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This paper describes the creep characteristics of three kinds of electrolytic copper thin films. Tensile creep and creep rupture tests were performed using three kinds of electrolytic copper thin films with 30mm gage length, 5mm width and 12μm thickness at 353K, 373K, 398K and 423K. The electrolytic copper plating thin films were direct current thin films (DC), periodic reverse pulse thin films (PL) and via fill thin films (VF). The DC and VF showed the same creep rupture lifetimes which were longer than those of the PL. Clear transient and steady creep stages were found in these kinds of the thin films but no acceleration creep stage was found. The minimum creep strain rates of the PL were faster than those of the DC and VF, which corresponded well with the creep rupture lifetimes. The thin film that yielded the faster creep strain rate had the shorter creep rupture lifetime. The relationship between the minimum creep strain rates and rupture lifetimes was well expressed by the Monkman-Grant equation. This implies that the creep rupture lifetime was mainly controlled by the creep deformation rate so that the thin film that has slower creep strain rate is preferable to use in electric devices because it has a stronger creep resistance. The creep rupture lifetimes at different temperatures were well correlated with the Larson-Miller parameter for each film. The correlation indicates that the temperature acceleration testing is performable to obtain the longer creep rupture lifetimes from the relatively shorter creep testing.

The dynamic shear modulus in torsion (G'), water absorption, thermal expansion and residual monomer of the reinforced materials produced by adding four short glass fibres (19 microm in mean diameter and 86.1--763 microm in mean length) and one spherical E glass (11.1 microm in mean diameter) were examined and discussed in comparison with those of the materials without filler. G' of short fibre reinforced composites increased with fibre length and reached a maximum value near 382 microm for a dry specimen and near 156 microm for a wet one. In addition, the coefficient of thermal expansion of the fibre reinforced composites and the amount of residual monomer decreased considerably compared with those of composites containing spherical glass. There was no significant difference in water absorption between the fibre reinforced composites and the composites containing spherical glass. Therefore, it was concluded that the reinforcement method of adding short glass fibres is favourable for improving the viscoelastic properties of the materials.

This study discusses fatigue properties of low carbon steel under multiaxial non-proportional loading and an evaluation of failure life. Multiaxial fatigue tests under non-proportional loading with various stress amplitudes were carried out using a hollow cylinder specimen in low and high cycle regions at room temperature. In the test, three types of strain/stress path were employed. They are a push-pull, a reversed torsion and a combined push-pull and reversed torsion loadings in which stress amplitudes used were constant and random. This study evaluates an effect of non-proportional loading on fatigue life in the high cycle fatigue region to discuss the applicability of ΔεNP proposed by Itoh et al. on life evaluations in the high cycle region and under random loading.

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