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적층압축에 의한 접합재의 경계면 성장거동에 대한 수치 시뮬레이션
정태훈,류제구,後藤學 서울産業大學校 1997 논문집 Vol.45 No.1
Under plane strain compression, of two blocks with sawtoothed interface, the sawtooth growth occurred. We presumed in the previous paper that such growth was caused by the shear-band formation starting from the tip of sawtooth and its degree depended on the material properties of the block. In this paper, Compression in the case where similar blocks are twinned and also compression in the case where dissimilar blocks are twinned variously are carried out in the condition of lubricated interface. Further, in the latter, compression where the interface is degreased is also performed. The degree of growth is experimentally investigated. Moreover, numerical simulations are carried out by the elastic-plastic FEM for the case of the dissimilar blocks with the initial sawtooth angle of 60℃ . In the experiment, the harder material yields larger growth than the softer one, and the growth in the case of initial sawtooth angle 60℃ is greater than that of 90℃ . Larger ratio of total height to sawtooth height gives larger growth in comparison with the previous experimental result. In the case where the dissimilar blocks are twinned, larger difference between material properties leads smaller growth, and the degreased interface leads smaller growth than that in the lubricated one. Furthermore, by the simulation of compression where dissimilar blocks are twinned, it is confirmed that the tendency of the general deformation pattern is very similar to the experiment.
김영수,정태훈,後藤學 한국공작기계학회 2003 한국공작기계학회 추계학술대회논문집 Vol.2003 No.-
It is clearly demonstrated that deeper cups could be formed by single and double stretch-drawings from smaller circular blanks due to such wall-thinning action than in the usual deep-drawing of larger blanks. From this fact, it is emphasized that the deep-drawability of a sheet metal is not evaluated simply by the conventional L.D.R (limiting drawing ratio), but the depth of the drawn cup should also be taken into account. Many experimental data about various metals and thicknesses given in this paper offer a valuable information in this process for more general use which recommends to replace the conventional deep-drawing process by the stretch-drawing process both for single and double operations. In the single stretch-drawing, it is also confirmed that a deeper cup can be produced by raising the blank-holding force at later stage of operation.