• 제목/요약/키워드: Hot bending

검색결과 183건 처리시간 0.026초

A Study on Evaluation of Plastic Strain at Notch Tip of Weld HAZ in Steel (강 용접 열영향부 놋치 선단 의 소성 스트레인 평가에 관한 연구)

  • 김태영;임재규;정세희
    • Journal of Welding and Joining
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    • 제2권1호
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    • pp.41-48
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    • 1984
  • Recrystallization technique was applied to analyze plastic strain at the notch tip of coarse grain HAZ in mild steel (SB 41) and high strength steel (SA 588). The notch tip of specimen was deformed by three point bending. Accumulated displacement (Crack Opening Displacement ${delta}t$) by the monotonic and cyclic loading under room temperature and hot strain embrittlement temperature ($250^{\circ}C$) was 0~1.0mm. Recrystallization heat treatment conditions were $650^{circ}C{ imes}3hr$ for SB 41 and $700^{circ}C{ imes}3hr$ for SA 588. The experimental results obtained were as follows ; 1) Distribution of the effective plastic strain at plastic zone was appeared by the function of crack opening displacement, and plastic zone or the effective plastic strain increased with crack opening displacement. 2) Plastic strain at notch tip of HAZ due to accumulated hot strain calculated as follows. .epsilon. over bar $_{p}$ = .epsilon. over bar $_{cr}$ (x/ $R_{x}$ ) $^{m}$ (m=0.25) 3) Work hardending ratio of notch tip for hot strain was linearly increased with .epsilon. over bar $_{max}$ and dependent upon the material types.s.

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A Camber Monitoring System of RM Zone based on Direction Selective Edge Detection Algorithm (방향 선택형 에지검출 알고리즘 기반의 RM존 캠버 모니터링 시스템)

  • Kim, Hyun-Soo;Choi, Yong Joon
    • Journal of Institute of Control, Robotics and Systems
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    • 제21권8호
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    • pp.713-717
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    • 2015
  • In this paper, we propose camber monitoring system which is using on hot rolling process. In roughing mill which is one of the rolling part in hot rolling process, steel plate can be bended in width direction under the imbalance of rolling condition. This bending of steel plate in width direction is called as camber. In order to measure the camber, first, cameras which are installed over transport pathway of steel plate take pictures of whole shape of steel plate. And location value of steel plate edge is extrated from these pictures by edge detection algorithm. But, there are a lot of noises which are generated by such as water sprays, dusts, peripheral equipments in these pictures, and these noises make edge detection difficult. In order to solve this kind of problem, we developed a direction selective edge detection algorithm, and applicated in our camber monitoring system. As a result, we got stable results in spite of process noises.

Influence of Testing Method on the Fracture Toughness of Cordierite-SiC Whisker Ceramic Composites (코디어라이트-SiC위스커 복합재료에서 측정방법에 따른 파괴인성치의 변화)

  • ;Weisskopf
    • Journal of the Korean Ceramic Society
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    • 제24권4호
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    • pp.313-320
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    • 1987
  • Fracture toughness of hot pressed cordierite-SiC whisker ceramic composites contained up to 40vol.% SiC whiskers were determined by using the indentation crack length(IC), indentation strengthin-bending(IS), and single-edge notched-beam(SENB) methods. The results were compared to stress intensity factor, KB, at the crack branching boundary measured by using the mirror zone radius (MZ) method. IS method seems to provide a more reasonable estimation of fracture toughness than other methods for these composites.

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Construction of Vehicle Door Impact Beam Using Hot Stamping Technology (핫스탬핑에 의한 자동차 도어 임팩트빔의 개발)

  • Lee, Hyun-Woo;Hwang, Jung-Bok;Kim, Sun-Ung;Kim, Won-Hyuck;Yoo, Seung-Jo;Lim, Hyun-Woo;Yum, Young-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • 제34권6호
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    • pp.797-803
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    • 2010
  • A vehicle door impact beam made of a thin sheet of steel has been constructed using hot stamping technology with the aim of ensuring occupant safety in the event of a side collision. This technology has been used to increase the strength of the vehicle body parts and to reduce the weight of the door impact beam as well as the number of work processes. Mechanical tests were performed to determine the material properties of the hot-stamped specimen and the results of the tests were used as input data in stamping and structural simulation in order to obtain the optimal design of door impact beam. The strength of the hot-stamped door impact beam increased to a value that was 102% higher than that of conventional pipe-shaped door impact beam. A weight reduction of 34% was also achieved.

Characterization of Aluminum Coated Layer in Hot Press Forming of Boron Steel (고온 프레스성형시 보론강 알루미늄 코팅층 거동특성)

  • Jang, Jeong-Hwan;Joo, Byeong-Don;Lee, Jae-Ho;Moo, Young-Hoon
    • Journal of the Korean Society for Heat Treatment
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    • 제21권4호
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    • pp.183-188
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    • 2008
  • Hot press forming allows geometrically complicated parts to be formed from sheet and the rapid cooling hardens them to extremely high strength. The main purpose of this research is to characterize Al coated layer in Al coated boron steel during hot press forming. For the hot press hardening experiment, test specimens were heated up to $810{\sim}930^{\circ}C$ and held for 3, 6 and 9 minutes, respectively. And then, some specimens were press hardened and others were air-cooled without any pressing for the comparison purpose. Al coated layer shows four distinct micro-structural regions of interest; diffusion zone, Al-Fe zone(I) low-Al zone(LAZ) and Al-Fe zone(II). Band-like LAZ is clearly shown at temperature ranges of $810{\sim}870^{\circ}C$ and sparsely dispersed at temperature higher than 900oC. The micro-cracking behavior in the Al coated layer during forming were also analyzed by bending and deep drawing tests. The strain concentration in softer LAZ is found to be closely related with micro-cracking and exfoliation in coated layer during forming.

Effect of Post-processing on Mechanical Properties of 3D Printed Carbon Chopped Fiber Reinforced Composites (3D 프린팅 된 탄소 단섬유강화 복합재료의 후처리 효과가 재료의 기계적 성능에 미치는 영향)

  • Jia-le, Che;Seung-Hwan, Chang
    • Composites Research
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    • 제35권6호
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    • pp.463-468
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    • 2022
  • The high porosity of the infill pattern of carbon chopped fiber-reinforced Nylon composite structures fabricated by the fused filament fabrication (FFF) type 3D printers determines the mechanical performance of the printed structures. This study experimentally evaluated the mechanical performance of Onyx composite specimens fabricated with a rectangular infill structure under the hot-pressing condition to improve the mechanical properties by reducing the porosity of the infill pattern of the printed structure, and evaluated the best mechanical performance. The hot-pressing conditions (145℃, 4 MPa, 12 min) that induce the most appropriate mechanical properties were found. As a result of microscopic observation, it was confirmed that the infill porosity of the composite specimens subjected to post hot-pressing treatment was effectively reduced. In order to confirm the mechanical performance of the post-treated specimen, a tensile test and a three-point bending test were performed with a control specimen without post-treatment and a specimen printed with the same density and dimensions after post-treatment to evaluate the mechanical properties. As a result of comparison, it was confirmed that the mechanical properties were effectively improved when the post-treatment of hot-pressing was performed.

Development of Large Diameter Hardfacing FCW for Life Extension of Hot Forging Die (열간단조 금형 수명연장을 위한 경화육성용접용 태경 FCW의 개발)

  • Kim, Sung-Ho;Jung, Yun-Ho;Baek, Seung-Hui;Jang, Jong-Hun;Park, Chul-Gyu;Woo, Hee-Chul;Jung, Byung-Ho;Cho, Sang-Myung
    • Proceedings of the KWS Conference
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    • 대한용접접합학회 2009년 추계학술발표대회
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    • pp.13-13
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    • 2009
  • 현재 열간단조 금형을 제작함에 있어 육성용접을 실시하는 방법이 금형강 STD61, STD11 등으로 제작하는 방법에 비해 보수나 비용적인 측면에서 이점을 가지고 있기 때문에 점차적으로 증가하고 있는 추세이다. 열간단조 공정에서 금형은 $1000^{\circ}C$이상의 고온재료와 반복접촉하게 된다. 이때 이형제의 사용은 급속냉각 및 급속가열의 열피로를 가속시킨다. 또한, 금형은 반복충격에 의한 기계적 피로를 받게 된다. 이러한 금형의 사용환경을 고려한 FCW는 종래 고가의 $2.8{\sim}3.2{\Phi}$인 외국산 FCW를 사용하였으나 이를 대체한 $3.2{\Phi}$ 태경 FCW가 국내에서 개발되었다. 하지만 개발된 FCW를 사용하여 제작된 금형의 수명이 부족한 현상이 발생하였다. 이에 금형의 수명을 연장시킬 수 있는 내균열성 및 내열충격성을 확보한 태경 FCW의 개발과 개발된 FCW의 성능평가가 요구되었다. 특히 열간단조 금형에 있어서 중요한 내열충격성의 경우 가열과 냉각의 반복 Cycle에 의한 Thermal shock의 평가가 대부분이며 높은 Cycle로 인해 많은 시간이 걸리며, 또한 가열과 냉각을 오갈 수 있는 고가의 시험장치가 요구된다. 그러므로 개발된 FCW 육성용접부의 내균열성 및 내열충격성을 평가할 수 있는 방법에 대한 연구와 특히 내열충격성을 시간이 적게 걸리면서도 경제적으로 평가할 수 있는 방법에 대한 연구가 필요하다. 본 연구의 목적은 열간단조 금형 육성용접부의 내균열성 및 열충격특성을 평가할 수 있는 방법에 대한 검토와 특히 내열충격성에 대해 J.W.Kim등의 시험방법을 참고하여 시간이 적게 걸리면서 저 비용으로 열 충격특성을 평가할 수 있는 시험법을 고안하는 것이다. 이를 위한 방법으로 육성용접부의 내균열성을 평가하기 위한 상온 Bending을 실시하였고, 내열충격성을 평가하기 위한 염욕로를 이용하는 고온 Bending을 고안하여 실시하였다. 상온 Bending, 고온 Bending 모두 3점 굽힘시험을 적용하였다. 고온 Bending의 가열방법으로는 염욕로를 사용하여 시편이 대기중에서 약 $850^{\circ}C$의 온도가 될 수 있도록 하였다. 시편은 각각 열처리를 하여 요구 경도를 확보하였고, 이를 염욕로에서 5분간 가열 및 유지하여 취출 후 굽힘하중을 가하여 변위의 정도로 열충격을 평가하는 방법을 사용하였다. 상온 Bending은 극한변형량과 파단부 극한응력으로, 고온 Bending은 고온 극한변형량으로 평가를 하였고, 외국산 FCW를 사용한 육성용접부를 비교대상으로 하였다. 평가 결과 개발된 국산 $3.2{\Phi}$ 태경 FCW의 성능은 외국산 FCW와 유사하거나 우수한 것으로 평가되었고, 실제 금형을 제작하여 현장에 적용한 결과 금형의 수명이 연장된 것이 나타났다.

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Evaluation of Formability and Mechanical Characteristic for Hot Forming Quenching in Sheet Forming of Al6061 Alloy (Al6061 판재성형에서 핫 포밍 ��칭의 성형성 및 기계적 특성 평가)

  • Ko, Dae Hoon;Kim, Jae Hong;Lee, Chan Joo;Ko, Dae Cheol;Kim, Byung Min
    • Transactions of the Korean Society of Mechanical Engineers A
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    • 제37권4호
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    • pp.483-490
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    • 2013
  • In aluminum sheet metal forming, the conventional forming methods of T4 or T6 heat-treated sheets result in low formability and dimensional accuracy. This study suggests a new forming method for aluminum sheets called as hot forming quenching (HFQ) that solves the problems faced in the conventional method. HFQ combines the heat treatment and forming processes through the forming die during the quenching of a solid solution. To evaluate the application of HFQ to the sheet forming of aluminum, an Erichsen and V-bending test are performed in this study to measure the dimensional accuracy and formability, which are then compared with those of the conventional forming method. Furthermore, the strength and hardness of the products formed by HFQ are measured to confirm the degradation in mechanical properties compared with the conventional forming method, which shows the validity of the application of HFQ to aluminum sheet metal forming.

Strength Properties and Elastic Waves Characteristics of Silicon Carbide with Damage-Healing Ability (손상치유 능력을 가지는 탄화규소의 강도 특성과 탄성파 특성)

  • KIM MI-KYUNG;AHN BYUNG-GUN;KIM JIN-WOOK;PARK IN-DUCK;AHN SEOK-HWAN;NAM KI-Woo
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 한국해양공학회 2004년도 학술대회지
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    • pp.337-341
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    • 2004
  • Engineering ceramics have superior heat resistance, corrosion resistance, and wear resistance. Consequently, these art significant candidates for hot-section structural components of heat engine and the inner containment of nuclear fusion reactor. Besides, some of them have the ability to heal cracks and great benefit can be anticipated with great benefit the structural engineering field. Especially, law fracture toughness of ceramics supplement with self-healing ability. In the present study, we have been noticed some practically important points for the healing behavior of silicon nitride, alumina, mullite with SiC particle and whisker. The presence of silicon carbide (SiC) in ceramic compound is very important for crack-healing behavior. However, self-healing of SiC has not been investigated well in detail yet. In this study, commercial SiC was selected as sample, which can be anticipated in the excellent crack healing ability. The specimens were produced three-point bending specimen with a critical semi-circular crack of which size that is about $50-700{\mu}m$. Three-point bending test and static fatigue test were performed cracked and healed SiC specimens. A monotonic bending load was applied to cracked specimens by three-point loading at different temperature. The purpose of this paper is to report Strength Properties and Elastic Waves Characteristics of Silicon Carbide with Crack Healing Ability.

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Power Generation Properties and Bending Characteristics of a Flexible Thermoelectric Module Fabricated using PDMS Filling Method (PDMS 충진법을 이용하여 형성한 유연열전모듈의 발전특성과 굽힘특성)

  • Han, Kee Sun;Oh, Tae Sung
    • Journal of the Microelectronics and Packaging Society
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    • 제26권4호
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    • pp.119-126
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    • 2019
  • A flexible thermoelectric module, which consisted of 18 pairs of Bi2Te3-based hot-pressed p-n thermoelectric legs, were processed by filling the module inside with polydimethylsiloxane (PDMS) and removing the top and bottom substrates. Its power generation properties and bending characteristics were measured. With putting the flexible module on the wrist, an open circuit voltage of 2.23 mV and a maximum output power of 1.69 ㎼ were generated during staying still. On the other hand, an open circuit voltage of 3.32 mV and a maximum output power of 3.41 ㎼ were obtained with walking motion. The resistance variation of the module was kept below 1% even after applying 30,000 bending cycles with a bending curvature radius of 25 mm.