• 제목/요약/키워드: artificial aging treatment

검색결과 49건 처리시간 0.024초

TIG 용접된 Al6013-T4 알루미늄 합금에서 피로균열전파저항의 변동성에서의 PWHT의 영향 (Effect of PWHT on Variability of fatigue Crack Propagation Resitance in TIG Welded Al 6013-T4 Aluminum Alloy)

  • 구나완;이상열;김선진
    • 동력기계공학회지
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    • 제15권6호
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    • pp.73-80
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    • 2011
  • The experimental investigation focuses on an influence of artificial aging time in longitudinal butt welded Al 6013-T4 aluminum alloy on the fatigue crack growth resistance. The preferred welding processes for this alloy are frequently tungsten inert gas welding (TIG) process due to its comparatively easier applicability and better weldability than other gas metal arc welding. Fatigue crack growth tests were carried out on compact tension specimens (CT) in longitudinal butt TIG welded after T82 heat treatment was varied in three artificial aging times of 6 hours, 18 hours and 24 hours. Of the three artificial aging times, 24 hours of artificial aging time are offering better resistance against the growing fatigue cracks. The superior fatigue crack growth resistance preferred spatial variation of materials within each specimen in the Paris equation based on reliability theory and fatigue crack growth rate by crack length are found to be the reasons for superior fatigue resistance of 24 hours of artificial aging time was compared to other joints. The highest of crack propagation resistance occurs in artificial aging times of 24 hours due to the increase in grain size (fine grained microstructures).

하이브리드 센터필러 제조 시 열처리 이력이 7075 알루미늄 합금 판재의 인장강도에 미치는 영향 (Effect of Heat Treatment History in Fabrication of Hybrid Center Pillar on Tensile Strength of 7075 Aluminum Alloy Sheet)

  • 유동훈;김지훈;박상언;장홍규;김대용
    • 소성∙가공
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    • 제30권2호
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    • pp.61-68
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    • 2021
  • As part of efforts to reduce the weight of automotive body-in-white, a hybrid center pillar with high strength 7075 aluminum alloy (AA7075) sheet and carbon fiber reinforced plastic (CFRP) has been recently studied. In the fabrication of the AA7075-CFRP hybrid center pillar, the AA7075 sheet might go through heating-forming-in-die quenching (HFQ), artificial aging, hybridizing, and then paint baking processes. In this study, we investigate the effects of the heat treatment history associated with each process on the tensile strength of the AA7075 sheet. Typical heat treatment conditions are HFQ for 20 minutes at 480℃ and then cooling down with die, artificial aging of T6 temper for 24 hours at 120℃, hybridizing for 10 minutes at 150℃, and paint baking for 20 minutes at 180℃. The tensile strength of the AA7075 sheet is continuously increased by a series of heat treatments of hybridizing and paint baking and is expected to have yield stress above 500MPa without artificial aging of T6 temper.

극저온 열처리 공정이 6061 알루미늄 합금의 잔류응력과 인장특성에 미치는 영향 (Effects of Cryogenic Treatment on Residual Stress and Tensile Properties for 6061 Al Alloy)

  • 박기정;고대훈;김병민;임학진;이정민;조영래
    • 대한금속재료학회지
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    • 제49권1호
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    • pp.9-16
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    • 2011
  • To develop a 6061 aluminum alloy with low residual stress and high tensile strength, a cryogenic treatment process was investigated. Compared to the conventional heat treatment process for precipitation hardening with artificial aging, the cryogenic treatment process has two additional steps. The first step is cryogenic quenching of the sample into liquid nitrogen, the second step is up-hill quenching of the sample into boiling water. The residual stress for the sample was measured by the $sin^2{\psi}$ method with X-ray diffraction. The 6061 aluminum alloy sample showed 67% relief in stress at the cryogenic treatment process with artificial aging at $175^{\circ}C$. From this study, it was found that the optimum cryogenic treatment process for a sample with low residual stress and high tensile strength is relatively low cooling speed in the cryogenic quenching step and a very high heating speed in the up-hill quenching step.

Comparative evaluation of shear bond strength of orthodontic brackets bonded to three-dimensionally-printed and milled materials after surface treatment and artificial aging

  • Ameer Biadsee;Ofir Rosner;Carol Khalil;Vanina Atanasova;Joel Blushtein;Shifra Levartovsky
    • 대한치과교정학회지
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    • 제53권1호
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    • pp.45-53
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    • 2023
  • Objective: This study aimed to evaluate the shear bond strength (SBS) of orthodontic brackets bonded to three-dimensionally (3D)-printed materials after various surface treatments and artificial aging compared with that bonded to computer-aided design/computer-aided manufacturing (CAD-CAM) polymethyl methacrylate (PMMA)-milled materials. Methods: Eighty cylindrical specimens were 3D printed and divided into the following four subgroups (n = 20 each) according to the surface treatment and artificial aging procedure. Group A, sandblasted with 50 ㎛ aluminum oxide particles (SA) and aging; group B, sandblasted with 30 ㎛ silica-coated alumina particles (CO) and aging; group C, SA without aging; and group D, CO without aging. For the control group, 20 CAD-CAM PMMA-milled cylindrical specimens were sandblasted with SA and aged. The SBS was measured using a universal testing machine (0.25 mm/min), examined at ×2.5 magnification for failure mode classification, and statistically analyzed (p = 0.05). Results: The retention obtained with the 3D-printed materials (groups A-D) was higher than that obtained with the PMMA-milled materials (control group). However, no significant difference was found between the study and control groups, except for group C (SA without aging), which showed significantly higher retention than the control group (PMMA-SA and thermocycling) (p = 0.037). Study groups A-D predominantly exhibited a cohesive specimen mode, indicating specimen fracture. Conclusions: Orthodontic brackets bonded to 3D-printed materials exhibit acceptable bonding strengths. However, 3D-printed materials are prone to cohesive failure, which may result in crown fractures.

경년열화 열처리된 2.25CrMo 강에서의 탄화물 특성 및 자기적 성질의 변화 (Changes of Carbide Characteristics and Magnetic Properties in Artificially Aging Heat Treated 2.25CrMo Steel)

  • 변재원;권숙인
    • 열처리공학회지
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    • 제14권6호
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    • pp.323-329
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    • 2001
  • Artificial aging was performed to simulate the microstructural degradation in 2.25CrMo steel arising from long time exposure at $540^{\circ}C$. The carbide morphologies were classified as acicular, pipe and globular type, and the number of carbides per unit area was measured for each type of carbides. The fine acicular carbides were found to diminish drastically in the initial stage of aging. An attempt was made to evaluate the microstructural degradation in artificially aging heat treated 2.25CrMo steel by the magnetic property measurements such as saturation magnetization, coercivity and remanence. The saturation magnetization showed no distinct trend with aging time. However, the coercivity and remanence were observed to decrease rapidly in initial 920 hours of aging time and then decrease slowly afterwards.

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다이캐스팅 ADC12 합금의 열처리 전후의 기계적 특성변화 (Change of Mechanical Properties During Heat Treatment of Diecast ADC12 Alloy)

  • 강신욱;박경섭;오은호;심정일;김희수
    • 한국주조공학회지
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    • 제36권3호
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    • pp.88-94
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    • 2016
  • We investigated the effect of heat treatment on an ADC12 alloy produced using diecasting. The heat treatment used in this study was a typical T6 process: a solid solution treatment followed by an artificial aging treatment. As-cast specimens were solid-solution-treated at $500^{\circ}C$ and $530^{\circ}C$ for 1-16 hr, and aged at $160^{\circ}C$ and $180^{\circ}C$ for 1-8 hr. Microstructural changes in the alloy during the heat treatment were observed. Changes in mechanical properties of the alloy were measured using a micro-Vickers hardness tester. Finally, we determined the optimal heat treatment conditions for the diecast ADC12 alloy.

조선왕조실록 밀랍본 복원기술연구(제2보) - 실록의 복원용지 탐색을 위한 전통한지의 열화특성 평가 - (The Study of Restoration Technique of Wax-Treated Volume for the Annals of the Joseon Dynasty(II) - Evaluation of aging characteristics of Korean traditional paper, Hanji as the restoration material of the annals -)

  • 정선화;정소영;서진호
    • 펄프종이기술
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    • 제40권2호
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    • pp.43-56
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    • 2008
  • The purpose of the experiment was to evaluate the material stability of the paper of the annals of Joseon Dynasty for the conservation purpose and the categories were as listed below : 1. Procuring traditional Hanji and semi-Hanji from different regional hanji paper mill. 2. Artificial accelerated aging treatment to examination its stability (UV irradiation, dry heat) 3. Analysis of optical, physical characteristic. The suitable Hanji for categories would be used as a reconstruction material for the waxel paper in the papers of the annals of Joseon Dynasty.

인공 열화 열처리된 2.25CrMo 강의 미세조직 변화에 대한 초음파 비파괴평가 (Ultrasonic Nondestructive Evaluation of Microstructural Degradation in Artificially Aging Heat Treated 2.25CrMo Steel)

  • 변재원;권숙인;박은수;박익근
    • 열처리공학회지
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    • 제14권2호
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    • pp.110-117
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    • 2001
  • Artificial aging was performed to simulate the microstructural degradation in 2.25CrMo steel arising from long time exposure at $540^{\circ}C$. It was found that the carbides became coarser and spheroidized as aging time increased. An attempt was made to evaluate the microstructural degradation in artificially aging heat treated 2.25CrMo steel by the ultrasonic attenuation and velocity measurements. Ultrasonic velocity was found essentially insensitive to the microstructural changes resulting from aging heat treatment. However, the ultrasonic attenuation was observed to increase with increasing aging time. Also, it was noticed that the change of ultrasonic attenuation with aging time was more sensitive at high frequency regions.

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DA-3711:A POTENT TISSUE-ENGINEERED ACTIVE INGREDIENTS FOR ANTI-AGING

  • Kim, B. M.;Lee, M.;Lee, J. H.;I. S. Doo;M. K. Son;S. H. Kang;Kim, W. B.;J. W. Kwon
    • 대한화장품학회:학술대회논문집
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    • 대한화장품학회 2003년도 IFSCC Conference Proceeding Book I
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    • pp.659-659
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    • 2003
  • In this study, we have investigated the potent anti-aging effect of DA-3711, a cosmetic ingredient derived from artificial skin culture. The artificial skin was originally developed as a skin replacement for the treatment of chronic skin wounds. To produce DA-3711, neonatal human fibroblasts were seeded into biocompatible collagen/chitosan/glycosaminoglycan (GAG) scaffolds and cultured in Dulbecco's modified Eagle's medium (DMEM) supplemented with fetal bovine serum and nonessential amino acids. Analysis of the culture broth (DA-3711) showed that growth factors such as VEGF, TGF-$\beta$, KGF were present at significantly higher levels that in the culture broth of fibroblasts cultured in monolayer. The biological activity of DA-3711 was assessed by measuring in vitro cell proliferation and collagen synthesis of normal human fibroblasts. Fibroblasts treated with 10% DA-3711 showed a 2-fold higher proliferation and 2 to 4-fold higher collagen synthesis than untreated cells. DA-3711 also exhibited anti-oxidative effects, since cells under peroxide-induced oxidative stress showed a 30% higher viability in DA-3711-containing medium than in medium without DA-3711 addition. The results suggest that DA-3711 may have anti-aging effects by stimulating skin regeneration and protecting against oxidative stress.

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조선왕조실록 밀랍본 복원기술 연구(제3보) -습열열화처리를 이용한 복원용 한지의 내구성 평가- (The Study of Restoration Technique of Wax-Treated Volume for the Annals of the Joseon Dynasty (III) -Evaluation of Durability of Korean Traditional Paper using Moist-heat Aging Treatment-)

  • 정선화;정선영;서진호;정소영
    • 펄프종이기술
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    • 제45권5호
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    • pp.49-55
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    • 2013
  • To explore the paper materials for restoration of the Annals of the Joseon Dyansty, durability of the three type of the traditional Korean Papers were estimated in this study, through moist heat artificial aging test. Three types(D, F, and G) which showed the best preservation performance in dry heat and UV treatment in the previous study were selected and artificial accelerated aging treatment with moist-heat process was conducted; the viscosity change rate was D>G>F; folding endurance G>D>F; $L^*$ value F>D>G; $a^*$ and $b^*$ change rate D>G>F; brightness decrease rate D>G>F, suggesting paper F showed the least change rate in physical/optical properties. Also the CLSM image observation showed fair coherence among fibers and confirmed paper mulberry. And in FDI extraction from each sample, paper F showed the highest value. Overall, paper F (traditional glossy paper) showed the highest stability against thermal treatment. It confirms that paper F is suitable as restoration paper for tributary remains including the annals of the Joseon Dynasty for its steady strength/viscosity decrease rate and color change rate.