• International Journal of CAD/CAM
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• 제7권1호
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• pp.71-80
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• 2007

Recently, feature-based solid modeling systems have been widely used in product design. However, for engineering analysis of a product model, an ed CAD model composed of mid-surfaces is desirable for conditions in which the ed model does not affect analysis result seriously. To meet this requirement, a variety of solid ion methods such as MAT (medial axis transformation) have been proposed to provide an ed CAE model from a solid design model. The algorithm of the MAT approach can be applied to any complicated solid model. However, additional work to trim and extend some parts of the result is required to obtain a practically useful CAE model because the inscribed sphere used in the MAT method generates insufficient surfaces with branches. On the other hand, the mid-surface ion approach supports a practical method for generating a two-dimensional ed model, even though it has difficulties in creating a mid-surface from some complicated parts. In this paper, we propose a dimension reduction approach on solid models based on the midsurface abstraction approach. This approach simplifies the solid model by abbreviating or removing trivial features first such as the fillet, mounting, or protrusion. The geometry of each face is replaced with mid-patches from the simplified model, and then unnecessary topological entities are deleted to generate a clean ed model. Also, additional work, such as extending and stitching mid-patches, completes the generation of a mid-surface model from the patches.

• 대한기계학회논문집B
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• 제28권10호
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• pp.1264-1270
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• 2004

In this paper research on micro solid propellant thruster is reported. Micro solid propellant thruster has four basic components; micro combustion chamber, micro nozzle, solid propellant and micro igniter. In this research igniter, solid propellant and combustion chamber are focused. Micro igniter was fabricated through typical micromachining and the effect of geometry was evaluated. The characteristic of solid propellant was investigated to observe burning characteristic and to obtain burning velocity. Change of thrust force and the amount of energy loss following scale down at micro combustion chamber were estimated by numerical simulation based on empirical data and through the calculation normalized specific impulses were compared to figure out the efficiency of combustion chamber.

• 한국CDE학회논문집
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• 제12권2호
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• pp.101-108
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• 2007

As 3D solid modeling has been widely used in designing products, solid models of the products are directly used in various applications such as engineering analysis and process planing. However, the fully-detailed solid models may not be necessary in some application. For example, it is often more efficient to use simplified model of part of engineering analysis. Generation of mesh for the complex original model requires a quite amount of time, and the consequence of finite element analysis may not be desirable due to small and detailed geometry in the model. In this paper, a method to simplify solid models of machined part is presented. This method decomposes the delta volume of machined part, and uses the decomposed volumes to simplify the solid model. Since this method directly recognizes the features to be removed from the final model, it is independent of not only design features of specific CAD system, but also designer's design practice of design sequences.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제20회 춘계학술대회 논문집
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• pp.147-150
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• 2003

The purpose of this research was to develope components of micro solid propellant thruster. Micro solid propellant thruster had four basic components: combustion chamber, nozzle, solid propellant and micro heater for ignition. A performance of micro heater and characteristic of solid propellant was investigated. Micro heater was fabricated by conventional MEMS process and Platinum layer was used for heating element. Effect of geometry parameters on micro heater was tested. The temperature responses of heater with respect to each parameters was compared for a given electrical power. The characteristic of solid propellant(HTPB/AP) was investigated to obtain burning velocity in small chamber. Additionally, a capacity of filling propellant with high viscosity in small chamber was checked to guarantee for the micro fabrication.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.275-282
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• 2008

This paper presents numerical investigation of multi-phase flow in solid rocket motor nozzle and effect of multi-phases on the performance prediction of the Solid Rocket Motor. Aluminized propellants are frequently used in solid rocket motors to increase specific impulse. An Eulerian-Lagrangian description has been used to analyze the motion of the micrometer sized and discrete phase that consist of the larger particulates present in the Solid Rocket Motor. Uniform particles diameters and Rosin-Rammler diameter distribution method has been used for the simulation of different burning of aluminum droplets generating aluminum oxide smokes. Roe-FDS scheme has been used to simulate the effects of the multi-phase flow. The results obtained show the sensitivity of this distribution to the nozzle flow dynamics, primarily at the nozzle inlet and exit. The analysis also provides effect of two phases on performance prediction of Solid Rocket Motor.

• Interaction and multiscale mechanics
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• 제2권1호
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• pp.45-68
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• 2009

An aim of the study is to develop an efficient numerical simulation technique that can handle the two-scale analysis of fluid permeation filters fabricated by the partial sintering technique of small spherical ceramics. A solid-fluid mixture homogenization method is introduced to predict the mechanical characters such as rigidity and permeability of the porous ceramic filters from the micro-scale geometry and configuration of partially-sintered particles. An extended finite element (X-FE) discretization technique based on the enriched interpolations of respective characteristic functions at fluid-solid interfaces is proposed for the non-interface-fitted mesh solution of the micro-scale analysis that needs non-slip condition at the interface between solid and fluid phases of the unit cell. The homogenization and localization performances of the proposed method are shown in a typical two-dimensional benchmark problem whose model has a hole in center. Three-dimensional applications to the body-centered cubic (BCC) and face-centered cubic (FCC) unit cell models are also shown in the paper. The 3D application is prepared toward the computer-aided optimal design of ceramic filters. The accuracy and stability of the X-FEM based method are comparable to those of the standard interface-fitted FEM, and are superior to those of the voxel type FEM that is often used in such complex micro geometry cases.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1093-1097
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• 2004

We propose 'the haptic primitive' for haptic rendering without the need to solve complicated parametric equations. To develop 'the haptic primitive', we adopted "the God-Object Method" as a haptic rendering algorithm and applied 'Constructive Solid Geometry' to manage haptic objects. Besides being used in the 'ghost library' of $PHANToMTM^{TM}$ our method can be used as a basic component for developing tools and libraries that aim to simplify haptic modeling. It can also be applied to tactile display modules and temporal display modules. Ultimately it can be developed into a one-stop haptic modeling tool that enables the user to more conveniently create a tangible CAD systems or a tangible e-ommerce system.

• 한국지능시스템학회논문지
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• 제12권3호
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• pp.255-260
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• 2002

This paper describes a fuzzy-based system for analyzing the stress intensity factors (SIFs) of three-dimensional (3D) cracks. A geometry model, i.e. a solid containing one or several 3D cracks is defined. Several distributions of local node density are chosen, and then automatically superposed on one another over the geometry model by using the fuzzy knowledge processing. Nodes are generated by the bucketing method, and ten-coded quadratic tetrahedral solid elements are generated by the Delaunay triangulation techniques. The singular elements such that the mid-point nodes near crack front are shifted at the quarter-points, and these are automatically placed along the 3D crack front. The complete finite element(FE) model is generated, and a stress analysis is performed. The SIFs are calculated using the displacement extrapolation method. To demonstrate practical performances of the present system, semi-elliptical surface cracks in a inhomogeneous plate subjected to uniform tension are solved.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1993년도 추계학술대회 논문집
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• pp.200-205
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• 1993

The automatic forming sequence design system can determine desirable operation sequences even if they have little experience in the design of cold forging process. This system is proposed,which generates forming sequence plans for the multistage cold forging of zxisymmetrical solid products. Since the process of metal forming can be considered as a transformation of geometry, treatment of the geometry of the product is a key in planning processes. Forming sequence for the part can be determined by means of primitive geometries such as cylinder,cone, convex, and concave. By utilizing this geometrical characteristics(diameter,height, and radius),the product geometry is expressed by a list of the pnmitive geometries. Accordingly, the forming sequence design is formulated as the search problem which starts with a billet geometry and finishes with a given product one. Using the developed system, the sequence drawing with all dimensions, which includes the proper sequence of operations for the part, is generated under the environment of AutoCAD. The preliminary choice of some feasible forming sequences can verify by using the finite element simulation.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.237-240
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• 2004

Indexable end mills, which consist of inserts and cutter body, have been widely used in roughing of parts in the mold industry. The geometry and distribution of inserts on cutter body are determined by application. This paper proposes analytical cutting force model for indexable flat end-milling process. Developed cutting force model uses the cutting-condition-independent cutting force coefficients and considers runout, cutter deflection and size effect for the accurate cutting force prediction. Unlike solid type endmill, the tool geometry of indexable endmill is variable according to the axial position due to the geometry and distribution of inserts on the cutter body. Thus, adaptive algorithm that calculates tool geometry data at arbitrary axial position was developed. Then number of flute, angular position of flute, and uncutchip thickness are calculated. Finally, presented model was validated through some experiments with aluminum workpiece.