Open Access
ABSTRACT
T. Asada1, N. Ohno1
The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.4, pp. 201-206, 2007, DOI:10.3970/icces.2007.004.201
Abstract In this study, to determine incremental, perturbed displacement fields in periodic inelastic solids, an incremental homogenization problem is fully implicitly formulated, and an algorithm is developed to solve the homogenization problem. It is shown that the homogenization problem can be iteratively solved with quadratic convergences by successively updating strain increments in unit cells, and that the present formulation allows versatility in the initial setting of strain increments in contrast to previous studies. The homogenization algorithm developed is then examined by analyzing a holed plate, with an elastoplastic micro-structure, subjected to tensile loading. It is thus demonstrated that the convergence in… More >
Open Access
ABSTRACT
N. Ohno1, D. Okumura1
The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.4, pp. 207-214, 2007, DOI:10.3970/icces.2007.004.207
Abstract The self energy of geometrically necessary dislocations (GNDs) is considered to inevitably introduce the higher-order stress work-conjugate to slip gradient in single crystals. It is pointed out that this higher-order stress stepwise changes in response to in-plane slip gradient and thus directly influences the onset of initial yielding in polycrystals. The self energy of GNDs is then incorporated into the strain gradient theory of Gurtin (2002). The resulting theory is applied to model crystal grains of size D, leading to a D-1-dependent term with a coefficient determined by grain shape and orientation. It is thus shown that the self energy… More >
Open Access
ABSTRACT
S. Takashima1, N. Miyazaki2, T. Ikeda3, M. Nakagaki4
The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.4, pp. 215-222, 2007, DOI:10.3970/icces.2007.004.215
Abstract Composite materials have complicated microstructures. These structures affect macroscopic deformation. In this study, we focus on the particle size effect in composite materials. For this purpose, we derived an elastic-plastic constitutive equation considering size effect by using Eshelby's theory and the strain gradient theory of plasticity. We performed a homogenized finite element analysis using the elastic-plastic constitutive equation. The results obtained from the analysis show increase of the strength with decrease of the particle size in composite materials. More >
Open Access
ABSTRACT
R. Matsumoto1, N. Miyazaki1, M. Nakagaki2
The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.4, pp. 223-230, 2007, DOI:10.3970/icces.2007.004.223
Abstract The mechanical properties of amorphous metals and metallic glasses are remarkably changed by precipitated crystalline particles. In this paper, the effects of crystal particle size and volume fraction on the flow stress of the metallic glass are evaluated by molecular dynamics simulations. The investigated volume fraction ranges from 0% (metallic glass) to 100% (nanocrystalline metal), and the average particle diameter ranges from 1nm to 12nm. It is revealed that the dispersed particle effects on the flow stress are very small in the entire volume fraction range when the average particle diameter is smaller than 3 nm, and the flow stress… More >
Open Access
ABSTRACT
E.T.R. Dean1
The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.4, pp. 231-242, 2007, DOI:10.3970/icces.2007.004.231
Abstract The shapes of yield envelopes for soils and other materials are generally taken as the starting point of a macroscopic plasticity model. This paper shows that these shapes can be accurately predicted using recent advances in thermodynamics and the new concept of multi-scale patterns. Some implications for future models are discussed. More >
Open Access
ABSTRACT
K. Hashiguchi1 and T. Ozaki2
The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.4, pp. 243-250, 2007, DOI:10.3970/icces.2007.004.243
Abstract The overstress model is improved by incorporating the novel variable "overstress tensor" reaching the current stress from the subloading stress evolving in an imaginary quasi-static process of elastoplastic deformation due to the extended subloading surface model with the tangential inelastic strain rate. More >
Open Access
ABSTRACT
T. Tanaka1
The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.4, pp. 251-256, 2007, DOI:10.3970/icces.2007.004.251
Abstract The viscoplastic constitutive relations with kinematic strain hardening-softening model for geomaterials are developed. The constitutive models include strain-rate dependent properties based on the thoery by Duvaut-Lions. The dynamic relaxation method for static problems and the dynamic analysis for earthquake responses are applied to boundary value problems using finite element methods. More >
Open Access
ABSTRACT
K. Hashiguchi1
The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.4, pp. 257-264, 2007, DOI:10.3970/icces.2007.004.257
Abstract General corotational rate of tensors in arbitrary order having the objectivity is shown first, and then it is verified that the material-derivative of yield condition can be replaced generally to the corotational derivative, i.e. the consistency condition. More >
Open Access
ABSTRACT
Jae-Sang Park1, SangJoon Shin2
The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.4, pp. 265-270, 2007, DOI:10.3970/icces.2007.004.265
Abstract This paper presents the preliminary design effort of a brand new integral twist-actuated blade incorporating single crystal piezoelectric fiber composites. Although the previous integral twist-actuated blade was able to reduce the vibration and acoustic noise of rotorcrafts significantly, a quite high input-voltage was unavoidably required. Therefore, in this paper, it is suggested to develop a new active blade using single crystal piezoelectric composites to reduce the vibration and acoustic noise of helicopters more efficiently. For the preliminary design of a new blade, the characteristics of the sectional properties and the twist actuation frequency responses in hover are investigated in terms… More >
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