Photoelastic 點熔接이음의 光彈性應力 解析

김부동 서울産業大學校 1979 논문집 Vol.12 No.1

Spot welding as a manufacturing process has long been accepted as an economical and rapid means of fabricating light and medium gage metal. The tear and intermediate failure modes of a spot weldment when loaded in tension shear is .Shown to be determined by the photoelastic investigation of stress distribution. The resells obtained are as follows: (1) This part of the investigation shows the high find complex stress distribution around the nugget edge of a spot weld. (2) The author regards as of especial importance the tear fracture effect as shown by the normal stresses. (3) The specimens of spot welds of light alloys, particularly in thin sheets, failure has taken place by the intermediate fracture.

심 熔接이음材의 疲勞擧動

김부동 서울産業大學校 1999 논문집 Vol.49 No.2

In the manufacturing of car bodies Tailored Blank Method is recently put to good use a working method in which several steel plates are welded and assembled to serve the purpose and then pressed. The purpose of this study is to bring to light characteristics of fatigue behavior on test pieces with seam welded joint in case the sheets are different from each other in their thickness and material. As far as characteristics of fatigue strength are concerned, changes in microstructure, hardness and residual stress of materials have been investigated by using test pieces with seam welded joint. Some conclusions that have been drawn are as follows: 1) As for test pieces welded with two sheets of the same thickness, changes in microstructure can be found only on the weld zone; as for test pieces welded with two sheets of the different thickness, changes in microstructure can be found up to the outside region of the weld zone on the thick plate side. 2) A remarkable rise in from the weld zone, of the specimen. The more distant it is from the weld zone, the lower hardness is. 3) Compressive residual stress has been generated on the weld zone of the specimen, which has tuerned out not to have any effect on fatigue strength.

異種材金屬의 스폿트 및 심熔接(RIF熔接)에 關한 硏究

金富東 서울産業大學校 1982 논문집 Vol.17 No.1

異種材 金屬의 겹침抵抗熔接이음에 있어서 技術的 開發에 關해 硏究해 보았다. 熔接材料表面에는 ring 모양이나 平平한 電極을 使用하게 되는데, 이러한 諸熔接方法들을 RIF 熔接이라고 稱한다. RIF 熔接의 特徵은 金屬板에 電極加壓力을 주어 朔性變形을 일어나게 하고 그 結果 새로운接觸表面을 生成케하여 接合하는 固相壓接의 原理인 것이다. 또한 擴散作用에 依해 接合部의 强度를 向上시키게 된다. 特히 一般熔接方法으로는 不可能한 腋性材의 熔融接合에 效果가 크다.

表面皮膜의 破裂과 點熔接 改善機構

金富東 서울産業大學校 1980 논문집 Vol.13 No.1

When Alclad 2024-T3 is spot welded, the welding quality becomes improved by having surface treatment. This studies are dealt with the improvemental mechanism on the quality of spot welding. For the means of surface treatment the mechanical method and chemical method are adopted. The results obtained are summarized as follows: (1)Oxidizing film decreases a electric conductivity and it prevents the nugget formation. (2)Therefore bursting of oxidizing film is necessary and for the method of it cold diluted solution method is more suitable than wire brushing method. (3)Improvemental mechanism on the quality of spot weldings are: artificial hardening of oxidizing film → bursting of oxidizing film by electrode pressure, failure of unevenness→open the bridge of electric passage.

點熔接鋼板의 破壞位置에 關한 硏究

金富東 서울産業大學校 1983 논문집 Vol.18 No.1

This report estimates the process in which spot welded steel sheets are deformed step by the stresses. On the basic of this estimation the location, where the failure is examined when spot welded steel sheets are subjected to tension-shear loading. The conclusions obtained from the data and experimental results areas follows. 1)The more c/t increases, the better the tear failure and the more difficultly the shear failure. 2)Tear failure readily in -0.05>Xt/C>-0.37, the intermediate failure in 0.03<Xi/C<0.17 and the shear failure at XS=0 just around the welded joint edge. 3)Cornell's paper would be used as criterion which predicts the region of the tear failure in the future study rather than is coincident to this experimental result. 4)The shear failure not only when the loading starts but also after the bending moment arises.

曲線보의 中立軸 決定에 있어서 Timoshenko와 Winkler-Bach 理論式의 光彈性實驗에 依한 比較

金富東 忠州大學校 1976 한국교통대학교 논문집 Vol.8 No.1

Many machine members are curved before a bending mement applide to them such as crane hooks, chain links and frames of punching machines. In calculation the strength of materials, when a rectang ?? cross sectional area is rather large, there will occur a considerable difference in the use of Timoshenko's and Winkler-Bach's formulas or those of straight beam formulas. According as the changing in the radius of the centroidal axis is calculated by two theoretical formulas, the curved beam is bent by coupless applied the ends. When compared the results of photoelastic analysis, it was found that there is an range in which two theoretical formulas correspond considerably according to the radius of the curved beam.

引張荷重을 받는 對稱傾斜形 龜裂을 가진 平板의 應力擴大係數

金富東 忠州大學校 1974 한국교통대학교 논문집 Vol.7 No.-

The increasing number of theoretical and numerical solutions for the crack tip stress intensity factor has widened the scope of application of linear elastic fracture mechanics techology. In this paper, it is shown that the stress intensity factor K is determined by two methods. One of these is based on P.C Paris and G.C. Sin's theoretical expressions for the elastic stress field at the tip of the crack, and the other is a result of photoelastic experiment derived by S.A. Hussainy, H.M. Hasscem and G.K. Bhagawan's slender notches having various crack configurations. In an experimental method, a sharp crack is simulated by a relatively narrow notch terminating in a root radius of 0.8mm a chordal distance of 30mm and an inclined angle of 30°, further more on the symmetric triangular hole in a plate. As a result, the similarity in stress intensity factor was observed and the conformity with theoretical value was ascertained.

Laplace 變換에 依한 彈性받침 有限보의 解析

金富東 충주대학교 1977 한국교통대학교 논문집 Vol.10 No.1

彈性地盤위에 놓인 無限보에 關한 理論式을 利用함과 同時 Laplace 變煥으로 解析해 보았다. Laplace 變煥을 活用하면 Timoshenko의 線形微分方程式으로 푸는 方法보다 수고가 적게 들게 된다. 또한 몇가지 基本的인 形態의 荷重이 作用되는 境遇에 있어서 처짐 公式을 求해 보았다. 表를 마련하여 實際問題를 計算할때 時間과 勞力이 節約되도록 연구해 보았다.

低炭素鋼의 疲勞擧動에 미치는 異種材의 熔着과 結晶粒度 相關性

金富東 서울産業大學校 1978 논문집 Vol.11 No.1

One of the problems relating to fatigue strength of a welded dissimilar metals containing a weld defect is the evaluation of propagation life of fatigue crack initiated from the defect. In this paper, propagation behavior of fatigue crack from the weleded metals not have a annealed and have a full annealed materials of structral low carbon steel, in other words, from the fine grains and the coarse grains zone were examind. The Petch theoris were used. The results obtained are summarized as follows : (1) the fatigue strength of the welded specimens were lower than that of the Parent of the as the 28.3%. (2) Most welded bar for the fatigue tests failed at weld defect as the inclusions. (3) The fatigue cracks started at the coarse grains zone of the deposited metal.

構造用鋼의 리 - 브 十字形 필렛 熔接이음에 있어서 疲勞强度의 改善

金富東 서울산업대학교 1977 논문집 Vol.10 No.1

Fatigue tests on the structural steels with transverse fillet welded joints by flat and vertical welding position were obtained as following results: (1) In the present test range of leg length (h?4mm, t'=6mm, t' being the thickness of plate) the fatigue strength of plates with transverse fillet welded attachments, is little affected by the leg length of fillet. (2) The endurance limits of the welded joints were lower than that of the parent metal. (3) The fatigue strength of the vertical welded joints is 1.09 kg/mm? lower than that of the flat welded joint. (4) As a method for improving the fatigue strength of plates with transverse fillet welded joints, grinding of the toe of fillet weld at ρ=3mm R has proved effective. The improvement amounted to 0.6 kg/㎣ in fatigue strength a times in fatigue crack initiation life and 3 times in fatigue fracture life at ρ=3mm R. (5) Most welded joints failed at the bounded zone or the softened zone in the affected zone. In the case of the toe of fillet at bonded zone, as welded specimens, the fatigue cracks started at the coarse grain zone of the bonded.