UT 와 RT 에서의 용접부 결함 검출 비교에 관한 연구

남궁재관 한국산업안전학회 1996 한국안전학회지 Vol.11 No.4

In this study, specimens were prepared which have some defects on the buttweld joint of mild steel. In order to detect the defects of specimens, the following tests were put to : AUT and RT. When the results of the three tests were compared, the conclusion could be brought to as follows: 1) AUT outstrips RT in the abillity to detect plane defects like slags or cracks, but RT excels AUT in the ability to detect spheroidal defects like blowholes. 2) RT detects neither taper cracks nor very closed cracks, whereas AUT detects both of them. 3) AUT can detect at once plane defects like cracks and spheroidal defects like blowholes.

自動熔接으로 因한 軟鋼熔接部의 機械的性質에 미치게하는 磁場의 影響

南宮在寬 서울産業大學校 1984 논문집 Vol.20 No.1

When we applied the magnetizing system to a submerged-arc welder and then tried the D.C. submerged-arc welding to a mild steel. summarizing results examed that the D.C electromagnetic stirring influenced on the hardness distribution and notch toughness of welded part are like this: (1) Hardness distribution of welded part show a rising tendency based on electromagnetic stirring. It seems to be much larger based on the minimization of solidification, but the changing of bed shape as the hardness caused by strong magnetic field is low and the difference of cooling conditions at the solidificational process of welding have an influence upon this, too (2) Notch toughness of welded part will be better by electromagnetic stirring that is, the stopping power of crack's occurrence and crack's occurrence and crack's propagation in the transition temperatures moved to the lower temperature side by 20℃. It is related to the minimization of final formative structure that the minimization of primary crystal grain caused by electromangetic stirring have an influence on Austenite grain size.

원통둘레 용접부의 온도분포 해석

남궁재관 한국공작기계학회 2008 한국공작기계학회 추계학술대회논문집 Vol.2008 No.-

The study of the solidification process of welded metal is carried out using the finite element method, which is the basic study for optimal design. In the analysis of temperature, the welded zone is cooled as the result of heat conduction to the base menta and heat transfer to the circumference. In the early phase of the temperature in base metal zone is little changed. But after the rise in temperature the whole area is cooled gradually and uniformly with the lapse of 10 seconds, and a temperature change is hardly occurred in the radial direction but in the axial direction.

재료가 다름에 따른 초음파감쇠율의 차가 결함판정에 주는 영향

남궁재관 한국공작기계학회 2004 한국공작기계학회 추계학술대회논문집 Vol.2004 No.-

필릿熔接에서의 殘留應力과 크랙에 關한 硏究

南宮在寬 서울産業大學校 1986 논문집 Vol.24 No.1

A series of theoretical analysis for thermal stress occurred in the first pass was performed under various restraining conditions in T-type fillet weld joint for high tensional steel of 50kg/㎟. And the results, based on the investigation of strength restraint and crack form, are as follows: 1. When the longitudinal restraint is low, critical point of crack lies on the flange slide and crack may be occurred at toe, root and heel. In case f the restraint becomes higher, critical point moves on the web side and the average shearing plastic deformation in each part of the web is proportional to the degree of restraint (inverse of restraining distance). In this case, toe crack of the flange occur followed by root crack and toe crack of the web side. 2. When the restraint for rotation is low, crack may be observed at the toe on the flange. In case of the restraint becomes severer and constrains thermal contraction, crack may be occurred at the root on the web and the toe on the flange.

MoSi₂용사피막의 기계적 특성에 관한 연구

남궁재관 서울산업대학교 산업대학원 1999 大學院論文集 Vol.6 No.-

In order to investigate the mechanical properties of MoSi₂thermal - sprayed coatings, tension and rotating bending fatigue tests have been conducted at the room temperature using specimens of mild steel (SS41) with sprayed molybdenum silicide coatings. It was found that MoSi₂coating metal can hardly have beneficial influences on fatigue strength. Compared with base metal, fatigue mechanism of coating metal cannot get desirable results, but it draws near to the property of fatigue of base metal in proportion to the increase in the frequency of fatigue. Undercoated layers including coating metal are different in the properties of transformation, and the cracks appearing from both surfaces rapidly spread over the coated layers, which cannot be essential causes that can dominate fatigue strength.

軟鋼과 硬鋼熔接의 適合成에 關한 考察

南宮在寬 서울産業大學校 1982 논문집 Vol.17 No.1

In order to study matching weld between mild steel and hard steel, it has been considered the behavior of tensile strength, hardness number distribution and impact value on the submerged are welded joint on grooved angle 60°×type. 1) The tensile strength of the weld metal shows the best condition at non-annealing condition after welding. 2) The microhardness distribution of the weld metal shows a desirable weldabity by Hv max 280, and any crack made hardening and brittle do not occor. 3) In order to improve the effect of absorb energy, it is the best condition to treat annealing at 800℃∼900℃. 4) In comparison with the single metal weld of mild steel or hardsteel, weldiability and all the behavior of mechanical properties of the weld between mild steel.

機械構造用 炭素鋼材熔接의 機械的 性質에 關한 硏究(SM45C)

南宮在寬 서울産業大學校 1981 논문집 Vol.15 No.1

In order to study the mechanical properties of a welded carbon steel for machine structural use, it has considered the behavior of tensile strength, hardness distribution, and impact value on the welded joint submerged for grooved angle 70 type of X. The results are as follows: (1) Although tis tensile strength decreases more or less than before welding, it may as well not to anneal. SM 45C had better results than SS 41 even if the weld of SM 45C is annealed. The value of tensire strength also increases gradually in proportion to its rising temperature in the annealing at more than 700°C. (2) The impact value is absolutely high when annealing. It is the highest only 800°C and should not anneal at the more temperature. Annealing effect shows at 800°C only. Therefore SM 45C is more advantageous than SS41 being disadvantageous at other temperature. (3) Its hardness value is the highest as Hv=370 near the bonded line of the heat affected zone free from deposited metal and other parts are irregular, but showing the fluctuation at Hv=220 is a peculiar advantage than SS41 whose hardness being maximum near the bonded line of deposited metal and decreasing in accordance with the increase in the distance from the bonded line of welded joint. (4) The welding of SM45C shows more advantages than that of SS41 in the behavior of all thetmechanical properties.

노치를 갖는 軟鋼熔接에서 熱影響部의 疲勞破壞擧動

南宮在寬 서울産業大學校 1985 논문집 Vol.22 No.1

For the purpose of investigating the behvivor of fatigue fracture in mild steel welding with notches, I treated with the notch effect influenced upon the fatigue strength of H.A.Z for a small test specimen and examined the results in detail. The results obtained are as follows: (1) In case of the same shapes of notchces, the-fatigue of H.Z.Z is much higher than that of base metal. (2) For V-notch of the factor of stress concentration with range 1.00 to 5.00, in consequence of the fatigue test for notched parts of H.A.Z in mild steel, fatigue strength of the H.A.Z of welded bead, deposited manually (in one pass or two pass) or by unionmelt method (in one pass) represented the same modes and the overage value of 75% compared with the base metal without notches. (3) In relation to the factor of stress concentraction and the notch factor, for the base metal and the test servies of all deposited metal, it represented the same relation between α and β, but the H.A.Z of welded bead represented pretty different results. In a general away, βin the H.A.Z showed a constant tendensy for the value of α is more than 2.

지름이 다른 원통둘레 용접부의 잔류응력 분포 비교 연구

남궁재관 한국공작기계학회 2008 한국공작기계학회 춘계학술대회논문집 Vol.2008 No.-

A knowloedge of the residual stress distribution at circumferential welds can increase the prediction accuracy of a fracture assessment in pipe lines. In this study, in order to predict the residual stress distribution in the circumferential butt-welded pipes were measured, using the hole-drilling strain gauge method. Their practical applications were performed in to two kinds of pipes. As the results, the following characteristics were found. On the inner surface of pipes, the circumferential and axial residual stresses were both tensile near the center line of welding and both of them changed from tensile to compressive as the distance from the center line increased. On the outer surface, however, the circumferential residual stress was shown to be tensile wile the axial residual stress was compressive near the center line of welding, and later they were revered at the region far away from the centerline.