FunctionBay Inc.

Seongnam, South Korea

FunctionBay Inc.

Seongnam, South Korea
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Patent
FunctionBay Inc. | Date: 2016-08-21

Provided is a modeling method including: executing a modeling program; performing a first modeling based on a plurality of entities by using the modeling program, wherein a first entity among the plurality of entities comprises a first parameter and a first value corresponding to the first parameter; parsing a header value, a parameter value, and a modification value corresponding to each field from a data table comprising a header field, a parameter field, and a modification field; modifying the first value of the first entity based on the extracted header value, parameter value, and modification value; and performing a second modeling based on the modified first entity.


Kim S.,FunctionBay Inc. | Choi J.,FunctionBay Inc. | Rhim S.,Kyung Hee University | Choi J.H.,Kyung Hee University
Key Engineering Materials | Year: 2017

An analysis for operating characteristics of piston lubrication system is performed based on the numerical model in this study. Dynamic piston lubrication characteristics such as oil film pressure and thickness distribution can be analyzed through a numerical model with an integration of elastohydrodynamics and multi-flexible-body dynamics (MFBD). In particular, the oil film thickness variation by elastic deformation is considered in the elastohydrodynamic analysis by using the modal reduction method in MFBD system. And this effect is reflected on the fluid governing equations to evaluate the oil film pressure in the lubrication region. A series of process proposed in this study is available for the analysis of realistic elastohydrodynamic lubrication phenomenon. A numerical example for the piston lubrication system is also demonstrated. © 2017 Trans Tech Publications, Switzerland.


Choi J.,FunctionBay Inc. | Kim S.S.,Seoul National University | Choi J.H.,Kyung Hee University
5th Asian Conference on Multibody Dynamics 2010, ACMD 2010 | Year: 2014

This study deals with the modeling and analysis method for the elastohydrodynamic lubrication system such as journal bearing coupled with flexible multibody dynamics (or Multi-Flexible-Body Dynamics, MFBD) in order to analyze dynamic bearing lubrication characteristics such as pressure distribution and oil film thickness. In order to solve coupled fluid-structure interaction system, this study uses two main parts. The one is the MFBD solver and the other is elastohydrodynamic module. The elastohydrodynamic lubrication module developed in this study transmits the force and torque data to the MFBD solver which can solve general dynamic systems that include lots of rigid and flexible bodies, joints, forces, and contact elements. And then, the MFBD solver analyses the position, velocity, and accelerations of the flexible multibody system with the pressure distribution results of the elastohydrodynamic module. And the MFBD solver transmits the position and velocity information to the elastohydrodynamic solver continuously. Moreover, other functions such as mesh grid control and oil hole and groove effects are implemented. Finally, numerical examples for bearing lubrication systems are demonstrated. Copyright (c) 2010 by JSME.


Choi J.,Seoul National University | Ryu H.S.,FunctionBay Inc. | Kim C.W.,Konkuk University | Choi J.H.,Kyung Hee University
Multibody System Dynamics | Year: 2010

Dynamic analysis of many mechanical systems often involves contacts among rigid bodies. When calculating the contact force with a compliant contact force model, a penetration depth and a contact reference frame (a contact point and normal and tangent directions) should be determined from the geometrical information of the rigid body surfaces. In order to improve the speed and robustness of the contact analysis, this paper proposes a contact search algorithm for surfaces composed of triangles. This algorithm is divided into two parts, the pre-search and the detailed search. In the pre-search, a bounding box tree and an overlap test are used to find intersecting triangle pairs, and triangle connectivity information is used to identify and separate multiple contact regions. Then an efficient and robust detailed search algorithm is proposed, where the penetration depth and contact reference frame are determined from the results of the pre-search. Finally, the contact force for each contact region is calculated from a modified compliant contact force model. Numerical examples are also presented to illustrate the accuracy and performance. © 2009 Springer Science+Business Media B.V.


Choi J.,FunctionBay Inc. | Kim S.S.,Seoul National University | Rhim S.S.,Kyung Hee University | Choi J.H.,Kyung Hee University
International Journal of Automotive Technology | Year: 2012

This study uses an elastohydrodynamic lubrication model coupled with multi-flexible-body dynamics (MFBD) to analyze dynamic bearing lubrication characteristics, such as pressure distribution and oil film thickness. To solve the coupled fluid-structure interaction system, this study uses an MFBD solver and an elastohydrodynamics module. The elastohydrodynamics module passes its force and torque data to the MFBD solver, which can solve general dynamic systems that include rigid and flexible bodies, joints, forces, and contact elements. The MFBD solver analyzes the positions, velocities, and accelerations of the multi-flexible-body system while incorporating the pressure distribution results of the elastohydrodynamics module. The MFBD solver then passes the position and velocity information back to the elastohydrodynamics solver, which reanalyzes the force, torque, and pressure distribution. This iteration is continued throughout the analysis time period. Other functions, such as mesh grid control and oil hole and groove effects, are also implemented. Numerical examples for bearing lubrication systems are demonstrated. © 2012 The Korean Society of Automotive Engineers and Springer-Verlag Berlin Heidelberg.


Choi J.,FunctionBay Inc. | Choi J.H.,Kyung Hee University
Proceedings of the ASME Design Engineering Technical Conference | Year: 2013

The contact analysis of multi-flexible-body dynamics (MFBD) has been an important issue in the area of computational dynamics because the realistic dynamic analysis of many mechanical systems includes the contacts among rigid and flexible bodies. But, until now, the contact analysis in the multi-flexible-body dynamics has still remained as a big, challenging area. Especially, the most of contact algorithms have been developed based on the facetted triangles. As a result, the contact force based on the facetted surface was not accurate and smooth because the geometrical error is already included in the contact surface representation stage. This kind of error can be very important in the precise mechanism such as gear contact or cam-valve contact problems. In order to resolve this problem, this study suggests a cubic spline surface representation method and related contact algorithms. The proposed contact algorithms are using the compliant contact force model based on the Hertzian contact theory. In order to evaluate the smooth contact force, the penetration depth and contact normal directions are evaluated by using the cubic spline surface interpolation. Also, for the robust and efficient contact algorithm development, the contact algorithms are divided into four main parts which are a surface representation, a pre-search, a detailed search and a contact force generation. In the surface representation part, we propose a smooth surface representation method which can be used for smooth rigid and flexible bodies. In the pre-search, the algorithm performs collision detection and composes the expected contact pairs for the detailed search. In the detailed search, the penetration depth and contact reference frame are calculated with the cubic spline surface interpolation in order to generate the accurate and smooth contact force. Finally in the contact force generation part, we evaluate the contact force and Jacobian matrix for the implicit time integrator. Copyright © 2013 by ASME.


Sanborn G.G.,FunctionBay Inc. | Choi J.,FunctionBay Inc. | Choi J.H.,Kyung Hee University
Multibody System Dynamics | Year: 2011

The Absolute Nodal Coordinate Formulation (ANCF) is a relatively new nonlinear finite element type that uses Hermite splines for shape functions. In this investigation, the ANCF is examined as a possible tool for use in modeling the media in flexible media transport systems, such as printers, copy machines, and roll-to-roll systems. However, it is demonstrated using an example of a thin plate-type ANCF finite element that these elements can suffer from significant membrane locking, which can be problematic for paper or paper-like media. One source of this locking is identified to be a property of all parametric curves that are composed of polynomials. The property is that for parametric polynomial curves, changes in the state of curvature of the curve cause changes in the distribution of points along the curve. This property is labeled Curve-Induced Distortion (CID) by the authors of this paper. CID can cause axial and membrane strain distortion in elements, causing them to be overly stiff. A new solution method is proposed to directly counteract CID in finite elements that use cubic Hermite curves for shape functions, specifically for modeling problems in which bending occurs primarily around one axis, such as paper in printing and media transport machinery. This method is labeled Flat-Mapped Extension Modeling (FMEM). FMEM is a mixed field method that uses a 1D Hermite polynomial kinematically linked to the 3D Hermite curve to represent the axial displacement field. FMEM significantly reduces the effect of CID in the ANCF element tested here. This investigation demonstrates using a single ANCF plate element type that the ANCF's accuracy can be significantly improved by FMEM with only a small increase in computational cost. It is shown with this plate-element example that without correcting CID, the ANCF element tested is computationally much slower than contemporary methods like the co-rotational formulation for similar accuracy. But with FMEM, the ANCF is significantly faster than the co-rotational formulation for similar accuracy. © 2011 Springer Science+Business Media B.V.


Cha H.-Y.,FunctionBay Inc. | Choi J.,FunctionBay Inc. | Ryu H.S.,FunctionBay Inc. | Choi J.H.,Kyung Hee University
Journal of Mechanical Science and Technology | Year: 2011

Contact force of Multi-body dynamics (MBD) system can be classified two parts. First is a normal force and the other is a tangential force called friction force. And the friction force can be represented by two states such as stick and slip. The stick-slip phenomenon is simply described as a simple contact model which is a rigid body contacted on a sloped surface. If the calculated friction coefficient between the body and sloped surface is less than the static friction coefficient, the body should be stuck. If the calculated friction coefficient is greater than the static friction coefficient, the body will be sliding along the surface. The phenomenon is called as stick and slip state of friction, respectively. Usually many researchers and commercial MBD software used a coulomb friction force model which is defined with an only function of relative velocity. This kind of friction force model will be called a conventional friction force model in this paper. A big problem of the conventional model can not describe a stick state of friction phenomenon. In the case of conventional friction force model, the body will be sliding even though friction state is stick. Because, the relative velocity must have a non-zero value in order to generate the friction force. To solve this kind of problem, we propose a stick-slip friction force model including a spring like force. In the case of stick-slip friction force model, the body can be stuck on the sloped surface because the friction force will be a non-zero value, even though the relative velocity approaches zero. We defined a relative displacement variable called stiction deformation. In this paper, the stick-slip friction model is proposed and applied in the contact algorithm of MBD system. And then two friction models are compared with numerical examples. With the proposed stick-slip friction model, more realistic results are achieved. © 2011 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.


Choi J.,FunctionBay Inc. | Rhim S.,Kyung Hee University | Choi J.H.,Kyung Hee University
International Journal of Non-Linear Mechanics | Year: 2013

The analysis of multi-flexible-body dynamics (MFBD) has been an important issue in the area of computational dynamics. Also, dynamic analysis of many mechanical systems often involves contacts among rigid and flexible bodies. But, until now, the contact analysis in the multi-flexible-body dynamics has still remains a big, challenging area. In order to simulate the contact phenomena, this study uses a compliant contact force model based on the Hertzian contact theory. When generating the contact force with a compliant contact force model, a penetration depth and a contact reference frame (a contact point and normal and tangent directions) must be determined from the geometrical information of the rigid and flexible body surfaces. For robust and efficient general purpose contact algorithms, the contact algorithms are divided into four main parts which are a surface representation, a pre-search, and a detailed search and a contact force generation. In the surface representation part, we propose a general surface representation method which can be used for complex rigid and flexible bodies. In the pre-search, the algorithm performs collision detection and composes the input data sets for the detailed search. Then, in the detailed search, the penetration depth and contact reference frame are calculated in order to generate the contact force by using the compliant contact force model. Finally, in the contact force generation part, we evaluate the contact force and the Jacobian matrix which can be used for the implicit integrator. The new general purpose contact algorithm is called GGEOM (General GEOMetry) contact, because it can use general rigid and flexible geometries. © 2013 Elsevier Ltd. All rights reserved.


Zhu X.,Pusan National University | Zhu X.,FunctionBay Inc. | Yoo W.S.,Pusan National University
Nonlinear Dynamics | Year: 2016

The dynamics of marine cables are efficiently expressed using the lumped-mass model, which divides the cable into finite elements, on each of which a reference frame is fixed in order to convert loads acting on the element. This paper proposes a new element reference frame that is formulated by the vectors of the element orientation and relative velocity of the fluid. This frame satisfactorily addresses situations wherein singularities are generated by the Frenet frame and Euler angles. Additionally, it expresses the hydrodynamic drag force in a concise formulation. The advantages of the proposed frame are demonstrated by comparing the established cable modeling with that established by the Frenet frame and Euler angles in several examples. Simulation results reveal that the proposed frame is more suitable for dynamic analysis of marine cables compared with the Frenet frame and Euler angles. © 2016 Springer Science+Business Media Dordrecht

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