http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
하지웅(Jiwoong Ha),허훈(Hoon Huh),박창욱(Changuk Park),안용덕(Yong-Dok An) 한국자동차공학회 2009 한국자동차공학회 부문종합 학술대회 Vol.2009 No.4
Recently, interest in the laser welding to assemble components of the auto-body has increased in the automotive industry due to its productivity, efficiency and reliability. When car crash occurs, crash performance and deformation mode of the auto-body are changed according to the location and shape of laser welds. In order to understand the crash behavior of auto-body through the FE analysis, the laser welded parts should be modeled physically compatibly and simply. This paper evaluates the compatible FE modeling technique for laser welds in crash analyses. A single laser welded part in a stich shape is modeled by a group of numerous beam elements or hexahedron elements. FE analyses of cross tension test and lap-shear test under the quasi-static condition were carried out according to the number of elements, panel mesh size, and the relative position of the laser weld to the panel mesh. From the comparison between experiment and analysis results which are load and displacement curve, suitable modeling technique, which has hardly influence on analysis results, for laser welds in crash analyses is suggested.
하지웅(Jiwoong Ha),허훈(Hoon Huh),송문종(Moon-Jong Song),안용덕(Yong-Dok An),박창욱(Changuk Park) 한국자동차공학회 2010 한국자동차공학회 부문종합 학술대회 Vol.2010 No.5
This paper is concerned with the evaluation of the failure loads of the laser welding under combined axial and shear loading conditions using experiments and FE analysis. A single laser welding whose bead length was 25㎜ in a stich shape was conducted to CR340 2.0t using CO₂ laser equipped with a remote laser scanner. Quasi-static cross tension tests of the laser welding were carried out with different loading angles from 0° to 75° in order to impose the different combined loads conditions on the laser welding. Based on the experimental results, failure loads and failure behaviors of the laser welding are investigated with respect to different loading angles. Failure loads of the laser welding obtained from failure tests are interpolated to investigate failure characteristics and construct the empirical engineering failure model. Additionally, in order to evaluate the failure characteristics of the laser welding of thinner steel sheets, FE analysis of CR340 0.8t and 1.2t was carried out in the same condition of the failure test for the laser welding of CR340 2.0t.
하지웅(Jiwoong Ha),허훈(Hoon Huh),장순근(Soonkeun Jang) 한국자동차공학회 2012 한국자동차공학회 부문종합 학술대회 Vol.2012 No.5
This paper is concerned with the failure characteristics and the failure loads of laser welding in SPRC340 1.2t steel sheet under the combined normal and shear loading conditions. The testing fixture and the specimen proposed by Song and Huh and newly designed fixtures, loading angles of 80° and 85°, in this paper are used to impose the combined normal and shear load on laser welding at a loading angle from 0° to 85°. Especially for experiment of pure-shear loading condition, a loading angle of 90°, testing fixture and specimen are newly designed to evaluate the strength of laser welding under the same condition of two-layer laser welding. Using these testing fixtures and specimens, quasi-static and dynamic failure tests of the laser welds are conducted with the nine different combined loading conditions. The failure load and failure behavior of laser welding are investigated with different loading conditions. Dynamic effects on the failure load of laser welding, which is critical for structural crashworthiness, are also examined based on the experimental data. In order to evaluate the effect of the strain rate on the failure contour of laser welding under combined normal and shear loads, the failure loads measured from the experiment are decomposed into the two components along the normal and shear directions.
복합하중조건에서 AHSS 점용접부의 준정적 파단특성 연구
하지웅(Jiwoong Ha),허훈(Hoon Huh),이홍우(Hongwoo Lee),김교성(Kyo-seong Kim) 한국자동차공학회 2010 한국자동차공학회 학술대회 및 전시회 Vol.2010 No.11
This paper is concerned with the failure characteristic and the failure load of spot welds of AHSS under combined axial and shear loading conditions. The testing fixture and the specimen are newly designed to impose the pure-shear load on a spot weld. The testing fixture and the specimen proposed Song and Huh1 are used to impose the combined axial and shear load from 0° to 75° on spot welds. Using those testing fixture and specimens, failure tests of the spot weld of 590TRIP 1.2t, 780DP 1.0t, and 980DP 1.2t are conducted with seven different combined loading conditions. Based on the experimental results, failure loads and failure behaviors of the spot weld are investigated with respect to different loading angles. Failure loads of the spot weld obtained from failure tests are interpolated to construct Song and Huh’s failure model1, which facilitates the failure description of spot welds in the macroscopic finite element analysis of auto-body structure.
하지웅(Jiwoong Ha),김유종(Yujong Kim),허훈(Hoon Huh),임지호(Jiho Lim) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
This paper propose an alternative methodology to construct the dynamic failure model of a spot weld under combined loading conditions for auto-body crash analyses using cross-tension and lap-shear tests. In order to construct the failure model proposed by Song and Huh, failure tests of spot welds should be carried out at intervals of 15˚ from 0˚ to 90˚ or cross-tension and pure-shear tests. But this methodology is not practical because of too difficult and a large number of experiments. In order to substitute lap-shear tests for pure-shear tests, correlation equation between failure loads of pure-shear and lap-shear tests is derived from stress distribution that was assumed around a nugget at failure of a spot weld. Using failure loads of lap-shear and cross-tension tests and β-norm 1.45, Song and Huh’s dynamic failure model of a spot weld is constructed simply. With the failure model which is constructed by the alternative methodology, FE analyses in which are failure loads and failure behaviors of the spot weld are investigated carried out.
하지웅(Jiwoong Ha),허훈(Hoon Huh),임승찬(Seung-Chan Lim),이홍우(Hongwoo Lee),남재복(Jae-Bok Nam) 한국자동차공학회 2011 한국자동차공학회 학술대회 및 전시회 Vol.2011 No.11
This paper is concerned with the failure characteristics and the failure criterion of spot welds of a dissimilar AHSS combination under combined axial and shear loading conditions. In order to keep the constant ratio of the axial load to the shear load acting on the spot weld during the failure test, the testing fixture and the specimen proposed by Song et al. for a loading angle ranging from 0° to 75° and the newly designed fixture and specimen for loading angle of 90° are used for the failure tests to obtain failure loads and to identify the failure behavior of spot weld of a dissimilar AHSS combination. The newly designed fixture and specimen can obtain more correct failure loads as preventing rotation of spot welds during the failure tests at a loading angle of 90°. The failure loads of spot welds were investigated with experiments for the spot weld of DP780 1.2t and DP980 1.2t steel sheet combination. The failure loads obtained at various loading angles are utilized to construct the failure criterion proposed Song and Huh for description of failure behavior of spot welds in the crash analysis or the strength analysis of an auto-body.
하지웅(Jiwoong Ha),송정한(Junghan Song),허훈(Hoon Huh),임지호(Jiho Lim),박성호(Sungho Park) 한국자동차공학회 2008 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
This paper propose a methodology to identify the dynamic material properties of the HAZ near the base metal in a resistance spot weld at various strain rates. The mechanical properties of the HAZ of SPRC340R were obtained by fabricating thermal simulated HAZ specimens which have similar hardness and microstructure as the actual weld HAZ near the base metal. The thermal simulated HAZ specimens are fabricated using the Material Thermal Cycle Simulator (MTCS). Then, dynamic tensile tests are performed at various strain rates of 0.001 /sec to 100 /sec. Finite element analysis of tensile-shear tests were done under the static and dynamic loading conditions to verify the validity and effectiveness of thermal simulated HAZ properties. Load and displacement curves were obtained with and without applying the material properties of HAZ. The curves are compared to the experimental data. The amount of errors between the analysis and experiment were reduced when the material properties of thermal simulated HAZ were applied to the HAZ. The comparison demonstrates that the dynamic material properties obtained from thermal simulated HAZ specimens are valid for the analysis of spot welded specimens.