Gigacycle fatigue data sheets for advanced engineering materials

Gigacycle fatigue data sheets have been published since 1997 by the National Institute for Materials Science. They cover several areas such as high-cycle-number fatigue for high-strength steels and titanium alloys, the fatigue of welded joints, and high-temperature fatigue for advanced ferritic heat-resistant steels. Some unique testing machines are used to run the tests up to an extremely high number of cycles such as 10¹⁰ cycles. A characteristic of gigacycle fatigue failure is that it is initiated inside smooth specimens; the fatigue strength decreases with increasing cycle number and the fatigue limit disappears, although ordinary fatigue failure initiates from the surface of a smooth specimen and a fatigue limit appears. For welded joints, fatigue failure initiates from the notch root of the weld, because a large amount of stress is concentrated at the weld toe. The fatigue strength of welded joints has been obtained for up to 10⁸ cycles, which is an extremely high number of cycles for large welded joints. The project of producing gigacycle fatigue data sheets is still continuing and will take a few more years to complete.     

Oxidative degradation of polymers. II. Thermal oxidative degradation of atactic polypropylene in solution under pressure

Atactic polypropylene was oxidized in solution in the presence and absence of radical initiator over the temperature range of 140° to 200°C under oxygen pressure of 3.3 to 12.4 kg/cm², and the effects of metal catalyst and additives on the rate, products, and change in molecular weight distribution were measured. The synergistic effect was observed with cobalt and managanese salts. The deactivation of the metal catalyst was suppressed by the addition of acetic acid and acetic anhydride as solvent. The rate of oxidation increased with increasing temperature, but the decrease in molecular weight was nevertheless not so significant as to give many low-boiling products. However, the production of mixtures of acid, ketone, alcohol, and ester with molecular weights of several hundreds was promising. The refractive index of polypropylene decreased markedly as the oxidation proceeded, and the complications involved in the determination of the change in molecular weight distribution measured by gel permeation chromatography are discussed.     

The action modes of an extracellular beta-1,3-glucanase isolated from Bacillus clausii NM-1 on beta-1,3-glucooligosaccharides

The mode of action of an extracellular -1,3-glucanase from Bacillus clausii NM-1 on beta-1,3-3glucooligosaccharides and their alditols was studied. The enzyme could not hydrolyze laminaribiose or laminaritriose. beta-1,3-Glucooligosaccharides higher than laminarihexaose were rapidly hydrolyzed, while laminaritetraose was slowly hydrolyzed. The k(cat)/K(m) ratios for a series of beta-1,3-glucooligosaccharides from laminaritetraose to laminariheptaose showed that the substrate binding site of the enzyme covered a wide range of beta-1,3-glucooligosaccharides having six glucose residues. The action pattern of the enzyme on the alditols corresponding to each laminarioligosaccharide suggested that the catalytic site of the enzyme existed between the third and fourth glucose residue from the non-reducing terminal. The value of k(cat)/K(m) also suggested that the sixth binding position contributed to the catalytic efficiency and stability.     

Natural-looking strokes for drawing applications

This paper presents an algorithm for generating realistic drawing strokes in real-time that can take on the appearance of pastels, charcoals, or crayons. The similarity between the pigment deposit patterns on paper surfaces produced by pastel strokes and the shadows/shades on illuminated paper surfaces have been investigated. Multiple paper textures have been prepared and the paper surfaces have been ascertained by illumination from various directions to represent strokes in arbitrary directions. These textures have been processed as if they could be used as a height field, and pigments deposited on the paper have been calculated using the height field and tablet inputs.     

Influence of stress ratio on the threshold level for fatigue crack propagation in high strength steels

Centrally cracked specimens of JIS SM58Q and HT80 steels were fatigued. The fatigue crack growth rates, da/dn, and the stress intensity threshold levels, ΔK_th were measured over the range of stress ratio, R, from ?1 to 0.8 by the use of an automatic method of continuously decreasing stress intensity factor with crack extension. The measured ΔK_th was well represented as |ΔK_th/2|_R=(1?R)γ|ΔK_th/2|_R=0; and the propagation rate, as da/dn = A(1?R)^γm[(ΔK/2)^m ? {(1 ? R)^γ|ΔK_th/2|R=0}^m] for ?1≦R≦0.33 or da/dn = A(1 ? 0.33)^?γm [(ΔK/2)^m {(1 ? R)^γ |ΔK_th/2|R=0}^m] for 0.33 < ≦ 0.8.     

Effect of tool stiffness upon tool wear in high spindle speed milling using small ball end mill

Longer tool life can be tentatively achieved at a higher feed rate using a small ball end mill in high spindle speed milling (over several tens of thousands of revolutions per minute), although the mechanism by which tool life is improved has not yet been clarified. In the present paper, the mechanism of tool wear is investigated with respect to the deviation in cutting force and the deflection of a ball end mill with two cutting edges. The vector loci of the cutting forces are shown to correlate strongly with wear on both cutting edges of ball end mills having various tool stiffnesses related to the tool length. The results clarified that tool life can be prolonged by reducing tool stiffness, because the cutting forces are balanced, resulting in even tool wear on both cutting edges as tool stiffness is lowered to almost the breakage limit of the end mill. A ball end mill with an optimal tool length showed significant improvement in tool life in the milling of forging die models.     

Packaging technology for 40-Gb/s optical receiver module with anMU-connector interface

A compact 40-Gb/s optical receiver module with an MU-connector interface has been developed. Its packaging has three main technical features. (1) Coplanar waveguide (CPW) patterns of the waveguide photodiode (WG-PD) and of the preamplifier IC in the facing area of the flip-chip structure are optimized for impedance matching. (2) A film carrier is used to connect the preamplifier IC to an electrical coaxial connector for electrical signal output. (3) An MU-connector is used as the optical interface to reduce the module size. Optimum design enabled a module size of 14.0 mm wide, 40.4 mm long, and 9.65 mm high. Measurements showed a 3-dB down bandwidth of the optical/electrical response of at least 50 GHz and a clear open eye pattern for a 40-Gb/s nonreturn-to-zero (NRZ) signal input. This optical receiver module is suitable for large-capacity communication network systems     

SEM and TEM characterization of magnesium hydride catalyzed with Ni nano-particle or Nb2O5

The microstructures of MgH₂ catalyzed with Ni nano-particle or Nb₂O₅ mesoporous powders are examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. For MgH₂ catalyzed with Ni, the Ni particles with the diameter smaller than 1 μm were detected on the MgH₂ particles with the diameter smaller than 5 μm by the back scattering electron (BSE) microscopy. In details, the TEM micrograph indicates that the Ni particles distribute 20 nm in diameter on MgH₂ uniformly, which was the same size as the additive doped in MgH₂ before milling. On the other hand, for MgH₂ catalyzed with Nb₂O₅, the additive particles could not be found anywhere in the BSE image. Even in the TEM micrograph by much larger magnification than the SEM micrograph, the particles corresponding to the additive cannot be observed at all. Furthermore, an energy dispersive X-ray (EDX) analysis in spots with a diameter of 20 nm indicated that the existing ratio of Mg to Nb was evaluated to 98:2, being the same as the starting ratio before milling. Therefore, the metal oxide Nb₂O₅ becomes extremely small particle that could not be observed by the present work after milling compared to metal Ni^nano.