• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.1
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• pp.92-97
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• 2007

This study was carried out to minimize the lifting force and to design the slim sized frame of a height adjustment mechanism. This unit is designed for the display devices in order to enhance the ergonomics for effective height adjustment as well as to achieve much slimmer frame for the pedestal. A tolerance analysis of 6 sigma was applied to achieve smooth lift at design stage not to change the tolerance specification of gap several times in a roller type of lifting mechanism at mass production stage. The specification of minimum gap and the target of production yield ratio were agreed with a quality team before tooling. A DFSS simulation on drawings had been done with reasonable tolerance and achievable standard deviation(${\sigma}$) several times until the target specification of gap and yield ratio was met. Once tolerance and deviation(${\sigma}$) were fixed tooling start was done successfully. A CAE method was applied to achieve a slim design. Design parameters were frozen when those parameters matched the reference strength data of standard model. Through those tolerance analysis and CAE simulation the number of tool modification was reduced and production yield ratio was raised up without arguing quality specification at production stage in the end.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.714-719
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• 2000

In this paper, an application program is made to simulate the behavior of a ship block under various crane works and to generate data of lu9 reactions and wire tensions. The program is based on a CAD program, Pro/ENGINEER. A ship is composed of more than 100 ship blocks. In order to lift, move, turn, or put a ship block at a convenient location fur assembling, workers in a shipyard use cranes, wires, and lugs temporarily attached to the block. In the procedure of lifting and turning a ship block with a crane, it is important to find suitable lug points and wires to do the handling efficiently and prevent accidents. Evaluation of forces in lugs and wires is necessary, but the problem is rather complex due to nonlinearity and nonuniqueness. In the present development, the nonlinear system of equations for quasi-static equilibriums is derived and a Newton type solution method is adopted to solve the system. The importance of initial estimates to the solution is illustrated and two approaches are utilized and compared. With the program developed, users can assign lug points on the CAD model by mouse and choose various linking devices at each crane point. Users can try to simulate the motion for any prescribed conditions, compare the motion of the block and the reactions and choose appropriate lug points and the type of wires and lugs.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.9
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• pp.816-822
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• 2011

In this study, a program has been coded to evaluate propeller thrust rapidly following the effects of propeller shapes and the environmental facts. At this time, Semi-infinite Helical Vortices model is used to predict the induction factor which is introduced by Kawada. This program is based on Wrench's Propeller lifting line theory, and it can predict aerodynamic coefficients such as thrust, power, and efficiency. First of all, this program is compared with test results of NACA reports to verify of the reliability. Secondly, subsonic wind tunnel test has been performed following variations of propeller's rpm and inflow velocities.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.3
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• pp.431-453
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• 2013

The principal purpose of this paper is to present a novel two phases rational scenario applied in constructing an offshore monopod platform; in which the two phases are the all-ground horizontal construction phase and the post-construction phase. Concerning the all-ground construction phase, a brief investigation of its different stages, i.e., pre-fabrication, fabrication, pre-assembling, positioning, assembling, and surface finishing is introduced. The important practical aspects of such construction phase are investigated without going into the nitty-gritty of the details involved therein. Concerning the post-construction phase, a clear investigation of its sequential stages, i.e., lifting, moving and up-righting is introduced. A finite element model (FEM) of the monopod platform is created to perform the structural analysis necessary to decide the suspension points/devices and the handling scenario during the various stages of the post-construction phase on a rational wise. Such structural analysis is performed within the framework of the three dimensional quasi-static modeling and analysis aiming at simulating the realistic handling condition, and hence introducing a reliable physical interpretation of the numerical results. For the whole effort to be demonstrated efficiently, the results obtained are analyzed, the conclusions are presented, and few related recommendations are suggested.

• Journal of Ship and Ocean Technology
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• v.12 no.2
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• pp.41-52
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• 2008

The development of a high-lift rudder is needed because low speed full ships such as the VLCC(Very Large Crude oil Carrier) have difficulty for obtaining enough lifting force from a common rudder. The rudder of a ship is generally positioned behind the hull and propeller. Therefore, rudder design should consider the interactions between hull, propeller, and rudder. In the present study, the FLUENT code and body fitted mesh systems generated by the GRIDGEN program are adopted for the numerical simulations of flow characteristics around a rudder that is interacting with hull and propeller. Sliding mesh model(SMM) is adopted to analyze the interaction between propeller rotation and wake flow behind hull. Several numerical simulations are performed to compare the interactions such as hull-rudder, propeller-rudder, and hull-propeller-rudder. Also, we consider relationships between the interactions. The results of present numerical simulations show the variation of flow characteristics by the interaction between hull, propeller, and rudder, and these results are compared with an existing experimental result. The present study demonstrates that numerical simulations can be used effectively in the design of high-lift rudder behind low speed full ship.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.30 no.2
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• pp.1-6
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• 2022

Recently, the development of UAM, which was named by NASA as an alternative to solve the traffic and environmental problems caused by the rapidly progressing urbanization. When designing UAM, the location of lift fans greatly affects the core technology of the eVTOL type, distributed electric propulsion technology and aerodynamic performance of the vehicle. In this paper, a hybrid UAM model was designed using OpenVSP, an open source aircraft configuration modeling program, and aerodynamic analysis was performed according to the lift fans position change by the vortex lattice method. As a result, it is confirmed that the flight parameters and trailing wakes are stable by fixing the lift fan with the state rotated 0° to the flow direction of the aircraft during cruise flight. Also, OpenVSP is a suitable tool to be used in aircraft configuration modeling and design.

• Wind and Structures
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• v.10 no.6
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• pp.543-554
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• 2007

The suspension bridge is situated in an area of complex topography with both open sea and overland turbulence characteristics, and it is subject to frequent typhoon occurrences. This paper investigates experimentally the possible vortex shedding events of the structure under high wind and typhoon conditions. A single-degree-of-freedom model for the vibration of a unit bridge deck section is adopted to determine the amplitude of vibration and to estimate the parameters related to the lifting force in a vortex shedding event. The results of the studies are presented in a companion paper (Law, et al. 2007). In this paper, statistical analysis on the measured responses of the bridge deck shows that the vibration response at the first torsional mode of the structure has a significant increase at and beyond the critical wind speed for vortex shedding as noted in the wind tunnel tests on a section model of the structure.

• Journal of the Ergonomics Society of Korea
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• v.14 no.1
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• pp.91-96
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• 1995

The purpose of this study was two-fold : (1) to investigate the difference between the lifting capacities based on three different ergonomic approaches; a) the biomechanical, b) the physiological, and c) the phsychophysicalo approach, and the 1991 revised NIOSH Equation, and (2) to develop a comprehensive model for deter- mining maximum weight of lift.

• Korean Journal of Construction Engineering and Management
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• v.13 no.4
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• pp.48-59
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• 2012

Gangform, compared to the traditional forms, is a systemized form which can reduce construction duration and cost by the advantage of using it repeatedly. However, transportation and climbing process of the Gangform is highly dependant on the performance of tower crane. Gangform climbing process takes one day out of six to seven days of a structural work cycle. Tower cranes can not be used in other lifting works when they lift the Gangform during the structural work cycle, causing the delay in the construction project. Numerous efforts and researches have been done in domestic and international industry to solve such limitations of Gangform climbing process. Especially, "A Study on the Development of Automatic Gangform Climbing System for Apartment Housing Construction"has suggested a conceptual model which can climb the Gangform system without a tower crane. In this paper, the technical and economical feasibilities of previously proposed Automatic Gangform climbing system are examined by evaluating its structural stability and lifting load reduction effect.

• Journal of Ship and Ocean Technology
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• v.10 no.2
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• pp.11-23
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• 2006

The model exchange from CAD system to CAE system in valid and effective manner is the major issue of automatic analysis modelling of ship structure. However, model exchange approaches based on the neutral CAD file have resulted in invalid model exchange that could not properly reflect the characteristics of CAD model and CAE model of ship structure. This paper presents the new approach of n-to-n mapping to exchange ship structure model in heterogeneous CAD/CAE environments. In this study, the common model called 'unified ship model for analysis' to directly extract proper information from different CAD systems for ship structural analysis is proposed. Moreover, a command language based model interfacing technique to construct an idealized model for analysis job is also proposed. The proposed approach has been actually implemented in DSME CAD/CAE environment of ship structure such as TRIBON system, PATRAN system and FLUENT system. The applicability and effectiveness of the proposed approach was verified by applying it to the real analysis project for fore-body of ship and block lifting. This application results show that the proposed approach can be effectively used for heterogeneous CAD/CAE environment.