HV 682). All H-precharged tensile specimens (SAE52100, ASTM-A485-1 and SAE5160) were fractured from internal inclusions except the SAE52100 tensile specimens with a Vickers hardness of HV 346. It was confirmed that the distribution of extreme values of inclusion sizes obtained by SAE52100 tensile testing with H-precharged specimens coincided with those obtained by SAE52100 fatigue testing. From these results, it is presumed that the inclusion rating method by fatigue testing can be replaced by simple tensile testing with H-precharged specimens. The proposed method is more convenient and reliable than other existing inclusion rating methods, i.e., fatigue testing and optical microscopy. The proposed method can be applied to specimens with a Vickers hardness of higher than HV 447.     

Decremental oscillation curve fitting of heart rate response following face immersion into cold water

Sociodemographic differences between rural and urban clients with severe mental illness (SMI) are explored using approaches which extend research in this area beyond limitations found in the few existing studies. Sixteen hundred adult clients from 18 Wisconsin counties are classified according to the degree of rurality of their counties of residence, using two definitions: a dichotomous metropolitan-non-metropolitan grouping and population density. There are significant differences between rural and urban clients for age, gender, and marital status, but not education or income. Young (18-35 years), unmarried males are more likely to live in more densely populated counties. Older (65 and older) women who are currently or previously married are more likely to live in less densely populated counties.     

Optical Fiber Cable Measurements in the Field

The optical fiber cable measurement instruments developed by NTF for field use in the 1.3 μm wavelength are discussed. The properties of a stabilized optical light source for single-mode fiber attenuation measurement, optical time-domain reflectometer using a Q-switched Nd:YAG laser as a light source, and chromatic dispersion measurement instrument are described. From the measurement results, these instruments are revealed to be suitable in constructing and maintaining singlemode fiber optical transmission lines.     

Evaluation of mechanical properties of high-temperature superconducting bulks fabricated by a melt-processing

High-temperature superconducting bulks with highly oriented crystallographic structures are expected to be applied for high field quasi-permanent magnets, current leads and so on. However, the bulks sometimes fracture due to the thermal stress on the cooling process or the electromagnetic force during the magnetization. Thus, it has been recognized that improvement and understanding of the mechanical properties of bulks are indispensable for practical application. In this review, we summarize the present status of evaluation process of the mechanical properties for various bulks. The Young’s modulus, Poisson’s ratio, fracture strength, fracture toughness and hardness are evaluated by tensile, bending, compression and hardness tests. The mechanical properties are anisotropic, mainly due to the crystallographic structure and pre-existing micro-cracks associated with it. Data obtained are summarized and the influential parameters associated with the microstructure and testing condition for the mechanical properties are explained.     

FATIGUE CRACK PROPAGATION AND CRACK CLOSURE BEHAVIOR IN POLYCARBONATE AND FIBRE REINFORCED POLYCARBONATE

Abstract— Fatigue crack propagation was investigated in polycarbonate and glass fibre reinforced polycarbonate and the effect of stress ratio and glass fibre content determined. The addition of glass fibre increases the tensile strength, but does not always contribute to an increase in fatigue crack propagation resistance. For polycarbonate the effect of stress ratio can be partly explained by using crack closure concepts as other researchers have suggested, but for glass fibre reinforced polycarbonate this was not possible. Fractography revealed a void growth process, which occurred by decohesion at the interface of the glass fibres and the base material, which was dependent on the maximum stress intensity factor. The process of linking the voids and the main crack growth behavior depended on the stress intensity factor range, Δ K. A proposed crack propagation model can explain the effect of stress ratio on crack propagation in fibre reinforced polycarbonate.     

Mechanism of carbon microbead formation from paraffin-pitch mixtures

We have proposed a model of carbon microbead formation from the mixture of coal-tar pitch and n-paraffin under mild conditions, supported by results obtained by high-temperature and high-pressure¹H nuclear magnetic resonance and electron spin resonance in conjunction with thermogravimetric and differential thermal analysis. The data obtained by different techniques are in good agreement with each other.     

Numerical analysis of coupled flows in porous and fluid domains by the Darcy-Brinkman equations

A numerical method to achieve the simultaneous computation of the seepage flows in porous media and the Navier-Stokes flows in the domain occupied purely by a fluid is presented in this paper. The method uses the Darcy-Brinkman equations with the continuous modelling of the interfacial flow velocity, and applies the finite volume method to the spatial discretization and the fractional step method to the numerical simulation of the incompressible fluid. The coupling of the two different flows is realized by the relevant interpolation of the pressure and the flow velocity onto the interface at which permeability and porosity are discontinuous. The interpolation schemes provide simple solutions to overcome the computational instability caused by the discontinuous change in permeability and to avoid having to resolve the considerably thin transition zone near the interface. Numerical analyses of the one-dimensional uniform flow, the lid-driven cavity flow, and the pipe-flow in a porous medium have been carried out. The results have shown that the proposed schemes enable a stable computation and fulfill the accurate and physically realistic numerical solutions.