http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
초고장력강판 트리밍 시 클리어런스와 경사각이 전단면 특성에 미치는 영향
최홍석(H. S. Choi),김성귀(S. G. Kim),최희관(H. K. Choi),김병민(B. M. Kim),고대철(D. C. Ko) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.10
In this study, the effect of clearance and inclined angle of die on the sheared edge characteristics in trimming of DP980 sheet, which is widely used in the automotive industry for the lightweight construction of body-in-white has beer evaluated. Trimming load and sheared edge with regard to the process parameters are investigated using finite element analysis. It is shown that maximum trimming load decreases with increasing clearance because of large bending moment resulting in hydrostatic tensile stress in the sheared zone, and tensile typed burr occurs under the trimming clearance above 15.6%t. It is also noted that the negative inclined angle results in better influence on sheared edge and lower trimming load. Furthermore, burr height significantly decreases be-cause localization zone appears to be straight, and the zone is connected from the punch edge to the die edge.
DP980의 트리밍 시 전단면 특성에 미치는 공정변수의 영향
최홍석(H. S. Choi),이지욱(J. W. Lee),김성귀(S. G. Kim),고대철(D. C. Ko),서판기(P. K. Seo),김병민(B. M. Kim) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.5
Ultra high strength steels such as DP980, CP1180 and hot stamped boron steel are widely used in automotive industry for the light weight body. However, sheared edge of the trimmed part made of these steels is sensitive to edge cracking, which leads to unpredicted failure in the subsequent forming process such as bending and hole flanging. Furthermore, trimming tool life decreases due to their higher strength than mild steel. In this study, the effect of process variables on the sheared edge properties in trimming of DP980 sheet. Considered parameters are clearance and inclined angle of trimming die. Trimming load and sheared edge with respect to the parameters are investigated using finite element analysis. Maximum trimming load decreases with increasing clearance because of large bending moment resulting in tensile hydrostatic pressure in the sheared band. Also, tensile type burr occurs under the trimming clearance above 15%t. Inclined angle have better influence on sheared edge and trimming load.
최홍석(H. S. Choi),김병민(B. M. Kim),서판기(P. K. Seo),강충길(C. G. Kang),고대철(D. C. Ko) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.5
When stamping the ultra high strength steel, galling which is characterized by the transfer of sheet material to the tool surface occurs due to a high contact pressure resulted from higher sheet material strength. This galling makes the friction condition unstable and high, leading to the scratches on the sheet and the tool surfaces, and eventually premature tool surface failures. Therefore, the simple and accurate evaluation method of tool scratch is needed for selecting tool material and coating. In this study, pin-on-flat surface test (POFST) is performed to investigate the variation of friction coefficient during the test with the material of STD11 and DP980 under various contact pressures. V-channel ironing test (UCIT) was performed in order to verify POFST. As a result of the test, it was shown that tool life related to scratch is well predicted by POFST.
핫스템핑 부품의 전단가공에서 전단 하중의 저감 및 트리밍 금형 수명 향상을 위한 국부 연화 방법
최홍석(H.S. Choi),임우승(W. S. Lim),강충길(C. G Kang),김병민(B. M. Kim) 한국소성가공학회 2011 한국소성가공학회 학술대회 논문집 Vol.2011 No.5
In genera], hot stamped component is trimmed by high-priced and time consuming laser cutting due to the ultra high strength over 1,500MPa. The aim of this research is to improve trimming die life as well as to decrease trimming load by adjusting the strength at the region to be trimmed. The employed model in the study is hat shape, which is similar to the cross section of conventional hot stamped product. FE-analysis of hot stamping process is performed to evaluate the effect of the tool shape on cooling rate at the part to be trimmed. As a result of hot stamping and trimming experiment, hardness at the flange is decreased according to the distance from contact region with tools to air cooled flange area, and the wear at the cutting tool edge is reduced due to the local softening at the trimming area of the hot stamped part.