FRC Cold Box 법

윤명진,박성윤,이종명 한국주조공학회 1988 한국주조공학회지 Vol.8 No.2

Zinc Ferrite의 生成機構에 관한 硏究(第一報)

吳伊植,尹明鎭 釜山工業大學校 1981 論文集 Vol.22 No.2

To determine the mechnism by which zinc ferrite forms when ferrous zinc sulphide ore is roasted, the experiment has been carried out under given conditions by sufficiently mixing zinc oxides with ferric oxide in mole ratio (ZnO/Fe₂O₃=1) way. The resluts obatined from this experiment are summarized as follows; (1) Formation of zinc ferrite was not comfirmed by D.T.A thermal analysis property. (2) Formation of zinc ferrite was confirmed by X-ray diffraction analysis in formed compound at alternation of various temperature and it was greatly formed increased temperature, 1.e, zinc ferrite was not confirmed at less than 700℃, but was found at above 700℃, (3) Zinc leaching rate of synthetic zinc ferrite on sulphuric acid solution was similiar at low temperature (680℃), but decreased at above 700℃.

계면균열의 인성과 진전 거동

尹命辰,崔柄善 慶一大學校 2002 論文集 Vol.18 No.-

Interfacial crack problems between fiber and matrix in composite materials were discussed. A series of interfacial crack initiation and propagation experiments were conducted using the biaxial loading device for various mode-mixes. From the series of crack experiments, it could be seen that there was a large increase in toughness with shear components. The behavior of interfacial crack propagation is also analyzed as a function of mode-mix. The result shows that the initial crack propagation was delayed as an increase of absolute value of mode-mix. It could be seen that crack initiation velocity was increased with positive mode-mix and was decreased with negative mode-mix. However, it was found that crack propagation was less accelerated with positive mode-mix than the negative mode-mix. Possible causes of trend were thought be the different behavior of contact and/or effects of friction between far field and near-tip field along the interfacial crack.

구상흑연주철재의 화상해석에 의한 평균구상 흑연크기와 피로강도

윤명진,조현제 한국경영공학회 2002 한국경영공학회지 Vol.7 No.1

중탄소강의 피로크랙 개폐구의 특성 및 피로강도의 평가

윤명진 한국공작기계학회 1997 한국생산제조학회지 Vol.6 No.1

It is not clearly known how surface defects or inclusions of a medium carbon steel affect a fatigue strength. In this study, we used SM35C specimens with spheroidized cementite structure to eliminate dependence of miro structure of fatigue crack. The investigation was carried out by behavior of crack closure at non-propagating crack and effect of the fatigue limit according to the artificial defects size. Experimental findings are obtained as follows : (1) Fatigue crack initiation point of medium carbon steel with spheroidized cementite structure is at the surface defects. (2) Non-propagating crack length of smooth specimen is equal to the critical size of defect. (3) Considering the opening and closure behavior of fatigue crack, the defect shape results in various crack opening displacement, while it does not affects the fatigue limit level of medium carbon steel with spheroidized cementite structure. 4) The critical length of the non-propagating crack of smooth specimen is the same as critical size of defect in transient area which determines threshold condition in steel with spheroidized cementite structure.

中炭素鋼의 疲勞强度의 定量的 評價

尹命辰 慶一大學校 1996 論文集 Vol.13 No.2

It is not clearly known how surface defects or inclusions of a medium carbon steel affect a fatique strength. In this study, we use SM35C specimens with spheroidized cementite structure to eliminate dependence of micro structure of fatigue crack. The investigation was carried out by crack closure, threshold condition and relation of defects size and fatigue limit. Experimenta findings are obtained as follows : (1) Fatigue crack initiation point of medium carbon steel with spheroidized cementite structure is surface defects. (2) Non-propagating crack length of smooth specimen and the critical size of defect is coincide. (3) In this case, fatigue limit of artificially defected specimen is lower than that of a flawless one, however, there exist allowance size of defect which don't get to influence at fatigue limit. (4) The critical length of the non-propagating crack of smooth specimen is the critical size of defect in transient area which decide threshold condition in steel with spheroidized cementite structure.

微小疲勞크랙의 傳播下限界條件에 關한 硏究

尹命辰 慶一大學校 1988 論文集 Vol.4 No.1

The critical size of artificially induced micro-holes in 0.17%, 0.36% carbon steel specinens with spheroidized cementite and in 0.17% Carbon steel specimens with martensite structure is compared with annealed pre-crack in order to discuss the physical meaning of the fatigue limit and evaluation of the tilerant microflaw size at the stress level of the fatigue limit. Results obtained were summarized as follows; (1) In this study, non-propagating crack length of smooth specimen and critical pre-crack length (1c) is coincide. (2) In the carbon steels with spheroidized cementite structure, critical pre-crack length(1c) and allowable micro-hole size (dc) is coincide each other at the fatigue limit level. (3) In has been published that there exists a particular size of micro-hole which has no effect on the fatigue limit. In this study, the micro-hole of critical size can be regarded asequivalent to a tolerant microflaw which would not reduce the fatigue limit.

HVOF용사 코팅한 SM490B용접재의 피로크랙성장에 미치는 후 열처리의 영향

윤명진 한국경영공학회 2007 한국경영공학회지 Vol.12 No.3

velocity oxygen-fuel thermal spray coating of the WC-Co cermet material is a well-established process for modifying the surface properties of the structural components exposed to the corrosive and wear attacks. In this study, HVOF coated SM490B are prepared to evaluation of the effect of coating and post-heat treatment on fatigue crack growth behavior. The pre-crack of the fatigue crack growth test specimens machined at deposited material area, heat affected zone and boundary, respectively. Through these test, the following results are obtained: 1) The fatigue crack of coated specimens propagated more rapidly than non-coated specimen in all specimens. 2) In the same coating thickness specimens, the specimens with pre-crack at boundary more rapidly propagated than the specimens with pre-crack at HAZ and deposited material area. This is probably because whereas the structure of the deposited material zone is very strong thanks to evenly distributed minute carbide or minute martensite, the structure of the edge is highly unstable and contains diverse defects. 3) In three type specimens, the fatigue crack growth rate of post-heat treatment specimen decrease in near-threshold value, while it was about the same in intermediated region and high growth rate region. These results can be used as basic data in a structural integrity evaluation of rolled SM490B weldments considering HVOF coating.

중ㆍ저 탄소강의 결함투영면적의 파괴역학적 평가

尹命辰 慶一大學校 1999 論文集 Vol.16 No.5

The investigation is carried out by a quantitative evaluation relationship between fracture mechanics and √area. We study this issue using SM15C and SM35C materials and the current conclusions may be summarized as follows. (1) Surface nonmetallic inclusions have a more harmful effect than interior inclusions. Different effects of inclusions whit various shapes and sizes at various locations cause a large scatter of fatigue strength. Therefore, it is almost impossible to predit the fatigue limit of individual specimens and machine components. (2) The lower limit σwl of scatters of fatigue strength can be predicted by the square root of the projected area (√area) of inclusions are the crucial influential parameters. The value of σwl depends on the maximum inclusion size ((√areamax) which is expected to be contained in specimens or machine componednts. (3) The fatigue limit of un-notched specimens is approximately proportional to 70 ∼720 of Hv. When the values of Hv increases beyond 400, the fatigue limit shows a distince drop from fatigue strength expected fromula(4). This is because nonmetallic inclusions in hard materials become the origin of fatigue fracture.

過小應力이 疲勞에 미치는 影響

尹命辰 慶北工業專門大學 1978 論文集 Vol.15 No.-

Using R20 Rounded Specimens of carbon steel, the fatigue tests under Varying two step loads are performed and following results has been obtained. 1) In case of the constant stress fatigue experiment, the fatigue limit is 12㎘/㎟ 2) The fatigue limits, ?? and ?? are similar in the constant stress experiment. 3) The ∑n/N of values considered repeating ratio of lower stress in varying load tests contained lower stress may be below for fracture. 4) It has been shown that the crack behavior propagate widely in upper stress and narrowly in lower stress.