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 >

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 >

H.S. Lee¹, W.S. Chu¹, Y.C. Kang¹, H.J. Kang¹, S.H. Ahn²

The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.3, pp. 195-200, 2007, DOI:10.3970/icces.2007.004.195

Abstract The fuel cell is one of promising environment-friendly energy sources for the next generation. The bipolar plate is a major component of the Proton Exchange Membrane (PEM) fuel cell stack, and it takes a large portion of stack volume, weight and cost. In this study, as alternative materials for bipolar plate of PEM fuel cells, graphite composites were fabricated by compression molding and by machining. Graphite particles mixed with epoxy resin were used as the main substance to provide electric conductivity. Flow channels were fabricated by compression molding applying design of experiments (DOE) in order to evaluate moldability. The cost… More >

Song-Jeng Huang¹, Yan-Fu Liu²

The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.3, pp. 187-194, 2007, DOI:10.3970/icces.2007.004.187

Abstract A digital shearographic (DS) technique is a tool well-suited for precision strain measurement and is a nondestructive testing technology. But the fringe patterns of shearography are not so clear. A phase-shifting technique is incorporated into DS and demonstrated to yield fringe patterns with good quality. The major purpose of this study is to produce a measuring system of digital phase-shifting shearography (DPSS) to measure out-of-plan strain of sandwich plate with fully-potted insert. The system mainly includes piezoelectric transducer, servo controller, Michelson shearing mechanism, image processing system and loading system. The Macy algorithm is used for program simulation, and applying noise… More >

S. Nishida¹, N. Hattori¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.3, pp. 179-186, 2007, DOI:10.3970/icces.2007.004.179

Abstract The authors have experimentally confirmed that the non-propagating microcracks are observed in the low carbon plain specimens subjected to the stress of fatigue limit by 1×107 cycles and not observed in those of pure copper and aluminum alloys etc.. In addition, there exists clear fatigue limit in typical austenitic stainless steel SUS304 but not exist the non-propagating micro-cracks subjected to the stress of fatigue limit by 1×107 cycles. On the other hand, there exist not only clear fatigue limit but also non-propagating micro-cracks in the high manganese austenitic steel (HMA 0.20%C steel). Then, the authors have focused to the existence… More >

Iwona Pokorska¹, Andrzej Sluzalec²

The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.3, pp. 171-178, 2007, DOI:10.3970/icces.2007.004.171

Abstract This work has been focused on a unified approach for parameter identification in metal forming processes of poroplastic materials. In order to solve the associated inverse problem a chosen functional is minimized by the use of gradient based methods and a sensitivity analysis. Several numerical and experimental results were presented. These are: the direct problem of simple compression, re-identification of flow stress and identification of loading functions. More >

Sastry Vankamamidi¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.3, pp. 167-170, 2007, DOI:10.3970/icces.2007.004.167

Abstract The behaviour of single free head model flexible batter piles buried in sand and subjected to horizontal loads is investigated. The theoretical estimates of ultimate load, location and magnitude of maximum bending moment for the piles were obtained by considering a vertical rigid pile under inclined load and using semi empirical relations. The length of the equivalent rigid pile was based on the relative stiffness factor of the pile. Model tests were carried out using instrumented flexible piles of wide ranging flexibilities. The piles were buried in loose sand at batter angles of β = ± 30°, ± 15° and… More >

B. Gatmiri¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.3, pp. 159-166, 2007, DOI:10.3970/icces.2007.004.159

Abstract This document summarizes the basic concepts and steps of establishment of the set of equations of wave propoagation in far field and of the dynamic behaviour of porous media in the near field. A breif description of HYBRID software as a powerful tool for evaluation of local seismic site effect is presented. The Combination of the FEM and BEM and improvement of numerical algorithm for the time truncation are described. More >

Jin Yeon Cho¹, Yun Hyuk Choi², You Me Song³, Chang Sik Kim⁴

The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.3, pp. 151-158, 2007, DOI:10.3970/icces.2007.004.151

Abstract In this work, PDSL(pre-detection sort last) and SDSL(strip-wise decomposition sort last) parallel visualization algorithms are proposed for efficient visualization of massive data generated from large-scale parallel finite element analysis through investigating the characteristics of distributed parallel finite element analysis procedure. The proposed parallel visualization algorithms are based on the sort last approach, and designed to be highly compatible with the characteristics of domain-wise computation in parallel finite element analysis. To investigate the performances of proposed algorithms, in-house software is developed by applying the binary tree network communication pattern along with the proposed sorting algorithms, and benchmarking test for parallel visualization… More >

S.H. Lee¹, J.Y. Kim², K.H. Yoon³, K.N. Song⁴

The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.3, pp. 145-150, 2007, DOI:10.3970/icces.2007.004.145

Abstract The nuclear fuel rod support grid is an important structural part of a nuclear fuel assembly used in the pressurized light water reactor. It provides flexible support for the nuclear fuel rods which experience severe thermal expansion and contraction caused by the harsh operational condition in the core. Diverse design requirements should be set on the performances of multidisciplinary nature such as impact resistance, spring characteristics, possible amount of fretting wear on fuel rods, coolant flow and heat transfer around it, and so on. In this paper, an effort is reported to improve the impact resistance of OPT-H type support… More >