• Composites Research
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• v.33 no.6
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• pp.353-359
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• 2020

In this work, a contour-based section analysis method incorporating the use of Bézier curves is attempted for the construction of optimal structural design framework of composite helicopter blades. The suggested section analysis method is able to analyze composite blades with solid cores made of arbitrary materials and geometric shapes. The contour-based section analysis method is integrated into a blade structural optimization framework to confirm the efficiency of the present approach. The numerical simulation result demonstrates that the optimized blade configurations are obtained with a reduction in mass by 52%, compared to the baseline blade. For the structural optimization of composite blades with 19 subsections, it takes about one hour for the successful optimization while satisfying all the design constraints considered in this study, which reveals the efficiency of the present approach.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.1
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• pp.132-138
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• 2011

A micromachined silicon accelerometer capable of surviving and detecting very high accelerations(up to 200,000 times the gravitational acceleration) is necessary for a high impact accelerometer for earth-penetration weapons applications. We adopted as a reference model a piezoresistive type silicon micromachined high-shock accelerometer with a bonded hinge structure and performed structural analyses such as stress, modal, and transient dynamic responses and sensor sensitivity simulation for the selected device using piezoresistive-structural coupled-field analysis. In addition, structural optimization was introduced to improve the performances of the accelerometer against the initial design of the reference model. The design objective here was to maximize the sensor sensitivity subject to a set of design constraints on the impact endurance of the structure, dynamic characteristics, the fundamental frequency and the transverse sensitivities by changing the dimensions of the width, sensing beams, and hinges which have significant effects on the performances. Through the optimization, we could increase the sensor sensitivity by more than 70% from the initial value of $0.267{\mu}V/G$ satisfying all the imposed design constraints. The suggested simulation and optimization have been proved very successful to design high impact microaccelerometers and therefore can be easily applied to develop and improve other piezoresistive type sensors and actuators.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.04a
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• pp.154-161
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• 2001

A procedure of the design optimization for steel box girder bridges using micro genetic algorithms(μGA) is developed. The effect of population size is investigated and the efficiency and reliability of μGA is demonstrated in the optimum design of steel box girder bridges. Optimum design problems of steel box girder bridges are formulated, where tile design of concrete slab is based on the USD specifications and steel box girder based on LRFD respectively. Design of optimizations of single-span and 2-span steel box girder bridges are performed with the population size of 5, 40, 80, and 120, respectively The μGA-based optimum design of the 3-span steel box girder bridge is compared with SQP results.

• Structural Engineering and Mechanics
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• v.86 no.2
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• pp.197-209
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• 2023

In the case of designing control devices in a building, reliance on experimental formulation or engineering concepts without using optimization algorithms leads to non-optimal solutions or design parameters, which makes the use of control devices costly and unreasonable. The optimization algorithms are capable of identifying the required number of parameters for a specific design problem, however, this process is difficult and inefficient in dealing with some specific optimal design processes. This paper aims to introduce an upgraded version of the salp swarm algorithm to handle some engineering design. The performance of the new upgraded algorithm is tested using some benchmark test functions as well as a six-story benchmark building equipped with semi-active MR dampers. The simulation results show that the proposed algorithm can be successfully applied to get an optimal design of the MR dampers in the building.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.1
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• pp.71-78
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• 2014

Door hinges of large refrigerators are required to ensure that the doors open and close smoothly in addition to supporting door weights and enduring the impact loads due to door opening and closing. However, door hinge design is difficult because of complex hinge mechanisms and sensitive structural safety. In this study, the mechanism satisfying the required spring response, space constraints, and structural strength is optimized, and the volume of the outer frame covering the hinge mechanism is minimized for reducing production costs. The entire design process is automated using the PIDO(Progress Integration and Design Optimization) technique, which achieves an efficient design process. Therefore, the frame mass is reduced to 24%, and the mechanism performance and structural stability are improved.

• Journal of the Korean Society of Safety
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• v.27 no.5
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• pp.148-157
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• 2012

Reliability-based design optimization (RBDO) problem is usually formulated as an optimization problem to minimize an objective function subjected to probabilistic constraint functions which may include deterministic design variables as well as random variables. The challenging task is that, because the probability models of the random variables are often assumed based on limited data, there exists a possibility of selecting inappropriate distribution models and/or model parameters for the random variables, which can often lead to disastrous consequences. In order to select the most appropriate distribution model from the limited observation data as well as model parameters, this study takes into account a set of possible candidate models for the random variables. The suitability of each model is then investigated by employing performance and risk functions. In this regard, this study enables structural design optimization and fitness assessment of the distribution models of the random variables at the same time. As the first paper of a two-part series, this paper describes a new design method considering probability model uncertainties. The robust performance of the proposed method is presented in Part 2. To demonstrate the effectiveness of the proposed method, an example of ten-bar truss structure is considered. The numerical results show that the proposed method can provide the optimal design variables while guaranteeing the most desirable distribution models for the random variables even in case the limited data are only available.

• The KSFM Journal of Fluid Machinery
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• v.2 no.4 s.5
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• pp.31-39
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• 1999

Using basic shape and aerodynamic data for the designed impeller, basic structure analysis such as stress analysis and eigenvalue analysis was carried out. Also, we made the optimization program that was designed for optimum thickness within the adaptive stress limits. For the structural optimum theory, we used the BFGS(Broydon Fletcher Goldfarb Shanno) Method which is one of the searching methods. Through this program we managed optimization of the blade. For numerical simulation, we used the optimization program to compose Cyclic Module of NASTRAN and the Optimization Program which was implemented by C and fortran language.

• Structural Engineering and Mechanics
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• v.55 no.6
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• pp.1157-1176
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• 2015

This study presents optimizing structural topology patterns using regularization of Heaviside function. The present method needs not filtering process to typical SIMP method. Using the penalty formulation of the SIMP approach, a topology optimization problem is formulated in co-operation, i.e., couple-signals, with design variable values of discrete elements and a regularized Heaviside step function. The regularization of discontinuous material distributions is a key scheme in order to improve the numerical problems of material topology optimization with 0 (void)-1 (solid) solutions. The weak forms of an equilibrium equation are expressed using a coupled regularized Heaviside function to evaluate sensitivity analysis. Numerical results show that the incorporation of the regularized Heaviside function and the SIMP leads to convergent solutions. This method is tested using several examples of a linear elastostatic structure. It demonstrates that improved optimal solutions can be obtained without the additional use of sensitivity filtering to improve the discontinuous 0-1 solutions, which have generally been used in material topology optimization problems.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.8
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• pp.1920-1929
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• 1994

The stochastic finite element method(SFEM) based structural optimal design is presented. Random system response including uncertainties for the design variable is calculated with first order perturbation method. A method for calculating the sensitivity coefficients is developed using the equilibrium equation and first-order perturbed equation. Numerical results are presented for a truss, frame and plate structures with displacement and stress constraints. The sensitivity calculation proposed here is compared with finite difference method. A nonlinear programming technique is used to solve the problem. The procedure is easily incorporated with existing deterministic structural optimization.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.2
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• pp.86-93
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• 2010

The tilting index table has attached to CNC machining center with 3axes, it can be improvement of its performance and its machining efficiency. The tilting index table is a key unit in order to manufacture some non-rotational and 3-dimensional parts, using the conventional machining center. In this study, structural analysis is carried out by FEM simulation using the commercial software ANSYS Workbench 11 to develop tilting index table using direct drive motor. The shape of the tilting index table obtained from the optimization was analyzed and compared with the initial model. Also, the initial model was modified based on the optimization model and the result was verified to have the acceptable improvement.