A performance optimization based on Computational Fluid Dynamics (CFD) for exhaust hoods of low pressure steam turbine wasconducted A low pressure exhaust hood must be designed promptly m a design process of a steam turbine plant In order to design a low pressure exhaust hood for longer rotor blades rapidly, a database based on conventional CFD analysis results was applied By using this database, the number of CFD analysis for performance designs of low pressure exhaust hoods was reduced Further, validations of these designs were conducted using air test apparatus From these results, the effectiveness of this performance optimization process was confirmed

View full abstract

A semi-intrusive approach to the surrogate modeling in aerodynamic shape optimization problems is presented and its approximating accuracy is analyzed quantitatively The method is semi-intrusive as it uses flow field information m the training of the surrogate models A set of CFD flow field samples obtained with design of experiment are processed through a proper orthogonal decomposition, a decomposition into orthonormal basis of the flow field covariance matrix, which recovers the sample data as the subspace spanned by the orthonomal basis The surrogate model is constructed by establishing a functional relationship between the set of design parameters which generated the sample set and the coefficients of the POD The radial basis function network was used for this purpose The resulting POD-RBFN surrogate model was tested for its approximating accuracy by two validation methods, leave-one-out cross-validation and validation with a fixed set of validating samples The results shows the POD-RBFN approach performs much better than a simple RBFN approach which dmodels the relationship between the design parameters and the scalar objective functions directly

View full abstract

This paper presents a non-parametric shape design methodology of energy absorbing panels under cyclic load with the elastic-plastic behavior The Green-Lagrange strain, the 2nd Piola-Kirchhoff stress and the stiffness tensor are employed to express the elastic-plastic problem involving material and geometric nonlinearity in finite element method The optimal shape of the panel is determined by applying the sensitivity as the fictitious external forces to the design boundaries to change the shape, while maximizing the energy absorption A calculated result is demonstrated to show the effectiveness of the convenient methodology

View full abstract

In this paper, we present a parameter-free free-form optimization method for weight reduction in the strength design of shell structures A volume is minimized under inequality constraints of von Mises stress The optimum design problem is formulated as a distributed-parameter shape optimization problem under the assumptions a shell is varied in the out-of-plane direction to the surface and the thickness is constant The local inequality stress constraints are transformed to an integral equality constraint The shape gradient function and the optimality conditions are derived using the material derivative method, and applied to the free-form optimization method With this method, the smooth optimal free-form of a shell structure is obtained without any shape design parameterization while minimizing the volume and satisfying the stress constraints The validity of this method is verified though a design example

View full abstract

In deep drawing, tearing and wrinkling are major defects In order to avoid these defects, variable blank holder force (VBHF) trajectory should be optimized for successful sheet forming Numerical simulation is so expensive that sequential approximate optimization (SAO) is valid for optimization In particular, the relationship between tearing and wrinkling is conflicting, and multi-objective design optimization is considered in this paper To find VBHF trajectory under conflicting relation, sequential approximate multi-objective optimization (SAMOO) is applied The forming limit diagram (FLD) is used to evaluate tearing and wrinkling Also, the total stroke is divided, and the blank holder force of each sub-stroke step variable is taken as the design variables Numerical result shows that the VBHF trajectory can successfully form the product without tearing and wrinkling

View full abstract

[in Japanese]

View full abstract

In our study, a design system is developed for generating gear trains under design constraints in a specified area The design specifications are input position, output position, input torque, output torque, rotation direction, and so on Spur gear trains are generated by using random method combined with local optimization method The objective function evaluates weight, efficiency and operating life of generated gear train Multi-objective design optimizations in spur gear train generation problems are examined by the gear tram generation system The advantage of the optimization approach to generating effective gear trains is reported through several examples

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

Crack growth under the elastic-plastic fracture is an important issue of the structural integrity, because seismic wave causes low cycle fatigue in the engineering structure We developed automated FEM analysis framework for elastic-plastic crack growth simulation The framework consists of 4 major modules In this work, we employ crack tip opening angle (CTOA) and displacement (CTOD) which are the angle between crack surfaces and the displacement vector to be defined near the crack tip The present work is applied to the cyclic loading analysis of a pipe with a single notch The work shows automated mesh generation capability and fracture mechanics parameters to evaluate crack growth criterion

View full abstract