• Journal of the Society of Naval Architects of Korea
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• v.54 no.2
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• pp.161-169
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• 2017

Recently, ship owners have been requiring the assessment of the maneuverability of twin-screw ships under mechanical failures. Because this kind of assessment has not yet been conducted, it is necessary to study the types of machinery failures that can significantly affect the maneuverability of a ship, and to construct a procedure to simulate the maneuvering behavior under such failures. In this paper, the sole focus is the steering system failure from among the variety of failure types, and the maneuvering behavior of the ship under the single rudder failure is simulated for an investigation of the unique characteristics. First, the mathematical model for the twin-screw container ship is verified by comparing the simulated results for the $35^{\circ}$ turning test, $10^{\circ}/10^{\circ}$ zigzag test, and $20^{\circ}/20^{\circ}$ zigzag test under the normal operating condition with those obtained from free running model tests. After the IMO maneuvering tests are additionally simulated under the single rudder failure, the results are reviewed to investigate the maneuvering characteristics that are due to the failure. Further, the $35^{\circ}/35^{\circ}$ zigzag test and the $35^{\circ}$ turning test are simulated to additionally investigate the effects of the single rudder failure on the steering and turning abilities.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.1012-1015
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• 2001

The purpose of this paper is to evaluate the specific cutting energy characteristics during turning SM45C steel. Using the orthogonal array method the specific cutting energy has been predicted. And the significance of the equation is checked by ANOVA test. Predicted values of specific cutting energy are well concide with the measured ones. When the feed rate becaomes larger than 0.5mm/rev, predicted specific cutting energy increases.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.9
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• pp.20-24
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• 2006

Wind tunnel tests were conducted to compare gliding and turning performance of normal cruciform parachutes with newly modified cruciform parachutes. Modified cruciform parachute has better gliding performance than original cruciform parachutes but, modified cruciform parachute has worse turning performance than original cruciform parachute.

• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.96-97
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• 2001

A 110 mm diameter aspheric metal secondary mirror for a test model of an earth observation satellite camera was fabricated by ultra-precision single point diamond turning (SPDT) . Without a conventional polishing process, the surface texture of R$\sub$a/=2.8 nm, and the form error of R$\sub$a/=0.05 λ has been stably achieved In a laboratory condition. (omitted)

• Journal of the Society of Naval Architects of Korea
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• v.52 no.1
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• pp.61-69
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• 2015

In the beginning of the 1990's, numerous shaft bearing damages, especially in aft stern tube bearing, were reported. The main reasons of bearing damages were estimated that hull deflections have been increased by more flexible hulls and propeller dynamic loads have not been considered in shaft alignment. After that time, studies to take into account hull deflections in shaft alignment have been actively carried out, but for the latter leave much to be desired. In this study, the effects of the propeller forces on the propeller shaft bearing have been investigated by estimating thrust eccentricity as reasonable as possible although some assumptions to simulate turning of ship were introduced. Three dimensional nominal wake to estimate thrust eccentricity have been calculated by using CFD analysis and model test in the towing tank. This study presents the procedure to estimate the propeller eccentric forces and their influence on the stern tube bearing for a container carrier. As a result, it has been found that the lateral propeller forces in turning condition should be considered in shaft alignment to prevent shaft bearing damages.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.3
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• pp.214-221
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• 2005

For decades, airships have being developed in Europe (especially German) and America. Airships are planning to be used for advertisements and airliners as well. In Korea, KARI (Korea Aerospace Research Institute) is developing stratospheric communication airship and the similar research is carried out in Japan. Among them, Zeppelin of German has the cutting-edge airship technology with Zeppelin NT. In this paper, the flight performance and stability were evaluated by comparing mathematical theory and the real test. The stability was examined through dynamic modeling and assured by designing controllers at each flight mode. Elevator angle, rudder angle, magnitude of thrust and tilting angle of thrust vector were used as control inputs. Moreover, after measuring the airship velocity, flight direction, magnitude and direction of the wind, attitude angles and trajectories of the airship at each flight mode, the results were compared with the simulation. To get the reasonable data, low-pass filter and band-stop filter were designed to get rid of the sensor noise and engine vibration. The test was accomplished at cruise mode, turning mode, and deceleration. To conclude, with comparing the simulation data and flight test data, it could be known that the dynamic model used in this paper was reasonable.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.34 no.1
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• pp.62-66
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• 1998

The maneuverabilities of the training ship M.S. HEUIMANGBONG were studied, based on the data obtained from her Z test. The results obtained were summerized as follows: 1. The maneuvering indices K' and T'of the M.S. HEUIMANGBONG were 0.542, 1.305 at 10$^{\circ}$Z Test and 0.433, 1.351 at 20$^{\circ}$Z test and 0.442, 1.388 at 30$^{\circ}$Z test respectively. The above calculated values K', T' showed that her maneuverabilities were more effective when her rudder was used to small angle than to large angle. 2. As the overshoot angles of the starbord side of the M.S. HEUIMANGBONG were larger than those of port side at 10$^{\circ}$, 20$^{\circ}$and 30$^{\circ}$Z test, her maneuverabilities in port turning were found to be higher than in starbord turning. 3. The running distance of a turn at her 10$^{\circ}$Z test was about 9.9 times her own length and she was considered to have a good maneuverabilities synthetically

• Journal of the Korean Society for Precision Engineering
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• v.21 no.10
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• pp.20-25
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• 2004

Using the multiple regression analysis cutting forces of turning processes have been predicted based on the cutting conditions such as feed rate(f), depth of cut(d), and cutting velocity(v). The statistical inference of the equation was checked by ANOVA test. The validity of the proposed regression analysis was verified by two sets of cutting tests of 27 cutting conditions and the additional cutting tests of 18 cutting conditions. From the results of analytical and experimental studies, it was found that there was no significant difference between the measured and predicted cutting forces. Also, the shear and friction characteristics of turning processes were analyzed with predicted cutting forces.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.68-71
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• 2000

A tool holder system has been designed to measure cutting forces in diamond turning. This system includes a 3-component piezo-electric tranducer. In this research, tool holder system is modeled by considering the element dividing, material properties, and boundary conditions using MSC/PATRAN. Mode and frequency analysis of structure is simulated by MSC/NASTRAN, for the purpose of developing the effective design. In addition, tool holder system is verified by vibration test using accelerometer. This system will aid to the development of Fast Tool Servo.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.5
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• pp.186-194
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• 2000

The purpose of this study is to investigate the difference in cutting characteristics of cermet, carbide and coated carbide tools in the similar application range via turning test of various conditions. The cermet and carbide tools in the range of ISO P10 grade were developed using optimum compositions with a view to obtaining a high toughness and hardness by PM process. First mechanical properties were characterized on these tools. Experimental results of wear behaviour and resistance to fracturing were presented and discussed in the turning of gray cast iron and alloy steels by cermet, carbide and coated carbide tools. The coated carbide tool shows similar cutting performance compared to the cermet, while the cermet has better combination of wear resistance and toughness of high speed (V=500m/min) cutting in comparison with carbide and coated carbide tools, and also shows a potentiality for cast iron cutting. Fe adhesive behaviour on the tools and surface roughness of workpieces were explained by chemical affinity between tools and workpieces.