• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.2
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• pp.97-106
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• 2001

본 연구에서는 트러스 구조물의 이산최적설계를 위해 유전알고리즘(GA)을 적용하였다. 확률론적인 절차를 통해 설계에 필요한 초기 집단을 생성시킨 후, 설계를 개선시키기 위해서 자연선택 및 적자생존의 원리를 적용하였다. 다하중조건 하에서 트러스 구조물의 중량 최소화를 위해 응력 및 변위 제약을 고려하였다. 먼저, 이미 잘 알려진 트러스 구조물에 대해서 GA를 이용하여 얻은 최적해와 기존 문헌들에서 제시하고 있는 값들을 비교함으로써 GA의 신뢰성 및 적용성을 검증하였고, 이러한 신뢰성 검증을 바탕으로 사용성 있는 트러스 구조물의 이산최적설계를 위해 현재 생산중인 강재제원표로부터 부재가 선택되도록 하였다. 강재의 단면으로는 L형강을 사용하였으며, L형강의 강종은 9개의 강종들 (SS 400, SWS 400, SMA 41, SWS 490Y, SWS 520, SMA 50, SWS 570, SMA 58) 중에서 설계자에 의해 자유롭게 선택되도록 하였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.3 no.4
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• pp.133-142
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• 1979

The fracture toughness of a hot rolled 100 mm thick SS41 steel plate was investigated for various crack ratios and thichnesses using the method of J-integral. The experiments were performed on an MTS machine and the crack initiation point was detected by using an electricl impedance method. The J-integral computed at the initiation point of the slow stable crack growth was almost constant within the range of crack ratios tested. The fracture toughness thus obtained was $J_{1c}/=27.0kgf/mm$ for specimens having fracture plane parallel to the rolling direction and 35.5kgf/mm for those perpendicular to the rolling direction. The J- integral computed at maximum load point was found to be unsuitable for fracture toughness determination, becaese of large variation depending on the crack ratio and thickness. It was also found that the slow stable crack growth increases as the thickness and/or crack ration of the specimen decrease.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.11
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• pp.1124-1130
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• 2007

This paper presents a new way for fabricating sandwich plates with tetrahedral truss cores. The tetrahedral truss cores are manufactured through metal expanding and bending process and then brazed with solid face sheets. The properties of sandwich plates with the tetrahedral truss cores composed of a wrought steel SS41 under compression and shear loading have been investigated. Good agreement is observed between the measured and predicted peak strengths. Comparisons with normalized compressive strength for other cellular metals have indicated that the tetrahedral truss structures outperform aluminum open cell forms and woven core sandwich plates.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.4
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• pp.19-27
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• 1995

Face milling is required to study cutting process with a view of multipoint cutter. This experimental study mainly deals with the single and multi-insert cutting characteristics using coated tool. Because metal cutting of the single and multi-insert has a large relation to the improvement of productivity, the economic cutting process can be achieved by the analysis of proper metal cutting mechanism. Therefore, machining characteristics of face molling in this paper has been studied by investigating the role of different insert number which is concerned with mean cutting force, the RMS values of AE(acoustic emission) signal, tool life and surface roughness in milling SS 41 and SUS 304. The cutting force and AE signal are monitored to make an analysis of cutting process. The surface roughness of the specimens machined by inserts of different numbers is measured at different speeds, feeds and depth of cut. The width of flank wear is also observed.

• Proceedings of the KWS Conference
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• 2000.10a
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• pp.216-218
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• 2000

In case of hardfaced wrapping roll, beadmark shape appear at wrapping roll surface due to irregular wear between weld bead. Irregular wear of this is caused by difference of hardness between weld bead. This study aims at investigating which matrix is good for removing of beadmark at wrapping roll surface. So, we make specimen with martensitic matrix and austenitic matrix. The hardfacing alloys were deposited 4 times on a SS41 steel plate using self-shielding flux cored arc welding method. Difference of hardness between weld bead of specimen with matrix of martensite was higher than specimen with matrix of austenite both as-welded and after heat treatment. Therefore, austenitic matrix is better than martensitic matrix for removing of beadmark of wrapping roll surface.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.2
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• pp.427-432
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• 1995

Surface heat treatment using a laser beam or an electron beam is studied through numerical analyses and experiments. For the surface heat treatment process, a theoretical model is developed to predict the effects of laser beam power, travel speed and properties of a workpiece on the depth and width of the heat affected zone(HAZ). The shape of HAZ and the hardness of heat-treated surface are experimentally obtained using an electron beam. Three materials(SS41, S45C and S55C) are selected as workpiece materials. The hardness of HAZ is increased up to 3 times for materials of a low carbon content. The results of the numerical analysis are compared with those of experiments. The comparison shows that the numerical model predicts larger depths and widths.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.11
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• pp.63-73
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• 1995

A mechanistic force system model considering the flank wear for the face milling process has been developed. The model predicts variation of the cutting forces according to flank wear in face milling over a range of cutting conditions, cutter geometries and cutting process geometries including relative positions of cutter to workpiece and rounouts. Flycutting and multitoth cutting teste were conducted on SS41 mild steel with sintered carbide tool. In order to verify the mechanistic force model considering the flank wear of cutting tools, a series of experiments was performed with single and multitooth cutters in various cutting conditions. The results show good agreement between the predicted and measured cutting force profiles and magnitudes in time and frequency domains.

• Journal of the Korean Society for Precision Engineering
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• v.6 no.4
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• pp.94-102
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• 1989

The effect of plastic strain on the surface integrity of mild steel (SS 41) was studied. This paper shows that the recrystallization technique is adequate to evaluate the plastic strain in a machined surface experimentally. The relations between the plastic strain and the machining conditions are quantitatively evaluated by using the recrystallization technique. The obtained results are summarized as follows. 1. The surface integrity of steel is considerably influenced by the amount of surface region deformation produced by changes in cutting conditions. 2. The plastic strain in machined surface produced by changes of the cutting conditions is evaluated by the recyrstallization technique. 3. The plastic strain increases with the increase of depth of cut and the decrease of rake angle. 4. When the cutting force is high and the rake angle is small, the value of maximum true strain reaches to high. 5. The maximum true strain is related to the cutting energy, and the values increase with the increase of the unit shear and total engergy in constant depth with the increase of the energy values.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2001.11a
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• pp.98-104
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• 2001

Recently, the researches on the prevention of marine oil pollution being strengthened. Sludge oils were unavoidably produced in ship's operations, therefore it is necessary to manage the sludge oils inside the ship itself with the view to prevent marine oil pollution from ship. The present study deals with the ultrasonic breaking systems that recycle the sludge oil from ships into usable oil to be burnt. At the first instanceexperimental studies were carried out to investigate the homogenizing effect of the marine oils and the erosion aspect of horn disc by repeated vibration of ultrasonic transducer. The erosion damages for horn disc SS41 steel with weight loss rate and the irradiation time to max. erosion rate were examined according to the variation of the transducer amplitude, the oil temperature and the immersing depth of horn disc. As the result of it, the erosion aspects of horn disk were varied with oil environments and testing time.

• Transactions of the Korean Society of Mechanical Engineers
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• v.6 no.3
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• pp.232-238
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• 1982

The behavior of corner crack propagation by unidirectional plane bending fatigue was investigated in the butt welded joints of SS41 and SM50 steel plates including an edge through-thickness notch. The properties of fatigue crack propagation were inspected in the weld metal, heat-affected zone, and base metal of the welded joints. Main results obtained are as follows; (1) When a plate with an edge through-thickness notch is loaded by plane bending fatigue in indirection, the 2 variant corner cracks on the upper and lower edge of the plate are initiated and propagated respectively from the notch. (2) In case of a specimen containing a corner crack, it is more reasonable to estimate the crack propagation rate by area of fracture surface than by crack surface length. (3) The rate of fatigue crack propagation becomes faster in the following order; weld metal, heat-affected zone, and base metal. (4) The specimen including reinforcement shape is rapidly failed throughout bond due to effect of its shape when the repeated load exceeds a certain cycle.