• 대한금속재료학회지
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• 제47권5호
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• pp.274-282
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• 2009

To investigate the evolution of deformation texture in dual phase (DP) steels during deep-drawing deformation, deep-drawing experiments were performed. Microtexture measurements were conducted using electron backscattered diffraction (EBSD) to analyze texture evolution. A rate-sensitive polycrystal model was used to predict texture evolution during deep-drawing deformation. In order to evaluate the strain path during deep-drawing deformation, a steady state was assumed in the flange part of a deep-drawn cup. A ratesensitive polycrystal model successfully predicted the texture evolution in DP steels during deep-drawing deformation. The final stable orientations were found to be strongly dependent on the initial location in the blank. Texture analysis revealed that the deep drawability of DP steels decreases as the true strain in the radial direction of the deep-drawn cup increases during deep-drawing deformation.

• Steel and Composite Structures
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• 제41권5호
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• pp.747-759
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• 2021

Built-up Double-I (BD-I) columns have been commonly used for mid-rise steel-frame structures in Iran. These columns consist of two hot rolled IPE sections which are connected by two cover plates and fillet welds. Until 2017, BD-I columns were employed in intermediate moment resisting frames (MRF) using welded flange plate (WFP) connections. To evaluate the seismic behavior of the connections, four samples were made and tested based on cyclic loading according to AISC 341-16. It was concluded that typical samples cannot satisfy the seismic provisions related to intermediate MRFs. In contrast, the proposed connections retrofitted with two-part external diaphragms were able to satisfy not only the seismic requirements related to intermediate MRFs but also those related to special MRFs according to AISC. The numerical modeling of these samples was performed using ABAQUS finite element software. This study compared the hysteresis moment-rotation curves, plastic strains, and behavior modes in both experimental samples and numerical models.

• 소성∙가공
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• 제32권5호
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• pp.268-275
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• 2023

ISO 21029 cryogenic vessel is used to transport cryogenic fluids. High-manganese steel (High-Mn steel) is widely regarded as suitable for use at cryogenic temperatures. The conventional way of manufacturing an ellipsoidal vessel head involves incremental stretching, followed by a spinning process. In this study, an alternative method for forming an ellipsoidal vessel head was proposed. Finite element analysis (FEA) was used to theoretically examine the strain evolution during a multi-stage forming process, which involved progressive stretching, deep drawing, and spinning of High-Mn steel. The distribution of effective strain and strain components were analyzed at different regions of the formed part. The FEA results revealed that only normal strains were evident in the dished region of the vessel head due to the stretching process. However, the flange region experienced complex strain evolution during the subsequent deep drawing and spinning process.

• 한국가스학회지
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• 제16권2호
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• pp.14-17
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• 2012

본 연구에서는 유한요소법을 이용하여 알람밸브의 응력 및 변형거동에 대한 해석적 연구를 수행하였다. 알람밸브의 강도안전성에 대한 연구는 최대시험압력이 2.0MPa인 경우에 대하여 계산하였다. 유한요소법으로 계산한 알람밸브의 최대응력은 항복강도 370MPa의 6.1%에 해당하고, 인장강도 485MPa의 4.6%에 해당하는 결과로 제시되었고, 이것은 커버 플랜지와 밸브몸체 사이의 모퉁이 부근에서 발생하는 것으로 나타났다. 그리고 밸브에서 발생한 최대변형 $12{\mu}m$는 알람밸브 몸체의 중간부근에서 형성되는 것으로 예측되었다. 이러한 연구결과는 대부분의 알람밸브에서 지나치게 높은 강도안전성을 갖도록 설계하는 것으로 지적할 수 있고, 이것은 알람밸브의 중량이나 크기가 증가되는 요소로 작용하고 있음을 알 수 있다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.285-288
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• 2007

The use of commercial finite element analysis software to perform the entire process analysis and springback analysis has increased fast for last decade. Pamstamp2G is one of commercial software to be used widely in the world but it has still not been perfected in the springback prediction accuracy. We must select the combination of input parameters for the highest springback prediction accuracy in Pamstamp2G because springback prediction accuracy is sensitive to input parameters. Then we study the affect of input parameters to use member part for acquiring high springback prediction accuracy in Pamstamp2G. First, we choose important four parameters which are adaptive mesh level at drawing stage and cam flange stage, Gauss integration point number through the thickness and cam offset on basis of experiment. Second, we make a orthogonal array table L82[(7)] which is consist of 8 cases to be combined 4 input parameters, compare to tryout result and select main factors after analyzing affect factors of input parameters by Taguchi's method in 6 sigma. Third, we simulate after changing more detail the conditions of parameters to have big affect. At last, we find the best combination of input parameters for the highest springback prediction accuracy in Pamstamp2G. The results of the study provide the selection of input parameters to Pamstamp2G users who want to Increase the springback prediction accuracy.

• 한국강구조학회 논문집
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• 제12권5호통권48호
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• pp.595-604
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• 2000

유공합성보는 공기조화설비등의 각종 배관으로 인한 용적률의 저하를 완화할 수 있고, 바람과 같은 수평력에 의한 층모멘트 감소등의 구조적 측면에서도 유용하다. 또한 휨강성도 증가되어 하중에 의한 처짐이 적어지고 진동하중이나 충격하중에도 유리하게 되어 건축물의 강성 및 내력을 높이기 위해 사용되고 있다. 그러나 개구부 위치 및 편심여부에 따라 외력에 대한 구조적인 거동이 달라지게 되므로 이에 대한 적절한 검토가 요구된다. 이에 본 논문은 편심유공합성보의 종국내력 및 변형능력에 관한 실험적 연구로서, 무공합성보인 기준시험체와 중심 및 상 하 편심유공합성보 시험체의 실험 및 이론적 고찰을 통하여 각 시험체들의 항복 및 최대내력, 휨 및 전단강성, 개구부주위의 응력분포, 그리고 모멘트-전단력 상관관계등의 구조적 특성을 규명코자 한다.

• 한국강구조학회 논문집
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• 제17권6호통권79호
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• pp.689-697
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• 2005

보 플랜지 절취형 (Reduced Beam Section, RBS) 내진 철골모멘트접합부의 최근 실험결과를 살펴보면, 보 웨브를 볼트 접합한 시험체는 보 웨브를 용접한 시험체에 비해 조기에 스캘럽에서 취성파단이 발생하는 열등한 내진성능을 나타냈다. 과거 여러 연구자들이 수행한 실험 결과 및 본 연구의 수치해석 결과를 종합해 볼 때, 이러한 접합부의 조기 취성파괴는 고전 휨이론과 매우 다른 응력전달 메카니즘에서 기인하는 웨브 볼트의 슬립, 그리고 재료의 인성이 가장 낮은 스캘럽 부근의 응력집중과 밀접한 관련이 있는 것으로 분석된다. 본 연구에서는 실험 및 해석결과를 바탕으로 RBS 접합부의 실제 응력전달경로에 부합되는 새로운 보 웨브 볼트 설계법 및 개선된 상세를 제시하고 실물대 실험을 통하여 방안의 타당성을 입증하였다.

• Structural Engineering and Mechanics
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• 제74권6호
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• pp.723-735
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• 2020

This study is reported the adhesion failure in adhesive bonded composite and specifically for the T-joint structure. Three-dimensional finite element analysis has been performed using a commercial tool and the necessary outcomes are obtained via an eight noded solid element (Solid 185-element) from the library of ANSYS. The structural analysis input has been incurred through ANSYS parametric design language (APDL) code. The normal and shear stress distributions along different layers of the joint structure have been evaluated as the final outcomes. Based on the stress distributions, failure location in the composite joint structure has been identified by using the Tsai-Wu stress failure criterion. It has been found that the failure index is maximum at the interface between flange and web part of the joint (top layer) which indicates the probable location of failure initiation. This kind of failures are considered as adhesion failure and the failure propagation is governed by strain energy release rate (SERR) of fracture mechanics. The different adhesion failure lengths are also considered at the failure location to calculate the SERR values i.e. mode I fracture (opening), mode II fracture (sliding) and mode III fracture (tearing) along the failure front. Also, virtual crack closure technique (VCCT) principle of fracture mechanics steps is used to calculate the above said SERRs. It is found that the mode I SERR is more dominating compared to other two modes of failure for the joint considered. Finally, the influences of various parametric (geometrical and material) effect on SERR of the joint structure are evaluated and discussed in details.

• Steel and Composite Structures
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• 제23권3호
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• pp.273-283
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• 2017

In this paper, it is aimed to present a detail investigation related to structural behavior of laterally unrestrained steel cantilever roof of tribune with slender cross section. The structure is located in Tutak town in $A{\breve{g}}r{{\i}}$ and collapsed on October 25, 2015 at eastern part of Turkey is considered as a case study. This mild sloped roof structure was built from a variable I beam, and supported on steel columns of 5.5 m height covering totally $240m^2$ closed area in plan. The roof of tribune collapsed completely without any indication during first snowfall after construction at midnight a winter day, fortunately before the opening hours. The meteorological records and observations of local persons are combined together to estimate the intensity of snow load in the region and it is compared with the code specified values. Also, the wide/thickness and height/thickness ratios for flange and web are evaluated according to the design codes. Three dimensional finite element model of the existing steel tribune roof is generated considering project drawings and site investigations using commercially available software ANSYS. The displacements, principal stresses and strains along to the cantilever length and column height are given as contour diagrams and graph format. In addition to site investigation, the numerical and analytical works conducted in this study indicate that the unequivocal reasons of the collapse are overloading action of snow load intensity, some mistakes made in the design of steel cantilever beams, insufficient strength and rigidity of the main structural elements, and construction workmanship errors.

• 한국지진공학회논문집
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• 제8권3호
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• pp.87-96
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• 2004

최근에 수행된 보 플랜지 절취형 (Reduced Beam Section, RBS) 내진 철골모멘트접합부의 실험 결과에 의하면, 보 웨브를 볼트 접합한 시험체는 보 웨브를 용접 접합한 시험체에 비해서 조기에 스캘럽을 가로지르는 취성파단이 발생하는 열등한 내진성능을 보였다. 실험결과에 의할 때, 이러한 접합부 취성파괴가 발생하는 주요 원인은 웨브 볼트의 슬립과 고전 휨이론에 의한 예측과는 전혀 다른 응력 전달메카니즘에 의한 스캘럽 부근의 응력집중 때문으로 사료된다. 이는 고전 휨이론에 기초한 전통적 보 웨브 볼트접합부의 설계법을 재검토할 필요가 있음을 시사하는 것이다. 본 연구를 통하여 고전 휨이론에 기초한 현행의 보 웨브 설계법에 문제가 있음을 지적하였다. 실험 및 해석결과를 바탕으로 RBS 접합부의 실제 응력전달경로에 부합되는 새로운 보 웨브 볼트접합 설계법을 제안하였다.