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143 results on '"Tsutomu UMEDA"'

102. Application of Damage Mechanics to the Analysis of Spall Damage

Author

Masaharu Itoh, Hiroshi Takizawa, Tsutomu Umeda, and Sumio Murakami

Subjects
Materials science, Viscoplasticity, business.industry, Mechanical Engineering, Constitutive equation, General Engineering, Finite difference method, Finite difference, Damage analysis, Structural engineering, Mechanics, Spall, Nonlinear system, Stress wave, Mechanics of Materials, Damage mechanics, General Materials Science, Particle velocity, business
Abstract

A systematic method of spall damage analysis was developed on the basis of damage mechanics. By use of a scalar damage variable, the damage evolution equation of Lemaitre et al. and the viscoplastic constitutive equation of Perzyna modified for the damaged materials were incorporated into the commercial finite-difference program MANJUSRI-3 D for nonlinear dynamic analysis. The process of spall damage and histories of stress wave propagation and temperature were analyzed for plate impact of OFHC copper disc targets. The results of analysis of the stress history and the particle velocity at the rear surface of the target plate were compared with those of the corresponding experiments.

Published
1994
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103. Mechanical Properties of a Langmuir−Blodgett Film Measured by Atomic Force Microscopy

Author

Kazuaki Suehiro, Miyuki Kuramori, Yushi Oishi, and Tsutomu Umeda

Subjects
Kelvin probe force microscope, Materials science, Atomic force microscopy, Electrochemistry, General Materials Science, Nanotechnology, Surfaces and Interfaces, Conductive atomic force microscopy, Condensed Matter Physics, Langmuir–Blodgett film, Spectroscopy, Photoconductive atomic force microscopy
Published
2002
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105. STUDY OF ACCURATE HIGH-SPEED TENSION TESTING METHOD

Author

Tsutomu Umeda and Koji Mimura

Subjects
Accuracy and precision, Materials science, business.industry, Stress–strain curve, Statistical and Nonlinear Physics, Dynamic Tension, Split-Hopkinson pressure bar, Structural engineering, Condensed Matter Physics, Load cell, Finite element method, business, Strain gauge, Tensile testing
Abstract

The high measurement accuracy in dynamic tension testing is required for designs and numerical simulations based on the accurate modeling of stress–strain relations at various strain-rates. The non-coaxial Hopkinson bar method (NCHBM) is one of the recently proposed methods for dynamic tension tests. In this study, the direct measurement of both stress and strain was conducted by using the strain gauges affixed on the special specimen with load cell part. The stress–strain relations obtained by this revised NCHBM were compared with those obtained by the normal NCHBM. In order to verify the experimental results, some numerical models were examined by using the FEM code LS-DYNA, in which the whole finite-element model of the apparatus and the plate-type specimen were made in detail. Furthermore, new appliances for fixing specimen were examined by experiment. The target material employed in this study is SUS316.

Published
2009
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