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Measurements of strain-rate distributions on material after SHPB impact

Kawai M., Futakawa M., Naoe T., Yamada H., Xu C. N.

Engineering Transactions

2011

Vol. 59, iss. 1

13-21

We have proposed a sophisticated novel method of the SHPB experiment to measure the local strain-rate distributions on a surface of the specimen by using mechanoluminescent materials combined with a high-speed camera and an image intensi?er. The feasibility study was made for the aluminum specimens pasted by a typical mechanoluminescent material -Eu doped SrAl2O4 ?lm, in order to obtain the fundamental data for the method. Our results showed that SrAl2O4: Eu emitted lights as a response to the stress. Increase of the light intensity was swift enough to follow the strain change due to SHPB impact. The luminescence intensity was experimentally veri?ed and expressed as a product of strain and strain rate. Accordingly, it can be said that this method gives a good tool for measuring time variation of local strain distributions.

Multiaxial constitutive modelling for R-phase and M-phase transformations of TiNi shape memory alloys

Kawai M., Ogawa H., Baburaj V., Koga T.

Archives of Mechanics

1999

Vol. 51, nr 6

665-692

A multiaxial constitutive model for describing the pseudoelastic and shape memory behaviour of a titanium-nickel (TiNi) shape memory alloy due to the stress-induced rhombohedral and martensitic transformations has been developed from a phenomenological point of view. First, the existing constitutive models proposed for shape memory alloys are reviewed in brief. On the basis of a comparison between these models, an expression prescribing the transformation strain range is proposed which depends on the applied stress and the current phase volume fraction. Then, the uniaxial Tanaka model for the rhombohedral and martensitic transformations of TiNi shape memory alloys is extended to a multiaxial form using the framework of the Boyd-Lagoudas model and the proposed expression of the transformation strain range. Finally, the capability of the present model to predict the pseudoelastic behaviour of TiNi shape memory alloys is examined through numerical simulations of stress-strain responses under uniaxial and multiaxial proportional/nonproportional loading-unloading conditions.

PtSi Schottky-barrier infrared focal plane arrays

Kimata M., Ueno M., Yagi H., Shiraishi T., Kawai M., Endo K., Kosasayama Y., Sone T., Ozeki T., Tsubouchi N.

Opto-Electronics Review

1998

Vol. 6, No. 1

1-10

The focal plane array (FPA) technology based on the PtSi Schottky-barrier (SB) photoemissive detector is presented. Taking advantage of Si-compatible manufacturing processes and high responsivity uniformity, we have developed a series of 2-dimensional PtSi SB FPAs with array sizes from 256 x 256 to 1040 x 1040 elements for medium wavelength thermal imaging, and two spaceborne long linear FPAs with 4096-element x 4-band and 2100-element x 6-band for short wavelength remote sensing applications. Along with design and performance of the FPAs, this paper reports on the Charge Sweep Device readout architecture, which is a key technology for high performance 2-D FPAs. A high reliability and high planarity packaging technology for large FPAs is also described.