• Journal of the Korean Geosynthetics Society
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• v.12 no.1
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• pp.11-19
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• 2013

Coarse-grained soils are typical engineering materials commonly used in many civil engineering applications such as structural fills, subgrade and drainage fills for dam, railway and bridge. Various researches have been performed with related to constitutive laws for numerical analysis of such structures. This paper presents a parametric study for a constitutive model for coarse grained materials. The model is a kind of the bounding surface models based on critical state theory. A distinct feature of the model is to capture the response of coarse-grained materials with different void ratios and confining pressures using a single set of model parameters. The model behavior is defined with a set of elastic parameters, critical state parameters, and model-specific parameters. The parametric study was performed for the model-specific parameters. The result of parametric study shows that the model is capable to capture stress-dilatancy behavior and kinematic-hardening under non-associative plastic flow.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.6
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• pp.62-68
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• 2012

Geometry of a screw fabricated by a turning process determined by the shape of the tool, feed rate of the tool and rotation speed of the spindle. Therefore, computing the exact geometry of the screw is very important to perform a simulation on machining or an evaluation of the workpice quality. In this paper, a new mathematical geometry model of the 3 dimensional screw is fabricated by turning process introduced for the exact geometry computation. Becasue model has a parametric formulation, it is easy to process for a CAD geometry or apply for a machining simulation. Also, it can be applied to process planning because it gives precise machined geometry on whole the 3 dimensional surface of the screw. This paper introduces a new parametric model of a geometry for screw fabricated by turning process. As an application, a simulation software for the 3 dimensional screw surface is developed and evaluated for several manufacturing parameters.

• Geomechanics and Engineering
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• v.29 no.3
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• pp.301-310
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• 2022

Accurate prediction of mixed ground conditions ahead of a tunnel face is of vital importance for safe excavation using tunnel boring machines (TBMs). Previous studies have primarily focused on electrical resistivity surveys from the ground surface for geotechnical investigation. In this study, an FE (finite element) numerical model was developed to simulate electrical resistivity surveys for the prediction of risky mixed ground conditions in front of a tunnel face. The proposed FE model is validated by comparing with the apparent electrical resistivity values obtained from the analytical solution corresponding to a vertical fault on the ground surface (i.e., a simplified model). A series of parametric studies was performed with the FE model to analyze the effect of geological and sensor geometric conditions on the electrical resistivity survey. The parametric study revealed that the interface slope between two different ground formations affects the electrical resistivity measurements during TBM excavation. In addition, a large difference in electrical resistivity between two different ground formations represented the dramatic effect of the mixed ground conditions on the electrical resistivity values. The parametric studies of the electrode array showed that the proper selection of the electrode spacing and the location of the electrode array on the tunnel face of TBM is very important. Thus, it is concluded that the developed FE numerical model can successfully predict the presence of a mixed ground zone, which enables optimal management of potential risks.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.13 no.3
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• pp.154-163
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• 2013

In this paper, we propose a formation control algorithm for underactuated autonomous underwater vehicles (AUVs) with parametric uncertainties using the approach angle. The approach angle is used to solve the underactuated problem for AUVs, and the leader-follower strategy is used for the formation control. The proposed controller considers the nonzero off-diagonal terms of the mass matrix of the AUV model and the associated parametric uncertainties. Using the state transformation, the mass matrix, which has nonzero off-diagonal terms, is transformed into a diagonal matrix to simplify designing the control. To deal with the parametric uncertainties of the AUV model, a self-recurrent wavelet neural network is used. The proposed formation controller is designed based on the dynamic surface control technique. Some simulation results are presented to demonstrate the performance of the proposed control method.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.451-458
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• 2002

This paper presents the prediction of deep excavation-induced ground surface movements using artificial neural network, which is of prime importance in the perspective of damage assessment of adjacent buildings. A finite element model, which can realistically replicate deep-excavation-induced ground movements was employed and validated against available large-scale model test results. The validated model was then used to perform a parametric study on deep excavations with emphasis on ground movements. Using the result of the finite element analysis, Artificial Neural Network(ANN) system is formed, which can be used in the prediction of deep exacavation-induced ground surface displacements. The developed ANN system can be effecting used for a first-order prediction of ground movements associated with deep-excavation.

• International conference on construction engineering and project management
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• 2015.10a
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• pp.641-642
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• 2015

Unlike for other building processes, BIM for earthwork does not need a large variety of 3D model shapes; however, it requires a 3D model that can efficiently reflect the changing features of the ground shape and provide soil type-dependent workload calculation and information on equipment for optimal management. Objects for earthwork have not yet been defined because the current BIM system does not provide them. The BIM technology commonly applied in the manufacturing center uses real-object data obtained through 3D scanning to generate 3D parametric solid models. 3D scanning, which is used when there are no existing 3D models, has the advantage of being able to rapidly generate parametric solid models. In this study, A method to generate 3D models for earthwork operations using reverse engineering is suggested. 3D scanning is used to create a point cloud of a construction site and the point cloud data are used to generate a surface model, which was then converted into a parametric model with 3D objects for earthwork

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.299-304
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• 2001

An approach is developed for parametric investigation of the influence of the surface roughness on thermohydrodynamic analysis with film conditions which systemically occur in journal bearings. A parametric investigation is performed for predicting the bearing behaviors such as pressure and temperature distributions in lubricating films between the stationary and moving surfaces determined by absorbed layers and interfaces on the statistical method for rough surface with Gaussian distribution. The layers expressing the effects of surface roughness are expressed as functions of the standard deviations (${\sigma}$) of each surface and surface orientation (j) to explain the flow patterns between both rough surfaces. The coupled effect of surface roughness and shear zone dependency on hydrodynamic pressure and temperature has been found by solving the present model in non-contact mode and contact mode, respectively.

• Transactions of Materials Processing
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• v.13 no.7
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• pp.614-622
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• 2004

A new approach for the automatic elimination of free edges in the finite element model for the analysis of sheet metal forming processes is presented. In general, the raw finite element model constructed from an automatic mesh generator is not well suited for the direct use in the downstream forming analysis due to the many free edges which requires tedious time consuming interactive graphic operations of the users. In the present study, a general method for the automatic elimination of free edges is proposed by introducing a CAD/CAE hybrid method. In the method a trimmed parametric surface is generated to fill the holes which are orginated from the free edges by using the one step elastic finite element analysis. In addition, mesh generation algorithm is suggested which can be used in the general trimmed surface. In order to verify the validity of the proposed method, various examples including actual automobile sheet metal parts are given and discussed.

• Journal of Computational Design and Engineering
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• v.1 no.1
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• pp.27-36
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• 2014

Similar to the essential components of many mechanical systems, the geometrical properties of the teeth of spiral bevel gears greatly influence the kinematic and dynamic behaviors of mechanical systems. Logarithmic spiral bevel gears show a unique advantage in transmission due to their constant spiral angle property. However, a mathematical model suitable for accurate digital modeling, differential geometrical characteristics, and related contact analysis methods for tooth surfaces have not been deeply investigated, since such gears are not convenient in traditional cutting manufacturing in the gear industry. Accurate mathematical modeling of the tooth surface geometry for logarithmic spiral bevel gears is developed in this study, based on the basic gearing kinematics and spherical involute geometry along with the tangent planes geometry; actually, the tooth surface is a parametric surface defined on a parallelogrammic domain. Equivalence proof of the tooth surface geometry is then given in order to greatly simplify the mathematical model. As major factors affecting the lubrication, surface fatigue, contact stress, wear, and manufacturability of gear teeth, the differential geometrical characteristics of the tooth surface are summarized using classical fundamental forms. By using the geometrical properties mentioned, manufacturability (and its limitation in logarithmic spiral bevel gears) is analyzed using precision forging and multiaxis freeform milling, rather than classical cradle-type machine tool based milling or hobbing. Geometry and manufacturability analysis results show that logarithmic spiral gears have many application advantages, but many urgent issues such as contact tooth analysis for precision plastic forming and multiaxis freeform milling also need to be solved in a further study.

• Bulletin of the Korean Space Science Society
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• 2010.04a
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• pp.34.2-34.2
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• 2010

We built 7 potential extra-terrestrial planets including the full 3D Earth model with various surface types and 6 planet models, each with uniform surface characteristics. The surface types include ice, tundra, forest, grass, ground and ocean. We then imported these 7 planets into integrated ray tracing(IRT) model to compute their disk averaged spectra and to understand the spectral behavior depending on the geometrical view, illumination phase and seasonal change. The IRT computation show that the 6 planets with uniform surfaces exhibit clear spectral differences from that of the Earth. We then built a phase and seasonal DAS database for the 6 uniform surface planets and used them for parametric spectral decomposition technique to derive the Earth DAS. This computation resulted in the first potential solution to the surface type ratio of the Earth compared to the measured earth surface type ratio. The computational details and the implications are discussed.