복합하중조건에서 점용접부의 동적 파단특성 연구

송정한(Junghan Song),허훈(Hoon Huh),임지호(Jiho Lim),박성호(Sungho Park) 한국자동차공학회 2008 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

This paper is concerned with the evaluation of the dynamic failure load of the spot weld under combined axial and shear loading conditions. The testing fixture are designed to impose the combined axial and shear load on the spot weld. Using the proposed testing fixtures and specimens, quasi-static and dynamic failure tests of the spot weld are conducted with seven different combined loading conditions. The failure load and failure behavior of the spot weld are investigated with different loading conditions. Dynamic effects on the failure load of the spot weld, which is critical for structural crash worthiness, are also examined based on the experimental data. In order to evaluate the effect of the strain rate on the failure contour of the spot weld under combined axial and shear loads, the failure loads measured from the experiment are decomposed into the two components along the axial and shear directions. Experimental results indicate that the failure contour is expanded with increasing strain rates according to the rate sensitivity of the ultimate stress for welded material.

이종소재 점용접부의 파단특성 연구

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.

복합하중조건에서 일자형 레이저 용접부의 동적 파단특성

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.

고강도 강의 이종 재질 및 두께 간 프로젝션용접부 전단 파단 하중 예측

한기열,하상언,Siva Prasad Murugan,박영도,이형일 대한기계학회 2019 大韓機械學會論文集A Vol.43 No.11

This study aims at predicting shear fracture load of the projection weld part, which is welded with dissimilar materials and thickness of high strength steel using dimensional analysis. After projection welding experiment, lap shear test was performed to obtain shear fracture load. The nugget size, plate thickness and tensile strength of base material were proportional to the shear fracture load. Shear fracture load obtained was lower than predicted value and partial interfacial fracture occurred when both upper and lower welded parts have high tensile strength and thickness. The predict equation for shear fracture loads for interfacial fracture and pullout fracture represent average error is 5.4 and 6.4 % respectively, compared with the experimental results. The failure mode was analyzed with the relationship of plate thickness and the nugget size, and the critical nugget size for pullout fracture was suggested as 5.3√tm using the average thickness of the upper and lower welded specimens. 본 연구에선 차원 해석을 활용해 고강도 강의 이종 재질 및 두께 간 프로젝션용접부 전단 파단 하중을 예측한다. 프로젝션용접 실험 후 lap shear 시험을 수행해 전단 파단 하중을 측정했으며 판재 두께, 너깃 크기, 모재 최대 인장강도가 증가할수록 전단 파단 하중이 증가한다. 상/하부 용접 시편 모두 판재 두께가 두껍고 높은 인장강도를 가지는 조건들은 lap shear 시험 시 일부 버튼식 파단이 발생했고, 예측값보다 현저히 낮은 전단 파단 하중을 획득했다. 계면식, 버튼식 파단 모드에 대한 전단 파단 하중 예측식과 실험 간 평균 오차는 각각 5.4, 6.4%이다. 고강도 강의 판재 두께와 너깃 크기에 따른 파단 모드를 분석했으며 버튼식 파단이 발생하는 임계 너깃 크기를 상/하부 용접 시편 평균 두께를 활용해 5.3√tm으로 제시한다.

EWK 모델을 적용한 점용접부 파단특성 예측

김대영(Dae Young Kim),김정민(Jung Min Kim),김헌영(Heon Young Kim),송종호(Jong Ho Song),김관회(Koan Hoi Kim) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11

The welding point has been represented by rigid body element or link element in finite element analysis and simple failure criteria have been used for failure after large deformation. However, since the failure model of link element is removed at the highest loading point, it cannot support the load after the failure of welding point. Since this affects the energy absorbing characteristics of whole model in structural deformation, it became the main reason for the problem of analysis. Therefore, this paper simulated the failure characteristics of base metal of welding part by applying the EWK failure model and tried to predict the energy absorbing characteristics of base metal after failure, and verified by comparing the test and analysis. In order to express the behavior and failure of material, tensile tests and EWK tests(R notch type, U notch type, R parameter type) were performed. Also, we tried to predict the occurrence of tearing of base metal and load characteristics considering the welding part by comparing with the test result applying the EWK failure model for typical welding specimens(cross type, T type, Ⅰ type).

적층복합재료 패널의 확률론적 비선형 초기파단하중 및 좌굴하중에 관한 연구

방제성 한국구조물진단유지관리공학회 2013 한국구조물진단유지관리공학회 논문집 Vol.17 No.6

복합재료가 신재생 에너지 산업 관련 구조물 및 해양 구조물에서 좀 더 신뢰도 있는 주 하중 부재로 사용되기 위하여 복합재료평판의 확률론적 비선형 초기 파단 하중과 원공과 곡률이 있는 복합재료판의 확률론적 비선형 좌굴 하중이 평가되었다. 주어진 설계 추출점에서의 확정론적 유한요소해석 결과를 바탕으로 반응면기법을 이용하여 한계상태면을 확률변수로 이루어진 2차 다항식으로 근사하였다. 또한, MPFP 근처에서 좀 더 정확하게 한계상태면을 근사하기 위하여 반복적 선형보간법이 적용되었다. 파괴확률을 평가하기 위하여 근사된 한계상태면 상에서 향상된 일계이차모멘트법과 몬테카를로법이 수행되었다. 마지막으로 파단에 영향을 주는 주요한 확률변수를 파악하기 위하여 변환된 확률변수에 대한 신뢰도지수의 감도를 계산하였다. Probabilistic nonlinear first ply failure loads of flat composite panels and nonlinear buckling loads of curved composite panels with cutouts are estimated to provide the more reliable main load carrying structure in the renewable energy industry and offshore structures. The response surface method approximates limit state surface to a second order polynomial form of random variables with the results of deterministic finite element analyses at given sampling design points. Furthermore, the iterative linear interpolation scheme is used to obtain a more accurate approximation of the limit state surface near the most probable failure point (MPFP). The advanced first order second moment method and the Monte Carlo method are performed on an approximated limit state surface to evaluate the probability of failure. Finally, the sensitivity of the reliability index with respect to transformed random variables is investigated to figure out the main random variables that have an effect on failures.

충돌 해석에서의 점용접부 모델링에 관한 연구

송정한(Junghan Song),허훈(Hoon Huh),김홍기(Honggee Kim),박성호(Sungho Park) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

Simulation of vehicle crashes using the finite element method has made major advances in the last several years. Every major automotive company now uses CAE to perform virtual crash tests. Designers can mow quickly adjust the structural performance before performing a physical crash test. Compared to physical crash tests, the virtual simulation is less costly and faster which allows manufactures to reduce costs and vehicle development time. In order to produce more efficient and precise simulations, it is needed to adopt the dynamic property of materials and the failure modeling of resistance spot weld. The resistance spot weld in most current finite element crash models are characterized as a rigid beam at the location of the weld. The role of this rigid beam is simply to transfer the load across the welded component. The spot weld elements is design to be failed by some failure criteria which is function of axial and shear load at the rigid beam. For this reason, the calculation of the load at the rigid beam is important to predict the failure of the spot weld. In this paper, the numerical simulations are carried out to evaluate the calculation of the load at the rigid beam. The first study conducted is to examine the effect of mesh size on the load at the rigid beam. The effect of element shape on the welded components is, then, investigated. Finally, the location and the number of welded constrains is changed for the correct prediction of the load on the spot weld element. The analysis results demonstrate that the correct prediction of the load on the spot weld element is achieved by the change of the element shape on the welded component s and the location of welded constrains.

알루미늄 및 용융아연도금강판의 다겹 Self-Piercing Rivet 접합특성에 관한 연구

권의표,이광진 한국기계기술학회 2018 한국기계기술학회지 Vol.20 No.3

Multiple galvanized steel and aluminium alloy sheets were joined by self-piercing rivet(SPR) and hybrid joining(SPR + adhesive bonding). In this study, tensile-shear load and fatigue properties of multi-layer SPR and hybrid joints were investigated. Moreover, tensile-shear deformation behavior of the joints under different specimen configurations was investigated. Depending on the specimen configurations either top sheet tearing failure mode or rivet tail pull-out failure mode was observed during the tensile-shear tests. The top sheet tearing failure mode resulted in low maximum tensile-shear load, but it led to larger displacement value as compared to that in the tail pull-out failure mode. Maximum tensile-shear load of hybrid joints was about four times higher than that of SPR joints. Also, fatigue limit of hybrid joints was about two times higher than that of SPR joints.

충돌해석에서의 점용접부 모델링에 따른 하중특성 평가

송정한(Junghan Song),허훈(Hoon Huh),김홍기(Honggee Kim),박성호(Sungho Kim) 한국자동차공학회 2006 한국 자동차공학회논문집 Vol.14 No.2