• Steel and Composite Structures
• /
• 제47권5호
• /
• pp.601-613
• /
• 2023

Numerous methods have been proposed in predicting formability of sheet metals based on microstructural and macro-scale properties of sheets. However, there are limited number of papers on the optimization problem to increase formability of sheet metals. In the present study, we aim to use novel optimization algorithms in neural networks to maximize the formability of sheet metals based on tensile curve and texture of aluminum sheet metals. In this regard, experimental and numerical evaluations of effects of texture and tensile properties are conducted. The texture effects evaluation is performed using Taylor homogenization method. The data obtained from these evaluations are gathered and utilized to train and validate an artificial neural network (ANN) with different optimization methods. Several optimization method including grey wolf algorithm (GWA), chimp optimization algorithm (ChOA) and whale optimization algorithm (WOA) are engaged in the optimization problems. The results demonstrated that in aluminum alloys the most preferable texture is cube texture for the most formable sheets. On the other hand, slight differences in the tensile behavior of the aluminum sheets in other similar conditions impose no significant decreases in the forming limit diagram under stretch loading conditions.

• 소성∙가공
• /
• 제16권8호
• /
• pp.621-628
• /
• 2007

Nowadays, Exhaust Gas Recirculation(EGR) Cooler is one of the most favorite systems for reducing the generation amount of $NO_x$ and other particle materials from vehicles burning diesel as fuel. Efficiency of the system is mainly dependent on its heat transfer efficiency and this ability is affected by net heat transferring area of the system. For that reason, several types of heat transfer tube such as dimple, wrinkle and spiral types that have large net area are used. However, it is difficult to manufacture the rectangular tube with dimpled type structure because it experiences too much strain around the rectangular tube surface during the forming process. For that reason, in this study, numerical simulation for forming process of non-symmetric dimple shape on a thin sheet metal was carried out. Furthermore, theoretical forming limit curves(forming limit diagram, forming limit stress diagram) were proposed as criteria of formability evaluation. From the results of finite element simulation in view of stress and strain distribution, it is found that the designed process has robustness and feasibility to safely manufacture the dimpled rectangular tube.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
• /
• pp.545-548
• /
• 2003

The purpose of this study is measures vulcanization properties of matter by time of room temperature vulcanization synthetic rubber sheet and the evaluation adhesive properties tested by concrete surface moisture. Also, Its estimated reaction mechanism and adhesion performance between protection mortar and waterproofing layer. The results showed that vulcanization progressed in room temperature and adhesion intensity increased regardless of moisture condition.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 1999년도 춘계학술대회논문집
• /
• pp.7-13
• /
• 1999

Hydroforming is the technology that utilizes hydraulic pressure to form sheet and tube metals in to desired shapes inside die cavities. It can be subdivided into tube hydroforming and sheet hydroforming according to the blanks used. In this paper the simulation of tube and welded blank hydroforming is carried out respectiyely. And simulation results are compared to evaluate formability in tube and welded blank hydroforming of engine mount bracket

• Journal of Welding and Joining
• /
• 제26권5호
• /
• pp.79-89
• /
• 2008

With the increased use of surface textured steel sheet in body-in-white assembly, resistance spot weldability of these steels is considered to be an important subject. This study evaluated nugget formation and weldability by measuring dynamic resistance with various weld pressure, current, and weld time for steel sheet with two different surface roughnesses. The surface roughness for T-H steel ($R_{a}=1.70\;{\mu}m$) was higher than that for T-L steel ($R_{a}=1.33\;{\mu}m$), and resulted in increased contact resistance and heating for T-H steel spot welding. Therefore, at low weld current and weld cycle ranges, the T-H steel showed better weldability over the T-L steel. The evaluations of weld interface showed that the fusion zone in the T-H steel sheet was continuous in contrast to discontinuous fusion zone for T-L steel sheet at the same welding conditions. A comparison of dynamic resistance and tensile-shear strength (TSS) between T-H and T-L steel sheet suggested that high surface roughness provided larger heating at early cycle of welding and larger TSS.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2008년도 춘계학술대회 논문집
• /
• pp.387-390
• /
• 2008

Electromagnetic forming (EMF) technology, which is one of the high speed forming methods, has been used for the forming process in various industry fields. Numerical approach by finite element simulation of the EMF process is presented in this study. The implicit code is used to obtain the numerical model of the time-varying currents that are discharged through the coil in order to obtain the transient magnetic forces. In addition, the body forces generated in the workpiece are used as the loading condition to analyze deformation of thin sheet metal workpiece using explicit code. Numerical approach for a dimpled shape by EMF process is carried out and the simulated results of the dimpled shape by EMF are reviewed in view of the deformed shape and formability evaluation.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2021년도 봄 학술논문 발표대회
• /
• pp.4-5
• /
• 2021

In this study, in the coating-sheet composite waterproofing method, a specimen was formed to prevent the transmission of the no-node tensile stress occurring under the junction between sheets by forming an insulating structure when the junction was formed, and to compare the effect of preventing breakage with the existing common junction. For this, tensile performance evaluation was conducted. As a result of the evaluation, it was confirmed that it exhibited higher tensile strength compared to the existing joint and at the same time exhibited a large width of displacement characteristics, and thus, had an effect of preventing breakage.

• 한국가스학회지
• /
• 제4권2호
• /
• pp.52-57
• /
• 2000

본 연구에서는 자료를 통한 국내 가스산업시설의 인적오류에 관한 산업재해를 분석하고 국외에서 발전된 정량화 방법을 이용하여 인적 오류 가능성을 예측할 수 있도록, 먼저 PIF(Performance Influencing Factor)분류구조를 바탕으로 보다 객관적이고 정확한 자료를 얻기 위해 평가 Sheet를 제시하였다. 그리고 평가 Sheet를 이용하여 가스산업시설의 인적 오류변수들을 평가하고, 평가 자료를 가지고 정량화 기법을 이용하여 HEP(Human Error Probability)를 산출하게 된다. 마지막으로, 보다 현장 작업자들이 편하고 쉽게 적용시킬 수 있도록 프로그램화를 시켰다. 본 연구의 결과로써 신뢰성 있는 인적오류 D/B를 구축함으로써 이를 공유할 수 있으며, 그리고 인간의 능률을 현저히 향상시킴과 동시에 인적오류감소 전략을 수립하는데 많은 도움이 될 것이다.

• 한국광학회지
• /
• 제34권5호
• /
• pp.185-191
• /
• 2023

유연 스텔스 소재의 실용성 향상을 위해 보호층을 입힌 뒤의 경도, 유연성, 보호층과 스텔스 소재의 접착력을 평가하였다. 우선 ISO 15184 연필 시험법을 통해 경도를 측정하였으며, 보호층을 입히기 전과 비교하여 경도가 HB에서 3H로 3등급 올라가는 것을 확인할 수 있었다. 유연성은 ASTM D522 시험법에 따라 소재를 특정 직경의 원기둥에 대고 구부린 뒤 균열 생성 여부를 확인하며 평가하였고, 그 결과 균열이 생성되지 않는 최소 직경이 0.125인치임을 확인하였다. 접착력은 ASTM D3359 시험법에 따라 접착 띠를 보호층에 붙였다 떼어내면서 보호층이 박리되는 비율로 평가하였다. 이를 통해 보호층을 입혔을 시 군용 접착력 한계 조건인 4B보다 높은 결과(5B)를 얻었다.

• 한국정밀공학회지
• /
• 제19권2호
• /
• pp.160-170
• /
• 2002

Retroreflective article is different from other reflecting objects as it returns the incidence ray to the near of its source. This characteristic makes the retroreflectors have many applications in reflective highway signs, reflective vests, and other safety-relaxed items. These articles may have various shapes. However, the quantitative evaluation of performance for the best shape of retroreflector needs much time and cost for manufacturing prototypes and for performance experiments. In this work, we have developed a program for simulating the trace of ray entered into a retroreflective element, in order to determine the optimal shape of retro-reflection. We have also proposed new performance criterion of retroreflective articles, which can confide the range of incidence angle, instead of the criterion with the merely retroreflective strength.