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論文 |
論文
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神宮, 利夫 ; 川端, 一司
概要:
application/pdf<br />Journal Article<br />The misalignment of the flat anvil of a testing machine with the end of a circular rod specimen causes local crushing due to the stress concentration and bending moment, which must be avoided in
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compression tests. When very hard material, such as fine ceramics, is tested using the compression split Hopkinson bar, the hard specimen may be indented into the incident and transmission bars. In this paper, the insertion of a thin metal plate between the bar-specimen interface in the conventional compression split Hopkinson bar system was examined to prevent indentation. The stress pulse in the incident and transmission bars is measured using the thin steel plate (thickness 0.4 and 1 mm), copper (1 mm) and aluminium (1 mm) , and the pulse profile is investigated. The configuration of the wave observed using the thin steel plate (0.4 mm) is the sharpest, and is similar to that without the plate. The rise of pulses using the steel plate (1 mm) is ramplike. With use of a copper plate and aluminium, the two-step profile appears. The stress-strain relationship evaluated from these stress pulses was compared with that obtained in the static test. The dynamic strength of ceramics is less than about half the static strength.
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| 2.
論文 |
論文
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神宮, 利夫
概要:
application/pdf<br />Journal Article<br />The strength of unidirectionally reinforced carbon/epoxy composites (CFRP) subjected to the compressive impact load was measured by the Split Hopkinson Pressure Bar Method (S. H. P. B. M),
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then the effect of fiber orientation on the compressive impact strength was investigated. Stress of the specimen, caused by multiple reflected stress waves at its ends in contact with the incident bar and transmitter, was analysed based on one-dimensional stress wave theory. The resulting formulation can be used to evaluate either the linear or nonlinear stress-strain relation. The strength of a specimen of zero-degree fiber is the greatest. The strain of a specimen of 45-degree fiber is the largest. A split fracture parallel to the fiber appeared in the specimen of zero-degree fiber. Inclination of the fracture surface of specimens of 30-, 45- and 60- degree fiber is in alignment with the fiber orientation. Tat of 90 degrees is not. The impact strength is about 80 MPa larger than the static strength. In contrast, the dynamic elongation is smaller than the static elongation.
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