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ABSTRACT. Stress controlled multiaxial fatigue test was carried out using a hollow cylinder specimen of type 316 stainless steel. A newly developed fatigue testing machine which can apply push-pull loading and reversed torsion loading and inner pressure to the hollow cylinder specimen was employed. 5 types of cyclic loading paths were employed by combining zero to pull axial and hoop stresses: a Pull (only axial stress), an Inner-pressure (only hoop stress), an Equi-biaxial (equi-biaxial stress by axial and hoop stresses), a Square-shape (trapezoidal waveforms of axial and hoop stresses with 90-degree phase difference) and a L-shape (alternately axial stress and hoop stress) loading paths. Since directions of principal stresses are fixed in all the tests, all of the loading paths are classified into 'proportional loading'. In the Pull, the Inner-pressure and the Equi-biaxial tests, fatigue lives can be correlated on a unique line by a maximum equivalent stress based on von Mises. On the other hand, fatigue lives in the Square-shape and the L-shape tests were reduced comparing with that in the other tests, which was caused by yielding of larger plastic deformation.

The purpose of this study is to investigate the effects of the fiber unbundling on the mechanical properties of carbon fiber reinforced thermoplastic (CFRTP) fabricated using discontinuous carbon fibers and polypropylene. Tensile test and puncture impact test were performed using CFRTP of which the volume fractions (Vf) were 10, 20, and 30 %. The wet type of unbundling treatments, which applied the water flow with shearing forces, were given to carbon fiber bundles with 5 and 10 mm lengths. Tensile strength and puncture energy of CFRTP were improved by the effects of fiber unbundling in spite of the same Vf. The amount of strain at the maximum tensile stress also increased with the progress of fiber unbundling. The effects of fibers unbundling on mechanical properties were obtained even in the small-scale of unbundling treatments which still remained a certain amount of fiber bundles in CFRTP. However, it was difficult to obtain the effects of improving mechanical properties in the condition of high Vf using long fibers (10 mm) due to the occurrence of the deviation of fiber direction.

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If a K3 surface admits an automorphism with a Siegel disk, then its Picard number is an even integer between 0 and 18. Conversely, using the method of hypergeometric groups, we are able to construct K3 surface automorphisms with Siegel disks that realize all possible Picard numbers. The constructions involve extensive computer searches for appropriate Salem numbers and computations of algebraic numbers arising from holomorphic Lefschetz-type formulas and related Grothendieck residues.