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- 저자 : Kasman (검색결과 3 건)
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Şefika Kasman,Sertan Ozan 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.2
In this study, AA7075-T651 aluminum alloy was joined by friction stir welding (FSW) method, using two different pin offset values, and the microstructure, macrostructure, mechanical properties of welded joints were examined. The tensile strength, elongation at rupture, and bending strength of welded joints were measured in the ranges of 236-408 MPa, 0.3-5.7 % and 110-574 MPa, respectively. Tensile test results revealed that the highest tensile strength of 408 MPa was obtained with the process parameters of 630 rpm tool rotational speed (TRS) and 0 mm pin offset. It is worth noting that joints, welded with a TRS of 800 rpm in the same manner, i.e., the pin was positioned at zero offset, exhibited the lowest tensile strength, with a value of 236 MPa. Microstructural and macrostructural observations revealed that welded joints exhibiting lower tensile strength and elongation at rupture consist of various types of defects (e.g. tunnel and cavity). Defect-free joints were fractured at a region between heat affected zone (HAZ) and base metal; however, welded joints with variety of defects were fractured through HAZ.
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Friction Stir Welding of Twin-Roll Cast EN AW 3003 Plates
Yucel Birol,Sefika Kasman 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.6
Twin-roll cast EN AW 3003 plates were butt-welded with friction stir welding and their structural features were identified. Sound welds were obtained in twin-roll cast EN AW 3003 plates at tool rotation speeds higher than 500 rpm. The ultimate tensile strength of the welded plates was 134 ± 3 MPa, comparable to the ultimate tensile strength of the original plate, at 146 MPa. The stirring action of the pin fractured the interdendritic network and coarse eutectic cells, replacing the dendritic features of the base plate with a uniform dispersion of very fine intermetallic particles across the stir zone. The thermal and mechanical cycles introduced during FSW relaxed the supersaturation of the cast plate, leading to the precipitation of intermetallic particles. This precipitation activity produced a particle population gradient that peaks inside the stir zone and dictates the etching response across the plate section. The material in direct contact with the rotating pin is severely deformed and is exposed to frictional heating and inevitably undergoes dynamic recrystallization. The very fine grain structure thus obtained suffers abnormal grain growth when annealed at high temperatures due to the effective pinning of the grain boundaries by the fine particles.
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Francesco Del Giudice,Alex M. Kasman,Matteo Ferro,Alessandro Sciarra,Ettore De Berardinis,Federico Belladelli,Andrea Salonia,Michael L. Eisenberg 대한비뇨의학회 2020 Investigative and Clinical Urology Vol.61 No.4
Purpose: Ongoing evidence has suggested the role of male factor infertility as a potential predictor of mortality and general health status. The aim of the present review is to update the current knowledge base regarding the association between male factor infertility and general health through a critical review of the literature. Materials and Methods: A systematic review of the literature was carried out from inception to November 2019 in order to evaluate significant associations between male infertility and adverse health outcomes such as cardiovascular, oncologic, metabolic and autoimmune diseases as well as overall mortality. Results: In all, 27 studies met inclusion criteria and were critically examined. Five studies examined male infertility and cardiovascular disease risk, 11 examined oncologic risk (e.g., overall cancer risk, testis and prostate cancer), 8 examined aggregate chronic medical diseases and 5 infertility related to incidence of mortality, for a total of 599,807 men diagnosed with any male factor infertility covering a period from 1916 to 2016. Conclusions: A man's fertility and overall health appear to be interconnected. Therefore, a diagnosis of male infertility may allow a window into future comorbidity and/or mortality which may help guide clinical decisions and counseling. Several possible etiologies such as genetic, epigenetic, developmental, and lifestyle-based factors need to be further evaluated in order to establish the underlying mechanisms between male infertility and health.
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