We developed a hybrid computational method for the design of steam turbine blades. It is composed of three main blocks: the meridian simulation, 3D simulation, and mixing plane blocks. This method was applied to a one-stage medium-pressure turbine and a four-stage low-pressure steam turbine. The results showed that the computation time was approximately half or even less than that of a fully 3D simulation. There was good agreement of the main design parameters, which suggests that our method is useful for the design of turbine blades. By use of this hybrid simulation method, front-loading of the blade design can be achieved and the number of feedbacks in the design process can be reduced. We believe that the proposed method is potentially useful for the simulation-driven design of various industrial products.

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In this paper, a theoretical analysis for predicting the mechanical properties of lattice structures under compressive loading is proposed, and verified by comparing the analytical predictions with FEM results. This theory for estimating E^* is based on the classical beam theory, and the one for estimating σ^*_pl reflects the stress state for each lattice structure. It is found that the BCC structure is a bending-dominated structure, and the BCCZ structure is a compression-dominated structure, and the ƒ₂BCC structure is a mixed loading-dominated (stretching or compression and bending-dominated) structure. Also, the results obtained by this theory agree well with the FEM results.

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The SLSV (single-loop-single-vector) method is modified for the reliability-based optimization problem with multiple reliability constraints. The design problem is formulated to minimize the structural volume of frame structure in terms of cross-sectional area of each frame element subjected to the two mode reliability constraints. The two mode reliability criteria consist of the mean compliance and mean eigenfrequency. The limit state functions are formulated as normalized form to achieve numerical stability of the SLSV method, because the functions are directly adopted as constraint conditions. That is a large difference from the conventional double-loop method, where the limit state functions do not appear in the optimization loop. Through numerical examples of 2-D and 3-D frame design problems, higher computational efficiency and sufficient reliability approximation accuracy by the SLSV method are demonstrated in comparison with the conventional double loop method that the mode reliabilities are evaluated by the first order reliability method (FORM) in each optimization step. Additionally, the importance of normalization of the limit state functions in the SLSV method is also demonstrated.

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The minimum energy motions of pure edge and screw dislocations in aluminum were investigated by atomistic transition state analysis. While the Peierls-Nabarro model and its modifications duplicate the essential nature of a dislocation within a crystalline lattice, the atomic-level relaxation of the dislocation core should be considered to estimate the minimum energy barrier. The relaxed atomic structure within and around the dislocation core is derived from the material’s inherent intrinsic properties and is therefore difficult to solve solely by simple analytical models. In this study, the minimum energy barriers and core structures for the quasi-static motions of pure edge and screw dislocations were investigated by the parallelized nudged elastic band method with the embedded atom method potential. We found that the local potential energy is distributed asymmetrically around the dislocation line for the most stable state and that it is bilaterally symmetrical at the transition state of the dislocation motion. The short-ranged structural relaxation of the core rearrangement as well as the wide-ranging elastic stress field is of great importance in realistic dislocation motion.

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It is well known that the solution of an exterior acoustic problem governed by the Helmholtz equation is violated at the eigenfrequencies of the associated interior problem when the boundary element method (BEM) based on the conventional boundary integral equation (CBIE) is applied without any special treatment to solve it. To tackle this problem, the Burton-Miller formulation using a linear combination of the CBIE and its normal derivative (NDBIE) emerges as an effective and efficient formula which is proved to yield a unique solution for all frequencies if the imaginary part of the coupling constant of the two equations is nonzero. The most difficult part in implementing the Burton-Miller formulation is that the NDBIE is a hypersingular type, and it is often regularized by using the fundamental solution of the Laplace's equation. But various regularization procedures in the literature give rise to integrals which are still difficult and/or extremely time consuming to evaluate in general. However, when constant triangular elements are used to discretize the boundary, all the strongly-singular and hypersingular integrals can be evaluated in finite-part sense explicitly without any difficulty, and the numerical computation becomes more efficient than any other singularity-subtraction technique. Therefore, in this paper, these singular integrals are evaluated rigorously for triangular constant element as finite parts of the divergent integrals by canceling out the divergent terms which appears in the limiting process explicitly. The correctness of the formulation is also demonstrated through some numerical test examples.

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