We present a new approach on the multi-scale, multi-physics computational biomechanics in cardiovascular system (CVS), which is established to be capable to reasonably predict the cardiovascular functions and the biomechanics of arteries and heart under physiological and pathological conditions. This simulator is composed of four computational models involving an anatomically realistic, three-dimensional arterial tree model, a closed-loop, lumped-parameter compartment model of the global CVS, a systematic control model of the autonomic nervous system (ANS) with consideration of the cerebral auto-regulation (CA), and an image-based three-dimensional CFD model of the local arteries and organs. Our results demonstrate that the physiological conditions are of great significance, which points to the importance of the multi-scale and multi-physical modeling of the biomechanics and mechanobiology in the CVS.

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In this research, the buckling behavior of long columns subjected to dynamic loads was investigated both experimentally and numerically, and an effective buckling criterion for the dynamic load with the limited time duration was described in terms of the slenderness ratios. In order to validate the proposed criterion, the dynamic FEM code 'MSC. Dytran' was used to simulate the typical experimental results, and the validity and the accuracy of the proposed model were examined. Furthermore, the dynamic buckling loads at various impact speeds were systematically investigated. From the results, it was found that the ratio of the dynamic load to the static load was expressed as a square function of the slenderness ratio of the long columns.

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MD simulations of dislocation behavior in KCl under shock compression along the [100], [110] and [111] axis directions are carried out to investigate the elastoplastic transition under shock compression. The dislocations moved along to 45 degrees to the compression direction due to the displacement of atomic lines around its dislocation core. This result is consistent with the Von-Mises hypothesis. Under shock compression along the [111] axis direction, simulation results showed that two edge dislocations were generated due to that two extra half-(011) planes were inserted. The minimum stress for dislocation motion under shock compression along the [111] axis direction was much larger than those under shock compression along the [100] and [110] axis directions. It was suggested that the large stress was caused by the existence of two edge dislocations which were generated by two extra half-(011) planes. The result is consistent with the experimental ones that the Hugoniot-elastic limit (HEL) along the [111] axis direction is much larger than those along the [100] and [110] axis directions.

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In order to investigate the fundamental properties of energy absorption components, thin-walled circular tubes have been examined as simple example structures. In this study, the effects of the initial wave pattern on the surface of the tubes which will lead the tube to the axis symmetric buckling, were especially investigated by using the FEM code LS-DYNA. To evaluate the effects of the initial wave pattern, we paid attention to the energy absorption per unit volume and the stability of buckling load. From the numerical results, it was found that the stability was obtained by adding wave patterns in the axial direction, although the energy absorption per unit volume decreased with the increase of the stability of buckling load. Furthermore, we introduced the change of the amplitude of wave pattern in the axial direction to improve the energy absorption per unit volume.

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The measurement accuracy in dynamic tension testing is required for the development of design and numerical simulation based on the accurate model of stress-strain relation which is applicable to various strain-rate conditions. The Hopkinson bar method (HBM) is the most widely used one for the dynamic compression test, whereas this method is not used very much for the dynamic tension test. The non-coaxial Hopkinson bar method (NCHBM) is one of the recently proposed dynamic tension tests and is based on HBM. In this study, the accuracy of the stress-strain relation obtained on the basis of NCHBM was discussed by using the FEM code LS-DYNA and by experiment, for SUS316 stainless steel.

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Efficient interatomic potential for PbTiO_3 crystals, which are intensively applied to ferroelectric devices, is required for the atomic-scale study of mechanical and electronic behavior of the materials. In this study, we develop parameters of empirical shell-model potential functions for the equilibrium lattice parameters, elastic constants, Born effective charges and phonon dispersion relations of both cubic and tetragonal PbTiO_3 by fitting to ab initio results using the Newton-Raphson method. The optimized potential for PbTiO_3 reproduces the structures, elastic properties and phonon dispersion relations in good accuracy, whereas Born effective charges are poorly reproduced.

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Plastic bending of (5,5)@(10,10) double-wall carbon nanotube (DWNT) is analyzed using nudged elastic band minimum energy path calculations. At lower applied bending curvature, only the outer tube deforms plastically. But at higher bending curvature, both the inner and outer tubes deform plastically. We find the plastic deformation of the outer tube is more difficult than that of isolated single-wall carbon nanotube (SWNT) of the same diameter, due to tube-tube interactions. In contrast, the plastic deformation of the inner tube is not strongly affected by the presence of the outer tube. We also analyze the shape memory effect (SME) discovered experimentally, which is a thermal recovery process from the plastically bent state to the straight defect-free state, that can be repeated multiple times. We analyze the physics behind SME of carbon nanotubes, which is quite different from that of traditional shape memory alloys.

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By using molecular dynamics method, face-to-face collisions of carbon nanoparticles were simulated for various initial densities, radii and velocities. As the impact velocity increased, the liquidized nanoparticles were decomposed into multiple fragments. The size distributions of the fragments were almost independent of the initial density, radius, and velocity, indicating that most of the fragmentation took place thermally at a certain temperature.

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