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함경춘,이하성 한국산업안전학회 1992 한국안전학회지 Vol.7 No.1
Disc specimen with the center crack and edge crack simulated by two-dimensional static method is used to analyze the stress field around the crack tip in terms of the stress inten sity factor, K. A simple and convenient method of testing to realize the mixed mode stress intensity factor of the cracked body is used, The conclusions obtatined in this photoelastic analysis are as follows : 1. According to this experiment, cracked disc specimen can be used to demonstrate the mixed mode stress intensity factor analysis by simply changing the crack angle from the loading line. 2. Despite the simplicity and continuous data reading, the photoelastic method shows the slightly lower strain reading comparing to the FEM analysis method. 3. In this photoelastic analysis, K₁of center cracked disc specimen under a pair of compressive load shows negative value as the crack angle increases over 30˚.
Kinematical analysis on the several linkage drives for mechanical presses
함경춘,장동환 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.2
In this paper, a kinematical analysis is preformed to see mechanical characteristics of various linkage drives for a mechanical press. Mechanical characteristics of conventional and newly designed drives are investigated and compared in terms of slide velocity, productivity, load capacity and possible work-piece size. A crank-slider mechanism with arc crank-pin guide is introduced and analyzed particularly for kinematical performance using kinematical analysis software. The new linkage drive turns out to be effective in terms of load and velocity characteristics and productivity. Kinematical performance also provides a basis for the proper selection of mechanical presses.
김상철,함경춘,강동명,Kim, Sang-Chul,Ham, Kyoung-Chun,Kang, Dong-Myeong 한국정밀공학회 1992 한국정밀공학회지 Vol. No.
The effect of mechanical, properties in the plastic zone near the crack-tip was investigated, under various controlled loading conditions, i.e., ${\Delta}K$ increasing, ${\Delta}K$ decreasing, and single overload test. For both ${\Delta}K$ decreasing test and ${\Delta}K$ increasing test with constant stress ratio, it is found that the ratio of material constant m'( ${\Delta}K$ decreasing test) to material constant m( ${\Delta}K$ increasing test) is larger than 1 for n<0.1, and it is equal to 1 for 0.1<n<0.2. But it is smaller than 1 for n>0.2. A modified crack growth rate equation based on Forman's equation which applied stable region of fatigue crack propagation in ${\Delta}K$ decreasing test is proposed. Within the limit of this single overload test, an empirical relation between among the retardation ratio (Nd/ $N^{*}$), the strain hardening exponent (n) and the percent peak load (%PL) has been established.established.
초음파법을 이용한 탄소성 파괴인성치 평가에 있어서 시험편 크기의 영향
강동명,함경춘,우창기 한국산업안전학회 1998 한국안전학회지 Vol.13 No.4
Elastic-plastic fracture toughness(J_(IC)) by ultrasonic method is evaluated in terms of width and thickness. Widths of specimen in 6061-T6 aluminum alloy are 50㎜ and 100㎜, thicknesses of those are 20㎜ and 25㎜, respectively. Elastic-plastic fracture toughness by ultrasonic method is independent of specimen thickness and side groove. Angle beam probe which are placed on the end of the compact specimen detect the maximum crack extension effectively. Comparing with elastic-plastic fracture toughness by ultrasonic method and that of unloading compliance method, J_(IC) of ultrasonic method are underestimated to that of unloading compliance method. Elastic-plastic fracture toughness of width 100㎜ specimen are underestimated to that of width 50㎜ specimen about 20%.
김상철,함경춘,오범석 韓國非破壞檢査學會 1987 한국비파괴검사학회지 Vol.7 No.1
In this experimental research, fracture mechanisms of spheroidal graphite cast iron(As Cast,annealed and normalized)were investigated by using Acoustic Emission (AE) technique. In this study, the data (AE signal) are digitized and processed with the 8 bits micro-computer (APPLE Ⅱ) connected to the AE measuring device without data processing unit. The source of AE signal was estimated by fractography analysis. The results obtained in this experimental study are summarized as follows: For the heterogeneous materials (spheroidal graphite cast iron) with inclusions which may be considered as cracks, it is found that both low and high AE amplitude appear simultaneously and the load is found to be fluctuated in the final stage of deformation. But the lad is not fluctuated in tension test with low AE amplitude only. AE is measured within elastic region and it is confirmed that 0.2% offset yield load agrees approximately with the load point where AE counts decrease steeply after the point of maximum AE counts.