• Journal of Magnetics
• /
• v.20 no.4
• /
• pp.387-393
• /
• 2015

Torque ripple is necessarily generated in interior permanent magnet synchronous motors (IPMSMs) due to the non-sinusoidal distribution of flux density in the air gap and the magnetic reluctance by stator slots. This paper deals with an asymmetric rotor shape to reduce torque ripple which can make sinusoidal flux density distribution in the air gap. Meanwhile the average torque is relatively increased by the asymmetric rotor. Response surface method (RSM) is applied to find the optimum position of the permanent magnets for the IMPSM with improved torque performance. Consequently, an asymmetric structure is the result of RSM and the structure has disadvantage of a mechanical stiffness. Finally, the performance of suggested shape is verified by finite element analysis and structural analysis is conducted for the mechanical stiffness.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1999.03b
• /
• pp.45-48
• /
• 1999

A program for initial blank design in sheet forming which contains the capabilities of forward loading simulation by the finite element method and backward tracking simulation has been developed and proved the effectiveness by applying to a square cup stamping process. In the blank design of square cup stamping the backward tracing program can produce an optimum blank configuration which forms a sound net-shape cup produce without machining after forming. Another general application appears in the blank design of a cup stamping with protruding flanges one of typical automobile components. The blank configurations derived by backward tracing simulation have been confirmed by a series of loading simulations. The approach for decision of an initial blank configuration presented in this study will be a milestone in fields of sheet forming process design.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2000.04a
• /
• pp.21-25
• /
• 2000

An inverse finite element approach is employed for more capability to design the optimum blank shape from the desired final shape with small amount of expense and computation time For multi-stage sheet metal forming processes numerical analysis is expense difficult to carry out the to its complexities and convergence problem. It also requires lots of computation time. For the analysis of elliptic cup with large aspect ratio intermediate sliding constraint surfaces are difficult to describe. in this paper multi-stage finite element inverse analysis is applied to multi-stage elliptic cup drawing processes to calculate intermediate blank shapes and strain distributions in each stages. To describe intermediate sliding constraint surfaces an analytic scheme is introduced to deal with merged-arc type sliding surfaces.

• Journal of the Korean Society of Safety
• /
• v.21 no.6 s.78
• /
• pp.82-87
• /
• 2006

The existing raised pavement marker, however, have some limitations. Most of them are square-shaped which makes only forward and backward retro-reflection, their orientation can be easily changed by impact of vehicle, and the surface reflector can be readily contaminated leading poor functioning. In addition, maintenance for broken raised pavement marker is not easy. The purpose of the study is to design and manufacture a new and improved type of raised pavement marker. The new raised pavement marker has round-shaped upper structure. Its body was separated from the holder and the reflector was surrounded by acrylic cover. We tested performances of the constituent parts, optimum load after installation, and reflection efficiency. The new raised pavement marker will be an initiation of studies on the improvement of the shape and performance of raised pavement markers.

• Journal of computational fluids engineering
• /
• v.11 no.1 s.32
• /
• pp.21-28
• /
• 2006

Reliability Based Design Optimization(RBDO) is one of the optimization methods that minimize the product failure due to small changes of operating conditions or process errors. It searches the optimum that satisfies the safety margin of each constraint, and it gives stable and reliable designs. However, RBDO requires many times oj computational efforts compared with the conventional deterministic optimization(DO) to evaluate the probability of failure about each constraint, therefore it is hard to apply directly to large-scaled problems such as a flexible wing shape design optimization. For the efficient reliability analysis, the approximate reliability analysis method with the two-point approximation(TPA) is proposed In this study, the lift-to-drag ratio maximization designs are performed with 3-dimensional Navier-Stokes analysis and NASTRAN structural analysis, and the optimization results about the deterministic, FORM and SORM are compared.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.7 no.4
• /
• pp.135-141
• /
• 2008

Independent suspension axle and final reduction gear for special-purpose vehicles such as a armored vehicles are almost imported in Germany etc. so, developing them is necessary to save cost. In severe condition (open fields, water surface driving, obstacle pass), special-purpose vehicles must work well. Drop box, axle and final reduction gear performed static analysis. We know that is possible weight reduction. The purpose of this paper is to find out the optimal shape of final reduction gear's case by means of response surface methodology. The response surface method is the statistical method which can be applied to the non-sensitivity based optimization. The response surface which is constructed by the least square method contains only the polynomial terms so that the global maximum and minimum points are easily obtained.

• Proceedings of the KSME Conference
• /
• 2001.06a
• /
• pp.752-757
• /
• 2001

To reduce stress concentration around the intersection between a spherical pressure vessel and a cylindrical nozzle under various load conditions using less material, the optimization for the distribution of reinforcement has researched. The ranked bidirectional evolutionary structural optimization(R-BESO) method is developed recently, which adds elements based on a rank, and the performance indicator which can estimate a fully stressed model. The R-BESO method can obtain the optimum design using less iteration number than iteration number of the BESO. In this paper, the optimized intersection shape is sought using R-BESO method for a flush and a protruding nozzle. The considered load cases are a radial compression, torque and shear force.

• Proceedings of the KSME Conference
• /
• 2000.04b
• /
• pp.721-727
• /
• 2000

Impedance method was carried out to design the electrode that can measure the void fraction of the bubbly flow in pool reservoir. To find out the optimum electrode shape, Styrofoam-tests were performed in a specially designed acrylic reservoir. Three kinds of electrodes were designed to compare the characteristics of water-air flow. The resistance was increased as the void fraction increased and the capacitance was decreased as the void fraction increased. The resistance is a main parameter to express the nature of the water-air flow in impedance method. Almost all the values of impedance were involved in resistance. The degree of deviation from the mean-resistance values showed reasonable results. Electrode type-I expressed excellent results among the three electrode shapes. The impedance values in void fraction 0-10% were similar to those of Maxwell's equation. But the impedance values in void fraction 10-20% were not similar to those of Maxwell' equation because of the edge effect near electrode.

• Proceedings of the KSME Conference
• /
• 2003.11a
• /
• pp.735-740
• /
• 2003

In this study, a numerical optimization to find the optimal shape of streamwise periodic ribs mounted on both of the principal walls is performed to enhance turbulent heat transfer in a rectangular channel. The optimization is based on Navier-Stokes analysis of flow and heat transfer with $k-{\varepsilon}$ turbulence model and is implemented using response surface method. The width-to-height ratio of a rib, rib height-to-channel height ratio, rib pitch to rib height ratio and distance between opposite ribs to rib height ratio are chosen as design variables. The object function is defined as a function of heat transfer coefficient and friction drag coefficient with weighting factor. Optimum shapes of the rib have been investigated for the range of 0.0 to 0.1 of weighting factor.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.50 no.11
• /
• pp.539-545
• /
• 2001

A simple analysis method for inverter-fed induction motor using F.E.M and harmonic equivalent circuit is proposed. And an optimum shape of rotor slot for 2Hp inverter-fed induction motor is determined by combining the proposed analysis method and an optimization algorithm. Conjugate gradient method is used for the optimization algorithm. The optimization is performed for higher efficiency and reduction of harmonic loss in the inverter-fed induction motor. The optimization results are verified by comparing with those of the time-step F.E.A.